An all-wheel-drive vehicle in which flexibility in setting the diameter of a driven gear is increased. In an all-wheel-drive vehicle in which an engine drives a rear wheel and also drives a hydraulic pump, and oil pressure generated by the hydraulic pump is supplied to a hydraulic motor for driving a front wheel. A front wheel hub provided on the front wheel is formed into a cup-shaped hub provided with a recess portion covered by a cover. The hydraulic motor is supported by the cover. A drive gear is provided on an output shaft of the hydraulic motor and a driven gear is provided in the recess portion of the hub with the driven gear being provided on the side of an axle.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority under 35 USC 119 to Japanese Patent Application No. 2005-086113 filed on Mar. 24, 2005 the entire contents of which are hereby incorporated by reference.

FIELD OF THE INVENTION

The present invention relates to an all-wheel-drive motorcycle in which an engine drives a rear wheel and also drives a hydraulic pump, and oil pressure generated by the hydraulic pump is supplied to a hydraulic motor for driving a front wheel.

DESCRIPTION OF BACKGROUND ART

Normally, in a motorcycle, only a rear wheel is driven via a chain or the like from an output shaft of an engine. Thus, a front wheel together with the rear wheel are propelled for traveling on rough-terrain or snow in the related art.

An all-wheel-drive motorcycle in which a rear wheel is driven by an engine and a front wheel is driven by a hydraulic motor is proposed, for example, in JP-A-2000-229596, see FIG. 10.

FIG. 10 of JP-A-2000-229596 is a cross-sectional view of a front wheel hub 41, note that the following reference numerals are used in JP-A-2000-229596, that includes a boss 41b for penetrating an axle formed integrally at an axial center portion of a bottom portion 41a with a double-row of ball bearings 61 for rotatably supporting the boss 41b. An internal gear 64 is fixed to a boundary section between the bottom portion 41a and a cylindrical portion 41c of the hub 41. An output gear 65 (hereinafter referred to as the drive gear 65) of a hydraulic motor 7 is engaged with the internal gear 64 (hereinafter referred to as the driven gear 64) so that the hub 41 is driven by the hydraulic motor 7.

Since the driven gear 64 is provided on the inner periphery of the hub 41, the diameter of the driven gear 64 can only be set to a diameter larger than that of the drive gear 65. Thus, the driven gear 64 has little flexibility in setting the diameter thereof.

SUMMARY AND OBJECTS OF THE INVENTION

Accordingly, an object of an embodiment of the present invention is to provide an all-wheel-drive motorcycle for improving the flexibility in setting the diameter of a driven gear.

It is an object of an embodiment of the present invention to provide an all-wheel-drive motorcycle in which an engine drives a rear wheel and also drives a hydraulic pump. Oil pressure generated by the hydraulic pump is supplied to a hydraulic motor for driving a front wheel. A front wheel hub is provided on the front wheel and is formed into a cup-shaped hub provided with a recess portion, the recess portion of the hub is covered by a cover with the hydraulic motor being supported by the cover. A drive gear is provided on an output shaft of the hydraulic motor, and a driven gear is provided in the recess portion of the hub wherein the driven gear is provided on the side of an axle.

According to an embodiment of the present invention the diameter of the drive gear is set to be larger than the diameter of the driven gear.

According to an embodiment of the present invention the output shaft of the hydraulic motor is arranged so as to be inclined with respect to the axle by employing bevel gears as the drive gear and the driven gear. The bevel gears are arranged so that smaller diameter portions face toward the inside of the recess portion.

According to an embodiment of the present invention, in the all-wheel-drive motorcycle in which the engine drives the rear wheel and also drives the hydraulic pump, and oil pressure generated by the hydraulic pump is supplied to the hydraulic motor for driving the front wheel, the drive gear is provided on the output shaft of the hydraulic motor, and the driven gear is provided on the hub. In view of the fact that the driven gear is provided on the side of the axle, it is easy to set the diameter of the driven gear to be smaller than the diameter of the drive gear. In addition, it is also easy to set the former to be larger than the latter.

Since it is easy to change the diameter of the driven gear, flexibility in setting the diameter of the driven gear is advantageously increased.

According to an embodiment of the present invention the drive gear is provided on the output shaft of the hydraulic motor with the driven gear being provided in the recess portion of the hub, and the diameter of the drive gear is set to be larger than the driven gear.

