U.S. patent application number 10/911166 was filed with the patent office on 2005-03-03 for system for controlling a hydraulic variable-displacement pump.
Invention is credited to Schmid, Johannes.
Application Number | 20050047930 10/911166 |
Document ID | / |
Family ID | 27762743 |
Filed Date | 2005-03-03 |
United States Patent
Application |
20050047930 |
Kind Code |
A1 |
Schmid, Johannes |
March 3, 2005 |
System for controlling a hydraulic variable-displacement pump
Abstract
In the case of a system for controlling a hydraulic variable
displacement pump, the latter is acted upon in the direction of
increasingly pump capacity over an energy storage system and, in
the opposite direction, over a hydraulic adjusting device, the
adjustment of the variable displacement pump being controlled over
a flow regulator, which is constructed especially as a restrictor
and the passable cross section of which is variable and which is
located in the connection between the adjusting device and the
reservoir, and which, for the sudden increase in the pump capacity
of the variable displacement pump, opens up a drainage cross
section to the reservoir, over which cross section an almost
loss-free drainage of the pressure medium, displaced by the
admission over the energy storage system, is possible.
Inventors: |
Schmid, Johannes;
(Schwaebisch Gmuend, DE) |
Correspondence
Address: |
JORDAN AND HAMBURG LLP
122 EAST 42ND STREET
SUITE 4000
NEW YORK
NY
10168
US
|
Family ID: |
27762743 |
Appl. No.: |
10/911166 |
Filed: |
August 4, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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10911166 |
Aug 4, 2004 |
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PCT/EP03/02138 |
Mar 3, 2003 |
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Current U.S.
Class: |
417/274 ;
417/213 |
Current CPC
Class: |
F04C 2/3441 20130101;
F16H 61/0025 20130101; F04C 14/223 20130101; F16H 61/0021 20130101;
F04C 14/26 20130101; F16H 61/66272 20130101 |
Class at
Publication: |
417/274 ;
417/213 |
International
Class: |
F04B 049/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 6, 2002 |
DE |
102 09 880.8 |
Claims
1. System for controlling a hydraulic variable-displacement in
which a variable displacement pump is acted upon in its control
direction, corresponding to the increase in the pump capacity, over
an energy storage system, and, in the opposite direction, over a
hydraulic control device, which is controlled at a return pipeline
that is branched off from the a high pressure intake, discharges
excess amounts pumped and runs out into a reservoir, and
furthermore, is controlled as a function of the return pipeline
pressure between a flow-control valve in the return pipeline and a
flow regulator downstream therefrom, a connection to the reservoir,
variable in the discharging cross section, being assigned to the
control device, the flow regulator forming the connection of
variable discharging cross section to the reservoir and that the
control device is located in the return pipeline between the
flow-control valve and the flow regulator, the discharging cross
section of the control device, controlled over the flow regulator,
being controlled in such a manner with respect to the reservoir
that, when the variable displacement pump is adjusted to the
maximum pump capacity, the size of the drainage cross section is
maximized for an unrestricted drainage.
2. The system of claim 1, wherein the flow regulator is controlled
as a function of control parameters specified by the consumer.
3. The system of claim 1, wherein the flow regulator is controlled
as a function of parameters determined by the consumer
environment.
4. The system of claim 1, wherein the flow regulator is an
adjustable restrictor.
5. The system of claim 1, wherein a measurement restrictor is
disposed downstream, in the direction of the control device, from
the flow-control valve controlling the passable cross section of
the hydraulic control device and that a control piston, which is
constructed as a pressure-maintaining valve, is acted upon by
pressure, on the one hand, through the connection to the pressure
side of the variable displacement pump and, in the opposite
direction to this, by a spring as well as over a branch, which is
connected downstream from the measurement restrictor.
6. The system of claim 1, wherein the control device is adjusted,
the volumes of the control device, which change in opposite
directions (pressure space, rear area) are connected with one
another and communicate with little loss.
