U.S. patent application number 17/299283 was filed with the patent office on 2022-02-17 for controllable screw spindle pump.
The applicant listed for this patent is NIDEC GPM GmbH. Invention is credited to Franz PAWELLEK.
Application Number | 20220049697 17/299283 |
Document ID | / |
Family ID | 1000005989486 |
Filed Date | 2022-02-17 |
United States Patent
Application |
20220049697 |
Kind Code |
A1 |
PAWELLEK; Franz |
February 17, 2022 |
Controllable Screw Spindle Pump
Abstract
A controllable screw spindle pump for the lubricating oil supply
of an internal combustion engine comprises a pump housing (1), in
which a throttle chamber (13) and a control chamber (14) are
configured which are in contact with the lubricating oil to be
conveyed; wherein the throttle chamber (13) is arranged between the
pump inlet (10) and the spindle chamber (12), and the throttle
chamber (13) comprises a throttle valve (3), by way of which a
throughflow cross section of a conveying stream can be set; and the
control chamber (14) comprises a hydraulic control valve (4) with a
piston (40) which responds to a hydraulic control pressure (p1, p2)
in the control chamber (14), and the control chamber (14) is
oriented parallel to the spindle chamber (12) in relation to an
actuating travel of the piston (40); and a valve body (30) of the
throttle valve (3) is coupled to the piston (40) of the hydraulic
control valve (4).
Inventors: |
PAWELLEK; Franz; (Lautertal,
DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
NIDEC GPM GmbH |
Auengrund Ot Merbelsrod |
|
DE |
|
|
Family ID: |
1000005989486 |
Appl. No.: |
17/299283 |
Filed: |
November 14, 2019 |
PCT Filed: |
November 14, 2019 |
PCT NO: |
PCT/EP2019/081324 |
371 Date: |
June 2, 2021 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F04C 2/16 20130101; F04C
2240/50 20130101; F04C 14/24 20130101; F04C 2210/206 20130101; F04C
2240/60 20130101 |
International
Class: |
F04C 2/16 20060101
F04C002/16; F04C 14/24 20060101 F04C014/24 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 10, 2018 |
DE |
10 2018 131 587.2 |
Claims
1-7. (canceled)
8. A controllable screw pump for supplying lubrication oil to a
combustion engine, comprising: a pump housing with a spindle
chamber as well as a pump inlet and a pump outlet communicating
with the spindle chamber; at least two screw spindles rotatably
accommodated in the spindle chamber, the screw spindles being
driven by the combustion engine; wherein inside the pump housing, a
throttle chamber and a control chamber are provided, which are in
contact with the lubrication oil to be conveyed; wherein the
throttle chamber is situated between the pump inlet and the spindle
chamber, and the throttle chamber includes a throttle valve, via
which a flow cross-section of a delivery flow is settable; the
control chamber includes a hydraulic regulating valve with a piston
that responds to a hydraulic control pressure inside the control
chamber, and the control chamber is arranged in parallel to the
spindle chamber with reference to a displacement of the piston; and
a valve body of the throttle valve is coupled with the piston of
the hydraulic regulating valve.
9. The controllable screw pump according to claim 8, wherein a
displacement of the valve body of the throttle valve is arranged in
parallel to the spindle chamber, and a valve seat of the throttle
valve is provided at a mouth of the pump inlet into the throttle
chamber.
10. The controllable screw pump according to claim 8, wherein the
valve body of the throttle valve and the piston of the hydraulic
regulating valve are seated on a common valve stem.
11. The controllable screw pump according to claim 8, wherein the
screw pump comprises two screw spindles, wherein a cross-section of
the spindle chamber is formed by two overlapping circle radii, and
a cross-section of the control chamber is situated in the area of
an intersection axis of an overlap of the circle radii next to the
spindle chamber.
12. The controllable screw pump according to claim 8, wherein the
control chamber comprises two hydraulic connections for introducing
two hydraulic control pressures that act on opposing sides of the
piston of the hydraulic regulating valve.
13. The controllable screw pump according to claim 8, wherein a
compression spring is situated inside the control chamber on one
side of the piston of the hydraulic regulating valve.
14. The controllable screw pump according to claim 8, wherein the
pump housing comprises at one end face of the spindle chamber a
collar portion that includes a passage for the housing and a shaft
bearing for a drive shaft, and a gear rim that is seated on the
drive shaft comprises a radial cut-out for the collar portion so
that a toothing of the gear rim and the shaft bearing overlap
axially.
