EP2226476B1 - Hydraulic unit for a cylinder head of a combustion engine with hydraulically variable gas exchange valve drive - Google Patents

Abstract

The unit (5) has a drive-side master unit (6), a driven-side slave unit, a high-pressure chamber, a controllable hydraulic valve (10), a medium-pressure chamber (12) running into a housing bottom part (20). A throttle opening is formed as a part of a hydraulic medium channel passing via a housing middle part (21). The throttle opening runs into a flat housing seal (23) that is arranged as a separate component either between the bottom part or a housing top part (22) and the middle part. A section of the hydraulic medium channel passing via the middle part exhibits a low-throttle construction.

Description

• ■ zumindest eine antriebseitige Gebereinheit,
• ■ zumindest eine abtriebseitige Nehmereinheit,
• ■ zumindest ein ansteuerbares Hydraulikventil,
• ■ zumindest einen Mitteldruckraum,
• ■ zumindest einen Hochdruckraum, der im Übertragungssinn zwischen der zugehörigen Gebereinheit und der zugehörigen Nehmereinheit angeordnet und über das zugehörige Hydraulikventil mit dem zugehörigen Mitteldruckraum verbindbar ist,
• ■ zumindest einen als Hydraulikmittelreservoir dienenden Niederdruckraum, der über eine Drosselöffnung mit dem zugehörigen Mitteldruckraum verbunden ist,
• ■ und ein Hydraulikgehäuse mit einem Gehäuseunterteil, einem Gehäusezwischenteil und einem Gehäuseoberteil,
  wobei die Gebereinheit, die Nehmereinheit, der Hochdruckraum, das Hydraulikventil und der Mitteldruckraum im Gehäuseunterteil verlaufen, der Niederdruckraum im Gehäuseoberteil ausgebildet ist und die Drosselöffnung Teil eines das Gehäusezwischenteil durchsetzenden Hydraulikmittelkanals ist.

The invention relates to a hydraulic unit for a cylinder head of an internal combustion engine with hydraulically variable gas exchange valve train. The hydraulic unit comprises:

• At least one drive-side transmitter unit,
• At least one output-side receiving unit,
• At least one controllable hydraulic valve,
• ■ at least one medium-pressure space,
• At least one high-pressure space, which is arranged in the direction of transmission between the associated transmitter unit and the associated slave unit and can be connected to the associated medium-pressure chamber via the associated hydraulic valve,
• At least one low-pressure space serving as a hydraulic medium reservoir, which is connected via a throttle opening to the associated medium-pressure space,
• ■ and a hydraulic housing with a housing lower part, a housing intermediate part and a housing upper part,
  wherein the transmitter unit, the receiver unit, the high-pressure chamber, the hydraulic valve and the medium-pressure chamber run in the lower housing part, the low-pressure chamber is formed in the upper housing part and the throttle opening is part of the housing intermediate part passing through the hydraulic fluid channel.

Background of the invention

Such a hydraulic unit is from the unpublished EP 2 060 754 A2 (State of the art according to Art. 54 (3) EPC). In the hydraulic unit proposed there are all essential, required for the hydraulically variable transmission of cam lobes on the gas exchange valves components and the pressure chambers in a common hydraulic housing in sandwich construction summarized. The lower housing part is formed very compact design, and in the intermediate housing part is also a substantially flat plate, so that each of the intermediate pressure chambers is limited to a correspondingly small volume.

As explained in the cited document, however, a small-volume medium-pressure chamber during the starting process of the internal combustion engine can be problematic, especially if it is a starting operation at low ambient temperatures and after a long period of stoppage of the internal combustion engine. This is due to the fact that the hydraulic fluid supply of the internal combustion engine still does not promote sufficient hydraulic fluid flow into the medium-pressure space during start-up and only the hydraulic fluid volume remaining in the medium-pressure space and shrunk at low temperatures is insufficiently large for a complete refilling of a then-expanding high-pressure space. This problem applies to a greater extent in a short time repetitive starting operations, since in this case the hydraulic fluid consumption from the medium-pressure space can be greater than the nachgeförderte from the hydraulic fluid supply to the internal combustion engine volume. Such multi-start operations are typical, for example, for taxi cabs at taxi stands.

