Interrelated power delivery controls – including engine control – Transmission control – Continuously variable friction transmission
Reexamination Certificate
2001-03-14
2003-04-15
Schwartz, Christopher P. (Department: 3683)
Interrelated power delivery controls, including engine control
Transmission control
Continuously variable friction transmission
C477S046000
Reexamination Certificate
active
06547694
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates in general to a continuously variable transmission of the type employing a V-belt for use in a vehicle or the like, and more particularly to improvements in a hydraulic control system for the same.
2. Description of the Prior Art
A V-belt type continuously variable transmission (CVT) suitable for vehicle applications is disclosed in, for example, Japanese Patent Application Laid Open No. 11-82725.
In such a V-belt type continuously variable transmission, a V-belt passes about a primary pulley which is coupled to an engine and a secondary pulley which is coupled to the wheel axle of the vehicle. The groove width of the primary pulley is variably controlled by the supply of hydraulic pressure. The general construction of the transmission together with a conventional hydraulic control system therefor is shown in
FIGS. 2 and 3
.
The transmission mechanism
10
comprises a primary pulley
16
, a secondary pulley
26
and a V-belt
24
provided between the primary and secondary pulleys
16
and
26
, and is coupled to an engine (not shown) via a torque converter
12
with a lockup clutch
11
incorporated therein.
More particularly, the primary pulley
16
comprises a pair of fixed and moving conical boards
18
and
22
, which are facing each other to define V-shaped pulley groove therebetween. The fixed conical board
18
is fixedly connected to an output shaft of the torque converter
12
for rotation therewith. The primary pulley
16
is provided with first cylinder chamber
20
, and the moving conical board
22
can be axially displaced by supplying hydraulic pressure to the first cylinder chamber
20
.
The secondary pulley
26
also comprises a pair of fixed and moving conical boards
30
and
34
, which are facing each other to define V-shaped pulley groove therebetween. The fixed conical board
30
is fixedly connected to an output shaft associated with an axle(not shown) for rotation therewith. The secondary pulley
26
is provided with second cylinder chamber
32
, and the moving conical board
34
can be axially displaced by supplying hydraulic pressure to the second cylinder chamber
32
. The moving conical board
34
is also normally biased in a direction reducing the width of the corresponding pulley groove by a return spring (not shown).
The operation of the transmission mechanism
10
can be controlled by the hydraulic control valve system
3
in dependence on control signals from the CVT control unit
1
.
The second cylinder chamber
32
of the secondary pulley
26
is continuously supplied with a predetermined line pressure from the hydraulic control valve system
3
and the first cylinder chamber
20
of the primary pulley
16
can be placed in fluid communication with a shift control valve
63
of the valve system
3
. It should be noted that a pressure receiving net area of the first cylinder chamber
20
is set to be greater than that of the second cylinder chamber
32
.
While the line pressure is supplied to the second cylinder chamber
32
, the shift control valve
63
maybe operated to control the hydraulic pressure supplied to the first cylinder chamber
20
so as to continuously change the width of the groove of the primary pulley
16
to thereby control a force for clamping the V belt
24
between the opposite conical boards. In this way, driving torque can be transmitted between the output shaft of the torque converter and the output shaft associated with the axle depending on the frictional force between the V-belt
24
and the pulleys
16
and
26
.
The transmission mechanism
10
may vary the effective contact radius of the V-belt
24
at the contact position of each of the first and second pulleys
16
and
26
by changing the width of the pulley grooves of the respective pulleys, resulting in variation in the speed ratio between the primary and secondary pulleys
16
and
26
. More specifically, the transmission mechanism
10
can establish a high transmission ratio (i.e., a pulley ratio LOW) by widening the primary pulley groove to decrease the effective contact radius of the V-belt
24
on the primary pulley
16
and to increase the effective contact radius of the V-belt
24
at the secondary pulley
26
. Thus, the rotation of the engine side is transmitted to reduced rotation of the axle side.
The transmission mechanism
10
can also establish a low transmission ratio (i.e., a pulley ratio HI) by narrowing the primary pulley groove to increase the effective contact radius of the V-belt
24
on the primary pulley
16
. In this case, the rotation of the engine side is transmitted to increased rotation of the axle side.
As can be seen, the transmission ratio can be continuously changed as a function of the ratio of the contact radii of the V-belt
24
on the primary pulley
16
and on the secondary pulley
26
.
The hydraulic control valve system
3
also includes a line pressure regulator
60
which is adapted to receive and regulate hydraulic pressure from a hydraulic pump
80
, and continuously supplies the regulated line pressure to both the second cylinder chamber
32
and an input port of the shift control valve
63
. To control the hydraulic pressure supplied to the first cylinder chamber
20
, the shift control valve
63
actuated by a step motor
64
regulates the line pressure as the original pressure. As well known in the art, the valve system
3
further comprises a line pressure solenoid valve
4
, a pressure modifier valve
62
and a pilot valve
61
also in fluid communication with the valve
4
.
The CVT control unit
1
is adapted to separately receive a signal representative of a selected position of an inhibitor switch
8
, a signal representative of throttle opening degree TVO (a degree of depression of the accelerator pedal operated by the operator) generated by a throttle opening sensor
5
and a signal representative of an engine rpm Ne from an engine speed sensor (not shown) and estimate an engine torque on the basis of these signals. Then, the CVT control unit
1
determines the required line pressure on the basis of the estimated engine torque and provides a duty ratio signal to the line pressure solenoid
4
and also issue a command to the step motor
64
to initiate shift control for the target transmission ratio. When the step motor
64
is a total of 200 step positions, for example, 20 to 170 positions thereof may advantageously be utilized for establishment of the target transmission ratio.
The line pressure solenoid
4
is operable to supply the hydraulic pressure from the pilot valve
61
to the pressure modifier valve
62
in response to the input duty ratio signal from the CVT control unit
1
and the line pressure regulator
60
is operable to regulate the hydraulic pressure from the hydraulic pump
80
in dependence on the hydraulic pressure demand signal generated by the pressure modifier valve
62
. In this way, the line pressure can be varied within the predetermined range depending on the required torque to be transmitted.
The shift control valve
63
has a spool
63
a
which at its one end is pivotally connected to a shift link
67
which in turn at one end is connected to the moving conical board
22
of the primary pulley
16
via a movable member
71
and at the other end to the step motor
64
. The spool
63
a
slides according to the displacement of the shift link
67
.
The shift control valve
63
receives the line pressure from the line pressure regulator
60
, and supply the controlled pressure, which is reduced from the line pressure by the displacement of its spool
63
a
, to the first cylinder chamber
20
to thereby change the width of the primary pulley groove. In this way, the desired transmission ratio is attained.
The CVT control unit
1
has connected thereto a first speed sensor
6
which detects the rotational speed (Npri) of the primary pulley
16
and also a second speed sensor
7
which detects the rotational speed (Nsec) of the secondary pulley
26
. The CVT control unit receives the Npri and Nsec signa
Miyagawa Yoshikazu
Sakakibara Satoshi
Jatco Transtechnology Ltd.
Rossi & Associates
Schwartz Christopher P.
Torres Melanie
LandOfFree
Hydraulic control system for a continuously variable... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Hydraulic control system for a continuously variable..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Hydraulic control system for a continuously variable... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3008519