Self-propelled working vehicle

1. Field of the Invention

The present invention relates to a self-propelled working vehicle, and particularly to a mower, including right and left drive wheels driven independently of each other.

A typical self-propelled working vehicle of this type comprises a front wheel unit, a rear wheel unit including a left rear wheel and a right rear wheel, and a drive transmission apparatus for transmitting drive from an engine to the rear wheel unit. The drive transmission apparatus includes a first drive transmission mechanism for transmitting the drive to the left rear wheel and a second drive transmission mechanism for transmitting the drive to the right rear wheel. The first transmission mechanism is arranged at the left side of a vehicle body, while the second transmission mechanism is arranged at the right side of the vehicle body.

2. Description of the Related Art

For example, Japanese Patent Unexamined Publication No. 2001-275440 discloses a mower including a drive transmission apparatus having a branch transmission case for diverging torque output from an engine to rearward positions, a pair of stepless change speed devices for transmitting the output from the branch transmission case to the rearward positions, and a pair of wheel transmission cases for transmitting the output to a left rear wheel and a right rear wheel individually. A running brake is provided outwardly and laterally of each of the right and left wheel transmission cases to be operable by a brake pedal disposed on a driving platform.

Such a mower includes the right and left brakes provided outwardly of the change speed devices and thus protruding from the vehicle body. As a result, the actual width of the vehicle body is increased, which is contrary to compactness of the vehicle body.

The object of the present invention is to provide a self-propelled working vehicle with a minimized width.

In order to achieve this object, a self-propelled working vehicle of the type noted above according to the present invention includes a brake assembly arranged between the first drive transmission mechanism and the second drive transmission mechanism for acting on an output shaft of a first transmission unit provided for the first drive transmission mechanism and on an output shaft of a second transmission unit provided for the second drive transmission mechanism.

With this construction, the brake assembly is provided within a space formed, as a natural result, between the first transmission unit and second transmission unit arranged at the opposite sides of the vehicle body, respectively. This eliminates the disadvantage of the brake assembly protruding outwardly of the right and left transmission mechanisms. Thus, a compact self-propelled working vehicle with a reduced width can be realized.

Preferably, the first and second transmission units are constructed as change speed devices, respectively, and the first and second change speed devices are operable independently of each other. Particularly, a construction with each of the first and second change speed devices being constructed as a hydrostatic stepless transmission device switchable between forward movement and backward movement is advantageous to a working vehicle that performs operations while frequently reversing its direction of movement.

In one preferred embodiment of the present invention, the brake assembly includes a first braking member movable between a braking position to engage the output shaft of the first change speed device and a releasing position to disengage the output shaft of the first change speed device, a second braking member movable between a braking position to engage the output shaft of the second change speed device and a releasing position to disengage the output shaft of the second change speed device, and a control unit for moving the first and second braking members to the braking positions at the same time. With this construction, the first and second braking members are operable by the single common control unit, which makes the brake assembly compact.

In a further preferred embodiment of the present invention, each braking member includes brake disks arranged coaxially with, and movable axially of, a corresponding one of the output shafts. The control unit for moving the brake disks axially includes pressure plates movable axially of the output shafts by a cam mechanism or a hydraulic mechanism. With this construction, a force acts on at least two pressure plates to move them axially away from each other and operate the two groups of brake disks. This simplifies the brake operating mechanism.

It is also preferable that the vehicle body has a utility space defined centrally thereof defined by the brake assembly and the first and second drive transmission mechanisms. Where this self-propelled working vehicle is a mower, such an arrangement is advantageous since a grass clipping transport duct may extend through this utility space.

Other features and advantages of the invention will be apparent from the following detailed description of the preferred embodiments to be taken with reference to the accompanying drawings.

FIG. 1 is a side elevation of a mower which is one example of self-propelled working vehicle according to the present invention;

FIG. 2 is a schematic plan view of the mower shown in FIG. 1 ;

FIG. 3 is a further schematic plan view of the mower shown in FIG. 1 ;

FIG. 4 is a schematic front view of the mower shown in FIG. 1 ;

FIG. 5 is a system diagram of a power transmission line;

FIG. 6 is a view in vertical section of a brake mechanism;

FIG. 7 is a side view in vertical section of a first drive transmission mechanism; and

FIG. 8 is a view in vertical sectional of a brake mechanism according to another embodiment of the present invention.

FIGS. 1 through 4 show a mower exemplifying a self-propelled working vehicle according to the present invention. The mower comprises a front wheel unit 1 including right and left caster-type front wheels 1 A and 1 B, a rear wheel unit 2 including right and left rear drive wheels 2 A and 2 B, a vehicle frame 3 supported by the front wheel unit 1 and rear drive wheel unit 2 relative to the ground, and a mower unit 40 suspended from the vehicle frame 3 to be vertically movable between the front wheel unit 1 and rear drive wheel unit 2 . A driver's seat 4 is mounted on the vehicle frame 3 generally directly over the mower unit 40 . A duct 60 extends through a space between the right and left rear drive wheels 2 A and 2 B for guiding grass clippings cut by the mower unit 40 to a rear portion of the mower to be discharged rearwardly. A grass catcher 51 is connected to a rear portion of the vehicle frame 3 through a four-point link mechanism 50 to be switchable between a grass collecting position for receiving and collecting the grass clippings and an upper discharging position.

Right and left steering control levers 5 are provided forwardly of the driver's seat 4 on the vehicle frame 3 . A brake pedal 6 is provided in an area around a foot of the operator seated on the driver's seat 4 . An engine 7 is mounted rearwardly of the driver's seat 4 .

