WO2003102383A1 - Hydraulically actuated, variable valve gear of an internal combustion engine - Google Patents

Abstract

The invention relates to a hydraulically actuated, variable valve gear (1) of an internal combustion engine, comprising a master piston (3), which is in contact with a cam (2), a slave piston (5) that acts on a gas exchange valve (4) and a pressure chamber (6) of variable volume that is positioned between the master and the slave pistons (3, 5). The chamber is intersected by a path (7) for supplying and selectively draining hydraulic fluid, said path being subjected to the action of a switching element (8), such as an electromagnet for influencing the pressure of the hydraulic fluid. A secondary path (9) branches from the path (7) to a pressure accumulator (10), the latter (10) comprising a piston (12) in the direction of flow of the path (7) that is subjected to the action of a spring element (11). The invention is characterised in that the path (7) is connected to a hydraulic fluid reservoir (13), which consists of a pot-type element (14) comprising a non-return valve (16) on its base (15) that faces the path (7). Said valve opens in the direction of the path (7) and closes in the direction of flow to an inner chamber (18) that is surrounded by the wall (17) of the element (14). An intentional passage (21) in the form of a leakage gap is configured starting from one side of the path (19) of the element (14) and running radially between the wall (17) and a guide (20) for said element (14), said passage supplying the hydraulic fluid from the path (7) to the inner chamber (18), where it accumulates. This configuration permits the provision of a valve gear (1), which prevents the intake of air into the pressure chamber (6) of the valve gear, during the operation of the internal combustion engine.

Description

 Name of the invention

Hydraulically operated, variable valve train of an internal combustion engine

Field of the Invention

The invention relates to a hydraulically operated, variable valve train of an internal combustion engine, with a master piston contacted by a cam, a slave piston acting on a gas exchange valve, a variable pressure chamber positioned between the master and slave pistons, which can be changed by a path for supplying and optionally discharging the hydraulic medium is cut, which is acted upon by a switching means such as an electromagnet for influencing pressure on hydraulic medium, a path branching off from the path to a pressure accumulator, which pressure accumulator has a piston acted upon in the flow direction to the path by a spring means.

Background of the Invention

Such a valve train is evident from EP 0 803 642, which is considered to be generic. Its pressure accumulator is installed vertically in a support for the valve train on the internal combustion engine. How adequately Knows, in such valve drives to achieve partial or zero strokes during a stroke phase of the corresponding cam hydraulic fluid is derived from the pressure chamber by an open electromagnetic switching means. A pressure accumulator largely takes up this hydraulic fluid and returns it to the pressure chamber when it is enlarged.

In particular after the internal combustion engine has been switched off, it can be ascertained during refiring that the piston of the pressure accumulator sinks to its lower stop due to the force of the spring means acting on it and due to the unavoidable leaks in hydraulic fluid. Some of the cams of the internal combustion engine are in the lifting position. This means that the master piston has moved relatively far into the pressure chamber, the corresponding gas exchange valve remaining closed. When the corresponding cam rotates for the first time, the adjacent master piston follows it into the base circle. This increases the volume of the pressure chamber and there is a risk that air or air-oil foam is sucked into the pressure chamber, since the pressure accumulator is virtually empty and at the same time a hydraulic medium pump is not yet or does not deliver hydraulic medium in sufficient quantity. This can lead to a massive malfunction in the valve train.

Object of the invention

The object of the invention is therefore to provide a valve train of the aforementioned type in which the disadvantages cited are eliminated.

Summary of the invention

According to the invention, this object is achieved in that the path is connected to a hydraulic fluid reservoir, which consists of a pot-like element with a check valve arranged on its bottom facing the path, which opens in the direction of the path and in the direction of flow to one of a wall of the element covered interior closes, where, starting from a path side of the element, radially between the wall and a guide for the element, a desired passage is formed like a leakage gap for supplying the hydraulic medium from the path for accumulation in the interior.

