Internal combustion engine with separable crankshafts

An internal combustion engine wherein a first group of cylinders rotates a first crankshaft and a second group of cylinders can rotate a second crankshaft which can be separably coupled to the first crankshaft by an accelerating friction clutch. The clutch permits slippage of a first clutch member which is driven by one of the crankshafts relative to a second clutch member which drives the other crankshaft while the other crankshaft undergoes gradual acceleration to the speed of the one crankshaft. Once the speed of the other crankshaft matches or closely approximates the speed of the one crankshaft, and the other crankshaft assumes a predetermined angular position relative to the one crankshaft, the first clutch member ceases to slip relative to the second clutch member. The accelerating clutch can be interposed between two camshafts one of which is driven by the one crankshaft and the other of which drives the other crankshaft during acceleration of the other crankshaft. The engine is then equipped with a positive-engagement second clutch which is installed between the two crankshafts and is engaged as soon as the other crankshaft rotates at the speed of the one crankshaft and assumes the desired angular position with respect to the one crankshaft.

BACKGROUND OF THE INVENTION 
The present invention relates to internal combustion engines in general, 
and more particularly to improvements in internal combustion engines of 
the type wherein several groups of cylinders can rotate discrete 
crankshafts. Still more particularly, the invention relates to 
improvements in internal combustion engines of the type having a first 
engine section or unit which comprises a first crankshaft adapted to be 
rotated by a first group of cylinders, at least one further section or 
unit whose crankshaft or crankshafts can be rotated by one or more 
additional groups of cylinders, and means for connecting the crankshafts 
to each other when the speed of the previously idle crankshaft or 
crankshafts is adequately increased to match or approximate the speed of 
the driven crankshaft. 
It is already known to deactivate a group of cylinders in a multi-cylinder 
internal combustion engine when the engine is to operate at partial load. 
This entails substantial savings in fuel and reduces the quantity of 
deleterious combustion products which are discharged into the surrounding 
atmosphere. Reference may be had to German Offenlegungsschrift No. 28 28 
298 which discloses a method of operating an internal combustion engine 
having several cylinders which are disposed in a common cylinder block. 
The engine has a composite crankshaft which includes several discrete 
crankshafts each associated with a given group of cylinders. When the 
engine is to be operated at partial load, e.g., immediately after 
starting, the cylinders of a first group of cylinders drive the 
corresponding discrete crankshaft while the remaining cylinders and the 
corresponding discrete crankshaft or crankshafts remain idle. If the 
engine is to be thereupon operated at full load, it is necessary to 
accelerate the remaining crankshaft or crankshafts to the speed of the 
crankshaft which is driven by the first group of cylinders, and to couple 
the crankshafts to each other only when the crankshafts assume 
predetermined angular positions. 
OBJECTS AND SUMMARY OF THE INVENTION 
An object of the invention is to provide an internal combustion engine of 
the type having several crankshafts with novel and improved means for 
connecting such crankshafts to or for disconnecting such crankshafts from 
each other. 
Another object of the invention is to provide novel and improved means for 
ensuring that the crankshafts can be coupled to each other at proper times 
as concerns their angular velocities and/or mutual angular positions. 
A further object of the invention is to provide novel and improved clutch 
means for use in an engine of the above outlined character. 
An additional object of the invention is to provide novel and improved 
means for actuating the clutch which can establish or terminate a torque 
transmitting connection between discrete crankshafts of an internal 
combustion engine. 
A further object of the invention is to provide the engine with means which 
allows for full engagement of the clutch only and alone when the angular 
velocities of the crankshafts to be coupled are in proper relationship to 
each other as well as when the angular positions of the crankshafts to be 
connected are in optimum relation to one another. 
Still another object of the invention is to provide a relatively simple, 
rugged, compact and readily accessible torque transmitting connection 
between discrete crankshafts of an internal combustion engine. 
A further object of the invention is to provide an apparatus which is 
capable of automatically effecting full torque transmitting engagement 
between discrete crankshafats of an internal combustion engine only when 
the speed and the angular position of the crankshaft which is to be 
coupled to an already driven crankshaft match predetermined values. 
