GB2141081A - Front wheel driving apparatus - Google Patents

Abstract

A front-wheel driving apparatus for use in tractors and the like has bevel-gear cases on each of which a front-wheel case is fitted for free rotation about a kingpin axis, the front-wheel case being adapted to support a front wheel and accommodate therein a bevel-gear train which is for incorporating the kingpin and the front wheel. Both upper and lower end portions of the kingpin are supported on the bevel- gear case via the respective bearings, and are provided with the respective bevel pinions as mounted thereon so as to exert axial thrusts on the kingpin in directions opposite to each other, and further with the respective thrust retainers as secured thereon for taking up any possible overall balance thrust. A hub base is consolidatedly incorporated in the front-wheel case, and on the hub base there is fitted, for free rotation, through a bevel gear fixture base a bevel gear which meshes with the lower bevel pinion on the kingpin. The front wheel is mounted on an outer end portion of the bevel gear fixture base. <IMAGE>

Description

SPECIFICATION Front-wheel driving apparatus Background of the Invention (1) Field of the Invention This invention relates to a front-wheel driving apparatus in which a bevel-gear case is fixed to each end of a front-wheel axle case, a kingpin is fitted in the bevel-gear case, and a front-wheel case is mounted for free rotation about the kingpin axis.

(2) Description of the Prior Art Front-wheel driving apparatuses for tractors, of the structure as mentioned just above, are well known for instance as disclosed in JP-U SHO. 56-139223 and US-Patent 2306958.

In such known apparatuses, the mode supporting the kingpin is in such manner that both upper and lower ends of the kingpin are supported on both the bevel-gear case and the front-wheel case. On account thereof, particularly of thusly required lower bearing, the bevel gear for speed reduction can not be made large enough and therefore the reduction ratio can not be large as desired.

Further, so to a hub base, it is supported on a pair of inner and outer bearings, while the bevel gear is fixedly secured on this hub base, in view that the hub base is free to rotate relative to the front-wheel case. On account thereof, this hub base must inevitably be of considerable length, and therefore the front wheel can not be disposed close enough, as desired, to the kingpin, thus to result in supporting the front wheels rather unstably and also in making the tread of the front wheels considerably long. Summary of the Invention This invention has as its object to overcome the shortcomings of the conventionl front-wheel driving apparatuses as mentioned above.In order to attain the object, the frontwheel driving apparatus according to this invention of the type such that on both ends of a front-axle case there respectively are mounted bevel-gear cases each accommodating therein a bevel-gear train for interlocking a differential output shaft and a kingpin; that at each of the bevel-gear cases there is provided a front-wheel case, for free rotation about the kingpin axis, for supporting a front wheel; and that within the front-wheel case there is accommodated a bevel-gear train for interlocking the kingpin and the front wheel: is characterized in that both upper and lower end portions of the kingpin are supported on the part of the bevel-gear case side respectively via bearings; that on both said upper and lower end portions of the kingpin there respectively are mounted bevel pin ions which are constituent parts of the respective bevelgear trains, as disposed so as to respectively exert axial thrusts on the kingpin in directions opposite to each other; that on the upper and lower tip end portions of the kingpin there further are secured, respectively, thrust retainers for taking up any possible overall balance thrust; that a hub base is consolidatedly incorporated in the front-wheel case; that on the hub base there is fitted, for free rotation, through a bevel gear fixture base a bevel gear which meshes with the lower bevel pinion on the kingpin; and that the front-wheel is mounted on an outer end portion of the bevel gear fixture base.

In the front-wheel driving apparatus according to this invention as above, since the kingpin is supported, by means of the pair of upper and lower bearings, on the bevel-gear case fixed to each end of the front-wheel axle case, in the said manner namely such that the axial thrusts, exerted on the kingpin respectively by the upper and lower bevel pin ions, are in directions opposite to each other for thus effectively canceling each other, it is hereby possible to minimize the kingpin bearing and also to enlarge the speed reduction ratio. Thus, any possible overall balance thrust acting axially on the kingpin can now securely and simply taken up by the thrust retainers mounted on tip end portions of the kingpin, leading therefore to simplification of the structure.As is especially advantageous, it is possible to make the lower kingpin bearing without any duty of taking up the axial thrust, thus to construct same as a simple plane bearing, to therefore result in the kingpin substantially of single-end support type.

Furthermore, since the hub base is consolidatedly incorporated in the front-wheel case and on the hub base there is fitted for free rotation the bevel gear; the hub-base supporting structure is simpler and stabler in comparison with the structure in the case of rotating hub base, and it is hereby possible to make the hub base as supported in cantilever manner and short in size, which is advantageous also in view of structural strength and allows to dispose the front wheel, which is mounted on the outer end portion of the bevel gear fixture base, close enough to the kingpin as desired, and to therefore make the tread of the front wheels short enough. Still further advantages of this invention will become clear from the detailed description given hereunder with reference to the accompanying drawings.

