Cam phaser

Abstract

A cam phaser including a stator that is driven by a crank shaft of an internal combustion engine; and a rotor that is connectable torque proof with a cam shaft of the internal combustion engine and that includes plural blades that protrude radially outward from a rotor hub, wherein operating chambers arranged between the stator and the rotor are divided into pressure cavities by the blades, wherein the stator and the rotor are configured as sintered components, wherein displacement recesses are provided on axially configured faces of the stator and/or of the rotor wherein material is configured to flow into the displacement recesses during a deforming finishing of the faces.

Claims

1. A cam phaser, comprising: a stator that is driven by a crank shaft of an internal combustion engine; and a rotor that is connectable torque proof with a cam shaft of the internal combustion engine and that includes plural blades that protrude radially outward from a rotor hub, wherein operating chambers arranged between the stator and the rotor are divided into pressure cavities by the blades, wherein the stator and the rotor are configured as sintered components, wherein displacement recesses are provided on axially configured faces of the stator or the rotor wherein material is configured to flow into the displacement recesses during a deforming finishing of the axially configured faces.

2. The cam phaser according to claim 1, wherein the axially configured faces are finishable by height calibration.

3. The cam phaser according to claim 2, wherein the displacement recesses are substantially evenly distributed on the axially configured faces.

4. The cam phaser according to claim 2, wherein the displacement recesses are configured three dimensional facet shaped and respectively include a base surface and essentially trapezoid side surfaces so that circumferential bar structures envelop the displacement recesses.

5. The cam phaser according to claim 4, wherein the circumferential bar structures form a calibration structure.

6. The cam phaser according to claim 5, wherein the displacement recesses are arranged on the axially configured faces so that at least a portion of the bar structures forms a continuous structure which defines the axially configured faces circumferentially.

7. The cam phaser according to claim 5, wherein the calibration structure includes a surface portion that is adapted to a size of the sintered components.

8. The cam phaser according to claim 5, wherein an inclination angle of the trapezoid side surfaces is adapted to the surface portion of the calibration structure.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further advantages can be derived from the dependent patent claims, the description and the drawing figure, wherein:

(2) FIG. 1 illustrates a stator and a rotor of a known cam phaser in a perspective view;

(3) FIG. 2 illustrates a rotor of the cam phaser according to the invention in a perspective view;

(4) FIG. 3 illustrates a blade of the rotor according to FIG. 2 in a partial sectional view and in a perspective view;

(5) FIG. 4 illustrates a top view of the blade according to FIG. 3;

(6) FIG. 5 illustrates a stator of a cam phaser according to the invention in a perspective view;

(7) FIG. 6 illustrates an enlarged partial view of the stator according to FIG. 5; and

(8) FIG. 7 illustrates a stator according to another embodiment of the cam phaser according to the invention in a perspective view.

DETAILED DESCRIPTION OF THE INVENTION

(9) FIG. 1 illustrates a known cam phaser 1 configured to adjust an angular relationship between a crank shaft and a cam shaft during operations of an internal combustion engine. A relative rotation of the non-illustrated cam shaft adjusts opening and closing timing of the gas control valves so that the internal combustion engine delivers optimum power at a respective speed. The cam phaser 1 thus facilitates a continuously variable adjustment of the cam shaft relative to the crank shaft.

(10) The cam phaser 1 includes a cylindrical stator 2 which is connected torque proof with a gear 3. In the embodiment the gear 3 is a sprocket over which a chain is run that is not illustrated in detail. The gear 3, however, can also be a timing belt cog over which a drive belt is run that forms the drive element. The stator 2 is operatively connected with the crank shaft through the drive element and the gear 3 in a known manner.

(11) In this embodiment the stator 2 and the gear 3 are integrally configured in one piece. Bolts clamp a non-illustrated stator cover against a unit formed by the stator 2 and the gear 3. When the stator 2 and the gear 3 are separate components in an alternative embodiment the stator 2 is clamped by bolts between the gear 3 and a stator cover.

