WO2015036257A1

WO2015036257A1 - Hollow valve, in particular for an internal combustion engine

Info

Publication number: WO2015036257A1
Application number: PCT/EP2014/068278
Authority: WO
Inventors: Wolfgang Issler
Original assignee: Mahle International Gmbh
Priority date: 2013-09-16
Filing date: 2014-08-28
Publication date: 2015-03-19
Also published as: DE102013218488A1

Abstract

The invention relates to a hollow valve (1), in particular for an internal combustion engine, having a valve shank (2) which, along the axial direction (A) thereof, has an outer diameter (d_A) and which transitions, in the axial direction (A), into a valve plate (3) which projects radially outward from the valve shank (2), wherein, in the valve shank (2), there is provided a hollow chamber (4) which extends along the axial direction (A) and which is of substantially cylindrical form and which is at least partially filled with a liquid or liquefiable coolant, wherein the hollow chamber (4) transitions, counter to the axial direction (A), away from the valve plate (3), from a first into a second axial section (7, 8), wherein the hollow chamber (4) has, in the first axial section (7), a first hollow chamber diameter (d₁) which differs from a second hollow chamber diameter (d₂) in the second axial section (8), such that the diameter of the hollow chamber (4) within the valve shank (2) changes.

Description

Hollow valve, in particular for an internal combustion engine

The invention relates to a hollow valve for an internal combustion engine and an internal combustion engine with at least one such hollow valve.

A mechanism that in a reciprocating engine, the valves and thus the charge cycle by opening and closing the air intake and

Exhaust gas outlet controls, is referred to in vehicle technology as a valve control or valve train. Valve actuators based on so-called

Tellerhubventile are used in the prior art in almost all four-stroke engines. Such a valve comprises a valve disk, which seals the inlet or outlet passage in the closed state against the suitably shaped valve seat in the cylinder head of the reciprocating engine. The valve plate merges into an elongated, cylindrical section of the valve connected to it, in order to provide as little resistance as possible to the gases flowing through it. The last-mentioned section is familiar to the person skilled in the art as a valve stem.

According to the prior art, it is for improving the thermal

Resilience of the thermally highly stressed exhaust valves in the case of particularly heavily loaded reciprocating engines usual to run the valve stem hollow and to fill the cavity provided in the valve stem and with a suitable coolant. During operation of the reciprocating engine, the coolant melts and sloshes in this liquid state between the temporarily hot red hot valve plate and the opposite colder end of the

Valve stem back and forth and thus allows effective heat transfer from the hot valve plate to the less hot valve stem. In this way, with a suitable choice of coolant, a lowering of the temperature of the valve disk by up to 100 K can be achieved. In the case of hollow valves, however, it proves to be an optimal problem

Dimensioning the diameter of the cavity in the valve stem relative to the outer diameter of the valve stem. On the one hand, a cavity designed with the largest possible diameter favors a particularly good thermal coupling of the coolant in the cavity to the outside due to the associated thin-walled design of the circumferential wall of the valve stem. On the other hand, too thin a design of the valve stem leads to an unacceptable reduction of the mechanical stiffness of the valve stem.

From the prior art, DE 10 201 1077 198 A1 is known in connection with this problem, which describes a method for producing a hollow valve with a valve stem and a valve disk. According to the method, a bore with a constant diameter is introduced into the valve stem and then widened in the region of the valve disk by electrochemical removal.

CN 102 159 799 A discloses a hollow valve with a cavity whose cavity diameter in the region of the valve disk continuously increases away from the valve stem.

JP 2008-274779 A finally describes a hollow valve with a

Valve stem, in the cavity of a separate, throttle-like component is provided, which ensures a taper of the diameter of the cavity.

The invention has as its object to provide a hollow valve, which on the one hand the strongest possible thermal coupling of the cavity

existing coolant allowed with the environment of the valve, on the other hand but also provided with the required for operation in heavy-duty reciprocating engines mechanical stiffness. A further object of the invention is to be seen in an internal combustion engine, in particular a reciprocating engine to supplement such a hollow valve.

