Planetary gear transmission systems or components – Fluid drive or control of planetary gearing – Fluid controlled mechanical clutch or brake
Reexamination Certificate
2002-08-21
2003-08-26
Marmor, Charles A (Department: 3681)
Planetary gear transmission systems or components
Fluid drive or control of planetary gearing
Fluid controlled mechanical clutch or brake
C475S120000, C475S122000, C475S127000
Reexamination Certificate
active
06609991
ABSTRACT:
BACKGROUND OF THE INVENTION
1. 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 applied to a powertrain utilizing two single pinion planetary gearsets, four clutches, two one-way clutches, and two brakes to obtain four forward speeds and one reverse speed.
2. Description of the Related Art
Conventional automatic transmissions used in vehicles include a torque converter, a multi-stage gear shift mechanism connected to the torque converter, and a plurality of friction elements actuated by hydraulic pressure for selecting one of the gear stages of the gear shift mechanism, the gear shift mechanism being realized through a planetary gearset. The friction elements are controlled to engaged and disengaged states by a hydraulic control system, which controls pressure generated by an oil pump, to change shift ratios of the planetary gearset.
The friction elements are selectively operated by a plurality of valves, which undergo port conversion to change the flow of hydraulic pressure, and actuators supplying hydraulic pressure to the valves. Further, a manual valve, indexed with a driver-operated shift selector to realize port conversion, is connected to a plurality of lines to supply hydraulic pressure from the oil pump to each valve and actuator.
Solenoid valves are operated to ON and OFF states in different combinations to realize control into the various speeds and shift modes. That is, as described above, the solenoid valves are operated to ON and OFF states such that the supply of hydraulic pressure to the valves is controlled. This, in turn, controls the supply of hydraulic pressure to specific friction elements to control the same, thereby ultimately controlling the multi-stage gear shift mechanism for control into the different shift speeds and modes.
However, in the prior art hydraulic control system, an engine brake is applied frequently at unsuitable times such that drive performance is reduced. Also, fail-safe means in case the transmission malfunctions is not provided.
SUMMARY OF THE INVENTION
The present invention has been made in an effort to solve the above problems.
It is an object of the present invention to provide a hydraulic control system applied to a powertrain utilizing two single pinion planetary gearsets, four clutches, two one-way clutches, and two brakes to obtain four forward speeds and one reverse speed, the hydraulic control system operating an engine brake at only a high stage of each range such that drive performance is improved and which provides a fail-safe mode by holding a fourth speed in a drive D range and a third speed in a low D2 range such that drive performance is improved.
To achieve the above object, the present invention provides a hydraulic control system in which hydraulic pressure generated by the operation of an oil pump is supplied to pressure/damper clutch control means, pressure reducing means, and shift control means, pressure reduced by the pressure reducing means and hydraulic pressure supplied as a result of port conversion of the shift control means being supplied to hydraulic pressure control means, and hydraulic pressure controlled by the hydraulic pressure control means being supplied to hydraulic pressure distribution means and directly to selective friction elements to engage the same.
The shift control means includes a manual valve which is indexed with a driver-controlled select lever to supply hydraulic pressure through five different lines to the hydraulic pressure control means, the hydraulic pressure distribution means, and the friction elements, the hydraulic pressure control means includes first, second and third pressure control valves which are controlled by pressure controlled by first, second and third solenoid valves, the first pressure control valve controlling hydraulic pressure to be directly supplied to a first clutch operating in forward shift modes, the second pressure control valve controlling hydraulic pressure to be supplied to a second brake operating in second and fourth speeds of a drive D range, and the third pressure control valve controlling hydraulic pressure to be supplied to a first brake operating in a low L range and a reverse R range and to a third clutch operating in third and fourth speeds of the drive D range such that hydraulic pressure is supplied to two valves of the hydraulic pressure distribution means.
The hydraulic pressure distribution means comprises a low control valve for supplying L-range pressure to another valve as control pressure in the low L range such that control pressure of the third pressure control valve is supplied to the first brake; an N-R control valve for supplying reverse pressure to the first brake by reduced pressure supplied via the pressure control valve when shifting into the reverse R range; a line pressure control switch valve controlled by D-range pressure and hydraulic pressure supplied to a second clutch, the line pressure control switch valve supplying a part of the hydraulic pressure supplied to the second clutch to a pressure regulator valve; a first fail-safe valve controlled by control pressure supplied from the low control valve and from the second pressure control valve, the first fail-safe valve undergoing port conversion to supply hydraulic pressure supplied from the third pressure control valve to the second clutch in the third and fourth speeds of the drive D range, and hydraulic pressure supplied from the third pressure control valve to the first brake in the low L range; a second fail-safe valve controlled by reverse pressure, hydraulic pressure supplied to a fourth clutch, and hydraulic pressure supplied to the third clutch, the second fail-safe valve supplying hydraulic pressure supplied from the second pressure control valve to the second brake in the second and fourth speeds of the drive D range; and an engine brake control switch valve for supplying D-range pressure to the fourth clutch in the first and third speeds of the drive D range.
According to a feature of the present invention, the manual valve is connected to a reverse R range pressure line directly communicated with the third clutch; a forward pressure line connected to the pressure regulator valve; a drive D range pressure line connected to the first, second and third pressure control valves, the second fail-safe valve, and the engine brake control switch valve; a low D2 range pressure line connected to the fourth clutch with a 3-way valve interposed therebetween; and a low L range pressure line connected to the low control valve.
According to another feature of the present invention, the first, second and third solenoid valves are 3-way valves which maintain a closed state when controlled to OFF.
According to yet another feature of the present invention, a valve body of the first pressure control valve includes a first port for receiving hydraulic pressure reduced by a reducing valve; a second port for receiving hydraulic pressure from the manual valve; a third port for supplying the hydraulic pressure received by the second port to the first clutch; and a fourth port for receiving control pressure from the first solenoid valve; a valve spool of the first pressure control valve slidably provided in the valve body of the first pressure control valve includes a first land on which the hydraulic pressure supplied through the first port acts, the first land having a relatively small diameter; a second land on which the hydraulic pressure supplied through the first port acts to selectively open and close the second port; and a third land which, together with the second land, selectively communicates the second port and the third port; and an elastic member is disposed between the third land and the valve body.
According to still yet another feature of the present invention, a valve body of the second pressure control valve includes a first port for receiving hydraulic pressure reduced by a reducing valve; a second port for receiving hydraulic pressure from t
Hu Ha
Hyundai Motor Company
Marmor Charles A
LandOfFree
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