Abstract:
A tractor with a front wheel suspension and mechanical front wheel drive wherein the front wheel drive differential case includes an engine oil sump replacing the need for a separate engine oil sump and wherein the suspension control arms are mounted to the differential case through integrally formed mounting structures in the differential case. These mounting. structures reduce the number of front end components thereby improving the packaging of the suspension, steering and front wheel drive. The elimination of the oil: pan allows the front axle ground clearance to be increased while improving ground visibility in front of the tractor over the hood.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a tractor with a front suspension and particularly to a tractor where the front suspension components are mounted directly to a mechanical front wheel drive differential case. 
     2. Description of Related Art 
     To improve tractor performance, front axle suspension systems are becoming more commonplace. A front suspension provides improved operator comfort, thereby reducing operator fatigue. In addition, the tractor frame is subjected to less impact loading during operation. A front suspension axle, however, adds complexity and additional components to the front axle. 
     To further improve the performance of agricultural tractors, many tractors are provided with mechanical front wheel drive. While the front wheels and tires are typically smaller than the rear, by driving both the rear and the front wheels, tractive efficiency is improved. A mechanical front wheel drive requires a front drive axle with considerably more components compared to a front axle without front wheel drive. 
     Many competing design requirements make it difficult to package front wheel drive and a front axle suspension in a tractor. These design requirements include: ground visibility over the hood; high crop clearance; and a small turning radius. These requirements place a premium on space at the front axle, especially with front wheel drive and a front wheel suspension. 
     SUMMARY OF THE INVENTION 
     The tractor of the present invention overcomes the packaging difficulties described above by integrating the engine oil pan into the mechanical front wheel drive differential case and by integrating the suspension mounting bosses into the differential case casting. The integration of the oil pan into the differential case eliminates the need for a separate oil pan and the vertical packaging space needed for the pan. This enables both the crop clearance and the front ground visibility over the hood to be improved. 
     The differential case itself is an integral part of the tractor frame. There are no frame members extending longitudinally of the tractor along side or beneath the engine. The differential case is the frame. While the engine oil pan has previously been integrated into the tractor frame, the front drive axle has been a beam structure in which the front differential is part of a pivoting axle beam. This front beam axle is pivotally mounted to the frame about a longitudinal axis but it is not suspended from the frame. 
     The integration of the suspension mounting bosses into the differential case casting reduces the number of components needed to attach the suspension system control arms to the vehicle structure, in this instance, the differential case. By eliminating components, more space is available for the suspension arms, the drive shaft, the steering cylinder and tie rods. 
     The suspension system is an independent suspension having upper and lower control arms on each side of the differential case extending outward to steering knuckles that support final drive assemblies. The left and right sides of the suspension system are mechanically independent from one another. The left and right sides are coupled through a common gas accumulator providing fluid pressure to hydraulic cylinders on each side of the suspension. 
     A steering cylinder is also carried by the differential case having a cylinder rod extending from both sides of the differential case to which tie rods are attached and extend to the steering knuckles. The upper control arm has an inboard end attached to a mounting boss projecting laterally outward from the differential case. The inboard end of the upper control arm is:forked, having two spaced apart legs that are placed on opposite sides of the mounting boss. A single pivot pin extends through both legs of the upper control arm and through the mounting boss to pivotally attach the upper control arm to the differential case. The lower control arm has two separate attachments to the differential case. A forward branch of the control arm is forked, like the upper control arm, and has a pivot pin extending through the two spaced legs of the fork and through a mounting boss extending laterally from the differential case. The rear branch of a lower control arm has a rear pivot pin extending therethrough that is bolted directly to the side of the differential case. No separate mounting brackets are attached to the differential case for attachment to the control arms. 
     In addition to the control arms, the suspension includes a hydraulic cylinder that functions as a spring. The hydraulic cylinder is bolted to a mounting boss on the differential case at one end and has an extending rod that is bolted to the lower control arm to carry the suspended tractor mass. By integrating the suspension attachments into the differential case, fewer components are required for the suspension, thus providing the designer with greater flexibility in locating axle components. In addition, greater visibility through the axle to the ground between the tires and the tractor hood is obtained. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a left side view of the tractor of the present invention. 
     FIG. 2 is a perspective view of the tractor engine, front wheel drive differential case and right front axle. 
     FIG. 3 is a right front perspective view of the front wheel drive differential case. 
     FIG. 4 is a bottom front perspective view of the front wheel drive differential case and right side suspension. 
     FIG. 5 is a top front perspective view of the front wheel drive differential case and right side suspension. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     With reference to FIG. 1, a tractor  10  with a front suspension according to the present invention is shown. The tractor  10  includes rear tires  12  and front tires  14 . The front tires are steering tires and rotate about upright turning axis described below to steer the vehicle. A chassis  16  supports both the front and rear tires. In the description that follows and the drawings, only the right hand side of the suspension is shown. Both sides are essentially identical in structure. 