Accordingly, the basic idea of the invention is to vary the diameter of the cavity provided in the valve stem along its axial extension direction, whereas the outside diameter of the valve stem along the axial direction is preferably maintained at a substantially constant value. In the simplest case, such a variation of the diameter can be achieved by subdividing the cavity along the axial direction into a first and an adjoining second axial section, wherein the cavity diameter in the first axial section - hereinafter referred to as first cavity diameter - either is greater or smaller than the cavity diameter in the second axial section, which will be referred to as a second cavity diameter hereinafter. A dimensioning of the two cavity diameter approximately such that the first cavity diameter has only a slightly smaller value than the outer diameter of the valve stem, leads to a thin-walled design of the valve stem in the region of the first axial section and consequently to a very good

thermal coupling of the coolant in the cavity to the

Environment of the valve stem. In order to prevent the mechanical rigidity of the circumferential wall of the valve stem below one for the

Functioning of the hollow valve in an internal combustion engine critical

Threshold decreases, the second cavity diameter of the second axial portion is chosen sufficiently small, resulting in a compared to the first axial portion according thickwandigeren - and thus stiffer - design of the valve stem. This results in increased mechanical stability of the entire valve stem. By a suitable definition of the values for the two cavity diameter, the valve stem can be opposite conventional valve stems in terms of its mechanical and thermal properties individually to different operating conditions

adapt to different types of reciprocating engines. By the

Diameter jump between the first and the second cavity creates the previously described radial step, which causes with its edge a particularly good mixing of the refrigerant filled in the cavity and thus a good heat dissipation.

With regard to the dimensioning of the cavity in the valve stem of the approach of the invention opens the expert various technical implementation options, from which he under production engineering

To select points of view. This cavity can be implemented in a particularly simple manner, for example, by placing it on one of the valve plate

remote from the end face of the valve stem, a bore is introduced. For this purpose, a drill with a drill of predetermined diameter can be used, by means of which the shaft material of the valve stem is machined to form said bore to a predetermined depth hole. The diameter of the bore thus created corresponds to the first cavity diameter described above, the depth of the bore corresponds to a length of the first axial portion of the cavity. In order now to produce a second axial section with a second cavity diameter reduced with respect to the first axial section, a reduced diameter drill bit may be inserted into the already existing bore and the bore be lengthened along the reduced diameter axial direction in the axial direction. The amount of this extension corresponds to a length of said second axial portion, the reduced diameter of the bore in this region to the second hollow diameter, which is therefore smaller than the first cavity diameter. In other words, the cavity diameter of the hollow cylinder decreases away from the end face of the valve stem towards the valve disk, wherein the transition between the two axial sections in the form of a radial step.

As an alternative to the above-described procedure, the driller with a smaller diameter can be used initially to drill a hole with a

To create hole depth whose value corresponds to a sum of the length of the first and second axial section. Subsequently, the bore thus produced is expanded by using a larger diameter drill to a depth corresponding to the length of the first axial portion, or a step drill is used which allows the entire bore to be made in one operation. In all embodiments described above forms a cavity bounding radially inner peripheral side in the transition region between the first and the second axial portion of a radial step.

In order to close the hole made in the manner described above after filling with coolant, which is selected from the elements of the alkaline earth metals, such as in the form of liquefiable sodium, fluid-tight, it is advisable to extend this on the front side of the valve stem

Attach the shaft cover. Preferably, it is advisable to provide the shaft cover with an outer radius that corresponds to that of the valve stem, so that the peripheral side of the shaft cover is aligned with the valve stem.

With regard to the attachment of the valve cover to the valve stem, various options are available to the person skilled in the art. As particularly resistant to unwanted wear and tear proves a welded to the valve stem valve cover. A particularly resistant and cost-effective variant uses a friction welding process or a

Laser beam welding. According to an alternative embodiment variant, the cavity of the valve stem can also by means of a on the end face of the valve disk in the

Valve stem introduced bore can be generated. This approach makes it possible to provide the valve stem with a cavity whose cavity diameter decreases away from the valve head. The production of such a cavity is again achieved by using drills with drills of different diameters or stages boh rem. The hole created directly on the valve disc can be made after the regular filling of the cavity with coolant, with the help of a plug-like

Seal closure element fluid-tight. The desired seal can be made again by welding the closure element to the valve disk. In this case, for example, a particularly inexpensive friction welding or laser beam welding can be used.