To solve this problem, it is proposed in the cited document to form in the upper housing part serving as a hydraulic fluid reservoir low-pressure chamber, which has a throttle opening in the intermediate housing part with the medium-pressure space connected is. With the help of the low-pressure chamber on the one hand during the starting process of the engine required hydraulic fluid reservoir for the medium-pressure space and thus expanded for the high-pressure chamber and on the other hand eliminates the risk of suction of gas bubbles as far as possible. The latter results from the intermediate housing part, which separates the low-pressure chamber from the medium-pressure chamber, so that during the stoppage phase of the internal combustion engine and thereby cooling and thus shrinking hydraulic fluid, the formation of gas bubbles in the medium-pressure space is prevented by suction of hydraulic fluid from the low pressure chamber.

However, the expense of producing such a throttle opening in the form of the smallest diameter of a stepped bore amounting to only a few tenths of a millimeter has been found to be disadvantageous due to the housing intermediate part. For example, in the case of a machined bore with high tool wear or frequent tool failure to be expected, while the production by means of laser beam leads to undesirably high shape and cross-sectional deviations of the desired geometry of the throttle opening.

Another hydraulic unit is off DE 10 2006 008 676 A1 known.

Object of the invention

The present invention is therefore based on the object, a hydraulic unit of the type mentioned in such a way that the throttle opening between the medium-pressure chamber and the low-pressure chamber with little effort and at the same time as precisely produced.

Summary of the invention

The solution of this problem arises from the characterizing features of claim 1, while advantageous developments and refinements of the invention are the dependent claims can be removed. Accordingly, it is provided that the throttle opening extends in a housing seal, as a separate Component is arranged either between the lower housing part or the upper housing part on the one hand and the intermediate housing part on the other hand, wherein the intermediate portion of the housing passing through portion of the hydraulic fluid channel is formed throttle-poor. The displacement of the throttle opening from the intermediate housing part in the housing seal leads to a significantly lower production costs, since the throttle opening in particular by punching a single or multi-layer metal seal, as it is often used as such in the cylinder head of internal combustion engines, precise and inexpensive to produce. At the same time, the intermediate housing part is significantly less expensive to produce as a result of its now dropping throttle effect.

In a further development of the invention, the housing seal should be formed as a flat gasket and have a tubular elevation which limits the throttle opening in the manner of a nozzle. The nozzle-like geometry of the throttle opening leads to a pronounced viscosity dependency of the hydraulic fluid volume flow such that the volume flow to be throttled at low temperatures / high-viscosity hydraulic fluid is significantly smaller than at high temperatures / low-viscosity hydraulic fluid. This throttle characteristic is particularly advantageous when the upper housing part is provided with an opening into the cylinder head overflow. This not only serves to vent the low pressure chamber, but also the cooling of the hydraulic unit by escaping heated hydraulic fluid via low pressure chamber in the cylinder head and thus can be returned to the cooled hydraulic fluid circuit of the engine. Here, the viscosity-dependent throttle effect causes a needs-based flushing of the hydraulic unit, which is ideally such that when hot hydraulic fluid flushing the largest possible and cold hydraulic fluid is carried out no rinsing of the hydraulic unit.

The housing seal is expediently arranged between the housing lower part and the housing intermediate part, and the elevation extends into a through-bore in the housing intermediate part Gas bubbles in the medium-pressure space can escape in the best possible way into the low-pressure space.

In addition, a further housing seal may be provided, which is likewise designed as a separate component and is arranged between the lower housing part and the upper housing part on the side facing away from the housing seal of the intermediate housing part. Consequently, the hydraulic unit is sealed by means of separate housing seals in the region of both joints on the intermediate housing part to the environment.