Since the number of revolutions of the hydraulic motor is smaller than the number of revolutions of the front wheel, the number of revolutions of the hydraulic motor can be reduced. Thus, a lowering of the output or the mileage due to the hydraulic pressure loss can be advantageously restrained.

According to embodiment of the present invention, since the output shaft of the hydraulic motor is arranged so as to be inclined with respect to the axle by employing the bevel gears for the drive gear and the driven gear and arranging the bevel gears so that the small diameter portions face the inside of the recess portion, even though the diameter of the drive gear is increased, the arrangement of a seal member for sealing between the hub and the cover is not affected. Thus, upsizing of the hub in the direction of the axle can be restrained.

In addition, since the output shaft of the hydraulic motor is arranged to be inclined with respect to the axle, even though the diameter of the drive gear provided on the output shaft is increased, upsizing of the hub in the radial direction is restrained. Thus, the drive gear and the driven gear can be arranged compactly around the axle of the front wheel.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A best mode for carrying out the present invention will be described below on the basis of the drawings.

FIG. 1is a side view of an all-wheel-drive motorcycle according to the present invention. An all-wheel-drive motorcycle10includes a vehicle body frame11with a front fork12steerably mounted to a front portion of the vehicle body frame11and a steering handle13mounted to an upper portion of the front fork12. A front wheel15is mounted to a lower portion of the front fork12via a front wheel axle14. A fuel tank16and a passenger seat17are arranged on the vehicle body frame11from the front to the rear. A swing arm18is mounted to a rear portion of the vehicle body frame11so as to be capable of moving in the vertical direction about a pivot shaft21with a rear wheel23being mounted to a rear end of the swing arm18via a rear wheel axle22.

A front fender24is provided with a front cowl25, a side cowl26, a headlight27, a stop lamp28and a step29.

A drive system for the motorcycle10includes an engine31mounted across the vehicle body frame11. An engine sprocket33is mounted to an output shaft32of the engine31with a rear wheel sprocket34being mounted to the rear wheel23. A chain35is provided for transmitting a drive force, the chain35connects the rear wheel sprocket34with the engine sprocket33. A hydraulic pump41is provided for driving the front wheel and is connected to the output shaft32of the engine via a drive force transmitting means38including a gear36and a gear37. A hydraulic motor42, for driving the front wheel15, is mounted to the lower portion of the front fork12. A hydraulic pipe, not shown, is connected between the hydraulic motor42and the hydraulic pump41.

Since the hydraulic pump41is arranged above the output shaft32of the engine and near a center of gravity of the motorcycle10, the influence to the weight distribution between the front wheel15and the rear wheel23is negligible.

In other words, the all-wheel-drive motorcycle10drives the rear wheel23by transmitting the power of the engine31to the rear wheel23via the chain35. Hydraulic pressure is supplied to the hydraulic motor42of the front wheel15by the engine-driven hydraulic pump41. Thus, the front wheel15is driven by the hydraulic motor42.

In addition to this, a muffler44is mounted from the engine31to the rear via an exhaust pipe43.

The structure around the front wheel15will be described with the next drawing in detail.

FIG. 2is a cross-sectional view taken along the line2-2inFIG. 1. A front wheel hub structure50is a part of the front wheel15. The hub51includes a boss portion52for allowing passage of the front wheel axle14, a recess portion53, and a cylindrical portion54. The hydraulic motor42is provided for transmitting power to the front wheel hub51. A cover55is provided for fixedly supporting the hydraulic motor42and for covering the recess portion53of the front wheel hub51. The front wheel axle14fixes the cover55to the front fork12. The boss portion52, provided at an axial center56of the front wheel hub51, is provided for allowing passage of the front wheel axle14. A needle bearing61is provided with a single-row angular-shaped radial ball bearing62be interposed between the boss portion52and the front wheel axle14with a sleeve63kept in abutment with the radially outside of the bearings61,62and fixed to the boss portion52. A driven gear64is fitted on the outer periphery of the sleeve63. A drive gear65, to be engaged with the driven gear64, is provided on an output shaft77of the hydraulic motor42. A plate67is provided for a disk brake. A collar78is mounted adjacent to the needle bearing61.

