ROTOR FOR A HYDRAULIC CAMSHAFT PHASER

The invention relates to a rotor for a hydraulic camshaft phaser, comprising a hub that holds a camshaft and comprising an outer shell with a plurality of vane elements, whereby hydraulic-medium channels run from the interior of the hub to the outer shell. The invention also relates to a hydraulic camshaft phaser having such a rotor.

BACKGROUND

A rotor and a camshaft phaser of the above-mentioned type are disclosed, for example, in U.S. Pat. No. 7,661,397 B2. In such a camshaft phaser, the rotor is mounted in a stator so that it can rotate around an axis of rotation. The phase shift of a camshaft with respect to a crankshaft of an internal combustion engine can be set by rotating the rotor relative to the stator. For this purpose, when the camshaft phaser is in the installed state, the rotor is non-rotatably joined to the camshaft while the stator is non-rotatably joined to the crankshaft of the internal combustion engine.

According to U.S. Pat. No. 7,661,397 B2, the rotor has a hub that holds the camshaft. A plurality of vane elements is arranged on the outer shell of the rotor, and each of these vane elements engages between separating elements of the stator so as to seal them. Each vane element divides the space between two separating elements into two pressure chambers that can alternately be supplied with a hydraulic medium via hydraulic-medium channels running from the interior of the hub to the outer shell. When one of the pressure chambers is charged with a hydraulic medium while the hydraulic-medium channel of the other pressure chamber is opened towards an outlet, the rotor is adjusted vis-à-vis the stator. The pressure chamber that—when it is charged with a hydraulic medium—leads to an advance of the rotor with respect to the stator is also referred to as the early-adjustment chamber. The other pressure chamber is correspondingly referred to as the late-adjustment chamber. In order to establish a connection to the hydraulic control system, the hydraulic-medium channels in the hub are flow-connected to axial supply spaces that are situated in the camshaft and that can be activated from the outside, or else these hydraulic-medium channels are connected directly to a central valve that is integrated into the camshaft.

SUMMARY OF THE INVENTION

Since rotors of this type require a great deal of material, they have the drawback that they are very heavy and also labor-intensive to manufacture because of the processing steps needed to create the hydraulic-medium channels, for instance, by means of drilling.

It is an object of the invention to provide a rotor of the above-mentioned type that, to the greatest extent possible, is lightweight as well as easy to manufacture. Furthermore, a camshaft phaser of the above-mentioned type that is correspondingly lightweight and easy to manufacture is also being provided.

The present invention provides a rotor having a hub that holds a camshaft and having an outer shell with a plurality of vane elements—whereby hydraulic-medium channels run from the interior of the hub to the outer shell—in that at least one hydraulic-medium channel is interrupted by an axial recess in the material, whereby a bushing that connects the interrupted hydraulic-medium channel is inserted into the recess in the material.

In this context, in a first step, the invention is based on the notion that the area that can be cut away or exposed on a rotor is fundamentally an area that does not have a bearing or sealing function. In the invention, however, it has surprisingly been found that, in a second step, especially the area of a hydraulic-medium channel can be exposed, even though this fundamentally interrupts the connection of the pressure chamber to the hydraulic system. The flow-connection of a hydraulic-medium channel that has been interrupted by an exposed section or by a recess created in the material is re-established in a simple manner by an inserted bushing.

A recess in the material—something that had not been taken into consideration up to now—in the area of a hydraulic-medium channel or in the area of several hydraulic-medium channels makes it possible to manufacture a rotor that weighs considerably less than the prior-art types. The hydraulic-medium channels that are interrupted by the recess in the material are connected by simply inserting an appropriate bushing into the open recess in the material. In particular, the bushing can be made of plastic by means of non-cutting shaping. However, it can also be made of metal, for instance, aluminum.

In order to achieve a reliable coupling in terms of the flow as well as a relatively simple sealing, the inner diameter of the bushing is selected so as to be larger than the diameter of the appertaining hydraulic-medium channel that has been cut open. This also simplifies the insertion of the bushing into the recess in the material since, to a certain extent, this measure makes allowance for tolerances in the alignment of the inserted bushing with respect to the hydraulic-medium channel that has been cut open. Advantageously, the bushing has positive-fit elements which, as they interact with complementary shapes on the rotor, only allow the bushing to be inserted in a precise position and with the proper angle orientation.

