Apparatus for Establishing and Terminating Connections Between Crankshafts

Certain features of the apparatus which is disclosed in the present case are referred to in the commonly owned copending application Ser. No. 233,960 filed Feb. 12, 1981 by Paul Maucher et al. for "Internal combustion engine with separable crankshafts" and in the commonly owned copending application Ser. No. 233,890 filed Feb. 12, 1981 by Lothar Huber for "Method and apparatus for separably connecting crankshafts in internal combustion engines".

The present invention relates to internal combustion engines in general, and more particularly to improvements in apparatus for saving energy during operation of internal combustion engines. Still more particularly, the invention relates to improvements in apparatus for coupling a second crankshaft to, or for disconnecting the second crankshaft from, a first crankshaft in order to save fuel for operation of internal combustion engines.

It is already known to save fuel by disconnecting one or more cylinders of a multi-cylinder internal combustion engine when the engine is to operate at partial load. For example, German Offenlegungsschrift No. 28 28 298 discloses a method of operating an internal combustion engine which has several cylinders installed in a common block. The engine further comprises several crankshafts including a first crankshaft in a first engine section embodying a first group of cylinders and a second crankshaft in a second engine section embodying a second (e.g., the remaining) group of cylinders. When the engine is operated at partial load, the second group of cylinders is deactivated by disengaging the corresponding (second) crankshaft from the other (first) crankshaft. In order to restart the temporarily deactivated section, the second crankshaft must be coupled to the first crankshaft in such a way that the two crankshafts will be maintained in predetermined angular positions with reference to each other to thereby ensure firing of the cylinders in proper sequence.

An object of the invention is to provide a novel and improved apparatus for selective coupling of a second crankshaft to a first crankshaft and for disengagement of the second crankshaft from the first crankshaft in a space-saving mannner and with a minimum of wear upon the motion transmitting parts.

Another object of the invention is to provide the apparatus with novel and improved means for establishing a torque transmitting connection between the crankshafts in a manner such that the establishment of connection is least likely to result in excessive wear upon and/or damage to the torque transmitting components.

A further object of the invention is to provide novel and improved clutch means for use in an apparatus of the above outlined character.

An additional object of the invention is to provide novel and improved means for accelerating one of several crankshafts in an internal combustion engine to the RPM of a continuously driven crankshaft in the same engine.

A further object of the invention is to provide novel and improved torque transmitting connections between the rotary components of several sections of an internal combustion engine.

An ancillary object of the invention is to provide a novel and improved clutch between discrete camshafts of an internal combustion engine of the type wherein each of several groups of cylinders can rotate a discrete crankshaft.

A further object of the invention is to provide a simple, rugged and reliable separable connection between the crankshafts of an internal combustion engine wherein each of the crankshafts can be rotated by a discrete cylinder or a discrete group of cylinders.

Another object of the invention is to provide the apparatus with novel and improved means for accurately timing the establishment of a connection between the crankshafts and for ensuring that the crankshafts are invariably coupled in proper angular positions relative to each other.

The invention resides in the provision of an apparatus for connecting or disconnecting first and second sections or units of an internal combustion engine (each such section can comprise a group of cylinders which are installed in a common cylinder block or a common casing). More specifically, the apparatus comprises first and second rotary crankshafts which respectively form part of the first and second sections of the engine, accelerating means operable to raise the speed of the second crankshaft to at least approximate the speed of the first crankshaft (it being assumed here that the first crankshaft is driven whenever the engine is on, i.e., regardless of the number of cylinders which are in use), and positive-engagement clutch means which is operative to positively couple the crankshafts to each other upon completed acceleration of the second crankshaft to the speed of the first crankshaft.

The accelerating means comprises or may comprise a camshaft which receives torque from the first crankshaft (e.g., by way of a gear train) and constitutes the input element of the accelerating means. The accelerating means may further comprise a second camshaft, means (e.g., a gear train) for transmitting torque from the second camshaft to the second crankshaft and a dry friction clutch or other suitable means for transmitting torque from the first to the second camshaft.