On the one hand, these housing seals may be formed differently from one another so that the section of the hydraulic fluid channel which passes through the further housing seal is of low-throttle design. In other words, the function of the further housing seal in this case is limited to the sealing of the hydraulic unit to the environment.

On the other hand, the housing seal and the further housing seal can also be identical parts. Due to corresponding unit-price effects, further reduced production costs are to be expected. Due to the then double throttle effect is also possible to run the throttle openings with a relatively large cross-section in favor of further improved manufacturability.

Brief description of the drawings

Figur 1

eine schematische Darstellung eines hydraulisch variablen Gaswech- selventiltriebs;

Figur 2

eine erfindungsgemäße Hydraulikeinheit in perspektivischer und teil- weise explodierter Schnittdarstellung;

Figur 3

die Ansicht A gemäß Figur 2 mit zwei voneinander verschiedenen Gehäusedichtungen, wobei die Drosselöffnung blendenartig ausgebil- det ist;

Figur 4

die Ansicht A gemäß Figur 2 mit zwei identischen Gehäusedichtun- gen, wobei die Drosselöffnungen blendenartig ausgebildet sind;

Figur 5

die Ansicht A gemäß Figur 2 mit zwei Gehäusedichtungen, wobei die Drosselöffnung düsenartig und der Durchtritt in der weiteren Gehäu- sedichtung drosselarm ausgebildet sind, und

Figur 5

die Ansicht A gemäß Figur 2 mit zwei Gehäusedichtungen, wobei die Drosselöffnung düsenartig und der Durchtritt in der weiteren Gehäu- sedichtung drosselnd ausgebildet sind.

Further features of the invention will become apparent from the following description and from the drawings, in which embodiments of the invention are shown. Unless otherwise stated, the same or functionally identical features or components are provided with the same reference numbers. Show it:

FIG. 1

a schematic representation of a hydraulically variable gas exchange selventiltriebs;

FIG. 2

a hydraulic unit according to the invention in a perspective and partially exploded sectional view;

FIG. 3

the view A according to FIG. 2 with two mutually different housing seals, wherein the throttle opening is formed like an iris;

FIG. 4

the view A according to FIG. 2 with two identical Gehäusedichtun- gene, wherein the throttle openings are formed like an orifice;

FIG. 5

the view A according to FIG. 2 with two housing seals, wherein the throttle opening nozzle-like and the passage in the further housing seal are formed throttle-poor, and

FIG. 5

the view A according to FIG. 2 with two housing seals, the throttle opening being nozzle-shaped and the passage in the further housing seal being throttled.

Detailed description of the drawings

• ■ eine antriebseitige Gebereinheit 6, hier in Form eines vom Nocken 3 angetriebenen Pumpenstößels 7,
• ■ eine abtriebseitige Nehmereinheit 8, hier in Form eines das Gaswechselventil 4 unmittelbar betätigenden Nehmerkolbens 9,
• ■ ein ansteuerbares Hydraulikventil 10, hier in Form eines elektromagnetischen 2-2-Wege-Schaltventils,
• ■ einen zwischen der Gebereinheit 6 und der Nehmereinheit 8 verlaufenden Hochdruckraum 11, aus dem bei geöffnetem Hydraulikventil 10 Hydraulikmittel in einen Mitteldruckraum 12 abströmen kann,
• ■ ein an den Mitteldruckraum 12 angeschlossener Druckspeicher 13 mit einem federkraftbeaufschlagten Ausgleichskolben 14,
• ■ ein in Richtung des Mitteldruckraums 12 öffnendes Rückschlagventil 15, über das die Hydraulikeinheit 5 an den Hydraulikmittelkreislauf der Brennkraftmaschine angeschlossen ist, und
• ■ einen als Hydraulikmittelreservoir dienenden Niederdruckraum 16, der über eine Drosselöffnung 17 in einer den Niederdruckraum 16 vom Mitteldruckraum 12 separierenden Trennwand 18 mit dem Mitteldruckraum 12 verbunden ist.

