DE102018130094B4 - Hydraulic camshaft adjuster and locking procedure - Google Patents

Abstract

The invention relates to a hydraulic camshaft adjuster (1) for adjusting the control times of gas exchange valves of an internal combustion engine, with a stator (2) which can be rotated synchronously with a crankshaft of the internal combustion engine, and with a rotor (3) which is arranged so as to be rotatable relative to the stator (2) and which can be rotated synchronously with a camshaft. The hydraulic camshaft adjuster (1) also has two groups of working chambers (8, 9) with different directions of action, each of which can be acted upon by a pressure medium (11) flowing in or out of a pressure medium circuit, and a center locking device (10) for temporarily locking the rotor in a defined position relative to the stator (2), the center locking device comprising a first locking element (12) and a second locking element (13). It is provided that the first locking element (12) is designed as a hydraulic control element which, in a first operating state, blocks a hydraulic connection between a second working chamber (9) of the hydraulic camshaft adjuster and a reservoir (31) for the pressure medium (11) and, in a second operating state, releases a hydraulic connection between the second working chamber (9) and the reservoir (31) for the pressure medium (11), wherein the second locking element (13) serves exclusively for the mechanical locking of the rotor (3) in the locking gate (14) and is designed free of a hydraulic control function.The invention further relates to a method for locking such a hydraulic camshaft adjuster (1).

Description

The invention relates to a hydraulic camshaft adjuster and a method for locking a rotor in a hydraulic camshaft adjuster according to the preamble of the independent claims.

Hydraulic camshaft adjusters are used in internal combustion engines to adjust the load state of the internal combustion engine and thus increase the efficiency of the internal combustion engine. Hydraulic camshaft adjusters that work according to the vane cell principle are known from the prior art. These camshaft adjusters generally have a basic structure of a stator that can be driven by a crankshaft of an internal combustion engine and a rotor that is connected in a rotationally fixed manner to the camshaft of the internal combustion engine. An annular space is provided between the stator and the rotor, which is divided into a plurality of working chambers by projections that are connected in a rotationally fixed manner to the stator and extend radially inwards. Each of these working chambers is divided into two pressure chambers by a vane that extends radially outwards from the rotor. Depending on the pressure chambers being subjected to a hydraulic pressure medium, the position of the rotor relative to the stator and thus also the position of the camshaft relative to the crankshaft can be adjusted in the “early” or “late” direction. Hydraulic camshaft adjusters with a center lock are known, in which the rotor can be locked in a middle position in addition to the respective end positions, in particular to make starting the engine easier. In exceptional cases, for example if the combustion engine stalls, it is possible that the locking device does not lock the rotor as intended and the camshaft adjuster must be operated with the rotor unlocked in the subsequent start-up phase. However, since some combustion engines have very poor start-up behavior if the rotor is not locked in the middle position, the rotor must then be automatically rotated to the middle locking position in the start-up phase and then locked.

From the DE10 2012 211 870 A1 A hydraulic camshaft adjuster with a center locking device is known. The center locking device has a first and a second locking gate, the first locking gate being formed on a first cover and the second locking gate being formed on a second cover opposite the first cover, and the locking pins emerging on opposite end faces of the rotor.

From the EN 10 2014 212 617 A1 A hydraulic camshaft adjuster with a center locking function is known, whereby the rotor can be rotated from any position into the center locking position according to the principle of a hydraulic ratchet, whereby rotational movement in the opposite direction to this rotation is blocked. The hydraulic ratchet uses alternating torques from the camshaft drive to pull the rotor from an "early" adjustment position or a "late" adjustment position into the center position, depending on the starting position. To do this, a group of working chambers must be closed in order to prevent rotation in the opposite direction to the intended direction of rotation and to support the corresponding moments of the camshaft. The locking pins can be arranged on different faces of the rotor or on the same side.

From the EN 10 2007 004 196 A1 A hydraulic camshaft adjuster with a two-part locking cover is known. In order to be able to precisely adjust the play of the locking pins in their recesses, the locking cover is made up of two covers, each of which has a recess for engaging a locking pin.

