Patent Application
20060103103
This invention relates generally to leaf spring suspension systems, and more particularly to leaf spring suspension systems having reduced weight and part count.
An automotive suspension system is designed to support a vehicle frame or body relative to a number of wheeled axles. The suspension system components work together to isolate the vehicle from the road so as to provide a soft, smooth ride for the vehicle occupants over an irregular road surface. The design of a suspension system seeks to balance the often conflicting goals of isolating the motion of the axle from the frame while providing desirable handling characteristics and minimizing manufacturing and operating costs.
A suspension system design often used in long-haul trucks includes a leaf spring, air spring, and shock absorber. Typically, each end of an axle is mounted near the center of a leaf spring which has a forward end mounted to the vehicle frame so that leaf spring may pivot in a vertical plane perpendicular to the road surface. An air spring connects the rear end of the leaf spring to the vehicle frame. A shock absorber is also coupled between the leaf spring or axle and the vehicle frame. Flexing of the leaf spring combined with the operation of the air spring and shock absorber isolate and dampen vertical motion of the wheels as they negotiate the roadway, thereby providing a smoother ride.
Although leaf spring, air spring, and shock absorber type suspension systems are successful, they tend to have a high number of component parts and are relatively heavy. The high number of parts contributes to high cost for manufacturing, assembly, inventory, and maintenance of the suspension system. A heavy suspension system reduces fuel economy and may also reduce useful load on roadways having axle weight limits. Thus, reducing suspension system weight is desirable.
However, a suspension system must also be strong and durable. For example, a typical heavy duty truck may be driven an average of 100,000 miles per year, or more, and may be driven well over a million miles in its useful lifetime. Thus, suspension system components may have design lifetimes of up to 1.5 million miles.
It would therefore be desirable to provide a leaf-air spring suspension system having fewer parts and a lower system weight without sacrificing system durability.
It would also be desirable to provide a low-weight suspension system suitable for use in long-haul trucks and other vehicles.
An object of the present invention is to provide a suspension system having fewer parts and lower weight than previously known suspension systems.
These and other objects of the invention are achieved by a leaf spring-air spring suspension system. A forward end of the leaf spring has a formed eye pivotally mounted to a lightweight bracket connected to the vehicle frame. The leaf spring is shaped so that the rearward portion of the leaf spring is positioned underneath the vehicle frame so that an air spring may be connected between the leaf spring and frame without using a cross beam.
The above objects and advantages of the present invention will be readily apparent upon consideration of the accompanying detailed description taken in conjunction with the accompanying drawings in which like characters refer to like parts throughout and in which:
The present invention relates to suspensions systems having a reduced part count and a reduced system weight. Although the suspension of
As shown in
Leaf spring 16 is subject to large static forces due to the weight of the vehicle and any load being carried. Leaf spring 16 is further subjected to large bending and tensile loads due to relative motions between vehicle frame 14 and axle 12 as the vehicle is driven. For instance, as a vehicle is driven over a roadway bumps and potholes in the road surface, the center of leaf spring 16 is deflected vertically relative to frame 14. This deflection results in a bending force being applied to leaf spring 16 and causes leaf spring 16 to flex along its length. Vehicle acceleration and breaking cause forces generally parallel to the vehicle frame to be applied to leaf spring 16, thereby subjecting leaf spring 16 to tensile and compressive loads. Accordingly, leaf spring 16 as well as the other component parts of suspension system 12 must be sufficiently strong and durable to withstand these forces over a significant length of time.
The high forces applied to leaf spring 16 may result in failure of the spring during use. Such failure may result in uncontrolled motion of axle 12 relative to frame 14. For example, a complete separation of leaf spring 16 between eye 20 and axle attachment area 24 may result in forward or rearward motion of one end of axle 12 relative to frame 14 so that axle 12 twists beneath the vehicle. Such a failure may result in a loss of control of a vehicle and has the potential to cause significant damage. To guard against such catastrophic failures, leaf spring 16 preferably comprises multiple layered components.
In one embodiment of leaf spring 16, leaf spring 16 comprises two spring leafs disposed one on the other as shown in
In a second embodiment of the invention, leaf spring 16 comprises a single spring leaf with a safety strap disposed along a portion thereof. For example, as shown in
The forward end of leaf spring 16 is pivotally coupled to frame 14 by means of bar pin assembly 22 which is mounted to a frame bracket. This is shown in more detail in
Frame bracket 30 has a transverse portion defining a surface substantially perpendicular to frame 14. Bolt holes are provided in the transverse surface of bracket 18 for accepting bolts for attaching of bar pin assembly 22. Bracket 30 is preferably configured so that when mounted to frame 14, bar pin assembly 22 is substantially orthogonal to a face of frame 16 and parallel to the road surface. Preferably bracket 30 is symmetrical so that a single bracket design may be used for mounting a suspension on either the right or left side of the vehicle.
