The invention relates to an apparatus for camshaft timing adjustment. The apparatus comprises at least a drive disc and a hub with a common rotational axis and being supported relative to each other to enable a swiveling movement of the hub and the drive disc relative to each other. The drive disc comprises at least two fluid chambers, being separated from each other by radially extending separation means. The fluid chambers are each separated by a vane being attached to the hub into a first sub-chamber and a second sub-chamber. Description of the related art

Most combustion engines require a cam shaft for opening and closing the intake valves and outtake valves. The cam shaft is typically driven by the crank shaft via some sort of transmission, mostly by a chain drive or a belt drive. In four stroke engines (i.e. Otto-type engines) the cam shaft rotates with half the speed of the crank shaft. To optimize loading and unloading the cylinders, the angular relation of the cam shaft's rotational position relative to the crank shaft's rotational position can be adjusted, e.g. in response to changes of throttle position or rpm (rotations per minute) of the crank shaft. This change in angular relation is as well referred to as 'timing' as the angular relationship defines the point of time of opening and closing the respective valves(s) relative to a particular position of the respective piston.

Generally speaking, a drive disc, like e.g. a sprocket or a pulley, may be attached to the cam shaft. By driving the drive disc, the cam shaft rotates accordingly. To adjust the timing of the cam shaft during operation of the combustion engine it has been suggested to support the drive disc on a hub, the latter being connected to the cam shaft. By adjusting the angular relation of the hub to the drive disc, the angular relation of the cam shaft to the crank shaft and thus the timing maybe varied. To enable the angular adjustment of the hub relative to the drive disc a hydraulic drive in the drive disc-hub unit has been suggested by attaching vanes to the hub. The vanes each separate a fluid chamber in the drive disc into a first sub-chamber and a second sub-chamber. A hydraulic oil pump is connected to the first and second chambers to pump oil from one sub-chamber into the other, thereby swivelling the hub relative to the drive disc. The hydraulic pump is typically driven by the crank shaft. Pumping of the fluid from one sub-chamber into the other is controlled by a valve unit. Examples of this type of timing ad- justment apparatus are disclosed e.g. in US 8,291,876 Bl and US 6,453,859 Bl.

Summary of the invention

The problem to be solved by the invention is to provide a reliable, light weight and easy to manufacture camshaft timing apparatus.

Solutions of the problem are described in the independent claim. The dependent claims relate to further improvements of the invention.

The apparatus for camshaft timing adjustment, which can as well be referred to as camshaft timing apparatus comprises at least a drive disc and a hub with a common rotational axis. The drive disc and the hub are supported relative to each other to enable a swiveling movement of the hub relative to and the drive disc.

The hub may comprise coupling means for attaching the hub to a cam shaft of a combustion engine. They thus may form a drive-disc hub unit. The drive disc may be connected or configured to be connected by some sort of transmission to a crank shaft of a combustion engine, e.g. by a belt drive, a gear drive, a chain drive or the like. Of course, the hub can as well be attached to the crank shaft and the drive disc may be connected by the transmission to the cam shaft. For simplicity only, it is assumed herein that (i) the hub is attached to or configured to be attached to the camshaft, and that (ii) the disc drive is driven via some transmission by the crank shaft, but without restricting the application to this preferred example installation. The drive disc may be attached to the hub via a bearing enabling the drive disc to swivel relative to the hub. For example, the hub may comprise a first plain bearing surface and the drive disc may comprise a complementary second plain bearing surface providing a plain bearing when attached to each other. Other types of bearings may as well be used. The drive disc comprises, i.e. encloses at least one, preferably two fluid chambers being separated from each other by radially extending separation means. The separation means may thus have side faces providing a boundary of the fluid chamber in clockwise and/or counterclockwise direction. The fluid-chambers comprise a fluid, like e.g. a hydraulic oil or the like. The separation means do not necessarily have straight side faces. These side faces can be curved and/or inclined against the radial direction, but the radially extending separation means provide a radially extending barrier between two fluid chambers being formed by or attached to the drive disk. Only to avoid ambiguities, the side faces of the separation means provide a boundary in the circumferential direction, i.e. per- pendicular to the axis of rotation and not radially. The separation means in some sense are spokes but they do not need to bear radial loads. In this picture the side faces of two neighbored spokes would face each other. In between of the side faces of two neighbored separation means is a fluid chamber. These fluid chambers each accommodate a vane being attached to the hub. The vanes sepa- rate the fluid chambers into a first sub-chamber and a second sub-chamber. In other words, the vanes inhibit a free (i.e. uncontrolled) fluid exchange between the sub-chambers of the respective fluid chamber. The vanes are preferably in touch with the front and rear boundary of the fluid chamber and with the radial boundary. The vanes are movably supported e.g. by the hub to pivot in the respective fluid chamber. Thus, by providing a fluid flow from the first sub- chambers into the second sub-chambers, the hub can be swiveled relative to the drive disc. To provide this fluid flow, each vane rotatable supports a sprocket. Alternatively or additionally, the fluid flow can be provided by sprockets being rotatable supported by the disc, e.g. in the region of the separation means. This is subsequently referred to as the support of sprockets by the separation means, even if the bearing is not provided by the separation means. The wording "support of sprockets by the separation means" shall simply expresses that sprockets may as well be positioned in recesses of the separation means, preferably a single sprocket in each separation means.

