U.S. patent application number 13/803123 was filed with the patent office on 2013-11-21 for actuator system for a controlled coolant pump.
This patent application is currently assigned to SCHAEFFLER TECHNOLOGIES AG & CO. KG. The applicant listed for this patent is SCHAEFFLER TECHNOLOGIES AG & CO. KG. Invention is credited to Andreas Nendel, Markus Popp.
Application Number | 20130309103 13/803123 |
Document ID | / |
Family ID | 49510939 |
Filed Date | 2013-11-21 |
United States Patent
Application |
20130309103 |
Kind Code |
A1 |
Popp; Markus ; et
al. |
November 21, 2013 |
ACTUATOR SYSTEM FOR A CONTROLLED COOLANT PUMP
Abstract
A coolant pump of an internal combustion engine, with a pump
housing and a hollow shaft rotatably mounted therein. Coolant is
delivered via an impeller wheel from a suction connection. The flow
is controlled by a guide plate on the impeller wheel that is
variably displaceable axially between two end positions. The guide
plate is adjustable by a push rod actuator guided in the pump
shaft. The actuator has a radial piston pump integrated within the
coolant pump with an intake piston and a counterpiston guided in
the pump shaft, that are inserted lying opposite one another and
delimit a pressure space. The pistons are enclosed outside by a
linearly displaceable control element guided in the pump housing.
Adjustment of the control element takes place as a function of a
rotary angle of the pump shaft via an actuator unit having an
electrically operated actuating element and a linear freewheel.
Inventors: |
Popp; Markus; (Bamberg,
DE) ; Nendel; Andreas; (Hessdorf, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SCHAEFFLER TECHNOLOGIES AG & CO. KG |
Herzogenaurach |
|
DE |
|
|
Assignee: |
SCHAEFFLER TECHNOLOGIES AG &
CO. KG
Herzogenaurach
DE
|
Family ID: |
49510939 |
Appl. No.: |
13/803123 |
Filed: |
March 14, 2013 |
Current U.S.
Class: |
417/215 |
Current CPC
Class: |
F05D 2270/64 20130101;
F04D 13/12 20130101; F04B 49/005 20130101; F04D 15/0038
20130101 |
Class at
Publication: |
417/215 |
International
Class: |
F04B 49/00 20060101
F04B049/00 |
Foreign Application Data
Date |
Code |
Application Number |
May 15, 2012 |
DE |
102012208103.8 |
Claims
1. A coolant pump of an internal combustion engine, comprising a
pump housing in which a pump shaft is mounted rotatably, the pump
shaft is configured as a hollow shaft and has an associated
impeller wheel connected on one end thereof which delivers a
coolant as volumetric flow via a suction connection into a spiral
channel, a guide plate on the impeller wheel to adjust a volumetric
flow that is axially displaceable between two end positions in an
infinitely variable manner and is connected in a rotationally rigid
manner to a push rod that is guided in the pump shaft and is
connected to an actuator system, the actuator system comprises a
radial piston pump which is integrated within the coolant pump and
includes a main or intake piston and a counterpiston, which are
guided in a through hole of the pump shaft, and are inserted so as
to lie opposite one another, to delimit a pressure space, and are
enclosed on an outside by a radially or linearly displaceable
control element which is guided in a cutout in the pump housing, an
adjustment of which takes place via an actuator unit which includes
an electrically operated actuating element and a linear
freewheel.
2. The coolant pump as claimed in claim 1, wherein a clamped
assembly of the linear freewheel of the actuator unit, which makes
a self-locking action possible, comprises at least two clamping
bodies which are inserted in a guide sleeve, are guided on an
outside on a cutout of the pump housing and on an inside enclose a
clamping cone which is assigned to the control element.
3. The coolant pump as claimed in claim 2, wherein the clamping
cone which tapers in a direction of the guide sleeve engages in
regions into the guide sleeve and is enclosed by a compression
spring which is inserted between the control element and the guide
sleeve.
4. The coolant pump as claimed in claim 3, wherein, for a powerless
actuating element, the compression spring exerts an axial force
which releases the clamped assembly of the linear freewheel and
moves it into an initial position or a neutral position.
