EP0060248A1

EP0060248A1 - Integral power steering axle

Info

Publication number: EP0060248A1
Application number: EP19810901181
Authority: EP
Inventors: Louis F. Versaci
Original assignee: Towmotor Corp
Current assignee: Caterpillar Industrial Inc
Priority date: 1980-09-18
Filing date: 1980-09-18
Publication date: 1982-09-22
Also published as: WO1982000983A1; JPS5769765U

Abstract

Des vehicules ont souvent eu un cylindre de direction separe boulonne sur un essieu de direction, des roues etant reliees a l'essieu de direction, et le cylindre de direction interconnecte entre l'essieu et les roues. Il etait difficile de positionner correctement un assemblage a piston du cylindre de direction avec les essieux de direction de l'art anterieur, et les assemblages a piston etaient soumis a une charge laterale pouvant provoquer leur defaillance prematuree. La presente invention concerne un essieu de servo direction integral (26, 26') qui elimine sensiblement ces problemes de charge laterale. Deux variantes d'un mode de realisation d'un essieu de servo direction integral (84, 84') comprennent un essieu de direction (26, 26') ayant un alesage (86, 86') et un assemblage a piston (90, 90') positionnes de maniere mobile dans l'alesage (86, 86').Vehicles have often had a separate steering cylinder bolted to a steering axle, wheels being connected to the steering axle, and the steering cylinder interconnected between the axle and the wheels. It was difficult to properly position a piston assembly of the steering cylinder with the steering axles of the prior art, and the piston assemblies were subjected to a lateral load which could cause their premature failure. The present invention relates to an integral servo steering axle (26, 26 ') which substantially eliminates these lateral load problems. Two variants of an embodiment of an integral servo steering axle (84, 84 ') include a steering axle (26, 26') having a bore (86, 86 ') and a piston assembly (90, 90 ') positioned in a movable manner in the bore (86, 86').

Description

Integral Power Steering Axle

Technical Field

This invention relates generally to steering axle assemblies for vehicles, and more particularly to an integral power steering axle for use in a lift truck or the like.

Background Art

It is well known to use a double-acting cylinder in the steering system of a vehicle to turn the wheels. Such steering cylinders are conventionally connected to a steering axle by fasteners, such as bolts. Steering knuckles are pivotally connected to the steer axle by kingpins and have spindles on which the wheels are rotatably mounted. The kingpins are seated in bores passing through laterally spaced ends of the steering axle and include steering arms projecting therefrom. The conventional steering cylinder has a piston assembly with a double-ended rod interconnected between the steering cylinder and the kingpins.

It has been difficult to precisely align the piston assemblies of the prior art steering cylinders with the kingpins, for example because the steering cylinder has been a separately fabricated component from the steering axle, and the steering cylinder bore is often not easily correctly positioned and held with respect to the kingpin bores. Additionally, forces caused by loading and/or operation of the vehicle have caused deflection of the steer axle assembly resulting in misalignment of the steering knuckles relative to the double-ended cylinder rod. This causes side loading of the rod and connection with the steering knuckle resulting in possible early failure of the cylinder, knuckle and related components. This misalignment also increases the friction between the connections, the cylinder piston and rod, and increases the amount of force required to remove the rod. Also deflection of the axle can cause bending of the rod and further increase in friction and possible damage to the rod and associated components.

The present invention is directed to overcoming one or more of the problems as set forth above.

Disclosure of Invention

In one aspect of the present invention, a combined steering axle and cylinder assembly is provided which comprises a bore extending through the steering axle. The steering cylinder assembly has a housing defined by the steering axle about the bore and a piston assembly movably positioned in the bore. In another aspect of the present invention a method for making an integral power steering axle comprises the steps of forming an elongated bore in a rigid beam and slidably mounting a piston assembly in the bore.

A steering cylinder assembly in accordance with the present invention is thus integrally formed with the steering axle itself. Kingpins and the like, for interconnecting the steering cylinder and wheels of a vehicle, may be assembled in very precise orientation with respect to the bore of the steering cylinder. Thus, misalignment between a piston assembly mounted within the bore and steering knuckles pivotally mounted on the kingpins, or the like, is substantially prevented. Continued precise alignment of the component parts of the steering system is ensured to provide the system with a trouble-free and long service life. The steering axle is a massive, rigid structure which resists deflection under loading and/or operation of the vehicle. Thus, side loading of the piston assembly is substantially prevented.

