Note: Descriptions are shown in the official language in which they were submitted.
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A RUNNING APPARATUS FOR AN
AGRICULTURAL VEHICLE
Background of the Invention
This invention relates to a running apparatus for an
agricultural vehicle in which an oil stemless change speed
device is provided.
The above-mentioned agricultural vehicle normally has
the following drawbacks or troubles. Namely, when pulses
occur in the output of an oil pump consisting of the step-
less change speed device due to an oil leakage or other causes under such a state that a driving load of the running
apparatus is relatively small and driving speeds thereof
are relatively fast and that the vehicle runs on a flat road
at high speeds, variation of rotation speeds of an oil motor
becomes extremely great due to the pulsing output thereof
and then brings about great driving noises and gives the
vehicle body a compulsive vibration which is discomfort able
to a driver.
Summary of the Invention
The first object of this invention is to improve a run-
nine apparatus for an agricultural vehicle such that speeds
of an oil motor are not easily varied even if an oil pump
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produces a pulsing output.
The characteristic construction of this invention for
achieving the first object is that a running apparatus for
an agricultural vehicle comprises an oil stemless change
speed device consisting of an oil pump and an oil motor,
oil paths for connecting the oil pump and the oil motor,
and an accumulator disposed in parallel with the oil motor
between the paths, characterized in that the accumulator
is so constructed as to accumulate therein a surplus of an
output pressure of the oil pump when the output pressure
is greater than a predetermined value and as to discharge
an accumulated pressure when the output pressure of the oil
pump is smaller than the predetermined value.
Namely, by providing the accumulator in the above-men-
toned state, when the output pressure of the pump becomes greater than a predetermined value, the accumulator absorbs
and accumulates a surplus pressure of the output pressure
and controls the output pressure for the motor to be reduced
into a value lower than that of the output pressure of the
pump, and when the output pressure is smaller than the
predetermined value, the accumulator discharges the accumu-
fated pressure so as to control the pressure for the motor
to be increased to a value greater than that of the output
pressure of the pump.
Therefore, even if pulses occur in the output of the
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pump, the oil pressure to the motor may be kept substantial-
lye at a predetermined value so as to make rotation speeds
of the motor constant to the utmost, so that it becomes
possible to drive the vehicle comfortably by preventing
issues of noises and compulsive vibrations to the vehicle
body due to such a pulsing output of the pump.
The second object of this invention is to obtain the
above-mentioned advantages by only providing the accumulator
with a single piston.
To achieve the second object, the running apparatus for
the agricultural vehicle according to this invention cam-
proses the accumulator which comprises a piston disposed
reciprocally slid ably, a pair of oil pressure chambers for
the piston, each being connected to a pair of the oil paths
and arranged separately at each end of the piston, and an
accumulating spring or springs arranged to urge the piston
to return to a neutral position.
Namely, since a pair of the oil pressure chambers for
the piston are connected respectively to a pair of the oil
paths and arranged separately at each end of the piston and
then the accumulating spring or springs are arranged to urge
the piston to return to a neutral position, the spring or
springs are deformed flexibly by the oil pressure acting on
an end of the piston when forward running and the spring or
springs are deformed flexibly by the oil pressure acting on
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the other end of the piston when rearward running, and
therefore accumulation and discharge of the oil pressure
may be carried out in both the forward and rearward running
by providing only such a single piston.
Therefore, it is not necessary to provide a changing
means or to save trouble of provision thereof in comparison
with such a case that it is necessary to connect an accumu-
later having a piston only on the side of the supplying
path to the motor with respect to a pair of the paths.
Thus, it may be driven comfortably in any of forward and
rearward running. This running apparatus has been obtain-
Ed simple in construction and operation.
Other advantages of this invention will be apparent
from the following description.
grief Description of the Drawings
The drawings show an embodiment of a running apparatus
for an agricultural vehicle in which:-
Fig. 1 is a side elevation of an agricultural tractor,
Fig. 2 is a side view of a mount section of an oil
stemless change speed device,
Fig. 3 is an oil circuit,
Fig. 4 and Fig. 5 are sectional views of an accumulator,
Fig. 6 is a sectional view of another embodiment of an accumulator,
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Fig. 7 is a sectional view of a further embodiment of
an accumulator, and
Fig. 8 is a circuit for another embodiment of a change
speed device.
Detailed Description of the Preferred Embodiments
As shown in Fig. 1, an agricultural tractor is construct-
Ed such that a lift arm 1 which is singable up and down and
liftable connected to any type of working implements such as
a rotary cultivating device (not shown), and a power take-
off shaft 2 for transmitting a power to the connected working implement, are disposed at a rear portion of a self-propelled
vehicle body having a running device of wheel type.
