EP2331797B1 - Device for variably adjusting the control times of gas exchange valves of an internal combustion engine - Google Patents

Description

Field of the invention

The invention relates to a device for variably setting the timing of gas exchange valves of an internal combustion engine with a hydraulic phase adjusting device, a camshaft and a pressure accumulator, wherein the phase adjusting device can be brought into drive connection with a crankshaft and rotatably connected to the camshaft, wherein a phase angle of the camshaft relative to Crankshaft is variably adjustable by means of the phase adjusting device and wherein the interior of the camshaft has a cavity.

Background of the invention

In modern internal combustion engines devices for variable adjustment of the timing of gas exchange valves are used to make the phase relation between the crankshaft and the camshaft in a defined angular range, between a maximum early and a maximum late position variable. The device usually consists of a camshaft and a hydraulic phase adjusting device, by means of which a phase relation between the crankshaft and the camshaft can be selectively changed by pressure medium supply or removal. For this purpose, the phase adjusting device is integrated in a drive train, via which torque is transmitted from the crankshaft to the camshaft. This drive train can be realized for example as a belt, chain or gear drive.

Such a device is for example from the DE 195 29 277 A1 known. The device comprises a phase adjusting device and a camshaft. The phase adjusting device has an output element, which is arranged rotatably to a drive element. The drive element is in drive connection with the crankshaft. The output element and the drive element define a pressure chamber, which is divided by means of an axially displaceable piston into two counteracting pressure chambers. By supplying pressure medium to or removing pressure medium from the pressure chambers, the piston is displaced within the pressure chamber. The piston has a helical toothing, which meshes with a helical toothing of the camshaft. By an axial displacement of the piston thus a targeted rotation of the camshaft can be effected to the crankshaft.
The device further comprises a pressure accumulator, which is arranged in a crankcase or a cylinder head of the internal combustion engine. During normal operation of the internal combustion engine, the pressure accumulator of a pressure medium pump of the internal combustion engine with pressure medium, usually the engine oil, filled. If the system pressure delivered by the pressure medium pump drops below a value which is required for the functionally reliable operation of the device, the pressure accumulator empties into the pressure medium circuit of the internal combustion engine. Thus, short-term minimum pressure drops can be intercepted within the pressure fluid system or the flow rate can be increased.
A disadvantage of this embodiment, the high space requirement of the pressure accumulator within the crankcase and the cylinder head.

The DE 102 28 354 A1 1 shows a camshaft with a camshaft adjusting device. Within the camshaft, an accumulator and a pressure generating device is arranged. The pressure generating device can be operated with a nitrogen tablet. The pressurized fluid under pressure in the accumulator (oil) can be fed to the camshaft adjusting device.

The US 2003/0188705 A1 shows a hydraulic circuit with a pressure accumulator 114, a pump 102, a proportional valve 68, various hydraulic fluid lines and a camshaft 73, on the front side a camshaft adjuster 83 is attached.

Object of the invention

The invention has for its object to provide a device for variable adjustment of the timing of gas exchange valves of an internal combustion engine, the space requirement of the device to be reduced.

The object is achieved in that the pressure accumulator is arranged in the cavity and communicates with the phase adjusting device.