7. The system of claim 1, wherein the system is a control agent of
a power-assisted steering system.
8. The system of claim 1, wherein the system is for a
transmission.
9. The system of claim 1, wherein the variable displacement pump is
as a rotary vane pump.
10. The system of claim 1, wherein the system is for a continuous
variable automatic transmission (CVT).
Description
[0001] The invention relates to a system for controlling a
hydraulic variable-displacement pump for a consumer in accordance
with the introductory portion of claim 1.
[0002] In practice, a operating system with hydraulic consumers,
such as power-assisted steering devices of motor vehicles, usually
employ constant-displacement pumps and excess amounts, obtained as
a function of the rpm by means of the driving mechanism of the pump
over the internal combustion engine of the vehicle, are
decompressed and returned to the suction side of the pump.
Appreciable losses and thermal loads are associated with this,
especially at a higher rpm. However, these are accepted in order to
have large flow rates, corresponding even to the maximum
requirement of the consumer, available at all times suddenly in
case of need and, with that, ensure that the respective hydraulic
consumer, such as the operating cylinder, which intensifies the
steering power of power-assisted steering devices is acted upon
without delay. Until now, the use of hydraulic
variable-displacement pumps, by means of which the pump capacity
could be adapted to the respective requirement and, with that, the
power dissipated reduced, has failed in practice owing to the fact
that the adjusting dynamics of the pumps for increasing the pump
capacity could not always satisfy requirements, which could lead to
critical conditions from a comfort and also a safety point of
view.
[0003] In the case of a system, working with a hydraulic
variable-displacement pump and disclosed in the DE 197 22 495 A1,
as acknowledged in the introductory portion of claim 1, the
variable-displacement pump, which is constructed as a rotary vane
pump, is acted upon, in the direction of an adjustment to a rate of
delivery by an energy storage system in the form of a spring and,
in the opposite direction, by a hydraulic regulating unit, the
latter being connected in a return line, which is branched off from
the high-pressure intake to the consumer, discharges excessive
amounts pumped and drains into a reservoir. In the return line,
there is a flow-control valve in the direction of flow to the
reservoir and a restrictor as flow regulator discharging into the
reservoir and, between the flow-control valve and the restrictor,
the control pressure for a control valve is branched off, over the
spool valve of which the cross section of the connection of the
hydraulic control device of the variable displacement pump to the
high-pressure connection between the pump and the consumer or to
the reservoir is controlled. Such a control is relatively complex
and the sudden adjustment of the variable displacement pump, aimed
for in the case of this solution in the sense of a sudden increase
in the pump capacity or in the system pressure, is dependent on
that, initially, by applying a control pressure at the flow-control
valve, the high-pressure connection of the return line is reset
and, by these means, the control pressure at the control valve is
lowered in order to open the connection between the hydraulic
regulating unit and the reservoir, which passes over the control
valve, and so, over the energy storage system in the form of a
spring, achieve an appropriate adjustment of the pump, which, in
view of the different controlling elements which are to be
energized, excludes a spontaneous adjustment of the variable
adjustment pump and likewise excludes the loss-affected
configuration of the discharge path over the control valve.
[0004] It is an object of the invention to provide a simplified
system for controlling a hydraulic variable displacement pump,
which makes possible a practically sudden response in the changing
over of the variable displacement pump to higher, especially
maximum flow rates and, with that, also a sudden increase in the
operating pressure of the system.
[0005] This is achieved with the distinguishing features of claim
1, according to which the discharging cross section of the
controlling device is maximized towards the reservoir, when the
variable displacement pump is adjusted to the maximum pump
capacity, in such a manner, that there is quasi unrestricted
drainage, so that the sudden changeover of the variable
displacement pump over the energy storage system becomes possible.
