CA2025635A1

CA2025635A1 - Independent front air suspension apparatus and method

Info

Publication number: CA2025635A1
Application number: CA 2025635
Authority: CA
Inventors: Jonathan Young
Original assignee: Individual
Current assignee: Paccar Inc
Priority date: 1989-09-19
Filing date: 1990-09-18
Publication date: 1991-03-20
Also published as: AU638055B2; GB9020457D0; GB2236287B; AU6263290A; GB2236287A

Abstract

ABSTRACT

A method and system for effecting pneumatically cushioned independent front steer axle suspension for a Class 8 (33,001 lb + GVW) highway truck. An air spring rocker is provided to improve the fit arrangement of the front suspension components. By its pivoting action, the air spring rocker serves to take the vertically-directed suspension load and redirect this load to compress a suspension air spring in a horizontal direction, against a chassis frame rail side member. The left hand side road wheel is enabled to articulate independently of the articulation movement of the right hand side road wheel, and vice versa.

Description

INDEPENDENT FRONT AIR SUSPENSION APPARATUS AND METHOD

BACKGROUND OF THE INVENTION
1. Field of the Invention. The present invention relates generally to steering axle suspension for a heavy truck. More specifically, the present invention relates to an independent front air suspension for the steering axle of a heavy truck.

2. Prior Art. Independent front axles are universally applied in passenyer cars and light trucks. In most cases such vehicles use coil springs (typically in a vertical position) or leaf springs. Independent front axles ~or "suspensions"~ allow each of the front steering wheels ~left and righk) to absorb sh~cks independent of one another.
Although their use is pervasive in automobiles, th2y have not been used in heavy trucks.

There are two primary reasons for the absence of independent fxont suspen~ions in trucks. The first is that trucks are design to haul freight and not as pleasure vehicles. Cars, on the other hand, are designed for comfortable transportation. Ind~pendent front suspensions signif7cantly ~urther this end because with an independent front suspen~ion road bumps and other disturb~nces of a smooth ride aff~cting one wheel are reacted in that wheel suspension ~ssembly without affecting the other wheel. In a typical non independent ~ront ~uspension of prior art trucks, an iDI~pact or articul~tion af:Eecting on~ wheel also PACfAi 50141~SCS~SJA -1-affects the other wheel (because they are connected togeth~r throu~h an axle beam) causing a more turbulent di~turbance of the overall vehicle ride characteristics. The second reason is ~hat trucks must have more sturdy suspension components to support the yreat weight they carry. These large components take up most of the available space, so much so that prior ar~ independent front suspe~sions do not fit.

Prior art attempts to create an independent front suspension in a heavier vehicle include those at~empts to provide the same in transit c~aches (busses~. A common prior art approach in this context i~ to install air springs for each wheel in a vertical position such that the air spring centerline is compressed in a vertical plane during suspension articulation. The prior art is characterized by this approach of suspension air spring ~ounting.

While transit coaches have front axle capacity similar to that of a Class 8 highway tractor (deflned as having 33,001 lb. qross vehicle weight and up), their chassis arrangement is very different. Transit coaches typically have rear engine installations, narrow center beam frames and horizontal mounting of the steering gea~. In such an arrangement there i~ room to mount the air spring vertical-ly. The is not the case, however, in heavy trucks.

SUMMARY OF THE INYENTION
Accordingly, it is the object of the present invention to provide an independent front air suspension for a truck.

It is another object of the ~resent invention to provide an independent front air suspension having an air spring rocker.

It is still another object of the present invention ko provid~ an independent ~ront suspension for a truck without using a vertically oriented air ~pring~

PAC/~-50141/SCS/SJA -2-Furtherm~re, it is an object of the present invention to enable independent front axle air suspension to be u~ed on a vehicle ~in the described embodiment, a Class 8 highway tractor) by means of an air spring rocker. The air spring rocker pivots on a rocker pin to deliver an air spring force into an upper support arm which is structurally eonnected to receive ground load reaction force from a tire/wheel/hub/spindle assembly. The air spring is com-pressed directly against a frame rail side member.