If the first and second crankshafts are coaxial with each other, they preferably have end portions which are adjacent to each other. The positive-engagement clutch means then preferably comprises a first clutch member which is driven by the end portion of the first crankshaft and has a first (e.g., toothed) profile facing the end portion of the second crankshaft, a second clutch member driven by the end portion of the second crankshaft and having a second (e.g., toothed) profile complementary to the first profile, and means (e.g., a set of springs) for axially movably securing at least one of the clutch members to the respective crankshaft so that the profile of the one clutch member can move into positive engagement with the profile of the other clutch member in response to movement of the one clutch member relative to the crankshafts. The apparatus then further comprises control means (e.g., control means including a plate-like member which is movable in parallelism with the axes of the crankshafts) for moving the one clutch member toward the other clutch member in response to completed acceleration of the second crankshaft. Still further, the apparatus preferably comprises means for maintaining the control means in a first predetermined position (in which the one clutch member is disengaged from the other clutch member) while the angular velocity of the second crankshaft deviates from the angular velocity of the first crankshaft. The apparatus preferably also comprises means for moving or for effecting the movement of the control means to another predetermined position (in which the one clutch member engages with the other clutch member) in response to completed acceleration of the second crankshaft to the speed of the first crankshaft.

The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The improved apparatus 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.

FIG. 1 is a partly elevational and partly longitudinal sectional view of an apparatus which embodies one form of the invention;

FIG. 2 is a transverse sectional view as seen in the direction of arrows from the line II--II of FIG. 1; and

FIG. 3 is a fragmentary partly elevational and partly longitudinal sectional view of a modified apparatus.

Referring first to FIG. 1, there is shown a first crankshaft 1 which is coaxial with a second crankshaft 4. That end portion 2 of the crankshaft 1 which is adjacent to and faces the crankshaft 4 carries a first clutch member 5 which has a profile 6 facing the crankshft 4 and consisting of alternating hills and valleys or teeth 6a and tooth spaces 6b shown in the middle of the upper portion of FIG. 1. The spaces 6b between the teeth 6a extend in parallelism with the axis of the crankshaft 1. The teeth 6a form an annulus which is concentric with the annulus of tooth spaces 6b and the centers of the two annuli are located on the axis of the crankshaft 1.

The clutch member 5 on the end portion 2 of the crankshaft 1 can be engaged with or disengaged from a second clutch member 7 which is indirectly connected to and is coaxial with the crankshaft 4. That end face of the clutch member 7 which faces the clutch member 5 has a profile 8 which is complementary to the profile 6 and also includes annuli of alternating hills and valleys or teeth 8a and tooth spaces 8b. When the clutch member 7 is moved axially of the crankshaft 4 in a direction toward the crankshaft 1, the teeth 8a penetrate into the tooth spaces 6b and the teeth 6a penetrate into the tooth spaces 8b. FIG. 1 shows the positive-engagement clutch including the clutch members 5 and 7 in disengaged condition, i.e., the profile 8 is remote from the profile 6 and the crankshaft 1 can rotate independently of the crankshaft 4 or vice versa.

If desired, the profiles 6 and 8 can be designed in such a way that the clutch member 7 can move into engagement with the clutch member 5 only in a single predetermined angular position of the crankshaft 1 with respect to the crankshaft 4 or in a relatively small number of predetermined angular positions. This can be readily achieved by providing the profile 6 with teeth 6a and tooth spaces 6b of varying width and/or length or depth (as considered in the circumferential and/or axial direction of the crankshaft 1), and by imparting to the profile 8 a similar configuration, i.e., by ensuring that each tooth 6a can enter only a predetermined tooth space 8b or one of a limited number of tooth spaces 8b, and that each tooth 8a can enter only a predetermined tooth space 6b or one of a limited number of tooth spaces 6b. Thus, if the clutch members 5 and 7 are to engage in two or more different angular positions whose total number is less than the number of teeth 6a or 8 a, the profiles 6 and 8 will include two or more identical halves, thirds, fourths, etc. During engagement of a clutch which is designed in the just described manner (so that the teeth 6a and 8a have different widths and/or lengths, as considered in the circumferential direction and/or the direction of the common axis of the camshafts 1 and 4, the engagement takes place after a certain amount of ratcheting of teeth 6a along the teeth 8a and vice versa, i.e., until the teeth 6a find tooth spaces 8a of appropriate width and/or depth and the teeth 8a also find tooth spaces 6b of requisite width and/or depth.

