GB2356181A

GB2356181A - A steering cylinder mounting structure for a working vehicle

Info

Publication number: GB2356181A
Application number: GB0004971A
Authority: GB
Inventors: Naoki Onishi; Yuichi Fujikawa; Satoshi Oizumi; Seiji Nishimura
Original assignee: Kubota Corp
Current assignee: Kubota Corp
Priority date: 1999-11-10
Filing date: 2000-03-01
Publication date: 2001-05-16
Anticipated expiration: 2020-03-01
Also published as: JP2001130422A; IT1316708B1; FR2800692A1; ITMI20000419A0; GB0004971D0; GB2356181B; JP3474135B2; ITMI20000419A1; FR2800692B1

Abstract

A steering cylinder mounting structure for a working vehicle with a steering cylinder (20) disposed forwardly or rearwardly of a front axle case (14) for steering front wheels (4). An elongate cylinder mounting member of C-shaped cross-section (21) having cylinder mounts (21a) for attaching the steering cylinder is fixed to the front axle case to extend longitudinally of the front axle case so as to surround at least part of the front axle case.

Description

2356181 STEERING CYLINDER MOUNTING STRUCTURE FOR A WORKING VEHICLE

BACKGROUND OF THE INVENTION

FIELD OF THE INVENTION

This invention relates to a steering cylinder mounting structare for a working vehicle with a front wheel steering cylinder disposed forwardly or rearwardly of a front axle case.

DESCRIPTION OF THE RELATED ART

In a conventional steering cylinder mounting structure for a working vehicle noted above, a steering cylinder is bolted to a cast front axle case.

According to the prior art structure, the entire front axle case must have an increased wall thickness for sufficient strength to support the: -.steering cylinder. The increased wall thickness results in- a disadvantage of an increased weight of the front axle case. In addition, it is necessary to form a seating for the steering cylinder to be integral with the front axle case. This requires a mold of complicated shape, resulting in an inconvenience of high manufacturing cost.

SUMMARY OF THE INVENTION

An object of this invention is to provide a mounting structure for allowing a front axle case to have sufficient strength for supporting a front wheel steering cylinder, while lightening of the front axle case and reducing the manufacturing cost.

The above object is fulfilled, according to this invention, by a steering cylinder mounting structure for a working vehicle with a steering cylinder disposed forwardly or rearwardly of a fi-ont axle case for steering front wheels, characterized in that an elongate cylinder mounting member having cylinder mounts for attaching the steering 1 cylinder is fixed to the front axle case to extend longitudinally of the front axle case so as to surround at least part of the front axle case.

With this construction, the front axle case has improved strength by a partial double construction formed with the cylinder mounting member. Thus, on the whole, the front axle case may have a reduced wall thickness to lighten the front axle case. At the same time, the front axle case is given sufficient strength for supporting the steering cylinder. The front axle case need not include a steering cylinder seating formed integral therewith. As a result, a simplified mold may be used to form the front axle case. The manufacturing process may be made easy and manufacturing cost reduced correspondingly. Moreover, since the cylinder mounting member is an elongate object fixed to the front axle case to extend longitudinally thereof, where the front axle case is connected to a body frame to be rollable about a fore and aft axis, the -cylinder mounting member may be: -used also as a restricting member for contacting the body frame or the like to limit the rolling of the front axle case to a predetermined range. This construction is simpler than where a separate restricting member is provided. In addition, the front axle case has improved durability compared with a case where the front axle is used also as the restricting member.

Consequently, while the front axle case is lightened, the manufacturing process simplified and manufacturing cost reduced, the front axle case is given sufficient strength to support the steering cylinder for the front wheels. Moreover, the rolling about the fore and aft axis of the front axle case may be restricted while simplifying the construction and improving the durability of the front axle case.

In a preferred embodiment of this invention, the cylinder mounting member is formed of a channel (profile) material having a C shaped section. In this case, a commercially available channel material is used as the cylinder mounting member. Thus, the 2 construction is simpler and assures higher strength than where a sheet metal material is bent to have a C-shaped section for use as the cylinder mounting member.

In the preferred embodiment of this invention, the cylinder mounting member formed of the channel material has a channel width for receiving the front axle case in a transverse direction, and a channel depth for receiving at least a half of the front axle case in the transverse direction. Since, in this construction, the cylinder mounting member surrounds at least a half of the front axle case from the transverse direction, there is less chance of foreign objects contacting the front axle case. The front axle case is reinforced with increased effect since the cylinder mounting member may be fixed to the front axle case with the latter pinched between opposite flanges of the cylinder mounting member.

