ROTOR FOR A CAMSHAFT PHASER, AND CAMSHAFT PHASER

The present invention relates to a rotor for a camshaft phaser, including a hub part having an oil supply passage, at least one vane radially disposed on the hub part, as well as oil channels extending through the hub part and fluidically connected to the oil supply passage. The present invention further relates to a camshaft phaser for adjusting the phase angle of a camshaft with respect to a crankshaft of an engine, the camshaft phaser having such a rotor.

BACKGROUND

In internal combustion engines, in particular, gasoline-powered automotive engines, camshafts are used to actuate the so-called gas-exchange valves. The cams of the camshaft normally bear against cam followers, such as bucket tappets, finger followers or cam levers. When a camshaft is set in rotation, the cams act on the cam followers, which in turn actuate the gas exchange valves. Thus, the position and shape of the cams determine both the opening duration and the opening amplitude, as well as the opening and closing points of the gas exchange valves.

Shifting the angular position of the camshaft relative to a crankshaft in order to optimize the valve timing for different speed and load conditions is referred to as camshaft phasing. For example, one design variant of a camshaft phaser operates according to what is known as the swing motor principle. Here, a stator and a rotor are provided which are arranged coaxially with respect to each other and are movable relative to one another. The stator and the rotor together form hydraulic chambers, referred to here simply as chambers. Each chamber pair is delimited by webs of the stator and is divided by a respective vane of the rotor into two oppositely acting chambers, the volumes of which are oppositely varied by rotational movement of the rotor relative to the stator. In the maximum adjusting position, the respective vane bears against one of the boundary webs of the stator. The relative rotational movement of the rotor is accomplished by displacement of the vane. To this end, a hydraulic medium, such as oil, is introduced through channels into the chambers and urges the vane away. Displacement of the rotor causes the camshaft attached to the rotor to be phase-shifted, for example, in the advance direction, i.e. towards an earlier opening point of the gas exchange valves. Displacement of the rotor in the opposite direction causes the camshaft to be phase-shifted relative to the crankshaft in the retard direction, i.e. towards a later opening point of the gas exchange valves. In such processes, the hydraulic medium is conducted from a central oil supply passage into the respective chambers via oil channels arranged on both sides of the respective vanes.

German Patent Application No. DE 10 2007 020 527 A1 describes a rotor which is adapted to serve as a driven member. The inner rotor is non-rotatably connected to a camshaft. An outer rotor constitutes a driving member and has five hollows or chambers spaced apart in the circumferential direction; one vane of the inner rotor extending into each of said hollows. The hollows are delimited in the axial direction by two side covers. In this way, each of the hollows is sealed pressure-tight.

A particular complex and correspondingly expensive step in the manufacture of a rotor is the formation of the oil channels. Generally, the oil channels are bores made in the material of the rotor. In a rotor in the form of a sintered body, the oil channels are formed in the green body in a separate manufacturing step.

SUMMARY OF THE INVENTION

It is an object of the present invention to simplify the manufacture of a rotor.

The present invention provides a rotor for a camshaft phaser, including a hub part having an oil supply passage, in particular a central oil supply passage, at least one vane radially disposed on the hub part, as well as oil channels extending through the hub part and fluidically connected to the oil supply passage. The rotor includes a main body and at least one cover element arranged on an end face of the main body. The oil channels are axially closed by the cover element and, in particular, are formed by the cover element. The oil channels extend substantially radially between the central oil supply passage and an outer periphery of the rotor.

Furthermore, the above object is achieved by a camshaft phaser for adjusting the phase angle of a camshaft with respect to a crankshaft of an engine, the camshaft phaser including such a rotor in accordance with one of the embodiments described above. The advantages and preferred embodiments described below with reference to the rotor apply equally to the camshaft phaser.

The oil channels in the hub part of the rotor are axially closed by the cover element. This makes it much easier to produce the oil channels, which in particular are formed as groove-like recesses in the surface of the main body and/or in the surface of the cover element. It is only when the cover element is attached and secured to the main body that the oil channels are axially closed and disposed inside the rotor. This way of producing the oil channels is associated with a low level of technical complexity and does not require subsequent machining of the oil channels. In particular, no additional manufacturing step is needed to form bores in the material of the rotor.

Since the rotor is made up of several parts, there is greater freedom in the design of each of the parts, in particular with regard to the formation of spaces within the rotor at the junction between the rotor and the cover element. Such spaces are easily formed in various geometric shapes and sizes by assembling the individual parts. Moreover, owing to the multi-part rotor design, the main body and the cover element have a relatively small volume. Due to the split design, the rotor can be given complex geometries in a simple manner by correspondingly shaping the individual parts of the main body and without additional subsequent machining.

