Switching element for a valve drive of an internal combustion engine

Abstract

A switching element (1) for a valve drive of an internal combustion engine, preferably for shutting off valves, is provided, and includes an external part (2) in whose bore (3) an inner element (5) is axially movable. The external part (2) and the inner element (5) have at least a respective mutually aligned recess (7, 8) due to an axially spaced relative position obtained through a lost motion spring (6), and in one of the recesses, in the direction of the other recess, displaceable coupling means (9) are mutually applied in the relative position for coupling the inner element (5) with the external part (2). Two pistons (10) are provided as coupling means (9), which travel in the recess (8) formed as a radial bore of the inner element (5), and which diametrically oppose one another. The recess (7) of the external part (2) is formed as an annular groove (16) in the bore (3), and the pistons (10) at their underside (17) remote from the cam, starting from their radially external end faces (13), sectionally have a planar transverse surface (14) as contact region to a facing annular surface (15) of the annular groove (16), and the pistons (10) are guided with rotation securement (19) in the inner element (5). This provides a switching element (1) which has a simply constructed coupling mechanism, which produces only a small component loading.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of PCT/EP02/14431, filed Dec. 18, 2002, which is incorporated herein by reference as if fully set forth.

BACKGROUND

The invention relates to a switching element for a valve drive of an internal combustion engine, preferably for shutting off valves, with an external part in whose bore an inner element is axially movable, the external part and the inner element having at least one respective mutually aligned recess due to an axially spaced relative position obtained by a lost motion spring, and in one of the recesses, facing in the direction of the other recess, displaceable coupling means are mutually applied in the relative position for coupling the inner element with the external part.

Such a switching element, constructed here as a cam follower in a tappet push rod gear, is known from DE 199 15 531. It is disadvantageous in this that only one piston is provided as the coupling means. It is clear to one skilled in the art that there is a high component loading in the coupling region because of the single piston coupling. There is also a relatively great danger of tilting of the inner element with respect to the external part. It is disadvantageous that a bore is provided as the recess into which the piston travels as coupling means. An extremely undesired edge loading can occur here when the coupling means travels out insufficiently, because of the special penetration of the bodies.

SUMMARY

The object of the invention is therefore to provide a switching element of the kind mentioned at the beginning, in which the cited disadvantages are eliminated with simple means.

This object is attained according to the invention in that two pistons are provided as coupling means, which travel in the recess formed as a radial bore of the inner element, and which diametrically oppose one another there, the recess of the external part being formed there as an annular groove in the bore, and the piston at its underside remote from the cam, starting from its radially external end face, sectionally has a planar transverse surface as contact region to a facing annular surface of the annular groove, and the piston being guided in a rotationally secure manner in the inner element.

A switching element with a very secure coupling mechanism is hereby provided. The component loading, and likewise the tilting movement, are greatly reduced by the two-piston locking. On the other hand it is to be observed that a coupling aperture which is easy to make is present in the external part because of the recess in the external part being formed as a peripheral annular groove. According to the invention, the pistons have on their underside a planar surface as contact region for the annular groove, so that the surface pressure is greatly reduced here. In other words, through the measures according to the invention, the cam stroke is transferred to the inner part over very large bearing surfaces. If necessary, more than two coupling means can be arranged in the inner element; preferably these are then symmetrically distributed.

So that the planar transverse surface is always in contact with the annular surface of the annular groove, the pistons are fixed against rotation in their recess by means of a simple rotational securement. Here, in one specific embodiment of the invention, for example, a surrounding snap ring is present enclosing the inner element and on which the cross section of the piston abuts in the recess region. The pistons can of course be themselves secured against rotation in their recess by means of flats or spring-groove embodiments.

As a further development of the invention, it is proposed to provide a stop for the piston in the inner element. This is arranged centrally, so that both pistons always have the same travel path radially outward.

Preferably the radial bore in the inner element is made as a through bore. An offset or stepped construction is however also conceivable, so that the said spring ring or a similar means can be dispensed with.

It is particularly advantageous if the radially outward end face of the piston, at least in the edge region toward the transverse surface, has a curvature correlating with the bore of the inner element. It is thus clear that a good bearing region is already provided with even the smallest travel of the piston into the annular groove of the external part.

A further particularly preferred embodiment of the invention relates to the end side of the piston connecting the transverse surface with the underside having a curvature correlating to the bore of the inner element, or being beveled like a roof. It is thus clear that by means of these simple measures the pistons can travel out radially very far in the annular groove in the case of coupling, and thus form an outstanding support pattern.

The scope of this invention relates expressly to all kinds of switching elements in valve drives such as cam followers in tappet push rod drives, support elements for finger levers, bucket tappets, etc.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is appropriately described with reference to the drawings.

FIG. 1 is a longitudinal section through a switching element constructed as a roller tappet according to the invention,

FIG. 2 is a partial longitudinal section, turned through 90° according to FIG. 1,

FIG. 3 is a partial longitudinal section similar to FIG. 2,

FIG. 4 is a bottom view of a piston as coupling means,

FIG. 5 is a cross-sectional view of the piston, and

FIGS. 6 and 7 show alternative embodiments to FIGS. 4 and 5.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1-3 disclose a switching element 1 for a valve drive of an internal combustion engine. This is constructed here as a roller tappet for a tappet push rod drive. It includes an external part 2, in whose bore 3 the external surface 4 of an axially movable inner element 5 runs. The external part 2 and the inner element 5 are urged apart by a lost motion spring 6, not further described.