The device has at least one hydraulic phase adjusting device on a camshaft and a pressure accumulator. The phase adjusting device comprises at least one drive element and an output element. The drive element is in the assembled state of the device via a traction drive, such as a belt or chain drive or a gear drive, with the crankshaft in drive connection. The output member is pivotally mounted in an angular range relative to the drive element and rotatably secured to the camshaft.
Within the device, at least one pressure chamber is provided by the pressurization of which the output element relative to the drive element and thus the camshaft can be pivoted relative to the crankshaft. Advantageously, one or more pairs of mutually acting pressure chambers are provided.
The camshaft has a cavity. This can be formed for example as a hollow shaft. Likewise conceivable are embodiments in which the camshaft consists of a tube on the outer lateral surface of cam force, are positively or materially secured. But also conceivable are solidly executed camshafts in which a cavity, for example in the form of a blind hole, is provided. In the cavity the camshaft, the pressure accumulator is arranged. The pressure accumulator can be connected, for example, positive, non-positive or cohesive, stationary with the camshaft.
The interior of the camshaft can be supplied for example via a camshaft bearing pressure medium. The pressure medium passes on the one hand to the hydraulic phase adjusting device, on the other hand to the pressure accumulator, which is filled with pressure medium during normal operation of the internal combustion engine. At the beginning of a phase adjustment of the pressure fluid system of the internal combustion engine is removed a certain amount of pressure medium. As a result, the system pressure drops to a lower level. The existing system pressure prior to adjustment is not fully available for phase adjustment. Thus, the adjustment speed of the phase adjustment and thus the performance of the entire internal combustion engine decreases. This pressure drop is intercepted with filled pressure accumulator through this, the adjustment speed is maintained at a high level. The arrangement of the accumulator within the camshaft, an otherwise unused space, the space requirement of the internal combustion engine is significantly reduced.

The pressure accumulator has a longitudinally displaceable piston. Furthermore, the pressure accumulator may have a spring element, which acts on the piston against the force of the pressure medium with a force. Alternatively, for example, gas cushions can be provided as energy storage. The pressure accumulator can be designed, for example, as a piston accumulator, in particular as a piston spring accumulator. This is a very robust solution.

In a further development of the invention it is provided that the pressure accumulator has a housing which is arranged in the cavity and in which the piston is guided longitudinally displaceable. Thus, a wall of the cavity of the camshaft must not be reworked consuming. The running surface of the piston is represented by an inner circumferential surface of the housing. The housing can be realized, for example, as a cylindrical or cup-shaped sheet metal part which can be produced, for example, by a non-cutting shaping process, for example by a deep drawing process. As a result, the weight and the manufacturing cost of the housing are kept low. The deep-drawing process automatically produces the running surface of the piston with the required accuracy. Elaborate post-processing steps are not necessary

Furthermore, it can be provided, the pressure accumulator is arranged by means of a frictional connection between the housing and a wall of the cavity in this stationary. Alternatively, fabric or positive connections, such as adhesive, solder or welded joints can be provided.

In a concretization can be provided that the housing has a guide portion and the piston has an outer circumferential surface which is adapted to an inner circumferential surface of the guide portion. The piston is guided axially movably on a guide surface of the guide section. The length of the guide section corresponds to the stroke of the piston within the pressure accumulator. The guide portion may extend over the entire length of the piston, for example. In this embodiment it can be provided that the frictional connection between the housing and the wall of the cavity along the entire length of the guide portion is formed, whereby the connection receives a high stability. For this purpose, the outer circumferential surface of the wall of the cavity is adapted. Alternatively it can be provided that the housing has an enlarged diameter at both axial ends of the guide portion, the outer circumferential surfaces of the wall of the cavity are adapted. Thus, there is a frictional connection only between the enlarged diameter portions and the wall of the cavity. This avoids deformation of the guide surface during assembly of the pressure accumulator in the cavity, which could lead to jamming of the piston in the housing.

Furthermore, it can be provided that the housing has, at least in one direction of displacement of the piston, advantageously in both, at least one stop for limiting the travel of the piston. Furthermore, it can be provided that the camshaft is tubular.

Brief description of the drawings

Figur 1

nur sehr schematisch eine Brennkraftmaschine,

Figur 2

einen Längsschnitt durch eine erste erfindungsgemäße Ausführungsform einer Vorrichtung zur Veränderung der Steuerzeiten von Gaswechselventilen einer Brennkraftmaschine,

Figur 3

einen Querschnitt durch die Phasenstelleinrichtung aus Figur 2 entlang der Linie III-III, wobei die Zentralschraube nicht dargestellt ist,

Figuren 4,5

die Einzelheit X aus Figur 2,

Figur 6

eine Darstellung einer weiteren erfindungsgemäßen Ausführungsform einer Vorrichtung analog zu Figur 4.