Another object of the invention is to provide a compact and fuel-saving 
internal combustion engine which embodies the above outlined apparatus. 
The invention resides in the provision of an internal combustion engine 
which comprises a first engine section or unit having a first rotary 
crankshaft which can be rotated by a first group of clyinders, a second 
engine section or unit having a second rotary crankshaft which can be 
rotated by a second group of cylinders and, in accordance with an 
advantageous feature of the invention, is parallel to the first 
crankshaft, and an accelerating clutch (e.g., a dry friction clutch) which 
is actuatable to transmit torque from one of the crankshafts to the other 
of the crankshafts. The clutch includes a first clutch member which 
receives torque from the one crankshaft (the one crankshaft can be driven 
by the respective group of clyinders when the engine is operated at 
partial load), a second clutch member which serves to transmit torque to 
the other crankshaft and to receive torque from the first clutch member, 
and mechanical, hydraulic, electronic and/or otherwise constructed 
actuating means for gradually increasing the rate of torque transmission 
from the first to the second clutch member until the rotational speed of 
the second clutch member at least approximates (or actually matches) the 
rotational speed of the first clutch member. The parallel crankshafts are 
preferably installed in a common casing or housing. 
The actuating means is designed to increase the rate of torque transmission 
from the first to the second clutch member to a maximum value (at which 
the first clutch member does not slip relative to the second clutch 
member) in a predetermined angular position of the other crankshaft with 
reference to the one crankshaft. The clutch members can be coaxial with 
the one or the other crankshaft. If the first clutch member is rigid with 
the one crankshaft, the engine further comprises means for rotating the 
other crankshaft in response to rotation of the second clutch member. Such 
rotating means may comprise a first torque transmitting element 
(preferably a first gear) which is rigid with the second clutch member and 
a second torque transmitting element (preferably a second gear) which is 
driven by the first torque transmitting element and is rigid with the 
other crankshaft. The ratio of the gears is preferably one-to-one. 
If the second clutch member is rigid with the other crankshaft and is 
coaxial with the first clutch members the engine further comprises means 
for rotating the first clutch member in response to rotation of the one 
crankshaft. Such rotating means may include a first torque transmitting 
element (preferably a first gear) which is rigid with the one crankshaft 
and a second torque transmitting element (preferably a second gear) which 
is driven by the first torque transmitting element and is rigid with the 
first clutch member. The ratio of such gears is again one-to-one. 
The aforementioned actuating means is preferably designed to increase the 
rate of torque transmission from the first to the second clutch member to 
a maximum value (at which the first clutch member ceases to turn relative 
to the second clutch member) in a predetermined angular position of the 
other crankshaft relative to the one crankshaft. Torsional shock absorber 
means (e.g., of the type known from the art of clutches which are used 
between the output element of the engine and the input element of the 
transmission in an automotive vehicle) can be interposed between the two 
clutch members to take up the initial shock when the first clutch member 
begins to transmit torque to the second clutch member. 
The novel features which are considered as characteristic of the invention 
are set forth in particular in the appended claims. The improved engine 
itself, however, both as to its construction and its mode of operation, 
together with additional features and advantages thereof, will be best 
understood upon perusal of the following detailed description of certain 
specific embodiments with reference to the accompanying drawing.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring first to FIG. 1, there is shown a portion of an internal 
combustion engine with two discrete units or sections. The first unit or 
section comprises a first crankshaft 1 which rotates when the engine is 
operated at partial load, for example, immediately after starting, as well 
as when the engine is operated at full load. Thus, the crankshaft 1 
rotates whenever the engine is running and has an end portion 3 which is 
remote from the end portion (3a) that transmits torque to one or more 
driven components of the vehicle in which the engine is installed. The end 
portion 3 of the crankshaft 1 extends from the housing or casing 30 of the 
engine and carries a first clutch member 4 which is rigidly secured 
thereto so that the clutch member 4 shares all angular movements of the 
crankshaft 1. The clutch member 4 constitutes a first component and a 
second clutch member 5 constitutes a second component of a clutch which 
serves to accelerate (when necessary) a second crankshaft 2 of the engine 
and to thereupon ensure that the second crankshaft rotates at the speed of 
the first crankshaft. The second clutch member 5 is preferably concentric 
to the first clutch member 4 and the first cankshaft 1. As shown in FIG. 