The clutch member 7 is indirectly connected to the crankshaft 4 in such a way that it shares all angular movements of the crankshaft 4 but is movable axially with respect thereto. The means for securing the clutch member 7 to the crankshaft 4 comprises composite resilient means including at least one first leaf spring 9 and at least one second leaf spring 22. Each of these springs is preferably a ring-shaped (dished) spring and can be flexed to the right or to the left, as considered in FIG. 1, but cannot be flexed in the circumferential direction of the crankshaft 4. The inner marginal portion of the spring 9 shown in FIG. 1 (as considered in the radial direction of the crankshaft 4) is non-rotatably connected to the front end portion 3 of the crankshaft 4 (the end portion 3 is that portion which is nearest to the clutch member 5 on the end portion 2 of the crankshaft 1) by screws, bolts or analogous fasteners 9a. The radially outermost or outer marginal portion of the spring 9 is connected with the radially outermost or outer marginal portion of the associated spring 22 by a connector 21 which is or may constitute a ring having a U-shaped cross-sectional outline. One flange of of the ring-shaped connector 21 is attached (e.g., riveted) to the radially outermost portion of the leaf spring 9, and the other flange of the connector 21 is secured (e.g., riveted) to the radially outermost portion of the leaf spring 22. The radially innermost or inner marginal portion of the leaf spring 22 is bolted, screwed or otherwise non-rotatably fastened (as at 22a) to that end face of the clutch member 7 which faces the end portion 3 of the crankshaft 4. The configuration and initial stressing of the leaf springs 9 and 22 are such that, in the absence of the application of any outside force, they maintain the clutch member 7 in the position which is shown in FIG. 1, i.e., the clutch member 7 is disengaged from the clutch member 5 on the crankshaft 1.

The apparatus of FIG. 1 further comprises means for centering the clutch member 7 with respect to the clutch member 5, i.e., with respect to the crankshafts 1 and 4. The centering means comprises a hollow cylindrical centering member 23 the right-hand portion of which extends into an axial bore 25 machined into the clutch member 7. The mounting of the centering member 23 is preferably such that it shares the angular movements of the clutch member 7 and crankshaft 4. The left-hand portion of the centering member 23 extends into an axial bore 26 which is machined into the right-hand end face of the clutch member 5 on the crankshaft 1. The bore 26 contains a cylindrical bearing sleeve 24 which surrounds the left-hand portion of the centering member 23 and allows the latter to move axially of the clutch member 5.

The axial bore of the centering member 23 accommodates a helical spring 66 which is installed in prestressed condition in such a way that it reacts against a conical internal shoulder of the centering member 23 and bears against the bottom surface in an axial bore 67 machined into the left-hand end face of the end portion 3 of the crankshaft 4. Thus, the spring 66 constitutes an energy storing device which permanently urges the clutch member 7 in a direction toward the clutch member 5 because the centering member 23 shares the movements of the clutch member 7. The clutch member 7 assumes an accurately defined position because it is always centered by the member 23. The latter further ensures that the clutch member 7 is mounted without any or without noticeable radial play relative to the crankshafts 1 and 4.

The apparatus of FIG. 1 further comprises a first camshaft 10 which is spaced apart from and parallel with the crankshafts 1 and 4. The shafts 1 and 10 form part of that unit or section of the internal combustion engine which is continuously driven, i.e., the camshaft 10 rotates when the crankshaft 1 receives torque from the corresponding cylinder or cylinders of the internal combustion engine. The means for transmitting torque between the shafts 1 and 10 comprises a gear train including a rotary member here shown as a spur gear 14 which is mounted on and drives the camshaft 10 and receives torque from a pinion 14a of or on the crankshaft 1. The camshaft 10 can accelerate the crankshaft 4 by way of a second camshaft 13 which is coaxial with the camshaft 10 and can be coupled to the camshaft 10 by a second clutch (called accelerating clutch) shown in the middle of the lower part of FIG. 1. This second clutch includes the parts which are denoted by reference characters 11, 12, 20, 17, 46 and 47 and will be described in greater detail below. The means for engaging the second clutch comprises a speed comparing device which, at the will of the driver of the vehicle, actuates the second clutch when the speed of the first camshaft 10 deviates from the speed of the second camshaft 13. In accordance with a presently preferred embodiment of the invention, the just mentioned speed comparing device includes an oil pump, e.g., a gear pump which causes oil or another liquid to flow into an annular chamber 19 along a path 36, 37, 38, 39 when the speed of the camshaft 10 deviates from the speed of the camshaft 13. The liquid in the chamber 19 acts upon an annular piston 20.