In FIG. 1 the basic structure of a hydraulically variable gas exchange valve drive 1 is schematically disclosed. Shown is a section of a cylinder head 2 of an internal combustion engine with a cam 3 of a camshaft and a spring-loaded gas exchange valve 4 which is essential for understanding the invention. The variability of the gas exchange valve drive 1 is generated by means of a hydraulic unit 5 arranged between the cam 3 and the gas exchange valve 4. the following components include:

• A drive-side transmitter unit 6, here in the form of a pump tappet 7 driven by the cam 3,
• ■ an output side slave unit 8, here in the form of a gas piston valve 4 directly actuated slave piston 9,
• ■ a controllable hydraulic valve 10, here in the form of an electromagnetic 2-2-way switching valve,
• ■ a high-pressure space 11 extending between the transmitter unit 6 and the receiver unit 8, from which hydraulic fluid can flow into an intermediate-pressure space 12 when the hydraulic valve 10 is open,
• ■ a pressure accumulator 13 connected to the medium pressure chamber 12 with a compensating piston 14 which is acted upon by a spring force,
• ■ in the direction of the medium-pressure chamber 12 opening check valve 15, via which the hydraulic unit 5 is connected to the hydraulic fluid circuit of the internal combustion engine, and
• ■ a low-pressure space 16 serving as a hydraulic medium reservoir, which is connected to the medium-pressure space 12 via a throttle opening 17 in a partition wall 18 separating the low-pressure space 16 from the medium-pressure space 12.

The known manner of operation of the hydraulic gas exchange valve drive 1 can be summarized to the effect that the high pressure chamber 11 between the transmitter unit 6 and the slave unit 8 acts as a hydraulic linkage, which - neglecting leaks - proportional to the stroke of the cam 3 displaced by the pump plunger 7 hydraulic volume as a function of the opening time and the opening duration of the hydraulic valve 10 in a first, the slave piston 9 acting sub-volume and in a second, in the medium pressure chamber 12 including pressure accumulator 13 effluent partial volume is split. As a result, the stroke transmission of the pump tappet 7 to the slave piston 9 and therefore not only the timing, but also the lifting height of the gas exchange valve 4 are fully variable adjustable.

In the FIG. 2 Cross-section shown hydraulic unit 5 for a 4-cylinder in-line engine has as a further essential part of a common Hydraulic housing 19, so that the hydraulic unit 5 can be mounted as a preassembled and possibly already filled with hydraulic fluid assembly in the cylinder head 2 of the internal combustion engine. The composite in sandwich construction hydraulic housing 19 consists of a lower housing part 20, a housing intermediate part 21 and a housing upper part 22. To seal the parting line between the housing base 20 and housing intermediate part 21 extends a housing seal 23, and for sealing the parting line between the housing intermediate part 21 and upper housing part 22 extends a further housing seal 24. Both seals 23, 24 are separate components in the form of single-layer metal seals. The housing parts 20, 21, 22 are screwed together hydraulically sealingly at various screwing points 25. For fixing the entire hydraulic unit 5 in the cylinder head 2 of the internal combustion engine, the lower housing part 20 separate Verschraubungspunkte 26 on.

The four transmitter units 6 extending in the housing lower part 20 each include the pump plunger 7, which is spring-loaded in the return stroke direction and which is driven by a cam-operated drag lever, not shown here. The pivotable mounting of the drag levers takes place by means of support elements 27, which are also accommodated in the lower housing part 20. From the intermediate housing part 21 outgoing bracket 28, serve as a captive for the drag lever with not mounted in the cylinder head 2 hydraulic unit 5. This is further designed so that each of the transmitter units 6 with two extending in the housing base 20 slave units 8 (see FIG. 1 ) cooperates. In other words, only one cam 3 and one transmitter unit 6 are required for each pair of identical gas exchange valves 4, ie intake valves or exhaust valves of a cylinder of the internal combustion engine, wherein the hydraulic volume displaced by the pump tappet 7 simultaneously acts on both slave units 8.

