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Claims  |
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I claim:
1. A vane cell installation for liquid flow media which comprises a rotor
means provided with at least approximately radial slot means, vane means
slidable within said slot means, an endless cam surface means surrounding
the rotor means and radially enclosing together with the rotor means at
least one sickle-shaped working space means, the cam surface means having
a radially outwardly directed inclination with respect to a circular
surface concentric to the center of rotation of the rotor means which
forms an inlet area during transversal of the cam surface means in a
predetermined direction corresponding to the operating direction, and a
corresponding radially inwardly directed inclination in at least one other
circumferential area of the cam surface means forming a discharge area,
two essentially plane base plate means axially sealingly enclosing on both
sides the rotor means together with the vane means and the cam surface
means and axially delimiting the working space means, internal connecting
channel means connecting the inlet area of the working space means with a
feed channel means and connecting the discharge area of the working space
means with a discharge channel means, a working medium supply means from a
part of the system which is subjected to the higher pressure level, to
bottoms of the slot means of the rotor means disposed in the inlet area by
way of flooding channel means and a working medium discharge means out of
the bottom of the slot means of the rotor means disposed in the discharge
area toward the high pressure side of the installation by way of emptying
channel means, characterized in that the working medium discharge means
takes place exclusively by way of a by-pass means including at least a
partial area of the axial extent of the bottoms of the slot means of the
rotor means disposed in the inlet area, and in that the flooding channel
means to said last-mentioned bottoms of the slot means terminates in said
slot bottoms at an axial position thereof disposed downstream with respect
to the connecting place of the emptying channel means, as viewed in the
flow direction of the working medium discharge.
2. An installation according to claim 1, characterized in that all slot
bottoms of the rotor means are in flow communication with each other by at
least one annular channel means, and in that only the slot bottoms of the
rotor means disposed in the inlet area are in direct communication with
the high pressure side of the installation.
3. An installation according to claim 1, characterized in that the slot
depth and the contour of the vane edge facing the slot bottom as well as
the slot bottom itself are so constituted that the remaining open cross
section between the vane edge and the slot bottom is relatively small in
the radially furthest pushed-back position of the vane means.
4. An installation according to claim 1, characterized in that the
connecting places of the annular channel means and of the flooding channel
means with the slot bottoms are arranged at the two axially mutually
opposite end faces fo the rotor means.
5. An installation according to claim 1, characterized in that the
connecting places of the annular channel means with the slot bottoms has
an axial spacing from the connecting place of the flooding channel means
with the slot bottoms which is relatively large.
6. An installation according to claim 5, characterized in that the annular
channel means is formed by an annular groove.
7. An installation according to claim 1, characterized in that all slot
bottoms of the rotor means are in flow communication with each other by at
least one annular channel means, the annular channel means is constructed
as an annular groove opening toward one of the two axially perpendicular
gaps between an end face of the rotor means and the corresponding base
plate means and axially machined into one of the two parts consisting of
rotor means and base plate means.
8. An installation according to claim 7, characterized in that the
connecting places of the flooding channel means with the slot bottoms are
constructed as aperture means machined axially into the other base plate
means and circumferentially extending substantially circularly shaped over
the corresponding inlet area, exclusively said aperture means having a
substantially unimpaired connection with the high pressure side of the
installation.
9. An installation according to claim 8, characterized in that the aperture
means machined into the base plate means on the flooding side of the rotor
means are constructed with respect to the open surface facing the axially
perpendicular gap between rotor means and base plate means at least
approximately of the same area as the corresponding area of the annular
groove channel means.
10. An installation according to claim 1, characterized in that the slot
bottoms of the vane means disposed respectively in a discharge area are
in-flow communication with the respective slot bottoms of the vane means
disposed in the adjacent inlet area which is located adjacent in a
predetermined circumferential direction, by way of respective arcuately
shaped channel means, and in that only the slot bottoms of the rotor means
disposed in the inlet area are in communication directly with the high
pressure side of the installation.
11. An installation according to claim 10, characterized in that each
arcuately shaped channel means is formed by a stationary part at least
with respect to the end walls thereof determining its axial dimension.
12. An installation according to claim 10, characterized in that the
connecting places of the arcuately shaped channel means with the slot
bottoms have a relatively large axial spacing from the connecting place of
the flooding channel means with the slot bottoms.