That side of the gear 14 which faces the camshaft 13 has a recess 30 for a gear 15 which forms part of the oil pump and is mounted on a shaft 31 one end portion of which is rotatably journalled in the gear 14 (see FIG. 1). The gear 15 meshes with a further gear 16 which also forms part of the oil pump and is non-rotatably secured to the left-hand end portion of the camshaft 13 (as viewed in FIG. 1), i.e., to that end portion of the camshaft 13 which is nearest to the camshaft 10. The camshafts 10 and 13 are coaxial with each other. The gear 16 is also located in the recess 30 of the gear 14, and the dimensions of the recess 30 are selected in such a way (see FIG. 2) that the surface surrounding this recess is closely adjacent to the top lands of teeth on the gears 15 and 16. In other words, the teeth of the gears 15, 16 define with the surface surrounding the gears 15, 16 a plurality of discrete compartments 68 wherein oil flows from an inlet opening or port 38 to an outlet opening or port 39 (see FIG. 2) when the rotational speed of the gear 14 deviates from that of the gear 16, i.e., when the orbital movement of the gear 15 about the axis of the gear 16 entails an angular displacement of the gears 15, 16 relative to each other. The port 39 discharges into the aforementioned annular chamber 19 for the annular piston 20. Thus, the teeth of the gears 15 and 16 act not unlike vanes which convey the hydraulic fluid from the port 38 to the port 39 when the gears 15, 16 rotate relative to each other. As shown in FIG. 2, the ports 38 and 39 are disposed at the opposite sides of the plane including the axes of the gears 15 and 16. When the gear 15 rotates in a counterclockwise direction (as viewed in FIG. 2), the gear 16 rotates in the same direction which means that the teeth of the gears advance discrete batches of liquid from the port 38, along the upper portion of the surface bounding the recess 30 and toward the port 39 as long as the gears 15, 16 turn relative to each other. At the same time, the teeth of the gear 16 transport batches of liquid from the port 38, along the lower part of the surface bounding the recess 30, and such batches merge with the batches supplied by the gear 15 prior to entering the port 39. Since the chamber 19 normally does not allow for escape of liquid except via port 39, the liquid which is pumped into the chamber 19 via port 39 displaces the piston 20 in a direction to the right, as viewed in FIG. 1, whereby the accelerating clutch couples the continuously rotating camshaft 10 with the second camshaft 13. The teeth or vanes of the gears 15, 16 draw liquid from a source (not shown) via suction channels 36, 37. The source is preferably the oil sump of the engine, i.e., there is no need to provide a separate source of liquid to be fed into the chamber 19. The sump (source of fluid) is shown in FIG. 1.