A constantly high regulating power turns out to be advantageous for
the energy storage system within the scope of the invention. For
this purpose, the energy storage system is formed, for example, by
a highly tensioned spring and the spring advisability also has a
high spring rate. Within the scope of the invention, it proves to
be advantageous for the sudden changeover aimed for, if the
displaced volume is used to fill the spaces resulting from the
changeover, that is, for example, in relation to a piston as
control element, if the volume, displaced from the pressure space
on the cylinder side is passed to the back of the piston, such a
short-circuit connection usually making particularly short pipeline
distances and large transfer cross sections possible.
[0006] For energizing the hydraulic control device, which is
controlled quantitatively within the scope of the inventive
solution, the flow regulator preferably is energized as a function
of control parameters specified on the part of the consumer. In
relation to the use, for example, of the inventive system for
vehicles, other information, which can be derived, for example,
from driving dynamics, can be taken into consideration
preventively, so that, in energizing the flow regulator, a change
in the requirement behavior of the consumer, which is to be
expected, can also already be taken into consideration for
adjusting the variable displacement pump in an anticipatory
manner.
[0007] Within the scope of the invention, the flow-control valve
may also, optionally, be constructed adjustably and, if necessary,
be provided with an additional energizing device, especially with
regard to expanding the inventive basic concept to further
functions.
[0008] Within the scope of the invention, an adjustable restrictor
may be used in the simplest manner as a flow regulator, so that the
adjustment of the pump, or optionally also its adjustment to other
control positions may also be attained within the scope of the
invention by simple means.
[0009] For the flow-control valve, a construction with a control
piston, operating as a pressure-maintaining valve, has proven to be
appropriate. It controls the cross section of the passage from the
high-pressure side to the hydraulic control device and is
spring-loaded on the high-pressure side and in the opposite
direction. A pressure, which corresponds to the pressure exerted in
the pipeline connection between the flow-control valve and the flow
regulator and is exerted on the subsequent measurement restrictor
downstream from the flow control valve, is superimposed on the
spring loading.
[0010] Further details and distinguishing features of the invention
arise out of the claims. Moreover, the invention is explained below
by means of an example, which diagrammatically shows a system for
controlling a hydraulic variable displacement pump for a
consumer.
[0011] In the system for controlling a hydraulic variable
displacement pump 1 for a consumer 2, shown in FIG. 1, the consumer
2 is in a supply cycle with a variable displacement pump 1 between
a suction pipeline 5 and a pressure pipeline 6 and connection of
the consumer 2 to the pressure pipeline 6 over the supply pipeline
3 and to the suction pipeline 5 over the drainage pipeline 4, with
a connection to the reservoir 24 on the suction side. A return
pipeline, symbolized by the return pipeline 27, extends between
connections 25 and 26 on the pressure side and the suction side
respectively and is shown as being in the transition from the
pressure pipeline 6 to the intake pipeline 3 or from the drainage
pipeline 4 to the suction pipeline 5. There is a flow control above
12 and a flow regulator 13 in the return pipeline 27 in the flow
direction from the connection 25 on the pressure side to the
connection 26 on the suction side.
[0012] The variable displacement pump 1 is shown highly
diagrammatically as a rotary vane pump with a lifting ring 7, which
can be adjusted relative to a rotor, which is not shown, with an
axis 8 attached to the housing for changing the pump capacity of
the variable displacement pump 1. On the one hand, an energy
storage device 9, formed by a spring arrangement, and, on the
other, a hydraulic control device 10, illustrated by a
piston-cylinder arrangement, are provided as control device. The
lifting ring 7 can be adjusted over the spring arrangement, which
forms the energy storage device 9, in the sense of raising the pump
capacity and, when acted upon in the opposite direction over the
control device 10, that is, against the force of the spring, in the
sense of lowering the pump capacity.
[0013] With respect to its supply, the hydraulic control device 10
lies in the return pipeline 27 between the flow regulating above 12
and the flow regulator 13, the free cross section of which is
variable and which is formed, for example, by an adjustable
restrictor.