In order to prevent foreign substances such as water, dust or dirt from entering between an outer peripheral edge66of the cover55and the cylindrical portion54of the hub51and attaching on the drive gear65and the driven gear64, sealing means73including a labyrinth portion71and a seal member72is provided.

Since the recess portion53of the hub51with the drive gear65and the driven gear64arranged therein is configured to be a dual structure with the labyrinth portion71and the seal member72, entry of the foreign substances into the recess portion53of the hub51can be prevented.

A collar member74is a member for limiting the axial (also referred to as the direction of the axle) movement by being placed between the needle bearing61and the single-row angular-shaped radial ball bearing62.

The front wheel axle14is a member to be inserted in the direction indicated by an arrow75and tightened at one end thereof by a shaft nut76.

An output shaft77of the hydraulic motor is arranged obliquely with respect to the front wheel axle14with a diameter85of the driven gear64, mounted to the front wheel hub51, being smaller than a diameter84of the drive gear65mounted to the output shaft77of the hydraulic motor42. A gear mounted to the output shaft77of the hydraulic motor42is a bevel gear.

In other words, the front wheel hub51is the cup-shaped hub provided with the recess portion53, and the recess portion53of the hub51is covered by the cover55. Then, the hydraulic motor42is supported by the cover55, the drive gear65is mounted to the output shaft77of the hydraulic motor42, and the driven gear64is mounted to the recess portion53of the hub51.

In this manner, since the output shaft77of the hydraulic motor is arranged obliquely with respect to the axle14, a space is defined between the inner side of the annular recess portion53of the hub51to which the plate67is mounted. Thus, a front portion of the drive gear65, and a rib79can be provided using the space. Since the rib79can be provided, the strength of the hub51can be increased without increasing the thickness of the hub51.

In addition, by employing the bevel gears as the drive gear65and the driven gear64, and arranging the bevel gear in such a manner that a smaller diameter portion81of the bevel gear is directed inwardly of the recess portion53, the output shaft77of the hydraulic motor42is inclined with respect to the front wheel axle14.

FIG. 3is a cross-sectional view taken along the line3-3inFIG. 2. The engaging portion includes the collar member74that is fitted on the periphery of the front wheel axle14. The sleeve63, on the rotating side with respect to the front wheel axle14, is arranged at a distance from the collar member74. The driven gear64is fixed to the sleeve63with the driven gear64being engaged with the drive gear65provided on the output shaft77of the hydraulic motor42(seeFIG. 2).

A pitch circle82of the drive gear65is provided together with a pitch circle83of the driven gear64. The reduction gear ratio is determined by the ratio between the diameters of the two pitch circles, and a pitch circle diameter Dpj of the driven gear64is set to be larger than a pitch circle diameter Dpk of the drive gear65.

In other words, the drive gear65is mounted to the output shaft77of the hydraulic motor, the driven gear64is mounted to the recess portion53of the hub51(seeFIG. 2), and the diameter84of the drive gear65is set to be larger than the diameter85of the driven gear64. A cylindrical portion54of the hub51is provided.

FIG. 4is a hydraulic system chart of the all-wheel-drive motorcycle according to the present invention, showing the all-wheel-drive motorcycle10in which the engine31drives the rear wheel23and also drives the hydraulic pump41. Oil pressure generated by the hydraulic pump41is fed to the hydraulic motor42, so that the front wheel15is driven by the hydraulic motor42. An oil control means86, for controlling the oil pressure, is interposed between the hydraulic pump41and the hydraulic motor42.

The oil control means86includes a pressurizing tank89including pressurizing means87and a filter88with an operation switching means91for switching the discharging port of the oil, a check valve92and a safety valve93. The oil control means86is configured by connecting a return pipe94A from the hydraulic motor42to the pressurizing tank89having the pressurizing means87and the filter88integrated therein. The operation switching means91is connected to the pressurizing tank89. The operation switching means91is connected by a return pipe94B to the hydraulic pump41. The hydraulic pump41is connected by an output pipe95to the hydraulic motor42. A bypass pipe96is connected to the output pipe95with the check valve92being interposed. The safety valve93is connected to the bypass pipe96. The check valve92and the safety valve93are connected to the pressurizing tank89.

The check valve92is arranged so that the oil flows only in the direction from the pressurizing tank89to the bypass pipe96, and the safety valve93is arranged in the orientation which allows oil flow from the bypass pipe96toward the pressurizing tank89only when the pressure is higher than a predetermined pressure.

