Note: Descriptions are shown in the official language in which they were submitted.
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A HYDRAULIC CONTROL SYSTEM FOR AUTOMATIC
TRANSMISSION
BACKGROUND OF THE l~v~NllON
Field of the Invention
The present invention relates to a hydraulic
control system for automatic transmission, and more
particularly to the control system which can ensure a
control of a damper clutch and minimize a loss of a
drive of an oil pump.
Description of Related Art
Generally, an oil pump driven by a driving force
generates a hydraulic pressure for engaging a friction
element which changes a speed ratio by selecting a gear
stage of gear stages of a multi-stage transmission gear
mech~nism.
A hydraulic control system pressurized by an oil
pump changes ports of shift valves in accordance with an
operation of a solenoid valve or proportional control
valves which are controlled to be turned ON/OFF or duty
by a transmission control unit.
At this point, the line pressure is supplied to the
selected friction member through the changed port to
engage or release the friction member.
The oil pump generates the hydraulic pressure in
proportion to the number of rotation of the engine. To
establish a stable speed ratio change, the hydraulic
control system should receive a regular hydraulic
pressure. Thus, the hydraulic pressure generated from
the oil pump is always controlled in a regular line
pressure by a regulator valve.
The regulator valve is designed to control the
hydraulic pressure in two modes, driving mode and
reverse mode.
However, since the hydraulic pressure become fixed
hydraulic pressure at the drive and reverse modes,
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respectively, when the shift lever is changed from the
neutral "N" range to the drive "D" range, a shift impact
occurs.
Accordingly, to decrease the shift impact caused by
shifting the shift lever from the neutral "N" range to
the drive "D" range, an N-D control valve is employed.
However, the hydraulic control system employing the N-D
control valve has a problem that the drive efficiency is
deteriorated since the hydraulic control system always
uses the fixed hydraulic pressure.
Additionally, since a reducing valve which reduces
the hydraulic pressure to be lower than the line
pressure to operate a pressure control valve and a
damper clutch control valve is controlled by an elastic
force of an elastic member and the line pressure, the
operation of the reducing valve is unreliable.
Further, a damper clutch employed for increasing a
mech~ical efficiency of power transmission in a torque
converter is engaged or released by a damper clutch
control valve. Since a position of a valve spool of the
damper clutch control valve is determined in accordance
with the elastic force of the elastic member and a
disparity in an area of lands of the valve spool, there
is a problem that the valve spool is stuck.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide
a hydraulic control system for an automatic
transmission, which can minimize a loss of drive of an
oil pump.
It is another object of the present invention to
provide a hydraulic control system for an automatic
transmission, which can ensure a control of a damper
clutch and minimize a shift impact thereby increasing
stability of a hydraulic pressure.
To achieve the objects, the present invention
provides a hydraulic control system for an automatic
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transmission, the system comprising:
an oil pump for generating the hydraulic pressure;
a plurality of shift valves for controlling a
plurality of clutch and brake means with the hydraulic
pressure in accordance with a vehicle's drive and
reverse speed and transmitting a torque of a torque
converter to a gear of a multi-stage transmission gear
mechanism;
a manual valve for selectively supplying the
hydraulic pressure generated from the oil pump to each
shift valve by changing ports thereof in accordance with
a position of a shift lever;
a reducing valve for regulating the hydraulic
pressure generated from the oil pump to be lower than a
line pressure;
a pressure regulating valve for receiving a control
pressure by communicating with the manual valve, and
changing the line pressure by opening or closing an
exhaust port thereof, the opening or closing of the
exhaust port is accomplished when the valve spool of the
pressure regulating valve is moved by the hydraulic
pressure which is reduced at the reducing valve;
a rear clutch exhaust valve for directly supplying
the hydraulic pressure supplied from the manual valve to
a rear clutch in a first forward speed ratio of a drive
"D" range;
two shift control solenoid valves, which are
controlled to be turned "OFF" or "ON" by a transmission
control unit, for supplying the hydraulic pressure
supplied from the manual valve to a second, third and
fourth speed lines in second, third, and fourth forward
speed ratios, respectively;
a shift control valve for selectively opening the
second, third, and fourth speed lines by moving a valve
spool thereof which is moved in accordance with the
ON/OFF operation of the shift control solenoid valves;
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and
a damper clutch control valve for supplying the
hydraulic pressure to a damper clutch engaging line or
releasing line by moving a valve spool thereof which is
moved in accordance with exhausting or cutting off the
hydraulic pressure of the reducing valve.