The main body and the cover member have, in particular, different geometries. The rotor is configured such that the main loads of attachments, such as the preload force of a central bolt of a central valve, the adjusting torque, the return spring torque, and the load of a locking device, are carried directly by the fatigue-resistant main body without placing any load on the cover element. Therefore, preferably, the forces exerted by such attachments are introduced solely into the main body. The main body has a thickness equal to a minimum thickness necessary to accommodate the preload force of the central bolt. For an overall rotor thickness of, for example, between 16 mm and 30 mm, the thickness of the main body is in particular about 4 to 10 mm. The remaining thickness of the rotor is defined by the at least one cover element.

The main body essentially forms the hub part of the rotor. In addition, it preferably includes the vanes, a locking bore, and at least portions of supporting surfaces for axial and radial bearings. The main body is in particular configured to be attached to the camshaft in a single additional operation by a friction fit, a form fit, or a material-to-material bond, for example, by brazing or welding.

The cover element forms a wall on an end face of the rotor, and serves in particular to provide sealing surfaces in order to reduce leakage. In contrast to a side cover, the cover element is in particular only connected to the main body, but not to the outer stator.

In accordance with a preferred embodiment, the main body and the cover element are made from different materials. The main body, which bears the forces that act on the rotor, is made from a hard and wear-resistant material. The cover element is in particular made from a lighter material than the main body, thereby reducing the weight of the rotor.

In accordance with another preferred embodiment, two cover elements are provided on the main body on the two sides thereof. As a result, the rotor has a symmetrical design, where one cover element is provided on each end face of the main body. Thus, two rows of oil channels can be easily formed in the axial direction, the oil channels extending along the junctions between the main body and the respective cover element.

The two cover elements may be either identical or different in design. Preferably, the two cover elements are identical in design. Since the two cover elements are configured substantially identically, their design is particularly convenient from a manufacturing point of view, because both cover elements may be manufactured using the same implement.

The cover element is preferably made of plastic. Plastic is a material which is lightweight and, in addition, particularly easy to shape. The use of plastic as the shell material for the main body makes it possible to significantly reduce the weight of the rotor, for example, from about 250 g to about 150 g. Alternatively, the cover elements are made from a light metal or from a non-metallic material.

In a preferred variant, the cover element is injection-molded onto the main body. Thermosetting plastic is an example of a material that is suitable for this use. In this case, the oil channels are formed using slides which extend between the main body and the molding material for the cover elements and which are removed radially after said injection-molding process is complete.

In an alternative preferred variant, the cover element is a separate component attached to the main body. In this case, the connection between the main body and the cover element is accomplished by a friction fit, a form fit, or a material-to-material bond, and is in particular permanent, so that in the assembled state, the rotor is one piece and is inserted as such in the camshaft phaser.

The main body is preferably made from a metal. Depending on the demands on the connection to the camshaft, the materials used for the main body are, for example, steel or sintered steel, as well as light metals, such as aluminum or sintered aluminum.

Expediently, the main body is a sintered body. Besides sintering, other manufacturing methods may be used to produce the main body. Examples of such methods include forming, separating, filling or punching and stacking processes.

In accordance with a preferred embodiment, the main body is provided with first recesses for the oil channels. If the main body is a sintered body, then initially a green body or compact of compressed powder, in particular metal powder, is produced and the first recesses for the oil channels are formed in the desired cross-sectional shape and size in the end-face surface of the main body. Subsequently, the green body is sintered.

Alternatively or in addition to the first recesses, in another preferred embodiment, second recesses for the oil channels are provided in the cover element. Regardless of whether only the first or only the second recesses are provided, or whether the first and second recesses are provided on the main body and on the cover element, the recesses are arranged and dimensioned such that when the rotor is in the assembled state, the oil channels are axially closed on one side by the cover element and on the other side by the main body.

The first and/or the second recesses are preferably rectangular in cross section, so that the oil channels are also rectangular. Therefore, the oil channels have an oblong cross-sectional area. The advantage of a rectangular oil channel cross section over a circular one is that the oil channels can be made wider, in particular in the circumferential direction. Therefore, in comparison to bores having the same, in particular axial depth (diameter of the bore), the cross-sectional area can be increased, thereby reducing the pressure drop in the oil channels. In this case, the rate of oil flow to the chambers is higher, so that the hydraulics for actuating the rotor are overall faster and more flexible. Alternatively, the recesses are circular in configuration or have a different geometric shape.