13. An installation according to claim 10, characterized in that the
arcuately shaped channel means and the end walls thereof are so arranged
circumferentially that the equalization flow from the discharge area to
the inlet area always takes place in the normal direction of rotation.
14. An installation according to claim 1, characterized in that the working
medium supply means is substantially unobstructed while the working medium
discharge means is throttled.
15. An installation according to claim 14, characterized in that the
working medium supply means takes place out of one of the two channel
means consisting of feed and discharge channel means which is subjected to
the higher pressure level.
16. An installation according to claim 14, characterized in that the
channel means subjected to the higher pressure is a corresponding internal
connecting channel means.
17. An installation according to claim 14, characterized in that the slot
means have substantially parallel walls.
18. An installation according to claim 14, characterized in that the rotor
means and the vane means as well as the ring means carrying the cam
surface means have substantially the same axial length and are delimited
by plane surfaces disposed axially perpendicular.
19. An installation according to claim 18, characterized in that all slot
bottoms of the rotor means are in flow communication with each other by at
least one annular channel means, and in that only the slot bottoms of the
rotor means disposed in the inlet area are directly in communication with
the high pressure side of the installation.
20. An installation according to claim 19, characterized in that the
connecting places of the annular channel means with the slot bottoms has
an axial spacing from the connecting place of the flooding channel means
with the slot bottoms which is relatively large.
21. An installation according to claim 20, characterized in that the
annular channel means is formed by an annular groove.
22. An installation according to claim 20, characterized in that the slot
depth and the contour of the vane edge facing the slot bottom as well as
the slot bottom itself are so constituted that the remaining open cross
section between the vane edge and the slot bottom is relatively small in
the radially furthest pushed-back position of the vane means.
23. An installation according to claim 22, characterized in that the
connecting places of the annular channel means and of the flooding channel
means with the slot bottoms are arranged at the two axially mutually
opposite end faces of the rotor means.
24. An installation according to claim 22, characterized in that the
annular channel means is constructed as an annular groove opening toward
one of the two axially perpendicular gaps between an end face of the rotor
means and the corresponding base plate means and axially machined into one
of the two parts consisting of rotor means and base plate means.
25. An installation according to claim 24, characterized in that the
connecting places of the flooding channel means with the slot bottoms are
constructed as aperture means machined axially into the other base plate
means and circumferentially extending substantially circularly shaped over
the corresponding inlet area, exclusively said aperture means having a
substantially unimpaired connection with the high pressure side of the
installation.
26. An installation according to claim 25, characterized in that the
aperture means machined into the base plate means on the flooding side of
the rotor means are constructed with respect to the open surface facing
the axially perpendicular gap between rotor means and base plate means at
least approximately of the same area as the corresponding area of the
annular groove channel means.
27. A pump according to claim 26, characterized in that the radial cross
section of the annular channel means is so selected as regards its open
cross-sectional area that the auxiliary feed flow which establishes itself
by reason of the feed action of the vane means radially sliding in the
rotor slot means, receives at minimum rotational speeds of the pump a
noticeable back pressure but, on the other, the back pressure of this
auxiliary feed flow at maximal rotational speeds of the pump remains
sufficiently far below that limit at which the radial abutment of the vane
means at the cam surface means menaces to cause a wear of the parts by
reason of the back pressure.
28. A pump according to claim 26, characterized in that the radial cross
section of the annular groove is so selected as regards its open
cross-sectional area that the auxiliary feed flow which establishes itself
by reason of the feed action of the vane means radially sliding in the
rotor slot means, receives at minimum rotational speeds of the pump a
noticeable back pressure but, on the other, the back pressure of this
auxiliary feed flow at maximal rotational speeds of the pump remains
sufficiently far below that limit at which the radial abutment of the vane
means at the cam surface means menaces to cause a wear of the parts by
reason of the back pressure.
29. An installation according to claim 28, characterized in that at least
two annular channel means are provided and fashioned as arcuately shaped
channel means, the slot bottoms of the vane means disposed respectively in
a discharge area are in-flow communication with the respective slot
bottoms of the vane means disposed in adjacent inlet area which is located
adjacent in a predetermined circumferential direction, by way of the
respective arcuately shaped channel means, and in that only the slot
bottoms of the rotor means disposed in the inlet area are in communication
directly with the high pressure side of the installation.
30. An installation according to claim 29, characterized in that each
arcuately shaped channel means is formed by a stationary part at least
with respect to the end walls thereof determining its axial dimension.