Brief Description of Drawings

In the drawings:

Figure 1 is a diagrammatic side elevational view of a lift truck incorporating an integral power steering axle embodiment of the present invention;

Figure 2 is an enlarged diagrammatic, partially sectioned plan top view of the integral power steering axle embodiment;

Figure 3 is a diagrammatic partially sectioned, front elevational view of the integral power steering axle embodiment;

Figure 4 is a diagrammatic isometric and exploded view of the embodiment as in Figures 2 and 3 with parts removed for clarification purposes; and, Figure 5 is a diagrammatic view similar to

Figure 4, but illustrating a modification thereof.

Best Mode For Carrying Out The Invention

Figure 1 illustrates a vehicle 10, herein illustrated as a lift truck, for lifting and carrying a load. Vehicle 10 has a horizontally disposed frame 14 with a frame rearward portion 18. Vehicle 10 includes a pair of front roadwheels 20 and a pair of rear roadwheels, or first and second wheels, 22.

Front roadwheels 20 may be mounted on a conventional drive axle (not shown) whereas rear roadwheels 22 are mounted on a steering axle 26. Axle 26 is connected to rear portion 18 of frame 14. Counterweight 19 is located adjacent rear roadwheels 22 of vehicle 10.

Referring to Figure 2, steering axle 26 preferably comprises a rigid beam 28 having first and second portions shown as generally longitudinally extending, opposed lateral portions 38. A medial portion 40 is located between lateral portions 38 and has ends 41. Thus, lateral portions 38 project beyond ends 41. Steering axle 26 is connected to rear portion 18 of frame 14 by any of various conventional means. For example, medial portion 40 has a forwardly projecting trunion 42 and a rearwardly projecting trunion 44. Each trunion 42, 44 is secured to a respective forward and rearward side 46, 48 of medial portion 40. Trunions 42, 44 are substantially aligned to define a longitudinal axis 50. Trunions 42, 44 are pivotally connected to the rear portion 18 of frame 14. Thus, steering axle 26 is permitted to oscillate about the horizontally disposed, longitudinal axis 50 of trunions 42, 44, and one rear roadwheel 22 may be raised as the other is lowered with respect to longitudinal axis 50.

Each lateral portion 38 of axle 26 is Identical to the other and together define a bilaterally symmetrical relationship. For convenience only one lateral portion 38 shall now be described unless otherwise noted. Turning to Figure 3, the lateral portion 38 is formed as a bifurcated structure 52 having spaced apart upper and lower arms 54, 56. Kingpins 60 are seated for pivotal movement in a pair of bearings 62. Each bearing 62 is fitted in a respective aperture or bore 64, 66. Aperture 64 is formed in the upper arm 54, whereas aperture 66 is formed in the lower arm 56. Apertures 64, 66 are aligned and together define an axis 68. Referring to Figure 2, a steering knuckle

70 is connected to the kingpins 60 and has a spindle 72 upon which rear roadwheel 22 is mounted. Steering knuckle 70 also has an outwardly projecting steering arm 74 which is pivotally fastened by pivot pin 76 to one end 80 of a tie link 82.

A double-acting, fluid steering cylinder assembly 83 functions to power pivotal movement of roadwheels 22 into and out of a plane passing through roadwheels 22 and perpendicular to spindle 72. A novel aspect of this invention resides in the structural integration of cylinder assembly 83 with steering axle 26. The integration of the cylinder assembly 83 and axle 26 shall be hereinafter referred to as an integral power steering axle 84 in accordance with the present invention.

Referring to Figure 4, medial portion 40 of axle 26 has a longitudinally extending, cylindrical bore 86. Bore 86 extends along an axis 89 and opens onto medial portion ends 41. Axis 89 lies in a plane passing midway through axis 68 between apertures

64, 66, and perpendicular to axis 68. The axis 89 is preferably offset from axis 68, i.e., axes 68 and 89 do not intersect one another. Referring to Figure 3, bore 86 is an integral part of steering cylinder 83 as steering axle 26 defines a housing 87 of steering cylinder assembly 83 at medial portion 40 about bore 86. The bore 86 has a longitudinally extending, cylindrical surface 88. A cylindrical sleeve, not herein illustrated, could be snugly inserted coaxially within bore 86. As used hereinafter, surface 88 shall include either the surface itself or the surface of a sleeve.

A piston rod assembly 90 of steering cylinder 83 is reciprocally mounted within bore 86 and includes a piston 92 and a double-ended piston rod 94. Piston 92 longitudinally reciprocates and slidably engages cylinder wall 88 of bore 86.