Furthermore, a hydraulic camshaft adjuster with a pressure medium reservoir and a so-called “smart phasing function” is known from the prior art, in which the working chambers can suck in additional pressure medium from a reservoir in the event of an insufficient supply of pressure medium by the pressure medium pump in order to avoid the suction of air and the associated malfunction of the hydraulic camshaft adjuster.

The disadvantage is that the function of a hydraulic ratchet is heavily dependent on the pressure medium supply and the viscosity of the pressure medium. In cold temperatures, the function can be limited or fail due to the high flow resistance. This does not matter during a normal engine stop, as the pressure medium is warmed up by the engine operation and has a low viscosity. If the engine is switched off without being locked, for example by stalling, the hydraulic camshaft adjuster must lock the combustion engine as a fail-safe function when the engine is started. If the engine is started after a long period of cooling at a low ambient temperature, the hydraulic ratchet can fail and the lock in the center locking position does not take place.

Finally, a generic camshaft adjuster goes out EN 10 2013 204 928 A1 out.

The object of the invention is to further develop a hydraulic camshaft adjuster in such a way that the rotor is reliably locked in the center locking position regardless of the external conditions. In addition, a corresponding locking method is to be specified.

According to the invention, the object is achieved by a hydraulic camshaft adjuster for adjusting the control times of gas exchange valves of an internal combustion engine with a stator which can be rotated synchronously with a crankshaft of the internal combustion engine, and with a rotor which is arranged so as to be rotatable relative to the stator and which can be rotated synchronously with a camshaft. The hydraulic camshaft adjuster also has two groups of working chambers with different directions of action, each of which can be acted upon by a pressure medium flowing in or out of a pressure medium circuit, and a center locking device for temporarily locking the rotor in a defined position relative to the stator, the center locking device comprising a first locking element and a second locking element. It is provided that the first locking element is designed as a hydraulic control element which, in a first operating state, blocks a hydraulic connection between a second working chamber of the hydraulic camshaft adjuster and a reservoir for the pressure medium and, in a second operating state, releases a hydraulic connection between the second working chamber and the reservoir for the pressure medium, wherein the second locking element serves exclusively for mechanically locking the rotor in the locking gate and is designed free of a hydraulic control function. As a result, the rotor of the hydraulic camshaft adjuster can be rotated into the center locking position essentially independently of the viscosity of the pressure medium, thus facilitating locking in the center locking position. The mechanical ratchet and the hydraulic ratchet can simultaneously contribute to adjusting the rotor to the center locking position. The hydraulic ratchet acts when the drain of the working chamber pushing towards the center locking position is closed. The first locking pin closes this drain in the locked position. The first pressure chamber can release pressure medium in any operating state and no longer has a locking function. The locking pin in the second pressure chamber has a hydraulic control function and can therefore support the function of a hydraulic ratchet. In the event of a critical locking from an adjustment position from "late" towards the middle, the locking is supported by a mechanical and a hydraulic ratchet function. In the event of an adjustment from "early" towards the middle, there is no hydraulic support, but the rotor is pulled towards the middle position by the camshaft friction. By eliminating a hydraulic control function in the second locking pin, additional holes in the rotor can be eliminated, which reduces the complexity of the rotor. This can reduce the manufacturing costs for the rotor and thus for the hydraulic camshaft adjuster.

The features listed in the dependent claims enable advantageous improvements and further developments of the hydraulic camshaft adjuster specified in the independent claim.

In a preferred embodiment of the invention, the first locking element and the second locking element are engaged in a common locking groove when the rotor is locked in the center position. This allows the space required for the locking mechanism to be reduced. The two locking elements can be arranged in the rotor hub of the rotor, and they can be moved closer together due to the elimination of the supply bore for the second locking element.

In an advantageous embodiment of the hydraulic camshaft adjuster, a groove is formed on the first locking element, which opens the hydraulic connection between the second working chamber and the reservoir. The diameter of the locking element, in particular of a cylindrical locking pin, can be reduced by means of a preferably circumferential groove, so that the cross section of the locking element in the region of the groove no longer completely blocks the hydraulic connection and thus enables pressure medium to flow through. The groove allows the locking element to be rotated as desired by the locking spring, so that an additional guide for the locking element is not necessary. As an alternative to a groove, the locking element can also have a through-hole in order to establish a hydraulic connection between the second working chamber and the central valve. However, this requires that rotation of the locking element is reliably prevented, which can be achieved, for example, by guide surfaces on the locking element. element and the corresponding mounting hole for the locking element.