On the side facing the transmitter units 6 side of the hydraulic unit 5, the respective one encoder unit 6 and the two slave units 8 associated hydraulic valves 10 can be seen with electrical connectors 29. In the de-energized state, the medium-pressure chamber 12 with the high-pressure chamber 11 (see FIG. 1 ) connecting hydraulic valves 10 are fixed in a known per se and not shown here in valve receptacles in the housing base 20. Further recognizable is the pressure accumulator 13 connected to the medium-pressure chamber 12 with the compensating piston 14 which is acted on by spring force.

Each serving as a hydraulic fluid reservoir for the associated medium-pressure chamber 12 low-pressure spaces 16 are formed by bulges in the upper housing part 22, which is made by deep-drawing of sheet steel. Like it out FIG. 3 as an enlarged view A clearly shows, the low-pressure chamber 16 and the medium-pressure chamber 12 are connected to each other via a hydraulic fluid channel, which extends through the housing seals 23, 24 and the intermediate housing part 21. As a partition 18 according to FIG. 1 is used between the housing base 20 and housing intermediate part 21 inserted housing seal 23 with punched throttle opening 17 ', which has a diameter of about 0.4 mm. The further housing seal 24 between housing intermediate part 21 and housing upper part 22 differs from the housing seal 23 in that its passage 30 as well as the through bore 31 in the housing intermediate part 21 has a multiple of the cross section of the throttle opening 17 '. The passage 30 and the easy-to-produce through-hole 31 thus represent throttle-poor portions of the hydraulic fluid channel.

One too FIG. 3 alternative embodiment of the housing seals is in FIG. 4 shown. In this case, the housing seal 23 and the further housing seal 24 are designed as identical parts, so that the hydraulic medium channel passing through the intermediate housing part 21 and connecting the low-pressure chamber 16 with the medium-pressure chamber 12 has two throttling sections. In order to the same throttle effect as in the embodiment according to FIG. 3 The diameter of the likewise punched throttle openings 17 "is clearly more than 0.4 mm. The throttle-poor through-bore 31 in the intermediate housing part 21 is unchanged compared to the aforementioned exemplary embodiment.

In the FIGS. 5 and 6 Further embodiments of inventive housing seals 23 and 24 are shown. In contrast to the merely punched out throttle openings 17 ', 17 ", the length of the comparatively small material thickness of the housing seals 23 and 24 corresponds and their throttle characteristic thus resembles that of a viscous iris independent, the throttle opening 17"' limited by a tubular elevation 33 of the housing seal 23 , The elevation 33 produced in a deep-drawing step and extending into the through-bore 31 by a multiple of the material thickness of the housing seal 23 causes the throttle opening 17 "'to assume the geometry of a viscosity-dependent and laminar-flow nozzle FIGS. 5 and 6 Embodiments shown differ only in that the further housing seal 24 according to either the throttle-poor passage 30 FIG. 3 or the orifice-type throttle opening 17 "connected in series with the throttle opening 17"'in FIG FIG. 4 having.

Although in the Figures 2 and 3 only one hydraulic fluid channel with throttle opening 17 'is shown, each medium-pressure chamber 12 may also be connected via two or more such hydraulic fluid channels to the associated low-pressure chamber 16. It is also conceivable to associate each of two medium-pressure chambers 12 with two or more low-pressure chambers 16 separated from one another. This applies in a corresponding manner to the alternative embodiments according to the FIGS. 4 to 6 ,

As in the FIGS. 1 and 2 can be gas bubbles, which pass through the throttle opening 17 from the medium-pressure chamber 12 in the low-pressure chamber 16 during operation of the internal combustion engine, via a running in the upper housing part 22 and opening into the cylinder head 2 vent 32 are deposited in the interior of the cylinder head 2. This also applies to excess hydraulic fluid, in which case the vent opening 32 serves as an overflow.