Brief Description of the Drawings Fig. 1 is an overall side elevation of a tractor as a specific example of the vehicle in which the appratus of this invention is incorporated, Fig. 2 is a sectional side elevation of the apparatus according to this invention, Fig.

3 is an end view of a bevel-gear case fixture portion, cut in half, Fig. 4 is a side view of a knuckle arm, and Fig. 5 is a view similar to Fig. 2 but showing a modified embodiment of this invention.

Description of the Preferred Embodiments Referring to the drawings, the illustrated embodiments of this invention are described in detail hereunder: Shown in fig. 1 is a tractor 1 of two-axle four-wheel type, thus with a pair of left and right front wheels 2 and a pair of left and right rear wheels 3, the front wheels 2 being mounted on both ends of a front-axle case 4 so as to be steerable by means of a steering apparatus 5.

The rear wheels 3 are driven via a transmission apparatus designed for suitable speed changing of the engine power output, the transmission appparatus being accommodated within a transmission case 6 which dually serves also for constituting a chassis.

The front-wheel case 4 is suspended, at its axial central portion, from a front-axle support 7 via a so-called center-pin apparatus 8, for free rocking about an axis extending in the fore-and-aft direction.

Within the front-axle case 4 there is accommodated a differential apparatus which is operatively driven by the transmission apparatus within the transmission case 6, via a propeller apparatus F, so that the front wheels and the rear wheels are synchronously or tunedly drivable.

Further details of the front-wheel driving apparatus are seen in Fig. 2 and also the views subsequent thereto.

By the way, both ends of the front-axle case 4 are each provided with the respective units of the front-wheel driving apparatus, but in view that the left and right units in such pair are identical in their structure, description in detail is given hereunder only with respect to one unit of the pair.

Referring to Fig. 2, a differential output shaft 9 is insertedly supported within the front-axle case, more specifically is provided at its tip end with a bevel pinion 10 mounted there by means of splining or the like, and is supported on the front-axle case tip end via a bearing 11.

Around the front-axle case tip end there is formed a fixture flange 12, and a bevel-gear case 1 3 is detachably fixed on to the fixture flange 1 2 by means of knock pins 14 and bolts 14A, as shown also in Fig. 3.

The bevel-gear case 1 3 has an opening 1 5 at its upper portion, while at its lower portion there is formed a tubular portion 1 6 of a contracted diameter; the opening 1 5 and the tubular portion 1 6 being coaxially aligned, thus having one and the same, common axis.

Within the bevel-gear case 1 3 there is fitted a kingpin 1 7 as slanted in a set kingpin angle.

In the illustrated embodiment, the kingpin 1 7 has its upper end supported via a radial bearing 1 8 and has its lower end fitted in the tubular portion 1 6 and supported via a needle bearing 19.

The kingpin 1 7 and the differential output shaft 9 are operatively iriterconnected via a bevel-gear train 20 accommodated within the bevel-gear case 1 3. The bevel-gear train 20- is constructed by securely fitting an upper bevel pinion 21 on an upper end portion of the kingpin 1 7 by means of splining, keying or the like, and having the upper bevel pinion 21 mesh, from above, with a mating bevel pinion 10 fitted on the differential output shaft 9.

On a lower end portion of the kingpin 1 7 there is securely fitted a lower bevel pinion 23 via a collar 22 by means of splining, keying or the like, and the lower bevel pinion 23 meshes, from below, with a mating bevel gear 25 accommodated within a front-wheel case 24, to thus construct a bevel-gear train 26 for operatively interconnecting the kingpin 1 7 and an associated front wheel.

In this way, the kingpin 1 7 is borne and held in place, at both its upper end lower end portions, only by the bevel-gear case 1 3 via the bearings 18, 1 9. and in order to bear the thrusts caused by the bevel pinions 21, 23 disposed as mentioned above to result in the thrusts acting on the kingpin 1 7 as tensile stresses as shown by arrows A and B, there are screwedly fixed, on threaded portions of the kingpin at both its outer end portions beyond the resrective bearings 1 8 and 19, thrust retainers 27 and 28 illustrated as the respective nuts.

The front-wheel case 24 consists integrally of a lower case 29 and a lateral case 30, is thus generally of L-shape as viewed from the rear, and accommodates therein the bevelgear train 26 consisting of the lower bevel pinion 23 and the bevel gear 25.

The lower case 29 is attached to the tubular portion 1 6 of the bevel-gear case 1 3 in a manner of being fitted thereon for free rotation via an inner ring 31 and a bush 31', and is further supported via a thrust bearing 32.

