Coupling gear

A coupling gear for transmitting rotation of a first shaft onto a second shaft has a first coupling wheel fixedly connected to the first shaft and a second coupling wheel fixedly connected to the second shaft. A third coupling wheel is driven by the first coupling wheel and a fourth coupling wheel is driven by the third coupling wheel and drives the second coupling wheel. A first coupler couples the rotational axle of the first coupling wheel and the rotational axle of the third coupling wheel. A second coupler couples the rotational axle of the third coupling wheel and the rotational axle of the fourth coupling wheel. A third coupler couples the rotational axle of the fourth coupling wheel and the rotational axle of the second coupling wheel. A control device for adjusting with a control movement the rotational phase of the first and second shafts has a control element for adjusting the angle between the first, second, and third couplers. The control device also has a friction member movable into frictional engagement with at least one of the coupling wheels to thereby aid the control movement initiated by the control device.

BACKGROUND OF THE INVENTION 
The present invention relates to a coupling gear for transmitting the 
rotation of a shaft onto another shaft, wherein a first coupling wheel is 
fixedly connected to one shaft and a second coupling wheel is fixedly 
connected to the other shaft. A third coupling wheel, driven by the first 
coupling wheel, and a fourth coupling wheel, driven by the third coupling 
wheel and driving the second coupling wheel, are provided. The rotational 
axes of the first and third coupling wheels, of the third and fourth 
coupling wheels, and of the fourth and second coupling wheels are 
connected with one another via couplers and the phase of rotation of one 
shaft relative to the other shaft can be adjusted with a control device 
which comprises a control element for adjusting the angle between the 
couplers. 
Such coupling gears are to be used for various applications and are, for 
example, known from German Patent Application P 42 44 550.7-13. One 
application for such coupling gears are devices for variably controlling 
the valves of combustion engines, especially for throttle-free load 
control of spark ignition engines via the inlet lift function of one or 
more inlet valves per cylinder, whereby the inlet lift function by two cam 
shafts the phase position of which can be adjusted. One requirement, which 
can only be dissatisfactorily fulfilled with conventional coupling gears 
in the designated application, is that the phase of the cam shafts must be 
adjusted by a great value within a short period of time. 
It is therefore an object of the present invention to provide a coupling 
gear of the aforementioned kind with which great phase changes within a 
short period of time can be effected. 
SUMMARY OF THE INVENTION 
The inventive coupling gear for transmitting rotation of a first shaft onto 
a second shaft according to the present invention is primarily 
characterized by: 
A first and a second shaft; 
A first coupling wheel fixedly connected to the first shaft; 
A second coupling wheel fixedly connected to the second shaft; 
A third coupling wheel with a rotational axle driven by the first coupling 
wheel; 
A fourth coupling wheel with a rotational axle driven by the third coupling 
wheel and driving the second coupling wheel; 
A first coupler for coupling the rotational axle of the first coupling 
wheel and the rotational axle of the third coupling wheel; 
A second coupler for coupling the rotational axle of the third coupling 
wheel and the rotational axle of the fourth coupling wheel; 
A third coupler for coupling the rotational axle of the fourth coupling 
wheel and the rotational axle of the second coupling wheel; 
A control device for adjusting with a control movement a rotational phase 
of the first shaft relative to the second shaft, the control device 
comprising a control element for adjusting the angle between the first, 
second, and third couplers; 
The control device further comprising a friction member movable into 
frictional engagement with at least one of the coupling wheels to thereby 
aid the control movement initiated by the control device. 
Advantageously, the coupling wheels are gear wheels and the friction member 
is movable alternatingly into frictional engagement with one of two of the 
gear wheels that rotate in opposite directions. 
Preferably, the coupling gear further comprises a solenoid for moving the 
friction member into frictional engagement. 