(12) The stator 2 is provided with radially inward protruding bars 5. Blades 6 of a rotor 4 are arranged circumferentially between the bars 5. The rotor 4 includes a rotor hub 7 which is connected torque proof with the cam shaft. Thus, the rotor hub 7 is shrunk or pressed onto a cam shaft end. In order to adjust the angular relationship between the cam shaft and the crank shaft the rotor 4 is rotated relative to the stator 2 against the force of a spiral spring. Thus, depending on the intended direction of rotation the hydraulic fluid is pressurized in pressure chambers 8 that are associated with a first direction of rotation whereas the pressure chambers 9 associated with a second direction of rotation are unloaded towards the tank. The pressure chambers 9 associated with the other direction of rotation are illustrated in the drawing figure in their minimum condition.

(13) In order for the rotor 4 to take an early outlet cam shaft position that is required for engine start when the internal combustion engine is turned off, this means when the cam phaser 1 is unloaded the rotor 4 is rotated by the spiral spring into a starting position. In this starting position the rotor 4 is fixed against pivoting relative to the stator 2 by a locking device 10. The locking device is arranged in one of the blades 6. Thus, during a pressure drop in the pressure cavities 8, 9 a non-illustrated locking bolt is moved by the spring force of a compression coil spring that is not illustrated in more detail into a locking position in which the locking bolt engages a locking opening of the non-illustrated stator cover. Upon engine start up the locking bolt is loaded by the hydraulic fluid against the spring force and pushed back so that the rotor 4 is unlocked from the stator cover and the cam phaser 1 can move into its control position.

(14) The pressure chambers 8, 9 can be supplied with hydraulic fluid through transversal bore holes 11, 12 or the hydraulic fluid can be drained from the pressure chambers. Thus, a hydraulic valve is provided coaxially arranged within the cam shaft wherein the hydraulic valve includes at least one hydraulic piston.

(15) The stator 2 and the rotor 4 of the cam phaser 1 are typically made from a steel or aluminum alloy and produced by a sintering method. In order to provide a correct function of the cam phaser 1 the process steps pressing, coarse machining and sintering are followed by rather complex finishing methods including calibrating, grinding, fine turning etc. in order to assure a required parallel alignment of axially opposed surfaces. These finishing processes are expensive and bear quality risks which are even increased by intermediate handling steps.

(16) In order to provide a cam phaser 1 where a precision of the sintered components required for functionality can be achieved with significantly reduced finishing complexity while maintaining a cost effective manufacture the cam phaser 1 according to the invention includes displacement recesses 14 on axially configured faces of the stator and/or the rotor 4.

(17) FIG. 2 illustrates a rotor 4 of a first embodiment of a cam phaser 1 according to the invention. Faces 13, 15 which contact an inner surface of the stator 2 after assembling the cam phaser 1 include displacement recesses 14 into which the material of the rotor 4 can flow during a deforming finishing process of the faces 13, 15. The finishing is advantageously performed by height calibration during which the height of the respective component and the parallel orientation of two opposite surfaces can be provided in a simpler and more cost effective manner through an intentional plastic deformation of the sintered material using a forming tool.

(18) During pressing of the blanks defined recesses are introduced in the form of recesses or grooves which provide the displacement space that is required for the finishing through deformation that is necessary after the sintering without impairing a load bearing capability of the finished faces 13, 15 so that sustainable surface pressures are exceeded during operations.

(19) Since the displacement recesses 14 are essentially evenly distributed on the axial faces 13, 15 it is possible to avoid an impairment of the load bearing capability of the faces 13, 15 so that a predetermined surface pressure is not exceeded during operations of the cam phaser 1.

(20) As evident in particular from FIGS. 3 and 4 which illustrate blown up details of a blade 6 the displacement recesses 14 are configured three dimensional facet shaped and respectively include a base surface 16 and essentially trapezoid side surfaces 17 so that a respective circumferential bar structure 18 envelops the displacement recesses 14. Thus, adjacent displacement recesses 14 transition into the same bar structure 18. The bar structures 18 essentially have an identical width over the faces 13, 15. The entirety of the bar structures 18 forms a calibration structure which includes a surface portion that is adapted to the size of the component. Thus, an additional deformation and thus an unintentional height reduction of the components during operations can be prevented. Thus, the surface portion is defined so that the required displacement space is provided and a desired sealing can be simultaneously provided.