The hydraulic pump41is a swash plate type axial pump, and the hydraulic motor42is an axial piston motor.

In this embodiment, front and rear wheel speed sensors97,98can be attached to the front wheel15and the rear wheel23, respectively. By providing the wheel speed sensors97,98, a wheel speed signal of the front wheel15and a wheel speed signal of the rear wheel23can be detected separately, and these signals can be used for hydraulic control.

Hereinafter, a description will be made about specific elements in the hydraulic system chart.

First, the pressurizing means87is mounted to the pressurizing tank89. By providing the pressurizing means87, the hydraulic pressure between the hydraulic motor42and the hydraulic pump41increases at the time of high load, whereby the generation of air bubbles in the return pipes94A,94B by the lowering of the oil pressure can be prevented.

Subsequently, the check valve92is arranged between the pressurizing tank89and the bypass pipe96. The check valve92is for preventing the rotation of the front wheel15from being hindered by the check valve92when the number of revolutions of the rear wheel23is lowered to a value lower than the number of revolutions of the front wheel15. Even when the number of revolutions of the hydraulic pump41is lowered, oil of an amount corresponding to the difference in the number of revolutions is returned from the check valve92through the bypass pipe96to the output pipe95. Thus, the hydraulic system such as the hydraulic motor42is prevented from being subjected to a load from the rotation of the front wheel15, whereby the rotation of the front wheel15is prevented from being impaired.

The safety valve (relief valve)93is provided between the pressurizing tank89and the bypass pipe96.

By providing the safety valve93, when the hydraulic pressure in the output pipe95is significantly increased, for example if the rear wheel23slips during traveling on a rough-terrain and the rotation of the hydraulic pump41is increased, the safety valve93is opened and oil enters into the pressurizing tank89from the output pipe95through the bypass pipe96and the safety valve93. Therefore, a significant increase in hydraulic pressure can be avoided.

An operation of the oil control means86will be described.

In the all-wheel-drive mode, when a port A and a port C of the operation switching means91are brought into communication, and a port B is closed, oil circulates in sequence from the hydraulic pump41through the output pipe95, the hydraulic motor42, the oil control means86composed of the pressurizing tank89, the filter88, and the operation switching means91, the return pipe94B, the hydraulic pump41to rotate the hydraulic motor42.

When the rear wheel23and the front wheel15rotate at substantially the same wheel speed, the hydraulic motor42rotates simultaneously with the wheel speed of the front wheel15. Therefore, when the wheel speed of the rear wheel23and the front wheel15is substantially the same, a drive force by the hydraulic motor42is not generated.

When the possibility of occurrence exists during traveling on snow or during traveling on rough-terrain and the wheel speed of the rear wheel23is increased to a wheel speed higher than that of the front wheel15, the hydraulic pressure between the hydraulic pump41and the hydraulic motor42is increased, and the hydraulic motor42applies the drive force to the front wheel15.

On the other hand, in the rear-wheel-drive mode, when the ports A-C of the operation switching means91are brought into communication with each other, the output pipe95and the return pipe94B are brought into communication by the bypass pipe96and the operation switching means91. Therefore, the hydraulic pressure applied to the hydraulic motor42is lowered. Thus, the front wheel15is not driven by the hydraulic motor42. Since the hydraulic motor42is driven and rotated by the front wheel15, oil circulates in sequence from the hydraulic motor42→the return pipe94A→the oil control means86→the bypass pipe96→the output pipe95, and the hydraulic motor42is not affected by the hydraulic pump41.

Switching between the all-wheel-travel mode and the rear-wheel-travel mode may be performed manually. Alternatively, it is also possible to detect the speed difference from the signal of the front wheel speed sensor97and the signal of the rear wheel speed sensor98so that the mode is switched from the rear-wheel-travel mode to the front-wheel-travel mode automatically.

FIGS. 5(a) and5(b) are explanatory drawings showing a structure of the front hub of the all-wheel-drive motorcycle.

FIG. 5(b) shows that the diameter of the drive gear65is larger than that of the driven gear64.

The driven gear64and the drive gear65may be, for example, a spur gear or a helical gear.

In addition toFIG. 5(b),FIG. 5(a) shows that bevel gears are employed as the drive gear65and the driven gear64and arranged so that the smaller diameter portions81of the bevel gears face toward the inside of the recess portion53, so that the output shaft77of the hydraulic motor42is inclined with respect to the front wheel axle14.