The disadvantages described at the outset are thus eliminated with simple means, since a leak-proof hydraulic fluid reservoir is available which, after the internal combustion engine has been switched off and fired again, immediately guarantees a sufficient quantity of hydraulic fluid. As a result, the pressure chamber of the valve train is completely supplied with hydraulic fluid from the first cam rotation and no air is sucked in. As said, this problem occurs in the prior art in particular in the case of the valves whose cams and thus the master pistons are at a stroke.

It is conceivable and envisaged that the pressure and hydraulic fluid reservoir form separate units. In particular, however, it is provided that both are designed as one structural unit. This unit is advantageously positioned as close as possible to the pressure chamber.

Of course, the scope of the invention also includes a valve train in which at least one of the links mentioned in the main claim is present multiple times.

Instead of the leakage gap for supplying the hydraulic medium into the interior of the element, further passages such as bypasses, lines, bores, channels, etc. are opened up to the person skilled in the art.

Of course, the specialist designs the interior of the element to be large enough to prevent air from being sucked into the pressure chamber under all circumstances. It is proposed that the storage volume be made at least 1.2 times as large as the volume that is displaced when the master piston is moved. Possibly. significantly larger volumes are also conceivable. It is also particularly advantageous if the piston of the pressure accumulator and the element of the hydraulic fluid accumulator run "connected in series" within a guide. The housing is therefore to be regarded as a guide, which in the prior art merely accommodates the piston of the pressure accumulator.

A helical spring or the like is advantageously used as the compression spring for the spring means, and further pressure-exerting means can also be provided.

The cup-shaped body for the guide embodied in a further development of the invention can consist, for example, of a thin-walled, deep-drawn sheet metal material. Possibly. machining is also conceivable. It is envisaged, on the one hand, to design the guide for the common component from a separate component which projects beyond a support of the valve train. It is equally conceivable and envisaged, however, to form the guide itself by accommodating the carrier. This may reduce the number of components.

According to a further development of the invention, the check valve on the underside of the piston / base consists only of a ball which is held in the opening direction by a spring cap or the like. Thus, no compression spring is proposed, which fixes the ball as a closing body on the passage of the piston or base when the pressure is equal.

However, since certain structural designs can lead to the leakage of the overall system when the internal combustion engine is at a standstill, it can also be advantageous to prevent the interior of the element from leaking if the pressure is equal. The closing body can thus also be spring-loaded. Instead of the ball valve, other valve types such as plate valves etc. can also be used. If the ball valve is not spring-loaded, it is clear that the ball immediately releases a sufficient cross-section at the passage at the lowest path-side negative pressure and thus the necessary amount of hydraulic fluid can flow from the interior into the pressure chamber.

When using the spring means for the closing body, it is provided that the latter opens at a path-side negative pressure of approximately 0.01 to 0.5 bar. Thus, on the one hand, the aforementioned leakage is prevented, on the other hand, a sufficiently quick opening is guaranteed.

Of course, the structural unit does not have to be arranged parallel to the vertical. An inclined, flat or overhead installation of the aforementioned unit is also conceivable. Possibly. Suitable ventilation lines must be arranged on the system to prevent an undesirable accumulation of air in the storage tank.

Due to the outlet for hydraulic fluid in the floor of the guide, it is guaranteed that, when the interior is filled, excess hydraulic fluid that is constantly generated due to the delivery of the hydraulic fluid pump and the leaks inherent in the system is discharged.

Brief description of the drawing

The invention is expediently explained in more detail with reference to the drawing. Show it:

Figure 1 is a schematic view of the variable valve train and

Figures 2, 3 the pressure accumulator, which according to the invention from a

Unit is made with the hydraulic fluid reservoir. Detailed description of the drawing

Figure 1 discloses a hydraulically operated, variable valve train 1 of an internal combustion engine. This has a master piston 3 acted upon by a cam 2, to which a pressure chamber 6 of variable volume is arranged in the stroke direction. The pressure chamber 6 is cut by a path 7 for the supply and optional discharge of the hydraulic medium. A slave piston 5 is arranged on the valve side, which acts directly on the gas exchange valve 4 in the stroke direction. An electromagnetic switching means 8, which cannot be explained in greater detail, communicates with the path 7, via which hydraulic medium can be derived from the pressure chamber 6.

