Motor grader

A circle rotator of a motor grader includes a worm, a worm wheel and a shaft. The worm wheel has an inner peripheral portion, an outer peripheral portion enclosing the inner peripheral portion from outside, and a plurality of first clutch discs to be spline-coupled to the inner peripheral surface of the inner peripheral portion. The inner peripheral portion is made of a material harder than a material of which the outer peripheral portion is made.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a U.S. National stage application of International Application No. PCT/JP2013/066607, filed on Jun. 17, 2013.

BACKGROUND

Field of the Invention

The present invention relates to a motor grader equipped with a blade pivoting device.

Background Information

Motor graders include a frame, a drawbar supported beneath the frame capable of pitching up and down, a blade pivoting device supported by the drawbar, and a blade supported by the blade pivoting device (e.g., see Japan Laid-open Patent Application Publication No. 2004-190232). The blade pivoting device includes a circle for supporting the blade and a circle rotator for driving and rotating the circle. The circle rotator is disposed on the drawbar.

SUMMARY

Since the circle rotator is disposed on the drawbar, it is required to extend the interval between the circle rotator and the frame for extending the range of rising motion of the blade, and hence, it is demanded to lower the height of the circle rotator.

The present invention has been produced in view of the aforementioned situation, and it is an object of the present invention to provide a motor grader in which the height of a circle rotator can be lowered.

A motor grader according to a first aspect of the present invention includes a frame, a drawbar, a blade pivoting device and a blade. The drawbar is disposed beneath the frame and is supported by the frame to be capable of pitching up and down. The blade pivoting device is supported by the drawbar. The blade is supported by the blade pivoting device. The blade pivoting device includes a circle, which supports the blade and is rotatably attached to the drawbar, and a circle rotator configured to rotary drive the circle. The circle rotator includes a worm, a worm wheel meshed with the worm, and a shaft inserted through the worm wheel. The worm wheel includes an inner peripheral portion enclosing the shaft, an outer peripheral portion, which encloses the inner peripheral portion from outside and is meshed with the worm, and a plurality of first clutch discs spline-coupled to an inner peripheral surface of the inner peripheral portion. The shaft includes a shaft body and a plurality of second clutch discs that are spline-coupled to an outer peripheral surface of the shaft body and each of which is interposed between the plural first clutch discs. The inner peripheral portion is made of a material harder than a material of which the outer peripheral portion is made.

According to the motor grader of the first aspect of the present invention, the inner peripheral portion is made of the hard material. Hence, surface pressure resistance can be enhanced for contact surfaces of the first clutch discs and the inner peripheral portion to which the first clutch discs are spline-coupled. Therefore, the first clutch discs can be reduced in thickness and in number. Hence, the circle rotator can be reduced in entire height. As a result, the interval between the circle rotator and the frame can be extended, and hence, the range of rising motion of the blade can be extended.

A motor grader according to a second aspect of the present invention relates to the motor grader according to the first aspect, and wherein the outer peripheral portion has an outer peripheral portion body enclosing the inner peripheral portion from outside and a thrust receiver that inwardly extends from the outer peripheral portion body and is disposed beneath the inner peripheral portion. The shaft has a contact portion that outwardly extends from the shaft body and is disposed beneath the thrust receiver.

According to the motor grader of the second aspect of the present invention, the thrust receiver made of the soft material is contacted to the contact portion to be capable of receiving a thrust load. Hence, galling and adhesion of the contact portion to the thrust receiver can be inhibited.

A motor grader according to a third aspect of the present invention relates to the motor grader according to the first or second aspect, and wherein the inner peripheral portion has an inner peripheral portion body having an annular plate shape and a bulging part outwardly and downwardly bulging from the inner peripheral portion body. The outer peripheral portion has a first part covering an upper end of the bulging part from above and a second part covering a lower end of the bulging part from inside.

According to the motor grader of the third aspect of the present invention, when the inner peripheral portion is fixed to the interior of a mold and then a melting material is poured into the mold, a gap can be inhibited from being produced in the surrounding of the bulging part.