As a preferred embodi--n.ent of this invention, covers may be attached to opposite, right and left ends of the cylinder mounting member for surrounding right and left piston rods of the steering cylinder. Then, the right and left piston rods of the steering cylinder are protected from contact by foreign objects, and an improved outward appearance may be provided compared with a case where the right and left piston rods are exposed to view.

In another preferred embodiment of this invention, a support bracket formed of sheet metal is fixed to a transversely intermediate position of the cylinder mounting member, a steering cylinder mounting end of the front axle case being supported by a body frame through the support bracket. In this case, there is no need to form a coupling integrally with the front axle case for connecting the steering cylinder mounting end thereof to the body frame. The shape of a mold for forming the front axle case may be simplified correspondingly to facilitate manufacture and reduce manufacturing cost.

3 Further, the support bracket may be placed to overlap the cylinder mounting member. This construction reinforces the front axle case with both the cylinder mounting member and support bracket.

In a further preferred embodiment of this invention, the cylinder mounting member supports a steering angle detecting mechanism for detecting a steering angle of the front wheels. This construction requires only a simplified mold for forming the front axle case simple, compared with a case of forming a support integrally with the front axle case for supporting the steering angle detecting mechanism. The shape of a mold for forming the front axle case may be simplified to facilitate manufacture and reduce manufacturing cost correspondingly.

The construction may be simplified and manufacturing cost reduced, compared with a case of providing a separate support member for supporting the steering angle detecting mech 1 Jn a further preferred embodiment of this invention, the steering angle detecting mechanism includes a steering angle detecting rod extending parallel to the steering cylinder and having opposite ends thereof connected to right and left piston rods of the steering cylinder, a steering angle of the front wheels being detected from an amount of movement of the steering angle detecting rod, the steering angle detecting rod being disposed between the front axle case and the cylinder mounting member. This construction reduces the chance of foreign objects contacting the steering angle detecting rod, and allows the position of the steering angle detecting mechanism to be changed as desired within a range of the length of the steering angle detecting rod.

In a further preferred embodiment of this invention, the steering cylinder is disposed between the front axle case and cylinder mounting member. This construction reduces the chance of foreign objects contacting the steering cylinder with increased effect. Where the cylinder mounting member is elongated to surround also the right and 4 left piston rods of the steering cylinder, a better outward appearance is provided than where the right and left piston rods are exposed to view.

To provide a still greater advantage, this invention proposes that the front axle case have a cylindrical body formed of sheet metal. That is, since the front axle case is sufficiently reinforced by the above- noted construction where the cylinder mounting member and support bracket are fixedly connected to the front axle case, it is possible for the front axle case to be a cylindrical body formed of sheet metal for a smaller wall thickness than a casting. As a result, the front axle case has a substantially reduced weight. In addition, the front axle case may be constructed without using a mold, which greatly contributes to facility of manufacture and a reduction of manufacturing cost.

Other features and advantages of this invention will be apparent from the following description of the embodiments to be taken with

15. reference to the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a side elevation of a tractor; Fig. 2 is a schematic side view of a transmission structure mounted in a transmission case; Fig. 3 is a view in cross section of a principal portion showing a construction around a front axle case; Fig. 4 is a view in vertical section of a principal portion showing the construction around the front axle case; Fig. 5 is a front view of a principal portion showing the construction around the front axle case; and Fig. 6 is a view in vertical section of a principal portion showing a construction around a front axle case in another embodiment.

DESCRIPTION OF THE PREFERRED EM130DIMENTS

Fig. 1 shows a side elevation of a tractor which is one example of working vehicles. This tractor includes an engine 1 mounted in a forward position of a vehicle body, a transmission case 2 connected to the rear of engine 1 and forming part of the vehicle body, a body frame 3 extending toward forwardly of engine 1, front wheels 4 disposed at opposite sides of the body frame 3, rear wheels 5 disposed at opposite sides of a rear portion of transmission case 2, a steering wheel 6 interlocked to the front wheels 4, and a driver's seat 7 disposed rearwardly of steering wheel 6.

As shown in Fig. 2, the transmission case 2 houses a main dutch 8 for connecting and disconnecting power transmitted from the engine 1, a hydrostatic stepless transmission 9 for steplessly changing the speed of power transmitted from the engine 1 through the main dutch 8, an auxiliary change speed device 10 for changing the power received from the hydrostatic stepless transmission 9 into three sp6eds, a rear differential 11 for distributing the power received from the auxiliary change speed device 10 to the right and left rear wheels 5 in a way to allow the right and left rear wheels 5 to rotate at different rates, a DT (dual transmission) clutch 12 tor connecting and disconnecting power transmission from the auxiliary change speed device 10 to the right and left front wheels 4, and a hydraulically operable front wheel accelerating device 13 for changing the power received from the auxiliary change speed device 10 through the DT dutch 12 into two speeds.