The lateral case 30 opens laterally outwardly and has ample open portion 33 sufficient for freely fitting in and out therethrough the bevel gear 25, and on its inner lateral wall 34 there is formed a hub base 35 of hollow structure as is integrally formed to outwardly protrude therefrom, and on this hub base 35 there is fitted a bevel-gear fixture base 37, for free rotation, in the illustrated embodiment via two juxtaposed ball bearings 36.

The bevel-gear fixture base 37 is generally of ring shape, and on to its inner end face the bevel gear 25 is properly secured by means of knock pins 38 and bolts 39, while on to its outer end face there is detachably mounted a wheel disc 41, of the associated front wheel, by means of a plurality of bolts 40.

Furthermore, the open portion 33 of the case 30 is covered up with a lid 44, by means of knock pins 42 and bolts 43, and on an upper edge portion of the inner lateral wall 34 of the lateral case 30 there is formed an upright fixture flange 45 in integral protrusion therefrom, extending in the illustrated embodi ment in parallel to the axis of the kingpin, and to this fixture flange 45 there is mounted a knuckle arm 46 in a manner as now described hereunder:In the opening 1 5 of the bevel gear case 1 3 there is fitted a knuckle pin 47 coaxially with the kingpin 1 7. In the illustrated embodiment, the fitting is in a manner of clamping insertion, blocking the relative rotation by constructing the fitting portion of the knuckle pin as is provided with transverse depressions and by forcibly fitting two pins or flat plates 48 into such depressions. It is well possible, by providing the structure for realiz ing sufficiently strong clamping insertion, to omit such pins or plates 48.

Though the knuckle pin 1 7 in this specific embodiment is of top-closed hollow cylindrical shape, it is as well possible to construct same in hollow cylindrical shape open in both upper and lower ends or as a solid cylinder or column. In the case of a top-closed hollow cylinder as in the illustrated instance, it is possible to inject lubicant such as grease or the like, via an oiling-plug fixture hole 49 formed in its top, into its interior space there under and confine it there, thus for lubricating the bearing 18. Accordingly, the bearing 18 is in such case provided with a seal 1 8A.

The knuckle arm 46 has, as integral components, a bottom-closed fitting portion 50 and fixture flanges 51. The fitting portion 50 is of hollow cylindrical shape and is fitted on the knuckle pin 47 via a bush 52, for free rotation. As shown in Fig. 4, the fixture brackets 51 extend from the fitting portion 50 in foreand-aft direction, and are abuttedly opposed on to the upright fixture flange 45 on the part of the front-wheel case side and mounted thereto in the illustrated instance by means of two bolts 53 each on either of fore and aft sides, fitted transversely from the inner side.

For the purpose, the fixture flange 45 is provided with tapped bores 45A and the fixture brackets 51 are provided with so-called dummy holes 51A, namely through bores amply and freely to pass the bolts, in aligned registration with the respective mating tapped bores 45A.

By the way, the knuckle arm 46 is provided with a steering arm, though not illustrated, in protrusion either forwardly or rearwardly or else laterally inwardly therefrom, as is integral therewith or is attached thereto via bolts or the like. It is of course so adapted that the steering force driving from the steering apparatus 5 is transmitted to the steering arm, and that the pair of left and right steering arms are interlocked via a tie rod or the like.

Further designated in Fig. 2 are: at 54 a stopper annulus for the bearing 18, at 55 a seal ring interposed in between the fitting portion 50 and the knuckle pin 47, at 56 a dust seal interposed to be confined in an annular space as is defined in between the bevel-gear case 1 3 and the lower case 29 of the front-wheel case 24, at 57 a dust seal interposed to fill an annular adjourning portion in between the lid 44 and the bevelgear fixture base 37, at 58 a lubricant oil passage providing communication in between the tubular portion 1 6 and the lower case 29, and at 59 a lubricant oil passage or passages formed at the portion supporting the bearing 11 outer periphery.It is thus possible to apply the lubricant oil into the lower case 29 at the level near the bearing as well as into the bevel-gear case 13, while purging out previously prevailing air, by injecting the lubricant oil via a non-illustrated oiling plug as is provided on the front-axle case 4 to thus pass through the passages 58 and 59. Shown still further to 60 is a lower-case-bottom covering lid and at 61 a hub lid, they both being free to attach and to detach.

Yet further, the inner lateral wall 34 of the frontwheel case 24 is provided, though not illustrated, with steering-angle-restraining stoppers formed thereon as disposed respectively forwardly and rearwardly of the kingpin, substantially symmetrically with respect thereto, and for the purpose the bevel-gear case is accordingly provided with the respective mating stoppers.

Fig. 5 is similar to Fig. 2, but shows a second embodiment which differs from the previous, namely a first, embodiment per said Fig. 2 only in that the previously provided lubricant oil passage 58 is now omitted.

Otherwise, the construction is identical with each other, and so like parts are all designated by like reference symbols.

