Note: Descriptions are shown in the official language in which they were submitted.
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TRANSMISSION GEAR SHIFT SYSTEM
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates to a transmission gear shift system in
which a shift select shaft supported on a transmission case is maintained in a
central select position among three select positions in the axial direction by
means of the resilient force of a select spring.
Description of the Prior Art
A transmission gear shift system is known in Japanese Patent
Publication No. 2629871. The shift select shaft of this gear shift system is
placed between a shift lever which is operated by the driver and shift forks
for
selectively establishing a plurality of gear shift stages and moves in the
axial
direction in operative connection with a select operation of the shift lever
and
rotates according to a shift operation of the shift lever. The shift select
shaft
can stop in three select positions by moving in the axial direction, and it is
forced by two select springs to be maintained in a central select position
when
the shift lever is in a neutral position. When the shift select shaft moves in
one
direction from the central select position, one of the select springs is
compressed thus generating a resilient force for returning the shift select
shaft
to the central select position, and when the shift select shaft moves in the
other
direction from the central select position, the other select spring is
compressed
thus generating a resilient force for returning the shift select shaft to the
central
select position.
However, since two springs are needed to maintain the shift select shaft
in the central select position in the prior art, there are the problems that
not only
does the number of parts increase but also the length of the shift select
shaft
increases in order to provide space for placing the select springs.
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SUMMARY OF THE INVENTION
The present invention has been carried out in view of the above-
mentioned circumstances, and it is an objective of the present invention to
both
reduce the number of select springs used for maintaining the shift select
shaft in
the central select position and to shorten the overall length of the shift
select
shaft.
In order to achieve the objective, in accordance with the present
invention a transmission gear shift system is provided which is a transmission
gear shift system for selectively establishing a plurality of gear shift
stages in
which shift forks are operated by means of a shift select shaft supported on a
transmission case, being moved in the axial direction according to a select
operation of a shift lever and being moved in a circular manner according to a
shift operation of the change lever. The shift select shaft is maintained in a
central select position among three select positions in the axial direction by
means of the resilient force of a select spring. A first spring seat and a
second
spring seat are supported in a slidable manner between a first stopper surface
and a second stopper surface which are provided on the shift select shaft with
a
gap between them in the axial direction. The inner surfaces in the axial
direction of the first and second spring seats are forced by the select spring
in
the direction in which they move away from each other so as to come into
contact with the first and second stopper surfaces respectively, and the outer
surfaces in the axial direction of the first and second spring seats are
supported
on first and second support surfaces respectively provided on the transmission
case.
In accordance with the above-mentioned arrangement, when the shift
select shaft is moved in one direction from the neutral position, since the
first
spring seat which is retained by the first stopper surface, moves together
with
the shift select shaft to move away from the first support surface and
compresses the select spring against the second spring seat which is supported
on the second support surface, and moves relative to the shift select shaft,
the
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shift select shaft is forced towards the neutral position by means of the
resilient
force of the select spring. When the shift select shaft is moved in the other
direction from the neutral position, since the second spring seat which is
retained by the second stopper surface moves together with the shift select
shaft
so as to move away from the second support surface and compresses the select
spring against the first spring seat which is supported on the first support
surface and moves relative to the shift select shaft, the shift select shaft
is
forced towards the neutral position by means of the resilient force of the
select
spring.
Thus, since the shift select shaft can be forced from either direction to
the neutral position by means of one select spring, not only can the number of
select springs be reduced to a minimum, but also the overall length of the
shift
select shaft can be shortened by reducing the space required for placing the
select spring.
Furthermore, in accordance with the present invention, a transmission
gear shift system is provided wherein the first and second spring seats and
the
select spring are housed inside a breather chamber provided in the
transmission
case, and the first and second support surfaces are formed on the inner wall
of
the breather chamber.