Steering cylinder 83 is connected to a source of pressurized hydraulic fluid in a conventional fashion such that application of hydraulic fluid to the steering cylinder 83 will cause the piston assembly 90 to move in one direction or the other depending upon the direction of flow of the pressurized fluid.

Figure 4 illustrates that housing 87 is structurally an integral portion of steering axle 26, and that bore 86 is precisely machined for proper orientation with respect to apertures 64, 66. As a consequence, when piston assembly 90 is assembled within bore 86, accurate alignment between the double-ended rod 94 of piston assembly 90 and steering knuckle 70 (not illustrated in Figure 4, but interconnected with apertures 64, 66 as previously described) is achieved. Further, the integral formation of bore 86 in steering axle 26 considerably reduces binding and wear caused by misalignment, and the massive, stiff steering axle 26 resists deflections during operation of vehicle 10. Thus, piston rod 94 is protected from side loading.

Referring to Figure 2, a connection between steering knuckles 70 and double-ended piston rod 94 may be by various conventional means. Preferably tie link 82 is pivotally fastened by a pivot pin 108 to piston rod 94.

Referring to Figure 4, a method for making integral power steering axle 84 shall now be described. Rigid beam 28, having the generally longitudinally extending, opposed lateral portions 38, and the medial portion 40 therebetween, has elongated bore 86 formed therein. Such formation is preferably by casting beam 28 with bore 86 being cored through the medial portion 40 of the casting, and trunions 42, 44 extending from medial portion 40 of the casting. Bore 86 is normally cast slightly under the desired, final diameter size, and may then be machined to within close tolerances so as to provide a smooth, cylindrical wall suitable as cylinder surfaces 88. Apertures 64, 66 are then machined in both lateral portions 38. This machining is fixtured, or oriented, with respect to bore 86. Piston assembly 90 is then slidably mounted in bore 86. Alternatively, bore 86 could be formed oversize and have a tubular cylindrical sleeve secured therein.

Referring to Figure 3, a pair of end caps 113 each having a bore 114 are inserted in opposite ends 116 of bore 86. A plurality of seals 120 are disposed in annular grooves in each end cap 113 for sealing engagement with piston rod 94. Seals 122 are disposed in annular grooves in each end cap 113 for sealing engagement with surface 88. Since power steering axle 84 is a rigid, integral structure, substantially no deflection of piston rod 94 with respect to end caps 113 will occur, and thus steering cylinder 83 is protected against binding during operation thereof. Referring to Figure 5, another embodiment of the present invention is illustrated, which, shall be denoted as integral power steering axle embodiment 84'. Integral power steering axle 84' is similar in construction to the previously described embodiment 84 and is substantially equivalent in function.

Accordingly, like reference numerals, but with the addition of a prime symbol, shall be used to describe similar or substantially equivalent structures.

Integral power steering axle 84' primarily differs from embodiment 84 in the manner of manufacture. Rather than the casting described for embodiment 84, integral power steering axle 84' forms a rigid beam 28' by fusing, e.g., welding, a plurality of plates 132, 134 and 136 and a cylinder housing 87' together. More particularly, housing 87' may be a cylindrically shaped tube having an elongated bore 86' therethrough. At each end 116' of bore 86' is welded an end plate 136. A pair of generally longitudinally extending top and bottom plates 132 are then welded to end plates 136. Top and bottom plates 132 extend beyond the junction of plates 136.

The extensions of top and bottom plates 132 beyond a medial portion 40' and end plates 136 are analogous to terminal portions 38 and hence are denoted as terminal portions 38'. Housing 87' is thus rigidly held between top and bottom plates 132, and has bore 86' extending in a direction generally parallel to lateral portions 38' of top and bottom plates 132. A pair of front and rear plates 134, each having a respective trunion 42', 44' affixed thereto, are welded to top and bottom plates 132 in a preferably generally perpendicular orientation with respect to end plates 136. Bores 64', 66' may then be machined in lateral portions 38'. The machining is oriented transversely with respect to and fixtured from bore 86'. A piston assembly 90' is then slidably mounted in bore 86'.

Industrial Applicability

The integral power steering axle embodiments 84, 84' find particular application as the steering axles of lift trucks, with fluid cylinders 83, 83' functioning to power the steering of roadwheels 22. However, it should be made obvious to those skilled in the arts relating hereto that integral power steering axle embodiments 84, 84' will find other applications, particularly applications in vehicles other than lift trucks.

As has been discussed above, kingpins 60 and the like, for interconnecting steering cylinder 83,83' and roadwheels 22 of a vehicle, may be assembled in very precise orientation with respect to the bores 86, 86' of steering cylinders 83, 83'. Thus, misalignments between piston assemblies 90, 90' and steering knuckles 70 are substantially prevented and piston rods 94, 94' are protected from side loading by the stiff cylinder housing 87, 87'.