Description
[0001] The present invention relates to a controllable screw pump
having compact dimensions which is suitable for supplying
lubrication oil to combustion engines in vehicles, more
particularly passenger cars.
[0002] In vehicles, vane pumps and geared pumps are generally used
as oil pumps which are driven by a drive shaft of the combustion
engine. Vane pumps and geared pumps are displacement pumps which
have a small axial dimension and are also available as variants
with a variable pump geometry. A variable geometry can change the
delivery volume in relation to the shaft rotation, whereby in
particular in relation to applications with rotational speeds which
fluctuate greatly, such as when operating combustion engines in
passenger cars, a delivery amount or oil pressure can be
adapted.
[0003] After many years' optimisation, vane pumps achieve an
overall degree of efficiency of approximately 70% in a favourable
operating point. Within wide ranges of the rotational
speed-pressure characteristic map, the overall degree of
efficiently falls greatly, e.g. at high rotational speeds to merely
35%. Furthermore, the technical maturity of these types of pump
does not allow the expectation of much room for further
improvements in the degrees of efficiency.
[0004] In contrast, screw pumps operate with degrees of efficiency
of 70% to 85% at the rotational speeds, pressures and volume flows
with low-viscous lubrication oils which are typical for lubrication
oil applications. Accordingly, further potential savings in fuel
consumption and CO.sub.2 emission could be achieved by using screw
pumps.
[0005] The structure of screw pumps comprises no delicate elements
or sliding fits, whereby, even with long intervals between
maintenance operations, the type of pump is relatively insensitive
to becoming contaminated with soot or metal abrasion in the
lubrication oil. In addition, they have a high power density,
whereby they can achieve high delivery pressures in relation to a
supply of lubrication oil.
[0006] However, screw pumps are fixed displacement pumps, the
displacement volume of which cannot be adjusted. Furthermore, the
structure is of a larger axial dimension compared with a vane pump
or a geared pump owing to the screw spindles. As a result, the use
of screw pumps as oil pumps is known predominantly for supplying
lubrication oil to large-volume combustion engines in ships or even
lorries in which more installation space is available and the
combustion engine is operated at a relatively constant rotational
speeds.
[0007] If a screw pump is used in the application as an oil pump,
the delivery pressure may exceed the permissible operating range of
the oil pressure in the combustion engine during rapid rotational
speed increases or high rotational speeds. In said applications in
ships or lorries, e.g. the delivery volume of the screw pump is
adjusted in that some of the delivery volume recirculates through
an adjustable bypass from an outlet back to an inlet of the screw
pump and runs through the spindle chamber once again, whereby the
resulting delivery flow in the lubrication oil delivery system is
reduced. For instance, DE 10 2009 056 218 A1 describes a screw pump
on which a pressure-limiting valve with a return path is
integrated, whereby, above a set delivery pressure, a hydraulic
short-circuit is produced between the pressure side and suction
side of the pump. However, the response behaviour of such an
adjustment is relatively slow and appears to be unsuitable in view
of the rapid rotational speed fluctuations during operation of
internal combustion engines in passenger cars.
[0008] Patent application DE 10 2018 109 886.9 which was not yet
published on the filing date of the present invention and is by the
same applicant proposes an adjustable lubrication oil delivery
system for combustion engines in utility vehicles having an
improved response behaviour, in which suction throttling occurs
upstream of the screw pump. In the system, a pressure of the
lubrication oil downstream of the throttle valve and upstream of a
pump inlet is lowered to the negative pressure of the suction side
of the pump chamber or the spindle chamber, whereby a pressure
difference--which is necessary for filling the spindle chamber
within a rotational speed-dependent time--is not achieved. DE 10
2018 109 886.9 deals with the principle of suction throttling and
an implementation of the system in terms of control technology,
without addressing a specific design of the screw pump or the
upstream throttle valve in terms of the application in utility
vehicles or lorries.
[0009] As explained above, there is a need for an efficient screw
pump which is suitable for use as an oil pump in a passenger car.
Accordingly, an object of the present invention is to provide a
compact design for a screw pump and an adjustment of the delivery
amount.
[0010] The object is achieved by a controllable or an adjustable
screw pump having the features of claim 1.