In accordance with the above-mentioned arrangement, since the first and
second spring seats and the select spring are housed by effectively using the
internal space of the breather chamber provided in the transmission case, the
space in which the first and second spring seats and the select spring are
placed,
can be minimized. Moreover, since the first and second support surfaces for
supporting the first and second spring seats are formed on the inner wall of
the
breather chamber, special members for forming the first and second support
surfaces are unnecessary and thus the number of parts can be reduced.
BRIEF DESCRIPTION OF THE DRAWINGS
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Fig. 1 is a vertical cross-sectional view of a manual transmission for a
vehicle.
Fig. 2 is a diagram showing the change patterns of a change lever.
Fig. 3 is a horizontal cross-sectional view of an essential part of the
manual transmission for a vehicle.
Fig. 4 is a magnified view of an essential part of Fig. 3 (third speed -
fourth speed select position).
Fig. 5 is a cross-sectional view at line 5 - 5 in Fig. 4.
Fig. 6 is a view for explaining an action corresponding to Fig. 4 (fifth
speed - reverse select position).
Fig. 7 is a view for explaining an action corresponding to Fig. 4 (first
speed - second speed select position).
Fig. 8 is a view taken in the direction of an arrow 8 in Fig. 3.
Fig. 9 is a cross-sectional view at line 9 -9 in Fig. 8.
Fig. 10 is a rilagnified view of an essential part of Fig. 8 (neutral
position).
Fig. 11 is a view for explaining an action corresponding to Fig. 10
(reverse position).
Fig. 12 is a view for explaining an action corresponding to Fig. 10 (fifth
speed position).
Fig. 13 is a view from line 13 - 13 in Fig. 10.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
As shown in Fig. 1 a transmission case 11 for a manual transmission M
for vehicle with five forward speeds and one reverse speed, comprises a case
left half 12 and a case right half 13 which are separated on a dividing plane
extending in the longitudinal direction of the vehicle, and a gear shift
clutch C
is housed in a clutch chamber 14 formed on the side surface of the case left
half
12 on the side of the engine E. The right and left ends of a main shaft Sm
connected to the engine E via the gear shift clutch C, are supported by means
of
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ball bearings 16 and 15 on the case right half 13 and the case left half 12
respectively, and the right and left ends of a counter shaft Sc positioned in
parallel to the main shaft Sm are supported by ball bearings 18 and roller
bearings 17 on the case right half 13 and the case left half 12 respectively.
A
differential gear D which distributes the output from the counter shaft Sc to
the
right and left axles 19, 19 is supported by a pair of right and left ball
bearings
21, 20 on the case right half 13 and the case left half 12 respectively.
The gear shift clutch C housed inside the clutch chamber 14, comprises a
clutch wheel 22 which is connected to the right end of the crankshaft of the
engine E and a clutch disc 24, connected to the left end of the main shaft Sm
via a damper 23. They are normally engaged by clamping the facings 27 of the
clutch disc 24 between a pressure plate 26 and the clutch wheel 22 by means of
the resilient force of a diaphragm spring 25 and the engagement is released
during gear shifting by means of a release fork 28 pushing a release bearing
29
leftwards.
On the main shaft Sm are secured a main first speed gear 31, a main
second speed gear 32, a main third speed gear 33, a main fourth speed gear 34
and a main fifth speed gear 35, which are all supported in a relatively
rotatable
manner. On the counter shaft Sc, a counter first speed gear 36 and a counter
second speed gear 37 which mesh with the main first speed gear 31 and main
second speed gear 32, are supported in a relatively rotatable manner. A
counter
third speed gear 38, a counter fourth speed gear 39 and a counter fifth speed
gear 40 are also secured with counter shaft Sc and mesh with the main third
speed gear 33, main fourth speed gear 34 and main fifth speed gear 35
respectively.
The right and left ends of a reverse idle shaft Sr are supported on the
case right half 13 and the case left half 12, and a reverse idle gear 41 which
is
supported on the reverse idle shaft Sr, in a laterally slidable manner, can
mesh
with a main reverse gear 42 which is secured on the main shaft Sm as well as
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with a counter reverse gear 43 which is supported on the counter shaft Sc in a
relatively rotatable manner.