31. An installation according to claim 30, characterized in that the
connecting places of the arcuately shaped channel means with the slot
bottoms have a relatively large axial spacing from the connecting place of
the flooding channel means with the slot bottoms.
32. An installation according to claim 31, characterized in that the
arcuately shaped channel means and the end walls thereof are so arranged
circumferentially that the equalization flow from the discharge area to
the inlet area always takes place in the normal direction of rotation. |
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Claims |
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Description |
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The present invention relates to a vane cell device for liquid flow media,
especially to a vane pump or motor with a rotor provided with vanes
slidable in at least approximately radial parallel-walled slots and with
an endless cam surface which surrounds the rotor and together with the
same encloses radially at least one sickle-shaped working space, in which
the cam surface includes a radially outwardly directed inclination
(suction or inlet area) with respect to a circular path concentric to the
center of rotation of the rotor when running over the cam surface in one
predetermined direction (operating direction of rotation) and other
circumferential areas of the cam surface, in which the corresponding
inclination is directed radially inwardly (discharge area), whereby the
rotor and the vanes and preferably also the ring or the like carrying the
cam surface all possess axially an identical length and are delimited by
plane, axially perpendicularly surfaces, and which further comprises two
plane base plates axially sealingly enclosing the rotor together with the
vanes and the cam surface on both sides and axially delimiting the working
space or spaces, as well as internal connecting channels connecting the
suction or inlet area of the working space with the feed line of the
installation and the discharge area or areas of the working space with the
discharge channel of the installation, and further equipped with an
unobstructed working medium supply out of the one of the two channels
consisting of feed and discharge channel which is subjected to the higher
pressure level or out of the corresponding internal connecting channel or
channels of the installation (high pressure side) to the slot bottoms of
the rotor disposed in the suction or inlet area or areas by way of
flooding channels and with a throttled working medium discharge out of the
slot bottoms of the rotor disposed in the discharge area or areas to the
high pressure side of the installation by way of discharge or emptying
channels.
Known pumps of this construction are used for numerous possible feed and
pressure-producing tasks thus, for example, also for producing pressure in
hydraulic servo-steering systems in motor vehicles. The vanes of these
vane pumps are pressed radially against the cam surface, inter alia, by
the liquid pressure. More particularly, the vanes are subjected to the
centrifugal force, to a liquid pressure prevailing in the slot bottom and
eventually with certain types of construction to the pressure of a spring.
A reliable vane abutment, on the other hand, is necessary for a completely
satisfactory filling of the feed cells and for the pressure production.
Within the suction or inlet area, apart from the centrifugal force and an
eventual spring pressing action, the vanes of the aforementioned type are
forced into abutment by the pressure produced by the pump; within the
pressure area, they are subjected to a back-pressure built up in the slot
bottom which is higher than the feed pressure of the pump. The vanes which
slide radially to and fro during rotation of the rotor, more particularly,
operate together with the rotor slots like a radial piston pump whose
pressure area and suction or inlet area are disposed in-phase in the
circumferential direction with the corresponding areas of the vane pump.
This small auxiliary feed or supply flow produced by the pump action of
the vanes is held back or dammed up in the pressure area by a throttle and
thus effects the radial abutment of the vanes at the cam surface. A second
pressure increase step which supplies the auxiliary feed stream and which
builds up on the feed level of the vane pump is formed so to speak of,
whose feed flow is utilized and dammed up as back pressure for purposes of
vane abutment.