In a drive line from an engine 3 to front wheels 4 and
rear wheels 5, there is provided an oil stemless change speed
device 6 which is changeable from neutral to forward and to
rearward. As shown in Fig. 2, a change speed operating
pedal 14 which is operatively connected to an operating arm
7 singable about an axis Pi of the change speed device 6,
via a singable connecting member Andy a rotary shaft 13,
is singable attached to a transmission case 16 which come
proses a tractor body frame. A roller 9 is singable
attached to the change speed device 6 via a swing support
arm 8 to be singable about an axis Pi. The roller 9 is
urged to contact with a V-shaped cam surface pa of the lower
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end of the operating arm 7 by means of a spring 10 so that
the operating arm 7 and the change speed pedal 14 may be
urged to return to a neutral position _. By stepping the
pedal 14 on the side of forward or rearward of the tractor,
the operating arm 7 is swung to forward F or the rearward
R and as the pedal 14 is stepped more deeply, the operating
arm 7 is close to the side of high speed. Namely, it is
so constructed that the change speed device 6 is operated
by the pedal 14 so as to carry out operations of changing
forward and rearward running, speeds and stopping of the
tractor.
As shown in Fig. 2, an accumulator 15 is attached
to the lower portion of the change speed device 6. As
shown in Fig. 3, the accumulator 15 is connected to a pair
of oil paths aye, 20b for an oil pump 18 as an element of
the change speed device 6 and an oil motor 19 via a pair
of suction and discharge oil paths aye, 17b formed with the
accumulator 15, so as to control variations of rotation
speeds of the motor 19 due to pulsing outputs of the pump
18 even if pulsing occurs in the outputs of the pump 18.
Namely, the accumulator 15 is constructed such that when
the output pressure of the pump 18 is greater than a pro-
determined value a surplus pressure over the predetermined
value of the output pressure is absorbed and accumulated in
the accumulator and controls the oil pressure acting on the
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motor to be reduced to a value lower than the output
pressure of the pump. Further, the accumulator 15 is also
constructed such that when the output pressure of the pump
is smaller than a predetermined value the accumulator
discharges an accumulated pressure and controls the oil
pressure acting on the motor to be increased to a value
higher than the output of the pump. A
charge pump 18' supplies oil to the connecting paths aye
20b in such a state that the pressure of the pump 18 is
10 Compensated.
The accumulator 15 is constructed as shown in Fig. 4
or Fig. 5.
Namely, as shown in Fig. 4, a single piston 21 is
housed in an accumulator case 16 to slide reciprocatingly,
and first and second oil chambers aye, 22b for the piston
21 are provided therein. The first oil chamber aye is
connected to the connecting path aye via the oil path aye
in the accumulator case 16 and the other second oil chamber
22b is connected to the other connecting path 20b via the
path 17b in the accumulator case 16, these thus being
arranged separately adjacent each end of the piston 21 in
such a state that these urge the piston 21 to return to a
neutral position in cooperation with each other. Namely,
when forward running, an oil flows into the first oil
chamber aye and the piston 21 is pushed to slide towards
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the second oil chamber 22b so that the spring 23b may be
compressed. When rearward running, an oil flows into
the second oil chamber 22b and pushes the piston towards
the first oil chamber aye so that the other spring aye
may be compressed.
As shown in Fig. 5, a single piston 24 is housed in
an accumulator case; 16 to slide reciprocatingly, and
first and second oil chambers aye, 25b for the piston 24
are provided therein. The oil chamber aye is connected
to the connecting path aye via the path aye in the
accumulator case 16 and the other chamber 25b is
connected to the other connecting path 20b via the oil
path 17b in the accumulator case 16, these chambers being
separately arranged adjacent each end of the piston 24.
A single compression spring 26 is housed in the first oil
chamber aye. An end portion of the spring 26 is supported
by a side surface aye of an intermediate portion of the
piston 24 and an oil chamber interior wall aye of the
accumulator case 16 via a first spring receiver 27 which is
slid ably fitted to the piston 24. The other end portion
of the spring 26 is supported by an end surface 24b of the
piston 24 and an oil chamber interior wall 16b of the case
16 via a second spring receiver 28 which is slid ably fitted
to the piston 24 so that the spring 26 may urge the piston
24 to return to a neutral position where the side surface
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aye of the intermediate portion and the oil chamber
interior wall aye maze substantially a flat plane.
