Planetary gear transmission systems or components – Fluid drive or control of planetary gearing – Fluid controlled mechanical clutch or brake
Reexamination Certificate
2001-11-19
2003-05-06
Wright, Dirk (Department: 3681)
Planetary gear transmission systems or components
Fluid drive or control of planetary gearing
Fluid controlled mechanical clutch or brake
Reexamination Certificate
active
06558284
ABSTRACT:
BACKGROUND OF THE INVENTION
(a) Field of the Invention
The present invention relates to a hydraulic control system for an automatic transmission, and more particularly, to a hydraulic control system for hydraulically controlling a powertrain of a 4-speed automatic transmission that utilizes two one-way clutches.
(b) Description of the Related Art
Conventional automatic transmissions used in vehicles typically include a torque converter and a powertrain realized through a multi-stage gearshift mechanism that is connected to the torque converter. A hydraulic system that selectively operates one of three operational elements of the powertrain (sun gear, planetary carrier and ring gear) according to a driving state of the vehicle is also included.
In designing such an automatic transmission, a design concept and plan are formulated based on a variety of factors such as performance, durability, reliability, ability to be mass-produced, and manufacturing costs. After selecting a design concept, development is pursued in three broad areas of a mechanical section, a hydraulic control system, and an electronic control system.
The powertrain, which falls under the mechanical section category, is realized through a compound planetary gearset. The compound planetary gearset includes at least two simple planetary gearsets and performs control into a required shift stage. The hydraulic control system controls the powertrain. The hydraulic control system includes a pressure regulator for regulating hydraulic pressure generated by operation of an oil pump, a manual/automatic shift controller for forming a shift mode, a hydraulic pressure controller for controlling shift feel and responsiveness to enable smooth shifting, a damper clutch controller for operating a damper clutch of a torque converter, and a hydraulic pressure distributor for supplying suitable hydraulic pressures to friction elements.
The above elements control to which friction element of the powertrain hydraulic pressure will be supplied through solenoid valves that are On/Off and duty-controlled by a transmission control unit. Since in such an automatic transmission the friction elements are controlled to engaged and disengaged states by hydraulic pressure, the generation of shift shock during shifting is unavoidable. There are, nevertheless, ongoing efforts to minimize shift shock.
However, since it is difficult to improve upon the timing at which certain friction elements are controlled to engaged states while others are controlled to disengaged states during the extremely short interval of time provided, there are limits to how much shift shock can be reduced. Further, shift responsiveness is also negatively affected during this operation since momentary control into neutral is being performed. There are efforts to reduce the problems of shift shock and shift delay through the use of one-way clutches.
FIG. 1
shows a schematic view of a conventional automatic transmission powertrain that uses one-way clutches.
Rotational force generated by an engine E is transmitted to an input shaft
2
through a torque converter. The input shaft
2
transmits the received torque to first and second single pinion planetary gearsets
4
and
6
, and shifting is realized through the complementary operation of the first and second single pinion planetary gearsets
4
and
6
. Clutch hook-up, through which output is effected, is realized via a transfer drive gear
10
, which is connected to a planet carrier
8
of the first single pinion planetary gearset
4
.
To provide a clearer description, a sun gear
12
, the planet carrier
8
, and a ring gear
14
of the first single pinion planetary gearset
4
will preceded by the word “first” (e.g., the first sun gear
12
), and a sun gear
16
, a planet carrier
18
, and a ring gear
20
of the second single pinion planetary gearset
6
will be preceded by the word “second”.
In a state where the first planet carrier
8
is fixedly connected to the second ring gear
20
, the first sun gear
12
is connected to the input shaft
2
via a first friction element C
1
, which operates in all forward speeds. Further, the second planet carrier
18
is connected to the input shaft
2
via a second clutch C
2
, which operates in forward third and fourth speeds, and the second sun gear
16
is connected to the input shaft
2
via the third clutch C
3
, which operates in a reverse R range.
The second planet carrier
18
operates as a reaction element through a first brake B
1
and a first one-way clutch F
1
, which are mounted to a transmission housing
22
. The first ring gear
14
is selectively operated together with the second planet carrier
18
through a fourth clutch C
4
and a second one-way clutch F
2
, which are mounted in parallel. Also, the second sun gear
16
operates as a reaction element through a second brake B
2
, which is mounted to the transmission housing
22
.
In the powertrain described above, shifting is realized by operation of the friction elements, which are controlled by the transmission control unit. Referring to
FIG. 2
, the different operative states of the friction elements and an engine brake according to shift range and shift speeds within the ranges (where applicable) are shown. The shifting operation of the powertrain will be described with reference to FIG.
1
and the chart of FIG.
2
.
In a first speed, the first clutch C
1
and the first and second one-way clutches F
1
and F
2
are operated. Accordingly, the first sun gear
12
acts as an input element, and the first ring gear
14
and the second planet carrier
18
act as reaction elements. Shifting into a second speed from the first speed is realized by operation of the second brake B
2
. That is, through the engagement of the second brake B
2
, input is realized through the first sun gear
12
, and the second sun gear
16
acts as a reaction element, thereby realizing shifting into the second speed.
Shifting into the third speed from the second speed is realized by operation of the second clutch C
2
and disengagement of the second brake B
2
. As a result, the first and second single pinion planetary gearsets
4
and
6
are linked such that output that is identical to the input results. Shifting into the fourth speed (i.e., overdrive) from the third speed is realized by the operation of the second brake B
2
such that the second sun gear
16
acts as a reaction element.
To effect shifting into the reverse R range, the third clutch C
3
and the first brake B
1
are controlled to engaged states such that input is realized through the second sun gear
16
and the second planet carrier
18
acts as a reaction element.
In sum and to describe operational states of the friction elements for ranges not yet mentioned, shifting is realized as follows: the first clutch C
1
operates in the first, second and third speeds; the second clutch C
2
operates in the third and fourth speeds; the third clutch C
3
operates in the reverse R range; the fourth clutch C
4
operates in the park P, reverse R, neutral N and low L ranges, and as needed in the first, second and third speeds; the first brake B
1
operates in the park P, reverse R, neutral N and low L ranges; and the second brake B
2
operates in the second and fourth speeds.
With reference to
FIG. 6
, in a hydraulic control system for controlling the powertrain above, a D range pressure supplied from a manual valve
200
is supplied to the first clutch C
1
and first, second and third pressure control valves
202
,
204
and
206
. Also, an L range pressure is supplied to the first pressure control valve
202
, and an R range pressure is supplied to the third clutch C
3
and the first brake B
1
.
In addition, the D range pressure supplied to the first pressure control valve
202
is selectively supplied, according to control by the first solenoid valve
208
, to an operational side of the second brake B
2
, and the L range pressure is supplied to the first brake B
1
in the low L range. A shuttle valve
210
is mounted on a line communicating with the first brake B
1
and the
Cho Jae-Ho
Jang Jae-Duk
Kim Tae-Kyun
Lee Chang-Wook
Lee Jin-Hee
Hyundai Motor Company
Wright Dirk
LandOfFree
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