However, the approach presented here of a cavity with varying cavity diameter is not limited to two axial sections with different cavity diameters. A person skilled in the art will be presented with a variety of possibilities to continue the inventive concept by appropriate design measures. For example, it is conceivable to provide a third axial section with a third cavity diameter, which is larger or smaller than the second cavity diameter, away from the second axial section in the direction of the end face of the valve stem facing away from the valve disk. For the preparation of such a third axial section, reference is made to the above explanations for the introduction of a bore in the valve disk or the end face of the valve stem facing away from the valve disk. The above-described measures can be easily determined by the person skilled in the art for the production of a cavity with three or more

Apply different cavity diameters. The radial steps are preferably arranged in a plane which is orthogonal to the axial direction. In other words, in the longitudinal section of the valve stem shown in the figures, the radial steps are in

Essentially formed at right angles. The "sharp" edges in the region of the stages typically associated with the realization of such a geometry promote the formation of turbulence in the coolant and thus lead to a particularly pronounced mixing of the coolant.

In order to achieve effective heat transfer between the valve disk and the axial end of the valve stem facing away from the valve disk, at least 50%, preferably at least 60%, of the cavity volume of the cavity should be filled with coolant.

If the first cavity diameter is chosen smaller than the second cavity diameter, then it is advisable in an advantageous

Embodiment, in the first section to form an axial shaft portion with reduced outer diameter. In this way, the

Wall thickness of the valve stem reduced in this shaft region, whereby an improved thermal coupling of the coolant in the cavity with the

Environment of the valve stem is achieved.

In an advantageous development of the above explained

Embodiment, the axial shaft portion is formed such that a wall thickness of the valve stem in the region of the axial shaft portion is substantially equal to a wall thickness of the valve stem in the region of the second portion. In this way, a particularly homogeneous thermal coupling of the coolant to the surroundings of the valve stem can be achieved along the axial direction of the valve stem due to the constant wall thickness. Particularly advantageously, the reduction of the outer diameter (dA) in the axial shaft portion amount to some 1/1 Omm.

The invention further relates to an internal combustion engine, in particular a reciprocating engine, with at least one hollow valve having one or more of the aforementioned features.

Other important features and advantages of the invention will become apparent from the dependent claims, from the drawings and from the associated

Description of the figures with reference to the drawings.

It is understood that the features mentioned above and those yet to be explained below can be used not only in the particular combination given, but also in other combinations or in isolation, without departing from the scope of the present invention.

Preferred embodiments of the invention are illustrated in the drawings and will be described in more detail in the following description, wherein like reference numerals refer to the same or similar or functionally identical components.

Show, in each case schematically,

Fig. 1 shows a first example of a hollow valve according to the invention in

a longitudinal section

Fig. 2 shows a second example of a hollow valve according to the invention

also in a longitudinal section,

3 shows a variant of the example of FIG. 1. FIG. 1 illustrates in a longitudinal section by way of example a hollow valve 1 according to the invention. This has a valve stem 2 with a constant along an axial direction A outer diameter dA- The valve stem 2 is in the axial direction A in a radially outwardly projecting from the valve stem 2 valve plate 3 over. The valve stem 2 is movably mounted in a reciprocating engine, which is only roughly indicated in the figures and designated by the reference numeral 19. The valve stem 2 is designed as a hollow body, ie in this extends along the axial direction A, a cylindrical cavity 4, which is filled to at least 50 vol .-% with a coolant 5 in the form of liquid in operation sodium. This moves during operation of the reciprocating engine due to its inertia in the periodically moving along the axial direction A valve stem 2 back and forth and thus ensures the desired heat transfer between the hot valve disk 3 and the less hot, the valve disc 3 opposite axial end 6 of Valve stem 2.