Only to avoid any misunderstanding, the verb 'to swivel' indicates a rotation of the two parts relative to each other around the common rotational axis. The term is used to indicate that the rotation is limited to an angle of rotation. The limitation is due to constructional details of the particular embodiment e.g. the space being provided between the separation means the dimensions of the vane(s).

The sprockets are geared with a gear wheel for driving the sprockets. The gear wheel can be connected to any kind of rotary drive. In the simplest case the rota- ry drive is an electric motor. The gear wheel is preferably at least approximately centered (radial displacement ±25% of the gear wheel's diameter and ±20° tilt angle) on the common rotational axis.

The sprockets are in contact with the fluid in the fluid chamber. As the vane and the separation means separate sub-chambers, the sprockets are in contact with the fluid in a first sub-chamber and with the fluid in a second sub-chamber. In case the sprockets are supported by the vane, the first and second sub-chambers belong to the same fluid chamber. In case the sprockets positioned in recesses of the separation means, the first and second sub-chambers belong to different fluid chambers. Thus, in any case a rotation of the sprockets due to a rotation of the gear wheel enables to provide a pressure gradient between a first sub- chamber and the respective second sub-chamber. Only to avoid a misunder- standing, if the sprockets are in contact with the fluid in the respective sub- chambers, this implies, that the vane or the separation means comprise at least one recess into which the respective sprocket is positioned and which is in fluid communication with the two respective sub-chambers, as will be explained by way of example below in more detail. Only for clarity, the vane and/or the separation means may thus each provide a fluid passage connecting two sub-chambers. The teeth of the sprockets (and/or the gear wheel) engage into the respective fluid passage. Thus a rotation of the gear wheel and/or the sprockets enables to drive the fluid through the vane or the separation means, respectively.

It is thus sufficient to control the rotational speed of the gear wheel relative to the hub to rotate (swivel) the hub relative to the drive disc. Controlling of the rotational speed can be obtained very simple, e.g. by an electric motor having an output shaft being coupled to the rotor. In the simplest case, the output shaft of the electric motor is simply attached to the gear wheel. In the past, the engine's oil pump was used to supply a hydraulic camshaft adjustment drive. This arrangement had a couple of disadvantages, one is that in particular upon cold start of the combustion engine the camshaft adjustment is not available unit the oil pressure builds up; in addition fluid flow losses had been significant. These disadvantages are resolved by the invention. In addition the combustion engine's oil pump can be dimensioned significantly smaller saving weight and cost.. For example, the separation means may each be provided by at least one protrusion of the drive disc. The separation means and thus the protrusions extend in a radial direction between the fluid chambers.