In the axially separated position of the external part 2 from the inner element 5 as described in the drawing, the recesses 7, 8 are mutually aligned. The recess 7 of the external part 2 is made as a peripheral annular groove 2. The recess 8 in the inner element 5, on the contrary, is made as a through bore extending radially. A path like a bowstring chord, or skew, is likewise conceivable.

Two diametrically opposed coupling means 9 are arranged in the recess 8 of the inner element 5. These are formed as pistons 10 here, and are urged apart by a compression spring means 11. A stop for the pistons 10 is provided centrally in the recess 8. This is provided as an annular part such as a snap ring. Thus in a decoupling position of the pistons 10, their central position and thus equal travel path is guaranteed.

As shown in detail in FIGS. 4-7, the pistons 10 sectionally have a planar transverse surface 14 starting from their radially outer end face 13. This acts as contact region to a facing annular surface 15 (see FIGS. 1-3) of the recess 7 formed as an annular groove. As can be seen, the coupling aperture in the external part 2 is formed circumferentially; this has manufacturing advantages, for example.

The end face 13 of the piston 10 can be curved, as shown in FIG. 4, as can the bore 3 of the external part 2. Thus a good bearing pattern is immediately set up when the piston 10 travels into the annular groove 16. So-called edge supports are effectively avoided.

As can be seen from FIGS. 4 and 6, an end side 18 of the piston 10 connecting the transverse surface 14 with an underside 17 remote from the cam is likewise provided with a curvature correlating with the bore 3 of the external part 2 or, as shown in FIG. 6, is beveled like a roof.

Since the transverse surfaces 14 of the pistons 10 have to be always facing the annular surface 15 of the annular groove 16 in the external part 2, a simple rotational securement 19 is provided for the pistons 10 (see FIG. 2). This comprises an annular part such as a snap ring, which is arranged in an annular groove 20 on the external surface 4 of the inner element 5. The rotational securement 19 runs at such a height as to engage under the transverse surface 14 of the pistons 10.

FIG. 3 shows an alternative measure to the central stop 12 for the pistons 10. This is provided here as a component 21 such as a pin, projecting orthogonally into the recess 8, formed as a radial bore, of the inner element 5.

Thus a switching element is present which has a very secure and simply built coupling mechanism which produces only a very small component loading.

List of Reference Numerals

• 1 switching element
• 2 external part
• 3 bore
• 4 external surface
• 5 inner element
• 6 lost motion spring
• 7 recess
• 8 recess
• 9 coupling means
• 10 piston
• 11 compression spring means
• 12 stop
• 13 end surface
• 14 transverse surface
• 15 annular surface
• 16 annular groove
• 17 underside
• 18 end side
• 19 rotation securement
• 20 annular portion
• 21 pin component
• 22 edge region

Claims

1. Switching element (1) for a valve drive of an internal combustion engine for shutting off valves, comprising an external part (2) with a bore (3) in which an inner element (5) is axially movable, the external part (2) and the inner element (5) having at least a respective mutually aligned recess (7, 8) due to an axially spaced relative position obtained by a lost motion spring (6) acting between the inner element and the external part, and in one of the recesses, in a direction of the other recess, a displaceable coupling mechanism (9) is provided for coupling the inner element (5) with the external part (2), wherein two pistons (10) are provided as the coupling mechanism (9), which travel in the recess (8) formed as a radial bore of the inner element (5), and which diametrically oppose one another, the recess (7) of the external part (2) being formed as an annular groove (16) in the bore (3), and the pistons (10) have an underside (17) and starting from a radially outer end face (13) of the pistons, sectionally have a planar transverse surface (14) as a contact region to a facing annular surface (15) of the annular groove (16), and the pistons (10) are guided by a rotation securement (19) in the inner element (5).

2. Switching element according to claim 1, wherein the rotation securement (19) comprises an annular part which extends in an annular groove (20) on an external surface (4) of the inner element (5) and is arranged at a height such that the annular part engages under the planar transverse surface (14) of the piston (10).

3. Switching element according to claim 1, wherein the recess (8) in the inner element (5) has a stop (12) for radially inner end faces of the pistons (10), and the stop (12) is positioned centrally.

4. Switching element according to claim 3, wherein the recess (8) is formed as a through bore, and the stop (12) is formed as one of an annular part located in the through bore, or a component (21) that projects orthogonally into the through bore.

5. Switching element according to claim 1, wherein the radially outer end face (13) of the piston (10), at least in an edge region (22) to the transverse surface (14), has a curvature corresponding to the bore (3) of the inner element (5).

6. Switching element according to claim 1, wherein an end side (18) of the piston (10), connecting the transverse surface (14) with the underside (17), has a curvature correlating to the bore (3) of the inner element (5), or is formed with a roof-like bevel in a bottom surface thereof.

7. Switching element according to claim 1, wherein the switching element (1) is produced as a cam follower in a tappet push rod drive.

8. Switching element according to claim 2, wherein the recess (8) in the inner element (5) has a stop (12) for radially inner end faces of the pistons (10), and the stop (12) is positioned centrally.