As shown in Figs. 2 through 5, the body frame 3 supports a front axle case 14 to be rollable about a fore and aft axis P1 under the body frame 3. Each front wheel 4 is connected to a lateral end of front axle case 14 at a -kingpin angle and to be steerable about an axis P2 of a kingpin 15, through a hub case 16 supported to be swingable about the aids P2. The front axle case 14 houses a front differential 18 for 6 distributing the power received from the front wheel accelerating device 13 through a transmission shaft 17 disposed on the fore and aft axis P1, to the right and left front wheels 4 in a way to allow the right and left front wheels 4 to rotate at different rates.

As shown in Figs. 3 through 5, the front axle case 14 includes a cylindrical body 14A formed of sheet metal to have a circular sectional shape, connecting flanges 14B formed of sheet metal and welded to opposite ends of cylindrical body 14A, and a rear boss 14C welded to a rear position of cylindrical body 14A and disposed on the fore and aft axisP1. The hub cases 16 are supported by fixed cases 19 bolted to the right and left connecting Ranges 14B, respectively. The rear boss 14C supports a forward end of transmission shaft 17. Thus, the front axle case 14 is lighter, easier to manufacture and less costly to manufacture than where the front axle case 14 is formed by casting.

The cylindrical body 14A of front axle -.case 14 has a cylinder mounting member 21 fixed and extending longitudinally of the front axle case 14 for supporting a hydraulically operable steering cylinder 20 for steering the right and left front wheels 4. The cylinder mounting member 21 is formed of a channel (profile) material having a C-shaped section. The channel material has a length almost corresponding to the total length of front axle case 14, with a web 2 1A defining the width of the channel substantially as large as the diameter of cylindrical body 14A, and opposite flanges 21B defining the depth of the channel substantiaRy as large as the radius of cylindrical body 14A. The web 2 1A has threaded bores formed in opposite end regions thereof to act as cylinder mounts 21a. Free ends of opposite flanges 21B are welded to the cylindrical body 14A, with the web 21A disposed at front, and the two flanges 2 1B holding the cylindrical body 14A in between. Thus, the cylinder mounting member 2 1, while reinforcing the front axle case 14, allows the steering cylinder 20 to be mounted forwardly of and 7 parallel to the front axle case 14.

The steering cylinder 20 is a double-acting, two-rod type cylinder.

Supply/drain ports 20a formed at opposite ends of a cylinder tube 20A are connected through hydraulic hoses 23 to a control valve 22 which controls a hydraulic oil flow to the steering cylinder 20 in response to an operation of steering wheel 6. Right and left piston rods 20B are connected through universal joints 24 and ball joints 26 to knuckle arms 16A formed integral with the hub cases 16, respectively. Thus, the control valve 22 interlocked to the operation of steering wheel 6 is operable to steer the right and left front wheels 4 to a steering angle corresponding to an amount of operation of steering wheel 6. The steering operation is effected without any jamming due to the kingpin angle occurring between the right and left piston rods 20B and knuckle arms 16A. The right and left piston rods 20B, universal joints 24 and ball joints 26 connected through meshing (screws). z A support bracket 27 formed of sheet metal is attached to an intermediate position transversely of cylinder mounting member 21.

The support bracket 27 allows a front end of front axle case 14 opposed to the steering cylinder 20 to be supported by the body frame 3. The support bracket 27 is bent to be approximately channel-shaped in side view, and has a transverse length substantially corresponding to a length between the right and left supply/drain ports 20a in the steering cylinder 20. The support bracket 27 is welded to the two flanges 21B of cylinder mounting member 21 so as to surround the cylinder tube 20A of steering cylinder 20, with upper and lower ends placed over the flanges 21B of cylinder mounting member 21. Thus, the support bracket 27 protects the cylinder tube 20A of steering cylinder 20 from contact by foreign objects, and reinforces the front axle case 14 with increased effect, without hampering attachment and detachment of hydraulic hoses 23 to/from the supply/drain ports 20a in the steering 8 cylinder 20.

The support bracket 27 has a front boss 27A welded to a forward end thereof and disposed on the fore and aft axis P1. This front boss 27A and the rear boss 14C of front axle case 14 are supported by the body frame 3 to be rotatable relative thereto, whereby the front axle case 14 is supported by the body frame 3 to be rollable about the fore and aft axis P1. The elongate cylinder mounting member 21 attached to the front axle case 14 acts also as a restrictor for abutting with right and left frames 3A of body frame 3 extending in the fore and aft direction (see Fig. 5), to limit the rolling of front axle case 14 within a predetermined range. This construction is simpler than where an additional restrictor or restrictors are provided. Deformation or damage of the front axle case 14 may also be avoided which could occur where the front axle case 14 is used as a restricting member.