In a preferred embodiment, the gear wheel is a pinion being supported by the hub. In example, the gear wheel is placed in between of the fluid chambers. Rotating the gear wheel thus provides a fluid flow from the first sub-chamber of a first fluid chamber into a second sub-chamber of a second fluid chamber, or vice versa, depending on the rotational direction of the drive wheel. Preferably, the radial inwardly facing side of at least one separation means or a land of the hub encloses the gear wheel partially, to form fluid pockets in between of two neighbored teeth of the gear wheel. The gear wheel thus can be considered as rotor of a rotary feeder.

In a second preferred embodiment, the gear wheel is an internal gear. For example, the separation means may each provide at least one plain bearing surface supporting a peripheral plain bearing surface of the internal gear. This provides a reliable and simple to manufacture bearing of the gear wheel.

For example, the separation means may have channel connecting a first sub- chamber of a first fluid chamber with a second sub-chamber of second fluid chamber. The radially inward facing boundary of the channel may be the plain bearing surface supporting a complementary peripheral plain bearing surface of the gear wheel. The radially outward facing side of the channel may enclose a fluid pocket between two neighbored teeth of the gear wheel. Thus, when the gear wheel rotates, the pockets 'move' along the channel and transport fluid from the first sub-chamber in the second sub-chamber (or vice versa, depending on the rotational direction of the gear wheel).

Preferably, the gear wheel has a rotational axis which is at least essentially parallel (±30°, preferably ±20, even more preferred ±10° or even better ±2,5°) with the common rotational axis. This eases manufacturing and enhances the life cycle of the apparatus.

The sprockets preferably have at least essentially parallel rotational axes. This optimizes the fluid flow between the sub-chambers and eases manufacturing of the apparatus. Again, at least essentially parallel means that a deviation from parallelism is smaller or equal to ±30° (preferably ±20, even more preferred ±10° or even better ±2,5°).

The sprockets' the rotational axes are at least essentially parallel (±30°, preferably ±20, even more preferred ±10° or even better ±2,5°) to the common rota- tional axis. As well they are preferably evenly spaced to the common rotational axis (preferably within ±20%, even more within ±10° or even better within ±2,5°) Both measures simplify manufacture and enhance lifetime as constructional imbalance of the apparatus is reduced.

Preferably, the vanes and/or the hub provide a passage for teeth of the sprock- ets, wherein a boundary of the passage and two neighbored teeth pointing towards said boundary of the passage form a fluid pocket, being moved through the passage from one side of the vane to the opposed side of the vane when the sprockets rotate.

If the separation means are provided by protrusions being attached to or inte- grally formed with drive disc, the apparatus can be kept very compact and thus small. For example the drive disc may comprise a front facing side and a rear facing side enclosing the fluid chambers axially. A ring, being attached to the front and/or rear facing side(s) may enclose the fluid chambers radially. The ring may support teeth, as well referred to as cogs, e.g. for engaging with a toothed drive belt, a drive chain and/or a cog wheel, all of which may be used to couple the apparatus to a crank shaft. As apparent from the above, the sprockets are as well gear wheels. The term 'sprocket' has been used only to enable a linguistic distinction between the different gear wheels. The gear wheel and the sprockets preferably have an at least essentially circular cylindrical envelope. This means that the tips of the teeth of the gear wheel (or of each sprocket) are lines lying in a circular cylindrical surface being centered on the respective rotational axis.

The apparatus of the invention can as well be used for other applications, i.e. not only for camshaft timing, but e.g. for anti-roll bar adjustment. The apparatus enables to adjust the preload of a torsion bar and thus of an anti-roll bar. More generally speaking the apparatus can be considered as a drive enabling an angular adjustment of two pieces being rotatable supported, i.e. being rotatable relative to each other around the common rotational axis. Thus more generally speaking the term 'hub' as used above and in the claims can be replaced by the term 'first piece' and the term 'drive disc' can be replaced by 'second piece being rotatable relative to the first piece'. Operation of the apparatus enables to swivel the first and second pieces relative to each other quickly even if high torques are required for this swiveling.

Description of Drawings

In the following the invention will be described by way of example, without limi- tation of the general inventive concept, on examples of embodiment with reference to the drawings.

Figure 1 shows an exploded view of a first camshaft timing apparatus.