In a further improvement of the invention, it is provided that the first locking element and the second locking element are arranged in the rotor of the hydraulic camshaft adjuster. This allows the supply channels in the rotor to be made comparatively short, which means that the machining effort for the rotor can be reduced, which lowers the manufacturing costs. In addition, this means that supply channels in the blades of the rotor can be omitted.

This allows the blades to be made narrower and with less material, which further reduces the cost of the rotor.

In an advantageous embodiment of the invention, the first working chamber is hydraulically connected to a central valve of the hydraulic camshaft adjuster in all operating states. This allows the second locking element to be designed as a simple cylindrical pin and is therefore particularly simple and inexpensive to manufacture. In addition, the pressure medium from the first working chamber can always flow in the direction of the central valve and from there into the reservoir, which eliminates a hydraulic blocking function of this chamber. This simplifies the pressure medium circuit, which means that the central valve can also be designed comparatively simply and inexpensively.

In an advantageous further development, the locking gate is designed asymmetrically, with the locking gate only having a step on its side facing the second locking element. A step allows the second locking element to move towards the bottom of the locking gate according to the principle of a mechanical ratchet and lock the rotor there in its central position. Such a step can be dispensed with on the other side of the locking gate, which reduces the width of the locking gate.

According to the invention, a reservoir is provided which is connected to the first working chamber via a first connecting line and to the second working chamber via a second connecting line. A reservoir can prevent one of the pressure chambers from being undersupplied with pressure medium, thus preventing a negative pressure from occurring in one of the pressure chambers and thus preventing air from being sucked in.

It is particularly preferred if a check valve is arranged in each of the connecting lines. A check valve in the supply line can be used to prevent the pressure medium from flowing back from the working chambers into the reservoir in a simple and cost-effective manner. This ensures that pressure builds up in the working chambers.

In a further improvement of the hydraulic camshaft adjuster, the locking gate is designed in a locking cover which limits the stator and/or the rotor in the axial direction. The locking gate can be incorporated into a locking cover relatively easily and inexpensively. A locking gate in the stator would also be conceivable in principle, but this increases the manufacturing effort and thus the costs for the camshaft adjuster.

According to the invention, a method for locking such a hydraulic camshaft adjuster is proposed, wherein the first locking pin supports rotation of the rotor relative to the stator in the direction of the center locking position according to the operating principle of a hydraulic ratchet and the second locking pin supports rotation of the rotor relative to the stator in the direction of the center locking position according to the operating principle of a mechanical ratchet and inhibits or blocks rotation in the opposite direction. As a result, the rotor of the hydraulic camshaft adjuster can be rotated into the center locking position essentially independently of the viscosity of the pressure medium, thus facilitating locking in the center locking position. The mechanical ratchet and the hydraulic ratchet can simultaneously contribute to adjusting the rotor to the center locking position. The hydraulic ratchet works when the drain of the working chamber pushing towards the center locking position is closed. The first locking pin closes this drain in the locked position.

The various embodiments of the invention mentioned in this application can be advantageously combined with one another, unless stated otherwise in individual cases.

• 1 eine schematische Darstellung eines hydraulischen Nockenwellenverstellers in einer Schnittdarstellung;
• 2 eine schematische Darstellung einer erfindungsgemäßen Mittenverriegelungseinrichtung für einen hydraulischen Nockenwellenversteller, wobei sich der Rotor in der verriegelten Mittenposition befindet;
• 3 eine schematische Darstellung einer Verriegelung des Rotors aus einer Verstellposition in Richtung „früh“;
• 4 eine schematische Darstellung einer Verriegelung des Rotors aus einer Verstellposition in Richtung „spät“;
• 5 eine schematische Darstellung einer Verriegelung des Rotors aus einer Verstellposition in Richtung „spät“, wobei das zweite Verriegelungselement nach dem Prinzip einer mechanischen Ratsche auf der Stufe der Verriegelungskulisse anliegt; und
• 6 eine schematische Darstellung der Mittenverriegelungseinrichtung bei einem Normalbetrieb des hydraulischen Nockenwellenverstellers, bei dem der Rotor frei drehbar gegenüber dem Stator ist.