Bar pin assembly 22 functions as a pivot point or axis about which leaf spring 16 rotates. Bus pin assembly 22 generally comprises bar 37 having a generally round central cross section designed to fit eye 20 in leaf spring 16. Bushing 38 is disposed on bar 37 to reduce wear between eye 20 and bar 37. Preferably, bushing 38 also includes a solid lubricant to reduce friction between eye 20 and bar 37. For example, Delrin may be suitable for use as bushing 38. The ends of bar 37 are flattened and have bolt holes formed therein corresponding to the bolt holes in frame bracket 30. Bolts 38 securely attach bar pin assembly 22 to frame bracket 30. Wear washers 38 are provided on bar pin assembly 22 to prevent wear between a eye 20 and frame bracket 30.
Advantageously, the arrangement of bracket 30 and bar pin 22 provides a convenient means for truing the alignment of axle 12 to frame 16 by the insertion or removal of shims 36 between bracket 30 and bar pin 22. For example, removing shims 36 from between bracket 18 and bar pin 22 on the right side of a vehicle and and/or inserting shims 36 between bracket 18 and bar pin 22 on the left side of the vehicle twists the axle in a clockwise direction relative to frame 14 when viewed from above. Conversely, inserting shims 36 between bracket 18 and bar pin 22 on the right side of a vehicle and and/or removing shims 36 from between bracket 18 and bar pin 22 on the left side of the vehicle twists the axle in a counterclockwise direction relative to frame 14 when viewed from above.
Axle 12 is mounted to central portion 24 of leaf spring 16 using, for example, u-bolts and suitably shaped brackets, saddles, and clamps. Referring now to
Preferably, saddle 41 also includes a integrate travel stop 46 that extends vertically above the uppermost extent of u-bolts 43. When the suspension system is compressed to an extreme degree, due to driving over a large bump at high speed for instance, travel stop 46 may come into contact with travel limit 47 disposed from frame 14 as shown in
Axle seat 42 fits between leaf spring 16 and axle 12 (see
Lower axle clamp 51 is disposed beneath axle 12 and accepts the legs of U-bolts 43 as shown in
In a preferred embodiment of the present invention, lower axle clamp 51 further includes a bracket for mounting a lower end of a shock absorber or other dampening device. Lower shock bracket 66 is disposed from a side or corner of lower axle clamp 51 and is adapted to accept an end of a shock absorber or similar device. In one embodiment of the invention, lower shock bracket 66 includes machined stud 67 which is press fit into a corresponding recess in lower shock bracket 66. Bracket 66 is configured so that stud 67 is disposed at an angle suitable for mating to a corresponding lower eye in shock absorber 59. Alternatively, lower shock bracket 58 may include a hole 68 or recess for accepting shock absorber 59 of the type having stud 57 in the end thereof as shown in
The rearmost end of leaf spring 16 is coupled to frame 14 by air spring 18. When the vehicle is loaded, air spring 18 compresses and leaf spring 16 pivots on bar pin assembly 22 allowing axle 12 to move vertically relative to frame 14. Leaf spring 16 may also flex somewhat. The air pressure in air spring 18 may be altered to adjust the position of leaf spring 16 relative to frame 14, and thereby adjust the ride height of the vehicle and maintain adequate travel clearance for axle 12. Preferably, the ride height adjustment is made automatically by a multi-way air valve suitably linked to the vehicle frame and axle. For example, as shown in
During normal driving, suspension system 10 compresses and extends within a normal operating range. When a vehicle is loaded, or encounters a large bump, suspension system 10 may be compressed beyond this normal operating range. When this happens, arm 74 and linkage 75 cause air valve 71 to operate to admit high pressure air to air-spring 18. This increases the downward force on the end of leaf spring 16 provided by air-spring 18, thereby opposing further compression of the suspension system. Conversely, when a vehicle is unloaded, suspension system 10 may become extended beyond its normal operating range. In this event, linkage 75 and arm 74 cause air valve 71 to vent high pressure air from air spring 18, thereby reducing the force on the end of leaf spring 16. Preferably, height control valve 71, arm 73, stud 75, and linkage 75 are configured so that when suspension system 10 is fully extended an angle between arm 74 and linkage 75 is less than about 150 degrees, and during full compression of suspension system 10, arm 74 and linkage 75 remain below the extended taper.
The present invention is not limited to the specific examples described and typical variations within the ordinary skill in the are also considered to be within the scope of the present invention. Although the present invention has been fully described by way of examples with reference to the accompanying drawings, it is to be noted that various changes and modifications will be apparent to those skilled in the art. Therefore, such changes and modifications should be construed as being within the scope of the invention.
