Machine element or mechanism – Gearing – Interchangeably locked
Reexamination Certificate
2001-10-02
2003-07-15
Estremsky, Sherry (Department: 3681)
Machine element or mechanism
Gearing
Interchangeably locked
C074S336001
Reexamination Certificate
active
06591704
ABSTRACT:
This application is based on and claims priority under 35 U.S.C. §119 with respect to Japanese Patent application No. 2000-302584 filed on Oct. 2, 2000, the entire content of which is incorporated herein by reference.
FIELD OF THE INVENTION
This invention generally relates to a control system applied in a synchromesh type automatic transmission. More specifically, this invention pertains to a control system which controls a shift actuator that drives a sleeve in a synchromesh type automatic transmission.
BACKGROUND OF THE INVENTION
Generally speaking, vehicles such as cars, buses, and the like are driven by a driving power source such as a gasoline engine or an electric motor. The vehicle is provided with a transmission for producing a preferable vehicle driving condition in response to the vehicle running condition.
The transmission is designed to change and select a combination of gears to generate torque or speed. Transmissions are basically categorized into automatic transmissions (AT) or manual transmissions (MT). In the case of automatic transmissions, the transmission automatically selects the combination of gears and the timing for changing the gears.
As shown in
FIG. 5
, manual transmissions (MT) are typically comprised of a counter shaft
51
(input shaft), a plurality of counter gears
52
, a main shaft
53
(output shaft), a plurality of idle gears
54
, and a synchromesh mechanism
55
that includes a sleeve
56
. Driving power is supplied to the counter shaft
51
from the driving source such as the gasoline engine. The counter gears
52
are mounted on the counter shaft
51
. The main shaft
53
outputs the driving power to the wheels via a propeller shaft and other parts. The idle gears
54
are freely rotatably provided on the main shaft
53
and mesh with the counter gears
52
.
In vehicles provided with the known manual transmission (MT), a predetermined speed-change gear is selected based on a manual shift operation performed by the driver. Upon the manual shift operation of a shift lever by the driver, an operating force applied to the shift lever is transmitted to a shift fork shaft via a cable and other parts. The sleeve
56
is moved by the shift fork shaft to effect contact of an idle gear
54
with an output shaft for rotating the output shaft.
Recent developments have led to an automatic manual transmission that is structurally based on the manual transmission (MT). As schematically shown in
FIG. 6
, the manual transmission performs the shift operation by a shift actuator
65
to relieve the driver of the manual operating requirements.
With the automatic manual transmission, the shift lever is operated to transmit the driver's request to an electronic control unit ECU
66
. The ECU
66
controls the timing and the amount of activation of the shift actuator
65
. The output from the shift actuator
65
is transmitted to a shift fork shaft
67
via inner levers
68
. The inner levers
68
are provided between a driving shaft
65
a
that is included in or formed by the shift actuator
65
and the shift fork shaft
67
. The inner levers are formed by an inner lever, an interlock plate, and a shift head.
Immediately after the shift actuator
65
is activated, the fork shaft
67
is axially moved via the inner levers
68
. The sleeve
56
is integrally moved with the shift fork shaft
67
by the engagement between a projecting portion
67
a
formed on the shift fork shaft
67
and an engaging groove
56
a
defined in the circumferential outer surface of the sleeve
56
. According to the aforementioned automatic manual transmission, when the sleeve
56
and the shift fork shaft
67
are moved by the shift actuator
65
via the inner levers
68
while a synchronizing operation is being performed, it is important to determine a shift position, i.e., the driving amount of the shift fork shaft
67
and the sleeve
56
.
As seen in
FIG. 5
, the sleeve
56
included in the synchromesh mechanism
55
is meshed with splines defined in a synchronizer hub
57
which rotates integrally with the main shaft
51
. When the driving force from the shift fork shaft
67
is applied to the sleeve
56
in the rightward direction in
FIG. 5
, the edge surface of a synchronizer key
58
pushes a synchronizer ring
59
against a cone portion (formed at left side in
FIG. 5
) of the idle gear
61
. Accordingly, the rotation of the idle gear
61
is gradually synchronized with the rotation of the sleeve
56
.
According to further movement of the sleeve
56
, the sleeve
56
is disengaged from the synchronizer key
58
, and directly pushes the synchronizer ring
59
. The rotation of the idle gear
61
becomes equal to the rotation of the sleeve
56
so that the idle gear
61
is synchronized with the sleeve
56
.
Hereinafter, the synchronizer ring
59
rotates independently, and does not hinder the idle gear
61
from axially moving. Therefore the sleeve
56
passes through the synchronizer ring
59
and is completely engaged with the idle gear
61
, whereby the sifting operation is completed.
If the moving amount of the sleeve
56
is larger than a required amount, unexpected reactive forces are generated between the members of the synchromesh mechanism
55
(i.e., the sleeve
56
, the synchronizer key
58
and the synchronizer ring
59
) and the idle gear
61
. Thus, one or more parts of the synchromesh mechanism
55
can become worn, thus decreasing the endurance or longevity of the mechanism.
On the other hand, if the moving amount of the sleeve
56
is smaller than the required amount, the reliable synchronizing operation may not be performed.
Accordingly, it is necessary to accurately control the moving amount of the shift fork shaft
67
or the sleeve
56
from the standpoint of the increasing the durability of the synchromesh mechanism
55
while also producing reliable synchronizing operation.
It is possible to provide position sensors adjacent the shift fork shaft
67
of the sleeve
56
when the automatic manual transmission is manufactured (and assembled) for detecting the moving amount of the shift fork shaft
67
. However, the sleeve
56
and the shift fork shaft
67
are positioned far inside the housing of the synchromesh-type automatic transmission and so it is difficult to provide the position sensors adjacent the sleeve
56
and the fork
67
. Thus, from the standpoint of manufacturing cost and manufacturing time, it may be unreasonable or unfeasible to provide position sensors adjacent the sleeve
56
and the shift fork shaft
67
.
In an attempt to overcome the aforementioned drawback, the position sensor
63
can be disposed adjacent the driving shaft
65
a
to detect the moving amount of the driving shaft
65
a
. The moving amount of the driving shaft
65
a
detected by the position sensor
63
can then be inputted to the ECU
66
, with the ECU
66
then regulating the moving amount of the fork
67
and the sleeve
56
.
However, with this alternative placement of the position sensor, the moving amount of the shift fork shaft
67
, i.e., the sleeve
56
, cannot be accurately detected to a sufficient degree because the inner levers
68
disposed between the driving shaft
65
a
and the shift fork shaft
67
deflect under the driving force and this deflection exerts a bad influence upon the moving amount of the sleeve
56
.
Therefore the moving amount of the driving shaft
65
a
detected by the position sensor
63
will differ from the actual moving amount of the shift fork shaft
67
. Owing to the difference between the detected moving amount and the actual moving amount, the control of the moving amounts of the shift fork shaft
67
and the sleeve
56
for purposes of properly stopping the shift fork shaft
67
and the sleeve
56
cannot be accurately ascertained. Thus, various members forming the synchromesh mechanism can become worn and reliable synchronizing operation may not be performed.
SUMMARY OF THE INVENTION
A shift actuating control system for a synchromesh-type automatic transmission includes a shift actuator having a driving portion activated
Aoyama Yoshiyuki
Choshi Ryuji
Ichikawa Yoshihiro
Kamiya Mitsutoshi
Miyazaki Takeshige
Aisin Ai Co., Ltd.
Estremsky Sherry
LandOfFree
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