By moving a sleeve 45 of a first speed - second speed synchronous
mechanism S1 leftwards by means of a first speed - second speed shift fork 44,
the counter first speed gear 36 is connected to the counter shaft Sc to
establish a
first speed gear shift stage, and by moving the sleeve 45 of the first speed -
second speed synchronous mechanism S1 rightwards by means of the first
speed - second speed shift fork 44, the counter second speed gear 37 is
connected to the counter shaft Sc to establish a second speed gear shift
stage.
By moving a sleeve 47 of a third speed - fourth speed synchronous mechanism
S2 leftwards by means of a third speed - fourth speed shift fork 46 the main
third speed gear 33 is connected to the main shaft Sm to establish a third
speed
gear shift stage, and by moving the sleeve 47 of the third speed - fourth
speed
synchronous mechanism S2 rightwards by means of the third speed - fourth
speed shift fork 46, the main fourth speed gear 34 is connected to the main
shaft Sm to establish a fourth speed gear shift stage.
By moving a sleeve 49 of a fifth speed synchronous mechanism S3
leftwards by means of a fifth speed shift fork 48, the main fifth speed gear
35 is
connected to the main shaft Sm to establish a fifth speed gear shift stage.
When
the sleeve 49 of the fifth speed synchronous mechanism S3 is moved
rightwards by means of the fifth speed shift fork 48, a reverse shift fork 50
which supports the reverse idle gear 41 in a rotatable manner, moves leftwards
in operative connection with the fifth speed shift fork 48, and the reverse
idle
gear 41 meshes with the main reverse gear 42 and the counter reverse gear 43
provided on the sleeve 45 of the first speed - second speed synchronous
mechanism S1, to establish a reverse gear shift stage.
The first speed - second speed synchronous mechanism S1, the third
speed - fourth speed synchronous mechanism S2 and the fifth speed
synchronous mechanism S3 are known and they carry out a synchronous action
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by means of the frictional force between a blocking ring and a synchro cone
due to the lateral movement of the sleeves 45, 47 and 49.
When the first to fifth gear shift stage or reverse gear shift stage is thus
established, rotation of the counter shaft Sc is transmitted to the
differential
gear D via a final drive gear 51 and a final driven gear 52 thus driving the
right
and left axles 19, 19.
The structure of a shifting system for establishing the first speed to fifth
speed gear shift stages and the reverse gear shift stage is explained below by
reference to Fig. 2 to Fig. 12.
Fig. 2 shows an operational pattern of a shift lever L of the shifting
system; Pl denotes a first speed - second speed select position, P2 denotes a
third speed - fourth speed select position (neutral position), P3 denotes a
fifth
speed - reverse select position, , ~ and ~ which are located on either side of
the first speed - second speed select position P1, denote a first speed
position
and a second speed position respectively, ~ and ~ which are located on either
side of the third speed - fourth speed select position P2, denote a third
speed
position and a fourth speed position respectively, and ~ and R which are
located on either side of the fifth speed - reverse select position P3, denote
a
fifth speed position and a reverse position respectively. The arrow SE in the
figure illustrates the directions of the select operation of the shift lever L
and
the arrow SI in the figure illustrates the directions of the shift operation
of the
shift lever L.
As shown in Fig. 3 to Fig. 5, a dish-shaped indentation 13a is formed on
the upper part of the case right half 13 of the transmission case 11, and by
connecting a cover member 57 by means of six bolts 56 to cover the opening of
the indentation 13a, a breather chamber 58 is formed between the cover
member 57 and the indentation 13a. A shift select shaft 59 is supported in a
rotatably and longitudinally movable manner in a guide hole 57a formed in the
center of the cover member 57 and a guide hole 13b formed inside the case
right half 13.