Further scope of applicability of the present
invention will become apparent from the detailed
description given hereinafter. However, it should be
understood that the detailed description and specific
examples, while indication preferred embodiments of the
invention, are given by way of illustration only, since
various changes and modifications within the spirit and
scope of the invention will become apparent to those
skilled in the art from this detailed description.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will become more fully
understood from the detailed description given
hereinbelow and the accompanying drawings which are
given by way of illustration only, and thus are not
limitative of the present invention, and wherein:
FIG. 1 is a schematic diagram of a hydraulic
control system according to the present invention;
FIG. 2 is a detailed view of a part Pl in FIG.l;
and
FIG. 3 is a detailed view of a part P2 in FIG.l.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to FIG. 1, a hydraulic control system
comprises an oil pump 2 for generating a hydraulic
pressure by way of a driving force of an engine(not
shown), a pressure regulating valve 4 for regulating a
line pressure supplied from the oil pump 2, and a torque
converter 6 for transmitting the driving force of the
engine to an input shaft of the transmission.
The torque converter 6 directly or indirectly
transmits the driving force of the engine to the input
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shaft of the transmission by way of the damper clutch
control valve 8 which controls the hydraulic pressure
working on a damper clutch DC.
The damper clutch control valve 8 i6 designed to
receive the hydraulic pressure which i8 controlled by
a torque converter control valve 10 which regulates the
hydraulic pressure of the torque converter 6 and the
hydraulic pressure used for lubricating when the damper
clutch is disengaged.
The hydraulic pressure generated from the oil pump
2 is further supplied to the reducing valve 12 and
controlled to be lower than the line pressure, and the
controlled hydraulic pressure controls each valve spool
of a pressure control valve 14, the hydraulic pressure
regulator valve 4, and the damper clutch valve 8.
The hydraulic pressure generated from the oil pump
2 is further supplied to a manual valve 16. Ports of
the manual valve are change by a shift lever(not shown).
Thus the hydraulic pressure is supplied in accordance
with a position of a valve spool of the manual valve 16
to a shift control valve 18, the pressure control valve
14, and an N-R control valve which reduces the shift
impact when the shift lever is shifted from the neutral
"N" range to the reverse "R" range.
The hydraulic pressure is supplied to the rear
clutch exhaust valve 26 through a first-speed line 24
which is branched off from the line 22 which connects
the manual valve 16 to the shift control valve 18. A
rear clutch 28 receives the hydraulic pressure in
accordance with a change of ports of the rear clutch
exhaust valve 26 and is engaged thereby.
A valve spool of the shift control valve 18 changes
in its position by two shift control solenoid valves
A,B. The shift control solenoid valves A,B are
controlled to be turned "ON/OFF" by a transmission
control unit TCU, such that the hydraulic pressure
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supplied from the line 22 is supplied in accordance with
the position of the valve spool of the shift control
valve 18 to a lst-2nd speed shift valve 30, an end
clutch valve 32, and a 2nd-3rd/4th-3rd speed shift valve
34 through second, third and fourth speed lines 36, 38
and 40, respectively.
The shift valves are designed to selectively supply
the hydraulic pressure to a front clutch 42, a
low/reverse brake 44, an end clutch 46, and a kick-down
servo 48 thereby engaging them selectively.
Each port of the N-R control valve 20 and the
pressure control valve 14 is changed by a solenoid valve
C controlled by the transmission control unit TCU.
Each port of the pressure regulator valve 4 and the
damper clutch control valve 8 is changed by each
solenoid valves D,E.