Advantageous in vane-type cells is their low-noise operation combined with
a relatively simple construction whereby the pump is inexpensive and
operationally reliable and prone to few troubles and failures. These
advantages open up to the pump also application possibilities in those
cases where only very small feed quantities are required, for example,
with the servo-steering systems or in the so-called comfort-hydraulics of
the motor vehicle construction. The small types of construction, however,
entail a disadvantage which becomes noticeable above all also particularly
aggravatingly when the pump is operated in cold ambient temperatures. This
disadvantage resides in that after an operating stoppage during which the
pump and the flow medium are cooled off to the ambient temperature, the
pump commences to feed only above a predetermined initial rotational speed
dependent on the oil viscosity, and upon exceeding this rotational speed,
a pressure build-up starts in the feed line suddenly. This stems from the
fact that, on the one hand, the vanes during each rotation of the rotor
are forcibly displaced at least once again radially inwardly and that, on
the other, as long as the pump itself does not feed, the liquid pressures
which cause abutment of the vanes cannot build up, but only the
centrifugal forces are effective. As to the rest, a spring installation in
the slot bottom is not acceptable in small pump constructions. With
smaller pump constructions, the centrifugal forces reach a significant
magnitude only with relative high rotational speeds by reason of the
slight vane weight, for example, of about two to three grams. The
centrifugal force, more particularly, not only has to overcome the
adhesive force of the oil but must also be so large that it is able to
suck in the viscous oil into the slot bottom in the short period of time
during the passage of a vane through the suction area, by an amount
corresponding to the displacement volume of the vane. For that purpose the
pump must have exceeded at least for a short period of time, the initial
rotational speed at which these oil forces are overcome by reason of the
centrifugal force influence. The colder and the more viscous the oil, the
higher this initial rotational speed, and not only because the oil is more
viscous but also because at the higher rotational speed, the filling time
of the slot bottoms are shorter. This may lead at especially low
temperatures to the fact that the oil present in the interior of the pump
and the pump parts have to be warmed up at first by an idling rotation of
the pump by reason of the friction loss in order that the oil can assume a
smaller viscosity. If the vanes of the rotor are thus once caused to abut
after exceeding the initial rotational speed, then the pump begins to feed
and a pressure is able to build up in the feed line; this pressure then
also contributes to the abutment of the vanes. Since this start of the
feed action and of the pressure build-up takes place at high pump
rotational speeds, the pump produces a forceful, strong pressure shock
with the beginning of the feed.
The vane pumps of the aforementioned type commence to operate from the
cooled-off condition initially only with a delay as regards rotational
speed and/or time and the feed and the pressure build up start shock-like.
This is at least very annoying even if not non-permissive for the
hydraulic system to be fed by the pump. However, these pressure shocks may
also produce in due course damages resulting therefrom. With the use in
servo-steering systems, this pressure shock, which becomes effective as a
strong jerk at the steering wheel, may lead to frightening the driver and
to an anxiety and apprehension on the part of the driver concerning the
operating safety of the steering system. The described starting
difficulties may also occur in vane-type mechanisms which are used as
hydraulic motor.
It is the aim of the present invention to so improve the installation of
the aforementioned type that the liquid pressures causing abutment of the
vanes can build up with a viscous flow medium already at very small
rotational speeds. This is achieved according to the present invention in
that the working medium discharge out of the slot bottoms of the vanes
disposed in the discharge area or areas, takes place at least partly by
way of a by-pass via at least one partial area of the axial extent of the
slot bottoms of the rotor disposed in the suction or inlet area or areas
and in that the flooding channels to these slot bottoms terminate in these
slot bottoms at an axial position disposed upstream in the flow direction
of the working medium discharge with respect to the connecting place of
the discharge channels.
The system, consisting of cam surface, vanes and rotor slots may--as
already mentioned--be considered as a small radial piston pump or motor.
Thanks to the by-pass according to the present invention of the discharge
of the flow medium of this radial piston installation out of the slot
bottoms which become smaller within the discharge area of the rotor, by
way of the slot bottoms disposed in the suction or inlet area of the
rotor, the discharge side of this radial piston pump or motor is at least
partially by-passed or short-circuited with the suction or inlet side
thereof and the volume forcibly displaced out of the slot bottoms in the
discharge area is initially fed into the slot bottoms disposed in the
suction or inlet area which become wider, and can build up thereat a
pressure cushion which displaces the vanes toward the outside. The oil
volumes present in the slot bottoms are therefore fed to and fro on the
inside of the rotor without the fact that a feed toward the outside could
be determined. The further aforementioned auxiliary flow is by-passed or
short-circuited in itself. Only at the slot bottoms which are disposed in
the suction or inlet area, the short-circuited or by-passed system is
connected to the high pressure side of the vane cell mechanism, properly
speaking, in order to superimpose from there a pressure corresponding to
the high pressure level of the pump or of the motor and to be able to
replenish the leakage losses in the by-passed or short-circuited system.
The advantages of the present invention in an application to pumps reside
in that the feed of the pump or motor commences during the starting phase
already at very low rotational speeds even with a viscous oil and at low
temperatures and in that a pressure commences to build up corresponding to
the supply flow increasing with the rotational speed, in the hydraulic
system connected downstream and more particularly softly and controllably
but very early. The early and soft start of the feed action additionally
eliminates during the beginning of the feed or supply vacuum shocks at the
pump suction side on the liquid which is viscous at the low temperatures.