A motor grader according to a fourth aspect of the present invention relates to the motor grader according to the third aspect, and wherein on a cross-section of the inner peripheral portion taken along a plane on which a center axis of the shaft passes, a first outer edge line indicating an outer peripheral edge of the inner peripheral portion body and a second outer edge line indicating a lower edge of the inner peripheral portion body are roughly symmetric to each other with respect to a reference line passing through a middle of the first outer edge line and the second outer edge line. A width of the inner peripheral portion body along a direction orthogonal to the reference line gradually decreases toward the bulging part A width of the bulging part along the direction orthogonal to the reference line gradually increases oppositely to the inner peripheral portion body.

According to the motor grader of the fourth aspect of the present invention, a binding force can be enhanced between the inner peripheral portion and the outer peripheral portion by narrowing the inner peripheral portion at a boundary between the inner peripheral portion body and the bulging part.

A motor grader according to a fifth aspect of the present invention relates to the motor grader according to any of the first to fourth aspects, and wherein the inner peripheral portion is made of cast iron.

A motor grader according to a sixth aspect of the present invention relates to the motor grader according to any of the first to fifth aspects, and wherein the outer peripheral portion is made of copper-aluminum alloy.

According to the exemplary embodiments of the present invention, it is possible to provide a motor grader in which the height of a circle rotator can be lowered.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Entire Construction of Motor Grader100

FIG. 1is a side view of an entire construction of a motor grader100.FIG. 2is an enlarged perspective view of a front part of the motor grader100.FIG. 3is a perspective view of a blade pivoting device65seen in a direction X inFIG. 2. It should be noted that in the following explanation, “up”, “down”, “left”, “right”, “front” and “rear” are terms defined on the basis of a direction seen from an operator seated on an operator seat.

The motor grader100includes a frame10, front wheels20, rear wheels30, a cab40, a drawbar50, a blade60, the blade pivoting device65, a lifter guide70, a lifter bracket75, a pair of lift cylinders80, and a shift cylinder90.

The frame10is composed of a front frame11and a rear frame12. The front frame11supports the drawbar50at the front end thereof. The rear frame12supports an engine, a hydraulic pump and so forth (not shown in the drawings).

The front wheels20are attached to the front end of the front frame11. The rear wheels30are attached to the rear frame12. The cab40is disposed on the front frame11. The cab40may be disposed on the rear frame12.

The drawbar50is disposed beneath the front frame11. The drawbar50is supported by the front end of the front frame11to be capable of pitching up and down. The blade60is supported by the blade pivoting device65.

The blade pivoting device65is supported by the rear end of the drawbar50. The blade pivoting device65includes a circle65a, a circle rotator65band a pinion65c. The circle65ais rotatably supported by the rear end of the drawbar50. The circle65asupports the blade60. The circle rotator65bis disposed inside the circle65a. The circle rotator65bis configured to rotary drive the circle65aby hydraulic pressure. Specifically, as shown inFIG. 3, the pinion65ccoupled to the lower end of the circle rotator65bis meshed with internal teeth65T of the circle65a. Thus, the circle65ais configured to be rotated in conjunction with rotation of the pinion65c. The construction of the circle rotator65bwill be described below.

It should be noted in the present exemplary embodiment, as shown inFIG. 1, the upper end of the blade pivoting device65upwardly protrudes from the drawbar50, but may be designed not to protrude from the drawbar50.

The lifter guide70is fixed to the frame10. The lifter guide70has an annular shape. The lifter bracket75is a frame enclosing the lifter guide70. The pair of lift cylinders80and the shift cylinder90are coupled to the lifter bracket75. The pair of lift cylinders80is coupled to the drawbar50and the lifter bracket75. When the pair of lift cylinders80is extended and contracted, the drawbar50can be moved up and down. The shift cylinder90is coupled to the drawbar50and the lifter bracket75. When the shift cylinder90is extended and contracted, the drawbar50can be moved right and left.

Construction of Circle Rotator65b

FIG. 4is a cross-sectional view of the circle rotator65b.FIG. 5is a cross-sectional view ofFIG. 4taken along line A-A.FIG. 4shows a cross section taken along a vertical direction, whereasFIG. 5shows a cross section taken along a horizontal direction. It should be noted that in the following explanation, “inward” and “outward” are terms defined on the basis of a center axis AX of a shaft140.