The cavity 4 is formed in the form of a bore 13, which was introduced by means of a suitable drilling means on a side remote from the valve plate 3 end face 1 1 in the valve stem 2. On that end face 1 1 is a

Valve stem 2 opposite to the axial direction A extending cap 12 welded, which closes the bore 13 fluid-tight. In a first axial section 7 of the valve stem 2, still in the region of the valve disk 3, the cavity 5 now has a first cavity diameter di. In the valve stem 2, the first axial section 7 is opposite to the axial direction in a second axial section 8, which is distinguished from the first axial section 7 by an enlarged diameter 02. Of the

Transition between the two axial sections 7, 8 is at a the Cavity 4 bounding radially inner peripheral side 10 in the form of a radial step 9 is formed.

The illustration of Figure 1 further takes away that the cavity 4 against the axial direction A, ie away from the valve disk 3, from the second axial

Section 8 merges into a third axial section 14 which has a third lumen diameter d3, which in turn is greater than the second lumen diameter 02, i. the cavity diameter d of the cavity 4 decreases along the axial direction A toward the valve disk 3. The transition between the second and third axial section 8, 14 is in the form of a radial step 15, whereby a particularly good turbulence of the coolant and thus a particularly good heat transfer can be achieved.

FIG. 2 now illustrates an alternative, for example, of FIG

Embodiment variant of the hollow valve 1, in which the cavity 4 is formed by a bore 18 which has been introduced on a side facing away from the valve stem 2 end 16 of the valve disk 3 in the valve disk 3. In a manner analogous to the cap 12 of the example of FIG. 1, the bore 18 is closed in a fluid-tight manner by means of a stopper-like closure element 17. The fastening of the closure element 17 can also be based on a welding process.

In the example of Figure 2, the diameter of the cavity 4 decreases in the axial direction to the valve stem end 2 from. Thus, in the scenario of FIG. 2, the first cavity diameter di of the first axial section has a greater value than the second cavity diameter 02 of the second axial section

Section 8; this in turn is larger than the third cavity diameter d3 of the third axial section 14. The transitions between the axial sections 7, 8, 14 are realized in an analogous manner, for example, the figure 1 in the form of radial steps 9, 15.

The radial step 9, 15 are preferably arranged in a plane which is orthogonal to the axial direction A. In other words, in the longitudinal section of the valve stem 2 shown in the figures, the radial steps 9, 15 are substantially rectangular, ie "sharp-edged". The "sharp" edges typically associated with the realization of such geometry in the region of the steps 9, 15 promote the formation of turbulence in the coolant 5 and thus its mixing.

In the hollow section 1 according to FIG. 1, in the first section 7 above the valve disk 3 the outside diameter dA can be reduced slightly locally, in particular by a few 1/10 mm, whereby the wall thickness is almost identical at least in the first and second sections 7, 8.

In order to increase the wear resistance, moreover, at least a part of the outer surface of the hollow valve 1 may be coated by means of an electroless or galvanic process or a

surface-modifying treatment, in particular nitriding, boriding, carbonitriding.

It can also be provided that the valve stem 2 is composed of a plurality of individual (tube) sections 7, 8, 14 with different cavity diameters di, 02, 03 and / or different materials, which are joined together by a welding process and their cavities 4 subsequently be reworked by one or more drilling operations. FIG. 3 shows a variant of the example of FIG. 1. Will be the first

Cavity diameter as shown in Figure 1 d i chosen smaller than the second cavity diameter 02, as shown in Figure 3 in the first section 7 from the second portion 8 away to the valve plate 3 through an axial shaft portion 20 are formed with reduced outer diameter dA. In this way, the wall thickness of the valve stem 2 is reduced in the region of the axial shaft portion 20, which in turn improves the thermal coupling of the

Coolant 5 is achieved in the cavity 4 with the environment of the valve stem 2.

As clearly shown in FIG. 3, the axial shaft section 20 becomes

preferably formed such that the wall thickness of the valve stem 2 in the region of the axial shaft portion 20 substantially equal to one

Wall thickness of the valve stem 2 in the region of the second portion 8 is. In this way, along the axial direction A of the valve stem 2, a particularly homogeneous thermal coupling of the coolant 5 to the

Environment of the valve stem 2 can be achieved.