5. The coolant pump as claimed in claim 1, wherein an electromagnet
is provided as the actuating element for the actuator unit.
6. The coolant pump as claimed in claim 1, wherein the actuator
unit provides a range of force of .gtoreq.10 N for the actuating
element, the compression spring has a range of force of from
.gtoreq.1.2 N to .ltoreq.3 N, and the linear freewheel has a wedge
angle .alpha. of .ltoreq.5.7.degree. with a coefficient of friction
.mu. of 0.1 in order to achieve a self-locking action.
7. The coolant pump as claimed in claim 1, wherein an eccentricity
(E) of the main piston and counterpiston which are offset by
180.degree. with respect to one another and are guided on an inner
contour of the control element can be influenced by the control
element which is inserted in the pump housing such that it is
sealed, fixed rotationally and displaceable radially in an
infinitely variable manner.
8. The coolant pump as claimed in claim 1, wherein a spring element
is inserted between the main piston and the counterpiston of the
radial piston pump, and the main piston includes an intake channel
or an intake valve for entry of hydraulic fluid, and the hydraulic
fluid exits into the pressure space via a one-way valve.
9. The coolant pump as claimed in claim 8, wherein, in the
actuation phase, a partial quantity of the hydraulic fluid is
displaced, in the case of a pressure gradient, out of the pressure
space via a closing valve of the pump shaft into a high pressure
space, in which an actuating piston which is coupled to the push
rod of the guide plate is loaded.
10. The coolant pump as claimed in claim 1, wherein, as a failure
safeguard for the actuator system, the push rod interacts with a
failsafe device which comprises a spring element.
Description
INCORPORATION BY REFERENCE
[0001] The following documents are incorporated herein by reference
as if fully set forth: German Patent Application No.:
102012208103.8, filed May 15, 2012.
BACKGROUND
[0002] The invention relates to a controlled coolant pump for an
internal combustion engine.
[0003] In the case of liquid-cooled, in particular water-cooled
internal combustion engines, the cooling water is guided in a
closed circuit through cooling channels of the crankcase and of the
cylinder head and is subsequently cooled again in an air/water heat
exchanger or radiator. A coolant pump which is, in particular,
driven directly via a belt drive is used to assist the circulation
of the coolant. A dependence of the pump rotational speed on the
rotational speed of the internal combustion engine is produced as a
result of the direct coupling between the coolant pump and the
crankshaft. It follows from this that, in the case of a cold start
of the internal combustion engine, the coolant circulates, as a
result of which desired rapid warming of the internal combustion
engine and an associated optimum operating temperature are delayed.
For the optimization of internal combustion engines with regard to
emissions and fuel consumption, it is appropriate to bring the
internal combustion engine to the operating temperature as quickly
as possible after the cold start. As a result, both the frictional
losses and, as a result, the fuel consumption and at the same time
the emissions values are reduced. In order to achieve this effect,
controllable coolant pumps are used, the delivered volumetric flow
of which can be adapted to the cooling requirement of the internal
combustion engine. For internal combustion engines which are
intended for vehicles, a coolant flow of <0.1 1/h, which is also
called a "zero leakage flow", is also aimed for in the cold running
phase.
[0004] DE 199 01 123 A1 has disclosed, as a measure to influence
the delivery volume of a coolant pump, assigning to the impeller
wheel an outer slide which engages over it. In this way, the
effective impeller width of the impeller wheel can be changed and
set in the axial direction in an infinitely variable manner. Here,
the adjustment of the slide takes place by way of the rotation of a
thread-like guide. DE 10 2005 062 200 A1 discloses a controllable
coolant pump, in which a valve slide which can be displaced in the
direction of the pump shaft axis is introduced within the pump
housing in order to influence the delivery quantity. The slide of
annular configuration forms an outer cylinder which covers the
outflow region of the impeller wheel in a variable manner.
According to DE 10 2005 004 315 A1, the valve slide, which can also
be called a guide disk, is adjusted electromagnetically by way of a
magnet coil which is arranged in the pump housing. As an
alternative to this, a pneumatically or hydraulically operated
actuator, which includes push rods which are guided in the pump
housing in order to adjust the valve slide, is provided for the
adjustment of the valve slide according to DE 10 2005 062 200
A1.