The circle rotator65bincludes a chassis110, a worm120, a worm wheel130and the shaft140.

The chassis110accommodates the worm120and the worm wheel130. The worm120is a cylindrical member to be disposed along the horizontal direction. The worm120is rotary driven by hydraulic pressure. The worm120has screw threads120aon the outer peripheral surface thereof.

The worm wheel130has an inner peripheral portion131, an outer peripheral portion132and a plurality of first clutch discs133.

The inner peripheral portion131encloses the shaft140. The inner peripheral portion131is made of a material harder than a material of which the outer peripheral portion132is made. The material of which the inner peripheral portion131is made is preferably FCD450 (Ferrum Casting Ductile: the hardness thereof is, for instance, HB200), but is not limited to this.

The inner peripheral portion131has an inner peripheral portion body131aand a plurality of bulging parts131b. The inner peripheral portion body131ahas an annular plate shape. The plural bulging parts131boutwardly and downwardly bulge from the inner peripheral portion body131atoward the interior of the outer peripheral portion132. With the construction, the inner peripheral portion131is firmly coupled to the outer peripheral portion132. Accordingly, radial load resistance about the center axis AX is enhanced. It should be noted that in the present exemplary embodiment, twelve bulging parts131bare provided, but the number and the size of the bulging parts131bcan be arbitrarily changed.

The outer peripheral portion132encloses the inner peripheral portion131from outside. The outer peripheral portion132is integrally formed with the inner peripheral portion131by casting. Specifically, the outer peripheral portion132is formed by fixing the inner peripheral portion131to the interior of a mold and then pouring a melting material into the mold. The outer peripheral portion132is made of the material softer than the material of which the inner peripheral portion131is made. The material of which the outer peripheral portion132is made is preferably copper-aluminum alloy (the hardness thereof is, for instance, HB160), but is not limited to this.

The outer peripheral portion132has an outer peripheral portion body132aand a thrust receiver132b. The outer peripheral portion body132ahas an annular shape. The thrust receiver132binwardly extends from the lower end of the outer peripheral portion body132a. The thrust receiver132bcovers the bulging parts131bfrom below. The thrust receiver132bhas an annular plate shape. The thrust receiver132bis disposed beneath the inner peripheral portion131.

An axial thrust load along the center axis AX of the shaft140is receivable by the thrust receiver132b. The thrust receiver132bis contacted to a contact portion140bof the shaft140to be described. The thrust receiver132bis made of the soft material such as copper-aluminum alloy, and hence, galling of the thrust receiver132bagainst the contact portion140bis inhibited.

The plural first clutch discs133respectively have an annular plate shape. The plural first clutch discs133are spline-coupled to the inner peripheral surface of the inner peripheral portion131(specifically, the inner peripheral portion body131a). The plural first clutch discs133are disposed at predetermined intervals in the axial direction. The first clutch discs133are interposed among second clutch discs143to be described. The first clutch discs133are firmly united to the second clutch discs143by a friction force generated therebetween. Moreover, the first clutch discs133and the second clutch discs143are pressed by an urging member (disc spring)134. When a radial load of a predetermined value or greater (a resistive force acting on the blade60) acts on the shaft140, the worm wheel130is protected by sliding the first clutch discs133against the second clutch discs143. In the present exemplary embodiment, eight first clutch discs133are provided. However, the number, the thickness and so forth of the first clutch discs133can be arbitrarily changed.

The shaft140is inserted through the worm wheel130. The shaft140is supported by the chassis110to be rotatable about the center axis AX. The shaft140is made of a material harder than the material of which the inner peripheral portion131is made. The material of which the shaft140is made is preferably a steel material, but is not limited to this. The shaft140includes a shaft body141, the contact portion142and the plural second clutch discs143.

