SPECIFICATION
TITLE OF THE INVENTION:
TRACTOR
FIELD OF THE INVENTION
[0001] The present invention relates to a tractor having a front axle frame supporting a front
axle case.
BACKGROUND OF THE INVENTION
[0002] In a tractor as described above, a front axle frame (front frame) has been configured by
welding left and right side members (first members) composed of a steel strip or sheet to a cross
member (second member) composed of a steel strip or sheet (see, for example, Patent Literature
1).
RELATED ART
Patent Literature
[0003] Patent Literature 1: Japanese Patent Laid-Open Publication No. 2013-136359
(paragraph [0019], Figs. 1 to 7)
SUMMARY OF THE INVENTION
Problems to Be Solved by the Invention
[0004] In the above configuration, there is a risk of cracks developing in welded portions
between the side members and the cross member during overload tasks in which heavy load
tasks such as bulldozing and towing are performed over an extended period of time. Under these
circumstances, in order to obtain a degree of strength capable of withstanding the heavy load
tasks, a plurality of reinforcement members could be welded to the front axle frame. However,
such a case may result in a decrease in productivity and a drastic rise in costs due to increasing a
number of components and number of steps in welding.
[0005] The present invention obtains a front axle frame having a high degree of strength
appropriate to heavy load tasks, without resulting in a decrease in productivity or a drastic rise in
costs.
Means for Solving the Problems
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[0006] In a tractor that includes a front axle frame supporting a front axle case, the front axle
frame is configured by a cast metal member having a support portion on a bottom of the front
axle frame, the support portion supporting the front axle case.
[0007] According to this aspect, the front axle frame is configured by a cast metal member
having a bottom panel, which readily ensures a high degree of strength. Therefore, in
comparison to a case using a structure welding together steel strips or sheets, for example, a high
degree of strength can be obtained with a small number of components and without requiring the
time and effort of welding.
[0008] In particular, by concentrating innovation in a shape which, for example, increases a
thickness of a location requiring a high degree of strength, that requirement can be readily
handled without resulting in an increase in the number of components and number of steps in
welding due to increasing the reinforcement members to be welded.
[0009] In addition, because there are no welded portions as in a welded structure, a risk of
cracks developing in the welded portions can be avoided during overload tasks in which heavy
load tasks such as bulldozing and towing are performed over an extended period of time.
[0010] Accordingly, a front axle frame can be obtained having a high degree of strength
appropriate to heavy load tasks, while increasing productivity and reducing costs by reducing the
number of components and eliminating a welding process.
[0011] Another aspect improving the suitability of the present invention is that the front axle
frame is made of cast metal.
[0012] According to this aspect, a weight of the front axle frame can be increased as compared
to a front axle frame obtained with a structure welding together steel strips and sheets.
[0013] As a result, an increase to the weight of the vehicle appropriate to heavy load tasks such
as bulldozing and towing can be achieved while reducing a number of balance weights provided.
[0014] Another aspect improving the suitability of the present invention is that the front axle
case includes a front/back-oriented support shaft rotatably supported by front and rear holders.
The front axle frame is long in a front/back direction, spanning the front and rear holders, and
includes the support portions at both the front and rear of the front axle frame. The front axle
frame is configured to support the front axle case with the front and rear support portions, via the
front and rear holders.
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[0015] According to this aspect, the front axle frame can be configured to be long at least in the
front/back direction, spanning the front and rear holders.
[0016] Accordingly, an increase to the weight of the vehicle appropriate to heavy load tasks
such as bulldozing and towing can be achieved while reducing a number of balance weights
provided.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017]
[Fig. 1] is a perspective view of a tractor.
[Fig. 2] is a vertical cross-section of a left lateral view of a relevant portion illustrating a
configuration of a front axle frame, for example.
[Fig. 3] is a plan view of a relevant portion illustrating the configuration of the front axle
frame, for example.
[Fig. 4] is a bottom view of a relevant portion illustrating the configuration of the front
axle frame, for example.
[Fig. 5] is an exploded perspective view of a relevant portion illustrating the
configuration of the front axle frame, for example.
[Fig. 6] is a schematic vertical cross-section of a left lateral view illustrating a
configuration of a housing unit for heavy load tasks.
[Fig. 7] is a schematic vertical cross-section of a left lateral view illustrating another
configuration of a housing unit for heavy load tasks.
[Fig. 8] is a schematic vertical cross-section of a left lateral view illustrating a
configuration of a housing unit for light load tasks.
[Fig. 9] is a schematic vertical cross-section of a left lateral view illustrating another
configuration of a housing unit for light load tasks.
[Fig. 10] is a schematic vertical cross-section of a left lateral view illustrating yet another
configuration of a housing unit for heavy load tasks.
