Planetary gear transmission systems or components – Fluid drive or control of planetary gearing – Fluid controlled mechanical clutch or brake
Reexamination Certificate
2000-05-24
2002-04-02
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, C475S127000
Reexamination Certificate
active
06364802
ABSTRACT:
BACKGROUND OF THE INVENTION
(a) Field of the Invention
The present invention relates to a hydraulic control system for a continuously variable transmission. More particularly, the present invention relates to a hydraulic control system for a continuously variable transmission in which only a single accumulator is used, thereby minimizing the number of elements in the hydraulic control system.
(b) Description of the Related Art
The transmission functions to deliver engine drive power to the drive wheels. There are three basic types of transmissions: (a) the manual transmission, in which the driver manipulates a shift lever to control shifting into different speeds and ranges; (b) the automatic transmission, in which shifting into the different forward speeds is automatically controlled according to various driving conditions; and (c) the continuously variable transmission, in which shifting is automatically performed over a single, large range and on a continuous basis when in either forward or reverse mode.
Among the different types of transmissions described above, the continuously variable transmission is ideal for many situations as it offers the convenience and ease of control of the automatic transmission, while providing many additional advantages such as reduced fuel consumption, enhanced power transmission performance, and reduced weight. In the continuously variable transmission, one pulley is mounted on an input shaft and another pulley is mounted on an output shaft, and a diameter of the pulleys is varied to realize shifting. Such a continuously variable transmission is referred to as a belt-type continuously variable transmission.
A hydraulic control system for controlling the belt-type continuously variable transmission will now be described with reference to FIG.
2
.
Hydraulic flow is generated by an oil pump
102
to create hydraulic pressure in the hydraulic control system. This hydraulic pressure passes through a primary regulator valve
104
such that the hydraulic pressure undergoes initial control to a predetermined level of line pressure. The line pressure is then supplied to a secondary regulator valve
106
and a secondary pulley
108
. The line pressure undergoes secondary control to a predetermined level in the secondary regulator valve
106
, after which the line pressure is fed to a solenoid supply valve
110
. The solenoid supply valve
110
distributes the hydraulic pressure to first, second, third and fourth solenoid valves S
1
, S
2
, S
3
and S
4
. The line pressure supplied from the secondary regulator valve
106
is also supplied to a shift ratio control valve
111
, a pressure regulator valve
114
, and a torque converter feed valve
122
.
The hydraulic pressure supplied to the shift ratio control valve
111
by the secondary regulator valve
106
is fed to a primary pulley
112
according to control by the second solenoid valve S
2
, thereby effecting changes in a diameter of the primary pulley
112
. Such variations in the diameter of the primary pulley
112
result in gearless shifting.
Further, the hydraulic pressure supplied to the pressure regulator valve
114
by the secondary regulator valve
106
is then supplied to a manual valve
116
according to control by the third solenoid valve S
3
. The hydraulic pressure is subsequently supplied to a forward pressure line
118
or a reverse pressure line
120
depending on how the driver positions a select lever. If the hydraulic pressure is supplied to the forward pressure line
118
, a first friction element C receives the hydraulic pressure, and if the hydraulic pressure is fed to the reverse pressure line
120
, a second friction element B receives the hydraulic pressure.
The hydraulic pressure supplied to the torque converter feed valve
122
by the secondary regulator valve
106
is stabilized in the torque converter feed valve
122
, then supplied to a lock-up clutch control valve
124
. The lock-up clutch control valve
124
subsequently supplies the hydraulic pressure to the torque converter and elements requiring lubrication according to control by the fourth solenoid valve S
4
.
An accumulator
126
is provided on each of the forward pressure line
118
and the reverse pressure line
120
. The accumulators
126
and
128
stabilize the operation of the first and second friction elements C and B respectively. In addition, a bypass line
132
is formed on the forward pressure line
118
and a bypass line
134
is formed on the reverse pressure line
120
. Check valves
136
and
138
are provided on the bypass lines
132
and
134
respectively, the check valves
136
and
138
opening during the exhaust of hydraulic pressure to enable the quick exhaust of the hydraulic pressure. A safety valve
140
is provided on the reverse pressure line
120
. The bypass line
134
, the reverse pressure line
120
, and the forward pressure line
118
are connected to the safety valve
140
.
In the hydraulic control system with the above configuration, gearless shifting is realized in the forward range by variations in the diameter of the primary and secondary pulleys
112
and
108
in a state where hydraulic pressure is being supplied to the first friction element C, while gearless shifting is realized in the reverse range by variations in the diameter of the primary and secondary pulleys
112
and
108
in a state where hydraulic pressure is being supplied to the second friction element B.
However, in such a hydraulic control system, because an accumulator is applied at each of the friction elements C and B, the use of two accumulators utilizes a substantial amount of space, increases the weight of the system, and also acts to increase manufacturing costs.
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 for a continuously variable transmission in which a single accumulator is used to control two friction elements such that the weight and size of the hydraulic control system is reduced, and production costs are minimized.
To achieve the above object, the present invention provides a hydraulic control system for a continuously variable transmission comprising a pressure regulating means including a primary regulator valve for regulating hydraulic pressure supplied from an oil pump, a first solenoid valve, a secondary regulator valve, and a solenoid supply valve; a shift control means including a shift ratio control valve, and a second solenoid valve controlling the shift ratio control valve; a forward/reverse control means including a pressure control valve, a third solenoid valve controlling the pressure control valve, a manual valve, and first and second friction elements acting respectively as forward and reverse operational elements; and a torque converter operation control means including a torque converter feed valve receiving hydraulic pressure from the pressure regulating means, a lock-up clutch control valve, and a fourth solenoid valve controlling the lock-up clutch control valve, wherein a single accumulator is mounted between the pressure control valve and the manual valve of the forward/reverse control means.
According to a feature of the present invention, a bypass line is formed between the pressure control valve and the accumulator, and a check valve is provided on the bypass line, the check valve being able to block the flow of hydraulic pressure through the bypass line.
REFERENCES:
patent: 4747327 (1988-05-01), Itoh et al.
patent: 4827805 (1989-05-01), Moan
patent: 5086671 (1992-02-01), Oshidari
patent: 5089964 (1992-02-01), Morishige et al.
patent: 5269726 (1993-12-01), Swanson et al.
patent: 5409421 (1995-04-01), Sakai et al.
patent: 6019700 (2000-02-01), Imai et al.
patent: 4029676 (1992-01-01), None
patent: 5099302 (1993-04-01), None
Ho Ha
Hyundai Motor Company
Marmor Charles A.
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