1, the second clutch member 5 is rotatable on antifriction bearings 13 and 
14 which surround a substantially cylindrical portion of the clutch member 
4. The clutch member 5 comprises a torque transmitting spur gear 15 which 
meshes with a torque transmitting spur gear 16 mounted on the right-hand 
end portion of the second crankshaft 2. The gear 15 may constitute a 
separable or integral part of the second clutch member 5. Analogously, the 
gear 16, which is in permanent mesh with the gear 15, can be separably or 
integrally connected with the second crankshaft 2. In the embodiment of 
FIG. 1, the second gear 16 is bolted at 31 to a collar 21 of the 
crankshaft 2. The ratio of the gears 15 and 16 is one-to-one. This ensures 
that, when the first crankshaft 1 drives the gear 15 through the fully 
engaged accelerating clutch including the clutch members 4 and 5, the 
speed of the second crankshaft 2 is identical with that of the crankshaft 
1. The axes of the crankshafts 1 and 2 are parallel to each other. 
The device (hereinafter called actuating device) which serves to engage or 
disengage the accelerating clutch including the clutch members 4 and 5 is 
denoted by the reference character 7. In normal operation, the clutch 
including the members 4 and 5 is engaged. When the clutch is to be 
disengaged, the actuating device 7 must furnish a force which overcomes 
the force of a spring 32 serving to normally engage the clutch member 5 
with the clutch member 4 so that the clutch member 5 is rotated at the 
exact speed of the crankshaft 1. During acceleration of the clutch member 
5, the clutch member 4 slips relative to the clutch member 5 to a greater 
or lesser extent, depending on the momentary speed ratio of the members 4 
and 5. The means for establishing a frictional torque transmitting 
engagement between the clutch members 4 and 5 includes one or more 
friction discs 34. The magnitude of friction between the clutch members 4 
and 5 depends upon the force which a piston 33 of the actuating device 7 
applies against the spring 32. In order to avoid or eliminate shocks 
during transmission of torque between the clutch members 4 and 5, the 
first clutch member 4 preferably carries a conventional torsional shock 
absorber means or damping device 24 having a disc-shaped member serving to 
carry the friction disc or discs 34. 
The actuating device 7 further comprises at least one valve 27 which 
regulates the flow of pressurized hydraulic fluid from a source 27a into a 
cylinder chamber 22 for the piston 33. The valve 27 can regulate the rate 
of admission of pressurized fluid into as well as the rate of evacuation 
of such fluid from the chamber 22 to thereby determine the axial position 
of the piston 33 which is reciprocable in the chamber 22. When the piston 
33 is ahifted in a direction to the left, as viewed in FIG. 1, it causes 
the central portion of the spring 32 to move in the same direction whereby 
the spring pivots about a seat 40 and its outer or marginal portion 42 
reduces the pressure upon the projections (only one shown) 41 of a 
pressure plate which bears against the friction disc or discs 34 and, as a 
result of such bias, regulates the extent of torque-transmitting 
engagement between the clutch members 4 and 5. The arrangement is such 
that, when the piston 33 is shifted in response to admission of 
pressurized hydraulic fluid into the cylinder chamber 22, the marginal 
portion 42 of the spring 32 moves in a direction to the right, as viewed 
in FIG. 1, whereby the extent of frictional engagement between the clutch 
members 4 and 5 is reduced. The spring 32 is preferably a dished spring 
which is pivotable at 40. The piston 33 transmits motion to the central 
portion of the spring 32 by way of an antifriction bearing 36 one race of 
which rotates with the spring 32 and the other race of which is connected 
to the left-hand end portion of the piston 33. The bearing 36 surrounds a 
cylindrical sleeve 35 which constitutes an extension of the end portion 3 
of the crankshaft 1. The sleeve 35 extends through a central opening of 
the spring 32. 