The air spring rocker is use to redirect the vertical-ly-directed suspension ground reaction load into a horizon-tally directed compressive force against the air spring.
The air spring rocker thus permits the air spring to be mounted horizontally, compr ssing against the web of the frame rail side member (as opposed to vertically, as in prior art devices).

The attainment of the foregoing and related obj~cts, advantages and features of the invention should be more readily apparent to those skilled in the art, after review of the following more detailed description of the invention, taken together with the drawings, in which RIEF DESCRIPTION QF THE DRAWINGS
The accompanying drawings, which are insorporated in and f~rm a part of this specification, illustrate embodi-ments of the in~ention and, together with the description, serve to explain the principles of the invention:

Figure 1 is a rear view of ~he independent ~ront air suspension of the preferred e~bodiment.

Figure 2 is a left hand side YieW of the independent front ~ir suspension of the preferred embodiment.

Figur~ 3 is a top view o~ the independent front air suspension of the preferred embodiment.

Figure 4 is a rear view of the independent front air suspension of the preferred embodiment illustrating the transfer of vertical force to horizontal force by the rocker.

DETAILED _ESÇRIPTION OF THE PREFERRED EMBODIMENI'S
Reference will now be made in detail to the preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. While the invention will be described in conjunction with the preferred embodiments, it will be understood that they are not intended to limit the invention to those embodiments.
On the contrary, the invention is intended to cover alternatives, modifications and equivalents, which may be included within the spirit and scope of the invention as defined by the appended claims.

Referring to Figure 1, a rear view of the independent front air suspension of the preferred embodiment is shown.
The independent front air suspension of the preferred embodiment is comprised primariiy of five parts. Those parts are a upper and lower support arm 12 and 14, a rocker 16~ an air compression spring 18 and a frame rail 20. In essence, as the wheel 22 undergoes substantially vertical mov~ment (or general articulation) as it traver~es along a roadway, and even as it stands still, vertical force is transferred from the wheel to the upper support arm 1~.
This vertical force is then transferred to the rocker means which transfers the vertical force to a horizontal force~
The horizontal forci~ is then trans~erred to the air compression spring lR and resisted by the frame rail 20.
The use of the air spring rocker ~6 permits independent front suspension in trucks because it's use requires less space.

Figure 1 shows the left rear side of the independent ~xont air suspension as~embly 10. The right side (not shown) is a mirror image of the left side. A suspension frame 24 is providiPd. Th~ suspension frame 24 is connected to the frame rails (only one of which is shown) and forms sort of a "U" or "V" shape, the "U" or "V" shape circling under the engine 21 of the truck, as partially seen in Figure 4. The lower support arm~ 14 is connected betw~en the wheel (hub/wheel/tire assembly) 22 and the suspension frame 24. The upper support arm 12 is connected to upper ball joint 26 which is in turn connected to the wheel 22.
The other side of the uppex support arm 12 is connected to the upper arm bracket on the frame at pivot joint 28. The pivot joint 28 is used so that the upper support arm 12 can move up and down at its left end as the wheel 22 moves up and down.

The lower support arm 14 is similarly located and provid~s a similar function to that of the upper support arm 12. The lower support arm 14 is connected to ball joint 32. Both the ball joint 26 of the upper support arm 12 and the ball joint 34 of the lower support arm 14 are well known in the art. The other end of the lower support arm 14 is connected to the suspension frame 24 by pivot joint 32.
Pivot joint 32 performs the same function as pivot joint 28. That is, permitting the left end of the lower support arm 14 to move up and down as the wheel 22 moves up and down. The substantially ver~ical forces on the wheel 22 are transferred ~o the upper support arm 12.