Expediently, the coupling gear further comprises a control member and a 
helical gearing. The friction member is preferably an axially displaceable 
transmission gear wheel and the control motor is drivingly connected with 
a helical gearing to the transmission gear wheel. The transmission gear 
wheel has lateral surfaces with friction surfaces and the two gear wheels 
that rotate in opposite directions have lateral surfaces with friction 
surfaces. The frictional surfaces of the transmission gear wheel and the 
frictional surfaces of the two gear wheels provide the frictional 
engagement. 
Advantageously, the transmission gear wheel is movable into frictional 
engagement with one of the two gear wheels that rotate in opposite 
directions. 
Preferably, the control device further comprises a control gear wheel with 
an eccentric. The control element is supported at the eccentric. 
Advantageously, the rotational axis of the control gear wheel is positioned 
so as to coincide with the rotational axle of one of the first and second 
coupling wheels and the control element engages one of the rotational 
axles of the third and fourth coupling wheels. 
Preferably, the helical gearing comprises a drive pinion connected to the 
control motor and an outer toothing connected to the transmission gear 
wheel. The drive pinion meshes with the outer toothing of the transmission 
gear wheel. The control gear wheel is shaped as a segment of a circle and 
has an outer toothing. The transmission gear wheel comprises a further 
toothing meshing with the outer toothing of the control gear wheel. The 
gear ratio between the drive pinion and the outer toothing of the control 
gear wheel is such that a large rotational angle of the drive pinion 
results in a small rotational angle of the control gear wheel. 
Preferably, the coupling gear has a self-locking action with respect to 
accidental adjustment when the control device is not activated. 
Preferably, the self-locking action is realized with the eccentric acting 
on the control element. 
In a preferred embodiment of the present invention, the eccentric is 
comprised of a pin eccentrically connected to the control gear wheel and a 
bearing sleeve supported on the pin. The control element is connected to 
the bearing sleeve and the diameter of the bearing sleeve is greater than 
the distance between the axis of the bearing sleeve and the rotational 
axle of the control gear wheel. 
Preferably, in one end position of the eccentric the rotational phase 
assumes an extreme value. 
Expediently, the friction member is elastically biased into a neutral 
position. 
In a preferred embodiment of the present invention the friction member is 
mounted on one of the couplers. 
In yet another embodiment of the present invention the coupling gear 
further comprises a device for resetting the rotational phase to a preset 
value when an operating error occurs. 
In another embodiment of the present invention the control device comprises 
a drive unit with a drive gear wheel rotatable in opposite directions. 
Advantageously, the control device further comprises a control member with 
an outer toothing and the drive gear wheel meshes with the control member. 
The drive unit is positioned eccentrically to the rotational axis of the 
drive gear wheel and has a pivot axis about which the drive unit is 
pivotable. The friction member is preferably a friction wheel. The drive 
unit, when the drive gear wheel is being driven, is pivoted due to a 
reaction force resulting at the control member about the pivot axis such 
that the friction wheel is brought into frictional engagement with one of 
two of the coupling wheels rotating in opposite directions for aiding 
rotation of the drive gear wheel. 
Preferably, the pivot axis is arranged symmetrically to the rotational axes 
of the two coupling wheels rotating in opposite directions. 
Advantageously, the control member is a control gear wheel having a 
rotational axis positioned so as to coincide with the pivot axis. 
In a preferred embodiment of the present invention, the friction wheel has 
a friction surface and the coupling wheels have a friction surface for 
providing the frictional engagement. The friction surfaces of the friction 
wheel and of the coupling wheels have a plurality of wedge projections. 
Preferably, the drive gear wheel is positioned such that a rotational axis 
of the drive gear wheel and a rotational axis of the friction wheel 
coincide. The drive gear wheel is preferably fixedly connected to the 
friction wheel. The friction wheel has an outer circumferential surface 
that is a friction surface. 
Advantageously, the drive unit comprises an electric motor with a drive 
pinion. The friction wheel has an inner toothing and planetary gear wheels 
meshing with the inner toothing. The drive pinion drives the planetary 
gear wheels. 