[0011] The controllable screw pump is characterised in particular
in that, inside the pump housing, a throttle chamber and a control
chamber are provided, which are in contact with the lubrication oil
to be conveyed, wherein the throttle chamber is situated between
the pump inlet and the spindle chamber, and the throttle chamber
includes a throttle valve, via which a flow cross-section of a
delivery flow is settable; the control chamber includes a hydraulic
regulating valve with a piston that responds to a hydraulic control
pressure inside the control chamber, and the control chamber is
arranged in parallel to the spindle chamber with reference to a
displacement of the piston; and a valve body of the throttle valve
is coupled with the piston of the hydraulic regulating valve.
[0012] The invention thus provides for the first time an integrated
design of a screw pump and a hydraulically controlled suction
throttling.
[0013] The compact design of the controllable or adjustable screw
pump offers a solution for the need to have a considerably more
efficient supply of lubrication oil in passenger cars. In so doing,
the robust basic design of the screw pump with the advantages of
the high degree of efficiency, robustness and low pulsation over
other displacement pumps is retained.
[0014] By integrating the suction throttling in the pump housing,
the installation space and the installation of a component in the
lubrication oil system can be omitted. An assembly is produced
which is comparable to the known types of variable pumps with
variable geometry.
[0015] The arrangement of the hydraulic regulating valve in
parallel to the screw spindles allows a similar bounding geometry
of the pump housing, in which--despite the integration of the
suction throttling--the axial dimension remains substantially
unchanged and a radial dimension is increased to an insignificant
extent. Therefore, the optimisation of an installation space in new
systems or a replacement of the pump in current applications with a
predetermined installation space is facilitated.
[0016] The hydraulic implementation permits a higher power density
in relation to the actuating force for setting the suction
throttling, and so the hydraulic regulating valve can be smaller
compared with electric actuating members or the like and more
installation space is saved.
[0017] A high adjusting dynamic is achieved by the integrated
design. The invention is based on the knowledge that, during
suction throttling, down time between regulating engagement and
step response is in relation to the throttled suction path. As a
result of the short distance between the throttle valve and the
spindle chamber, the delivery amount can be changed in a highly
dynamic manner.
[0018] Advantageous developments of the adjustable lubrication oil
delivery system are the subject matter of the dependent claims.
[0019] According to one aspect of the invention, a displacement of
the valve body of the throttle valve can be arranged in parallel to
the spindle chamber, and a valve seat of the throttle valve can be
provided at a mouth of the pump inlet into the throttle chamber.
Therefore, the hydraulic regulating valve and also the throttle
valve are arranged in parallel to the spindle chamber, thus
favouring a compact design of the pump structure.
[0020] According to one aspect of the invention, the valve body of
the throttle valve and the piston of the hydraulic regulating valve
can be seated on a common valve stem. Therefore, there is no need
to separately guide the valve body of the throttle valve and the
integrated formation of both valves favours the compact design of
the pump structure.
[0021] According to one aspect of the invention, the screw pump can
comprise two screw spindles, wherein a cross-section of the spindle
chamber is formed by two overlapping circle radii, and a
cross-section of the control chamber can be situated in the area of
an intersection axis of an overlap of the circle radii next to the
spindle chamber. By way of this formation, the overall radial
dimension can be reduced, thus favouring the compact design of the
screw pump.
[0022] According to one aspect of the invention, the control
chamber can comprise two hydraulic connections for introducing two
hydraulic control pressures that act on opposing sides of the
piston of the hydraulic regulating valve. Therefore, in addition to
one variant of a hydraulic regulating valve in which a control
pressure acts against a spring bias, another variant in relation to
the hydraulic actuation is provided which is less critical in terms
of sealing the piston.
[0023] According to one aspect of the invention, a compression
spring can be situated inside the control chamber on one side of
the piston of the hydraulic regulating valve. A compression spring
can be used to provide a fail-safe function, and so a suction
throttling can be set to a predetermined or complete opening
position of the valve element in the case of a loss in control
pressure owing to a failure in the hydraulic actuation.
[0024] According to one aspect of the invention, the pump housing
can comprise at one end face of the spindle chamber a collar
portion that includes a passage for the housing and a shaft bearing
for a drive shaft, and a gear rim that is seated on the drive shaft
can comprise a radial cut-out for the collar portion so that a
toothing of the gear rim and the shaft bearing overlap axially. By
way of this formation, the overall axial dimension can be reduced,
thus favouring the compact design of the screw pump.