SUMMARY
[0005] It is the object of the present invention to provide an
actuator system for a controllable coolant pump, which actuator
system is optimized in terms of installation space and costs, is
functionally reliable and ensures an adjustment of the guide plate,
which adjustment is tailored to requirements.
[0006] This objective is met by a controllable coolant pump having
one or more features of the invention. Advantageous refinements are
specified below and in the claims.
[0007] According to the invention, the actuator system which is
integrated within the coolant pump affords the advantage of
reducing the installation space and the production costs for
realizing an effective and functionally reliable controllable
coolant pump. For the generation of pressure, the construction
according to the invention comprises an actuator system having a
radial piston pump which is integrated within the coolant pump and
includes two pistons, a main piston and a counterpiston, which are
guided in a through hole of the pump shaft and are inserted so as
to lie opposite one another. The pistons which delimit a pressure
space are enclosed on the outside by a control element which forms
an eccentric, also called a slide and by way of which an
oscillating movement of the pistons can be triggered. A change in
the volumetric flow of the coolant pump via a guide plate
displacement is triggered by an adjustment of the control element
in the direction of a greater eccentricity. The radially or
linearly displaceable control element which is guided in a cutout
in the pump housing can be set via an actuator unit as a function
of a rotary angle of the pump shaft, which actuator unit includes
an electrically operated actuating element and a linear freewheel.
The required actuating force for adjusting the control element is
generated by the electric actuating element, it being possible for
the required actuating force to be reduced according to the
invention by the linear freewheel. In conjunction with the linear
freewheel, an adjustment of the control element can advantageously
be limited to rotary angle phases of the water pump shaft, in which
rotary angle phases a reduced pressure is set in the pressure space
of the radial piston pump. In the case of a pressure rise, the
adjustment is blocked temporarily by the linear freewheel until a
next rotary angle phase with reduced pressure is reached.
Consequently the control element can be adjusted with a relatively
low actuating force level of the actuator unit.
[0008] Due to the cyclical adjustment of the control element which
is carried out exclusively with reduced actuating forces, a small
and inexpensive electrical actuating element which is optimized in
terms of installation space can advantageously be used. Resetting
of the guide plate into an initial or neutral position in order to
achieve a large volumetric flow takes place automatically in the
case of a powerless actuating element as a result of centrifugal
forces which act on the linear freewheel and/or by an assisting
spring force. By use of the radial piston pump, the cooling medium
is sucked in from the cooling circuit or the coolant pump and is
transferred to a pressure space which lies in the coolant pump
shaft. A control pressure can be generated by way of the radial
piston pump in conjunction with a variable eccentricity, in order
to adjust the piston between zero or idling operation and a
variable stroke. Furthermore, the speed of the pressure build-up
and therefore the position of the guide plate with respect to the
impeller wheel can be controlled in an infinitely variable manner,
in order to achieve rapid warming of the internal combustion engine
after a cold start or to influence the engine temperature in a
targeted manner. In comparison with previous, for example
electric-motor, complex and expensive embodiments for realizing a
controllable coolant pump, the invention advantageously provides a
concept which is neutral in terms of installation space, easy to
assemble and inexpensive. Furthermore, the construction which is
easy to assemble of the actuator system according to the invention
does not impair the installation space in the region of the drive
or belt plane of the coolant pump. The actuator system can
therefore be realized within the packaging limits of a conventional
coolant pump, formed of pulley wheel, mounting, slide ring seal and
impeller wheel. Moreover, the concept according to the invention
which ensures a satisfactory actuating capability of the guide
plate and satisfies all the criteria from the client viewpoint can
be realized with standardized components.