Figure 2 shows an axial front view of the partially assembled first camshaft timing apparatus. Figure 3 shows an exploded view of a second camshaft timing apparatus. Figure 4 shows an axial front view of the partially assembled second camshaft timing apparatus.

Figure 5 shows a view of a partially assembled third camshaft timing apparatus.

Figure 1 shows an exploded view of the main components of a first apparatus for camshaft timing adjustment, as well referred to as camshaft timing apparatus 1. The apparatus 1 comprises a drive disc 10 being rotatable supported by a hub 50. The drive disc 10 has a rear disc 11 to which a ring 15 is attached. The peripheral surface of the ring 15 has cogs for engaging e.g. with a toothed belt. Inside the ring 15 are separation members 12 (as well referred to as 'separation

means 12'), separating two fluid chambers 20, being essentially recesses of the drive disc 10. As can be seen, the separation means 12 can be considered as radially extending protrusions separating the two fluid chambers 20. The separation means thus have side faces 13 providing a boundary of the fluid chamber in the clockwise and counterclockwise direction. The radial boundary 14 of the fluid chambers can be provided e.g. by the radially inward facing surface of the ring 15. The fluid chambers can be closed by a front disc (i.a. a front cover), which is omitted for simplicity. Inside of the fluid chambers 20 are vanes 60. The vanes 60 separate each fluid chamber 20 into a first sub-chamber 21 and a second sub-chamber 22 as can be best seen in Fig. 2. Accordingly, the separation members 12 have side faces 13 facing towards side faces 63 of the vanes 60.

The vanes 60 are attached to the hub, thus if the vanes rotate in the fluid chambers 20 the hub 50 rotates relative to the drive disc 10. For example, the hub 50 can be mounted to a cam shaft and the drive disc 10 can be connected to a crank shaft. Thus, swiveling the vanes 60 in the fluid chambers 20 enables to adjust the angular relation between the cam shaft and the crank shaft, which is referred to as camshaft timing adjustment. This swiveling can be controlled by rotating a gear wheel 70, being rotatable supported by the hub 50 in between of the two vanes 60. The rotational axis of the gear wheel 70 is at least essentially identical with the common rotational axis 2. Each vane 60 rotatable supports a sprocket 80 being geared with the gear wheel 70. Thus, if the gear wheel rotates, the sprockets 80 are driven to rotate in opposite directions relative to each other around their respective rotational axes 3 (see Fig. 2). Each vane 60 provides a radially inward facing surface 64. This surface 64 provides a boundary 64 of a passage for the teeth 81 of the sprockets 80. The boundary 64 encloses a fluid pocket 82 being formed between neigh- bored teeth 81 of the sprockets 80. Accordingly, rotating the sprockets 80 will transport fluid via the passage from the first sub-chambers 21 of both fluid chambers to the respective second sub-chamber 22 of the same fluid chamber (or in the other direction, depending on the direction of the rotation). This fluid transport provides fluid flow changing the volume of the fluid in the sub- chambers 21, 22. Thus, the vanes 60 (and accordingly the hub) swivel to compensate for the change in volume (assuming an essentially incompressible fluid in the fluid chambers 22).

In addition, the hub 50 of the first example has ring segment like lands 55. The lands 55 each provide a gear wheel facing surface 54 extending over the teeth 71 of the gear wheel 70 and enclosing fluid pockets 72 being provided by neighbored teeth 71 of the gear wheel. When the gear wheel 70 rotates, the fluid pockets 72 transport fluid from the first sub-chambers 21 of a first fluid chamber 20 to the second sub-chamber 22 of the respective other fluid chamber 20 (assuming the same direction of rotation as above, which as well can be inverted by changing the direction of rotation of the gear wheel 70). Thus, there exists as well a flow of the fluid between the fluid chambers 20, enhancing swiveling of the vanes 60 (and thus of the hub 50) relative to the drive disc 10 via a passage of the hub 50 for the teeth 71 of the gear wheel 70. Alternatively, the passage could be provided by the radially inwardly facing sides of the separation means 12 (if the lands 55 are omitted). The gear wheel 70 can be driven, e.g. by an electric motor which may be connected to the gear wheel in any known manner, e.g. via an optional drive spigot 73 (see Fig. 1) extending through the front cover. Alternatively the gear wheel 70 may be attached to the front cover, the latter being driven by any kind of motor, e.g. by an electric motor.

