TRACTOR WITH FRONT SUSPENSION

Abstract: A tractor with a front wheel suspension and mechanical front wheel drive wherein the front wheel drive differential case (26) includes an engine oil sump replacing the need for a separate engine oil pump and wherein the suspension control arms (42, 62) are mounted to the differential case (26) through integrally formed mounting structures in the differential case (26). 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: Tractor with front suspension The present invention relates to a tractor with a front suspension. 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. It is an object of the present invention to provide a tractor with which the recited problems are overcome and the desires are met. In particular it is an object of the present invention to provide a tractor with an . axle suspension which requires relatively few components and which provides good ground visibility, high crop clearance, and a small turning radius . These and other objects are achieved by the present invention according to claim 1. Further advantageous arrangements and developments of the invention appear from the dependent claims . The tractor of the present invention overcomes the packaging difficulties described above and achieves the mentioned requirements. In an advantageous embodiment of the present invention the engine oil pan is integrated into the mechanical front wheel drive differential case and the suspension mounting bosses are integrated 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 front suspension components are mounted directly to a mechanical front wheel drive differential case. 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. The invention and further advantageous developments and arrangements of the invention will now be described and explained in more detail by way of example and with reference to the accompanying drawings in which: 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, and Fig. 5 is a top front perspective view of the front wheel drive differential case and right side suspension. 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 14 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 the 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 26 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 26 surrounds the sump 30 and engages the lower surface of the cylinder block 22 and is bolted thereto by bolts extending through the apertures 34 at the top of the differential case 26. The arrow 17 designates the forward longitudinal direction or orientation of the differential case 26. 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 46, 48 of the upper control arm 42 and the bore 38 in the upper mounting boss to pivotally attach the upper control arm 42. The upper control arm 42 thus rotates about the axis 40 to raise and lower the outboard end 52 of the upper control arm 42. At the front face 54 of the differential case 26, 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 62 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 58 to pivotally mount the lower control arm 62. 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 78 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 42, 62 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 92 for rotating the final drive assembly 92. The ball joints attaching the steering knuckle 88 to the control arms 42, 62 are disclosed in detail in the co-pending US patent application Ser. No. 09/662,609 (Attorney docket No. 15286-US) or in the co-pending European patent application filed at the same date as the present application (Attorney docket No. 15286 EP ), which hereby are 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 98 is coupled via a tie rod 102 on each side of the steering knuckle 88 whereby extension retraction of the rod 100 causes the steering knuckles 88 to rotate about the turning axis 90. The steering cylinder is disclosed in detail in the co-pending US patent application Ser. No. 09/661,832 (Attorney docket No. 15450-US) or in the co-pending PCT patent application filed at the same date at the EPO as the present application (Attorney docket No. 15450 WO ), which hereby are 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 42, 62 and spring member 108 are mounted to the differential 26 case through the integrally formed mounting bosses 36, 56, 104 on the side of the differential case 26. 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 20 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 .

Claims: Claims 1. A tractor comprising: rear wheels (12); front wheels (14) ; a chassis (16) to which the front and rear wheels (14, 12) are mounted; left and right upper and lower control arms (42, 62) having inboard ends (44, 68) mounted to the chassis (16) for pivotal motion about upper and lower axes (40, 84) respectively for up and down motion of outboard ends (52, 86) of the control arms (42, 62); and left and right steering knuckles (88) pivotally attached to the outboard ends (52, 86) of the left and right control arms (42, 62) respectively for pivotal motion about turning axes (90), the steering knuckles (88) carrying the final drive assemblies (92) ; left and right drive shafts (96) extending to final drive assemblies (92) carried by the steering knuckles (88) . 2. The tractor as defined by claim 1 comprising a steering cylinder (98) having an extendable rod (100) coupled to the steering knuckles (88) via tie rods (102) . 3. The tractor as defined by claim 1 or 2 wherein the chassis (16) including a cast front wheel drive differential case (26) with front drive shafts (96) extending laterally therefrom to the left and right final drive assemblies (92) coupled to left and right front wheels (14) to drive the front wheels (14) . 4. The tractor as defined by one of the claims 1 to 3 further comprising a steering cylinder (98) carried by the chassis (16) or the differential case (26), respectively, and having a rod (100) extending laterally from the cylinder (98) on both sides, the rod (100) being coupled to the steering knuckles (88) through tie rods (102) on each side whereby lateral movement of the steering cylinder rod (100) turns the steering knuckles (88) . 5. The tractor as defined by one or more of the preceding claims wherein the chassis (16) including an engine (18) having an engine block (22) and a cast front wheel drive differential case (26) attached to a lower end of the engine block (22), the differential case (26) forming an oil sump at an upper end thereof for engine lubricating oil. 6. The tractor as defined by one of the claims 3 to 5 wherein the differential case (26) is integrally cast with an upper mounting boss (36) to which the upper control arm (42) is attached. 7. The tractor as defined by one of the claims 3 to 6 wherein the differential case (26) is integrally cast with a lower mounting boss (58) to which the lower control arm (62) is attached. 8. The tractor as defined by claim 6 or 7 wherein the upper and lower mounting bosses (36, 58) define through bores (38, 60) that receive pivot pins (50, 74, 76, 78) attaching the upper and lower control arms (42, 62) to the differential case (26) for pivotal motion. 9. The tractor as defined by one of the claims 6 to 8 wherein the upper control arm (42) has a forked inboard end (44) with two spaced legs (46, 48) disposed on opposite sides of the upper mounting boss (36) on the differential case (26) with a single pivot pin (50) extending through the upper control arm (42) and the upper mounting boss (36) . 10. The tractor as defined by one of the claims 7 to 9 wherein the lower control arm (62) has a front and a rear attachment branch (64, 66} at the inboard end (68) thereof, the front branch (64) having a forked end (68) with two spaced legs (70, 72) on opposite sides of the lower mounting boss (58) and a single pivot pin (74) extending through the front branch (64) of the lower control arm (62) and through the lower mounting boss (58) . 11. The tractor as defined by one of the claims 7 to 10 wherein the lower mounting boss (58) is formed in a laterally extending flange (56) at a front face (54) of the differential case (26) . 12. The tractor as defined by claim 10 or 11 wherein the rear attachment branch (66) of the lower control arm (62) has a bore receiving a pivot pin (74, 76) that is bolted to the differential case (26) . 13. The tractor as defined by one of the claims 3 to 12 further comprising a spring mounting boss (104) integrally cast in the differential case (26) and a spring member (108) having one end coupled to the differential case (26) through the spring mounting boss (104) and a second end coupled to the lower control arm (62) . 14. The tractor as defined by one or more of the preceding claims wherein the chassis (16) or the differential case (26), respectively, has a pair of bolt holes (83, 85) receiving bolts (80, 82) to mount a rear pivot pin (76) for attaching the lower control arm (62) thereto .

Inventors: BOWMAN DENNIS AARON, BROWN JEFFREY KAHLE, JEFFRIES DENNIS LEE, SCHAFER CHRISTOPHER ALAN, BOWMAN, DENNIS, AARON, BROWN, JEFFREY, KAHLE, JEFFRIES, DENNIS, LEE, SCHAFER, CHRISTOPHER, ALAN
Applicants: DEERE & CO, DEERE & COMPANY
Application year: 2001
Main classification: B62D7
IPC codes: B60G3, B60G7, B60K17, B62D7, B62D49, F01M11