The right-hand side of the recess 30 (as viewed in FIG. 1) is overlapped by a cover or lid 18 which serves as a bearing member for the other end portion of the shaft 31 for the gear 15. Furthermore, the lid 18 has a central opening 32 for the left-hand end portion of the camshaft 13. Still further, the lid 18 has two concentric annular projections or ribs 33 and 34 the latter of which spacedly surrounds the former. The projections or ribs 33 and 34 define the aforementioned annular chamber 19 for the annular piston 20. The piston 20 is movable axially but is held against rotation in the chamber 19, i.e., the piston 20 shares the angular movements of the camshaft 10 and gear 14. When the speed of the camshaft 10 differs from the speed of the camshaft 13, the piston 20 is moved in a direction to the right, as viewed in FIG. 1, to thereby expose one or more liquid discharging openings in the annular projection or rib 33 and/or 34. In the embodiment of FIGS. 1-2, the projections 33, 34 are formed with liquid discharging openings 40, 41, 42 and 43. The openings 40 and 43 are provided in the outer projection 34 and the openings 41, 42 are provided in the inner projection 33. These openings return the liquid into the oil sump. In such axial position, the piston 20 urges one or more friction discs 12 against a clutch element 11 which is non-rotatably secured to the camshaft 13. Consequently, angular movements of the gear 14 and camshaft 10 are transmitted to the camshaft 13 whereby the latter rotates a gear 65 which, in turn, drives the crankshaft 4. When the speed of the camshaft 13 at least approximates the speed of the camshaft 10, the extent of angular movement of the gear 15 relative to the gear 16 is negligible or zero which means that the chamber 19 ceases to receive liquid via port 39. Therefore, a spring 28 which is mounted in the gear 65 can push the piston 20 against the left-hand end of the chamber 19, as viewed in FIG. 1, i.e., the accelerating clutch between the camshafts 10 and 13 is disengaged. The spring 28 is or may constitute a dished spring the marginal portion of which is fixedly connected with the gear 65 on the camshaft 13 and the innermost portion of which bears against the clutch element 11 so that the latter is biased in a direction to the left, as viewed in FIG. 1, i.e., toward the piston 20. When the piston 20 moves in a direction toward the gear 14 on the camshaft 10, it expels the liquid from the chamber 19, e.g., by way of a one-way valve 50 which can be actuated (opened) by the piston 20 when the latter assumes a predetermined axial position under the action of the spring 28. Opening of the valve 50 entails practically instantaneous escape of liquid from the chamber 19. The spring 28 urges the clutch element 11 in a direction toward the gear 14, and this clutch element rotates at or close to the speed of the gear 14 when the piston 20 opens the valve 50. This moves a projection or lobe 47 on the clutch element 11 into an opening or groove 46 when the camshaft 13 assumes a predetermined angular position with reference to the camshaft 10. The groove 46 is machined into or otherwise formed in a ring-shaped clutch element 17 connected to that side of the gear 14 which faces the camshaft 13. It is advisable to install a torsion damping or shock absorber device, e.g., a torsion spring 27, between the gear 14 and the ring-shaped element 17 so that the latter can turn through a predetermined angle with reference to the gear 14 in order to ensure that the projection or lobe 47 can enter the groove 46. Moreover, the torsion spring 27 can take up the initial stress when the lobe 47 penetrates into the groove 46 and the clutch element 11 begins to receive torque from the clutch element 17. It is clear that a torsion damping means in the form of a spring or the like can be installed at any desired locus of the path for transmission of torque from the camshaft 10 to the gear 65 on the camshaft 13.

As shown in FIG. 2, the apparatus which embodies the invention further comprises a plate-like control member 63 which has three fingers or arms 45 and defines two substantially semicylindrical sockets 63a, namely, a first socket between the two upper arms 45, and a second socket between the two lower arms 45, as viewed in FIG. 2. The upper half of the control member 63 can enter complementary grooves or depressions 61 in the periphery of the clutch member 7, and the lower half of the member 63 can enter complementary grooves or depressions 60 in the periphery of the clutch element 11. The purpose of the control member 63 is to ensure that the movements of the clutch member 7 are shared by movements of the clutch element 11 and vice versa, always to the same extent. Thus, and as already mentioned above, when the spring 28 is free to move the clutch element 11 in a direction to the left, as viewed in FIG. 1, because the RPM of the camshaft 13 matches or approximates the RPM of the camshaft 10, the control member 63 acts as a motion transmitting means and moves the clutch member 7 axially toward the crankshaft 1, i.e., toward the clutch member 5. This means that the profile 8 of the clutch member 7 engages the profile 6 of the clutch member 5 so that the crankshaft 1 drives the crankshaft 4. The control member 63 is mounted on and is movable in the axial direction of a shaft 62 which is parallel to the shafts 1, 4, 10 and 13. A coil spring 62a or other resilient or otherwise yieldable biasing means is provided to permanently urge the control member 63 to a predetermined position (as considered in the axial direction of the shaft 62), namely, to a starting position in which the clutch member 7 is disengaged from the clutch member 5 and, therefore, the clutch element 11 is disengaged from the composite clutch element including the gear 14 and the ring-shaped element 17 on the gear 14.