A preferred variant ensures the sealing function of the bushing that bridges the recess in the material in that the bushing is inserted with an axial press fit vis-à-vis the hydraulic-medium channel. If the bushing is made of a suitable flowable plastic, a permanent sealing functionality that is sufficient for the camshaft phaser is achieved. If the bushing is made of a fiber-reinforced plastic, then preference is given to a material that has a thermal expansion coefficient that is comparable to that of the material of the rotor. For instance, a fiberglass-reinforced epoxy resin can be employed as the material for the bushing in the case of a rotor made of aluminum.

The recess made in the material of the rotor is preferably rotation-symmetrical in order to avoid an unbalance. In particular, several ring-segmented recesses can be provided in the material, each of which interrupts several hydraulic-medium channels. In an advantageous variant, the recess in the material is essentially in the form of an annular space that interrupts several hydraulic-medium channels and that is situated between the hub and the outer shell, whereby, in each case, a bushing is inserted in order to connect each of the interrupted hydraulic-medium channels. Thanks to this configuration, the weight of the rotor can be greatly reduced. With an eye towards a simple angle-oriented installation of the bushing, the annular space is advantageously interrupted by at least one radial web. Such a web constitutes a stop element for the bushing part that is to be inserted, as a result of which the installation can only take place in a defined angular position or in a precise position. As an alternative, a projection or a groove can be created in the annular space, especially along the circumference or at the bottom, for purposes of an angle-oriented installation of the bushing.

If the recess in the material has the shape of ring segments or of an annular space, the one bushing or each bushing is advantageously arranged on an insert piece that has the shape of ring segments or of an annular space and that is inserted into the recess in the material. In this variant, especially all of the bushings are combined on a single insert piece that, for installation purposes, is then inserted into the recess in the material, if applicable, stopping against the above-mentioned web. In this context, especially the bottom of the rotor constitutes an axial stop element. The angle-oriented installation of the insert piece is prescribed by positive-fit elements or especially by a radial web.

In another advantageous embodiment, the insert piece comprises a number of axial projections so that, at its axial height, the insert piece that has been inserted is flush with the outer shell. As a result, in the installed state, it is ensured that the bushings arranged on the insert piece are situated on an axial plane together with the hydraulic-medium channels that are each to be connected. The insert piece is held by means of its axial projections between the covers of the camshaft phaser, especially between the bottom of the rotor and the locking cover of the stator. The axial projections can be located on one side of the insert piece. However, in the circumferential direction, the axial projections can also extend alternately to one axial side and then to the other axial side.

Advantageously, the one bushing or each bushing is arranged on an axial projection. As a result, a base of the insert piece that connects the bushings or the axial projections can be manufactured with as little material as possible so as to be very lightweight. If the hydraulic-medium channels for the early-adjustment and late-adjustment chambers are axially offset with respect to each other in the rotor, then preference is given to a variant in which the axial projections extend in the circumferential direction alternately to one axial side and then to the other axial side, whereby the bushings that supply the early-adjustment chambers are arranged in the one set of axial projections, whereas the bushings that supply the late-adjustment chambers are arranged in the other set of axial projections.

The insert piece can be made as a single part or else it can consist of several parts. In particular, the insert piece can be made of plastic by means of non-cutting methods. It can also be made of metal by means of non-cutting methods such as, for instance, a sintering method.

In one independently inventive embodiment, with an eye towards reducing the weight of a rotor of the above-mentioned type—which comprises a locking section with a hole to receive a movable locking bolt—the hole is created in such a way that it is open up to an axial wall section at the entrance of the hole, whereby a support element that serves as a counterbearing for the locking bolt is inserted into the open section opposite from the entrance to the hole.