In another embodiment, the drive unit comprises an electric motor 
comprising a worm gear for driving the drive gear wheel. 
With the inventively provided friction member it is achieved that only 
minimal requirements must be placed onto the control device for fast 
adjustment of the phase position. The required exterior force for the 
control device is thus reduced. The movement transmitted from the control 
device onto the control element is aided by engagement of the friction 
member with at least one moving part of the coupling gear by using in the 
manner of a servo device the kinetic energy contained within the moving 
part, triggered by the control device, for adjusting the control element. 
Coupling gear systems that can be used in connection with the present 
invention can have various designs; their gear wheels can be in direct 
engagement; between the gear wheels pulling means such as belts, cardan 
drives etc. can be used. 
The engagement of the friction member with advantageously at least one of 
the gear wheels can be embodied in various manners. For example, the 
friction member can be pressed onto the corresponding friction surface of 
the gear wheel in the axial or radial direction. The control device can be 
actuated directly manually, pneumatically, hydraulically or 
electromotorically. 
The inventive coupling gear is suitable for various applications. It can be 
used advantageously where, despite a limited energy, respectively, power 
supply of the control device, a secure and fast adjustment of the relative 
phase position of two shafts operating at the same rpm is to be performed.

DESCRIPTION OF PREFERRED EMBODIMENTS 
The present invention will now be described in detail with the aid of 
several specific embodiments utilizing FIGS. 1 through 8. 
A first gear wheel 2 is fixedly connected to a first cam shaft S1 that is 
stationarily supported, respectively, supported at a motor block with its 
axle P1. A second gear wheel 4 is fixedly connected to a further, cam 
shaft S2 of a motor with its axle P2. The two gear wheels 2 and 4, as can 
be seen in FIG. 2, are axially staggered relative to one another so that 
their peripheries overlap. A third gear wheel 6 meshes with the first gear 
wheel 2 which, in turn, meshes with a fourth gear wheel 8 which then also 
meshes with the second gear wheel 4. The gear wheels 6 and 8 are supported 
on couplers, whereby a first coupler 10 is supported at P1 and the third 
gear wheel 6 as well as the second coupler 12 are supported at P3. The 
second coupler is connected jointedly at P4 with a third coupler 14 which 
is supported at P2. At P4 the fourth gear wheel 8 is supported. The number 
of teeth of the gear wheels 6 and 8 is preferably different. However, the 
first gear wheel 2 and the second gear wheel 4, when both have the same 
number of teeth, respectively, the same diameter, rotate at the same rpm 
in opposite rotational directions whereby the phase position between the 
rotation of the gear wheels 2 and 4, in a manner known per se, is 
adjustable by changing the angular position of the couplers 10, 12, 14. 
For changing the angular position of the couplers a control element in the 
form of a connecting coupler 16 is provided. The connecting coupler 16 is 
supported at P3 and terminates in a bearing sleeve 18 that is supported on 
a pin 20. The pin 20 is positioned eccentrically on the control gear wheel 
22 which is supported at P2. The axis of the bearing 18, 20, which is 
positioned eccentrically to P2, is indicated with reference numeral P5. 
An outer toothing of the segment-shaped control gear wheel 22 meshes with a 
pinion 24 which is a unitary part of the transmission gear wheel 26. The 
pinion 24 is rotatable about a stationary axle P6 and is axially 
displaceable. An outer toothing of the transmission gear wheel 26 meshes 
with a drive pinion 28 of an electric motor 30. The toothing between the 
drive pinion 28 and the transmission gear wheel 26 is in the form of a 
helical gearing so that upon torque transmission from the drive pinion 28 
onto the transmission gear wheel 26, depending on the drive direction, an 
axial displacement of the transmission gear wheel 26 in one or the other 
direction takes place. 