The sizes ofFIG. 5(b) andFIG. 5(a) are compared in the axial direction and in the radial direction.

By arranging the drive gear65so as to be inclined and engaged with the bevel gear, the occupied width of the hydraulic motor42in the direction of the axle in the case ofFIG. 5(a) can be reduced by ΔW in comparison with the case ofFIG. 5(b). In addition, the relation between the widths Ha, Hb of the hub51is Ha<Hb, and the labyrinth portion71and the seal member72are arranged at the widthwise center side. Thus, an increase in the width of the hub can be avoided.

In the radial direction, the relation of the outer diameters Da, Db of the hub is Da<Db, and by arranging the drive gear65so as to be inclined and engaging with the bevel gear, the height of the hub inFIG. 5(a) can be reduced by the length (Db-Da) in comparison with that inFIG. 5(b).

Therefore, by arranging the drive gear65so as to be inclined and engaging with the bevel gear, the size of the hub51can be reduced both in the direction of the axle and in the radial direction.

Consequently, the size and the weight of the hub51can be reduced.

An operation of the present invention will be described below.

InFIGS. 5(a) to5(b), since the drive gear65is provided on the output shaft77of the hydraulic motor42, and the driven gear64is provided on the axle side which is integrated with the hub51, flexibility in setting the diameter of the driven gear can be increased.

In addition, since the drive gear65is provided on the output shaft77of the hydraulic motor42, and the driven gear64is provided in the recess portion53of the hub51, the diameter of the drive gear65may be set to be larger than the driven gear64. Thus, the number of revolutions of the hydraulic motor42is set to be lower than the number of revolutions of the front wheel15.

Since the number of rotations of the hydraulic motor42is lower than the number of revolutions of the front wheel15, the number of revolutions of the hydraulic motor42is reduced in the high-speed traveling. Thus, the output due to the hydraulic pressure loss or lowering of mileage can be prevented.

Here, the lowering of the output or the mileage during high-speed traveling in a case wherein the diameter of the driven gear is set to be larger than the diameter of the drive gear, as shown in Jp-A-2000-229596, will be described.

When the diameter of the driven gear is set to be larger than the diameter of the drive gear, the number of revolutions of the front wheel becomes smaller than the number of revolutions of the hydraulic motor. Since the speed of revolution of the hydraulic motor needs to be as high as several times the number of revolutions of the front wheel, the hydraulic motor needs to be rotated at high speed during operation at a high-speed.

Although the hydraulic motor circulates oil pressure with respect to the hydraulic pump, when the flow velocity of the oil pressure is increased, the resistance in the flow path abruptly increases at the rate of a square of the flow rate. The resistance in the flow path appears as a loss, and the amount of output subtracted from the output transmitted to the hydraulic pump by the engine by the loss of the resistance in the flow path is outputted for driving the front wheel.

In other words, during high-speed operation, the loss is increased and the output for driving the front wheel is decreased.

Consequently, a lowering of the output results. The mileage is also lowered corresponding to the loss.

In contrast, according to the present invention, since the diameter of the driven gear can be set to be smaller than the diameter of the drive gear, the number of revolutions of the hydraulic motor42is reduced. Thus, a lowering of the output or mileage due to a loss of the hydraulic pressure can be restrained in the high-speed traveling.

InFIG. 5(a), since the output shaft77of the hydraulic motor42is arranged so as to be inclined with respect to the front wheel axle14by employing the bevel gears as the drive gear65and the driven gear64and arranging the bevel gears so that the smaller diameter portions81of the bevel gears face toward the inside of the recess portion53, the seal member72for sealing between the hub51and the cover55can be arranged on the rear side of the drive gear65without upsizing the hub51in the direction of the axle.

Since the output shaft77of the hydraulic motor42is arranged so as to be inclined with respect to the axle14, even when the diameter85of the driven gear64provided on the hub51is set to be smaller than the diameter84of the drive gear65provided on the output shaft77, it is not necessary to upsize the hub51in the radial direction. Thus, the drive gear65and the driven gear64can be arranged around the axle14of the front wheel15.

Although the present invention is applied to a motorcycle in this embodiment, it is also applicable to a tricycle, and also can be applied to general vehicles without problem.