[Fig. 11] is a lateral cross-section of a plan view of a relevant portion illustrating a
configuration of an oil filter attachment portion of a housing unit.
MODE FOR CARRYING OUT THE INVENTION
[0018] In the following, an example of an embodiment of the present invention is described
with reference to the drawings.
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[0019] As shown in Fig. 1, an exemplary tractor in the present embodiment includes a motor
portion 2 in a front half of a vehicle body frame 1, and a cockpit 3 in a rear half of the vehicle
body frame 1. In addition, front wheels 4 (drivable steered wheels) are arranged on a left and
right of the motor portion 2 and rear wheels 5 (brake-enabled drive wheels) are provided on the
left and right of the cockpit 3, configuring a four-wheel drive model.
[0020] As shown in Figs. 1 to 5, the vehicle body frame 1 is configured such that a watercooled
upright diesel engine (hereafter referred to as an engine) 9 is connected via left and right
side members 8 (each configured by a steel strip) to a rear portion of a front axle frame 7
supporting a front axle case 6, and such that a cast metal housing unit 10 is connected to a
bottom portion of the engine 9.
[0021] The motor portion 2 is configured by providing the engine 9 and the like in an engine
compartment, which is formed by a hood 12 and the like. The cockpit 3 includes a steering
wheel 13 for front wheel steering, a driver's seat 14 capable of adjusting a position of the seat 14
in a front/back direction, and the like. The steering wheel 13 is linked to the left and right front
wheels 4 via a total hydraulic power steering apparatus 15 or the like. The power steering
apparatus 15 is configured by, for example, a double action steering cylinder 16 for front wheel
steering, which is attached to a rear portion of the front axle case 6; a control unit (not shown in
the drawings) controlling a flow of oil to the steering cylinder 16 in accordance with operation of
the steering wheel 13; and a pair of hydraulic hoses 17 connecting the steering cylinder 16 and
the control unit.
[0022] As shown in Figs. 2 to 5, the front axle frame 7 is configured by a cast metal member
formed in the shape of a frame having a bottom panel, the front axle frame 7 including a front
wall 7A, left and right side walls 7B, a rear wall 7C, and a bottom 7D, for example. Specifically,
the front axle frame 7 is configured by a cast metal member having a bottom panel, which
readily ensures a high degree of strength. Therefore, in comparison to a case using a structure
welding together steel strips or sheets, a high degree of strength can be obtained with a small
number of components and without requiring the time and effort of welding. In addition,
because there are no welded portions as in a welded structure, a risk of cracks developing in the
welded portions can be avoided during overload tasks in which heavy load tasks such as
bulldozing and towing are performed over an extended period of time. Also, a weight of the
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front axle frame 7 can be increased, thus facilitating an increase to the weight of a vehicle
appropriate to heavy load tasks such as bulldozing and towing.
[0023] As shown in Figs. 1 to 5, the front wall 7A of the front axle frame 7 is configured at a
coupling location where a weight support member 19 enabling a balance weight 18 to be added
or removed is bolt-coupled. The weight support member 19 is configured by cast metal.
Specifically, a weight of the weight support member 19 can be increased, thus further facilitating
an increase to the weight of the vehicle appropriate to heavy load tasks such as bulldozing and
towing.
[0024] Each of the side walls 7B of the front axle frame 7 are configured at coupling locations
where a rear half of each of the side walls 7B is bolt-coupled to a front half of the corresponding
side member 8. In addition, the side walls 7B of the front axle frame 7 are formed in a shape
having a stepped portion 7Ba, the stepped portion 7Ba creating a left/right spacing at the front
half of each of the side walls 7B larger than the left/right spacing at the rear half of each of the
side walls 7B so as to prevent an exterior surface of each of the side members 8 from projecting
past an exterior surface of the front half of each of the side walls 7B.
[0025] The bottom 7D of the front axle frame 7 includes front and rear support portions 7Da
supporting the front axle case 6 on both front and rear ends of the bottom 7D. The bottom 7D
also includes two front and rear hydraulic pipe openings 7Db between the front and rear support
portions 7Da. The front and rear support portions 7Da are configured at coupling locations
where front and rear holders 21 are bolt-coupled, the holders 21 rotatably supporting a
front/back-oriented support shaft 20 which is provided to the front axle case 6. Specifically, the
front axle frame 7 is configured such that the front axle case 6 is supported so as to be capable of
rolling, and is supported by the front and rear support portions 7Da provided to the bottom 7D,
via the front/back-oriented support shaft 20 and the front and rear holders 21. Also, the front
axle frame 7 can be configured such that at least the bottom 7D is long in the front/back
direction, spanning the front and rear holders, thus further facilitating an increase to the weight
of the vehicle appropriate to heavy load tasks such as bulldozing and towing.