FIG. 2 is a detailed view of a part Pl in FIG. 1,
wherein the pressure regulating valve 4 includes a
first port 50 into which the hydraulic pressure flows,
a second port 52 for supplying the hydraulic pressure to
the torque converter control valve 10, a third port 54,
a fourth port 56 communicating with the third port 54,
a fifth port 58 which is connected with the manual valve
16 to change the line pressure at the drive "D" range,
and a sixth port 60 through which the hydraulic pressure
is exhausted when it becomes high.
The pressure regulating valve 4 further includes a
seventh port 62 on which the hydraulic pressure is
formed or through which the hydraulic pressure is
exhausted by the solenoid valve D.
The pressure regulating valve 4 further includes a
valve spool 64 which selectively opens and closes the
sixth ports. The valve spool includes a first land 66,
a second land 68, a third land 70, and a fourth land 72.
The first land 66 is elastically supported by an elastic
member 74 and is designed to always receive a force
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rightward in the drawing.
The torque converter control valve includes a first
port 76 connected to the second port 52 of the pressure
regulator valve 4 to receive the hydraulic pressure, a
5second port 78 through which the hydraulic pressure is
exhausted, and a third port 80 through which the
hydraulic pressure is supplied to the damper clutch
control valve 8.
The torque converter control valve 10 further
10includes a valve spool 82 having a first land 84 for
opening and closing the second port 78 and a second land
86 where the by-pass passage is formed for the hydraulic
pressure to work on a right side surface of the second
land thereby moving the valve spool 82. The first land
1584 is elastically supported by an elastic member 88
thereby receiving a force rightward in the drawing.
The damper clutch control valve 8 includes a first
port 90 for receiving the hydraulic pressure from the
third port 80 of the torque converter control valve 10,
20a second port 92 for supplying the hydraulic pressure
supplied through the first port 90 to the damper clutch
release line L2 of the torque converter, a third port 94
for supplying the hydraulic pressure flowing through the
first port 90 to the damper clutch engaging line Ll of
25the torque converter, fourth and fifth ports 100,102
through which the hydraulic pressure supplied through
the first port 90 is supplied to a right side of a first
land 98 of a valve spool 96, and a sixth port 104 for
moving the valve spool 96 leftward in accordance with an
30operation of the solenoid valve E.
The valve spool 96 further includes a second land
106 and a third land 108 which move between the first
port 90 and the fourth port 100 to open and close them.
The reducing valve 12 includes a fist port 110
35through which the hydraulic pressure is supplied, a
second port 112 through which the hydraulic pressure
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supplied through the first port 110 is reduced and flows
out, and a third port 114 communicating with the second
port to receive the hydraulic pressure working on the
right side of a first land 118 of a valve spool 116.
The valve spool 116 further includes a second land
120 for controlling an opening area of the second port
112, and a third land 122 for controlling an opening
area of the first port 110. The third land 122 is
elastically supported by an elastic member 124.
The elastic member 124 is contacted at its one end
with an operation plate 126. The operation plate is
designed to be moved leftward or rightward by a screw
128 penetrating a valve body to vary an elastic force of
the elastic member 124.
The second port 112 of the reducing valve 12 is
connected to the seventh port 62 of the pressure
regulating valve 4 and the sixth port 104 of the damper
clutch control valve 8, such that a reduced hydraulic
pressure is supplied thereto.
FIG. 3 is a detailed view of a part P2 in FIG. 1,
in which the manual valve 16 includes a first port 130
for receiving the hydraulic pressure generated from the
oil pump, a second port 132 for supplying the hydraulic
pressure to the fifth port 58 of the pressure regulating
valve 4, and a third port 134 for supplying the
hydraulic pressure to the shift control valve 18 and the
rear clutch exhaust valve 26.
The manual valve 16 further includes a fourth port
136 for supplying the hydraulic pressure to the 2nd-
3rd/4th-3rd speed shift valve 34 through the rear clutch
exhaust valve 26, and the front clutch 42 so as to
engage them pressure, and to the kick-down servo 48 so
as to release it.