Figure 2 shows an exploded view of the main components of a second camshaft timing apparatus 1. The apparatus comprises as well a drive disc 10 being rotata- ble supported by a hub 50. The drive disc 10 has a rear disc 11 to which a ring 15 is attached. The peripheral surface of the ring 15 has cogs e.g. for engaging with a toothed belt. Inside the ring 15 are separation members 12, separating two fluid chambers 20, being essentially recesses of the drive disc 10, as explained with respect to Fig. 1. Again, the separation means 12 can be considered as radially extending protrusions separating the two fluid chambers 20. The fluid chambers 20 can be closed by a front disc (e.g. a front cover), which is again omitted for simplicity. Inside of the fluid chambers 20 are vanes 60. The vanes 60 separate each fluid chamber 20 into a first sub-chamber 21 and a second sub- chamber 22, as can be best seen in Fig. 4. The vanes 60 are attached to the hub 50, thus if the vanes 60 rotate in their respective fluid chambers 20 the hub50 rotates relative to the drive disc 10. As apparent, the reference numerals as used with respect to Fig. 1 and 2 have been used for the same or similar parts in Fig. 3 and 4.

The separation means 12 have a ring segment shaped channel, preferably being centered with the common rotational axis 2. The channel 16 has a radially inward facing boundary 17 providing a plain bearing surface supporting the peripheral plain bearing surface 76 of a gear wheel 70, being provided by the gear wheel's peripheral surface. Here, the gear wheel is an internal gear, i.e. it comprises a ring having cogs 71 as well referred to as teeth 71 at its radially inwardly facing side. The gear wheel's 70 rotational axis is at least essentially identical with the common rotational axis. The gear wheel 70 is geared with sprockets 80, being rotatable supported by the vanes 60. The sprockets 80 have rotational axes 3, being at least essentially parallel to the common rotational axis 2. The vanes 60 can be considered to be a part of the hub and in this sense the sprockets 80 are supported by the hub 50. A rotation of the gear wheel 70 thus drives the sprockets 80 and driving the gear wheel 70 transports fluid from the first sub- chamber 21 of a fluid chamber 20 into the second sub-chamber of the respective same fluid chamber 20. To this end, the hub 50 provides a radially outward facing surface 56. This radially outward facing surface 56 provides a boundary 56 of a passage for the teeth 81 of the sprockets 80. The boundary 56 encloses fluid pockets 82 being formed between neighbored teeth 81 of the sprockets 80. Thus rotating the sprockets 80 will transport fluid via the passage from the first sub- chambers 21 to the respective second sub-chamber 22 (or in the other direction, depending on the direction of the rotation). This fluid transport proved a fluid exchange between the sub-chambers 21, 22. Thus, the vanes 60 swivel to compensate for the change in volume (still assuming an essentially incompressible fluid in the fluid chambers 22). In addition the gear wheel 70 provides a fluid transport by moving fluid pockets 72 being formed by neighbored teeth 71 of the gear wheel 70 and a radially outward facing boundary 18 of the channel 16. Thus, driving the gear wheel 70 as well provides a fluid flow is from each first sub-chamber 21 of a fluid chamber 20 into the second sub-chamber 22 of the respective other fluid chamber 20 via the channel 16 (assume the same rotational direction as above). Of course the vanes 60 can be swiveled in the other direction by inverting the fluid flows, which in practice can be obtained by simply in- verting the direction of rotation of the gear wheel.