Further features of the invention will become apparent from the following description and from the drawings in which embodiments of the invention are shown in simplified form. Show it:

FIG. 1

only very schematically an internal combustion engine,

FIG. 2

a longitudinal section through a first embodiment according to the invention of a device for changing the timing of gas exchange valves of an internal combustion engine,

FIG. 3

a cross section through the phase adjusting device FIG. 2 along the line III-III, with the central screw not shown,

Figures 4,5

the detail X out FIG. 2 .

FIG. 6

a representation of another embodiment of the invention a device analogous to FIG. 4 ,

Detailed description of the drawings

In FIG. 1 an internal combustion engine 1 is sketched, wherein a seated on a crankshaft 2 piston 3 is indicated in a cylinder 4. The crankshaft 2 is in the illustrated embodiment via a respective traction drive 5 with an intake camshaft 6 and exhaust camshaft 7 in combination, wherein a first and a second device 11 for a relative rotation between Crankshaft 2 and the camshafts 6, 7 can provide. Cams 8 of the camshafts 6, 7 actuate one or more inlet gas exchange valves 9 or one or more Auslassgaswechselventile 10. Likewise, it may be provided only one of the camshafts 6, 7 with a device 11, or provide only a camshaft 6, 7, which with a Device 11 is provided.

The Figures 2 and 3 show a first embodiment of a device 11 according to the invention in longitudinal or in cross section. The device 11 has a phase adjusting device 12, a camshaft 6, 7 and a pressure accumulator 15.
The phase adjusting device 12 comprises a drive element 14, an output element 16 and two side covers 17, 18, which are arranged on the axial side surfaces of the drive element 14. The output element 16 is designed in the form of an impeller and has a substantially cylindrical hub member 19, extend from the outer cylindrical surface in the illustrated embodiment, five wings 20 in the radial direction outwardly.
Starting from an outer circumferential wall 21 of the drive element 14, five projections 22 extend radially inwards. In the illustrated embodiment, the projections 22 and the wings 20 are integrally formed with the peripheral wall 21 and the hub member 19, respectively. The drive element 14 is arranged by means of radially inner circumferential walls of the projections 22 relative to the output member 16 rotatable thereto.

On an outer circumferential surface of the drive element 14, a sprocket 23 is formed, via which by means of a chain drive, not shown, torque can be transmitted from the crankshaft 2 to the drive element 14. The output member 16 is rotatably connected to the camshaft 6,7. For this purpose, in the illustrated embodiment, a central screw 13 passes through a central opening 16a of the output element 16 and engages in a threaded portion 25 of the camshaft 6, 7 a. In this case, a shoulder of the central screw 13 is located on the camshaft 6, 7 facing away from the side surface of the output element 16 at.

Depending on one of the side covers 17, 18 is disposed on one of the axial side surfaces of the drive member 14 and rotatably fixed thereto. For this purpose, an axial opening 26 is provided in each projection 22. Furthermore, five openings each are provided in the side covers 17, 18, which are arranged such that they are aligned with the axial openings 26. In each case, a screw 27 passes through an opening of the second side cover 18, an axial opening 26 and an opening of the first side cover 17. In this case engages a threaded portion of the screw 27 in a threaded portion which is formed in the opening of the first side cover 17.

Within the device 11, a pressure space 28 is formed between each two circumferentially adjacent projections 22. Each of the pressure chambers 28 is circumferentially bounded by opposing, substantially radially extending boundary walls 29 of adjacent projections 22, in the axial direction of the side covers 17, 18, radially inwardly of the hub member 19 and radially outwardly of the peripheral wall 21. In each of the pressure chambers 28 projects a wing 20, wherein the wings 20 are formed such that they rest against both the side covers 17, 18, and on the peripheral wall 21. Each wing 20 thus divides the respective pressure chamber 28 into two counteracting pressure chambers 30, 31.