[0009] According to one preferred refinement of the invention, the
linear freewheel of the actuator unit comprises at least two
clamping bodies which make a self-locking action possible depending
on defined variables and form a clamped assembly. To this end, the
clamping bodies are inserted in a guide sleeve and are guided on
the outside on the cutout of the pump shaft and on the inside on a
clamping cone. Furthermore, the clamping cone which tapers in the
direction of the guide sleeve and is connected to the control
element is enclosed by a compression spring which is inserted
between the control element and the guide sleeve. In the case of a
powerless actuating element or in the case of a relatively low
actuating force of the actuating element, the axial force of the
compression spring releases the clamping bodies and therefore the
clamped assembly and displaces the guide sleeve and the actuating
element into an initial or neutral position. An electromagnet, the
actuating force of which adjusts the linear freewheel, the control
element which is connected thereto, and the associated pistons, is
suitable, in particular, as electrical actuating element. On
account of the adjustment according to the invention which is
limited to rotary angle phases of the water pump shaft and
interacts with the linear freewheel, an electromagnet can
advantageously be used which is inexpensive and is optimized in
terms of installation space.
[0010] Furthermore, according to the invention, a design is
advantageously provided for the actuator unit, which design
provides a range of force of .gtoreq.10 N for the electrical
actuating element and a range of force of from .gtoreq.1.2 N to
.ltoreq.3 N for the compression spring which is inserted between
the linear freewheel and the actuating element. In order to achieve
a self-locking action, the clamping cone of the linear freewheel
has a wedge angle .alpha. of .ltoreq.5.7.degree., a coefficient of
friction .mu. of 0.1 being taken into consideration.
[0011] As a measure for ensuring the functional reliability of the
actuator system, the control element, which can be displaced
radially in an infinitely variable manner and influences the
eccentricity and therefore the stroke of the pistons of the radial
piston pump, is inserted in the pump housing such that it is
sealed. The pistons, the main piston and the counterpiston, which
are offset by 180.degree. with respect to one another are guided on
the inner contour of the control element which is still
rotationally fixed, such that they are mounted on sliding bearings
or antifriction bearings. A spring element which is inserted
between the pistons brings about an assisting nonpositive support
of the pistons on the control element. The main piston which is
configured as a hollow body includes an intake valve which
interacts with an intake or inflow channel of the pump housing, via
which the hydraulic fluid or coolant of the coolant pump enters
into the main piston in an intake phase. Moreover, a nonreturn or
one-way valve is integrated into the main piston, via which valve
the hydraulic fluid flows into the pressure space of the pump
shaft, which pressure space is delimited by the main piston and the
counterpiston. A further one-way valve, which is also called a
closing valve, is provided between the pressure space and an inflow
channel of a high pressure space of the pump shaft, in which high
pressure space an actuating or working piston, which loads the push
rod of the guide plate, is guided displaceably.
[0012] A defined leakage gap between the working piston and the
bore wall of the pump shaft ensures automatic escape of hydraulic
fluid out of the high pressure space into the coolant pump. This
takes place as soon as the electrical actuating element of the
actuator unit is switched to the powerless state, and the working
piston and at the same time the guide plate which is connected
thereto are displaced in the direction of an end position, as a
result of which the volumetric flow of the coolant pump is
increased.
[0013] Furthermore, it is possible according to the invention to
combine the actuator system with a failure safeguard or failsafe
device. To this end, the push rod is assigned a spring element, in
particular a compression spring, which, in the case of a
disruption, for example a power failure of the actuator unit,
displaces the push rod including the associated guide plate into
the neutral position, in which the maximum delivery or volumetric
flow of the coolant pump is set.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] In the following text the invention will be explained using
preferred embodiments with reference to the appended figures, in
which:
[0015] FIG. 1 shows a diagrammatic illustration of the construction
of a coolant pump having an integrated actuator system which is
constructed according to the invention,
[0016] FIG. 2 shows a coolant pump according to the invention in a
longitudinal section,
[0017] FIG. 3 shows a functional principle diagram of the radial
piston pump of the actuator system,
[0018] FIG. 4 shows a diagram of the force profile for adjusting
the control element of the radial piston pump, and
[0019] FIG. 5 shows a diagrammatic illustration of the clamped
assembly of the linear freewheel.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0020] FIG. 1 diagrammatically shows all the components of a
coolant pump 1 which is controlled according to the invention. The
coolant pump 1 which is intended to cool an internal combustion
engine 2 is driven via a traction mechanism drive 3. The traction
mechanism 4 of the traction mechanism drive 3 which is configured
as a belt drive connects a first pulley wheel 5 which is connected
to a crankshaft (not shown) of the internal combustion engine 2 to
a second pulley wheel 6 which is assigned to the coolant pump 1.