The manual valve further includes a valve spool 138
which co-operates with the shift lever(not shown). The
valve spool has first, second, and third lands 140, 142
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and 144. When the shift lever is shifted to the neutral
"N" range, the second land 142 is moved to between the
second port 132 and the third port 134, whereby the
hydraulic pressure can not be supplied to the shift
control valve 18.
The shift control valve 18 includes a first port
146 which communicates with the line 22 to receive the
hydraulic pressure, a second port 148 which communicates
with the second speed line 35, a third port 150 which
communicates with the third speed line 38, and first,
second and third control ports 154, 156 and 158 which
regulate the hydraulic pressure in accordance with the
solenoid valves A, B.
The shift cont~ol valve 18 further includes a valve
spool 160 having a relatively large land 162 and a
relatively small land 164, a first plug 166 which is
disposed at a left side of the valve spool 160 and is
operated by the hydraulic pressure supplied through the
first control port 154, and a second plug 168 which is
disposed at a right side and is operated by the
hydraulic pressure supplied through the second control
port 156.
The rear clutch exhaust valve 26 is designed to
exhaust the hydraulic pressure which engages the rear
clutch at the fourth speed in drive "D" range, in which
the valve 26 includes a first valve spool 170 and a
second valve spool 172.
The first valve spool 170 includes a relatively
large first land 174, a second land 176, and a third
land 178 having a s~all diameter at its middle portion.
The second valve spool 172 includes first and
second lands having the same area as each other, and is
elastically supported at its right side by an elastic
member 184. In the fourth speed of drive "D" range, the
hydraulic pressure supplied through the fourth speed
line 40 of the shift valve 18 works on the right side
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surface of the first land 174 of the first valve spool
170, such that the first and second valve spools 170,
172 are moved rightward. Therefore, the small diameter
portion of the third land 178 of the first valve spool
5170 is located at a by-pass line 186, such that the
hydraulic pressure of the rear clutch is exhausted.
The hydraulic control system of the present
invention as described above generates the hydraulic
pressure by use of the oil pump 2 when the engine
starts.
The hydraulic pressure generated at this point
flows into the first port 50 of the pressure regulating
valve 4, the first port 110 of the reducing valve 12,
and the first port 130 of the manual valve 16.
15FIG. 1 is a view showing the hydraulic control
system in neutral "N" range mode. When the shift lever
is shifted from this mode to the drive "D" range mode,
the valve spool 138 of the manual valve 16 is moved
rightward and the second land 142 is located at a right
20side of the third port 134, such that the third port 134
communicates with the first port 130.
As the result, the hydraulic pressure flows into
the first port 146 of the shift control valve 18. At
this point, in the first forward speed ratio, since both
25of the shift control solenoid valves A,B are controlled
to be turned "ON' by the transmission control unit TCU,
the hydraulic pressure supplied to the first, second,
and third control ports 154, 156 and 158 is exhausted.
Accordingly, the valve spool 160 is moved leftward
30by the hydraulic pressure working on a right side
surface of the first land 162 which is larger than the
second land 164, whereby the first plug 166 is moved
leftward to cut off the second port 148.
However, the hydraulic pressure branched off from
35the line 22 is supplied to the rear clutch exhaust valve
26, and thereby to the rear clutch 28 through between
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the first and second lands 180, 182 of the second valve
spool 172 so as to engage the rear clutch 182, thereby
realizing the first forward speed ratio.
When the rear clutch 28 is engaged, the
transmission receives a driving force of the engine. At
this point, if a slip of the rear clutch is sensed by
the transmission control unit TCU, the transmission
control unit TCU controls the solenoid valve D to be
turned "OFF" to increase the hydraulic pressure which
flows into the seventh port 62 of the pressure
regulating valve 4.
Accordingly, since the valve spool 64 is designed
to be moved rightward, the second land is located
between the first port 50 and sixth port 60 for
exhausting, the hydraulic pressure is cut off, such that
all the hydraulic pressure generated from the oil pump
works as the line pressure.
