Hydraulic camshaft adjuster having a mechanical and a hydraulic ratchet

Abstract

The disclosure relates to a hydraulic camshaft adjuster having a stator, which is synchronously rotatable with a crankshaft of the internal combustion engine, a rotor rotatably arranged relative to the stator and synchronously rotatable with a camshaft, two groups of working chambers that can each be loaded with a pressure medium in a pressure medium circuit, and a central locking device for locking the rotor in a defined position relative to the stator. The stator is delimited on a first front end by a multi-part locking cover. The multi-part locking cover has a first locking cover and a second locking cover. A first stage of a mechanical ratchet is formed on the first locking cover, and at least one further stage of the mechanical ratchet is formed on the second locking cover.

Claims

1. A hydraulic camshaft adjuster for adjusting timing of gas exchange valves of an internal combustion engine, the hydraulic camshaft adjuster comprising: a stator configured to be synchronously rotatable with a crankshaft of the internal combustion engine, a rotor configured to be rotatable relative to the stator and synchronously rotatable with a camshaft, two groups of working chambers formed by the stator and rotor, the two groups of working chambers configured to be supplied a pressure medium flowing in or out in a pressure medium circuit, a central locking device for locking the rotor in a defined position relative to the stator, the stator delimited at a first end by a multi-part locking cover, the multi-part locking cover having a first locking cover and a second locking cover, and a first step of a mechanical ratchet formed on the first locking cover, and at least one second step of the mechanical ratchet formed on the second locking cover, and a check valve plate arranged between the first locking cover and the second locking cover.

2. The hydraulic camshaft adjuster as claimed in claim 1, wherein the second locking cover includes at least one insert configured to operatively connect with a locking pin of the central locking device.

3. The hydraulic camshaft adjuster as claimed in claim 2, wherein a stop for the locking pin is formed on the at least one insert.

4. The hydraulic camshaft adjuster as claimed in claim 2, wherein the at least one second step of the mechanical ratchet is formed on the at least one insert.

5. The hydraulic camshaft adjuster as claimed in claim 2, wherein the at least one insert is composed of a harder material than a material of the second locking cover.

6. The hydraulic camshaft adjuster as claimed in claim 5, wherein the at least one insert is composed of a sintered metal or is produced by a fine blanking or extrusion method.

7. The hydraulic camshaft adjuster as claimed claim 2, wherein the at least one insert is pressed into a guide slot base of the central locking device.

8. The hydraulic camshaft adjuster as claimed in claim 2, wherein the at least one insert is secured against tilting or falling out by the check valve plate.

9. A hydraulic camshaft adjuster for adjusting timing of gas exchange valves of an internal combustion engine, the hydraulic camshaft adjuster comprising: a stator configured to be synchronously rotatable with a crankshaft of the internal combustion engine, a rotor configured to be rotatable relative to the stator and synchronously rotatable with a camshaft, a central locking device for locking the rotor to the stator, the stator delimited at a first end by a multi-part locking cover, the multi-part locking cover having a first locking cover and a second locking cover, and a first step of a mechanical ratchet formed on the first locking cover, and at least one second step of the mechanical ratchet formed on the second locking cover, and a check valve plate arranged between the first locking cover and the second locking cover.

10. The hydraulic camshaft adjuster as claimed in claim 9, wherein the central locking device comprises a locking pin configured to move and stop at three different positions.

11. The hydraulic camshaft adjuster as claimed in claim 10, wherein the locking pin is configured to move to a locked position, an intermediate position, and an unlocked position.

12. The hydraulic camshaft adjuster as claimed in claim 10, wherein in the locked position and the intermediate position, the rotor is locked to the stator.

13. The hydraulic camshaft adjuster as claimed in claim 12, wherein the locking pin includes a recess configured to receive a pressure medium.

14. The hydraulic camshaft adjuster as claimed in claim 13, wherein in the unlocked position of the locking pin, the recess is configured to fluidly connect a duct arranged within the rotor to a working chamber of the hydraulic camshaft adjuster.