The delivery volume or the volumetric flow of the coolant pump 1
which is connected to a cooling circuit 7 can be set or controlled
via a hydraulically active actuator system 10 which is assigned to
a hydraulic circuit 8 and is integrated into the coolant pump 1.
The construction of the actuator system 10 comprises an
eccentrically adjustable radial piston pump 11 which interacts with
an actuator unit 15 which includes a linear freewheel 12 and an
actuable actuating element 13.
[0021] FIG. 2 shows the controllable coolant pump 1 in longitudinal
section and clarifies, in particular, the construction of the
actuator system 10. The coolant pump 1 comprises a pump housing 18,
in which a pump shaft 20 is mounted rotatably via an antifriction
bearing 21, which pump shaft 20 is configured as a hollow shaft and
is connected in a rotationally rigid manner to an impeller wheel
19. In the operating state of the coolant pump 1 in the case of a
rotating impeller wheel 19, the coolant flows as hydraulic fluid
axially via a suction connection 22 to the impeller wheel 19 and is
guided radially into a spiral channel 23 or pressure channel. Here,
a pump cover 24, which is connected to the impeller wheel 19, forms
a transition between the suction connection 22 and the spiral
channel 23. In order to influence the volumetric flow of the
coolant pump 1, a guide plate 25 which axially displaceably covers
the outflow region 26 in a variable manner is assigned to the
impeller wheel 19 in the outflow region 26 of the coolant pump 1.
To this end, the guide plate 25 is connected in a rotationally
fixed manner to a push rod 18 which can be displaced axially in the
pump shaft 20. Via the actuator system 10, the push rod 28 and, as
a result, the guide plate 25 can be positioned in an infinitely
variable manner between two end positions which are defined by the
pump cover 24 and a rear wall 27 of the impeller wheel 19.
According to the position of the guide plate 25 which is depicted
in FIG. 2 and is supported on the rear wall 27, a maximum
volumetric flow of the coolant pump 1 is set. The eccentrically
adjustable positive displacement pump of the actuator system 10,
which positive displacement pump is configured as a radial piston
pump 11, includes two pistons, a main piston 29 and a counterpiston
30, which lie opposite one another and are guided in a radial
through hole 31 of the pump shaft 20. On the outside, the pistons
29, 30 are enclosed by a control element 32 which can also be
called a slide and are supported nonpositively with a rounded
piston tip which is designed convexly or as a spherical cap on an
inner contour 33 of the control element 32 in the operating state
in a manner which is induced by centrifugal force and is assisted
by a spring element 37 which is inserted between the pistons 29,
30. The pistons 29, 30 can be displaced radially in the pump
housing 18 via the control element 32 in order to set an
eccentricity E between a rotational axis 35 of the coolant pump 1
and a rotational axis 36 of the control element 32. To this end,
the control element 32 is inserted in a cutout 34 of the pump
housing 18 such that it can be displaced radially or linearly and
in a sealing manner by a seal 38, and makes an eccentric adjustment
of the main piston 29 and of the counterpiston 30 possible. In
order to reduce the friction and therefore the wear, contact faces
of the pistons 29, 30 and the inner contour 33 of the control
element 32 are hardened locally or are coated, for example, with
Teflon or molybdenum and/or with a lubricant. As an alternative to
a sliding mounting, an antifriction mounting can be provided, in
which the pistons 29, 30 are enclosed by an intermediate ring which
encloses on the outside and includes a circumferential raceway for
rolling bodies, which raceway corresponds with a further inside
raceway of the control element 32, which raceway is of
complementary design.