Namely, in the case of forward running, a pressure oil
flows into the first oil chamber aye and the piston 24 is
slimed towards the second oil chamber 25b, and compresses
the spring 26 via the end surface 24b and the second spring
receiver 28 so as to accumulate a power therewith. Further,
when rearward running, an oil flows into the second oil
chamber 25b and the piston 24 is slimed towards the first
oil chamber aye and then compresses the spring 26 via the
intermediate surface aye and the first spring receiver 27
so as to accumulate a power therewith.
Another aspect of the accumulator 15 is as shown in
Fig. 6. Two pistons aye and 121b are housed slid ably in
an accumulator case 122. An oil chamber aye for forward
running is formed with the accumulator case 122 adjacent
one end of the piston aye in such a state that the oil
chamber is in communication with an inlet or outlet port
' aye. An oil chamber 123b for rearward running is formed
with the accumulator case 122 adjacent one end of the other
piston 121b in such a state that the oil chamber is in
I! communication with an inlet or outlet port 124b. A compress
soon spring 125 is interposed between the two pistons aye
and 121b. Each of the two pistons aye and 121b has a
spring housing space 126 and a connection path 127 to the
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oil chamber aye or 123b, and a valve 128 for the connect
lion path 127 is housed slid ably in each of the pistons
aye and 121b. The valve 128 of the piston aye or 121b
in an accumulating position is maintained in a closed
position in contact with a valve seat 129 by means of an
oil pressure in the oil chamber aye or 123b. On the
contrary, to enable a spring compression action for the
piston aye or 121b, the valve 128 of the piston 121b or
aye in a discharging position is operated into an open
state remote from a valve seat 129 by means of a pressing
action of the piston 121b or aye caused by the oil stayed
in the spring housing space 126 into which an oil leaks and
flows from the oil chamber aye or 123b through between
the piston aye or 121b and the accumulator case 122.
The leaked oil in the spring housing space 126 flows into
the oil chamber 123b or aye through the connection path 127
in order to return same to either of the connecting oil
paths aye or 20b (in Fig. 3) which has a lower oil pressure
than the other. In other words, the leaked oil from the
oil chamber aye or 123b is returned to the change speed
device 6 by means of the path aye and 17b for connecting the
j accumulator 15 and the change speed device 6, and by utilize
in an accumulating function of the accumulator 15.
A further aspect of the accumulator 15 is shown
in Fig. 7. A single piston 30 is slid ably housed in an
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accumulator case 31, and two of four compression springs
aye, aye, 32b and 32b are separately arranged on each side
of the piston 30 so as to urge the piston 30 to return to
a neutral position. An oil chamber aye for forward run-
nine is formed with the accumulator case 31 adjacent one end of the piston 30 to be in communication with an inlet
or an outlet port aye. An oil chamber 33b for rearward
running is formed adjacent the other end of the piston 30
to be in communication with an inlet or an outlet port 34b.
Fig. 8 shows another aspect of the stemless change
speed device 6. A relief valve 218 and a neutral valve
219 are housed in a change speed device casing 220 to be
a unit. The relief valve 218 prevents breakage of the oil
path aye or 20b by escaping an oil pressure from the path
aye or 20b to the path aye or 20b which is a return path
from the oil motor 19 to the oil pump 18, when pressures in
the oil pump 18, the oil motor 19, the connecting oil paths
aye and 20b for the oil pump 18 and the oil motor 19,
becomes higher than a predetermined value. The neutral
valve 219 functions to stop the oil motor 19 by escaping
the oil from the oil pump 18 out of the connecting oil paths
aye and 20b when an output pressure of the oil pump 18
becomes lower than a predetermined value. A charge oil
path 222 is connected to a relief oil path 22 in which the
relief valve 218 is provided, so that an oil from a charge
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pump 18~ may be charged to the connecting oil paths aye
and 20b via the relief oil path 22. A drain port aye
for the oil pump 18, a drain port lea for the oil motor
19, a discharge oil port aye of the relief valve 224 to
the charge oil path 222, and a discharge oil port aye of
the neutral valve 219 are opened respectively in the change
speed device casing 220~ so that a leaked oil from the oil
pump 18 and the oil motor 19, a surplus oil from the charge
pump 18' and an escaping oil from the connecting oil paths
aye and 20b due to the neutral valve 219, may be discharged
respectively into the change speed device casing 220.
Further, it is constructed such that the discharged oil
gathered in the casing 220 returns to a tank 227 via a
relief valve 225 for controlling an oil leakage of the oil
pump 18 or the oil motor 19, and a drain oil path 226.