Advantageously, the main body is provided with cavities which serve in particular to reduce the weight of the rotor. This, on the one hand, avoids an excessive moment of inertia and, on the other hand, reduces the amount of material required to manufacture the rotor. The cavities are preferably formed as closed cavities within the rotor. The cavities are axially sealed by the cover element, as are the oil channels. However, in contrast to the oil channels, they are not radially open, but closed in all directions when the rotor is in the assembled state. The area of the cavities is expediently about ⅓ to ⅔ of the area of the hub part between two vanes. In a preferred variant, the cavities are formed as depressions in the surface of the main body. In an alternative preferred variant, the cavities are apertures in the material of the main body, said apertures extending along the entire axial length of the main body and being closed on both sides by a cover element.

Preferably, the main body has ribs extending from its end faces and forming axial supporting surfaces when the rotor is in the assembled state. Therefore, said ribs preferably terminate substantially flush with the cover element. The term “flush”, as used herein, is intended to mean that the cover element and the axial rib surface forming the supporting surface are in the same plane, or that the cover element is slightly lower, for example, up to 50 μm lower, than the ribs. Here, the ribs form thrust bearings via which the rotor bears against the side cover. Since the points of contact between the rotor and the side cover and between the rotor and the stator are highly stressed, such critical functional surfaces are manufactured from the more wear-resistant material of the main body. In order to ensure long-term, trouble-free operation of the rotor, the radially outer regions of the vanes are preferably also formed of the material of the main body. Thus, the cover element covers the end face of the main body only partially. The cover element may, for example, be configured such that it extends only across the hub part and does not, or only partially, cover the vanes. However, the cover element always covers the regions which are to be axially sealed or which have a sealing function (e.g., toward the side covers) and therefore need a suitable sliding layer that is sealed by the cover elements. Therefore, this end-face surface forms a sealing surface.

BRIEF DESCRIPTION OF THE DRAWINGS

An exemplary embodiment of the present invention is explained in more detail with reference to the drawings, in which:

FIG. 1 shows a longitudinal sectional view through a camshaft phaser;

FIG. 2 shows a perspective view of a rotor;

FIG. 3 shows a first side of a main body for the rotor of FIG. 2;

FIG. 4 shows the main body of FIG. 3 in side view;

FIG. 5 shows a second rotor side opposite the first side shown in FIG. 3;

FIG. 6 shows the main body of FIGS. 3 through 5 in perspective view;

FIG. 7 shows an outer face of a cover element for a rotor according to FIG. 2;

FIG. 8 shows a side view of two assembled cover elements according to FIG. 7;

FIG. 9 shows an inner face of the cover element of FIG. 7;

FIG. 10 shows a perspective view of two cover elements in a first orientation; and

FIG. 11 shows the two cover elements of FIG. 10 in a second orientation.

Like or functionally equivalent parts are identified by the same reference numerals in all figures.

DETAILED DESCRIPTION

FIG. 1 shows, in longitudinal cross section, a hydraulic camshaft phaser 2 for adjusting the phase angle of a camshaft 3. Sectional plane A-A of FIG. 1 is shown in FIG. 2. Camshaft phaser 2 includes an outer stator 4 and an inner rotor 6 arranged concentrically and rotatably therein. Rotor 6 is connected to camshaft 3 by a central bolt 7. Formed between stator 4 and rotor 6 are chambers (not specifically shown) which are closed in the axial direction by two side covers 8a, 8b and delimited in the circumferential direction by radial webs 9 of stator 4. The two side covers 8a, 8b are non-rotatably connected to stator 4 by screws 11.

Rotor 6 includes a hub part 10 having a central circular oil supply passage 12 (see FIG. 2). Oil supply passage 12 is concentric with an axis of rotation D of rotor 6. Central bolt 7 extends through oil supply passage 12. A hydraulic medium, in particular oil, is introduced through oil supply passage 12 and passed from rotor 6 to the chambers through radially extending oil channels 14. As can be seen in FIG. 2, hub part 10 is provided with radially extending equally spaced vanes 16. Each of vanes 16 is rotatably disposed in one of the chambers. Vane 16 divides the chamber into two oppositely acting sub-chambers (not specifically shown). In order to change the position of vane 16, and thus of rotor 6, relative to stator 4, oil is introduced into one of the oppositely acting chambers.

Oil channels 14 each have an inlet 14a fluidically connected to central oil supply passage 12. An outlet 14b is disposed at the periphery in the region of a vane 16. When camshaft phaser 2 is in the assembled state, oil channels 14 each open via their outlets 14b into respective ones of the oppositely acting sub-chambers between stator 4 and rotor 6. An oil channel 14 is provided on both sides of vane 16. The two oil channels 14 near a vane 16 are axially offset with respect to each other.

In the exemplary embodiment shown in FIG. 2, rotor 6 is made up of a main body 18 and two cover elements 20. Cover elements 20 are arranged on the end faces of main body 18 such that they axially close oil channels 14. Thus, oil channels 14 extend along the junction between the main body 18 and the respective cover element 20. Here, oil channels 14 are rectangular in cross section. Alternatively, the cross section of oil channels 14 is circular. However, the rectangular cross section has the advantage that they can be made larger and, therefore, more oil is conveyed through oil channels 14 per unit of time.