[0022] The eccentricity E and, as a result, a stroke of the
oscillating pistons 29, 30 of the radial piston pump 1 can be set
directly via the actuator unit 15 of the actuator system 10. From
the, in particular, electrically operable actuating element 13 of
the actuator unit 15, an actuating force can be transmitted in the
arrow direction to a linear freewheel 12 and from there to the
control element 32. Here, the actuating element 13 is assigned a
guide sleeve 41 which is of cup-like design and is connected to the
linear freewheel 12. The linear freewheel 12 forms a clamped
assembly 39, which makes a self-locking action possible, with two
clamping bodies 40 which are positioned so as to lie opposite one
another and are inserted into local openings of the guide sleeve 41
of cup-like design. On the outer side, the clamping bodies 40 are
guided on the cutout 34 of the pump housing 18 and, on the inner
side, the clamping bodies 40 enclose a clamping cone 42 which
tapers in the direction of the guide sleeve 41 and is connected to
the control element 32. A cyclical adjustment of the control
element 32 with a relatively low actuating force, which adjustment
is limited to the intake phase of the main piston 29 of the radial
piston pump 11, can be realized by means of the actuator unit 15.
The actuating force which is exerted by the actuating element 13 is
transmitted to the guide sleeve 41, on account of direct support,
and from there directly to the control element 32. After the end of
the intake phase and the reaching of an increased pressure level
within the pressure space 49 which is delimited by the pistons 29,
30, the position of the control element 32 is held by the linear
freewheel 12 which locks in the arrow counterdirection. In the case
of a deactivated, powerless actuating element 13, the clamped
assembly 39 of the linear freewheel 12 is released, by a
compression spring 43, which encloses the clamping cone 42 and is
positioned between the control element 32 and the guide sleeve 41,
exerting an axial force which releases the clamping bodies 40.
Synchronously with this, the guide sleeve 41 and, as a result, the
control element 32 are displaced in the direction of a neutral or
initial position without eccentricity.
[0023] In the region of great eccentricity E, coolant flows as
hydraulic fluid via an intake valve 46 of the main piston 29 into a
piston interior space. A push-out opening 47 of the main piston 29
is assigned a one-way valve 48, via which the hydraulic fluid flows
into the pressure space 49 of the radial piston pump 11 in a
pumping phase of the radial piston pump 11. The intake valve 46 is
preferably connected to the spiral channel 23 or a pressure region
of the coolant pump 1, as a result of which the prevailing back
pressure assists the opening of the intake valve 46 at the
beginning of the intake phase of the main piston 29. The further
counterpiston 30 is provided for mass compensation or for radial
mass distribution with respect to the intake piston 29. In the
pumping phases which end at a rotary angle of 180.degree. and
360.degree. and follow the intake phases of the radial piston pump
11, the pressure in the pressure space 49 is boosted to a maximum.
Via a closing valve 51 which likewise acts as a one-way valve and
is inserted in a longitudinal bore 50 of the pump shaft 20, the
hydraulic fluid is displaced out of the pressure space 49 into a
high pressure space 52 of the pump shaft 20 during the actuation in
the pumping phase. Here, an actuating piston 54 which is guided
displaceably in the high pressure space 52 and is connected
indirectly via the push rod 28 to the guide plate 25 is
pressure-loaded. The closing valve 51 opens as soon as a pressure
gradient is set and the pressure in the pressure space 49 exceeds
the pressure level in the high pressure space 52. An actuating
movement of the push rod 28 and of the guide plate 25 which is
connected to it in the direction of the pump cover 24 is triggered
via the actuating piston 54 when the pressure in the high pressure
space 52 exceeds the spring force of a compression spring which can
also be called a failsafe device 56. The compression spring which
counteracts the actuating movement of the actuating piston 54 is
supported between a shoulder of the pump shaft 20 and the actuating
piston 54 and encloses the push rod 28 here. As a measure for
counteracting an uncontrolled pressure rise in the high pressure
space 52, a pressure relief valve can be integrated, for example,
into the pump shaft 20, which pressure relief valve opens when a
limit pressure is exceeded and makes an outflow of coolant out of
the high pressure space 52 possible. In order to ensure rapid
restoring of the guide plate 25, it is possible, furthermore, to
introduce a defined leakage gap, for example in the form of a
longitudinal channel, in the outer contour of the actuating piston
54, via which leakage gap coolant is discharged out of the high
pressure space 52 into an annular space which is intended for the
compression spring of the failsafe device 56 and from there via an
outflow opening of the pump shaft 20.