The means for shifting the valving element of the valve 27 comprises a 
control unit 12 which has an output for transmission of signals to the 
solenoid or solenoids of the valve 27 and several inputs including a first 
input connected to the output of a first monitoring device 8 and a second 
input connected to the output of a second monitoring device 9. The 
monitoring device 8 serves to track the angular position of the crankshaft 
2 and cooperates with an orbitable magnet 10 or an analogous portion of 
the gear 16 which is secured to and rotates the crankshaft 2. The 
monitoring device 8 is mounted in the casing 30 and may constitute a 
proximity detector which transmits a signal whenever the magnet 10 
advances past its left-hand end portion, as viewed in FIG. 1. The other 
monitoring device 9 serves to track the angular position of the crankshaft 
1 and cooperates with a magnet 11 or another signal generation initiating 
portion on a rotary part which shares the angular movements of the 
crankshaft 1. In the illustrated embodiment, the monitoring device 9 is 
adjacent to the circumference of the clutch member 4 and generates signals 
whenever the portion 11 advances therealong. Each of the monitoring 
devices 8, 9 can comprise a conventional inductive transducer. Signals 
which are transmitted by the monitoring devices 8 and 9 denote the angular 
positions of the respective crankshafts, and the frequencies at which such 
signals are generated denote the rotational speeds of the respective 
crankshafts. It goes without saying that the monitoring device 8 can be 
installed adjacent to the collar 21 or adjacent to a portion of the 
crankshaft 2. Analogously, the monitoring device 9 can be placed adjacent 
to a portion of the crankshaft 1, i.e., the device 9 need not be installed 
at the periphery of the clutch member 4 which is driven by the end portion 
3 of the crankshaft 1. 
The control unit 12 comprises means for evaluating the signals which are 
transmitted by the outputs of the monitoring devices 8 and 9. The 
evaluating means (e.g., a suitable circuit), the details of which forms no 
part of the present invention, ascertains the rotational speed of each of 
the two crankshafts 1 and 2 as well as the angular positions of the 
crankshafts at any stage of operation of the engine which embodies the 
structure shown in FIG. 1. As stated above, the rotational speed of each 
crankshaft can be readily ascertained by monitoring the frequency at which 
the corresponding monitoring devices 9 and 8 transmit signals to the 
respective inputs of the control unit 12. The angular position of the 
crankshaft 2 relative to the crankshaft 1 can be ascertained by monitoring 
the length of intervals between the generation of a signal by the 
monitoring device 9 and the generation of a signal by the monitoring 
device 8. 
When the rotational speed of the crankshaft 2 has been increased to such an 
extent that it equals or at least closely approximates the speed of the 
crankshaft 1, the output of the control unit 12 transmits a signal to the 
valve 27. Such signal is further supposed to indicate that the second 
crankshaft 2 has assumed a predetermined angular position with preference 
to the first crankshaft 1. The valve 27 then connects the chamber 22 with 
a sump for hydraulic fluid so that the spring 32 can push the piston 33 in 
a direction to the right, as viewed in FIG. 1, and the piston 33 expels 
the fluid into the sump by way of the valve 27. At such time, the spring 
32 pivots with reference to its seat 40 and its marginal portion 42 bears 
with a greater force against the projections 41 so that the frictional 
engagement between the clutch members 4 and 5 suffices to ensure that the 
rotational speed of the clutch member 5, and hence the rotational speed of 
the crankshaft 2, matches the rotational speed of the crankshaft 1. 
The operation of the structure which is shown in FIG. 1 is as follows: 
It is assumed that certain cylinders (e.g., two cylinders) of the engine 
drive the crankshaft 1 and that the clutch including the members 4 and 5 
is disengaged. In other words, the crankshaft 2 does not rotate. If the 
operator of the vehicle which embodies the engine including the 
crankshafts 1 and 2 desires to operate the engine at maximum load, the 
crankshaft 2 must be coupled to the crankshaft 1. To this end, the 
operator causes the control unit 12 (note the input 27b) to adjust the 
valve 27 so that the latter allows for gradual outflow of hydraulic fluid 
from the chamber 22. This causes the piston 33 to advance in a direction 
to the right, as viewed in FIG. 1, with attendant pivoting of the spring 
32 about its seat 40 in a direction to move its marginal portion 42 
against the projections 41 and to thereby gradually increase the 
frictional engagement between the clutch members 4 and 5 through the 
medium of the friction disc or discs 34. In other words, the magnitude of 
torque which the clutch member 4 transmits to the clutch member 5 
increases gradually at a rate which is a function of the speed of movement 
of the piston 33 in the chamber 22 toward the inlet-outlet opening 22a . 