This variant of a rotor can be implemented independently of the feature involving hydraulic-medium channels in the rotor. In this context, the invention is based on the consideration that, because of the mechanical locking function that has to be fulfilled vis-à-vis the stator, the locking section on the rotor is associated with a relatively large accumulation of mass since it calls for the use of more material. When the internal combustion engine is at a standstill, such a locking section allows the rotor to be locked in a defined angular position with respect to the stator. Consequently, when the internal combustion engine is started, even if the pressure generated in the hydraulic system is not yet sufficient, it is ensured that the rotor does not move in an uncontrolled manner and does not strike against the separating elements of the stator, which would cause undesired noises in the camshaft phaser.

The independent inventive solution is also based on the consideration that the relatively large accumulation of mass in the locking section causes a greater unbalance in the rotor. The greater the distance between the rotational axis and the locking section on the rotor, the greater the unbalance. An unbalance, however, detrimentally results in an undesired additional stress on the bearing, thus causing greater wear and tear on the camshaft phaser. Moreover, it is desirable to reduce the total weight of the rotor.

For purposes of achieving the objective, the invention surprisingly provides for the hole that holds the locking bolt to be left open to the greatest extent possible, so that only a relatively thin wall section remains at the entrance to the hole. The support and bearing functions for the locking bolt—which up until now had been fulfilled by the bottom of the hole, are now assumed by a support element located opposite from the entrance to the hole. This support element can be configured as a separate component and can be inserted into the open section. However, the support element can also be made as part of the rotor so that it is joined directly to the edge of the open section.

In a preferred embodiment, the support element is configured as a support crosspiece that has an axial arbor projection. Especially a mechanical restoring means, for instance, a helical spring or the like, can be placed onto this arbor projection. The guidance and counterbearing of the locking bolt are effectuated by the hole entrance and by the arbor projection on the support element. The configuration as a support crosspiece allows radial forces of the locking bolt to be absorbed and dissipated into the rotor.

In a particularly preferred embodiment, the open design of the locking section and the presence of a corresponding support element in a rotor are combined with a recess in the material that interrupts one or more hydraulic-medium channels, whereby, in each case, a bushing is inserted into the recess in the material in order to connect each of the interrupted hydraulic-medium channels.

In an especially preferred embodiment, the support element with the one bushing or with each bushing is arranged on a shared insert piece. This permits a very simple installation. Moreover, the support element—which is to be inserted into the open section of the hole—also allows an angle orientation of the bushings. In particular, the rotor can be manufactured with a closed annular space between the hub and the outer shell, which translates into a very substantial weight reduction. During installation, the appropriate insert piece—which comprises the bushings that connect the hydraulic-medium channels as well as the support element for a locking bolt that is to be subsequently inserted—is simply inserted into the annular space. The shared insert piece with the bushings and the support element can be manufactured without a mold. It can be made of plastic as well as of metal.

The second objective is achieved according to the invention by means of a camshaft phaser comprising a stator and a rotor of the above-mentioned type that can be rotated around a rotational axis relative to the stator. The advantages cited for the rotor and its refinements apply accordingly to the camshaft phaser.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention are explained in greater detail on the basis of a drawing. The following is shown in a perspective view:

FIG. 1 the rotor of a hydraulic camshaft phaser inserted into a stator, whereby the rotor has a ring-shaped recess in the material which has been created axially up to the locking section and which interrupts the hydraulic-medium channels;

FIG. 2 an insert piece that has been inserted into the recess in the material of the rotor according to FIG. 1, said insert piece having a number of bushings to connect the interrupted hydraulic-medium channels;

FIG. 3 the rotor according to FIG. 1, with an inserted insert piece according to FIG. 2;

FIG. 4 the underside of the rotor according to FIG. 1 or FIG. 3;

FIG. 5 another rotor for a hydraulic camshaft phaser, whereby an encircling ring-shaped recess that interrupts the hydraulic-medium channels has been axially created and this recess in the material also encompasses a locking section;

FIG. 6 an insert piece that has been inserted into the annular space of the rotor according to FIG. 5 and that has a number of bushings to connect the interrupted hydraulic-medium channels as well as a support element as a counterbearing for a locking bolt;

FIG. 7 the rotor according to FIG. 5, with an inserted insert piece according to FIG. 6; and

FIG. 8 the underside of the rotor according to FIG. 7, with an inserted insert piece.

