Endless belt power transmission systems or components – Pulley with belt-receiving groove formed by drive faces on... – Load responsive
Reexamination Certificate
2000-04-25
2002-05-14
Hannon, Thomas R. (Department: 3682)
Endless belt power transmission systems or components
Pulley with belt-receiving groove formed by drive faces on...
Load responsive
C474S028000
Reexamination Certificate
active
06387000
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a pressure medium supply arrangement for a continuous variable transmission (CVT transmission) comprising a pump by which the control cylinder can be supplied with pressure medium (hydraulic medium) for changing the gear ratio, wherein the pump has correlated therewith a control valve arrangement via which a bypass channel between the high-pressure side and the low-pressure side of the pump can be opened or closed for controlling the conveyed flow.
2. Description of the Related Art
Such CVT transmissions have been known for several years and allow a continuous change of the gear ratio of a motor vehicle. Since the CVT transmissions have not been able to compete with conventional automatic transmissions, efforts are currently undertaken in the process of developing high torque diesel engines (common rail fuel injection system, monobloc injection pump and nozzle injection systems) to use the advantages of the CVT transmission, i.e., the possibility of a continuous change of the gear ratio as a function of the operational parameters of the motor. Such transmissions allow, for example, to maintain the engine within predetermined torque or output ranges as a function of the driving conditions (acceleration, steady driving, breaking etc.) so that an optimal output with optimal fuel consumption is ensured.
FIG. 1
shows a basic concept of a CVT transmission as, for example, disclosed in the European patent document 0 271 109 or European patent document 0 076 552.
The central part of the CVT transmission
1
illustrated schematically in
FIG. 1
is a belt or piston drive
2
by which the crankshaft of an internal combustion engine
4
is connected with the reducing gear transmission
6
of a motor vehicle. The ratio of speeds of the belt drive can be adjusted continuously, for example, in the range of 3:1 up to 0.3:1 so that the motor
4
as a function of the desired driving state can always be maintained within the optimum torque/output range.
The belt drive has a belt
10
which is guided on two V pulleys
12
,
14
. The upper V pulley
12
of
FIG. 1
is coupled to the motor
4
while the lower V pulley
14
is connected to the reducing gear transmission
6
. The belt
10
is comprised conventionally of circulating steel belts which have a plurality of plate-shaped elements
16
by which the belt
10
rests on the V pulleys
12
or
14
.
Each of the V pulleys
12
,
14
has a stationary disc
18
or
19
and a movable disc
20
or
21
which can be moved in the axial direction relative to the correlated stationary disc
18
or
19
in order to change the support width for the belt
10
or, in other words, for the elements
16
. The movement of the movable discs
20
,
21
is performed by control cylinders
22
,
24
wherein, for example, the control cylinder
22
correlated with the V pulley on the motor side has a greater end face surface then the cylinder
24
on the reducing gear transmission side. The control cylinders
22
,
24
are connected by a control device
26
and a control valve arrangement
28
to a pump
30
and a hydraulic medium tank T.
As can be taken from the schematic of
FIG. 1
, the two movable discs
20
,
21
, respectively, the stationary discs
18
,
19
are arranged in a crossed arrangement so that the belt
10
is guided always straight, i.e., in a perpendicular line to the axes of the V pulleys
12
,
14
.
The control device
26
comprises, for example, a two-edge or four-edge control slide (piston) by which the hydraulic medium supplied by the pump
30
can be distributed to the two control cylinders
22
,
24
in order to perform the desired adjusting movements. When, for example, the same pressure is present, the support width of the V pulley
12
at the motor side is reduced by the greater force of the control cylinder
22
and, accordingly, the support width of the V pulley
14
at the reducing gear transmission side is enlarged against the force transmitted by the control cylinder
24
so that the belt
10
in the representation according to
FIG. 1
moves upwardly. This is so because of the different size of the end faces of the control cylinders
22
and
24
.
Via the control valve arrangement
28
the conveyed flow of the pump
30
is adjusted so that at all times only the required amount of hydraulic medium flows to the control cylinders
22
,
24
or is returned from them into the tank T.
The pumps
30
are often in the form of rotary piston pumps, for example, internal gear pumps, because they have a comparatively simple construction and can produce relatively high pressures with minimal weight. A further advantage of internal gear pumps is that they can be used in comparatively broad rpm (revolutions per minute), temperature, and viscosity ranges and operate with minimal pulsation and noise.
In European patent document 0 445 529 B1 an internal gear pump is described in which two gear wheels are rotatably supported in the housing. The displacement chambers are delimited by meshing tooth flanks, an inner wall of the housing, and an axial plate or pressure plate. The latter is loaded on its backside by a hydraulic medium so that it contacts sealingly the end faces of the gear wheels. The pressure acting on the backside of the pressure plate can be adjusted by a control device in which a metering orifice embodied as a directional control valve and a three-port directional pressure regulator (pressure scale) cooperate. It is loaded in the sense of increasing the pressure at the backside by the pressure downstream of the metering orifice as well as a pressure spring and in the sense of a reduction of the pressure at the backside by the pressure upstream of the metering orifice. The pressure regulator (pressure scale) connects forth is purpose a control connector connected to a pressure chamber on the backside of the pressure plate with the pressure outlet of the pump or with the tank, so that the sealing gap between the pressure plate and the end faces of the gear wheels is reduced or enlarged. For an enlarged sealing gap the hydraulic medium can flow directly from the high pressure side to the low pressure side so that the volumetric efficiency of the gear wheel machine can be reduced and, for example, the conveying volume or capacity of the gear pump can be adjusted as a function of the gap width. This means that by influencing the hydraulic medium pressure acting on the pressure plate an exact conveyed flow regulation can be performed.
In U.S. Pat. No. 4,014,630 a pump arrangement is disclosed in which a sealing plate is forced by a spring into the contact position on the conveying elements. The spring chamber is connected by a throttle bore to the displacement chamber of the pump arrangement so that the pressure plate is also hydraulically prestressed into its sealing position. The pressure acting on the pressure plate can again be adjusted by a control device via which the hydraulic medium can be returned to a tank.
A disadvantage of this construction is that a considerable expenditure must be provided in order to be able to adjust the conveyed flow of the pump quickly to changes of the operating parameters of the motor.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a hydraulic medium supply for a CVT transmission which allows a fast adjustment of the conveyed flow to the changes of the operational and functional parameters of the motor of a vehicle.
In accordance with the present invention, this is achieved in that the control valve arrangement is electrically controlled.
According to the present invention, the control valve arrangement correlated with the pump is electrically controlled so that the conveyed flow change can be adjusted already beforehand, i.e., for example, upon initiation of the acceleration or braking process. This means that via suitable sensors changes of the corresponding control members (gas pedal, fuel pump, diesel pump, brake pedal etc.) are detected and, as a function of these changes, a signal is sent by t
Eisenbacher Egon
Unsöld Manfred
Charles Marcus
Hannon Thomas R.
Huckett Gudrun E.
Hydraulik-Ring GmbH
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