15. The hydraulic camshaft adjuster as claimed in claim 9, wherein the second locking cover includes at least one insert configured to operatively connect with a locking pin of the central locking device.

16. The hydraulic camshaft adjuster as claimed in claim 15, wherein a stop for the locking pin is formed on the at least one insert.

17. The hydraulic camshaft adjuster as claimed in claim 16, wherein the at least one second step of the mechanical ratchet is formed on the at least one insert.

18. The hydraulic camshaft adjuster as claimed in claim 15, wherein the first locking cover is arranged to engage the rotor.

19. The hydraulic camshaft adjuster as claimed in claim 16, wherein the first locking cover includes an aperture configured to receive pressure medium to move the locking pin.

20. The hydraulic camshaft adjuster as claimed in claim 15, wherein the check valve plate secures the at least one insert within the second locking cover.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The disclosure is explained in greater detail below by means of an illustrative embodiment and the associated drawings. Here, components that are the same or components with the same function are denoted by the same reference numerals. In the drawings:

(2) FIG. 1 shows an illustrative embodiment of a hydraulic camshaft adjuster according to the disclosure in section;

(3) FIG. 2 shows the two-part locking cover of a hydraulic camshaft adjuster according to the disclosure;

(4) FIG. 3 shows an enlarged illustration of an insert into the locking cover;

(5) FIG. 4 shows a diagram intended to illustrate the interplay between the mechanical and the hydraulic ratchet function in a hydraulic camshaft adjuster according to the disclosure, in which one of the locking pins is locked;

(6) FIG. 5 shows a second diagram intended to illustrate the interplay between the mechanical and the hydraulic ratchet function in a hydraulic camshaft adjuster according to the disclosure, in which the outflow from the working chamber which pushes toward the central locking position is closed; and

(7) FIG. 6 shows a third diagram intended to illustrate the interplay between the mechanical and the hydraulic ratchet function in a hydraulic camshaft adjuster according to the disclosure, in which the outflow from the working chamber which pushes toward the central locking position is open.

DETAILED DESCRIPTION OF THE EMBODIMENTS

(8) FIG. 1 illustrates an embodiment example of a hydraulic camshaft adjuster 1 according to the disclosure for adjusting the valve timings of an internal combustion engine. The hydraulic camshaft adjuster 1 illustrated schematically in FIG. 1 is designed in a known manner as a rotary vane adjuster and comprises a stator 2, which can be driven by a crankshaft (not illustrated) of an internal combustion engine, and a rotor 3, which can be connected to a camshaft (likewise not illustrated) for conjoint rotation therewith. The rotor 3 has a rotor hub 4, from which a plurality of vanes 6 extends in a radial direction. The stator 2 has a plurality of ridges 5, which divide an annular space between the stator 2 and the rotor 3 into a plurality of pressure spaces 7. The pressure spaces 7 are each divided by the vanes 6 of the rotor 3 into two working chambers 8, 9 with different directions of action. In addition to the working chambers 8, 9 known in the normal operation of the hydraulic camshaft adjuster 1, support chambers for hydraulic support of the rotor 3 during rotation into a central locking position are provided between the rotor 3 and the stator 2. The stator 2 is delimited at a first end 14 by a multi-part locking cover 11, 12 and at a second end 15 situated opposite the first end 14 by a sealing cover 13. An additional reservoir cover, which has a reservoir for pump-independent supply of pressure medium to the working chambers 8, 9, can be mounted on the multi-part locking cover 11, 12. The multi-part locking cover 11, 12 has a first locking cover 11, which is connected to the stator 2 for conjoint rotation therewith. The multi-part locking cover 11, 12 furthermore has a second locking cover 12, which is connected to the first locking cover 11 and/or to the stator 2 for conjoint rotation therewith. An insert 21, which can be of single-part or multi-part design, is inserted into the second locking cover 12. The insert is can be a stepped insert 21, as illustrated in FIG. 1, and has a step 22, on which a locking pin 17 of a central locking device 10 of the hydraulic camshaft adjuster 1 can come to rest. The locking pin 17 is preloaded by the force of a spring 18 and can be pushed into the rotor 3 hydraulically by corresponding pressure buildup by the pressure medium. A check valve plate 16, which has check valves 27 for supplying the working chambers 8, 9 hydraulically with the pressure medium, is arranged between the first locking cover 11 and the second locking cover 12. Sprocket toothing, via which the stator 2 can be connected to a chain or a toothed belt to the crankshaft of the internal combustion engine, is furthermore formed on the stator 2 of the hydraulic camshaft adjuster 1.