Located above the upper support arm 12 is the rocker 16. The rocker 16 is pivotally mounted to the suspension frame at pivot 36. The rocker 16 is designed to have a horiæontal portion 16a which engages the upper support arm 12. The upper support arm 12 engages, but is not ~ixedly 3~ conne~ted to the rocker 16 so that when vertical forces are exerted on the upper ~upport arm (by the wheel) those forces are tran~ferred directly to the rocker 16. Note that in addition to absorbing upward v~rtical force (at the wheel 22) khe air spring 18 also extend~ outward when the wheel 22 moves vertically downward. In other words, the air spring 18 exerts a force on the rocker 16 throughout the entire anticipated vertical movement of the wheel 22.

Therefore, the rocker 16 need not be fixedly connected to th~ upper arm 12. The rocker 15 i5 pivotally connected to the suspension frame 24. This configuration permits the rocker 16 to be directly responsive to movement in the upper æ~pport arm 12, in either the up or down direction.

The upper support arm 12 and the lower support arm 14 are actually "A"-shaped with an extra rung. This is better illustrated in the t~p view of Figure 3. The rungs are not visible in Figure 1 becaus~ they run horiæontal and are obscured by the legs of the ~upport arms 12 and 14. One rung 12a (in the upper support arm 12 in Figure 1) is represented dotted line. The horizontal portion 16a of the rocker 16 rests on this rung 12a. Vertical forces are exerted through rung 12a to the rocker horizontal portion 16a and then to air spring 18.

The air spring 18 is located ~etwe~n the rocker 16 and the frame rail 20. A vertical portion 16b of the rocker 16 is maintained against the outside of the air spring 18.
The other sid~ of the air spring 18 is in contact with and pushes against the frame rail 20. As he rocker 16 is forced upward by forces on rung 12a, the rocker 16 pivot5 about pivot 36 and transfers force to the air spring 18.
The air spring 18 is compressed as the force is resisted by the frame rail 20 (note, air springs and their compres-sion under load are well known in the art).

Referring to Figure 2, a left side ~iew of the independent front air ~uspension ofthe preferred em~odiment is shown. The rocker 16 and the outside edge of the air ~pring 18 are shown in bold lines. A5 is evident ~rom Figure 2, a portion 16c of the rocker 16, curves t~ the right, or alternativ~ly stated, curves towar~ the r~ar of the truck. The horizontal portion 16a of the rocker 16, and particularly its relationship to rung 12a, is not readily discernable from this per pective, ~ut it can bs clearly seen th~t the rocker pivot ~6 is located below the PAC~A-50141/SCS/SJA -6-upper support arm 12. The rocker~ Ot~ 3~- iS mounted to a support rung 24a i~ the 6uspension frame 24.

Figure 2 illustrates that the upper support arm 12 (and lower 14) have two pivots each to accommodate their "A"-shape. The pivot joints 28 are for the upper support arm 12 and the pivot joints 32 are for the lower support arm 14. It is also apparent from Figure 2, that each of the support arms 12 and 14 are inclined toward the front of the vehicle at an angle of approximately 3 degrees. One reason for this is that since the vehicle usually moves in the forward direction, a slight forward tilt of the suspension provides "anti-dive" during the forward weight transfer associated with brake application.

The location of the frame rail 20 with respect to the other suspension components is also evident from Figure 2.
The rocker 16 compresses the air spring 18 squarely against frame rail 20, a short distance behind the vertical line which intersects the center of the wheel 22. A steering mechanism 40 is also shown in ~igure 2. The steering mechanism 40 forms no part of the present invention, but is included to show the positioning of various suspension and steerin~ components with respect to one another.

Referring to Figure 3, a top view of the independen~
front air suspe~sion of the pre~erred embodiment is shown.
From this p~rspective the "A"-shaped nature of the upper and lower support arms 12 and 14 can be seen. Focu~ing on the rocXer 16, the horiæontal portion of ~he rocker 16a is clearly visible on top ~ the fir~t rung 12a of the upper support axm 12. The second rung 12b of the upper ~upport arm can be seen tran~parently through the air spring 18.
The lower support arm 14 (joined to the suspension fram 24 at pivots 32) also has two rungs l~a and 14b. From this view it is evident that the vertical portion l~b 9f the rocker 16 i5 essenti~lly parallel to the frame rail 20 in the normal state. Consistent ther~with, when the air spring PAC/A-50141~SCS~SJA -7-(,J r ~ p~
1~ is compressed against the frame rail 20, the ~ompressi~n is relatively evenly distributed.