The invention is explained in more detail below using a preferred embodiment and the associated drawings. Identical components or components with the same function are identified by the same reference numerals. They show:

• 1 a schematic representation of a hydraulic camshaft adjuster in a sectional view;
• 2 a schematic representation of a center locking device according to the invention for a hydraulic camshaft adjuster, wherein the rotor is in the locked center position;
• 3 a schematic representation of a locking of the rotor from an adjustment position in the “advanced” direction;
• 4 a schematic representation of a locking of the rotor from an adjustment position in the “retarded” direction;
• 5 a schematic representation of a locking of the rotor from an adjustment position in the “late” direction, with the second locking element resting on the step of the locking gate according to the principle of a mechanical ratchet; and
• 6 a schematic representation of the center locking device during normal operation of the hydraulic camshaft adjuster, in which the rotor is freely rotatable relative to the stator.

In 1 An embodiment of a hydraulic camshaft adjuster 1 according to the invention for adjusting the valve timing of an internal combustion engine is shown. 1 The hydraulic camshaft adjuster 1 shown schematically is designed in a known manner as a vane cell adjuster and comprises a stator 2 which can be driven by a crankshaft (not shown) of an internal combustion engine and a rotor 3 which can be connected in a rotationally fixed manner to a camshaft (also not shown). The rotor 3 has a rotor hub 4 from which a plurality of vanes 6 extend in the radial direction. The stator 2 and the rotor 3 have a common central axis 38 about which the rotor 3 can be rotated relative to the stator 2. The stator 2 has a plurality of webs 5 which divide an annular space between the stator 2 and the rotor 3 into a plurality of pressure chambers 7. The pressure chambers 7 are each divided by the vanes 6 of the rotor 3 into two working chambers 8, 9 with different directions of action. The stator 2 is delimited on a first end face by a locking cover 15 and on a second end face opposite the first end face by a sealing cover 18. The rotor 3 has a central opening 21 into which a central valve 22 can be inserted to control the pressure medium supply in the working chambers 8, 9. Several screw openings 20 are formed on the stator 2, via which the sealing cover 18 and the locking cover 15 can be fixed by means of screws. Furthermore, a drive toothing 19 is formed on the stator 2, via which the stator 2 can be connected to the crankshaft of the internal combustion engine by means of a traction device. The rotor 3 has two axial bores in which a first locking element 12 and a second locking element 13 are arranged so as to be axially displaceable. The locking elements 12, 13 can be locked in a locking slot 14 in the locking cover 15, whereby rotation of the rotor 3 relative to the stator 2 is temporarily prevented.

In 2 A central locking device 10 of a hydraulic camshaft adjuster 1 is shown in a schematic representation. The central locking device 10 comprises a locking slot 14 in which the two locking elements 12, 13 can engage. In 2 the center locking device 10 is shown in a locked operating state, in which rotation of the rotor 3 relative to the stator 2 is temporarily and reversibly releasably blocked. The locking elements 12, 13 are each pressed into the locking slot 14 by a locking spring 29, the locking slot 14 being pressure-free and no pressure being exerted on the end faces of the locking elements 12, 13, so that the end faces of the locking elements 12, 13 rest against a base 17 of the locking slot 14. The lateral surfaces of the locking elements 12, 13 rest against a step 16 or a wall of the locking cover 15. In the middle position, which is also referred to as the middle locking position, the vanes 6 of the rotor 3 divide the pressure chamber 7 into first working chambers 8 and second working chambers 9, each of approximately equal size. A central valve 22 is positioned such that a pressure medium 11 can flow from both the working chambers 8, 9 and the locking gate 14 via a return line 33 into a storage container 31. For this purpose, the central valve 22 is connected to the first working chamber 8 of the hydraulic camshaft adjuster 1 via a first supply line 23, which is referred to below as the A channel 23. Furthermore, the central valve 22 is connected to the second working chamber 9 via a second supply line 24, which is referred to below as the B channel 24. The hydraulic connection between the central valve 22 and the second working chamber 9 can be interrupted by the first locking element 12, so that pressure medium 11 is prevented from flowing out of the second working chamber. The central valve 22 is connected to the locking gate 14 via a third supply line 25, which is referred to below as C-channel 25. For adjustment, the central valve 22 is loaded by a central valve spring 34 and can be adjusted by an actuator (not shown) against the force of the central valve spring 34. An oil pump 30 is also provided, with which the pressure medium 11 can be pressurized and pumped into the working chamber. mern 8, 9 or into the locking gate 14. Furthermore, a reservoir 26 is provided on the hydraulic camshaft adjuster 1, which is connected via a first supply line 36 to the first working chamber 8 and via a second supply line 37 to the second working chamber 9 of the hydraulic camshaft adjuster 1. A check valve 27, 28 is arranged in each of the supply lines 36, 37, which block the flow of pressure medium 11 from the working chambers 8, 9 into the reservoir 26. The storage container 31 is also connected to the reservoir 26 via a reservoir line 39. A third check valve 32 is provided between the oil pump 30 and the central valve 22 in order to prevent the pressure medium 11 from flowing back in the direction of the oil pump 30.