(9) The two-part locking cover 11, 12 of the central locking device 10 is illustrated on an enlarged scale in FIG. 2. Here, the hydraulic camshaft adjuster 1 can be seen locked in the central position. An aperture 19 for connection of a pressure medium feed duct, via which the locking mechanism of the central locking device 10 can be hydraulically controlled, is provided in the first locking cover 11. A stop 20 for the locking pin 17 of the central locking device 10, which limits a rotation of the rotor 3 in the corresponding direction, is furthermore provided on the first locking cover 11. An insert 21 having a step 22, which is held in position in the axial direction by the check valve plate 16, is inserted into the second locking cover 12. For this purpose, an axial securing means 28, which overlaps at least a section of the insert 21, is formed on the check valve plate 16. In addition, a further stop 26 for the locking pin 17 is formed on the insert 21, resulting in a mechanical ratchet 23 by means of which the rotor 3 can be rotated in steps into the central locking position. The locking pin 17 is pushed into the locking guide slot of the central locking device 10 on the second locking cover 12 by the spring 18, wherein the locking pin 17 blocks a duct 29, illustrated in FIG. 4, for controlling the hydraulic ratchet mechanism when the locking pin 17 is locked in the locking guide slot. Provided on the locking pin 17 is a recess 30, by means of which the duct 29 for controlling the hydraulic ratchet mechanism can be opened when the locking pin 17 is pushed into the rotor 3 by the hydraulic pressure of the pressure medium. The hydraulic ratchet mechanism is thereby deactivated, and the pressure medium can flow out of the corresponding working chambers 8, 9.

(10) A stepped insert 21 is shown in an enlarged illustration in FIG. 3. The insert 21 has a main body with a raised portion 24, by means of which the insert 21 is supported on the check valve plate 16, and a step 22. In this case, a rest 25, by means of which the insert 21 can be supported on the locking cover 12, is provided on the base part. A stop 26 for the locking pin 17, which prevents a rotary motion of the rotor 3 by positive engagement, can furthermore be seen on the insert 21.

(11) A segment of a hydraulic camshaft adjuster 1 is shown in a sectioned three-dimensional illustration in FIG. 4. Here, the rotor 3 has already been locked on one side in the central locking device 10, and the duct 29 to the working chamber 8, 9 is blocked by the locking pin 17. The rotor 3 is in mechanical stop contact, by means of its vane 6, with a ridge 5 of the stator 2.

(12) Another segment of a hydraulic camshaft adjuster 1 is illustrated in FIG. 5, wherein the locking pin 17 rests against a step of the mechanical ratchet 23 but is not yet in the central locking position. The duct 29 for hydraulic control of the working chambers 8, 9 is furthermore blocked by the locking pin 17, and therefore no pressure medium can flow out of the corresponding working chamber 8, 9. Thus, the mechanical ratchet 23 and the hydraulic ratchet mechanism are active simultaneously.