(21) The surface ratios between the displacement recesses and the calibration structure substantially contributes to the degree of deformation achieved and thus the precision with respect to obtaining a particular height dimension. Since height calibration loads the opposite surfaces with a pressing force and a counter acting support force a substantial amount of elastic deformation is achieved in addition to the intended plastic deformation wherein the elastic deformation leads to a spring back of the deformed material portions during unloading of the component. This elastic portion has to be kept small since it is a parameter that is difficult to control during subsequent clamping of the component in the cam phaser 1 and can thus have negative consequences for the cam phaser. However, since the elastic deformation portion during calibration cannot be completely avoided with these fabrication methods the elastic deformation portion is brought to a low and manageable level by a suitable configuration of the surface structure according to the invention. This is achieved by the shaping of the displacement recesses 14 with the side surfaces 17 as a transition to the bar structures 18 described supra. Additional shape configuration can be provided by radii, etc.

(22) In order to keep the elastic portion as small as possible the inclination angle of the trapezoid side surfaces 17 is adapted to the surface portion of the bar structures 18. As a matter of principle it has become apparent that transitions between protruding and recessed portions have to be steeper for a decreasing portion of recessed surfaces, i.e. displacement recesses 14 and vice versa.

(23) Furthermore it is in particular evident from FIG. 2 that the displacement recesses 14 and the bar structures 18 are arranged on the faces 13, 15 so that a portion of the bar structures 18 forms a continuous structure which circumferentially defines the faces 13, 15. This circumferential structure facilitates safe sealing of the faces 13, 15 when they contact the inner surface of the stator 2 so that leakage can be significantly reduced. This portion of the bar structures 18 can be configured wider than the inner bar structures 18 in order to improve the sealing.

(24) FIGS. 5 and 6 illustrate a stator 2 according to the first embodiment which is integrally configured with a gear 3 according to FIG. 1. As already described with respect to the rotor 4 also the stator 2 includes the displacement recesses 14 described supra at its faces 19, 20. Reference is made to the descriptions provided supra.

(25) FIG. 7 illustrates a stator 2 according to another embodiment wherein a timing belt cog or a belt pulley is attachable at the stator 2 torque proof.

(26) The described calibration structure with the displacement recesses 14 can be provided according to the invention at the rotor 4 or at the stator 2 or at both components, however it is used in particular advantageously at the faces 19, 20 of the stator 2. Thus, it has to be considered when configuring the calibration structure that the maximum sustainable surface pressures do not have to be exceeded in an assembled condition as well as under any operating condition in order to be able to receive the axial clamping forces reliably and permanently without the clamping interconnection settling. The operating conditions thus include in particular high temperatures where the creeping resistance of the materials deteriorates and axial and in particular radial mechanical forces can impart additional axial force components upon the surface that is structured according to the invention.

(27) It is also very important for the subsequent function of the components 2, 4 of the cam phaser 1 produced according to the invention that the axially opposed surfaces have the tightest tolerances with respect to parallel orientation. Thus it is even more important to precisely determine when configuring the calibration structure according to the invention on both faces 13, 15 or 19, 20 which deformation portions of a plastic nature or an elastic nature are to be expected and thus also to consider the force impact and the process impacts during calibration.

(28) Other advantages of the calibration structure according to the invention are achieved in that the height calibrated faces 13, 15 or 19, 20 can be configured with a predetermined global topology which e.g. facilitates the deformation of a rotor 4 that is being clamped onto the cam shaft end and which can contribute to an additional functional improvement while simultaneously reducing productions cost.

REFERENCE NUMERALS AND DESIGNATIONS

(29) 1 cam phaser 2 stator 3 gear 4 rotor 5 bar 6 blade 7 rotor hub 8 pressure chamber 9 pressure chamber 10 locking device 11 transversal bore hole 12 transversal bore hole 13 face 14 displacement recess 15 face 16 base surface 17 side surface 18 bar structure 19 face 20 face