[0026] The rear hydraulic pipe opening 7Db is formed so as to be positioned above the steering
cylinder 16, which is attached to the rear portion of the front axle case 6. In addition, the
opening 7Db is formed to have a rectangular shape in a plan view, of a size enabling a task of
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connecting a hydraulic hose 17 from above the front axle frame 7 to the steering cylinder 16
positioned below the front axle frame 7.
[0027] In a case where the steering cylinder 16 is attached to the front portion of the front axle
case 6, the front hydraulic pipe opening 7Db is formed so as to be positioned above the steering
cylinder 16. In addition, the opening 7Db is formed to have a rectangular shape in a plan view,
of a size enabling the task of connecting the hydraulic hose 17 from above the front axle frame 7
to the steering cylinder 16 positioned below the front axle frame 7.
[0028] Although omitted from the drawings, an independent dual clutch enabling an operation
interrupting drive power for travel and an operation interrupting drive power for work; a geartype
main speed change device speed-changing the drive power for travel; a gear-type auxiliary
speed change device speed-changing the drive power after the drive power has been speedchanged
by the main speed change device; and a rear wheel differential gear, for example, are
provided in an interior of the housing unit 10.
[0029] In this regard, in a case where a high horsepower engine 9 appropriate to heavy load
tasks such as bulldozing and towing is provided, a need arises to employ a broad transmission
gear or the like having a high degree of strength, which is capable of withstanding the high
horsepower. Therefore, an overall length of a transmission system installed in the housing unit
10 increases, necessitating that an overall length of the housing unit 10 be increased. In addition,
a need arises to increase the strength of the housing unit 10 for use with the high horsepower.
[0030] Conversely, in a case where a low horsepower engine 9 appropriate to light load tasks
such as tilling is provided, a narrow transmission gear or the like for low horsepower can be
employed. Therefore, the overall length of the transmission system installed in the housing unit
10 decreases, necessitating that the overall length of the housing unit 10 be decreased. In
addition, a need arises to reduce the weight of the housing unit 10 for use with the low
horsepower.
[0031] Also, in cases where the housing unit 10 for heavy load tasks and the housing unit 10
for light load tasks are each cast using dedicated die molds, tooling costs may rise.
[0032] Under these circumstances, the housing unit 10 is configured as follows.
[0033] As shown in Figs. 6 and 7, the housing unit 10 for heavy load tasks used by the present
tractor is configured to heavy load specifications, in which the total length is long, appropriate to
heavy load tasks such as bulldozing and towing, by bolt-coupling a front housing 10A in which
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the dual clutch as well as the main and auxiliary speed change devices and the like are installed;
a rear housing 10B in which the rear wheel differential gear and the like are installed; and a
middle housing 10C interposed between the front housing 10A and the rear housing 10B. In
addition, in order to ensure a high degree of strength and heavy weight appropriate to heavy load
tasks such as bulldozing and towing, each of the housings 10A to 10C are cast so as to have an
overall thick wall thickness. Also, forming each of the housings 10A to 10C such that a coupling
structure between the front housing 10A and the middle housing 10C and a coupling structure
between the rear housing 10B and the middle housing 10C are the same enables the front
housing 10A and the rear housing 10B to be bolt-coupled together. With such a coupling, the
overall length of the housing unit 10 can be reduced, enabling use with models having a short
wheel base.
[0034] As shown in Fig. 8, the housing unit 10 for light load tasks is configured to light load
specifications, in which the total length is short, appropriate to light load tasks such as tilling, by
bolt-coupling a front housing 10D for light load tasks, which has an exterior shape and coupling
structure formed identically to those of the front housing 10A for heavy load tasks, to a rear
housing 10E for light load tasks, which has an exterior shape and coupling structure formed
identically to those of the rear housing 10B for heavy load tasks. In addition, in order to achieve
a weight reduction appropriate to light load tasks such as tilling, each of the housings 10D and
10E are cast so as to have an overall thin wall thickness.
[0035] Specifically, in the case of casting the front housing 10A for heavy load tasks and in the
case of casting the front housing 10D for light load tasks, the same primary mold for a front
housing can be used. Also, the same primary mold for a rear housing can be used in the case of
casting the rear housing 10B for heavy load tasks and in the case of casting the rear housing 10E
for light load tasks. Accordingly, tooling costs can be reduced as compared to a case where
separate, dedicated heavy load task primary molds and light load task primary molds are also
used in addition to a nesting piece, core piece, and the like.