Particularly expedient, the reduction of the outer diameter dA in the axial shaft portion 20 may be some 1 / 10mm.

Claims

claims

1 . Hollow valve (1), in particular for an internal combustion engine,

with a valve stem (2) which along its axial direction (A) has a preferably constant outer diameter (d _A ) and merges in the axial direction (A) into a valve plate (3) projecting radially outwards from the valve stem (2) .

wherein in the valve stem (2) along the axial direction (A)

extending and substantially cylindrically shaped cavity (4) is provided which is at least partially filled with a liquid or liquefiable coolant (5),

wherein the cavity (4), opposite to the axial direction (A), away from the valve plate (3), from a first into a second axial section (7, 8), wherein the cavity (4) in the first axial section (7) first

Cavity diameter (di), which is different from a second cavity diameter (d ₂ ) in the second axial portion (8), so that the diameter of the cavity (4) within the valve stem (2) changes.

2. Hollow valve according to claim 1,

characterized in that

a radially inner peripheral side (10) bounding the cavity (4) forms a (first) radial step (9) in the transition region between the first and the second axial section (7, 8).

3. Hollow valve according to claim 1 or 2,

characterized in that the cavity (4) is formed by a bore (13) which is provided on an end face (11) of the valve stem (2) facing away from the valve disk (3),

on the front side (1 1) a the valve stem (2) against the axial direction (A) extending cap (12) is mounted, which closes the bore (13) fluid-tight.

4. Hollow valve according to claim 3,

characterized in that

the cap (12) on the front side (1 1) is welded.

5. Hollow valve according to claim 1 or 2,

characterized in that

the cavity (4) is formed by a bore (13) which is provided on an end face (16) of the valve disk (3) remote from the valve stem (2),

the bore (13) by means of a plug-like design

Closure element (17) is sealed fluid-tight.

6. Hollow valve according to one of the preceding claims,

characterized in that

the first cavity diameter (di) is larger than the second cavity diameter (d ₂ ).

7. Hollow valve according to one of claims 1 to 5,

characterized in that

the first cavity diameter (di) is smaller than the second cavity diameter (d ₂ ).

8. Hollow valve according to one of the preceding claims, characterized in that

in the first section (7) an axial shaft section (20) with reduced

Outer diameter (dA) is formed.

9. Hollow valve according to claim 8,

characterized in that

the axial shaft portion (20) is formed such that

a wall thickness of the valve stem (2) in the region of the axial

Shaft portion (20) substantially equal to a wall thickness of the

Valve stem (2) in the region of the second portion (8).

10. Hollow valve according to claim 8 or 9,

characterized in that

the reduction of the outer diameter (dA) in the axial shaft portion (20) is a few 1 / 10mm.

1 1. Hollow valve according to one of the preceding claims,

characterized in that

the cavity (4), opposite to the axial direction (A), moves away from the valve head (3), from the second axial section (8) to a third axial section (14) having a third cavity diameter (ds) larger or smaller than the second cavity diameter (d2).

12. Hollow valve according to one of the preceding claims,

characterized in that

a radially inner peripheral side (10) bounding the cavity (4) forms a (second) radial step (15) in the transition region between the second and third axial sections (8, 14).

13. Hollow valve according to one of the preceding claims, characterized in that

the first and / or second radial step (9, 15) lies in a plane that is orthogonal to the axial direction (A).

14. Hollow valve according to one of the preceding claims,

characterized in that

the cavity diameter of the cavity (4) either increases or decreases along the axial direction (A).

15. Hollow valve according to one of the preceding claims,

characterized,

at least part of the outer surface of the hollow valve (1) is coated by means of an electroless or galvanic process or is surface-modified, in particular nitrided, borated,

carbonitrated.

16. Hollow valve according to one of the preceding claims,

characterized,

the valve stem (2) is composed of a plurality of individual (tube) sections (7, 8, 14) with different cavity diameters (di, 02, ds) and / or different materials, which are separated by a

Welding process are connected together and their cavities (4) have been subsequently reworked by one or more drilling operations.

17. internal combustion engine, in particular reciprocating engine with at least one hollow valve (1) according to one of the preceding claims.