[0025] The invention will be explained hereinafter with the aid of
an embodiment and with reference to the accompanying drawing,
[0026] FIG. 1 shows a simplified schematic sectional view through
the design of one embodiment of the controllable screw pump in
accordance with the invention.
[0027] In the embodiment of the schematic illustration of FIG. 1, a
relative dimension of a hydraulic regulating valve 4 has been
selected in favour of improved perception.
[0028] However, the hydraulic regulating valve 4 can likewise be
smaller. Furthermore, to avoid a superimposed illustration of the
hydraulic regulating valve 4 with a spindle chamber 12, in FIG. 1 a
position of the hydraulic regulating valve 4 is shown offset with
respect to the spindle chamber 12. However, a position and distance
of the hydraulic regulating valve 4 with respect to the spindle
chamber 12 can likewise vary in favour of a more compact
arrangement.
[0029] In terms of this disclosure, the term `screw pump` is
understood to mean skew rotary piston pumps with a thread pitch for
displacement of the delivery medium. Such types of pump generally
comprise a driven screw spindle 2a and at least one further screw
spindle 2b which is dragged via engagement of the toothing.
[0030] The screw pump of the illustrated embodiment has one driven
screw spindle 2a and one dragged screw spindle 2b which are
rotatably accommodated in a spindle chamber 12 of a pump housing
10. The driven screw spindle 2a communicates with a drive shaft 5
which is driven by a combustion engine via a gear rim 50. The drive
shaft 5 exits the pump housing 1 in a collar portion 15. A shaft
bearing 51 in the form of a compact bearing having two rows of ball
bearings is fitted in the collar portion 15. The gear rim 50 is
seated on the free end of the drive shaft 5, protruding therefrom,
and has a bulge for the collar portion 15, and so a radial outer
toothing axially overlaps with the shaft bearing 51.
[0031] A pressure side of the spindle chamber 12 which communicates
with a pump outlet 11 in the form of a pressure connection is
located on the drive side of the screw spindles 2a, 2b. A suction
side of the spindle chamber 12 is located on the side of the screw
spindles 2a, 2b opposite the drive. The suction side of the spindle
chamber 12 communicates with a pump inlet 10 in the form of a
suction connection via a throttle chamber 3. In consideration of
the delivery direction, lubrication oil is sucked through by a
negative pressure on the suction side of the spindle chamber 12,
which is generated by a screw pitch of the rotating screw spindles
2a, 2b, via the pump inlet 10 and the throttle chamber 3, is
conveyed through the spindle chamber 12 and ejected out of the
spindle chamber 12 on the pressure side via the pump outlet 11.
[0032] A suction path upstream of the screw pump leads to an oil
sump of the combustion engine. Downstream of the screw pump, a feed
path of a lubrication oil delivery system, not illustrated, is
provided. The feed path leads to branches of a lubrication oil
supply of the combustion engine which serves to lubricate sliding
surfaces between moving parts in a crank drive, a valve drive and
cylinder barrels and the like under a required oil pressure.
[0033] The throttle chamber 13 of the pump housing 1 forms an inlet
chamber at an end face of the spindle chamber 12. An annular valve
seat 31 of a throttle valve 3 is formed at a mouth, at which the
suction connection of the pump inlet 10 enters the throttle chamber
3. A valve body 30 of the throttle valve 3 is guided at a valve
stem 34 axially opposite the suction connection of the pump inlet
10 and has a spherical sealing surface. By way of an opening
position along a displacement of the valve body 30 with respect to
the valve seat 31, a flow cross-section of the delivery flow of the
lubrication oil between the pump inlet 10 and the spindle chamber
12 is set or limited, whereby a suction throttling of the screw
pump is performed. On the other side of the valve stem 34 opposite
the valve body 30, there is arranged a piston 40 which is
accommodated in a cylindrical control chamber 14 of the pump
housing 1. The piston 40 and the control chamber 14 form a
hydraulic regulating valve 4 which sets an opening position of the
throttle valve 3 by a controlled supply of pressure of the
lubrication oil.