The support bracket 27 has a guide member 28.-having a channel shaped section fixed to an upper surface thereof and extending parallel to the steering cylinder 20. The guide member 28 receives a rod 29 extending parallel to the steering cylinder 20. The rod 29 is connected at opposite ends thereof to outward ends of right and left piston rods 20B of steering cylinder 20 through connecting plates 30 to be movable with the piston rods 20B. Thus, the guide member 28, rod 29 and right and left connecting plates 30 constitute a rotation stopper mechanism A for inhibiting rotation of the right and left piston rods 20B about an axis P3 within a range permitted by the universal joints 24 and ball joints 26, This construction effectively precludes the possibility of meshed portions 3 1 of right and left piston rods 20B, universal joints 24 and ball joints 26 becoming loose as a result of rotation about the axis P3 of right and left piston rods 20B.

The cylinder mounting member 21 has a plurality of threaded bores 2 lb formed in opposite, right and left ends thereof to act as cover 9 mounts for bolting covers 32 formed of sheet metal and curved to surround the right and left piston rods 20B of steering cylinder 20 and opposite, right and left ends of rod 29 exposed laterally of the body frame 3. With the covers 32 attached to these cover mounts 2 1b, the opposite ends of right and left piston rods 20B and rod 29 are protected from contact by foreign objects. In addition, a better outward appearance is provided than where the opposite ends of right and left piston rods 20B and rod 29 are exposed to view.

The support bracket 27 supports a steering angle detecting mechanism B mounted thereon for detecting a steering angle of front wheels 4 from an amount of movement of rod 29. Specifically, the steering angle detecting mechanism B includes the rod 29 acting as a steering angle detecting rod movable with the right and left piston rods 20B of steering cylinder 20 which steer the front wheels 4, a support element 33 having a channel-shaped section and c6nnected to an upper surface of support bracket 27 between the right and left frames 3A of body frame 3 extending in the fore and aft direction, a swing arm 34 supported by and extending forward from a lower portion of support element 33 to be swingable about vertical aids P4, a pin 35 erected on the rod 29 and penetrating a slot 34A formed in a free end region of swing arm 34 to extend in the fore and aft direction, a U-shaped control element 36 erected in a fore and aft intermediate position of swing arm 34, and a rotary potentiometer 37, which is one example of detecting devices, fixed to an upper position of support element 33 with a detecting arm 37A of the neutral return type engaged with the control element 36. The rod 29 moves in response to an operation of steering cylinder 20 interlocked to the operation of steering wheel 6. When a movement exceeding a predetermined amount causes the control element 36 on the swing arm 34 to displace the detecting arm 37A, the potentiometer 37 detects this displacement. In this way, the front wheels 4 being steered more than a predetermined angle is detected as when the tractor makes a small turn near a ridge in a field. Since the rod 29 of the rotation stopper mechanism A is identical with the steering angle detecting rod 29 of steering angle detecting mechanism B, the construction is simpler and less costly to manufacture than where separate rods are provided. Further, the swing arm 34, potentiometer 37 and so on are arranged above the axle case 14 and support bracket 27 and between the right and left frames 3A of body frame 3 extending in the fore and aft direction. These components are thus effectively protected from adhesion of soil or the like splashed upward by the front wheels 4 and contact by foreign objects.

As shown in Fig. 4, the potentiometer 371 of steering angle detecting mechanism B inputs results of detection to a controller 38 mounted on the vehicle body. When the front wheels 4 are found to be steered more than the predetermined angle. based on the input from the potentiometer 37, the controller 38 controls an electromagnetic selector valve 39 for switching the flow of hydraulic oil to the front wheel accelerating device 13 to provide an accelerating state for driving the front wheels 4 at about twice the speed of rear wheels 5. When the front wheels 4 are found not to be steered more than the predetermined angle based on the input from the potentiometer 37, the controller 38 controls the electromagnetic selector valve 39 to provide an equal speed state for driving the front wheels 4 at substantially the same speed as the rear wheels 5. Such front wheel accelerating controls allow the tractor to make turns near the ridges of a field smoothly without roughening the field.

Other embodiments of this invention will be described briefly hereinafter.

(1) The working vehicle may a rice planting machine or a direct seed planting machine as long as the steering cylinder 20 is disposed forwardly or rearwardly of the front axle case 14.