As stated previously, the rocker 16 is mounted at pivot 36 to rung 24a of the suspension frame 24. The two main portions of the suspension frame 24 appear vertically from the perspective of Figure 3, rung 24a running between the two. Also appearing in Figure 3 is a top view of the ball joint 26 which connects the upper support arm 12 to the wheel 22. Additionally, steering mechanism 40 is again lO included to illustrate positioning of various steering and suspension components with respect to one another.

Referring to Figure 4, the transfer of vertical to horizontal force is shown. The first arrow 50 indicates vertical force from the wheel 22, on the upper support arm 15 12 and the hori~ntal portion 16a of the rocker 16. The second arrow 52 indicates the transfer of that vertical force to horizontal force as the rocker 16 pivots in the direction of the transfer. The third arrow 54 represents the horizontal force being delivered through the air spring 20 18 into the frame rail 20.

The foregoing descriptions of specific embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the in~ention to the precise forms disclosed, and obviously many modifications and variations are possible in light of thP above teaching.
The embodiments werP chosen and dPscri~ed in order to best Qxplain the principl~s of the invention and its prac~ical application, to thereby enable others skilled in the art to be~t utilize the invention and various embodiments with various modifications as are suited t~ the particular use conte.mplated. It is intended that the scope of the invention be d~ined by the Claims appended hereto and thQir equivalents~

PAC/A-50141~$CS/SJA -8-

Claims

WHAT IS CLAIMED IS:
l. An independent steering axle suspension for a truck having a suspension frame and an adjacent frame rail and a wheel, comprising:
support means connected between said suspension frame and said wheel, said support means being connected to said wheel such that vertical forces on said wheel are substan-tially transferred to said support means;
rocker means pivotally connected to said suspension frame and positioned above said support means so that said vertical forces on said support means are substantially transferred into horizontal forces by said rocker means;
and compression means located between said rocker means and said frame rail so that said horizontal force is compressed against said frame rail, thereby absorbing said vertical forces on said wheel.
2. The suspension of claim 1 wherein said support means comprises an upper and a lower support means.
3. The suspension of claim l wherein said compression means is an air compression means.
4. The suspension of claim 1 wherein said truck is a class 8 highway tractor having a 12,000 lb front gross axle weight rating capacity.
5. An independent front suspension for a truck having a road wheel capable of articulation, comprising:
a substantially horizontally mounted compression means; and pivotally mounted rocker means connected between said road wheel and said horizontally mounted compression means for transferring substantially vertical forces from road wheel articulation to said horizontally mounted compression means.
6. The independent front suspension of claim 5 wherein said compression means is an air compression means.
7. An independent steering axle suspension for a truck having a suspension frame and an adjacent frame rail, comprising:
support means connected between said suspension frame and said wheel, said support means being connected to said wheel such that forces generated by the articulation of said wheel are substantially transferred to said support means;
pivotally mounted force redirection means positioned with said support means so that said articulation forces on said support means are substantially transferred into generally horizontal forces by said force redirection means; and compression means having a generally horizontal axis of compression located between said force redirection means and said frame rail so that said generally horizontal forces are delivered through said compression means against said frame rail, thereby absorbing said wheel articulation forces.
8. The independent steering axle suspension of claim 7 wherein said force redirection generally redirects force by 90 degrees.
9. The independent steering axle suspension of claim 7 wherein said wheel articulation forces are generally vertical in direction, said force redirection means transferring said generally vertical wheel articulation forces into generally horizontally directed forces.
10. The independent steering axle suspension of claim 7 wherein said compression means is an air compression means.
11. The independent steering axle suspension of claim 7 wherein said support means comprises an upper and lower support means, both connected between said suspension frame and said wheel,