JP4297844B2 - Tractor power steering system - Google Patents

Description

  The present invention relates to an all-hydraulic power steering device provided in a tractor.

As the power steering device, for example, as disclosed in Patent Document 1, rolling fulcrum portions project from the center of the front axle case in the front-rear direction, and the leading end portion of the rolling fulcrum portion is provided on the body frame. It is known that the front and rear rolling fulcrum brackets are rotatably supported and a double rod type steering cylinder is mounted along the front axle case.
Japanese Patent Laid-Open No. 2001-130428

The main object of the present invention is to increase the strength of the rolling fulcrum portion against the vertical bending load and to deploy the steering cylinder in the recessed portion .

The first invention, before the tubular rolling fulcrum projecting integrally respectively before and after the horizontal center of the axle case, before and after the rolling fulcrum bracket provided a tip end shaft portion of the rolling supporting point of the front and rear machine frame And a power steering device for a tractor in which a double-rod type steering cylinder is mounted along the front axle case.
While forming a recessed portion recessed upwards between the front shaft case of the one rolling fulcrum portion and the front axle case at the lower part of one rolling fulcrum portion of the front and rear rolling fulcrum portions, The position of the upper end of the recessed portion is set to a position higher than the lower end of the tip shaft portion at the one rolling fulcrum portion , and the cylinder axis of the steering cylinder is downward with respect to the lateral axis of the front axle case. The steering cylinder is arranged so as to enter the recessed portion in a deviated state .

According to the said structure, a cylindrical rolling fulcrum part becomes a high intensity | strength with respect to an up-and-down bending load, and will become the thing excellent in durability in a rolling fulcrum.

According to a second invention, in the first invention,
One of the hydraulic oil supply and discharge pipes connected near the left and right ends of the steering cylinder extends to one side by bypassing the upper side of the one rolling fulcrum, and is placed close to the other pipe. There is something.

According to the above configuration, the pipe that bypasses the upper part of the rolling fulcrum crosses the lower part of the airframe frame. Therefore, when the front axle case rolls, the bypass pipe approaches the airframe frame. Since the steering cylinder is equipped with a deviation from the front axle case and a relatively large space is formed between the steering cylinder and the lower end of the fuselage frame, a bypass pipe is provided in this space. Thus, even if the front axle case rolls, the piping does not interfere with the fuselage frame.
Therefore, according to the second aspect of the invention, the two pipes extended from the steering cylinder can be grouped on one side of the airframe, and piping is easier than when the pipes are arranged on both the left and right sides of the airframe. It will be a thing.

According to a third invention, in the first or second invention,
The front over the lower portion of the axle case and the lower portion of the tip end shaft portion of the one of the rolling fulcrum, bridged the stay part to bypass the steering cylinder downwardly, the stay portion, when assembled in the steering cylinder Are formed with recesses that allow passage of pipe connection ports projecting from the left and right of the steering cylinder .

According to the above construction, the rolling fulcrum portion which is formed in a cylindrical shape towards the longitudinal direction that Do as further high strength against vertical bending load by erection of the stay portion.

A fourth invention is the invention according to any one of the first to third inventions,
The steering cylinder is inserted into and supported by cylinder support bosses provided on the left and right sides of the front axle case from the lateral direction, and the pipe connection ports protruding from the left and right sides of the steering cylinder are connected to the piston fixed to the front axle case. It is engaged with the rod cover.

  According to the above configuration, there is no need for a dedicated anti-rotation structure that prevents rotation around the cylinder axis of the steering cylinder (even if a dedicated anti-rotation structure is provided, a small-scale structure is sufficient), and the structure is simple There is an effect in making.

  FIG. 1 shows a four-wheel drive tractor provided with a power steering apparatus according to the present invention. In this tractor, a clutch housing 2 directly connected to the rear portion of the engine 1, a housing frame 3 having a sheet metal structure, a main transmission 4 comprising a hydrostatic continuously variable transmission (HST), a transmission case 5, and a differential case 6 are arranged in series. A front axle case 9 having left and right rear wheels 7 pivotally supported by a differential case 6 and left and right front wheels 8 being steerable. A lower body frame 10 connected to the engine 1 is mounted and supported in a freely rolling manner.

  The front wheel 8 is steered by an all-hydraulic power steering device PS. The structure of the power steering device PS is shown in FIGS.

A pair of front and rear rolling fulcrum brackets 11, 12 are connected to the lower part of the body frame 10, and front end shafts 13 a, 14 a of rolling fulcrum parts 13 , 14 projecting integrally from the left and right center of the front axle case 9. Is supported by the respective rolling fulcrum brackets 11 and 12 so as to be pivotally fitted, so that the entire front axle case 9 is pivotally supported around the rolling fulcrum P extending over the front and rear rolling fulcrum brackets 11 and 12. .

  The rear rolling fulcrum portion 14 is formed in a circular cylindrical shape concentric with the rolling fulcrum P, and a rearward input shaft 15 is inserted and supported therein, and the input power is transmitted to the left and right differential shafts 17 via the differential mechanism 16. Branching is transmitted. Although detailed description of the structure is omitted, the power for driving the front wheels is taken out from the transmission case 5 and then passed through the front wheel transmission (not shown) built in the clutch housing 2 to the input shaft 15. The front wheel 8 is driven at substantially the same peripheral speed as the rear wheel 7 in the straight traveling and the steering state within the set angle range, and the front wheel 8 is steered to the left and right more than the set angle. Then, the front wheel transmission is automatically operated, and the front wheel 8 is driven at a large speed.