As indicated in FIG. 2, the transmission gear wheel 26 is arranged between 
the gear wheels 2 and 4. The transmission gear wheel 26 is provided at its 
end faces with friction surfaces 32 which overlap with friction surfaces 
34, 36 respectively provided at the gear wheel 2 and 4. The friction 
surfaces such as annular friction surfaces can, for example, be embodied 
such that each of the aforementioned end faces of the gear wheels is 
provided with an annular projection and the friction surfaces are formed 
by the end faces of the projections. 
For the following description of the function of the device, it is 
presupposed that the first gear wheel 2 according to FIG. 1 rotates in 
clockwise direction so that the second gear wheel 4 is driven via the 
third gear wheel 6 and the fourth gear wheel 8 with the same rotational 
speed but in the opposite direction. With the pin 20 having a 
correspondingly great diameter in relation to its eccentricity, the 
engagement between the connecting coupler 16, respectively, the bearing 
sleeve 18 with the pin 20 provides for a self-locking action of the 
coupling gear so that the coupling gear, due to the torque transmission 
from the first gear wheel 2 onto the second gear wheel 4 (or vice versa), 
cannot be automatically (accidentally) adjusted. 
When the drive pinion 28 for adjusting the coupling gear is driven in the 
clockwise direction, so that the transmission gear wheel 26 is rotated 
counter clockwise to thereby rotate the control gear wheel 22 in clockwise 
direction, the pin 20 together with the connecting coupler 16 are moved to 
the left and the coupling gear, respectively, the phase between the 
rotation of the two gear wheels 2 and 4 is adjusted correspondingly. Upon 
torque transmission from the drive pinion 28 onto the transmission gear 
wheel 26, the latter is forced, due to the helical gearing, in the 
direction toward the first toothed wheel 2 so that the frictional 
engagement between the friction surfaces 32 and 34 provides for an 
additional drive of the transmission gear wheel 26 in counterclockwise 
direction, i.e. the adjustment (control movement) is facilitated. As soon 
as the torque from the drive pinion 28 is relieved, no further pressing of 
the friction surfaces 32 and 34 takes place because due to the 
self-locking action of the coupling gear no torque is transmitted from the 
transmission gear wheel 26 onto the drive pinion 28. When the drive pinion 
28 is rotated in the opposite direction, the transmission gear wheel 26 is 
forced with its corresponding friction surface against the friction 
surface 36 of the second gear wheel 4 so that the adjustment of the 
inventive coupling gear is again facilitated. 
It is understood that the gear ratio between the drive pinion 28 and the 
control gear wheel 22 is advantageously selected such that a great change 
of angle at the drive pinion 28 results in a small change of angle at the 
control gear wheel 22. The electric motor 30 is advantageously designed 
such that it starts up with relatively great torque, i.e., upon actuation 
it reacts immediately. The further torque requirement must no longer be 
that great due to the servo action provided. 
The correlation between position of the eccentric drive 18, 20 and phase 
position of the gear wheels 2 and 4, for example, in the application for a 
cam drive, is advantageously such that at least one of the end positions 
corresponds to an extreme value, i.e., the minimum, respectively, maximum 
phase position. When the cam drive provided with the coupling gear serves, 
for example, for load control of an internal combustion engine without 
throttle, the maximum charge filling and thus also the maximum output can 
be safely limited in this manner. 
It is understood that a plurality of modifications and/or additional 
features of the present device are possible. For example, the transmission 
gear wheel 26 can be biased with its pinion 24 in an elastic manner in a 
neutral (central) position so that it is ensured that without torque 
provided by the drive pinion 28 no frictional engagement between any of 
the friction surfaces is possible. Furthermore, instead of a helical 
gearing between the drive pinion 28 and the outer toothing of the 
transmission gear wheel 26 a spur toothed gearing can be used when, for 
example, the transmission gear wheel 26 is axially moved in one or the 
other direction by a double-action hydraulic cylinder or solenoid in 
conjunction with an electric motor 30 as a drive unit, which will be 
described in the following. The friction surfaces can also be in the form 
of radial surfaces, the transmission gear wheel 26 then must be moved 
radially relative to the friction surfaces. 
