Axle driving apparatus - Patent Review 5473964

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BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an axle driving apparatus with a hydro-static-transmission used as a driving apparatus for a vehicle such as a light tractor.

2. Related Art

Conventionally, an axle driving apparatus, which vertically divides a casing thereof and journals axles at the divided surfaces and drives the axles by a hydro-static-transmission attached to the casing, is well known as disclosed in, for example, the Japanese Utility Model Publication Gazette No. Sho 62-44198 and the Japanese Patent Laid-Open Gazette Sho 62-101945, filed by the same applicant.

In the conventional apparatus, however, the hydro-static-transmission, separate from the axle driving apparatus, is fixed to the outside thereof in a manner of being exposed, whereby the apparatus is large-sized as a whole and larger in the gross weight. Also, it is required for driving the horizontally disposed axles by a motor shaft of a hydraulic motor vertically disposed at the exterior, to interpose bevel gears in a drive system for both the motor shaft and axles.

SUMMARY OF THE INVENTION

An object of the invention is to provide an axle driving apparatus which contains the hydraulic motor and a hydraulic pump 8 the hydro-static-transmission in a transmission casing of the axle driving apparatus, and a center section for connecting the hydraulic motor and hydraulic pump is disposed in the transmission casing, the center section being fixed to the butt joint surface of upper and lower sections of the casing.

The center section is formed in a L-like shape when viewed in section and an oil passage from the hydraulic pump to the hydraulic motor is bent at a right angle to thereby extend the motor shaft in parallel to the driven axle. Hence, instead of conventional bevel gears used to turn the rotation direction, the oil passage in the center section is used to turn the power transmitting direction.

In a case where the center section is fixed to the butt joint surfaces of the half casings, when the half casings are fixedly jointed directly with a center section 6 aluminum die casting by use of four bolts, the center section may be distorted, thereby using three tightening bolts.

The above and further objects and novel features of the invention will more fully appear from the following derailed description when the same is read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of a light tractor attached with an axle driving apparatus of the invention.

FIG. 2 is a sectional front view of the axle driving apparatus.

FIG. 3 is a sectional view taken on the line 3--3 in FIG. 2, in which an upper half casing is removed.

FIG. 4 is a sectional view taken on the line 4--4 in FIG. 3.

FIG. 5 is a sectional view taken on the line 5--5 in FIG. 3.

FIG. 6 is a sectional view taken on the line 6--6 in FIG. 3.

FIG. 7 is a sectional front view of a modified embodiment of the axle driving apparatus of the invention, in which the arrangement of the check valves is changed.

FIG. 8 is a plan view of the same.

FIG. 9 is a sectional view taken on the line 9--9 in FIG. 7.

FIG. 10 is a sectional view taken on the line 10--10 in FIG. 7.

FIG. 11 is a perspective exploded view of the axle driving apparatus of the invention.

FIG. 12 is a sectional front view of another modified embodiment of the invention, in which a center section is fixed to the inner surface of the bottom wall of a lower half casing.

FIG. 13 is a plan view of the FIG. 12 embodiment.

FIG. 14 is a sectional front view of a further modified embodiment of the invention, in which a center section has three bolt-bores into which three fixing bolts are inserted so that the center section is fixed therethrough to the upper half casing.

FIG. 15 is a plan view of the FIG. 14 embodiment.

FIG. 16 is a section plan view of the center section.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1, a light tractor loading thereon an engine E having a vertical crank shaft is shown.

A pulley is fixed to the vertical crank shaft of the engine so that a driving power is transmitted from the pulley through a belt to a pulley fixed to an input shaft, pump shaft 4 of a hydraulic pump P, projecting upwardly from an axle driving apparatus of the invention.

The tractor is provided at the front or under the body with a mower R or R' to thereby mow a lawn.

The present invention relates to an axle driving apparatus or transaxle and is specifically described herein as driving axles 13 of the tractor.

Next, the axle driving apparatus will be detailed of its construction in accordance with FIGS. 1-6.

A transmission casing of the axle driving apparatus is formed in upper and lower half casings 1 and 2, both the casings being joined along a junction surface 2z (see FIGS. 3 and 11) to form one closed-type transmission casing. As shown in FIGS. 1 and 2, the junction surface is horizontally disposed when the casing is fixed to a vehicle.

Between the butt joint junction surfaces of the upper and lower half casings 1 and 2 are held bearings in parallel thereto, for the axles 13 and a counter shaft 24; and a beating 34 for one end of a motor shaft 5. As shown in FIGS. 2-5, the longitudinal axes (5x, 13x, and 24x , respectively) of the motor output shaft 5, axles 13, and countershaft 24 are parallel to the junction surface, and are disposed within a single plane, more particularly, the plane defined by the junction surface.

At the lower surface of the upper half casing 1 is formed a mounting surface so that a center section 3 fixedly supporting the hydraulic pump P and a hydraulic motor M is mountable to the mounting surface through bolts 39 inserted into bolt holes 3g from below.

In the state where the center section 3, fixing thereto the hydraulic motor M and hydraulic pump P, is mounted to the lower surface of the upper half casing 1, the lower half casing 2 is jointed from below with the lower surface of the upper half casing 1 in a manner of closing the lower half casing 2 and bolts are used to connect both the upper and lower half casings 1 and 2.

The upper and lower half casings 1 and 2 are formed by aluminum die casting, whereby parts subjected to mechanical processing are reduced to lower the manufacturing cost

The HST or hydrostatic type transmission stored within the axle driving apparatus comprises the hydraulic pump P, center section 3 and hydraulic motor M. The center section 3 is formed, so that a pump mounting surface 3d formed on the center section 3 is parallel to the axles 13 and a motor mounting surface 3e formed on the center section 3 is perpendicular to the axles 13.

Pairs of crescent-shaped oil passages 3a' and 3b' and 3a" and 3b" are formed at the pump mounting surface 3d and motor mounting surface 3e, the pair of crescent-shaped oil passages 3a" and 3b" at the motor mounting surface 3e and pair of crescent-shaped oil passages 3a' and 3b' at the pump mounting surface 3d being connected to two oil passages 3a and 3b to constitute a closed circuit fluid path.

A cylinder block 10 for the hydraulic pump P is rotatably mounted on the pump mounting surface 3d and pistons 12 are inserted vertically slidably into a plurality of piston holes at the cylinder block 10 respectively.

When the pump shaft 4, supported by a bearing 31 at the upper half casing 1 and a spherical bush 32 at the pump mounting surface 3d, is rotated, the cylinder block 10 and pistons 12 rotate.

A thrust bearing 15 abutting against the upper end of each piston is changed at an angle by a swash plate 9, so that the discharge rate and discharge direction of the hydraulic pump P are changed to supply the discharged pressure oil from the oil passages 3a' and 3b' at the center section 3 to the hydraulic motor M through the oil passages 3a and 3b.

As shown in FIG. 4, the swash plate 9 is changeable of its angle through a positioning plate 6a in association with rotation of a speed change lever shaft 6, a detent unit 20 for holding the neutral position of the speed change lever shaft 6 being constituted in the upper half casing 1.

The detent unit 20 is fitted into a recess 6b at the positioning plate 6a, thereby enabling the neutral position to be ensured.

As shown in