(2) The front axle case 14 may have a cylindrical body 14A formed of sheet metal to have a polygonal sectional shape such as square or hexagonal. The cylindrical body 14A may be formed by casting.

(3) The cylinder mounting member 21 may be attached to the front axle case 14 from behind to place the steering cylinder 20 rearwardly of the front axle case 14. A cylinder mounting member 21 with threaded bores formed in opposite end regions of Ranges 2 IB to act as cylinder mounts 21a may be attached to the front axle case 14 so as to fit on the latter vertically, to place the steering cylinder 20 forwardly or rearwardly of the front axle case 14.

(4) The cylinder mounting member 21 may include stud bolts to act as cylinder mounts 2 Ia.

(5) The cyl-inder mounting member 21 may be-,-formed of a channel material with the width of flanges 21B larger than the radius of front axle case 14, or an angle material having an L-shaped sectional shape.

(6) The steering cylinder 20 may be attached to the support bracket 27, the cylinder mounting member 21 acting only as a reinforcing member for the front axle case 14.

(7) As shown in Fig. 6, the support bracket 27 may be omitted, with the cylinder mounting member 21 used to perform the functions of support bracket 27. That is, the cylinder mounting members 21 is fixed to the front axle case 14, with the steering cylinder 20 attached to the cylinder mounting member 21 and disposed between the front axle case 14 and cylinder mounting member 21. This effectively simplifies the construction and reduces manufacturing cost. In this construction, the guide member 28 and rod 29 may be disposed between the front axle case 14 and cylinder mounting member 21. The guide member 28 and 12 rod 29 may then by protected from adhesion of soil and the like splashed upward by the front wheel 4 and contact by foreign objects with increased effect. Further, in this construction, as illustrated, the guide member 28 may be fixed to the front axle case 14 to extend longitudinally thereof to reinforce the front axle case 14 also with the guide member 28.

(8) It is also advantageous where the cylinder mounting member 21 and support bracket 27 have a right and left length substantially corresponding to the total length of front axle case 14. Particularly, the support bracket 27 may have an increased length to perform the function of covers 32, to simplify the construction and reduce manufacturing cost still further.

(9) This invention is applicable also to a front axle case 14 fixedly supported by the body frame 3 not to be rollable.

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Claims

1. A steering cylinder mounting structure for a working vehicle with a steering cylinder (20) disposed forwardly or rearwardly of a front axle case (14) for steering front wheels (4), characterized in that an elongate cylinder mounting member (21) having cylinder mounts (21a) for attaching said steering cylinder is fixed to said front axle case to extend longitudinally of said front axle case so as to surround at least part of said front axle case.

2. A mounting structure as defined in claim 1, characterized in that said cylinder mounting member (21) is formed of a channel (profile) material having a C-shaped section.

3. A mounting structure as defined in claim 2, characterized in that said cylinder mounting member (21) formed of said channel material has a channel width for receiving said front axle case in a transverse direction, and a channel depth for receiving at least a half of said front axle case in the transverse direction.

4. A mounting structure as defined in claim 1, characterized in that said cylinder mounting member (21) has cover mounts for attaching covers (32) for surrounding right and left piston rods of said steering cylinder.

5. A mounting structure as defined in claim 1, characterized in that a support bracket (27) formed of sheet metal is fixed to a transversely intermediate position of said cylinder mounting member (2 1), a steering cylinder mounting end of said front axle case being supported by a body frame (3) through said support bracket.

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6. A mounting structure as defined in claim 1, characterized in that said support bracket (27) is placed to overlap said cylinder mounting member (2 1).

7. A mounting structure as defined in claim 1, characterized in that said cylinder mounting member (2 1) supports a steering angle detecting mechanism (B) for detecting a steering angle of said front wheels.

8. A mounting structure as defined in claim 7, characterized in that said steering angle detecting mechanism (B) includes a steering angle detecting rod (29) extending parallel to said steering cylinder (20) and having opposite ends thereof connected to right and left piston rods (20B) of said steering cylinder, a steering angle of said front wheels being detected from an amount of movement of said steering angle detecting rod (29), said steering angle detecting rod being disposed between said f-ront axle case (14) and said cylinder mounting member (21).

9. A mounting structure as defined in claim 1, characterized in that said steering cylinder (20) is disposed between said front axle case (14) and said cylinder mounting member (2 1).

10. A mounting structure as defined in any one of claims 1 to 9, characterized in that said front axle case (14) has a cylindrical body formed of sheet metal.

11. A steering cylinder mounting structure substantially as hereinbefore described with reference to the accompanying drawings