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A notch 59a is formed on the upper end of the shift select shaft 59 which
extends externally from the cover member 57 via a sealing member 60, and a
select lever 61 engages with the notch 59a. The select lever 61 swings
vertically in operative connection with the select operation (operation in the
direction of the arrow SE in Fig. 2) of the shift lever L and can move the
shift
select shaft 59 between the third speed - fourth speed select position shown
in
Fig. 4, the fifth speed - reverse select position (see Fig. 6), which is
upwards
relative to the third speed - fourth speed select position, and the first
speed -
second speed select position (Fig. 7), which is downwards relative to the
third
speed - fourth speed select position.
A shift lever 62 is fixed beneath the notch 59a of the shift select shaft
59, and the shift lever 62 rotates in lateral directions in operative
connection
with the shift operation (operation in the direction of the arrow SI in Fig.
2) of
the shift lever L. When the shift lever L is in the first speed - second speed
select position P1, the third speed - fourth speed select position P2 or the
fifth
speed - reverse select position P3, the shift select shaft 59 is in the
neutral
position; when the shift lever L is operated to move to the first speed
position
0, the third speed position ~3 or the fifth speed position ~, the shift select
shaft 59 rotates leftwards from the neutral position, and when the shift lever
L
is operated to move to the second speed position 0, the fourth speed position
~ or the reverse position R, the shift select shaft 59 rotates rightwards from
the
neutral position. The shift select shaft 59 can be stopped at nodal points in
the
three rotational positions by means of a detent mechanism 63 (Fig. 8).
A shift arm 64 is fixed by a fixing pin 65 on the shift select shaft 59
which extends inside the case right half 13, and an interlock plate 66 is also
supported on the shaft in a relatively rotatable manner such that the shift
arm 64
is vertically sandwiched by the plate 64. The interlock plate 66 comprises a
pair of upper and lower lock claws 66a, 66b, and the pair of lock claws 66a,
66b face the top and bottom respectively of a drive part 64a formed at the
forward end of the shift arm 64. The interlock plate 66 comprises a guide
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channel 66c which extends in a direction perpendicular to the shift select
shaft
59 and a rotation stopping pin 67 fixed on the case right half 13 engages with
the guide channel 66c.
Therefore, when the shift select shaft 59 moves vertically, the shift arm
64 and the interlock plate 66 ascend and descend together, but when the shift
select shaft 59 rotates, the shift arm 64 rotates together with the shift
select
shaft 59, but rotation of the interlock plate 66 is restricted by engagement
of the
guide channel 66c with the rotation stopping pin 67.
The shift select shaft 59 has a lower half with a smaller diameter beneath
a step-shaped first stopper surface 59b which is formed almost at its center
in
the longitudinal direction, and the upper surface of the inner circumference
of a
first spring seat 68 which fits in a slidable manner on the lower half of the
shift
select shaft 59 having the smaller diameter, engages with the first stopper
surface 59b from the lower side, whereas the upper surface of the outer
circumference of the first spring seat 68 is in contact with a first support
surface
57b which is a lower surface of the cover member 57. With regard to a disc-
shaped second spring seat 69 which is placed beneath the first spring seat 68
and fits in a slidable manner on the shift select shaft 59, the lower surface
of the
inner circumference thereof engages with a second stopper surface 66d which is
formed on the upper surface of the interlock plate 66. A roughly cross-shaped
opening 13c is formed on the bottom wall of the indentation 13a of the case
right half 13, and the lower surface of the outer circumference of the second
spring seat 69 is supported by four step-shaped second supporting surfaces 13d
which are formed on the edge of the opening 13c. The upper and lower ends of
a select spring 70 are supported between the lower surface of the first spring
seat 68 and the upper surface of the second spring seat 69.