Heretofore, vacuum shocks could be observed which by reason of the oil
viscosity could not be decreased sufficiently rapidly by an otherwise
existing flow of working oil out of the hydraulic system and led to
non-permissively high vacuums in the suction space over non-permissively
long periods of time. Normally, the shaft seal is connected at that place
where the pump shaft extends through the housing, with the suction or
inlet space of the pump or motor so that the pressure differences during
the pumping start can be conducted on to the shaft seal. With
non-permissively high and non-permissively long-lasting pressure vacuums,
however, the sealing lip might be lifted off from the pump shaft as a
result thereof and air, water or dirt can be sucked-in or sniffled-in into
the working oil. This not only leads to oil contaminations, pump wear and
premature oil aging, but also to a temporarily disturbing noise annoyance
until the sucked-in or sniffled-in air inclusions are again eliminated out
of the oil. The early and soft feeding start of the pump also permits the
use of oil types of higher viscosity and better lubricating properties
than heretofore, whence the operating properties of the pump, its length
of life, and its volumetric efficiency are improved. With the application
of such pumps to motor vehicle servo-steering systems, the advantages
follow therefrom that after a cold start the steering assist is present
immediately and that the disturbing turning jerk at the steering wheel is
avoided. Since a waiting duration for the starting of the steering assist
is dispensed with, also a transition from a steering free of servo-assist
to one with servo-assist is eliminated which even without a jerk-like
transistion, represents a moment of insecurity because the steering forces
required by the driver change thereby and an unintentional "pulling" of
the steering wheel is possible.
In a constructively particularly simple manner this by-pass according to
the present invention of the feed and suction spaces of the system acting
as radial pump of the vanes and of the slot bottoms in the rotor as well
as the pressure superimposition of the vane pump at the suction or inlet
side of this "auxiliary" pump can be effected in that all slot bottoms of
the rotor are in flow communication with one another by way of at least
one annular channel, especially by way of an annular groove and in that
only the slot bottoms of the rotor disposed in the suction area or areas
are in communication directly with the high pressure side of the
installation and in that the connecting places of the annular channel with
the slot bottoms have as large an axial distance as possible from the
connecting place of the flooding channels with the slot bottoms. The large
axial distance of the annular channel effecting the flow by-pass on the
one hand, and of the pressure-superimposing inlet line, on the other,
brings about that the feed volume of the "auxiliary" pump displaced in the
pressure area is again absorbed in the suction or inlet area thereof to as
large a proportion thereof as possible before the possibility exists
therefor to flow off into the pressure connection of the main pump. An
outward movement of the vanes in the suction or inlet area of the vane
pump is reliably achieved thereby. In order to further increase this
effect, provision may be made that the slot depth and the contour of the
vane edge facing the slot bottom as well as the contour of the slot bottom
itself are so constructed that the remaining open cross section between
vane edge and slot bottom is as small as possible in the furthest radially
retracted position of the vane. By reason of this narrow construction of
the discharge paths out of the feed or supply spaces of the auxiliary
pump, the possibility or the tendency to enlarge these paths, i.e. to
radially displace the vanes out of the slots, is still further increased.
The axial distance of the by-pass line and of the flooding line and
therewith the pressure effect on the vanes is particularly large when the
connecting places of the annular channel and of the flooding channels with
the slot bottoms are arranged at the two axially mutually opposite end
faces of the rotor.
In a constructively particularly simple manner, the annular channel may be
constructed as an annular groove opening in the direction toward one of
the two axially perpendicular gaps between the rotor end face and the
corresponding base plate (discharge side) and axially machined into the
rotor or one of the base plates, and the connecting places of the flooding
channels with the slot bottoms may be constructed as an aperture or recess
in the shape of a circular arc axially machined into the other base plate
(flooding side) and extending circumferentially over the suction or inlet
area or areas, whereby exclusively the aperture(s) or recess(es) may have
an unobstructed connection with the high pressure side of the
installation.
In order that the fluid forces acting axially on the rotor can cancel each
other far-reachingly, provision may be made appropriately that the
apertures or recesses machined into the base plate on the flooding side of
the rotor are constructed at least of approximately the same area as the
corresponding area of the annular groove as regards the open area facing
the axially perpendicular gap between the rotor and the plate.