Main body 18 and cover element 20 are formed from different materials. In the exemplary embodiment shown, main body 18 is a sintered metal body and cover elements 20 are plastic parts.

Here, cover elements 20 are separate components which are manufactured separately from main body 18 and suitably attached to main body 18 in a later manufacturing step.

Alternatively, cover elements 20 maybe formed by injection-molding plastic, in particular, thermosetting plastic, over main body 18. During this injection-molding process, slides are arranged between main body 18 and the later cover elements 20, said slides being subsequently radially removed, so that oil channels 14 are formed in their place.

The design of main body 18 is illustrated in FIGS. 3 through 6. In this exemplary embodiment, main body 18 includes both hub part 10 and vanes 16. In order to reduce the weight of rotor 6, hub part 10 is provided with cavities 22 that are formed as axial apertures in the material of main body 18. Cavities 22 are trapezoidal in cross section and axially closed by cover elements 27 when rotor 6 is in the assembled state.

In the region of main body 18, oil channels 14 are defined by first recesses 24 in the material of main body 18. At a first end face 21a of main body 18, first recesses 24 are rectangular in shape. At an opposite second end face 21b, recesses 24 are semicircular in cross section.

Furthermore, main body 18 has ribs 26 which extend from its end faces in the region of vanes 16 and are flush with the respective cover elements 20 when rotor 6 is in the assembled state, as can be seen in FIG. 2. Ribs 26 serve as thrust bearings to bear against side covers 8a, 8b. As a result of their contact with side covers 8a, 8b, the ribs are exposed to high torsional force during rotation of rotor 6 relative to stator 4. Alternatively, since cover elements 20 are more susceptible to wear, ribs 26 are somewhat higher, in particular about 50 μm higher, than cover elements 20 to prevent forces from being transmitted from side covers 8a, 8b to cover elements 20.

FIGS. 7 through 11 illustrate the configuration of cover elements 20, such as are used in rotor 6. Main body 18 has been omitted for the sake of clarity. As can be seen from FIG. 7, each cover element 20 has a substantially flat outer face 28a. Cover elements 20 cover the end faces of main body 18 only partially; i.e., the surface or rotor 6 includes both elements of plastic and elements of metal. In the region of vanes 16, cover elements 20 are formed with radially projecting collar elements 30, which partially surround ribs 26 in the circumferential direction when cover elements 20 rest on main body 18. Collar elements 30 form an oblong slot 32 for receiving rib 26.

In inner face 28b of cover elements 20, which is shown in FIG. 9, is provided with second recesses 34 corresponding to first recesses 24 on main body 18, so that the first and second recesses 24, 34 form oil channels 14 when cover elements 20 are attached to main body 18. If necessary, outer faces 28a of cover elements 20 may also be provided with similar recesses to form channels. Inner faces 28b of cover elements 20 are further provided with substantially trapezoidal depressions 36. The position and shape of depressions 36 correspond to those of apertures 22 in main body 18, so that depressions 36 complement cavities 22 at the end faces.

In a first manufacturing step, main body 18 is formed from a sinter material in a sintering process. In the process, weight-reducing cavities 22 and first recesses 24 are incorporated into main body 18. In a second manufacturing step, cover elements 20 are manufactured and applied to main body 18. This may be done in two ways. In a first variant, cover elements 20 are manufactured as separate components in a separate manufacturing step and attached to main body 18 by a friction fit, a form fit, or a material-to-material bond. Alternatively, cover elements 20 is injection-molded onto main body 18. After cover elements 20 are attached to main body 18, both the cavities 22 and the oil channels 14 are enclosed within rotor 6, without the need for subsequent machining of rotor 6, for example, to form bores.

A rotor 6 designed in this way is particularly suited for use as an inner rotor for camshaft phaser 2, but is not limited to such use. Rather, such a rotor may also be used, for example, in pumps or in other similar applications.

LIST OF REFERENCE NUMERALS

2 camshaft phaser

3 camshaft

4 outer stator

6 inner rotor

7 central bolt

8
a side cover

8
b side cover

9 web

10 hub part

11 screw

12 oil supply passage

14 oil channel

14
a inlet

14
b outlet

16 vane

18 main body

20 cover element

21
a first end face

21
b second end face

22 cavity

24 first recess

26 rib

28
a outer face of the cover element

28
b inner face of the cover element

30 collar element

32 slot

34 second recess

36 depression

A-A sectional plane

D axis of rotation

ROTOR FOR A CAMSHAFT PHASER, AND CAMSHAFT PHASER

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