On the contrary, if the slip of the rear clutch
does not occur, the transmission control unit TCU
controls the solenoid valve D to be turned "ON" to
exhaust the hydraulic pressure which flows into the
seventh port 62 of the pressure regulating valve 4.
Accordingly, since the valve spool 64 is designed
to be moved rightward by the hydraulic pressure working
on a right side surface of the third land 70, the sixth
port 60 for exhausting is to communicate with the first
port 50, such that a portion of the hydraulic pressure
is exhausted.
Since this operation as described above is
repeatedly accomplished by the transmission control unit
TCU which senses the slip of the rear clutch and the
line pressure is regulated thereby, the drive efficiency
of the oil pump is increased and when the shift lever is
shifted from the drive "D" range to the neutral "N"
range, a shift impact does not occur whereby an N-D
control valve which has been used for reducing the shift
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12
impact in the conventional art is not needed.
Further, if a vehicle speed is gradually increased
in a state of the first forward speed ratio, the
transmission control unit TCU controls the shift control
solenoid valve A to be turned "OFF" to form the
hydraulic pressure at the first control port 154. By the
operation, the first plug 166 is moved rightward while
pushing the valve spool 160.
As the result, the second land 164 of the valve
spool 160 is located between the second port 148 and the
third port 150 such that the hydraulic pressure-flowing
into the first port 146 is supplied to the second speed
line 36.
The hydraulic pressure supplied to the second speed
line 36 is supplied to a left side of the lst-2nd shift
valve 30 and pushes the valve spool Sl rightward, and at
the same time, a portion of the hydraulic pressure of
the first speed line 24 is supplied to the pressure
control valve 14.
At this point, the transmission control unit TCU
controls the solenoid valve C with a duty control to be
turned "OFF", thereby increasing the hydraulic pressure.
By the operation, the valve spool S2 of the pressure
control valve 14 moves rightward, such that the
hydraulic pressure supplied from the first speed line 24
is U-turned and flows into the lst-2nd shift valve 30.
At this point, since the valve spool Sl of the
shift valve 30 is in a state of being pushed rightward,
the hydraulic pressure is supplied to the kick-down
servo 48 to engage it, thereby accomplishing the second
forward speed ratio.
Further, if the vehicle speed gradually increases
in a state of the second forward speed ratio, the
transmission control unit TCU controls the shift control
solenoid valve B to be turned "OFF" as well as the shift
control solenoid valve A to increase the hydraulic
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pressure of the first and second control port 154, 156.
Accordingly, the valve spool 160 of the shift
control valve 18 in the state of second forward speed
ratio is moved by the hydraulic pressure working on a
left side surface of the first land 162.
By the operation, the second land 164 of the valve
spool 160 is located between the third port 150 and the
fourth port 152, such that the hydraulic pressure
supplied to the first port 146 is supplied to the second
and third speed lines.
Accordingly, a portion of the hydraulic pressure of
the third speed line 38 flows into a left side of the
shift valve 34 thereby moving the valve spool S3
rightward to contact the second plug 168.
By the operation, a portion of hydraulic pressure
supplied from the lst-2nd shift valve 30 to the kick-
down servo 48 is supplied to the 2nd-3rd/4th-3rd shift
valve 34 and thereby to the front clutch 42 as an
engaging pressure through the line Cl, and at the same
time, works on the kick-down servo 48 as a release
pressure.
Further, a portion of the hydraulic pressure of the
third speed line 38 is supplied to the end clutch valve
32 and thereby to the end clutch 46 through the line C2
to engage it. In consequence, all of the front clutch
42, rear clutch 28 and the end clutch 46 is engaged
thereby realizing the third forward speed ratio.
Further, if the vehicle speed gradually increases
in a state of the third forward speed ratio, the
transmission control unit TCU controls the shift control
solenoid valves B, A to be turned "OFF" and "ON",
respectively, such that the hydraulic pressure is not
formed at the first and second control ports 154, 156
but is formed at the third control port 158.