The connecting coupler 16 for adjusting the coupling gear can also be 
directly linearly driven and connected to a friction member which upon 
displacement of the connecting coupler is forced into abutment of an end 
face of, for example, the second gear wheel 4 provided at a suitable 
location. 
It is understood that the inventive coupling gear can also be embodied such 
that further wheels are meshing with the gear wheels which then provide 
for the frictional engagement. In a further embodiment it is also possible 
to design the self-locking action within the coupling gear such that the 
coupling gear, because of the torque transmission from the first gear 
wheel onto the gear wheel 4 driven by it, has the tendency to self-adjust 
in one direction so that this direction of adjustment must be released by 
a control means. A servo action by frictional engagement is thus necessary 
only in the other adjustment direction. 
In the disclosed embodiment the control device, for the connecting coupler 
16, comprised of the eccentric drive 18, 20, the control gear wheel 22, 
the transmission gear wheel 26, and the electric motor 30, is supported at 
a stationary bearing location, for example, directly at the internal 
combustion engine. When such a design variation is impossible due to 
spatial limitations, the control device can also be mounted alternatively 
at one of the couplers, for example, the coupler 12 whereby the 
transmission gear wheel can then be supported at P3 or P4. 
In another variation of the inventive design, the component to which the 
pin 20 is mounted is not embodied as a control gear wheel but as a lever 
which is supported at P2 and which is rotated by a drive unit, for 
example, a worm gear driven electromotorically. 
The embodiment of the coupling gear according to FIG. 3 differs from the 
one represented in FIG. 2 in that for the axial displacement of the 
transmission gear wheel 26 in order to realize frictional engagement with 
the gear wheels 2 or 4, an armature 39 cooperates with the shaft 38 of the 
transmission gear wheel. The armature 39 is moved by two solenoids A, B in 
one or the other direction to thereby entrain the transmission gear wheel 
in the axial direction. The adjustment of the coupling gear in this 
embodiment is performed exclusively by the frictional engagement of the 
transmission gear wheel 26 meshing with the control gear wheel 22. 
The disclosed embodiment can be provided in a simple manner with a safety 
function by supplying a spring in addition to the magnetic drive. The 
spring engages the armature 39 and is neutralized by a further solenoid 
during normal operation. Upon detection of an error, for example, 
breakdown of the energy supply, it pulls the armature 39 in a direction in 
which the transmission gear wheel 26 engages one of the gear wheels 2 or 4 
such that the coupling gear is displaced, for example, in the direction of 
reduced power output of an internal combustion engine. 
In the embodiment of the coupling gear according to FIGS. 4 and 5, a drive 
gear wheel 40 meshes with the toothing provided at the exterior of the 
segment-shaped control gear wheel 22. This drive gear wheel 40 comprises a 
friction wheel 44 being a unitary part thereof. The friction wheel 44 has 
an inner toothing 46, an exterior friction surface 48, and a rotational 
axis P7. The inner toothing 46 of the friction wheel 44 meshes with planet 
gear wheels 49 which mesh, in turn, with the toothing of the pinion 50 of 
electric motor 51 with which the drive gear wheel 40 is driven in both 
directions. 
The components electric motor 51 with pinion 50, friction wheel 44, and 
planetary gear wheels 49 form a pre-mounted structural group that is 
supported and pivotable as a whole on the axle P8 which is fixedly 
connected to the motor. 
The friction surface 48 of the friction wheel 44 in the rest position of 
the disclosed device is almost in engagement with, respectively, abutting 
the friction surfaces 52, 54 which are embodied at the circumferential 
surfaces of projections of the gear wheels 2 and 4 serving as coupling 
wheels. 