The operation of the apparatus which is shown in FIGS. 1 and 2 is as follows:

It is assumed that the internal combustion engine section or unit which includes the crankshaft 1 and the camshaft 10 is operative so that the crankshaft 1 rotates the gear 14 which drives the camshaft 10. Such situation can develop immediately after starting of the internal combustion engine. The control member 63 is then held in a position in which its upper and median fingers or arms 45 maintain the clutch member 7 out of engagement with the clutch member 5 and the median and lower fingers or arms 45 maintain the clutch element 11 out of engagement with the gear 14. In other words, the clutch including the clutch members 5, 7 is disengaged and the accelerating clutch including the piston 20 and the friction discs 12 is also disengaged. The piston 20 is held in the axial position of FIG. 1, and the chamber 19 for the piston 20 receives pressurized liquid because the gear 15 rotates relative to the gear 16, i.e., because the camshaft 10 rotates relative to the camshaft 13. If the camshaft 13 is to receive torque from the camshaft 10, the control member 63 is released for movement in the axial direction of the shaft 62, e.g., by means of a lever, pedal or an analogous actuating element (not shown), so that the spring 28 is free to move the clutch element 11 axially toward the piston 20. The piston 20 rotates with the gear 14, and such angular movement is transmitted to the clutch element 11 via friction discs 12. The camshaft 13 is accelerated so that its speed ultimately approximates or matches the speed of the camshaft 10 which is driven by the crankshaft 1. When the speed of the camshaft 13 at least approximates that of the camshaft 10, the extent of angular movement between the gears 15, 16 is reduced to zero or close to zero so that the gears 15, 16 cease to force additional liquid into the chamber 19. Therefore, the spring 28 can push the clutch element 11 in a direction to the left and the piston 20 is displaced by the clutch element 11 to actuate the valve 50 which abruptly allows the liquid to leave the chamber 19. This enables the lobe 47 to enter the groove 46 of the ring-shaped element 17 to thus establish a positive formlocking connection between the elements of the accelerating clutch intermediate the camshafts 10 and 13. Moreover, penetration of the lobe 47 into the groove 46 ensures that the clutch element 11 is located in a predetermined angular position with reference to the gear 14 and camshaft 10. Axial movement of the clutch element 11 in a direction to introduce the lobe 47 into the groove 46 is shared by the clutch member 7 which moves into engagement with the clutch member 5 because any axial movements of the element 11 must be shared by the member 7 owing to the provision of the control member 63. The crankshafts 1 and 4 then rotate in unison. This corresponds to normal operation of the engine, i.e., when the engine is operated at maximum or full load and each of the two crankshafts 1, 4 is driven by the respective group of cylinders of the internal combustion engine.

If the crankshaft 4 is to be disengaged from the crankshaft 1, e.g., when the engine is to be operated at partial load, the control member 63 is moved back to the illustrated position (for example, through the medium of the aforementioned lever, pedal or the like) so that the clutch including the components 11, 12 and 20 ceases to transmit torque. Also, the control member 63 disengages the profile 8 of the clutch member 7 from the profile 6 of the clutch member 5.

An important advantage of the improved apparatus is that, once the camshaft 13 is coupled to the camshaft 10, the camshaft 13 can accelerate the second crankshaft 4 via gears 65, 65a and the ratio of rotational speeds of the camshafts 10, 13 determines the timing of possible coupling of the crankshaft 4 to the crankshaft 1. Otherwise stated, positive engagement between the profiles 6, 8 of the clutch members 5, 7 can take place only subsequent to positive engagement between the clutch elements 11 and 17 (i.e., subsequent to penetration of the lobe 47 into the groove 46). The accelerating clutch (including the piston 20, discs 12 and clutch element 11) allows the camshaft 10 to rotate relative to the camshaft 13 while the latter is in the process of being accelerated to the angular velocity of the camshaft 10, the camshaft 13 is positively coupled to the camshaft 10 (by the lobe 47) when the angular velocity of the camshaft 13 is sufficiently high to match or closely approximate the angular velocity of the shaft 10 (i.e., when the RPM of the crankshaft 4 is sufficiently close to the RPM of the crankshaft 1 to warrant safe engagement of the profiles 6 and 8), and the crankshaft 4 is positively coupled to the crankshaft 1 when the difference between the speeds of the shafts 1 and 4 is zero or sufficiently small to enable the teeth 6a, 8a to respectively penetrate into the tooth spaces 8b, 6b.