The clutch member 5 gradually accelerates the second crankshaft 2. 
The monitoring devices 8 and 9 transmit signals which respectively denote 
the angular velocities of the crankshafts 2 and 1 as well as the angular 
positions of the respective crankshafts. When the crankshaft 2 assumes a 
predetermined angular position with reference to the crankshaft 1, and 
when the speed of the crankshaft 2 reaches or approximates the speed of 
the crankshaft 1, the output of the control unit 12 transmits a signal 
which causes the valve 27 to establish a practically unobstructed 
connection between the chamber 22 and the sump so that the piston 33 is 
free to abruptly move in a direction to the right. This enables the spring 
32 to fully engage the clutch members 4 and 5. From there on, the clutch 
member 5 rotates at the exact speed of the clutch member 4 and positively 
drives the crankshaft 2 through the medium of torque-transmitting gears 15 
and 16. 
The actuating device 7 can be modified in a number of ways without 
departing from the spirit of the invention. For example, this device can 
be replaced with a device which embodies or utilizes a liquid-filled 
bellows. Furthermore, it is possible to replace the hydraulic actuating 
device 7 with a mechanical device having means which responds to the 
output signal of the control unit 12 to change the condition of the spring 
32 and to thereby regulate the transmission of torque from the clutch 
member 4 to the clutch member 5, i.e., from the crankshaft 1 to the 
crankshaft 2. 
FIG. 1 further shows that the crankshaft 1 drives a pulley 38 which is 
installed outside of the casing 30 and receives torque from the end 
portion 3, for example, through the medium of the clutch member 4. The 
pulley 38 drives a V-belt 38a which can transmit motion to one or more 
auxiliary apparatus in the vehicle embodying the structure of FIG. 1. Such 
auxiliary apparatus may include the generator of the lighting system, a 
water pump or a cooling fan, not shown. 
An important advantage of the improved engine is that the crankshafts 1 and 
2 are parallel to each other. This ensures that the crankshafts are not 
subjected to torsional stresses which arise in an engine with serially 
arranged (coaxial) crankshafts (as disclosed, for example, in the 
aforementioned German Offenlegungsschrfit No. 28 28 298) when the engine 
is operated at maximum load. Consequently, the crankshafts 1 and 2 which 
are used in the engine of the present invention can be manufactured at a 
fraction of the cost of crankshafts which must be connected in series. As 
mentioned above, operation with less than the total number of cylinders 
allows for considerable savings in fuel and is desirable for ecological 
reasons (pronounced reduction of emission of deleterious combustion 
products into the surrounding atmosphere). The selection of the number of 
cylinders which are in use will be up to the operator of the vehicle which 
embodies the improved engine. As mentioned above, a single crankshaft will 
be driven by the respective group of cylinders immediately after starting 
and whenever the engine is to operate at partial load, and one or more 
additional crankshafts can be coupled to the crankshaft which is driven by 
the one group whenever the load upon the engine is to be increased. 
The mounting of all crankshafts (and of the corresponding camshafts) in a 
common housing is desirable and advantageous because it entails 
considerable savings in space, a reduction of the weight and reduction of 
initial cost of the engine. 
The mounting of the clutch outside of the casing 30 brings about the 
advantage that the component parts of the clutch are readily accessible 
for the purpose of maintenance, repair and/or replacement. 
FIG. 2 illustrates a modified construction wherein the clutch between the 
crankshafts 1 and 2 comprises cooperating clutch members 17 and 18. The 
crankshaft 1 is installed at a level below the crankshaft 2 and its end 
portion 3 drives a torque transmitting gear 15 meshing with a torque 
transmitting gear 16 which drives the clutch member 18. The latter 
corresponds to the clutch member 4 of FIG. 1. The clutch member 17 
corresponds to the clutch member 5 of FIG. 1 and serves to transmit torque 
to the second crankshaft 2. The end portion 3 of the lower crankshaft 1 
drives a pulley 37 which corresponds to the pulley 38 of FIG. 1. 