(13) A third illustration of a segment of the hydraulic camshaft adjuster 1 is shown in FIG. 6. In this operating state, the locking pin 17 has been pushed into the rotor 3, with the result that the recess 30 on the locking pin 17 exposes the duct 29 to the working chambers 8, 9, thus ensuring that the pressure medium can flow out of the working chambers 8, 9 and that the hydraulic ratchet mechanism is deactivated. In this case, the rotor 3 is unlocked and freely rotatable, thus providing the operation-related adjusting function of the hydraulic camshaft adjuster 1.

(14) The functioning of the hydraulic ratchet mechanism depends on the oil supply and on the temperature-dependent viscosity of the pressure medium. At low temperatures, the functioning of the hydraulic ratchet mechanism can fail owing to the flow resistances, which are then high. This plays a role especially when an internal combustion engine is shut down unexpectedly, e.g. by stalling, shortly after a cold start, and the hydraulic camshaft adjuster 1 remains unlocked. If the engine is started with cold and thus viscous pressure medium, the hydraulic ratchet mechanism may fail. To cover a failsafe function of the hydraulic camshaft adjuster 1, an additional mechanical ratchet 23 is employed. This comprises a step in which the locking pin 17 can latch in between the end stop positions and the central locking position.

(15) The mechanical ratchet 23 and the hydraulic ratchet can and should contribute simultaneously to the adjustment of the rotor 3 into the central locking position. The hydraulic ratchet acts when the outflow 29 from the working chamber 8, 9 that pushes toward the central position is closed. The locking pin 17 closes this outflow 29 in the locked position. In the intermediate latching position of the mechanical ratchet 23, it continues to be held closed. Because of the locking depth, required for this purpose, through the first locking cover 11, the insert 21 can be of stepped design, or a step 22 can be provided in some other way. The insert 21 in the second locking cover 12 is no longer secured axially against tilting due to shock loads by the extended locking guide slot and the aperture for the connection of the pressure medium supply for hydraulic unlocking of the central locking device 10 in the first locking cover 11. The check valve plate 16 situated between the first locking cover 11 and the second locking cover 12 is therefore used as a securing means.

(16) In the example embodiment illustrated, the mechanical ratchet 23 is formed only in the retarded direction of adjustment from the center and not in the advanced direction of adjustment since in this case no spiral spring is employed to compensate the camshaft friction torque. For adjustment out of the advanced direction of adjustment into the central locking position, the corresponding camshaft friction torque can exert a supportive effect, with the result that no additional mechanical ratchet 23 is required in this direction. In principle, the mechanical ratchet 23 can also be formed in both directions of adjustment and thus on both sides of the central locking position. In this case, an additional stepped insert 21 can be provided and inserted into the second locking cover 12. If the additional mechanical ratchet is used on the same locking pin 17 as the mechanical ratchet 23 illustrated in the embodiment example, the stepped insert should produce a reverse switching logic for the hydraulic ratchet mechanism, with the result that the hydraulic connection 29 to the working chambers 8, 9 is held open in the intermediate latching position. A mechanical ratchet 23 having a plurality of steps and finer gradation associated therewith is furthermore conceivable, wherein a multiple-step insert 21 can be used for this purpose.

(17) In the case of a hydraulic camshaft adjuster 1 according to the disclosure, it is thus possible to improve the rotation of the rotor 3 into the central locking position even at a low temperature and a high viscosity of the pressure medium and thus to ensure operationally reliable locking in the central locking position, irrespective of the external boundary conditions.

LIST OF REFERENCE CHARACTERS

(18) 1 hydraulic camshaft adjuster 2 stator 3 rotor 4 rotor hub 5 ridge 6 vane 7 pressure space 8 working chamber 9 working chamber 10 central locking device 11 first locking cover 12 second locking cover 13 sealing cover 14 first end 15 second end 16 check valve plate 17 locking pin 18 spring 19 aperture (in the first locking cover) 20 stop 21 insert 22 step on the insert 23 mechanical ratchet 24 raised portion 25 rest 26 stop 27 check valve 28 axial securing means 29 duct to hydraulic ratchet 30 recess on locking pin