Thus, when the shift select shaft 59 is in the three speed - fourth speed
select position shown in Fig. 4, the upper surface of the inner circumference
of
the first spring seat 68 and the lower surface of the inner circumference of
the
second spring seat 69 which are supported in a slidable manner on the shift
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select shaft 59 and are forced by the select spring 70 in a direction such
that
they move apart from each other, are resiliently in contact with both the
first
stopper surface 59b of the shift select shaft 59 and with the second stopper
surface 66d formed on the upper surface of the interlock plate 66, and the
upper
surface of the outer circumference of the first spring seat 68 and the lower
surface of the outer circumference of the second spring seat 69 are supported
by
being in contact with the first support surface 57b of the cover member 57 and
with the second support surfaces 13d of the indentation 13a respectively, and
the shift select shaft 59 thus stops in a stable manner at the third speed -
fourth
speed select position.
When the shift select shaft 59 moves upwards from the above-mentioned
state to the fifth speed - reverse select position (Fig. 6), since the second
spring
seat 69 which is pressed by the second stopper surface 66d of the interlock
plate
66 which is integral with the shift select shaft 59, ascends while leaving the
first
spring seat 68 which is latched onto the first support surface 57b of the
cover
member 57 at its original position, the select spring 70 is compressed,
generating a force to return the shift select shaft 59 to the third speed -
fourth
speed select position.
On the other hand, when the shift select shaft 59 moves downwards
from the third speed - fourth speed position to the first speed - second speed
select position (Fig. 7), since the first spring seat 68 which is pressed by
the
first stopper surface 59b of the shift select shaft 59, descends while leaving
the
second spring seat 69 which is latched onto the second support surfaces 13d of
the opening 13c, at its original position, the select spring 70 is compressed,
generating a force to return the shift select shaft 59 to the third speed -
fourth
speed select position.
As hereinbefore described, since the shift select shaft 59 can be centered
by forcing it to the third speed - fourth speed select position, which is the
neutral position, by means of just one select spring 70, in comparison with
the
case in which the shift select shaft 59 is forced upwards and downwards by
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means of two springs, the number of parts and the cost can be reduced.
Moreover, when two springs are supported on the shift select shaft 59, the
length of the shift select shaft 59 inevitably increases, but by using only
one
spring it is possible to reduce the overall length of the shift select shaft
59.
The internal space of the breather chamber 58 which is defined by the
indentation 13a of the case right half 13 and the cover member 57 is connected
to the internal space of the transmission case 11 via four through holes 71
which are formed between the inner circumference of the opening 13c and the
outer circumference of the second spring seat 69 and is connected to the
outside
of the transmission case 11 via a breather tube 73 provided on the forward end
of a breather pipe 72, which is integral with the cover member 57.
A subassembly A is formed by assembling the shift select shaft 59, the
first spring seat 68, the second spring seat 69, the select spring 70, the
shift arm
64, the fixing pin 65 and the interlock plate 66 beforehand, onto the cover
member 57, and by inserting this subassembly A into the opening 13c through
the indentation 13a of the case right half 13 during assembly. Thus, the
assembly operation can be outstandingly enhanced.
Since the breather chamber 58 is defined by the indentation 13a of the
case right half 13 and the cover member 57, and the first spring seat 68, the
second spring seat 69 and the select spring 70 are housed inside the breather
chamber 58, a single space functions as both the space forming the breather
chamber 58 and the space for housing the first spring seat 68, the second
spring
seat 69 and the select spring 70, and it is possible to avoid an increase in
the
size of the transmission case 11 and the number of parts. Moreover, since the
breather chamber 58 is connected to the internal space of the transmission
case
11 via the four through holes 71 which are formed between the inner
circumference of the opening 13c and the outer circumference of the second
spring seat 69, and the shift arm 64 and the interlock plate 66 are positioned
so
as to adjoin each other beneath the through holes 71, oil can be effectively
prevented from entering the breather chamber 58 due to the labyrinth effect.
