Note: Descriptions are shown in the official language in which they were submitted.
This invention relates to a speed-change appara-tus
adapted to give s-teplessly variable output rotation speed by
causing displacement of driven rotation member means -to alter
frictional engagement positions with respect to driving rota-
tion member means kept in fric-tional transmission engagement
: therewith.
Conventional s-tepless speed change apparatus of this
type has a single driving rotation member in frictional engage-
ment with a driven rota-tion member.
With such conventional apparatus, secure driving power
transmission cannot be attained unless the driving and driven
.
rotation members are urged together under considerable force
; owing to -the fact -that both oE the members are in fric-tion
engagement wi-th each other only at a sinyle contact spo-t. Mow-
cver, the use of such a strong Eorce results in the drawback of
causing heavier abrasion of both of the engaging members. Such
a strong compression force exerted on a single contact spot in
the intention of attaining sufficient driving power transmission
causes further difficulty also in that a large unbalanced bending
load is exerted on the shaft of the driven rotation member in one
direction, which ultimately results in -the failure to attain
smooth transmission of the driving power.
The main object of tiliS invention is to provide a step-
less speed change apparatus that avoids the difficulties of the
; conventional construc-tion as above and which will reliably and
smoothly transmit sufficient driving power.
Another object of this invention is to provide a step-
less speed change apparatus of the type mentioned above which
has a simple structure.
~ccordingly, the present invention provides a stepless
speed change apparatus, comprising: a driving bevel gear for
engine power transmission, a plurality of driven bevel gears
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each in meshing engagement with -the driving bevel grear and hav-
ing their rotation axes intersecting at a point, respective driv-
ing rotation members provided for each driven bevel gear and
arranged -to be rotatable integrally -therewith but axially movable
relative thereto, said driving ro-tation memhers each having a
frictional transmission surface, an output shaft journaled to
extend coaxially with the driving bevel gea:r and lie on an ex-ten-
sion ofthe axisthereof, adriven rotationmember splinedon theoutput
shaft having a frictionalperipheral surfacethereof in power trans-
mission engagement with the frictional transmission surfaces ofthe driving rotation members, whereby the fric-tional engagement
positions on the driving frictional transmission surfaces may be
altered, and means for urging the driving rota-tion members to
bear on the driven rotation member.
Ow.i.ny to the provision of such a plurali.ty of drivi.ng
rotation members which are kept in power transmission engagement
with a driven rotation member, the driving power allo-ted to and
borne by each of the transm:ission engagement spots of reduced,
which in turn reduces the abrasion and accordingly the transmis-
sion power loss in the stepless speed changing.
At the same time, power transmission realized at such
a plurality of separate engagement spots of the driven rotation
member contributes to better balanc:ing in -the power -transmission,
namely -the heavy unbalanced bending load exerted on the shaft of
the driven rotation member in one direction is reduced when com-
pared with the conventional structure in which the power trans-
mission occurs at a single engagement spot. It has thus been
made possible to realize smooth transmission.
~ ividing the driving power into such plurality of trans-
mission lines being realized by providing the corresponding numberof driven bevel gears, each meshing with a common driving bevel
gear. The structure is quite simple and compact.
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:
Still another object oE this invention is to make the
frictional driving power transmission from -the clriv:ing rotation
members to the driven rotation member more reliable.
In order to attain this object, cam mechanisms are
provided which are adapted to cause, as the driven bevel gears
are rotated, the driving rotation members -Io be urged on to the
driven rotation member with the urging force proportional to -the
driving torque.
The invention will now be described in more de-tail by
~ 10 way of example only, with reference to -the accompanying drawings
; in which:
Fig. 1 is a longitudinal vertical sectional view of a
transmission section of a trac-tor, with some non-relevant parts
om;-ttec1 Eor clarity;
Fig. 2 is an en:Larged view of a portion essential -to
the understandiny of the invention;
Fig. 3 is a view taken as on line III-III in Fig. 2,
and
Fig. 4 is a view similar to Fig. 3 but of a modified
embodiment of the invention.
In the transmission section of a tractor shown in the
accompanying drawincJs, the driving power frorn an engine E is
transmitted, via a main clutch 1, to a main shaft 2 and further
transmitted, via a main speed-change apparatus 3 and a planetary
gearing reduction mechanism 4 to a sleeve shaft 5. It is sup-
posed that the driving power is still to be transmi-t-ted from the
sleeve shaft 5 normally via an auxiliary speed-change apparatus
(not illus-trated) to a sleeve transmission shaft 6. From this
sleeve transmission shaft 6 after the auxiliary change-speed
apparatus, the driving power is transmitted on the one hand to
rear-wheel axles (not illustrated) via a differential mechanism
- (not illustrated) and on the o-ther hand tc front-wheel axles (~lOt
~ 3~
illustrated) via a transmission shaft 8 journalled in the lower-
most portion of -the overall -transmission case 7.