In order to achieve also a completely satisfactory vane abutment at minimum
rotational speeds of the pump, on the one hand, and in order not to permit
the vane abutment to rise excessively high at maximum rotational speeds of
the pump, on the other, it is advisable to so select the radial cross
section of the annular line as regards its open cross-sectional area that
the auxiliary feed flow which establishes itself by reason of the feed
effect of the vanes sliding radially in the rotor slots, receives or
undergoes a noticeable back pressure at minimum rotational speeds of the
pump, yet that, on the other hand, the back pressure of this auxiliary
feed flow remains still sufficiently far below that limit at maximum
rotational speed of the pump, at which the radial abutment of the vanes at
the cam surface threatens to cause a wear and scuffing of the parts. The
cross section of the annular groove (by-pass or short-circuit line)
effects the back pressure of the by-passed feed flow of the "auxiliary
pump" responsible for the abutment of the vanes in the pressure area. This
cross section must therefore be designed corresponding to the indications
given hereinabove. For that purpose, experimental and empirical
possibilities, test data and the like are available to the person skilled
in the art, without having to engage in any inventive activities which can
be expected of him so that with the aforementioned indications he has
received teachings leading in a concrete case to the desired goal. Even
though the aimed-at starting improvement of the pump under cold condition
is completely achieved by means of the by-pass line of the "auxiliary
pump", it has been discovered that in particular with a pump operating at
normal operating temperature, instabilities may be introduced into the
by-pass flow by reason of the flow direction which is not unequivocally
prescribed to the by-pass flow, which might become noticeable under
certain circumstances as noise and a high-frequency fluttering of the
vanes. As a result thereof, the production of chatter marks at the cam
ring may be favored or a flush sealing abutment of the vane edge at the
cam ring may be impaired. In order to eliminate these disadvantages so
that the inventive concept can be realized without harm, provision may be
appropriately made that the slot bottoms of the vanes respectively
disposed in a discharge area are in flow-communication only with the slot
bottoms of the vanes disposed in an adjacent suction area adjoining in a
predetermined circumferential direction by way of an arcuately shaped
channel formed by a stationary part at least with respect to its end walls
determining the length dimension, and in that only the slot bottoms of the
rotor disposed in the suction or inlet area or areas are directly in
communication with the high pressure side of the installation and in that
the connecting places of the arcuately shaped channels with the slot
bottoms have as large as possible a spacing from the connecting places of
the flooding channels with the slot bottoms.
Accordingly, the by-pass line is not continuous at all places but is
interrupted at certain places so that only very defined pairings of
suction or inlet and discharge areas and the slot bottoms thereof are
interconnected. Unequivocal conditions are created thereby with respect to
the flow direction of the by-pass stream and an unstable tilting over or a
to-and-fro movement of the flow into the one or the other direction is no
longer possible. The arcuately shaped channels may be constituted by a
non-genuine annular groove in one of the base plates which is interrupted
at certain places by cross webs or by an annular groove in the rotor, into
which stationary cross webs immerse at certain circumferential places.
For favoring the by-pass flow in one direction and for decreasing flow
resistances, it is appropriate if the arcuately shaped channel or channels
and the end walls thereof are so arranged circumferentially that the
equalization flow from the discharge area to the suction or inlet area
takes place always in the operating direction of rotation. This means with
the single-flooding vane cell device with a rotor arranged eccentrically
within a circular cam surface that a circularly shaped groove extending
over nearly 360.degree. has to be interrupted at the place opposite the
eccentricity. In the double-flooding construction with a rotor arranged
concentrically in an approximately eliptically shaped cam ring, two
arcuately shaped channels extending over about 180.degree. must be
provided whose butting places are arranged in the plane of the major half
axis of the elipse.
Accordingly, it is an object of the present invention to provide a vane
type mechanism which avoids by simple means the aforementioned
shortcomings and drawbacks encountered in the prior art.
Another object of the present invention resides in a vane pump or motor
which can be operated at cold temperatures and which eliminates possible
shocks that are normally encountered when commencing the operation of the
pump or motor while cold.
A further object of the present invention resides in a vane pump or motor
which is simple in construction, utilizes relatively few parts, yet avoids
fluttering and ensures proper operation under all conditions.