FIG. 1 further shows that a secondary path 9 branches off from path 7. This leads to a piston 12 which is acted upon in the flow direction to the path 7 by a spring means 11. In this pressure accumulator 10, as already stated in the introduction to the description, the hydraulic medium is received, which flows out of the pressure chamber 6 when the switching means 8 is open to achieve partial or zero stroke at the gas exchange valve 4 and is returned when the master piston 3 moves upward.

The arrow visible at the bottom right of the figure in FIG. 1 stands for a supply of hydraulic medium, starting from a hydraulic medium pump.

According to the invention, path 7 is assigned a hydraulic fluid reservoir 13, which is shown in more detail in FIGS. 2, 3. This forms a structural unit with the pressure accumulator 10 and is supplied via only one secondary path 9. The entire structural unit is advantageously positioned as close as possible to the pressure chamber 6. The piston 12 of the pressure accumulator 10 shown in FIG. 1 and the element 14 with the accumulator function are, as shown in FIGS. 2, 3, positioned within a thin-walled guide 20 with a base 24 remote from the path. The component 10, 14 thus consists of a check valve 16 arranged on the bottom 15 with a closing body 30 designed as a ball, which in the direction of the path 7 by only one spring cap 32 is held. In this case, the closing body 30 bears against a passage 33 of the base 15 in the event of overpressure on the path side 19 and thus closes it.

Radially between a wall 17 of the element 14 and the guide 20, a passage 21 is formed here as a leakage gap for supplying hydraulic fluid from the path 7 via the secondary path 9 into the interior 18. At the same time, the guide 20 has at least one outlet 34 for excess hydraulic medium in the region of its base 24.

Furthermore, a stop 28 for an end face 29 of the piston 12 is created in the region of the bottom 24. This is therefore on the side 22 facing away from the path 7. On the path side 19, on the other hand, the component 10, 14 finds a stop 27. This is designed here as a locking ring.

As the person skilled in the art can see from FIGS. 2, 3, the guide 20 is accommodated in sections in the region of the path side 19 in a bore 25 of a carrier 26 of the valve drive 1. However, a solution that is completely or at least largely integrated into the carrier 26 is also conceivable.

The compression spring 11 runs in the interior of the component 10, 14. This is supported on the path side on the floor 15 and acts on the side 22 facing away from the path 7 against a support 23. FIG. 2 shows the component 10, 14 in its sunken state, such as it is reached after switching off the internal combustion engine. It can be seen that the closing body 30 is open since there is at least pressure equality between the path side and the interior 18.

Figure 3 discloses the component 10, 14 during the regular operation of the valve train 1 or immediately after the internal combustion engine has been switched off. The space below the floor 15 has absorbed a quantity of hydraulic fluid which has been displaced from the pressure chamber 6, for example. The closing body 30 of the check valve 16 is closed due to the high pressure in the aforementioned room. A slight hydraulic The amount of medium is always conveyed into the interior 18 via the passage 21 designed as a leakage gap. Excess hydraulic medium, as mentioned, passes through outlet 34 into a reservoir or at least indirectly into the open. At the same time, due to the geodetically high outlet 34, any air that may be present can be discharged.

If the internal combustion engine is switched off and the cam 2 shown in FIG. 1 is at a stroke, with the master piston 3 then projecting axially as far as possible into the pressure chamber 6, the hydraulic medium originally passed from the pressure chamber 6 into the pressure accumulator 10 is gradually by leaks and over Force displaced by the spring means 11. Thus, as already mentioned several times, this amount of hydraulic medium is no longer available when the internal combustion engine is re-fired for immediate filling of the pressure chamber 6 during the upward movement of the master piston 3. However, since the necessary amount of hydraulic medium has been accumulated in the interior 18, it is immediately led into the pressure chamber 6 with the beginning upward movement of the master piston 3 via the sufficiently open check valve 16, the secondary path 9 and the path 7. This simple means effectively prevents air from being drawn into the pressure chamber 6 after the internal combustion engine has been started up. The valve train and thus the internal combustion engine run trouble-free right from the start.