As shown in FIG. 5 , a drive transmission apparatus 20 transmits drive from the engine 7 to the right and left rear drive wheels 2 A and 2 B, respectively, and includes a first drive transmission mechanism 20 A for transmitting divided engine drive to the left rear drive wheel 2 A and a second drive transmission mechanism 20 B for transmitting divided engine drive to the right rear drive wheel 2 B. The first and second drive transmission mechanisms 20 A and 20 B have first and second change speed devices 8 A and 8 B incorporated therein, respectively, which are independently operable through the steering control levers 5 . In the present embodiment, each of the change speed devices 8 A and 8 B is arranged as a hydrostatic stepless transmission device selectable between forward movement and backward movement and having a hydraulic pump 8 a driven by the engine 7 and a hydraulic motor 8 b driven by pressure oil supplied from the hydraulic pump 8 a.

With this construction, the mower is steerable by differentiating rotational speed between the right and left rear drive wheels 2 A and 2 B. More particularly, the right and left rear drive wheels 2 A and 2 B are rotatable at the same speed forward to propel the mower straight forward. The right and left rear drive wheels 2 A and 2 B are rotatable at the same speed backward to propel the mower straight backward. One of the right and left rear drive wheels 2 A or 2 B is rotatable at a lower speed forward than the other of the right and left rear drive wheels 2 B or 2 A for causing the mower to make a gentle forward turn with either of the rear drive wheels 2 A or 2 B positioned inwardly. One of the right and left rear drive wheels 2 A or 2 B is rotatable at a lower speed backward than the other of the right and left rear drive wheels 2 B or 2 A for causing the mower to make a gentle backward turn with either of the rear drive wheels 2 A or 2 B positioned inwardly. One of the right and left rear drive wheels 2 A or 2 B is rotatable forward with the other of the right and left rear drive wheels 2 B or 2 A stopped for causing the mower to make a forward pivot turn about either of the rear drive wheels 2 A or 2 B. One of the right and left rear drive wheels 2 A or 2 B is rotatable backward with the other of the right and left rear drive wheels 2 B or 2 A stopped for causing the mower to make a backward pivot turn about either of the rear drive wheels 2 A or 2 B. The right and left rear drive wheels 2 A and 2 B are rotatable in opposite directions for causing the mower to make a spin turn.

As understood from FIG. 4 , the first and second change speed devices 8 A and 8 B are juxtaposed transversely between the rear drive wheels 2 A and 2 B. The engine 7 is provided at a higher level than the change speed devices between the rear drive wheels 2 A and 2 B. With respect to height, the first and second change speed devices 8 A and 8 B are provided between the engine 7 and the rear wheel unit 2 in the present embodiment. Each of the rear drive wheels 2 A and 2 B is supported by a rear axle extending horizontally and outwardly from a lower end of a vertically extending rear axle case 30 attached inwardly of the vehicle frame 3 . The rear axle cases 30 extending upward inwardly of the rear drive wheels 2 A and 2 B define a utility space 100 inwardly thereof. The duct 60 extends longitudinally of the vehicle through this space 100 in the present embodiment.

The drive transmission apparatus 20 will be described next with reference to FIG. 5 .

Drive is transmitted from the engine 7 to an input shaft 71 of an intermediate transmission mechanism 70 and exits from an output shaft 72 of the intermediate transmission mechanism 70 . The output shaft 72 extending in the longitudinal direction of the vehicle is connected to a cross transmission shaft 34 through bevel gears 32 and 33 . The cross transmission shaft 34 is connected at one end thereof to an input shaft of the pump 8 a of the first change speed device 8 A and at the other end thereof to an input shaft of the pump 8 a of the second change speed device 8 B. An output shaft 9 A extending transversely of the motor 8 b of the first change speed device 8 A protrudes from opposite sides of the first change speed device 8 A. Similarly, an output shaft 9 B extending transversely of the motor 8 b of the second change speed device 8 B protrudes from opposite sides of the second change speed device 8 B. The output shaft 9 A of the first change speed device 8 A is coaxial with the output shaft 9 B of the second change speed device 8 B.

Each of free ends of the output shafts 9 A and 9 B is connected to an upper end of a vertical transmission shaft 21 housed in the rear axle case 30 through bevel gears 22 and 23 . Each transmission shaft 21 is connected at a lower end thereof to an axle 2 a or 2 b of the rear drive wheel 2 A or 2 B through bevel gears 24 and 25 .

As illustrated in FIG. 6 , a brake assembly 10 is provided between the first and second change speed devices 8 A and 8 B to be operable by the brake pedal 6 for braking the output shafts 9 A and 9 B of the change speed devices 8 A and 8 B.

The brake assembly 10 includes two multi-disk braking units as braking members. Each of the braking units includes a pressure plate 11 operable in an axial direction to press a plurality of brake disks into contact for braking action. As a control unit of the braking members, a cam mechanism 13 is provided for bridging the output shafts 9 A and 9 B, to be rotatable about the axis to operate the pressure plates 11 in the axial directions. The cam mechanism 13 is a well-known type, and will not particularly described herein. To be brief, a cam plate is rotated to move balls engaged in an inclined groove of the cam plate in the axial directions thereby to press the pressure plates 11 .

Every second disk of the brake disks 12 is fixed, and the disks 12 placed between the fixed disks are rotatable with the output shafts 9 . FIG. 7 shows a brake control shaft 14 rotatable by depression of the brake pedal 6 to rotate the cam mechanism 13 .

The foregoing embodiment employs the cam mechanism 13 as the control unit. Instead, as illustrated in FIG. 8 , a hydraulic mechanism may be employed as the control unit in which a pressure oil supplying space 15 is defined between the pressure plates 11 of the brake assembly 10 . Pressure oil is supplied to the pressure oil supplying space 15 through an oil passage 16 in response to a depression of the brake pedal 6 to actuate piston Ps, thereby to move both of the pressure plates 11 in the axial directions.