Still a further object of the present invention resides in a vane pump or
motor which is characterized by smooth starting.
Another object of the present invention resides in a vane pump or motor,
particularly for use in servo-steering systems of motor vehicles, which
precludes spurious improper operations of the servo-steering system,
thereby imparting the confidence of the driver as regards the steering
system.
A further object of the present invention resides in a vane-type cell
mechanism of the aforementioned type in which proper abutment of the vanes
against the guide cam surface is assured under all operating conditions.
Another object of the present invention resides in a vane pump in which the
liquid pressures causing abutment of the vanes can build up also at
relatively small rotational speed with a relatively viscous flow medium.
Still another object of the present invention resides in a vane pump in
which the feed effect is assured relatively early accompanied with a
relatively soft starting thereof.
Still a further object of the present invention resides in a vane pump in
which the contamination of the hydraulic medium with air, water or dirt is
effectively precluded while the length of life and volumetric efficiency
of the pump as well as its operating characteristics are improved.
A still further object of the present invention resides in a vane pump in
which the danger of chatter marks at the cam surface are greatly
minimized, if not precluded.
These and further objects, features and advantages of the present invention
will become more apparent from the following description when taken in
connection with the accompanying drawing which shows, for purposes of
illustration only, two embodiments in accordance with the present
invention, and wherein:
FIG. 1 is a longitudinal cross-sectional view, taken along the axis of
rotation, through a vane pump or motor with a discharge of the working
medium out of the slot bottom of the rotor in accordance with the present
invention;
FIG. 2 is a transverse cross-sectional view through the pump or motor
according to FIG. 1, perpendicular to the axis of rotation and taken along
line II--II of FIG. 1;
FIGS. 3 and 4 are respectively plan views on one base plate each for the
axial limitation of the sickle-shaped working spaces of the pump or motor
into which are machined the feed and discharge channels for the operating
cells and the flooding and emptying channels and the annular channel for
the slot bottoms, each in axial view on the side thereof facing the rotor;
FIG. 5 is a cross-sectional view through the base plate according to FIG.
4, taken along line V--V; and
FIG. 6 is a plan view on a modified embodiment of a base plate in
accordance with the present invention and similar to FIG. 3.
Referring now to the drawing wherein like reference numerals are used
throughout the various views to designate like parts, the pump or motor
illustrated in FIGS. 1 and 2 includes a pump housing 1 in which is
journalled the drive shaft 2 and in which are accommodated the essential
pump parts. These pump parts consist of the rotor 3 non-rotatably mounted
on the shaft 2 together with the vanes 4 as well as the two base plates 5
and 6 (FIGS. 4 and 3) and the cam ring 7. The pressure plates may--as
parenthetically noted--be also components of the pump housing or of a
housing part in another embodiment of the present invention. The last
three-mentioned parts are retained by retaining pins 8 in a definite
mutual circumferential and radial position and are secured against radial
movements and against rotation. Axially the assembly opening of the pump
housing is closed off sealingly by the closure lid 10 secured by means of
a spring ring 9, utilizing a sealing ring 11 to achieve the desired
sealing effect. The main parts 3 to 6 of the pump receive an axial basic
compression independent of the pressure by a compression spring 12 mounted
between the cover 10 and the upper base plate 5. The upper base plate 5 is
additionally sealingly accommodated in the pump housing by the use of a
sealing ring 13 and separates the pressure side of the pump (space 14)
from the inlet or suction side (annular space 15). Both spaces 14 and 15
are adapted to be connected with a hydraulic system by way of connecting
ports 16 and 17.
A force corresponding to the level of the feed pressure of the pump
prevailing in the pressure space 14--high pressure side of the vane cell
device-- is exerted onto the upper base plate 5 by the feed pressure of
the pump prevailing in the pressure space 5 which sealingly compresses the
main parts 3 to 6 of the pump axially against the pressure forces
prevailing on the inside of the pump.
Axially extending radially disposed slots 18 with parallel walls are
machined into the rotor 3, into which are inserted plane-parallel
rectangular metal plates, the so-called vanes 4, which are able to slide
therein with a slight predetermined play or clearance. The vanes 4 are
exactly as long in the axial direction as the rotor 3 and the cam ring 7.