DETAILED DESCRIPTION

FIG. 1 shows a camshaft phaser 1 comprising a rotor 2 and a stator 3. For the sake of clarity, the stator 3 is only partially shown. The rotor 2 is mounted so as to rotate around a rotational axis 4 relative to the stator 3. In order to be attached to a camshaft, the rotor 2 has a hub 5. The rotor 2 with its vane elements 7 on the outer shell 6 is inserted into the interior of the stator 3. Sealing elements 10 inserted into grooves 9 on the vane elements 7 then create a seal vis-à-vis the stator 3. The stator 3 is connected to the crankshaft of an internal combustion engine by means of a drive means (not shown in the drawing).

In order to lock the rotor 2 in a defined angular position with respect to the stator 3, for instance, during the start-up phase of the internal combustion engine, the rotor 2 also has a locking section 12 with a hole 14 into which a locking bolt can be inserted. In the appropriate angular position, the inserted locking bolt can engage into a recess of the stator 3, so that the rotor 2 and the stator 3 are mechanically bolted to each other.

The rotor 2 has a ring-shaped recess 16 in the material which has been created axially up to the locking section 12. The resultant annular space 18 can be clearly seen. In the area of the recess 16 in the material, the hub 5 and the outer shell 6 are each reduced down to an encircling collar having the wall thickness shown there. In other words, the entire rotor 2 is formed so as to be essentially pot-shaped and to enclose the inner hub 5. The locking section 12 interrupts the ring-shaped recess 16 in the form of a radial web 19.

A row of corresponding holes 20 can be seen on the hub 5 and on the outer shell 6, whereby these holes each belong to the first hydraulic-medium channels 24 and second hydraulic-medium channels 26. These hydraulic-medium channels 24 and 26 are interrupted by the corresponding recesses 16 in the material. The first hydraulic-medium channels 24 are arranged axially offset with respect to the second hydraulic-medium channels 26. The early-adjustment chambers 28 formed between the rotor 2 and the stator 3 are connected to a hydraulic pressure system via the hydraulic-medium channels 24, whereas the late-adjustment chambers 30 are connected to a hydraulic pressure system via the second hydraulic-medium channels 26. The individual hydraulic-medium channels 24, 26 are flow-connected in the interior of the hub 5 in that they are coupled to axial supply spaces in the camshaft, or else in that they are directly coupled to the inlet or outlet of a central valve installed in the camshaft. For purposes of forming the early-adjustment and late-adjustment chambers 28, 30, respectively, in each case a vane element 6 engages between two adjacent separating elements 31 of the stator 3.

Owing to the approximately ring-shaped axial recess 16 created in the material, the weight of the rotor 2 is markedly reduced in comparison to prior-art embodiments. In order to re-establish the connection of the early-adjustment and late-adjustment chambers 28, 30, respectively, to the hydraulic pressure system, bushings 47 (see FIG. 2) are inserted between the corresponding holes 20 in the hub 5 and outer shell 6.

For purposes of facilitating the installation, the bushings 47 shown in FIG. 2 are arranged on a shared insert piece 40. The insert piece 40 has a base 42 in the form of an open ring. First axial projections 44 and second axial projections 45 that extend alternately to one axial side and then to the other axial side are arranged in the circumferential direction on the base 42. The bushings 47 each pass through the axial projections 44 and 45. The axial gap 48 is visible on the open ring of the base 42. At the same time, a stop element 49 is defined on the base 42 by the axial gap 48. When the insert piece 40 is in the installed state, it is in contact via this stop element 49 with the radial web 19 of the rotor 2 shown in FIG. 1. As a result, a defined angular position of the insert piece 40 on the rotor 2 is prescribed, so that there is no need for a laborious adjustment and inspection of the installed position during the installation process.

In FIG. 3, the rotor 2 shown in FIG. 1 is depicted with the inserted insert piece 40 shown in FIG. 2. It can be seen how, since the insert piece 40 has been inserted, the hydraulic-medium channels 24, 26 that are interrupted by the recess 16 in the material are once again individually flow-connected to each other via the bushings 47. The axial installation position of the insert piece 40 results from the fact that the first axial projection 44 stops against the bottom of the rotor 2. Via the second axial projections 45, the axial height of the insert piece 40 is flush with the axial height of the outer shell 6. In the installed state, a locking cover axially encloses the rotor 2 and thus the insert piece 40 in the stator 3. The angular position of the insert piece 40 is defined by the stop element 49 as it stops against the locking section 12.