     An engine  18  (FIG. 2) is part of th e chassis and is concealed by the hood  20 . The engine  18  includes a cylinder block  22  having a lower end  24 . Instead of attaching a conventional oil pan to the bottom of the block  22 , the block  22  is attached to a front wheel drive differential case  26 . The differential case has a large recess  28  at the upper end that forms a sump  30  (FIG. 3) for engine lubricating oil. The upper face  32  of the differential case surrounds the sump  30  and engages the lower surface of the cylinder block and is bolted thereto by bolts extending through the apertures  34  at the top of the differential case. The arrow  17  designates the forward longitudinal direction or orientation of the differential case. 
     The differential case  26  is a cast body that is formed with an upper mounting boss  36  extending laterally on each side of the differential case. The upper mounting boss  36  has a central bore  38  therethrough defining an axis  40  extending generally fore and aft of the tractor but not necessarily horizontally. 
     The upper mounting boss  36  is used to mount an upper suspension control arm  42  shown in FIGS. 2,  4  and  5 . The upper control arm  42  has an inboard end portion  44  that is forked, having two spaced apart legs  46  and  48 . The legs  46 ,  48  are disposed on opposite sides of the mounting boss  36  and an upper pivot pin  50  extends through the two legs of the upper control arm and the bore  38  in the upper mounting boss to pivotally attach the upper control arm. The upper control arm thus rotates about the axis  40  to raise and lower the outboard end  52  of the upper control arm. 
     At the front face  54  of the differential case, a laterally extending flange  56  includes a front lower mounting boss  58 ; having a through bore  60 . A lower control arm  62  is pivotally mounted to the front boss  58 . The lower control arm has a front branch  64  and a rear branch  66 . The front branch  64  has a forked inboard end portion  68 . The forked front branch  64  has legs  70 ,  72  disposed on opposite sides of the mounting boss  58 . A front lower pivot pin  74  extends through the legs  70 ,  72  and the bore  60  in the mounting boss to pivotally mount the lower control arm. 
     A rear lower pivot pin  76  extends through a bore in the inboard end of the rear branch  66  and is bolted to the differential case by a pair of bolts  80 ,  82 . The bolts  80 ,  82  are threaded into apertures  83 ,  85  respectively in the differential case. The front lower pivot pin  74  and the rear lower pivot pin  76  define a lower pivot axis  84  (FIG. 4) about which the lower control arm  62  rotates to raise and lower the outboard end  86  of the lower control arm. 
     The outboard ends  52 ,  86  of the upper and lower control arms are coupled to a steering knuckle  88  through ball joints whereby the steering knuckle  88  can rotate about an upright axis  90  (FIG. 2) to turn the front tires  14 . The steering knuckle  88  supports a final drive assembly  92  having a wheel flange  94  to which the wheels supporting the tires  14  are attached. A drive shaft  96  (FIG. 2) extends from the differential case  26  to the final drive assembly for rotating the final drive assembly. The ball joints attaching the steering knuckle to the control arms are disclosed in detail in a co-pending patent application designated by attorney reference number 15286 filed the same date as the present application and hereby incorporated by reference. 
     The differential case  26  also carries a steering cylinder  98  having an extendable cylinder rod  100 . The rod  100  extends laterally outward on both sides of the differential case  26 . The steering cylinder rod  100  is coupled to the steering knuckle  88  by a tie rod  102  whereby extension retraction of the rod  100  causes the steering knuckles to rotate about the turning axis  90 . The steering cylinder is disclosed in detail in a co-pending patent application Ser. No. 09/661,832 filed the same date as the present application and hereby incorporated by reference. 
     With reference once again to FIG. 3, the differential case  26  is further formed with a spring mounting boss  104  extending laterally on each side of the differential case. The mounting boss  104  has a bore  106 . A hydraulic cylinder  108  has a end portion  110  mounted to the spring boss  104  by a fastener  112 . The cylinder  108  has an extendable rod  114  that is coupled to the lower control arm  62  via a fastener  116 . The cylinder  108  is in fluid communication with a hydraulic system through ports  118 . The hydraulic system includes one or more gas filled accumulators whereby the cylinder  108  functions as a spring for the suspension. 
     The differential case  26  is reinforced by braces  120  extending across the oil sump  30  between the left and right upper mounting bosses  36 . A second brace  122  extends across the sump between the spring mounting bosses  104  on each side. The braces  120 ,  122  provide improved structural strength to the differential case. 
     The front suspension control arms and spring member are mounted to the differential case through the integrally formed mounting bosses on the side of the differential case. This reduces the number of components used to attach the suspension system and avoids the need of separate parts bolted to the differential case to which the control arms and spring member are then attached. This provides improved visibility through the axle area, enabling the operator to see the ground and crop row between the front tires  14  and the tractor hood  20 . In addition, the elimination of additional components provides free space for packaging other components as necessary. The use of the differential case  26  as a sump for engine lubricating oil eliminates the need for a separate oil pan thereby reducing the vertical height of the tractor hood and/or allowing the front axle crop clearance to be increased. 
     The invention should not be limited to the above-described embodiment, but should be limited solely by the claims that follow.