The invention can be embodied with advantage in four-cycle internal combustion engines 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 improved apparatus allows for proper coupling of the camshafts 10, 13 to each other so as to ensure the firing of cylinders in proper sequence. The apparatus renders it possible to properly couple the crankshafts 1 and 4 to each other in spite of the fact that proper coupling must take place within an angle of 720 degrees rather than merely 360 degrees. Were the accelerating clutch placed between the crankshafts 1 and 4, it would be necessary to provide rather costly, bulky and sensitive additional control equipment in order to prevent coupling of the crankshaft 4 to the crankshaft 1 in a position at 360 degrees from the desired position.

The incorporation of our improved apparatus in an internal combustion engine not only brings about savings in fuel but also reduces the quantity of deleterious combustion products which are discharged into the atmosphere by conventional engines wherein all of the cylinders are operated if one of the cylinders is in operation, i.e., which do not allow for selective activation or deactivation of one or more groups of cylinders. The number of cylinders which cooperate with the crankshaft 1 may but need not be identical with the number of cylinders which rotate the crankshaft 4. This depends on the desired distribution of loads, i.e., on the desired ratio of partial load (some of the cylinders are in use) to maximum or full load when all of the cylinders are in action.

The speed monitoring and comparing means including the gears 15, 16 ensures that the spring 28 is free to move the clutch element 11 in a direction toward the gear 14 and to such an extent that the lobe 47 penetrates into the groove 46 only at a time when the speed of the camshaft 13 matches or closely approximates the speed of the camshaft 10. The speed of the shaft 10 is one-half the speed of the crankshaft 1, and the speed of the crankshaft 4 is twice the speed of the camshaft 13. Thus, the diameter of the gear 65a on the end portion 3 of the crankshaft 4 is half the diameter of the gear 65. Therefore, penetration of the lobe 47 into the groove 46 automatically ensures that the angular position of the crankshaft 4 relative to the crankshaft 1 is proper (within the angle of 720 degrees) when the profile 8 is free to move into positive engagement with the profile 6.

An advantage of the valve 50 is that it can provide a relatively large path for escape of liquid from the chamber 19 as soon as the spring 28 is free to move the piston 20 to an axial position in which the latter opens the valve 50. This insures that the piston 20 need not expel liquid from the chamber 19 by way of relatively narrow port 39, i.e., along the path 36-39 which admits liquid into the chamber 19 while the piston 20 moves toward the position of engagement with the friction discs 12, i.e., toward the position in which the accelerating (friction) clutch transmits torque from the camshaft 10 to the camshaft 13.

The control member 63 is shiftable between three different positions, namely, a first position in which the engine operates in the partial load range because the member 63 prevents the friction discs 12 from bearing against the clutch element 11 even if the piston 20 assumes its rightmost position, as viewed in FIG. 1; a second position in which the piston 20 can accelerate the camshaft 10 via friction discs 12; and a third position (full load) in which the clutch member 7 positively engages the clutch member 5 as a result of engagement between the profiles 6 and 8.

The structure which is shown in FIGS. 1 and 2 can also be used to drive one or more pieces of auxiliary equipment. Thus, the camshaft 10, which is rotated whenever the engine drives the crankshaft 1, can transmit torque to a rotary member 51, such as a pulley or a sprocket wheel, by way of a gear 52, which is driven by the gear 14, and a shaft 150 which connects the gear 52 with the rotary member 51 and is journalled in the casing or housing 64 for the clutches or in the cylinder block of the engine.

Instead of the just described power takeoff, the constantly driven camshaft can transmit motion to a modified takeoff in a manner as illustrated in FIG. 3. The camshaft 13 of FIG. 1 is replaced with a hollow camshaft 113 which surrounds an extension 110a of the constantly driven camshaft 110 replacing the camshaft 10. The extension 110a is journalled in the housing 164 for the clutches or in the cylinder block and rotates a pulley, a gear, a cam, a sprocket wheel or any other suitable rotary member 151.

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.