The rolling fulcrum portion 13 on the front side is formed in a circular cylindrical shape concentric with the rolling fulcrum P, and a portion between the front end shaft portion 13a fitted in the rolling fulcrum bracket 11 and the front axle case 9 is semicircular in cross section. A recessed portion 18 is formed that is narrowed down and opened downward, and the cylinder steering cylinder 20 is horizontally supported so as to enter the recessed portion 18. A steering cylinder is provided so that the shaft center is deviated downward with respect to the lateral shaft center of the front axle case 9, and extends between the lower portion of the tip shaft portion 13 a and the lower portion of the front axle case 9 in the rolling fulcrum portion 13. A stay portion 13b that detours 20 downward is provided so that the cylindrical rolling fulcrum portion 13 has higher strength against vertical bending load. A concave portion 18a is formed in the stay portion 13b.

  As shown in FIG. 11, the steering cylinder 20 is a double rod type in which a piston rod 21 protrudes from both left and right ends, and the left and right ends of the piston rod 21 are connected to left and right tie rods 22 that steer the front wheel 8. The ball joints 23 are connected to each other.

  The steering cylinder 20 is fitted and supported from one lateral direction (rightward in FIG. 3) to cylinder support bosses 25a and 25b that project forward from the left and right sides of the front axle case 9. Here, one cylinder support boss 25b on the back side in the cylinder assembling direction is configured to be fitted into one end of the steering cylinder 20 to be received and supported in the cylinder axial direction, and in the cylinder assembling direction. The other cylinder support boss 25a on the front side is configured to support the other end of the internally fitted steering cylinder 20 with a stopper ring 26 so as not to come off. Further, pipe connection ports 27a and 27b for supplying and discharging pressure oil are provided on the outer periphery near the left and right ends of the steering cylinder 20, and as shown in FIG. 9, a cylinder support located on the front side in the cylinder assembling direction is provided. The boss 25a is formed with a recess 28 that allows passage of the pipe connection port 27b.

  The steering cylinder 20 that is fitted and supported by the left and right cylinder support bosses 25a and 25b is rotated around the cylinder axis so that the pipe connection ports 27a and 27b face upward, and then is connected to the pipe connection ports 27a and 27b. Pipes 30a and 30b made of pressure-resistant hoses are connected via elbows 29a and 29b. Here, one pipe 30a is arranged outside the frame 10, while the other pipe 30b is detoured to the vicinity of the one pipe 30a through between the rolling fulcrum portion 13 and the frame 10, Two pipes 30a and 30b are collectively connected to a steering controller (not shown).

  Further, a piston rod cover 32 made of a metal plate material is attached and fixed over the cylinder supporting bosses 25a and 25b and a boss portion 31 projecting from the front axle case 9, and is formed at the inward edge of each piston rod cover 32. Engaging the recessed portion 33 with the pipe connection ports 27a and 27b prevents the steering cylinder 20 from rotating around the cylinder axis.

Overall side view of tractor Top view of power steering device Front view of power steering device Longitudinal side view of rolling center part Vertical side view showing piston rod cover attachment Cross-sectional plan view of the rolling center part Front view of a part of the front axle case AA sectional view in FIG. BB sectional view in FIG. CC sectional view in FIG. Perspective view of steering cylinder and piston rod cover

Explanation of symbols

9 Front axle case 10 Airframe frame 11 Rolling fulcrum bracket 12 Rolling fulcrum bracket 13 Rolling fulcrum part 13a Tip shaft part 13b Stay part 14 Rolling fulcrum part
14a Tip shaft portion 18 Recessed portion
18a Recessed portion of stay portion 25a Cylinder support boss 25b Cylinder support boss 27a Piping connection port 27b Piping connection port 32 Piston rod cover

Claims (4)

Before a cylindrical rolling fulcrum projecting integrally respectively before and after the horizontal center of the axle casing, rotatably supporting the tip end shaft portion of the rolling supporting point of the front and rear in the longitudinal rolling fulcrum bracket provided on the body frame And a power steering device for a tractor in which a double rod type steering cylinder is mounted along the front axle case,
While forming a recessed portion recessed upwards between the front shaft case of the one rolling fulcrum portion and the front axle case at the lower part of one rolling fulcrum portion of the front and rear rolling fulcrum portions,
The position of the upper end of the recessed portion is set to a position higher than the lower end of the tip shaft portion in the one rolling fulcrum portion,
The power of the tractor , wherein the steering cylinder is disposed in the recessed portion with the cylinder axis of the steering cylinder deviating downward with respect to the lateral axis of the front axle case. Steering device. One of the hydraulic oil supply and discharge pipes connected near the left and right ends of the steering cylinder extends to one side by bypassing the upper side of the one rolling fulcrum, and is placed close to the other pipe. The power steering device for a tractor according to claim 1. A stay portion that bypasses the steering cylinder downward is constructed across the lower portion of the tip shaft portion and the lower portion of the front axle case in the one rolling fulcrum portion ,
The power steering device for a tractor according to claim 1 or 2, wherein a recess is formed in the stay portion to allow passage of pipe connection ports projecting from the left and right of the steering cylinder when the steering cylinder is assembled .   The steering cylinder is inserted into and supported by cylinder support bosses provided on the left and right sides of the front axle case from the lateral direction, and the pipe connection ports protruding from the left and right sides of the steering cylinder are connected to the piston fixed to the front axle case. The power steering device for a tractor according to any one of claims 1 to 3, wherein the power steering device is engaged with a rod cover.

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