[0036] As shown in Fig. 9, an example of the housing unit 10 for light load tasks may be a
housing unit configured so as to include a middle housing 10F having a thin wall thickness for
light load tasks, and which has an exterior shape and coupling structure formed identically to
those of the middle housing 10C for heavy load tasks. With this configuration, the same primary
mold for a middle housing can be used in the case of casting the middle housing 10C for heavy
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load tasks and in the case of casting the middle housing 10F for light load tasks. Also, the
middle housing 10F can be used on models having a long wheel base.
[0037] As shown in Fig. 10, an example of the middle housing 10C for heavy load tasks may
be a middle housing formed so as to have a thicker wall thickness than that of the front housing
10A and the rear housing 10B for heavy load tasks. With this configuration, an increase to the
weight of the vehicle appropriate to heavy load tasks such as bulldozing and towing can be
further facilitated. In addition, an amount of oil stored within the housing unit 10 can be reduced
while providing an appropriate oil level.
[0038] Although not shown in the drawings, an example of the middle housing 10C for heavy
load tasks may also be a middle housing formed such that a lower half of the middle housing has
a thicker wall thickness than that of the front housing 10A and the rear housing 10B for heavy
load tasks. In this configuration also, an increase to the weight of the vehicle appropriate to
heavy load tasks such as bulldozing and towing can be further facilitated. In addition, an amount
of oil stored within the housing unit 10 can be reduced while providing an appropriate oil level.
[0039] As shown in Fig. 11, the housing unit 10 is integrally formed with an oil filter
attachment portion 10G. The oil filter attachment portion 10G includes: a first junction port 10a
connecting to an oil inlet 22a of an oil filter 22; a second junction port 10b connecting to an oil
outlet 22b of the oil filter 22; a first connection port 10c enabling a connection with a first feed
pipe 23, which connects to an oil output port (not shown in the drawings) formed at a
predetermined position on the housing unit 10; a second connection port 10d enabling a
connection with a second feed pipe 24, which connects to a hydraulic pump (not shown in the
drawings); a first internal oil passage 10e running between the first junction port 10a and the first
connection port 10c; and a second internal oil passage 10f running between the second junction
port 10b and the second connection port 10d. In addition, by connecting the oil outlet 22b of the
oil filter 22 to the second junction port 10b via a nipple 25, the configuration enables attaching
the oil filter 22 at a predetermined position of the housing unit 10.
[0040] Based on the above-noted configuration, by attaching the oil filter 22 to the oil filter
attachment portion 10G, and also by connecting the first feed pipe 23 (connected to the oil output
port of the housing unit 10) to the first connection port 10c and connecting the second feed pipe
24 (connected to the hydraulic pump) to the second connection port 10d, the housing unit 10 can
form a suction intake oil passage running from the oil output port to the hydraulic pump.
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[0041] In addition, a location on the housing unit 10 where the oil filter attachment portion
10G is provided can be readily changed in a design through changing a placement of a nesting
piece, core piece, or the like for molding the attachment portion, which are used when each of
the housings 10A to 10F are cast. Specifically, despite having a configuration in which the oil
filter attachment portion 10G is formed integrally with the housing unit 10, a degree of freedom
in positioning the oil filter 22 can be increased.
[0042] (Other Embodiments)
[0043] (1) The front axle frame 7 may be made of die cast aluminum or the like.
[0044] (2) The shape of the front axle frame 7 can be variously modified in response to a
required degree of strength, a required weight, and the like. For example, the front axle frame 7
may have a shape that does not include the hydraulic pipe openings 7Db. In addition, the front
axle frame 7 may be formed to be rectangular in a plan view and a flat cube.
[0045] (3) The front axle frame 7 may be configured so as to support the front axle case 6 in a
fixated state with the support portions 7Da of the bottom 7D.
INDUSTRIAL APPLICABILITY
[0046] The present invention can be applied to a tractor having a front axle frame supporting a
front axle case.
DESCRIPTION OF REFERENCE NUMERALS
[0047]
6 Front axle case
7 Front axle frame
7D Bottom
7Da Support portion
20 Support shaft
21 Holder

SCOPE OF THE CLAIMS:
[Claim 1]
A tractor having a front axle frame supporting a front axle case, wherein the front axle
frame is configured by a cast metal member having a support portion on a bottom of the front
axle frame, the support portion supporting the front axle case.
[Claim 2]
The tractor according to claim 1, wherein the front axle frame is made of cast metal.
[Claim 3]
The tractor according to one of claims 1 and 2, wherein the front axle case includes a
front/back-oriented support shaft rotatably supported by front and rear holders, and
the front axle frame is long in a front/back direction, spanning the front and rear holders,
and includes the support portions at both the front and rear of the front axle frame, and the front
axle frame is configured to support the front axle case with the front and rear support portions,
via the front and rear holders.