It is further supposed that the main shaft 2 extends
-to the rear of the transmission case 7, though not illustrated,
to transmit the driving power from the rear end thereof normally
via another speed-change apparatus to a power-take-off shaEt.
Designa-ted at 9 in Fig. 1 is a hydraulic pump to drive
a lift-arm-driving cylinder (not illustrated), wi-th gear oil in
the transmission case 7 serving as the hydraulic medium.
Looking now in detail in-to the main speed-change appara-
tus 3 with reference to F`igs. 2 and 3, the driving power is trans-
mitted frolrl-the main shaf-t 2 to an input shaEt 11 and Eurther
transmitted via a driving k~eve:L gear 13 to three drivell bevel
gears 12a, 12b, 12c disposed in such a manner that the axes
thereof cross together at a point. With these driven bevel gears
12a, 12b, 12c there are associated -the respective driving rota-
tion members 14a, 14b, 14c, for free rotation and axial sliding,
relative to the bevel gears, with their rotating edge surfaces F
adapted for frictional transmission engagemen-t. Within the space
def:ined by -thcse three driving rotation members 14a, 14b, :L4c
arranged generally in a gate Eorrn, there is journaled an ou-tput
shaft 15 to extend coaxiallv with the driving bevel gear 13, thus
on the extension of one and the same axis common thereto, with a
driven rotation member 16 splined on the output shaft 15, having
frictional peripheral surface thereof adapted to be in power
transmission engagement with the mating fric-tional -transmission
surEaces F of the driving rotation members 14a, 14b, 14c with
possibility of altering the frictional engagement positions on
the frictional transmission surfaces F in the respec-tive radial
directions thereof.
Referring particularly to the driving rotation member
14a, it will be seen that in the rota-ting edge surface thereof on
the side opposite to the said Erictional transmission surface F
and in the rotating edge surface opposed thereto of -the driven
bevel gear 12a there are formed alignable pairs of depressions
17 and 18, respectively, preferably in three or more yairs, with
a ball 19 fit-ted in each cavity of the aligned depression pair
17, 18. The depression 17 on the side of the drivinc~ rotation
member 14a is made -to be conical in shape to receive biasing
means constructed as a ball-cam mechanism 20. This urges the
driving rotation member 14a to forcibly bear on to the driven
rotation member 16 as the driven bevel gear 12a is rotated. With
this camming function, the force urging the driving rotation
member 14a to forcibly bear on to the driven rota-tion member 16
set in a desired adjustment pos:ition is proportlonal to the
clrivlng torque of the driving rotation mernber 14a, thus realizing
a stronger compression force at -the higher torque and thereby
achieving reliable transmission of the driving power.
Although the ball-cam mechanism 20 has been described
with reference only to the specific one driving rota-tion member
14a and the mating driven bevel gear 12a, similar ball-cam mech-
anisms 20 are provided for each pair of o-ther driving rotation
members 14b, 14c and the driven bevel gears 12b, 12c. With such
a construction, it is possible to transmit -the driving power from
-the driven bevel gears 12a, 12b, 12c to the output shaft 15 in
a stepless speed-changing manner utilizing the peripheral speed
difference at the adjustably selected different radial positions
on the driving rotation members 14a, 14b, 14c. As is apparent,
each depression 17 may also be elongate in the peripheral direc
tion, rather than the conical shape as already mentioned, result-
ing in substantially the same effect.
Designated in the illus-tration at 21 are compression
springs respectively for urging the driving ro~ation members l~a,
14b, l~c to always make contact with the driven rotation member
16.
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:
Fig. 4 shows the three pairs of the driven bevel gears
12a, 12b, 12c and the driving rotation members 14a, 14b, 14c dis
posed in a modified arrangement. More particularly, the rotation
axes of these three pairs are here spaced one from another a-t an
angular interval larger than a right angle, thereby having the
driving rotation members 14a, 14b, 14c serve to fixedly position
or securely set the driven rotation member 16 and also to suppress
the fluctuating movement of the axis thereof as it is rotated.
It should be noted that -the cam mechanism 20 is not
- 10 limited to a ball-cam as in the embodiment specifically described
. hereinabove, but may be modified. For instance, integral lug
portions may be provided on either part of the driven bevel
gear 12a, 12b, 12c or the driving rotation member 14a, 14b, 14c
and adapted to be :Eitted in respective depressions of the matirlg
other part. rrhis leads to a camming action similar to that des-
cribed hereinabove.
The described embodiments are of course not limited to
use ln a tractor. For example, they may be employed as auxiliary
speed-change apparatus.
:;
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