List of reference numbers

Valve train 21 passage

Cam 22 side

Master piston 23 support

Gas exchange valve 24 bottom

Slave piston 25 bore

Pressure chamber 26 carrier

Path 27 stop

Switching means 28 stop

Secondary path 29 front

Pressure accumulator 30 closing body

Spring means 31 bottom

Piston 32 spring cap

Hydraulic fluid reservoir 33 passage

Element 34 exit

ground

check valve

wall

inner space

page path

guide

Claims

claims Hydraulically operated, variable valve train (1) of an internal combustion engine, with a master piston (3) contacted by a cam (2), a slave piston (5) acting on a gas exchange valve (4), and one positioned between master and slave pistons (3, 5) Pressure chamber (6) of changeable volume, which is cut by a path (7) for supplying and optionally discharging the hydraulic medium, which is acted upon by a switching means (8) such as an electromagnet for influencing pressure on hydraulic medium, the path ( 7) a secondary path (9) branches off to a pressure accumulator (10), which pressure accumulator (10) has a piston (12) acted upon in the flow direction to the path (7) by a spring means (11), characterized in that the path ( 7) with a hydraulic fluid reservoir (13) is connected, which consists of a pot-like element (14) with a check valve (16) arranged on its bottom (15) facing the path (7), which opens in the direction of the path (7) and in the direction of flow to one enclosed by a wall (17) of the element (14) interior (18), wherein, starting from a path side (19) of the Elements (14), radially between the wall (17) and a guide (20) for the element (14), a desired passage (21) such as a leakage gap for supplying the hydraulic medium from the path (7) for accumulation in the interior (18 ) is formed. 2. Valve train according to claim 1, characterized in that the pressure and hydraulic fluid reservoir (10, 13) form a structural unit with only one secondary path (9). 3. Valve train according to claim 1, characterized in that the piston (12) of the pressure accumulator (10) and the element (14) of the hydraulic fluid accumulator (13) are formed by a component, wherein in the interior (18) of the component (10, 14) the spring means (11) designed as at least one compression spring runs against the piston (12) / bottom on the path side (15) acts and rests on a support (23) on a side (22) facing away from the path (7). 4. Valve drive according to claim 3, characterized in that the guide (20) for the component (12, 14) consists of a cup-like body, the bottom (24) of which is positioned on the side (22) facing away from the path (7), the guide (20) being installed on the path side at least in sections in a bore (25) of a carrier (26) for the valve train (1) on the internal combustion engine. 5. Valve train according to claim 4, characterized in that the guide (20) on the path side (19) has a stop (27) as a locking ring as a path limitation for the component (12, 14), on which the path (7) facing away from (22) optionally a further stop (28) for an end face (29) of the component (12, 14) is formed, which runs in the region of the bottom (24) of the guide (20). 6. Valve train according to claim 3, characterized in that a direct guide (20) for the component (12, 14) by an at least predominant Gend in a carrier (26) for the valve train (1) arranged bore is formed. 7. Valve gear according to claim 3, characterized in that a closing body (30) of the check valve (16) on an underside (31) of the piston (12) / bottom (15) and only by a spring cap (32) in front of a passage ( 33) is fixed to the interior (18). 8. Valve gear according to claim 3, characterized in that a closing body (30) of the check valve (16) on an underside (31) of the piston (12) / bottom (15) and by a compression spring to a passage (33) to the interior (18) is pressed. 9. Valve train according to claim 8, characterized in that the check valve (16) opens at a path-side vacuum of 0.01 - 0.5 bar. 10. Valve drive according to claim 4, characterized in that the bottom (24) of the guide (20) has at least one outlet (34) for hydraulic medium. l l .valve drive according to claim 3, characterized in that a volume of hydraulic medium can be enclosed in the interior (18), which corresponds to at least 1.2 times the volume displaced during a stroke movement of the master piston (3).