In an embodiment given by way of an example, the inner diameter of the bushings 47 is selected so as to be greater than the diameter of the holes 20. This results in a reliable flow-coupling, even if the bushings 47 are not oriented ideally when it comes to their being flush with the holes 20.

In the installed state shown in FIG. 3, it can also be seen that the bushings 47 of the second axial projections 45 are axially offset with respect to the bushings 47 of the first axial projections 44 and thus they each form the first hydraulic-medium channels 24 and second hydraulic-medium channels 26, respectively, and they also connect the corresponding holes 20. In this context, the bushings 47 are inserted by means of a radial press fit into the annular space 16 between the hub 5 and the outer shell 6, which corresponds to an axial press fit in the direction of the holes 20 or of the hydraulic-medium channels 24, 26. The resultant sealing functionality meets the criteria required for a hydraulic camshaft phaser 1.

In FIG. 4, the rotor 2 shown in FIG. 2 or 3 is depicted from a different perspective view towards the bottom 50. The holes 20 for the first and second hydraulic-medium channels 24, 26, respectively, are visible in the interior of the hub 5 and on the outer shell 6.

FIG. 5 shows a rotor 2 according to an alternative variant. In comparison to the rotor 2 shown in FIG. 1, in FIG. 5, the locking section 12 is additionally open up to a wall section 52 in which the locking hole 14 has been made. Consequently, the axial recess 16 created in the material between the hub 5 and the outer shell 6 is altogether ring-shaped.

FIG. 6 shows an appertaining insert piece 40 that is inserted into the annular space 18 of the rotor 2 shown in FIG. 5. In addition to the already described bushings 47 which, in turn, are arranged on corresponding axial shoulders 44, 45, the ring-shaped base 42 of the insert piece 40 shown in FIG. 6 now comprises a support element 54 in the form of a support crosspiece 55. In the hole section 12 of the rotor 2, in conjunction with the wall section 52, this support element 54 takes on the function of a blind hole in which a locking bolt is guided and supported in the manner of a counterbearing. The resulting elimination of material translates into an additional weight reduction for the rotor 2 shown in FIG. 5. In particular, the unbalance caused by the locking section 12 is diminished.

The support element 54 also comprises an axial arbor projection 57. In the installed state, a helical spring is mounted on this arbor projection 57, said helical spring serving to pre-tension the inserted locking bolt against the locking cover. The configuration as a support crosspiece 55 allows the arbor projection 57 to absorb not only axial forces but also radial forces (relative to the direction of movement of the locking bolt) and to dissipate these forces into the rotor 5.

In FIG. 7, the rotor 2 shown in FIG. 5 is depicted with the inserted insert piece 40 shown in FIG. 6. The angular orientation of the insert piece 40 relative to the rotor 2 is prescribed in a defined manner in that the arbor projection 57 is inserted into the hole 14 in the locking section 12.

FIG. 8 depicts the rotor 2 shown in FIG. 7 from a perspective view towards the bottom 50. In this perspective, it can be seen how the arbor projection 57 is inserted opposite from the hole entrance 58. The arbor projection 57 of the support element 54 assumes the function of a cartridge that has been normally used up until now in which the locking bolt is mounted so as to be pre-tensioned by means of a spring.

LIST OF REFERENCE NUMERALS

1 camshaft phaser

2 rotor

3 stator

4 rotational axis

5 hub

6 outer shell

7 vane element

9 groove

10 sealing element

12 locking section

14 hole

16 recess in the material

18 annular space

19 web

20 holes

24 first hydraulic-medium channel

26 second hydraulic-medium channel

28 early-adjustment chamber

30 late-adjustment chamber

31 separating element

40 insert piece

42 base

44 first axial projections

45 second axial projections

47 bushing

48 axial gap

49 stop element

50 bottom

52 wall section

54 support element

55 support crosspiece

57 arbor projection

58 hole entrance

ROTOR FOR A HYDRAULIC CAMSHAFT PHASER

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CPC

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