U.S. patent application number 09/987152 was filed with the patent office on 2002-05-16 for shaft having outer teeth for transferring torque between hydraulic machines arranged coaxially behind one another.
Invention is credited to Christiansen, Tage, Johansen, Bettina L.C., Paulsen, Helle.
Application Number | 20020057978 09/987152 |
Document ID | / |
Family ID | 7663162 |
Filed Date | 2002-05-16 |
United States Patent
Application |
20020057978 |
Kind Code |
A1 |
Johansen, Bettina L.C. ; et
al. |
May 16, 2002 |
Shaft having outer teeth for transferring torque between hydraulic
machines arranged coaxially behind one another
Abstract
In a shaft (19) having outer teeth (18) for transferring torque
between hydraulic machines (1, 2) arranged coaxially behind one
another, especially hydraulic pumps of a steering device, in which
an inner wheel (7; 8) provided with teeth (9; 10; 15; 16) on the
inside and outside moves around the inside of a toothed ring (3; 4)
having inner teeth (5; 6) and engages with the teeth (5; 6) of the
toothed ring (3; 4), and the teeth (18) of the shaft (19) engage
without relative rotation in the inner teeth (15; 16) of the inner
wheels (7, 8), in order to simplify manufacture and assembly of the
shaft and to avoid noise, the thickness of the teeth (18) of the
shaft (19) or of the inner teeth (15; 16) of the inner wheels (7,
8), measured on the reference circle, is greater than the width,
measured on the reference circle, of the gaps into which those
teeth (18; 7; 8) engage, with the result that the flanks of the
teeth (18) of the shaft (19) come into contact securely with the
flanks of the inner teeth (15; 16) of the inner wheels (7, 8), and
the shaft (19) has slots (20) in both end portions between at least
some of its teeth (18) and is hollow at least in the end portions
that are provided with the slots (20).
Inventors: |
Johansen, Bettina L.C.;
(Nordborg, DK) ; Paulsen, Helle; (Nordborg,
DK) ; Christiansen, Tage; (Nordborg, DK) |
Correspondence
Address: |
Matthew L. Schneider, Esquire
BURNS, DOANE, SWECKER & MATHIS, L.L.P.
P.O. Box 1404
Alexandria
VA
22313-1404
US
|
Family ID: |
7663162 |
Appl. No.: |
09/987152 |
Filed: |
November 13, 2001 |
Current U.S.
Class: |
418/171 ;
418/166 |
Current CPC
Class: |
F04C 2/102 20130101;
F04C 15/0073 20130101 |
Class at
Publication: |
418/171 ;
418/166 |
International
Class: |
F01C 001/10 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 14, 2000 |
DE |
100 56 252.3 |
Claims
1. Shaft (19) having outer teeth (18) for transferring torque
between hydraulic machines (1, 2) arranged coaxially behind one
another, especially hydraulic pumps of a steering device, in which
an inner wheel (7; 8) provided with teeth (9; 10; 18) on the inside
and outside moves around the inside of a toothed ring (3; 4) having
inner teeth (5; 6) and engages with the teeth (5; 6) of the toothed
ring (3; 4), and the teeth (18) of the shaft (19) engage without
relative rotation in the inner teeth (15; 16) of the inner wheels
(7; 8), characterized in that the thickness of the teeth (18) of
the shaft (19) or of the inner teeth (15; 16) of the inner wheels
(7; 8), measured on the reference circle, is greater than the
width, measured on the reference circle, of the gaps into which
those teeth (18; 7; 8) engage, with the result that the flanks of
the teeth (18) of the shaft (19) come into contact securely with
the flanks of the inner teeth (15; 16) of the inner wheels (7; 8);
and the shaft (19) has slots (20) in both end portions between at
least some of its teeth (18) and is hollow at least in the end
portions that are provided with the slots (20).
2. Shaft according to claim 1, characterized in that the thickness
of the teeth (18) of the shaft (19) is slightly greater than that
of the inner teeth (15, 16) of the inner wheels (7, 8).
3. Shaft according to claim 1 or claim 2, characterized in that the
shaft (19) is provided with an annular groove (21) near each of its
ends in the region of its slots (20).
4. Shaft according to any one of claims 1 to 3, characterized in
that the inner teeth (15; 16) of the inner wheels (7, 8) are formed
in adjacent end portions of the inner wheels (7, 8).
Description
[0001] The invention relates to a shaft having outer teeth for
transferring torque between hydraulic machines arranged coaxially
behind one another, especially hydraulic pumps of a steering
device, in which an inner wheel provided with teeth on the inside
and outside moves around the inside of a toothed ring having inner
teeth and engages with the teeth of the toothed ring, and the teeth
of the shaft engage without relative rotation in the inner teeth of
the inner wheels.