[0014] Supplementary to its symbolic representation in FIG. 1, the
flow-control valve 12 is shown diagrammatically and constructively
in FIG. 2 and comprises a pressure-maintaining valve in the form of
a control slide valve 14, which, depending upon its position,
connects the pipeline section 16 of the return pipeline 27,
starting out from the pressure side (pressure pipeline 6), over an
annular channel 15 with the pipeline section 17, which runs out to
the hydraulic control device 10 and in which there is a measurement
restrictor 18. The control slide valve 14 is acted upon at the
front side by pressure and moreover, on its front, high-pressure
side 19 over the branch 20 to the pipeline section 16, and at its
opposite front side 21 over the branch 20, which starts out from
the pipeline section 17 downstream from the measurement restrictor
18, a compensation spring 23 being supported additionally at the
front side 21.
[0015] The hydraulic control device 10 is shown as a piston
cylinder unit, the piston 28 being supported at the lifting ring 7
and the pipeline section 17 discharging into the pressure space 29,
which is bounded by the piston 28 and going over into the pipeline
section 30 of the return pipeline 27 containing the flow regulator
13. As shown in FIG. 2, the dimensions of the cross section of this
pipeline section 30 with regard to the maximum amount flowing
through are such that an almost loss-free drainage and thus
unrestricted drainage towards the suction side of the reservoir 24
is possible. Correspondingly, and this is not shown, the passable
cross section of the flow regulator 13, which is constructed as an
adjustable restrictor, is adapted to such a maximum drainage cross
section.
[0016] In view of an as unrestricted a drainage and as rapid a
pressure relief as possible in the pressure space 29, it is
furthermore advantageous if a branch 31 of the pipeline 30
discharges in the rear area 32 of the piston, so that, as shown
diagrammatically, the volume, displaced in each case when the
variable displacement pump 1 is changed over to a higher pumping
capacity by way of the energy storage device 9, is used to fill
cavities resulting from the changeover. This is done along the
shortest path. Such a short-circuit connection may also be
realized, and this is not shown, internally in the housing of the
variable displacement pump. With such a short-circuit connection,
it is not only possible to avoid pressure differences, which retard
the adjustment, but also even to use the remaining residual
pressure even for adjusting the piston, in addition to the
regulating power of the energy storage system 9. The cross section
of the pipeline 13, leading to the reservoir 24, can also be
reduced by such a short-circuit connection.
[0017] Pursuant to the invention, the sudden decrease in pressure
in the pressure space 29 is attained by maximizing the drainage
cross section, including the cross section of the fully opened
restrictor, which forms the flow regulator 13. This is accomplished
at a low cost. Admittedly, minor delays may be associated with the
hard design of the energy storage system appropriate for this
purpose with the constantly high regulating power, for example, by
using a spring, which is under a high tension and preferably also
has a high spring rate for adjusting in the opposite direction.
However, no noticeably disadvantageous effects are associated with
these delays either energetically or with respect to the function
of the system.
[0018] As a result of the design of the flow-control valve 12, as
the pressure drops in the pipeline section 17, which runs out to
the control device 10, the passable cross section from the pipeline
section 16 to the pipeline section 17 is decreased by the control
slide 14, so that, when the passable cross section of the flow
regulator 13 expands, there is initially a rapid decrease in
pressure in relation to the hydraulic control device 10.
Correspondingly, there is also a decrease in pressure in pipeline
section 16. Accordingly, if, starting out from an appropriate
energizing of the flow regulator 13 by enlarging the drainage cross
section, the pressure of the control device 10 is relieved, the
flow into the control device over pipeline section 17 is also
simultaneously reduced, even if only briefly, until the flow rate
is adjusted once again over the flow-control valve 12 working as a
pressure-maintaining valve. A corresponding regulating effect also
results in the case of a demand request over the consumer 2 with a
reduction in pressure in the intake pipeline 3 and a corresponding
reduction in the pressure in the pipeline section 16 of the return
pipeline 27, so that the response behavior of the system is also
affected positively in this way.
* * * * *