List of reference numbers

1

Gas exchange valve train

2

cylinder head

3

cam

4

Gas exchange valve

5

hydraulic unit

6

transmitter unit

7

pump plunger

8th

receiver unit

9

slave piston

10

hydraulic valve

11

High-pressure chamber

12

Medium-pressure chamber

13

accumulator

14

balance piston

15

check valve

16

Low-pressure chamber

17

throttle opening

18

partition wall

19

hydraulic housing

20

Housing bottom

21

Intermediate housing part

22

Housing top

23

housing seal

24

additional housing seal

25

screw fixing

26

screw fixing

27

supporting

28

hanger

29

Connector of the hydraulic valve

30

Passage in the other housing seal

31

Through hole in the intermediate housing part

32

vent

33

survey

Claims (7)

1. Hydraulic unit (5) for a cylinder head (2) of an internal combustion engine having a hydraulically variable gas-exchange valve timing mechanism (1), comprising

   ■ at least one drive-side transmitter unit (6),

   ■ at least one output-side receiver unit (8),

   ■ at least one actuable hydraulic valve (10),

   ■ at least one medium-pressure space (12),

   ■ at least one high-pressure space (11) which is arranged in the transmission direction between the associated transmitter unit (6) and the associated receiver unit (8) and can be connected via the associated hydraulic valve (10) to the associated medium-pressure space (12),

   ■ at least one low-pressure space (16) which is connected via a throttle opening (17, 17', 17'', 17"') to the associated medium-pressure space (12),

   ■ and a hydraulic housing (19) having a lower housing part (20) and an intermediate housing part (21),
   the throttle opening (17, 17', 17", 17"') being part of a hydraulic-medium channel which penetrates the intermediate housing part (21), and the transmitter unit (6), the receiver unit (8), the high-pressure space (11), the hydraulic valve (10) and the medium-pressure space (12) extending in the lower housing part (20), characterized in that the hydraulic housing (19) has an upper housing part (22), the low-pressure space (16) is formed in the upper housing part (22) and serves as hydraulic-medium reservoir, and the throttle opening (17, 17', 17", 17"') extends in a housing seal (23) which is arranged as a separate component either between the lower housing part (20) or the upper housing part (22) on one side and the intermediate housing part (21) on the other side, that section of the hydraulic-medium channel which penetrates the intermediate housing part (21) being configured with a low throttling action.
2. Hydraulic unit (5) according to Claim 1, characterized in that the housing seal (23) is configured as a flat seal and has a tubular elevation (33) which delimits the throttle opening (17"') in the manner of a nozzle.
3. Hydraulic unit (5) according to Claim 2, characterized in that the housing seal (23) is arranged between the lower housing part (20) and the intermediate housing part (21), the elevation (33) extending into a through hole (31) in the intermediate housing part (21).
4. Hydraulic unit (5) according to Claim 1, characterized in that a further housing seal (24) is provided which is arranged as a separate component between the lower housing part (20) and the upper housing part (22) on that side of the intermediate housing part (21) which faces away from the housing seal (23).
5. Hydraulic unit (5) according to Claim 4, characterized in that the housing seal (23) and the further housing seal (24) are configured differently from one another, that section of the hydraulic-medium channel which penetrates the further housing seal (24) being configured with a low throttling action.
6. Hydraulic unit (5) according to Claim 4, characterized in that the housing seal (23) and the further seal (24) are identical parts.
7. Hydraulic unit (5) according to Claim 1, characterized in that the housing seal (23) is a single-layer or multiple-layer metal seal.

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