[0002] In order to increase the output of a hydraulic machine,
especially hydraulic pumps of a steering device that serve as
metering pumps, it is known from DE 196 07 064 C2 to operate two
relatively small hydraulic machines in parallel. For that purpose
there is used a shaft having outer teeth, which connects the two
hydraulic machines with one another by bringing the teeth of the
shaft into engagement with the inner teeth of the inner wheel. The
two hydraulic machines are driven in customary manner by an
inserted shaft (also called a Cardan shaft) having outer teeth
which also engage with the inner teeth of one of the two inner
wheels. If it is desired, for example in a metering pump of the
type mentioned, to increase further the total pump capacity or
displacement, for example displacement to 1250 cm.sup.3, it is
difficult to make or produce the inner wheels (even in the case of
two hydraulic machines connected in parallel, each having only one
half of the desired total output so as to be able, where possible,
to use relatively small hydraulic machines already present) and
also the shaft connecting the two hydraulic machines with
sufficient precision that the teeth of the inner wheels cooperate
with the teeth of the shaft without play, in order to avoid the
generation of noise. Conversely, on engagement of the teeth of the
inner wheels with the teeth of the shaft, a force fit might occur
owing to the low production tolerances that would not be met with
sufficient precision in the case of such large components, in which
case it would be extremely difficult to assemble the shaft with the
inner wheels.
[0003] The problem underlying the invention is to provide a shaft
of the type mentioned at the beginning that enables simple and
economical manufacture, that is easy to assemble and even so
provides play-free connection of the hydraulic machines.
[0004] The problem is solved according to the invention in that the
thickness of the teeth of the shaft or of the inner teeth of the
inner wheels, measured on the reference circle, is greater than the
width, measured on the reference circle, of the gaps into which
those teeth engage, with the result that the flanks of the teeth of
the shaft come into contact securely with the flanks of the inner
teeth of the inner wheels, and the shaft has slots in both end
portions between at least some of its teeth and is hollow at least
in the end portions provided with the slots.
[0005] In that solution, the teeth of the shaft come into contact
without play with the inner teeth of the inner wheels. The shaft
can be assembled easily, however, because at least at the ends of
the shaft the slots enable the teeth of the shaft to yield
resiliently in the hollow chamber of the shaft and the teeth of the
shaft and inner wheels that engage with one another come into
resilient contact with one another. The teeth of the inner wheels
and of the shaft do not need to be manufactured with low
tolerances. It is only necessary to ensure that the tooth
thickness, measured as an arc length on the reference circle, of
the teeth engaging in the gaps between the other teeth is slightly
greater than the width of the gaps between the other teeth.
[0006] Preferably the thickness of the teeth of the shaft is
slightly greater than that of the inner teeth of the inner
wheels.
[0007] The shaft can then be provided with an annular groove near
each of its ends in the region of its slots. Those annular grooves
increase the resilience of the regions of the ends of the shaft
provided with teeth.
[0008] Moreover, the inner teeth of the inner wheels can be formed
in adjacent end portions of the inner wheels. The inner teeth of
the inner wheels thus do not need to be constructed over the entire
axial length of the inner wheels.
[0009] The invention will be described hereinafter in greater
detail with reference to a preferred embodiment, in conjunction
with the drawings, in which:
[0010] FIG. 1 is a front view of a portion of two hydraulic
machines in the form of hydraulic pumps connected by a shaft
according to the invention;
[0011] FIG. 2 is an axial section of FIG. 1,
[0012] FIG. 3 is an end view of a shaft according to the
invention,
[0013] FIG. 4 is the section IV-IV of FIG. 3, and
[0014] FIG. 5 is the section V-V of FIG. 4.
[0015] FIGS. 1 and 2 represent a portion of two hydraulic machines
1 and 2 in the form of hydraulic pumps constructed as metering
pumps of a hydraulic steering unit of a motor vehicle. The
hydraulic machines 1 and 2 each comprise, respectively, a toothed
ring 3 and 4 having inner teeth 5 and 6 and an inner wheel 7 and 8
(displacing wheel) having outer teeth 9 and 10. By means of holes
12 that are in alignment with the gaps between the teeth 5 and 6,
an intermediate disk 11 connects the spaces delimited by the teeth
5 and 9 and by the teeth 6 and 10, in dependence on the relative
position of rotation of the toothed rings 3, 4 and inner wheels 7,
8. The hydraulic machines 1 and 2 are connected by means of screws
(not shown), which are passed through axial bores 13 in the toothed
rings 3 and 4, the intermediate disk 11 and a plate 14 that covers
the hydraulic motor 4 on one side.