[0034] The spindle chamber 12 has a cross-sectional contour in the
form of a so-called Figure-of-eight housing, i.e. it is formed by
two bores in the pump housing 1 with overlapping radii in order to
ensure engagement of the screw spindles 2a, 2b. The cylindrical
control chamber 14 of the hydraulic regulating valve 4 is likewise
formed by a bore in the pump housing 1 which extends in parallel to
the bores of the spindle chamber 12. In a preferred compact
embodiment which differs from the schematic illustration in FIG. 1,
the cylindrical control chamber 14 is arranged close to a bulge of
the Figure-of-eight housing, i.e. between the axes of the bores of
the spindle chamber 12 close to a chamber wall of the spindle
chamber 12, and so a tight packing of cylindrical cavities and thus
a compact bounding geometry of the pump housing 1 is created.
[0035] The integrated arrangement of the hydraulic regulating valve
4 and of the throttle valve 3 is separated by a common stem guide
43 which is formed between the control chamber 14 and the throttle
chamber 13. The stem guide 43 provides an axial guide for the
common valve stem 34. A position of the piston 40 along a
displacement of the hydraulic regulating valve 4 is set by two
hydraulic control pressures p1 and p2 which prevail on both sides
of the piston 40 in the control chamber 14. The control pressure p1
is generated via a hydraulic connection 41 on one side of the
piston 40 in the control chamber 14. The control pressure p2 is
generated via a hydraulic connection 42 on the other side of the
piston 40 in the control chamber 14. An actuating movement of the
piston 40 is responsive to a pressure difference between the two
control pressures p1, p2 and retains a position in the event of an
equilibrium of forces on both sides of the piston 40.
[0036] On the side of the control pressure p1, a compression
spring, not shown, is preferably arranged which intervenes in the
force ratio of the control pressures p1, p2. The length of the
compression spring is selected such that without the two control
pressures p1, p2 a closed position of the throttle valve 3 is
prevented. The use of a compression spring ensures a fail-safe
function, and so in the event of a failure in the hydraulic
adjustment, stopping of the lubrication oil supply whilst the
combustion engine is running is prevented by a closed throttle
valve 3. Likewise, a complete opening position of the throttle
valve 3 can optionally be prevented by a further compression spring
on the opposite side. Depending upon the configuration of the
lubrication oil system, a critical delivery pressure will not be
exceeded in the event of a failure in the hydraulic adjustment.
[0037] A hydraulic actuation of the two control pressures p1, p2
occurs in a lubrication oil system, not illustrated, via an
electric-hydraulic regulating device which is fed from the
lubrication oil circuit of the combustion engine and by the
delivery pressure of the screw pump. Such an electric-hydraulic
regulating device has an electromagnetic 4/3 proportional valve.
The 4/3 proportional valve comprises four connections, including an
input connection for the supply of oil from an oil gate of the
combustion engine and three output connections, two output
connections of which provide the two control pressures p1, p2 with
a controlled pressure difference and one output connection of which
returns oil having an excess differential pressure from the
adjustment into the oil sump. The output connections of the two
control pressures p1, p2 are adjusted by means of a valve body
which sets a respective hydraulic resistance and thus a respective
pressure difference between the input connection and the three
output connections. The valve body is adjusted by an
electromagnetic actuating member having a coil and an anchor, and
by a compression spring. The electromagnetic actuating member is
actuated by a pulse width modulation of a supplied electrical
power. A control of the control pressures p1, p2 of the hydraulic
regulating valve 4 for adjusting the delivery volume of a
lubrication oil circuit via the suction throttling of the throttle
valve 3 in the screw pump can be effected by a control device in
dependence upon a load, a rotational speed and a temperature of the
combustion engine.
LIST OF REFERENCE NUMERALS
[0038] 1 Pump housing [0039] 2a Driven screw spindle [0040] 2b
Dragged screw spindle [0041] 3 Throttle valve [0042] 4 Hydraulic
regulating valve [0043] 5 Drive shaft [0044] 10 Pump inlet [0045]
11 Pump outlet [0046] 12 Spindle chamber [0047] 13 Throttle chamber
[0048] 14 Control chamber [0049] 15 Collar portion [0050] 30 Valve
body [0051] 31 Valve seat [0052] 34 Valve stem [0053] 40 Piston
[0054] 41 Hydraulic connection with control pressure p1 [0055] 42
Hydraulic connection with control pressure p2 [0056] 43 Stem guide
[0057] 50 Gear rim [0058] 51 Shaft bearing
* * * * *