The output element 16 is arranged rotatably in a defined Winkelbreich to the drive element 14. The angular range is limited in one direction of rotation of the driven element 16 in that the wings 20 come into contact with a corresponding boundary wall 29 (early stop 32) of the pressure chambers 28. Similarly, the angular range in the other direction of rotation is limited by the fact that the wings 20 come to rest on the other boundary walls 29 of the pressure chambers 28, which serve as a late stop 33.
By pressurizing a group of pressure chambers 30, 31 and pressure relief of the other group, the phase position of the drive element 14 to the output element 16 (and thus the phase angle of the camshaft 6, 7 to the crankshaft 2) are varied. By pressurizing both groups of pressure chambers 30, 31, the phase position can be kept constant.

In the region of a camshaft bearing 39, the camshaft 6, 7 has a plurality of openings 35, via which pressure medium conveyed by a pressure medium pump 48 passes into its interior. Within the camshaft 6, 7, a pressure medium path 36 is formed, which communicates on the one hand with the openings 35 and on the other hand with the control valve 34. To supply the phase adjusting device 12 with pressure medium, a control valve 34 is arranged in the interior of the central screw 13. By means of the control valve 34 pressure medium can be selectively directed to the first or second pressure chambers 30, 31 and discharged from the respective other pressure chambers 30, 31.

Inside the central screw 13, a pressure medium channel 37 is provided which communicates on the one hand with the pressure medium path 36 and on the other hand with a cavity 38 of the hollow camshaft 6, 7. The pressure medium channel 37 is formed as an axial bore, which passes through the threaded portion of the central screw 13.
In the cavity 38 of the pressure accumulator 15 is arranged. In the FIGS. 4 and 5 is the accumulator in the filled ( FIG. 4 ) or in the deflated state ( FIG. 5 ). The pressure accumulator 15 comprises a housing 40, a piston 41 and a force accumulator, in the illustrated embodiment, a spring element 42. The housing 40 is disposed within the cavity 38 and fixedly connected to a wall 43 of the cavity 38. In the illustrated embodiment, the outer surface of the housing 40 of the wall 43 is adapted and non-positively connected thereto. Also conceivable are embodiments in which the housing 40 is connected to the wall 43 in a material or form-fitting manner. In addition, the housing 40 can be fixed by means of a securing ring 24.
In the interior of the housing 40, the piston 41 is arranged axially displaceable, wherein this is cup-shaped in the illustrated embodiment.

The entire housing 40 serves as a guide portion 44, wherein an inner circumferential surface of the guide portion 44 is formed as a guide surface 45 for a cylindrical portion of the piston 41. In this case, the cylindrical portion of the piston 41 completely or partially abut the guide surface 45. The outer circumferential surface of the piston 41 is adapted to the guide surface 45 such that it separates the housing 40 pressure medium-tight in two areas axially in front of and behind the bottom of the piston 41. The piston 41 is acted upon by means of the spring element 42, which is arranged in the region of the cylindrical portion with a force. The spring element 42 is supported, on the one hand, on a stop 46, which is formed on the end of the housing 40 facing away from the phase adjusting device 12, and on the other hand on the bottom of the piston 41. Thus, the spring element 42 acts on the piston 41 with a force in the direction of the pressure medium channel 37. In this case, the displacement of the piston 41 is limited in the direction of the pressure medium channel 37 by a stop 46 which is formed on the phase adjusting device 12 facing the end.
In the illustrated embodiment, the housing 40 and the piston 41 are formed as sheet metal parts, which are made for example by a non-cutting manufacturing process, such as a deep drawing process. This has the advantage that the guide surface 45 and the cylindrical portion of the piston 41 can be produced so precisely by this shaping process that they do not have to be reworked. The use of the housing 40 also eliminates costly post-processing steps of the wall 43 of the cavity 38.

In FIG. 6 a second embodiment of a pressure accumulator 15 is shown. This has the difference from the first embodiment in that the guide portion 44 does not extend over the entire axial length of the housing 41 and does not abut the wall 43 of the cavity 38. The guide section 44 is adjoined in the axial direction by an enlarged area 47. In this case, the outer circumferential surfaces of the enlarged diameter portions 47 of the wall 43 are adapted. Thus, the non-positive connection between the housing 40 and wall 43 is only in Area of the diameter-enlarged areas 47 before. As a result, deformation of the guide surface 45 during the press-fitting operation of the housing 40 into the cavity 38 is avoided.