Figure 5 shows the main components of a further apparatus for camshaft timing adjustment, as well referred to as camshaft timing apparatus 1. The apparatus 1 comprises a drive disc 10 being rotatable supported by a hub (being similar to the hub 50 in Fig. 1). The drive disc 10 has a rear disc 11 to which a ring 15 is at- tached. The peripheral surface of the ring 15 has cogs for engaging e.g. with a toothed belt. Inside the ring 15 are separation members 12 (as well referred to as 'separation means 12'), separating two fluid chambers 20, being essentially recesses of the drive disc 10. As can be seen, the separation means 12 can be considered as radially extending protrusions separating the two fluid chambers 20. Like in the embodiment of Fig. 1 and 2, the separation means thus have side faces 13 providing a boundary of the fluid chamber 20 in the clockwise and counterclockwise direction. The radial boundary 14 of the fluid chambers can be provided e.g. by the radially inward facing surface of the ring 15. The fluid cham- bers can be closed by a front disc (i.a. a front cover), which is omitted for simplicity. Inside of the fluid chambers 20 are vanes 60. The vanes 60 separate each fluid chamber 20 into a first sub-chamber 21 and a second sub-chamber 22. Accordingly, the separation members 12 have side faces 13 facing towards side faces 63 of the vanes 60. The vanes 60 are attached to the hub, thus if the vanes rotate in the fluid chambers 20 the hub rotates relative to the drive disc 10. For example, the hub 50 can be mounted to a cam shaft and the drive disc 10 can be connected to a crank shaft. Thus, swiveling the vanes 60 in the fluid chambers 20 enables like in the other embodiments to adjust the angular relation between disc and the hub and thus between the cam shaft and the crank shaft, which is referred to as camshaft timing adjustment.

This swiveling can be controlled by rotating a gear wheel 70, being rotatable supported by the hub 50 in between of the two vanes 60. The rotational axis of the gear wheel 70 is at least essentially identical with the common rotational axis 2. Each separation means 12 provides a recess for rotatable supporting a sprocket 80 being geared with the gear wheel 70. As explained above, the bearing may be provided by a pin, a trunnion or the like (i.e. by some sort of bearing means) being attached to the disc 11, but the recess at least partially encloses the respective sprocket and has openings providing a fluid communication of the recess with the two chambers 20 being separated from each other by the separation means.

Thus, if the gear wheel 70 rotates, the sprockets 80 are driven to rotate in oppo- site directions relative to each other around their respective rotational axes 3. Each separation means 12 provides a radially inward facing surface 17. This radial inwardly facing surface 17 provides a boundary of a passage for the teeth 81 of the sprockets 80. The boundary encloses fluid pockets 82 being formed between neighbored teeth 81 of the sprockets 80. Accordingly, rotating the sprockets 80 will transport fluid via the passage from the first sub-chambers 21 of both fluid chambers to the second sub-chambers 22 of the respective other fluid chamber 20 (or in the other direction, depending on the direction of the rotation). This fluid transport provides fluid flow changing the volume of the fluid in the sub- chambers 21, 22. Thus, the vanes 60 (and accordingly the hub) swivel to com- pensate for the change in volume (assuming an essentially incompressible fluid in the fluid chambers 22). The space in between the radial inwardly facing surfaces 17 and the sprocket's body can thus be considered as fluid passage connecting a first and a second sub-chamber (of two different fluid chambers 20) and into which fluid passage the teeth 71 of the sprockets 70 engage. Similarly, the vanes 60 provide as well each a fluid passage connecting a first and a second sub-chamber, but of the same fluid chamber 20. The teeth 71 of the gear wheel 70 engage into the fluid channels and thus rotation of the gear wheel 70 as well provides a fluid transport between the respective first and second sub- chambers 21, 22 and thereby enhances a rotation of the vanes 60 (and thus the hub) relative to the disc 10. List of reference numerals

1 apparatus for camshaft timing adjustment

2 common rotational axis

3 rotational axes of sprockets

10 drive disc

11 rear disc

12 separation means / protrusion

13 side face of separation means

14 radial boundary

15 ring

16 channel in separation means

17 radial inward facing boundary / radial inward facing side

18 radial outward facing boundary / radial outward facing side 20 fluid chamber

21 first sub-chamber

22 second sub-chamber

50 hub

54 radially inward facing surface / gear wheel facing surface

55 land

56 radially outward facing surface

60 vane

63 side wall of vane

64 inwardly facing surface / boundary

70 gear wheel

71 tooth

72 fluid pocket

73 drive spigot (optional) radially outward facing surface of gear wheel sprocket

tooth / teeth

fluid pocket