The shaft body141has a columnar shape and extends in the axial direction. The pinion65c(seeFIG. 3) is coupled to the lower end of the shaft body141. The contact portion142outwardly extends from the shaft body141. The contact portion142has an annular plate shape. The contact portion142is disposed beneath the thrust receiver132bof the outer peripheral portion132. The contact portion142is contacted to the lower surface of the thrust receiver132b. The plural second clutch discs143respectively have an annular plate shape. The plural second clutch discs143are spline-coupled to the outer peripheral surface of the shaft body141. The plural second clutch discs143are disposed at predetermined intervals in the axial direction. The second clutch discs143are interposed among the first clutch discs133. In the present exemplary embodiment, seven second clutch discs143are provided. However, the number, the thickness and so forth of the second clutch discs143can be arbitrarily changed.

Detailed Construction of Outer Peripheral Portion132

FIG. 6is a cross-sectional view of the inner peripheral portion131and the outer peripheral portion132taken along a plane on which the center axis AX of the shaft140passes.

As shown inFIG. 6, the outer peripheral portion132has a first part201and a second part202.

The first part201covers the upper ends of the bulging parts131bof the inner peripheral portion131from above. The first part201inwardly extends from the upper end of the outer peripheral portion body132a. The second part202covers the lower ends of the bulging parts131bof the inner peripheral portion131from inside. The second part202is formed by partially protruding the thrust receiver132bupward.

The inner peripheral portion131has a first outer edge line H1indicating the outer peripheral edge of the inner peripheral portion body131aand a second outer edge line H2indicating the lower edge of the inner peripheral portion body131a. The first outer edge line H1and the second outer edge line H2are roughly symmetric to each other with respect to a reference line131S that passes through the middle of the first outer edge line H1and the second outer edge line H2.

A width W1of the inner peripheral portion body131aalong a direction orthogonal to the reference line131S gradually decreases toward the bulging parts131b. On the other hand, a width W2of each bulging part131balong the direction orthogonal to the reference line131S gradually increases oppositely to the inner peripheral portion body131a, and thereafter, gradually decreases further oppositely to the inner peripheral portion body131a.

The circle rotator65bof the motor grader100includes the worm120, the worm wheel130and the shaft140. The worm wheel130includes the inner peripheral portion131, the outer peripheral portion132that encloses the inner peripheral portion131from outside, and the plural first clutch discs133that are spline-coupled to the inner peripheral surface of the inner peripheral portion131. The inner peripheral portion131is made of the material harder than the material of which the outer peripheral portion132is made.

Thus, the inner peripheral portion131is made of the hard material, and hence, surface pressure resistance can be enhanced for the contact surfaces of the first clutch discs and the inner peripheral portion to which the first clutch discs are spline-coupled. Therefore, the first clutch discs133can be reduced in thickness and in number. Hence, the circle rotator65bcan be reduced in entire height. As a result, the interval between the circle rotator65band the frame10can be extended, and thus, the range of rising motion of the blade90can be extended.

The outer peripheral portion132has the thrust receiver132bto be disposed beneath the inner peripheral portion131, whereas the shaft140has the contact portion142to be disposed beneath the thrust receiver132b.

Therefore, the thrust receiver132bmade of the soft material is contacted to the contact portion142so as to be capable of receiving a thrust load. Hence, galling and adhesion of the contact portion142to the thrust receiver132bcan be inhibited. As a result, the circle rotator65bcan be smoothly driven.

The outer peripheral portion132has the first part201and the second part202. The first part201covers the upper ends of the bulging parts131bfrom above. The second part202covers the lower ends of the bulging parts131bfrom inside.

Therefore, when the inner peripheral portion132is fixed to the interior of the mold and then the melting material is poured into the mold, a gap can be inhibited from being produced in the surrounding of the bulging parts131b.

The width W1of the inner peripheral portion body131aalong the direction orthogonal to the reference line131S gradually decreases toward the bulging parts131b. The width W2of each bulging part131balong the direction orthogonal to the reference line131S gradually increases oppositely to the inner peripheral portion body131a.

Thus, a binding force can be enhanced between the inner peripheral portion131and the outer peripheral portion132by narrowing the inner peripheral portion131at a boundary between the inner peripheral portion body131aand the bulging parts131b.

According to the present invention, the height of the circle rotator can be lowered. Hence, the present invention is useful in the field of motor graders.