Piston for a hydraulic unit of a cam phaser and cam phaser

Abstract

A piston for a hydraulic unit of a cam phaser, wherein the piston is configured cylindrical and wherein the piston is received axially movable in a cam phaser opening of the cam phaser, wherein according to a positioning of the piston a plurality of connections, in particular operating connections of the cam phaser are opened and closed, wherein the piston includes an outer contour that is configured for opening or closing the connections wherein the outer contour is configured complementary to an inner contour of the cam phaser opening in order to provide opening and/or closing of the connections. The invention also relates to a cam phaser.

Claims

1. A piston for a hydraulic unit of a cam phaser, wherein the piston is configured cylindrical and wherein the piston is configured to move axially within a cam phaser opening of the cam phaser, wherein a plurality of operating connections of the cam phaser are opened and closed according to a positioning of the piston, wherein the piston includes an outer contour that is configured for opening or closing the plurality of operating connections wherein the outer contour is configured complementary to an inner contour of the cam phaser opening in order to provide opening or closing of the plurality of operating connections, wherein the cam phaser opening is formed by an inner surface of a rotor of the cam phaser and the rotor including rotor blades is integrally formed from one piece of material, and wherein the piston slides directly on the inner surface of the rotor.

2. The piston according to claim 1, wherein the piston includes control edges which cause opening or closing of the plurality of operating connections for a corresponding positioning relative to flow control edges of the cam phaser opening.

3. The piston according to claim 1, wherein the piston is secured by a terminal cover which partially envelops the piston.

4. The piston according to claim 3, wherein the terminal cover is provided for providing a supply connection.

5. The piston according to claim 1, wherein the piston includes a central channel.

6. The piston according to claim 1, wherein flow through openings of the piston are supplied with hydraulic fluid through a central channel of the piston to supply the plurality of connections.

7. A cam phaser, comprising: a rotor; a stator; and a piston that is received axially movable in a cam phaser opening of the cam phaser, wherein different operating connections of a plurality of operating connections of the cam phaser are opened and closed corresponding to a positioning of the piston, and wherein the piston and the rotor are configured according to claim 1.

8. The cam phaser according to claim 7, wherein a terminal cover of the piston is received in a hub of the cam phaser with a press fit.

9. The cam phaser according to claim 8, wherein the hub is rotor hub of the rotor.

10. The cam phaser according to claim 7, wherein the terminal cover is received in a receiving opening of the cam phaser, and wherein a stop is formed by the receiving opening.

11. The cam phaser according to claim 7, wherein an arrester element is configured to receive the piston in a secured and movable manner.

12. The cam phaser according to claim 11, wherein the arrester element is fixed at the cam phaser by fastener elements.

13. The cam phaser according to claim 11, wherein the arrester element includes an opening for receiving a piston pinion of the piston or the piston or an actuator plunger.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Additional advantages, features and details of the invention can be derived from the subsequent description of advantageous embodiments and from the drawing figures. The features and feature combinations recited in the preceding description and the features and feature combinations recited in the subsequent figure description are not only useable in the respectively stated combination but also in other combinations or by themselves without departing from the spirit and scope of the invention. Identical or functionally equivalent elements are associated with identical reference numerals. For reasons of clarity it is possible that the elements are not provided with reference numerals in all figures without however losing their association, wherein:

(2) FIG. 1 illustrates a longitudinal sectional view of a cam phaser according to the invention for a cam shaft with a piston according to the invention in a first embodiment;

(3) FIG. 1.1 illustrates a detail view I.I of the piston according to the invention according to FIG. 1;

(4) FIG. 2 illustrates a top view of the cam phaser according to the FIG. 1;

(5) FIG. 3 illustrates a longitudinal sectional view of a cam phaser according to the invention with the piston according to the invention in a second embodiment;

(6) FIG. 4 illustrates a sectional view IV of the cam phaser according to FIG. 3;

(7) FIG. 5 illustrates a longitudinal sectional view of the cam phaser according to the invention with the piston according to the invention in a third embodiment;

(8) FIG. 6 illustrates a detail VI of the camp phaser according to FIG. 5;

(9) FIG. 7 illustrates a longitudinal sectional view of the cam phaser according to the invention with the piston according to the invention in a fourth embodiment; and

(10) FIG. 8 illustrates a detail VIII of the cam phaser according to FIG. 7.

DETAILED DESCRIPTION

(11) A cam phaser 10 according to the invention for an internal combustion engine that is not illustrated in more detail for adjusting valve timing, put differently opening and closing times of gas exchange valves of the internal combustion engine is configured according to FIG. 1. The cam phaser 10 facilitates providing a change of valve timing during operation of the internal combustion engine. For this purpose the cam phaser 10 adjusts an angular position of a cam shaft of the internal combustion engine that is not illustrated in more detail relative to a crank shaft of the internal combustion engine that is not illustrated in more detail, wherein the cam shaft is rotated relative to the crank shaft continuously variably. Rotating the cam shaft moves the opening and closing times of the gas exchange valves so that so that performance and/or fuel burn and/or emissions of the internal combustion engine are optimized under various operating conditions.