Function of such structure is now described hereunder: As the differential output shaft 9 is driven, then the kingpin 1 7 is driven as interlocked via the bevel-gear train 20. Here in these instances, the power is further transmitted such that the bevel-gear fixture base 37 is driven, via the bevel-gear train 26, to rotate about the hub base 35, and thus the front wheels 2 are driven under the predetermined speed reduction (might as well be speed augmentation if so desired) synchronously - 1 2 or tunedly with respect to the rear wheels 3.

When the steering apparatus 5 is maneuvered for left or right steering, then each of the front wheels 2 is accordingly rotated, together with the associated front-wheel case 24, about the axis of the kingpin 1 7 to thus realize the intended steering, on account that the knuckle arm 46 is fitted, for free rotation and coaxially with the axis of the kingping 17, on the knuckle pin 47 which is in turn fitted, without possibility of relative rotation, into the top opening 1 5 of the bevel-gear case 13, and that the fixture bracket 1 5 of the knuckle arm 46 is securely fixed, by means of the bolts 53, to the upright fixture flange 45 on the part of the front-wheel case 24 side.

Slant load of the front-wheel case 24 is substantially borne by the knuckle pin 47 without subjecting the bolts 53 to any substantial loading, on account that on the one hand the fitting portion 50 of the knuckle arm 46 is made as bottom-closed and is fitted on the knuckle pin 47 and that on the other hand the knuckle arm 46 is fixed on to the part of the front-wheel case 24 side by means of the bolts 53. Therefore, the bolts 53 may be screwed in, from the laterally inner side, and easily tightened up without any serious hindrance thereagainst with the front wheel 2, and if any front wheel 2 may come to float, then the bolts 53 can serve for securely supporting same.

In thus transmitting the torque from the differential output shaft 9 via the bevle-gear grain 20 to the kingpin 1 7 and further the torque from the kingpin 1 7 via the bevel-gear train 26 to the front wheel 2, axial thrusts acting on the kingpin 1 7 result in tensile stresses as shown by arrows A and B, this meaning that the bearings 1 8 and 1 9 for supporting the kingpin 1 7 may both safely be made compact, the overall or ultimate balance axial thrust being sufficiently coped with by means only of the thrust retainers 27 and 28.

Logically, this further means that it is not required to have the bottom end of the kingpin 1 7 supported on the front-wheel case 24, and such omission of supporting connection at the bottom results in allowing to accordingly enlarge the diameter of the bevel gear 25, to thus obtain a larger ratio of the speed reduction.

Furthermore, since the hub base 35 is made integral with the front-wheel case 24, as the base on which the bevel gear 25 unit is fitted for free rotation, the wheelsupporting structure is far simpler and stabler than in the case of the structure with rotating hub bases.

In consequence hereof, it is now possible to provide substantially short hub base 35 in so supporting same in such cantilever manner, and since the axial length of the hub base 35 is thusly short, it in turn is possible to dispose the front-wheel close enough to the bevel-gear case 1 3 to thus shorten the steering arm length and therefore to realize agile steering operation.

Claims (3)

1. A front-wheel driving apparatus of the type such that on both ends of a front-axle case (4) there respectively are mounted bevelgear cases (13) each accommodating therein a bevel-gear train (20) for interlocking a differential output shaft (9) and a kingpin (17); that at each of the bevel-gear cases (13) there is provided a front-wheel case (24), for free rotation about the kingpin (17) axis, for supporting a front wheel (2); and that within the front-wheel case (24) there is accommodated a bevel-gear train (26) for interlocking the kingpin (17) and the front wheel (2); the front-wheel driving apparatus being CHARAC TERIZED IN THAT both upper and lower end portions of the kingpin (17) are supported on the part of the bevel-gear case (13) side respectively via bearings (1 8, 19); that on both said upper and lower end portions of the kingpin (1 7) there respectively are mounted bevel pinions (21, 23) which are constituent parts of the respective bevel-gear trains (20, 26), as disposed so as to respectively exert axial thrusts on the kingpin (17) in directions opposite to each other; that on the upper and lower tip end portions of the kingpin (17) there further are secured, respectively, thrust retainers (27, 28) for taking up any possible overall balance thrust; that a hub base (35) is consolidatedly incorporated in the front-wheel case (24); that on the hub base (35) there is fitted, for free rotation, through a bevel gear fixture base (37) a bevel gear (25) which meshes with the lower bevel pinion (23) on the kingpin (17); and that the front-wheel (2) is mounted on an outer end portion of the bevel gear fixture base (37).

2. The front-wheel driving apparatus of claim 1, characterized in that the mode of supporting the kingpin is such that the bearing (18), of radial type, disposed at the upper end portion of the kingpin, essentially takes up the kingpin load, thus substantially of singleend support type.

3. The front-wheel driving apparatus of claim 2, characterized in that the kingpin (17) is supported at its lower end portion by the bearing (19) which is of needle type.