During operation of the internal combustion engine 1, pressure medium is passed from the pressure medium pump 48 via the openings 35, the pressure medium path 36 and the control valve 34 to the phase adjusting device 12. Furthermore, pressure medium is conducted via the openings 35, the pressure medium path 36, the pressure medium channel 37 and a housing opening 50 in the housing 40. The pressure medium acts on the piston 41 with a force, whereby it is axially displaced against the force of the spring element 42. The accumulator 15 is filled ( FIG. 4 ). If the system pressure delivered by the pressure medium pump 48 drops, the force of the pressure medium on the piston 41 drops, as a result of which it is displaced by the spring element 42 in the direction of the pressure medium channel 37 and thus supplies pressure medium to the system. Due to a check valve 49, the pressure medium is prevented from flowing back into the pressure medium system and thus is completely available to the phase adjusting device 12, whereby its responsiveness and the adjustment speed are maintained at a high level.

reference numeral

1

Internal combustion engine

2

crankshaft

3

piston

4

cylinder

5

traction drive

6

intake camshaft

7

exhaust

8th

cam

9

Inlet gas exchange valve

10

Auslassgaswechselventil

11

contraption

12

Phase adjustment device

13

central screw

14

driving element

15

accumulator

16

output element

16a

central opening

17

side cover

18

side cover

19

hub element

20

wing

21

peripheral wall

22

head Start

23

Sprocket

24

circlip

25

threaded portion

26

axial opening

27

screw

28

pressure chamber

29

boundary wall

30

first pressure chamber

31

second pressure chamber

32

early stop

33

late stop

34

control valve

35

openings

36

Pressure fluid conduit

37

Pressure fluid channel

38

cavity

39

camshaft bearings

40

casing

41

piston

42

spring element

43

wall

44

guide section

45

guide surface

46

attack

47

Area

48

Hydraulic pump

49

check valve

50

housing opening

Claims (7)

1. Device (11) for variably adjusting the control times of gas exchange valves (9, 10) of an internal combustion engine (1) having

   - a hydraulic phase setting device (12), a camshaft (6, 7) and a pressure accumulator (15),

   - it being possible for the phase setting device (12) to be brought into a drive connection with a crankshaft (2), and said phase setting device (12) being connected fixedly to the camshaft (6, 7) so as to rotate with it,

   - a phase relation of the camshaft (6, 7) relative to the crankshaft (2) being variably adjustable by means of the phase setting device (12), and

   - the interior of the camshaft (6, 7) having a cavity (38),

   - the pressure accumulator (15) being arranged in the cavity (38) and communicating with the phase setting device (12),

   - the pressure accumulator (15) having a longitudinally displaceable piston (41), characterized in that the pressure accumulator (15) has a housing (40) which is arranged in the cavity (38) and in which the piston (41) is guided such that it can be displaced longitudinally.
2. Device (11) according to Claim 1, characterized in that the pressure accumulator (13) has a spring element (42) which loads the piston (41) with a force counter to the force of the pressure medium.
3. Device (11) according to Claim 1, characterized in that, at least in one displacement direction of the piston (41), the housing (40) has at least one stop (46) for limiting the travel of the piston (41).
4. The device (11) according to Claim 1, characterized in that the pressure accumulator (15) is arranged in a stationary manner in the cavity (38) between the housing (40) and a wall (43) of said cavity (38) by means of a nonpositive connection.
5. Device (11) according to Claim 1, characterized in that the housing (40) has a guide section (44) and the piston (41) has an outer circumferential face which is adapted to an inner circumferential face of the guide section (44).
6. Device (11) according to Claim 5, characterized in that the guide section (44) extends over the entire length of the piston (41).
7. Device (11) according to Claim 5, characterized in that, at both axial ends of the guide section (44), the housing (40) has a region (47) of increased diameter, the outer circumferential faces of which are adapted to the wall of the cavity (38).

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