The inner contour 19 of the cam ring 7 is constructed oval (FIG. 2)
according to a predetermined endless curved configuration so that two
sickle-shaped working spaces 20 result between the rotor 3 and the curved
surface 19, through which pass rapidly in the circumferential direction
the vanes 4 subdividing these working spaces into cells during the
rotation of the rotor. The cam surface 19 is inclined radially outwardly
with respect to the circumferential direction within the areas of the line
21 during the rotation of the rotor in the direction of arrow 22 (FIG. 1)
and the feed cells formed between the vanes 4 become larger within this
area (suction or inlet area). The suction or inlet areas of the
sickle-shaped working spaces 20 receive a direct connection with the
ring-shaped feed space 15 by corresponding apertures or recesses 23 and 24
(FIGS. 3 and 4) at the lower base plate 6 (FIG. 3) and at the upper base
plate 5 (FIG. 4). These apertures 23 and 24 represent the internal
connecting channels of the suction or inlet side of the working spaces
with the annular space 15. Within the angular area of the line 25 (FIG. 2)
the cam surface 19 is inclined radially inwardly with respect to the
circumferential direction so that during the rotation of the rotor, the
cells become smaller within this area. The flow medium contained therein
is displaced axially on both sides whereby on the top rotor side as viewed
in FIG. 1 it is able to reach the pressure space 14 by way of the
through-apertures 26 in the plate 5 and on the lower side of the rotor, by
way of the apertures 27 in plate 6 constructed as recesses, by way of the
return bores 28 in the cam ring 7 and also by way of the apertures 26.
The vanes 4 which during the rotation of the rotor follow radially the
inner contour 19 of the cam ring 7, move radially outwardly within the
rotor slots during the passage through the suction or inlet area 21 and
the corresponding slot bottoms 29 which become larger at that time,
thereby fill up by way of the circularly shaped arcuate apertures 30
(FIGS. 1, 4 and 5) which extend over the angular space of the suction or
inlet area, are arranged along the radius of the slot bottoms and are
unobstructedly in communication with the pressure space 14, whereby the
apertures 30 represent the flooding channels for the slot bottoms passing
through the suction or inlet area. These flooding channels 30 are provided
only in one and more particularly in the upper base plate 5. The rotor
side facing the upper gap between the rotor and the base plate 5 is
therefore the flooding side, from which--if necessary--the slot bottoms of
the rotor are flooded from the outside. As a result of this unobstructed
admission of the working medium into the slot bottoms within the suction
or inlet area, a fluid pressure corresponding to the high pressure level
in the space 14 is exerted on the vanes 4 and additionally a rapid
flooding of these spaces is made possible which increase in volume, i.e.,
become larger.
During the passage of the rotor vanes 4 through a discharge area of the
pump, these vanes are forcibly displaced radially inwardly by the
configuration of the cam surface 19 and liquid is thereby displaced out of
the volumes of the slot bottoms which now become smaller. This displaced
working medium may in the illustrated pump escape axially out of the slot
bottoms exclusively on one side and more particularly into the annular
groove 31 (FIGS. 1 and 2) provided in the lower base plate 6 along the
diameter of the slot bottoms. Since the annular groove 31 is provided only
in the lower base plate 6, the slot bottoms of the discharge area can
discharge axially only toward this side of the rotor (emptying or
discharge side of the rotor). This annular groove 31 represents a part of
the discharge or emptying line for the slot bottoms which become smaller
when they pass through the discharge area. The slot bottoms in this area,
more particularly, are thus in communication with the pressure space 14 by
way of the slot bottoms disposed in the suction area and by way of the
flooding apertures 30. Working oil displaced by the vanes out of the slot
bottoms within the discharge area must therefore escape by way of a
by-pass through the slot bottoms disposed in the suction area. Since
however the slot bottoms disposed in the suction or inlet area become
larger at that moment, they are in a position to absorb the oil displaced
elsewhere. Consequently, a line by-pass between the slot bottoms which
become larger and those which become smaller is created by the annular
groove 31. Oil constantly flows through the annular groove 31 out of the
discharge area into the suction or inlet area. In contrast thereto, oil is
constantly supplied in the reverse direction in the slot bottoms of the
rotor. A system closed in itself is created by the by-pass line, on which
is superimposed externally exclusively the feed pressure of the pump and
to which eventual leakage quantities are supplied. By the corresponding
dimensioning of the flow cross section of the by-pass line 31 (visible in
FIG. 1), a certain damming or throttling effect producing a back-pressure
can be exe | | |