The function of the disclosed device is as follows: 
When the coupling wheels 2, 4, 6 and 8 are rotated in the direction of the 
arrows shown in the drawings, i.e., the coupling wheel 2 is rotated 
counter-clockwise and the coupling wheel 4 is rotated clockwise and when 
the drive gear wheel 40 is driven via the drive pinion 50 and the 
planetary gear wheels 49 and the friction wheel 44 in the clockwise 
direction, the control gear wheel 22 is rotated in the counter-clockwise 
direction. The reaction force between drive gear wheel 40 and control gear 
wheel 22 causes the entire structural group 44, 49, 51 and 50 to be 
pivoted to the right about the axle P8 so that the friction surface 48 of 
the friction wheel 44 comes increasingly into contact with the friction 
surface 52 of the coupling gear wheel 2 so that the rotation of the 
coupling gear wheel 2 aids in driving the friction wheel 44 and thus aids 
in adjusting the control gear wheel 22. As soon as the rotational drive of 
the pinion 40 of motor 51 ceases, the frictional engagement is released 
and the control member 22 remains in its position as a consequence of the 
self-locking action between the pin 20 and the bearing sleeve 18. Upon 
displacement in the opposite direction, the aforementioned components act 
in the other direction. 
It is understood that numerous variations of the disclosed arrangement are 
possible. For example, the drive gear wheel could be directly driven by 
the electric motor so that the planetary gear wheels, which are 
advantageous with respect to the transmission action, are obsolete. The 
friction wheel can also be supported separate from the drive gear wheel. 
Advantageously, the control gear wheel 22 can be positioned such that its 
axis coincides with the axle P8. The tooth engagement between control gear 
wheel 22 and pinion 40 is thus not changed in any manner when the 
structural group consisting of motor, planetary gear wheels, and friction 
wheel are pivoted about the axle P8. Since the pivot movement is however 
very small, a reliable tooth engagement is ensured also in this 
construction. 
The embodiment represented in FIGS. 6 and 7 differs from the embodiment of 
FIGS. 4 and 5 only with respect to the drive of the drive gear wheel 40. 
With the exception of the drive gear wheel 40 only those reference 
numerals are shown which vary with respect to the embodiment of FIGS. 4 
and 5. The outer toothing of the drive gear wheel 40 meshes with a worm 
gear 56 that is mounted to the drive shaft 58 of the electric motor 60. 
The friction wheel 62 which is fixedly connected to the drive gear wheel 
40 in this embodiment does not have an inner toothing but is only provided 
with the friction surface 48 at its outer circumference. The drive gear 
wheel 40 has two toothings that are axially staggered. The toothing 64 
meshes with the worm gear 56 and the other toothing 66 meshes with the 
control gear wheel 22 according to FIG. 4. The transmission of power 
between electric motor and drive gear wheel, which in the embodiment 
according to FIG. 4 takes place via the planetary gear wheels, is realized 
in this embodiment with the worm gear 56 of FIG. 6. 
In FIG. 6 a common base plate 70 is indicated with dashed lines to which 
the drive gear wheel 40, the friction wheel 62, fixedly connected thereto 
and rotatable about their common rotational axis P7, as well as optionally 
the electric motor 60 with worm gear 56 are mounted such that the entire 
structural group can be pivoted about the pivot axle P8. The electric 
motor 60 could also be fastened to another component of the coupling gear 
so that it does not follow the small movement of the base plate. 
FIG. 8 shows another advantageous embodiment of the friction surfaces at 
the circumferential edge of the friction wheel 44, 62 and of the coupling 
gear wheels 2, 4 whereby the friction surfaces are shown in the 
circumferential direction, i.e., perpendicular to the rotational axis of 
the corresponding wheels. Due to the embodiment of the friction surfaces 
as surfaces with a plurality of wedge projections (greatly enlarged 
representation) a softer and at the same time considerably improved 
frictional engagement is provided. 
The present invention is, of course, in no way restricted to the specific 
disclosure of the specification and drawings, but also encompasses any 
modifications within the scope of the appended claims.