The function of the hydraulic ratchet mechanism depends on the oil supply and the temperature-dependent viscosity of the pressure medium. At cold temperatures, the function of the hydraulic ratchet mechanism can fail due to the high flow resistance. This is particularly important if an internal combustion engine is switched off unexpectedly shortly after a cold start, e.g. by stalling, and the hydraulic camshaft adjuster 1 remains unlocked. If the engine is started when the pressure medium 11 is cold and therefore viscous, the hydraulic ratchet mechanism can fail. An additional mechanical ratchet is used to cover a fail-safe function of the hydraulic camshaft adjuster 1. This comprises a step 16 in which the second locking element 13 can engage between the end stop positions and the center locking position.

The mechanical ratchet and the hydraulic ratchet can and should simultaneously contribute to the adjustment of the rotor 3 into the center locking position. The hydraulic ratchet mechanism acts when the outlet via the working chamber 8, 9 pushing towards the center position is closed. In the hydraulic camshaft adjuster 1 according to the invention, only the B channel 24 can be closed, with the first locking element 12 blocking the outlet in the locked position.

In 3 the center locking device 10 is shown in an operating state in which the rotor 3 is rotated from an "early" adjustment position into the center locking position. The first locking element 12 rests with its front face on a plateau 35 of the locking gate 14, while the second locking element 13 has already been pushed into the pressure-free locking gate 14 and there rests with its front face on the bottom 17 of the locking gate. The second locking element 13 limits rotation in the "late" direction beyond the center. The camshaft friction drags the rotor 3 and thus the first locking element 12 along until the first locking element 12 also engages in the locking gate 14 and there rests on the bottom 17.

In 4 the rotor 3 is rotated in an adjustment position in the "late" direction. The first locking element 12 is pushed into the pressure-free locking gate 14 by the spring force of the locking spring 29, while the second locking element 13 rests with its front face on the plateau 35 of the locking gate 14. By pushing the first locking element 12 into the locking gate 14, the hydraulic connection from the second working chamber 13 to the central valve 22 and further into the reservoir 31 is blocked, so that no further pressure medium 11 can flow out of the second working chamber 9. The flow of pressure medium 11 from the first working chamber 9 is possible, however, so that the rotor 3 is rotated in the direction of the central locking position according to the principle of a hydraulic ratchet.

In 5 The rotor 3 is compared to the illustration in 4 rotated a little in the direction of the center locking position so that the second locking element 13 has sunk into the step 16 on the locking link 14. The second locking element blocks rotation of the rotor 3 in the "late" direction by the contact of the outer surface on the locking link 14, while rotation in the direction of the center locking position is still possible. The second locking element blocks in the "late" direction when moving down from the plateau 35 in the direction of the base 17 like a mechanical ratchet and supports rotation in the direction of the center locking position.

In 6 the rotor 3 is shown in an unlocked position. For this purpose, the locking gate 14 and the second working chamber 9 are pressurized with pressure medium 11 by the oil pump 30. The hydraulic pressure in the locking gate 14 pushes the locking elements 12, 13 into the rotor 3 against the spring force of the locking springs 29 and thus enables the rotor 3 to rotate. The hydraulic connection between the central valve 22 and the second working chamber 9 is opened again so that the pressure medium 11 can flow into this second working chamber 9.