[0024] FIG. 3 shows a functional diagram of the radial piston pump
11 and FIG. 4 shows a diagram of the force profile which is
generated by the radial piston pump 11. As clarified by FIG. 3, one
revolution of the main piston 29 results in two intake operations
and two pumping operations, the phases of said operations differing
as a result of the eccentricity E which is set between the
rotational axis 35 of the pump shaft and the rotational axis 36 of
the radial piston pump 11. A short intake phase is set between
0.degree. and 90.degree. and a short pumping phase is set between
90.degree. and 180.degree.. Deviating from this, an extended intake
phase results between 180.degree. and 270.degree. and an extended
pumping phase results between 270.degree. and 360.degree.. The
diagram according to FIG. 4 graphically shows the force profile of
the radial piston pump 11 in relation to the rotary angle of the
radial piston pump 11, the rotary angle of the radial piston pump
11 being plotted on the abscissa and the force N being plotted on
the ordinate. As can be gathered from FIG. 4, a relatively low
force level is set in the intake phases between 0.degree. and
90.degree. and between 180.degree. and 270.degree., which
relatively low force level is used according to the invention to
adjust the control element 32 via the actuator unit 15.
[0025] FIG. 5 diagrammatically shows the clamped assembly 39 of the
actuator unit 15 and the forces which act for the clamping action.
In the pumping phases of the radial piston pump 11, a locking
function of the clamped assembly 39 is set, in which locking
function the clamping bodies 40 are supported nonpositively on the
outer side on the cutout 34 of the pump housing 18 and on the inner
side on the clamping cone 42 of the control element 32. In the
intake phases of the radial piston pump 11, the clamped assembly 39
is released from the actuating unit 13 of the actuator unit 15 by
the spring force F.sub.fed of the compression spring 43.
[0026] The following relations apply to the clamped assembly 39 of
the linear freewheel 12:
N-Fe.sub.exz/tan(.alpha.)=0; R-F.sub.fed-F.sub.exz=0; N=R/.mu.
[0027] In the case of the following assumptions: .mu.=0.1;
.alpha.=5.degree.; F.sub.exz =8 N, in the case of a powerless
actuating unit 13 of the actuator unit 15, a force F.sub.fed of the
compression spring 43 of 1.14 N is required to release the clamped
assembly 39 and restore the actuator unit 15.
LIST OF DESIGNATIONS
[0028] 1 Coolant pump
[0029] 2 Internal combustion engine
[0030] 3 Traction mechanism drive
[0031] 4 Traction mechanism
[0032] 5 Pulley wheel
[0033] 6 Pulley wheel
[0034] 7 Cooling circuit
[0035] 8 Hydraulic circuit
[0036] 10 Actuator system
[0037] 11 Radial piston pump
[0038] 12 Linear freewheel
[0039] 13 Actuating element
[0040] 15 Actuator unit
[0041] 18 Pump housing
[0042] 19 Impeller wheel
[0043] 20 Pump shaft
[0044] 21 Antifriction bearing
[0045] 22 Suction connection
[0046] 23 Spiral channel
[0047] 24 Pump cover
[0048] 25 Guide plate
[0049] 26 Outflow region
[0050] 27 Rear wall
[0051] 28 Push rod
[0052] 29 Intake piston
[0053] 30 Counterpiston
[0054] 31 Through hole
[0055] 32 Control element
[0056] 33 Inner contour
[0057] 34 Cutout
[0058] 35 Rotational axis
[0059] 36 Rotational axis
[0060] 37 Spring element
[0061] 38 Seal
[0062] 39 Clamped assembly
[0063] 40 Clamping body
[0064] 41 Guide sleeve
[0065] 42 Clamping cone
[0066] 43 Compression spring
[0067] 46 Intake valve
[0068] 47 Push-out opening
[0069] 48 One-way valve
[0070] 49 Pressure space
[0071] 50 Longitudinal bore
[0072] 51 Closing valve
[0073] 52 High pressure space
[0074] 54 Actuating piston
[0075] 56 Failsafe device
[0076] E Eccentricity
[0077] F.sub.fed Spring force
[0078] F.sub.exz Eccentric force
[0079] N Perpendicular force
[0080] R Frictional force
[0081] A Wedge angle
[0082] .mu. Coefficient of friction
* * * * *