It will be noted that, contrary to the construction shown in FIG. 1, the 
structure of FIG. 2 embodies an accelerating clutch 17, 18 which is 
coaxial with the second crankshaft 2. The clutch including the clutch 
members 17 and 18 transmits torque to the second crankshaft 2 when the 
engine which drives the crankshafts 1 and 2 is to be operated at maximum 
load. The clutch member 18 surrounds a portion of the clutch member 17 
which latter is rigidly connected to the respective end portion of the 
upper crankshaft 2. 
All such components of the second apparatus which are identical with or 
clearly analogous to the corresponding components of the apparatus shown 
in FIG. 1 are denoted by similar reference characters. For example, the 
reference character 30 denotes the casing for the crankshafts 1 and 2, the 
reference character 12 denotes a control unit, the reference character 27 
denotes a valve, and the reference characters 8 and 9 denote monitoring 
devices which respectively monitor the rotational velocities and angular 
positions of the crankshafts 2 and 1. The belt or belts (not shown) which 
are driven by the pulley 37 of FIG. 2 can transmit motion to auxiliary 
apparatus including the aforementioned light generator, water pump and/or 
cooling fan. 
It is further within the purview of the invention to install the 
accelerating clutch between two camshafts (not shown) and to provide a 
positive-engagement second clutch between the crankshafts 1 and 2. The 
positive-engagement clutch is engaged when the accelerating clutch has 
accelerated the second camshaft to the exact speed of the first camshaft. 
Each camshaft rotates with the respective crankshaft. Reference may be had 
to the commonly owned copending application Ser. No. 233,952 filed Feb. 
12, 1981 by Lothar Huber et al. for "Apparatus for establishing and 
terminating connections between crankshafts". The disclosure of this 
copending application is incorporated herein by reference. When the two 
camshafts rotate at the same speed, the accelerating clutch permits for or 
initiates the engagement of the positive-engagement clutch which couples 
the second crankshaft to the first crankshaft so that the engine can be 
operated at maximum load. An advantage of the just mentioned modification 
which is disclosed in the copending application of Huber et al. is that 
the structure can be embodied with advantage in a four-cycle internal 
combustion engine wherein the camshaft always completes one revolution for 
the firing of the cylinders whereas the crankshaft completes two 
revolutions for each ignition or working stroke of the cylinders. The 
apparatus then allows for proper coupling of the camshafts to each other 
so as to ensure the firing of cylinders in proper sequence. 
The camshafts are preferably installed in the casing for the crankshafts 
and the actuating means may be designed to monitor the angular velocities 
of the camshafts and to effect engagement of the positive engagement 
clutch between the crankshafts when the continuously driven camshaft 
completes the acceleration of the other camshaft (associated with the 
crankshaft 2) to a desired speed and the other camshaft (and hence the 
respective crankshaft) assumes a predetermined angular position with 
reference to the continuously driven camshaft. The manner of monitoring 
the angular positions of the camshafts may be the same as or analogous to 
that described in connection with FIG. 1, i.e., the camshafts can include 
or carry portions (e.g., permanent magnets) which travel along endless 
paths past suitable transducers which generate signals at a frequency 
corresponding to the RPM of the respective camshafts, and such signals are 
transmitted to the corresponding inputs of a control unit having an 
evaluating circuit which ascertains the angular velocities of the two 
camshafts as well as the angular positions of the camshafts relative to 
each other and initiates coupling of the crankshafts to each other when 
the angular velocities of the two camshafts are identical or nearly 
identical and the accelerated camshaft assumes a predetermined angular 
position with reference to the continuously driven camshaft to thereby 
ensure that the cylinders of the engine will be fired in a desired 
sequence. 
Without further analysis, the foregoing will so fully reveal the gist of 
the present invention that others can, by applying current knowledge, 
readily adapt it for various applications without omitting features that, 
from the standpoint of prior art, fairly constitute essential 
characteristics of the generic and specific aspects of our contribution to 
the art and, therefore, such adaptations should and are intended to be 
comprehended within the meaning and range of equivalence of the appended 
claims.