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As shown in Fig. 4 and Fig. 8, the two ends of a first speed - second
speed shift rod 76 comprising the first speed - second speed shift fork 44,
the
two ends of a third speed - fourth speed shift rod 77 comprising the third
speed
- fourth speed shift fork 46 and the two ends of a fifth speed - reverse shift
rod
78 comprising the fifth speed shift fork 48 are supported in a slidable manner
on the case left half 12 and the case right half 13 respectively. A first
speed -
second speed shift piece 79, a third speed - fourth speed shift piece 80 and a
fifth speed - reverse shift piece 81 are fixed on the first speed - second
speed
shift rod 76, the third speed - fourth speed shift rod 77 and the fifth speed -
reverse shift rod 78 respectively, and notches 79a, 80a, 81a formed at the
forward ends of the three shift pieces 79, 80, 81 respectively are aligned
vertically so that they can selectively engage with the drive part 64a
provided at
the forward end of the shift arm 64.
Thus, when the shift select shaft 59 is in the third speed - fourth speed
select position as shown in Fig. 4, since the drive part 64a of the shift arm
64
engages with the notch 80a of the third speed - fourth speed shift piece 80,
the
third speed - fourth speed shift rod 77 can be driven together with the third
speed - fourth speed shift piece 80 from the neutral position to the third
speed
position or the fourth speed position by a circular movement of the shift
select
shaft 59. At this stage, the locking claw 66b on the lower side of the
interlock
plate 66 engages with the notch 79a of the first speed - second speed shift
piece
79, and the locking claw 66a on the upper side of the interlock plate 66
engages
with the notch 81a of the fifth speed - reverse shift piece 81, and thus
malfunctions of the first speed - second speed shift piece 79 and the fifth
speed
-reverse shift piece 81 can be prevented.
As shown in Fig. 7, when the shift select shaft 59 is moved to the first
speed - second speed select position which is beneath the third speed - fourth
speed select position, since the drive part 64a of the shift arm 64 engages
with
the notch 79a of the first speed - second speed shift piece 79, the first
speed -
second speed shift rod 76 can be driven together with the first speed - second
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speed piece 79 from the neutral position to the first speed position or the
second
speed position by a circular movement of the shift select shaft 59. At this
stage,
the locking claw 66a on the upper side of the interlock plate 66 engages with
the notch 81a of the fifth speed - reverse shift piece 81 and the notch 80a of
the
third speed - fourth speed shift piece 80, and thus malfunctions of the fifth
speed - reverse shift piece 81 and the third speed - fourth speed shift piece
80
can be prevented.
As shown in Fig. 6, when the shift select shaft 59 is moved to the fifth
speed - reverse select position which is above the third speed - fourth speed
select position, since the drive part 64a of the shift arm 64 engages with the
notch 81a of the fifth speed - reverse shift piece 81, the fifth speed -
reverse
shift rod 78 can be driven together with the fifth speed - reverse shift piece
81
from the neutral position to the fifth speed position or the reverse position
by a
circular movement of the shift select shaft 59. At this stage, the locking
claw
66b on the lower side of the interlock plate 66 engages with the notch 79a of
the first speed - second speed shift piece 79 and the notch 80a of the third
speed
- fourth speed shift piece 80, and thus malfunctions of the first speed -
second
speed shift piece 79 and the third speed - fourth speed shift piece 80 can be
prevented.
As shown in Fig. 8, a detent mechanism 82 is provided in order to stop
the first speed - second speed shift rod 76 at nodal points so as to
correspond to
the first speed - second speed select position, the first speed position and
the
second speed position. Moreover, a detent mechanism 83 is provided in order
to stop the third speed - fourth speed shift rod 77 at nodal points so as to
correspond to the third speed - fourth speed select position, the third speed
position and the fourth speed position.
As shown in Fig. 8 to Fig. 10, a bracket 85 is fixed to the inner surface
of the case right half 13 by means of two bolts 86, 86, and the reverse shift
fork
50 is supported in a swingable manner on the bracket 85 via a fulcrum pin 87.