(12) The cam phaser 10 includes a hydraulic unit 12 which controls a hydraulic fluid flowing through the cam phaser 10. The cam phaser 10 essentially includes a rotor 14 and a stator 16 enveloping the rotor 14. The hydraulic unit 12 is configured to be received in the rotor 14. Put differently the hydraulic unit 12 is received in a central cam phaser opening 18 of the cam phaser 10 and at least partially enveloped by the cam phaser. The cam phaser opening 18 is provided as an opening of the rotor 14.

(13) The hydraulic unit 12 includes a piston 24 according to the invention that is axially movable along a first longitudinal axis 22 of the hydraulic unit 12, c.f. also FIG. 1.1, wherein the piston 24 is at least partially received in the center cam phaser opening 18 which is preferably provided as an opening of the rotor 14.

(14) The first longitudinal axis 22 is configured coaxial with a second longitudinal axis 23 of the cam phaser opening 18. Furthermore, the piston 24 is at least partially received in a terminal cover 20 of the hydraulic unit 12 which assures a fluid supply of the piston 24 and thus of the cam phaser 10 through a supply connection P configured at the terminal cover 20.

(15) The stator 16 of the cam phaser 10 is connected torque proof with a drive wheel 26 of the cam shaft. At insides 28 of a stator base element 30 radially inward extending bars 32 are configured in even intervals so that an intermediary space 34 is formed between two respectively adjacent bars 32 as illustrated, in particular, in FIG. 2. A blade 36 of the rotor hub 38 of the rotor 14 is arranged so that it protrudes into an intermediary space 34. Corresponding to a number of the intermediary spaces 34 the rotor hub 38 includes a number of blades 36. Thus, each intermediary space 34 is divided into two pressure cavities by the blades 36. The blades 36 are integrally provided in one piece with the rotor hub 38 so that the rotor 14 is integrally provided in one piece. A pressure medium, typically a hydraulic fluid is introduced into the pressure cavities in a controlled manner by the hydraulic unit 12.

(16) Each of the two pressure cavities separated by a blade 36 includes an operating connection A; B. This means put differently that one pressure cavity of the pressure cavities separated by the blade 36 includes the first operating connection A and the other of the two pressure cavities separated by the blade 36 includes the second operating connection B.

(17) In order to change an angular position between the cam shaft and the crank shaft the pressure medium in one pressure cavity or in a second pressure cavity is pressurized, this means a pressure is increased, while the second pressure cavity or the first pressure cavity is unloaded. The unloading is performed through at least one tank drain T that is not illustrated in more detail through which the hydraulic fluid can drain. The pressure increase can also be assisted by non-return valves which open as a function of camshaft torque.

(18) The piston 24 is configured cylindrical and includes a central channel 40 extending along the first longitudinal axis 22, through which flow through openings distributed over a circumference, a first flow through opening 42, a second flow through opening 44, a third flow through opening 46 and a fourth flow through opening that is not illustrated in more detail and arranged opposite to the second flow through opening can be supplied with hydraulic fluid. Each pair of operating connections A, B is associated with a flow through opening 42; 44; 46. This means put differently as evident from FIG. 2, a total of eight pressure cavities is provided, wherein two respective pressure cavities are separated by one of a total of four blades 36 of the rotor 14 and the piston includes four pass through openings.

(19) The piston 24 is positioned by an electromagnetic actuator that is not illustrated in more detail so that a corresponding loading of the pressure cavities can be provided. An actuator plunger that is not illustrated in more detail of the actuator is configured so that it engages a piston pinion 48 so that the piston 24 is positioned in the phaser opening 18 by the actuator.

(20) In addition to the rotor 14 and the stator 16 the cam phaser 10 includes a safety disc 50 which is configured for axially securing the rotor 14. In this embodiment the safety disc 50 is configured as a drive wheel 26.

(21) The safety disc 50 is connected torque proof with the stator 16 by the attachment devices 52. Furthermore, the safety disc 50 is used for receiving a locking pin 54 of a locking device 56 of the cam phaser 10, wherein the locking device 56 further includes a reset element 58 configured as a spiral spring and a cover element 60. In order to interlock the rotor 15 with the stator 16 the locking pin 54 is positioned in a receiving opening 62 of the safety disc 50.

(22) A back flow of the fluid into the supply connection P is prevented by a check valve 64 which is arranged in a portion of a cover end 66 that is oriented away from the piston pinion 48 and downstream of a fluid filter 70 secured in position by a safety element 68 in the terminal cover 20. A safety disc 72 is received between the check valve 64 which is configured as an annular check valve and the fluid filter 70 in the terminal cover 20, wherein disc openings 74 of the flow disc 72 are closeable by the check valve 64.