[0016] The inner wheels 7 and 8 are provided on the inside, in
adjacent end portions, with teeth 15 and 16, with which there
engage outer teeth 18 of a shaft 19 that connects the hydraulic
machines 1 and 2 coaxially. The height of the teeth 15 of the inner
wheel 7 varies from tooth to tooth (see FIG. 1) as does the height
of the teeth 16 of the inner wheel 8 (FIG. 2).
[0017] The shaft 19 is hollow throughout its axial length. It is
also possible, however, for the shaft to be hollow only in its end
portions. The thickness of its teeth 18, measured as an arc length
on the reference circle, is slightly greater than the width of the
gaps, measured as an arc length on the reference circle, of the
inner teeth 15, 16 of the inner wheels 7 and 8, with the result
that the flanks of the teeth 18 of the shaft 19 come into contact
securely with the flanks of the inner teeth 15, 16 of the inner
wheels 7 and 8. The thickness of the teeth 18 of the shaft 19 can
thus be slightly greater than that of the inner teeth 15, 16 of the
inner wheels 7, 8. More precisely, the thickness of the teeth 18 of
the shaft 19 is slightly greater than the width of the gap between
the teeth 15, 16 of the inner wheels 7, 8, the thickness of the
teeth and the width of the gaps between teeth being measured as arc
lengths on the reference circle of involute toothing of the teeth.
Conversely, it is also possible for the thickness of the teeth 15,
16 to be slightly greater than the width of the gaps between the
teeth 18. Put more simply, the thickness of the teeth engaging in
the teeth gaps is greater than the nominal dimension of the width
of the teeth gaps.
[0018] The shaft 19 also has in both end portions, between at least
some of its teeth 18, axial slots 20 that are open towards the ends
of the shaft 19 and that pass through the wall of the shaft 19
radially, which slots are spaced apart from one another at
identical angles. Owing to the slots 20, it is possible for the
parts of the shaft 19 that lie between the slots, together with the
teeth 18 formed on those parts, to bend resiliently radially
inwards as a result of the contact pressure between those teeth 18
and the inner teeth 15, 16 between which the teeth 18 engage, so
avoiding a force fit despite the greater dimension. This
facilitates assembly of the shaft 19 with the inner wheels 7,
8.
[0019] The ability of the portions of the teeth 18 that engage with
the teeth 15, 16 to bend is still further increased by the fact
that the shaft 19 is provided with an annular groove 21 near each
of its ends in the region of its slots 20. Moreover, there is play
between the tip circle of the teeth 18 lying between the annular
grooves 21 and the axial centre of the shaft 19 and the root circle
of the teeth 15, 16 of the inner wheels 7 and 8. The diameter of
the tip circle of the axially outer teeth 18, on the other hand, is
only slightly greater than the diameter of the root circle of the
teeth 15, 16.
[0020] The intermediate disk 11 engages in an axially central
annular groove 22 of the shaft 19 by means of projections 23 that
project radially inward (FIG. 2), which projections are arranged to
pass through the gaps between the teeth 18 of the shaft 19 during
assembly and then, after rotation of the intermediate disk 11 by
half the spacing of the teeth 18, to come to rest behind the teeth
18. Thereafter the screws are introduced through the bores 13.
[0021] The teeth 18 of the shaft 19 engage only in an end portion
of the axial length of the teeth 15, which end portion lies closest
to the facing ends of the inner wheels 7 and 8. A toothed ring gear
provided at the end of an inserted shaft (also called a Cardan
shaft) is then introduced, from the left-hand side in FIG. 2
through the hollow chamber of the inner wheel 7, into the portion
of the teeth 15 that is left free by the teeth 18. The hydraulic
machines 1 and 2, insofar as they are in the form of hydraulic
pumps, are then driven by means of that inserted shaft and the
shaft 19. It would also be possible, however, to operate the
hydraulic machines 1 and 2 as hydraulic motors by feeding in a
hydraulic fluid, which hydraulic motors would then drive a work
apparatus by means of the inserted shaft.
[0022] To provide the inner wheels 7 and 8 with teeth 15, 16 only
in their adjacent end portions, which are relatively short in
comparison with the total length of the inner wheels 7 and 8, as
shown in FIG. 2, has the advantage that it is easier to manufacture
the teeth 15, 16. Alternatively, it would also be possible to
extend the teeth 15, 16 over the entire axial length of the inner
wheels 7 and 8.
* * * * *