A notch SOa which is interposed between the two side surfaces of the reverse
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idle gear 41 is formed at one end of the reverse shift fork 50 and a driven
cam
face ~ for reverse shift, a driven cam face h for neutral return and a driven
cam
face ~ for neutral hold are formed continuously at the other end, relative to
the
fulcrum pin 87, of the reverse shift fork 50. A drive cam face ~ for reverse
shift which can come into contact with the driven cam face ~ for reverse shift
and a drive cam face ~ for neutral return which can come into contact with the
driven cam face 1i for neutral return and the driven cam face ~ for neutral
hold,
are formed continuously at the forward end of the drive cam 88, which is
formed integrally with the fifth speed - reverse shift piece 81.
A detent mechanism 84 for stopping the fifth speed - reverse shift rod 78
at nodal points to correspond to the fifth speed - reverse select position,
the
fifth speed position and the reverse position is provided at the forward end
of
an arm 85a which extends integrally from the bracket 85 supporting the reverse
shift fork 50. As shown in Fig. 9, the detent mechanism 84 comprises a detent
ball 84b which is urged by a detent spring 84a, and this detent ball 84b can
selectively engage with three indentations 81b to 81d (Fig. 10 to Fig. 12)
which
are formed on the fifth speed - reverse shift piece 81.
Thus, when the fifth speed - reverse shift piece 81 is at the neutral
position as shown in Fig. 10, the drive cam face ~ for reverse shift and the
drive
cam face ~ for neutral return of the drive cam 88 of the fifth speed - reverse
shift piece 81 are in contact with the driven cam face ~ for reverse shift and
the
driven cam face ~ for neutral hold of the reverse shift fork 50 respectively,
and
the reverse idle gear 41 is at the neutral position which is at the right end
on the
reverse idle shaft Sr and is in contact with the end face 13i of the case
right half
13. Therefore, even if the reverse idle gear 41 attempts to move leftwards so
as
to move away from the end face 13i of the case right half 13, the leftward
movement of the reverse idle gear 41 is prevented by the contact between the
drive cam face ~ for neutral return of the drive cam 88 and the driven cam
face
~ for neutral hold of the reverse shift fork 50.
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As shown in Fig. 12, when the fifth speed - reverse shift rod 78 moves
leftwards from the neutral position to the fifth speed position in order to
establish a fifth speed gear shift stage, the main fifth speed gear 35 is
linked to
the main shaft Sm by the fifth speed shift fork 48, which is provided on the
fifth
speed - reverse shift rod 78, to establish the fifth speed gear shift stage
(Fig. 1).
At this stage, the drive cam face ~ for neutral return of the drive cam 88
which
operates integrally with the fifth speed - reverse shift rod 78 moves to slide
along the driven cam face ~ for neutral hold of the reverse shift fork 50, and
the
reverse shift fork 50 remains stopped at the neutral position. In this case
also,
even if the reverse idle gear 41 attempts to move leftwards so as to move away
from the end face 13i of the case right half 13, the leftward movement of the
reverse idle gear 41 is prevented by the contact between the drive cam face ~
for neutral return of the drive cam 88 and the driven cam face ~ for neutral
hold
of the reverse shift fork 50.
When the fifth speed - reverse shift rod 78 moves rightwards from the
fifth position (Fig. 11) to the neutral position (Fig. 10) in order to release
an
established fifth gear shift stage, since the drive cam face ~ for neutral
return of
the drive cam 88 moves to slide along the driven cam face ~ for neutral hold
of
the reverse shift fork 50, the reverse shift fork 50 remains stopped at the
neutral
position.