(23) The check valve 64 is loaded by a first preload element 76 in a direction towards the flow disc 72. This means put differently the check valve is pressed by the first preload element 76 against the flow disc 72 for closing the disc openings 74. As soon as the hydraulic fluid flowing over through the supply connection P has a pressure which is greater than a pre load force of the first preload element 76 and the pressure in the central channel 40, the check valve 64 lifts off from the flow disc 72 and the hydraulic fluid enters through the disc opening 74 into an entry channel 78 of the terminal cover 20 wherein the entry channel 78 is flow connected with the central channel 40.

(24) In order to arrest and support the piston 24, the piston 24 is supported in an entry channel 78 and preloaded by a second preload element 80 relative to the terminal cover 20. In order to further arrest and support the piston 24 a piston end 82 of the piston 24 that is oriented away from the cover end 66 is secured by an arresting element 84 at the rotor hub 38 through additional attachment devices 86. The arresting element 84 includes an opening 88 for receiving the piston pin 48 in an axially movable manner. Thus, the piston 24 is arranged axially movable in the adjustment opening 18, wherein the axial movement of the piston 24 is limited at one end by the terminal cover 20 and at another end by the arresting element 84.

(25) The terminal cover 20 is configured so that it contacts the rotor 14 wherein a press fit is advantageously provided between the terminal cover 20 and a receiving opening 92 that is configured at a rotor side 90 that is oriented away from the arresting element 84.

(26) As illustrated in FIG. 1 the flow through or emptying of the pressure cavities is performed by operating connections A, B communicating directly with the piston 24 wherein the operating connections A, B are configured in the cam phaser opening 18. For this purpose the piston 24 includes control edges 94 in addition to the pass through openings 42, 44, 46 wherein flow control edges 96 of the operating connections A, B of the cam phaser opening 18 are covered and/or released by the control edges 94. An inner contour 102 of the cam phaser opening 18 is configured complementary to an outer contour 104 of the piston 24 for opening or closing the operating connections A, B. The term complementary does not mean in this context that the inner contour and the outer contour match each other, but they are oriented towards each other and configured to provide a communication between the pass-through openings and the connections, in particular, the operating connections A, B.

(27) The terminal cover 20 is supported at the rotor hub 38 at an additional stop 100 which is also configured annular.

(28) FIGS. 3-8 illustrate three additional embodiments of the piston 24 according to the invention and of the cam phaser 10 according to the invention. Compared to the first embodiment the piston 24 of the second to fourth embodiment is received in its entirety in the cam phaser 10. Put differently this means that the terminal cover 20 can be omitted in this embodiment.

(29) FIG. 3 illustrates a longitudinal sectional view of the cam phaser 10 in a second embodiment. FIG. 4 illustrates the corresponding piston 4 in a detail of the cam phaser 10. In this embodiment a support element 106 is configured which is received in its entirety in the cam phaser opening and is used for supporting a first preload element 76 and a second preload element 80. The cam phaser opening 18 is configured to receive the safety element 68; the fluid filter 70, the flow disc 72 and the first preload element 76.

(30) FIGS. 5 and 6 illustrate a longitudinal sectional view of the cam phaser 10 or of the corresponding piston 24 in a detail of the cam phaser 10 in a third embodiment. The cam phaser 10 includes a supply channel 108 that is arranged off center from the first longitudinal axis 22 wherein the supply channel is flow connected with the supply connection P. The supply channel 108 is flow connected with the piston 24 wherein hydraulic fluid flowing through the supply channel 108 can flow between the flow through openings of the operating connections A, B. Compared to first embodiment and the second embodiment where supply fluid is routed through the central channel 40 of the piston, supply fluid is routed through the phaser 10. In this case, the central channel 40 serves as tank connection T.

(31) FIG. 7 illustrates the cam phaser 10 according to the invention in a longitudinal sectional view in a fourth embodiment and FIG. 8 illustrates the corresponding piston 24 in a detail of the cam phaser 10. The supply connection P like in the first two embodiments is configured coaxial with the first longitudinal axis 22 so that the supply connection P can flow through the piston 24. The piston 24 includes two additional check valves 110 that are arranged in the portion of the pass through openings 42, 44, 46. The piston 24 is configured to utilize cam shaft torques and their associated pressure pulses in the cam phaser 10. A tank connection T is configured off center from the first longitudinal axis 22 in the cam phaser 10 and flowable through a drain channel 112.

(32) Although several embodiments of the present invention and its advantages have been described in detail, it should be understood that changes, substitutions, transformations, modifications, variations, permutations and alterations may be made therein without departing from the teachings of the present invention, the spirit and the scope of the invention being set forth by the appended claims.