Accordingly, the valve spool 160 of the shift
control valve 18 is more moved rightward while pushing
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14
the second plug 168. By the operation, all the ports
148, 150, 152 is to open, such that the hydraulic
pressure is supplied to all the second, third, and
fourth speed lines 36, 38 and 40 simultaneously.
This is to realize the fourth forward speed ratio.
In the fourth forward speed ratio, the rear clutch 28
and the front clutch 42 are released and the kick-down
servo 48 is engaged.
When the hydraulic pressure of the fourth speed
line 40 is flowed into a left side of the rear clutch
exhaust valve 26, the hydraulic pressure works on a left
side surface of the first land 174 having the largest
land and pushes the first and second valve spools
170,172 rightward, and at the same time, is supplied to
a right side of the 2nd-3rd/4th-3rd shift valve 34
through the line C3 so that the valve spool S3 is again
moved leftward, whereby the engage and release of the
clutches 28,42 and kick-down servo 48 are realized.
Further, when the shift lever is shifted to the
reverse "R" range, the valve spool 138 of the manual
valve 16 is moved leftward, such that the second land
142 is located between the first port 130 and the second
port 132, and the first land 140 is located at a left
side of the fourth port 136.
A portion of hydraulic pressure supplied to the
first port 130 is supplied to the rear clutch exhaust
valve 26 through the fourth port 136 and thereby to the
right side of the 2nd-3rd/4th-3rd shift valve 34 through
the line C3, such that the valve spool is moved
leftward, and at the same time, the hydraulic pressure
is supplied to the line Cl through the line C4 to engage
the front clutch 42.
Further, a portion of hydraulic pressure flowing
into the first port 146 of the manual valve 16 is
supplied to the N-R control valve through the line C5.
At this point, since the transmission control unit TCU
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controls the solenoid valve C to be turned "OFF" with
the duty control, the valve spool S4 of the N-R control
valve 20 is moved leftward, such that the hydraulic
pressure of the line C5 is supplied to the lst-2nd speed
shift valve and thereby to the low/reverse brake 44
through the line C6.
During this operation, a portion of the hydraulic
pressure generated from the oil pump 2 flows into the
first port 110 of the reducing valve 12 and exhausted
through the second port 112. At this point, a portion of
the hydraulic pressure flows into the third port 114 and
works on a right side surface of the first land 118,
such that the position of the valve spool 116 is changed
in accordance with the line pressure. That is, if the
line pressure is high, the open;~g area of the second
port 112 reduces, and if the line pressure is low, the
opening area of the second port 112 is increased,
whereby the hydraulic pressure is stably supplied.
Further, if the damper clutch enters into a field
of engage, the transmission control unit TCU controls
the solenoid valve E to be turned "ON", such that the
hydraulic pressure supplied from the second port 112 of
the reducing valve 12 is not supplied to the sixth port
104 of the damper clutch control valve 8 but is
exhausted.
By the above operation, although the valve spool is
moved rightward, since the hydraulic pressure supplied
from the third port 80 of the torque converter 10 is
supplied to the fifth port 102 via the fourth port 100
and works on the right side of the first land 98 of the
valve spool 9~. As the result, the valve spool is moved
leftward.
Accordingly, the hydraulic pressure flowing into
the first port 90 is supplied to the line L2 to engage
the damper clutch DC.
Further, if the damper clutch does not enter into
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a field of engage, the transmission control unit
controls the solenoid valve E to be turned "OFF", such
that the hydraulic pressure of the sixth port 104 of the
damper clutch control valve 8 is to be high whereby the
valve spool 96 is to be moved leftward.
Accordingly, the hydraulic pressure flowing into
the first port 90 is supplied to the torque converter 6
via the line L1 to release the damper clutch DC.
This damper clutch control method prevents a valve
stick phenomenon which appears in a valve structure
using a spring, since the valve spool is regulated by
the reducing pressure to be moved leftward or rightward.
The present invention being thus described, it will
be obvious that the same may be varied in many ways.
Such variations are not to be regarded as a departure
from the spirit and scope of the invention, and all such
modifications as would be obvious to one skilled in the
art are intended to be included within the scope of the
following claims.