Other aspects, objects, and advantages of this invenion can be obtained from a study of the drawings, the disclosure and the appended claims.

Claims

1. In a vehicle (10) having first and second wheels (22), a steering axle (26) and a steering cylinder assembly (83), said steering axle (26) having first and second end portions (38), said first and second wheels (22) being connected to said first and second end portions (38), respectively, said steering cylinder assembly (83) being positioned relative to said steering axle (26) and said first and second wheels (22) at a location sufficient for pivotally moving said wheels (22) relative to said steering axle (26), the improvement comprising: said steering axle (26) having a bore (86) extending through said steering axle (26) and opening on said first and second end portions (38) of said steering axle (26); and said steering cylinder assembly (83) having a housing (87) and a piston assembly (90), said housing (87) being defined by said steering axle (26) about said bore (86), said piston assembly (90) being movably positioned in said bore (86) and connected to said first and second wheels (22).

2. The vehicle (10) as set forth by claim 1 wherein said vehicle (10) has a frame (14) and said housing (87) includes trunions (42,44) generally transversely oriented to said bore (86) and connected to said frame (14) of said vehicle (10).

3. The vehicle (10) as set forth by claim 1 wherein said first and second end portions (38) of said axle (26) each has a pair of apertures (64, 66) and said vehicle (10) includes a pair of kingpins (60) each one of which is disposed in a respective one of said apertures (64, 66) and is connected to a related one of said wheels (22).

4. The vehicle (10) as set forth by claim 3 wherein: each of said first and second end portions (38) of said axle (26) includes a bifurcated structure (52) having spaced apart upper and lower arms (54, 56) and said pair of apertures (64, 66) in each of said first and second end portions (38) is defined in said upper and lower arms (54, 56).

5. The vehicle (10) as set forth by claim 3 wherein each of said pairs of apertures (64, 66) defines a longitudinal axis (68) and said bore (86) defines a longitudinal axis (89) transverse to and offset from said longitudinal axis (68) of each said pair of apertures (64, 66).

6. An integral power steering axle (84) comprising: a rigid beam (28) having a pair of opposed lateral portions (38) and a medial portion (40), said medial portion (40) having a bore (86) and being disposed between and extending outwardly of said lateral portions (38), said bore (86) extending in a direction generally parallel to said lateral portions (38); and a piston assembly (90) reciprocally mounted within said bore (86).

7. The integral power steering axle (84) as set forth by claim 6 further including: a vehicle (10) having a frame (14); and means (42,44) for connecting said beam

(28) to said frame (14) at said medial portion (40).

8. In a vehicle (10) having a steering axle (26) and first and second wheel assemblies (22), said steering axle (26) having first and second spaced apart end portions (38) and a medial portion (40), said first wheel assembly (22) being pivotally connected to said second end portion (38) of said steering axle (26), the improvement comprising: said medial portion (40) having first and second ends (41) and a bore (86) having a surface (88), said bore (86) extending through the medial portion (40) and opening at said first and second ends (91); and, a piston assembly (90) having a piston (92) and a rod (94), said piston (92) being slidably positioned in said bore (86) and in engagement with said surface (88), said rod (94) extending past said first and second ends (41) of said medial portion (40) and being connected to said first and second wheel assemblies (22).

9. A method for making an integral power steering axle (84, 84') comprising the steps of: forming a rigid beam (28, 28') having a medial portion (40, 40') and an elongated bore (86, 86') passing through said medial portion (40, 40'); and slidably mounting a piston assembly (90, 90') in said bore (86, 86').

10. The method as in claim 9 wherein said forming step includes fabricating said beam (28, 28') having a pair of opposed lateral portions (38, 38') each longitudinally extending from said medial portion (40, 40') in a direction generally parallel to said bore (86, 86') and machining a plurality of apertures (64, 66, 64 ',66') in said lateral portions (38,38').

11. The method of claim 10 further comprising the steps of: pivotally connecting wheels (22) to said lateral portions (38, 38') of said beam (28, 28') and connecting said piston assembly (90) to said wheels (22).

12. The method as in claim 10 wherein the fabricating of said beam (28) with said bore (86) in said medial portion (40) is by casting said beam (28).

13. The method as in claim 10 wherein the fabricating of said beam (28') with said bore (86') in said medial portion (40') is by fusing a plurality of plates (132, 134, 136) and a cylinder housing (87') together.