Thus, with a hydraulic camshaft adjuster 1 according to the invention, it is possible to rotate the rotor 3 into the center lock locking position even at low temperatures and high viscosity of the pressure medium and thus to ensure reliable locking in the center locking position regardless of the external conditions.

List of reference symbols

1

hydraulic camshaft adjuster

2

stator

3

rotor

4

Rotor hub

5

web

6

wing

7

Printing room

8th

Chamber of Labor

9

Chamber of Labor

10

Center locking device

11

Pressure medium

12

First locking element

13

Second locking element

14

Locking mechanism

15

Locking cover

16

Level

17

Floor

18

Sealing cover

19

Drive gearing

20

Screw opening

21

Central opening

22

Central valve

23

First supply line / A-channel

24

Second supply line / B-channel

25

Third supply line / C-channel

26

reservoir

27

First check valve

28

Second check valve

29

Locking spring

30

Oil pump

31

Storage container

32

Third check valve

33

Return line

34

Central valve spring

35

plateau

36

Supply line, connecting line

37

Supply line, connecting line

38

Central axis

39

Reservoir line

Claims (9)

Hydraulic camshaft adjuster (1) for adjusting the control times of gas exchange valves of an internal combustion engine, with - a stator (2) which can be rotated synchronously with a crankshaft of the internal combustion engine, - a rotor (3) which is arranged so as to be rotatable relative to the stator (2) and which can be rotated synchronously with a camshaft, - two groups of working chambers (8, 9) which can each be acted upon by a pressure medium (11) flowing in or out of a pressure medium circuit and which have a different direction of action, - a center locking device (10) for temporarily locking the rotor (3) in a defined position relative to the stator (2) with a first locking element (12) and a second locking element (13) - wherein the first locking element (12) is designed as a hydraulic control element which, in a first operating state, forms a hydraulic connection between a second working chamber (9) of the hydraulic camshaft adjuster and a reservoir (31) for the pressure medium (11) and, in a second operating state, releases a hydraulic connection between the second working chamber (9) and the storage container (31) for the pressure medium (11), wherein the second locking element (13) serves exclusively for the mechanical locking of the rotor (3) in a locking gate (14) and is designed free of a hydraulic control function, characterized in that - a reservoir (26) is provided which is connected to the first working chamber (8) via a first connecting line (36) and to the second working chamber (9) via a second connecting line (37). Hydraulic camshaft adjuster (1) according to Claim 1 , characterized in that - the first locking element (12) and the second locking element (13) are engaged in a common locking groove (14) when the rotor (3) is locked in the center position. Hydraulic camshaft adjuster (1) according to Claim 1 or 2 , characterized in that - on the first locking element (12) a groove which opens the hydraulic connection between the second working chamber (9) and the storage container (31). Hydraulic camshaft adjuster (1) according to one of the Claims 1 until 3 , characterized in that - the first locking element (12) and the second locking element (13) are arranged in the rotor (3) of the hydraulic camshaft adjuster (1). Hydraulic camshaft adjuster (1) according to one of the Claims 1 until 4 , characterized in that - the first working chamber (8) is hydraulically connected to a central valve (22) of the hydraulic camshaft adjuster (1) in all operating states. Hydraulic camshaft adjuster (1) according to one of the Claims 1 until 5 , characterized in that - the locking link (14) is designed asymmetrically, wherein the locking link (14) has a step (16) exclusively on its side facing the second locking element (13). Hydraulic camshaft adjuster (1) according to one of the preceding claims, characterized in that - a check valve (27, 28) is arranged in each of the connecting lines (36, 37). Hydraulic camshaft adjuster (1) according to one of the Claims 1 until 7 , characterized in that - the locking link (14) is formed in a locking cover (15) which limits the stator (2) and/or the rotor (3) in the axial direction. Method for locking a hydraulic camshaft adjuster (1) according to the generic term of Claim 1 , characterized in that - the first locking element (12) according to the operating principle of a hydraulic ratchet and - the second locking element (13) according to the operating principle of a mechanical ratchet supports a rotation of the rotor (3) relative to the stator (2) in the direction of the central locking position and inhibits or blocks a rotation against this direction.

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