As shown in Fig. 11, when the fifth speed - reverse shift rod 78 moves
rightwards from the neutral position to the reverse position in order to
establish
a reverse gear shift stage, the fifth speed shift fork 48 provided on the
fifth
speed - reverse shift rod 78 slips rightwards (Fig. 1). At the same time, the
drive cam face ~ for reverse shift of the drive cam 88 which operates
integrally
with the fifth speed - reverse shift rod 78 presses against the driven cam
face ~
for reverse shift of the reverse shift fork 50, swinging the reverse shift
fork 50
anticlockwise. As a result, the reverse shift fork 50 slides the reverse idle
gear
41 leftwards along the reverse idle shaft Sr, and the reverse idle gear 41
meshes
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with the main reverse gear 42 and the counter reverse gear 43 to establish a
reverse gear shift stage.
In this state, the left end face of the reverse idle gear 41 is in contact
with the end face 12b of the case left half 12, and even if the reverse idle
gear
41 attempts to move rightwards therefrom, the rightward movement of the
reverse idle gear 41 is prevented by the contact between the drive cam face ~
for reverse shift of the drive cam 88 and the driven cam face ~ for reverse
shift
of the reverse shift fork 50.
When the fifth speed - reverse shift rod 78 moves leftwards from the
reverse position (Fig. 12) to the neutral position (Fig. 10) in order to
release an
established reverse gear shift stage, the drive cam face a for neutral return
of
the drive cam 88 presses against the driven cam face h for neutral return of
the
reverse shift fork 50, swinging the reverse shift fork 50 clockwise. As a
result,
the reverse shift fork 50 slides the reverse idle gear 41 rightwards along the
reverse idle shaft Sr, and the reverse idle gear 41 moves away from the main
reverse gear 42 and the counter reverse gear 43 to release the established
reverse gear shift stage.
As is clear from Fig. 10 and Fig. 13, with regard to the reverse idle shaft
Sr, its left end is held by being fitted in a shaft support hole 12a which is
formed in the case left half 12 and its right end is held by being fitted in a
shaft
support hole 13e which is formed in the case right half 13. The inner wall
surface of the shaft support hole 13e of the case right half 13 is not closed
in
the circumferential direction, and a portion thereof opens in the direction
facing
the main shaft Sm via a notch. That is to say, a shaft support surface 13f of
the
shaft support hole 13e which supports the reverse idle shaft Sr comprises a
major arc having an angle of about 250°, and a portion of the outer
circumference of the reverse idle shaft Sr is exposed to the internal space of
the
case right half 13 through an opening 13g comprising a minor arc having an
angle of about 110°. Thus, even when a portion of the inner wall
surface of the
shaft support hole 13e is lacking, if the shaft support surface 13f of the
shaft
CA 02323384 2000-10-17
17
support hole 13e has a central angle of 180° or more, there is no
possibility of
the reverse idle shaft Sr dropping from the shaft support hole 13e.
As shown by the broken line in Fig. 8, if the shaft support hole 13e is
made in the form of a closed pocket, since an inner wall surface 13h of the
case
right half 13 projects into the inside of the transmission case 11, there is a
possibility of the inner wall surface 13h interfering with a gear provided on
the
main shaft Sm, and if the distance between the reverse idle shaft Sr and the
main shaft Sm is increased in order to avoid the interference, there is the
problem that the size of the transmission case 11 increases. However, by
cutting a portion of the shaft support hole 13e for the reverse idle shaft Sr
as in
the present embodiment, the size of the transmission case 11 can be reduced by
allowing the reverse idle shaft Sr to approach the main shaft Sm as closely as
possible without providing a special member for supporting the reverse idle
shaft Sr or carrying out special processing.
Although a manual transmission M is illustrated in the embodiment, the
present invention can be applied to an automatic transmission in which the
shift/select operation is carried out by an actuator.
The present invention may be embodied in other specific forms without
departing from the spirit or essential characteristics thereof. The presently
disclosed embodiment is therefore to be considered in all respects as
illustrative
and not restrictive, the scope of the invention being indicated by the
appended
claims, rather than the foregoing description, and all changes which come
within
the meaning and range of equivalency of the claims are, therefore, to be
embraced therein.
