SWITCHING ELEMENT FOR A VALVE DRIVE OF AN INTERNAL COMBUSTION ENGINE

ELEMENT DE COMMUTATION POUR SYSTEME D'ENTRAINEMENT DE SOUPAPES DE MOTEUR A COMBUSTION INTERNE

English Abstract

The invention relates to a switching element (1) for a valve gear of an
internal combustion engine, preferably for shutting off valves. Said valve
comprises an external part (2), in addition to an internal element (5) that
can be axially displaced in the bore (3) of said external part, said external
part (2) and internal element (5) having at least one respective recess (7, 8)
that lie in alignment with and at an axial distance from one another in a
relative position that is achieved by a lost motion spring (6). In one of the
recesses, coupling means (9), which are used for coupling the internal element
(5) to the external part (2) in said relative position and which can be
displaced in the direction of the other recess, are allocated to one another.
Two pistons (10) are provided as the coupling means (9), said pistons running
in the recess (8) that is configured as a radial bore of the internal element
(5) and lying diametrically opposite one another. The recess (7) of the
external part (2) is configured as an annular groove (16) in the bore (3) of
said part and sections of the underside (17) of the pistons (10), which faces
away from the cams, have a flat transversal surface (14), originating from the
radially external front face (13) of said underside and acting as a contact
area for a facing annular surface (15) of the annular groove (16). The pistons
(10) are guided in the internal element (5) by means of an anti-torsion
mechanism (19). The invention provides a switching element (1) that comprises
a simply constructed coupling mechanism, which creates negligible stress on
the components.

French Abstract

L'invention concerne un élément de couplage (1) pour un ensemble soupape d'un moteur à combustion interne, de préférence pour le désaccouplement de soupapes. L'élément de couplage selon l'invention comprend une partie extérieure (2) dans l'alésage (3) de laquelle un élément intérieur (5) est déplaçable axialement. La partie extérieure (2) et l'élément intérieur (5) possèdent chacun au moins un logement (7, 8), alignés l'un sur l'autre, dans une position relative éloignée axialement, obtenue par un ressort à perte de mouvement (6). Dans un des logements, des moyens de couplage (9), mobiles en direction de l'autre logement et servant au couplage de l'élément intérieur (5) avec la partie extérieure (2), sont appliqués l'un contre l'autre dans la position relative. Selon l'invention, on utilise comme moyens de couplage (9) deux pistons (10) qui s'étendent dans le logement (8), réalisé sous forme d'alésage radial, de l'élément intérieur (5) et y sont diamétralement opposés l'un à l'autre. Le logement (7) de la partie extérieure (2) est réalisé sous forme de rainure annulaire (16) dans l'alésage (3) de la partie extérieure et les pistons (10) présentent, par sections, une surface transversale plane (14) sur leur face inférieure (17) éloignée des cames en partant de leur surface frontale radialement extérieure (13), cette surface transversale plane servant de zone de contact avec une surface annulaire (15), faisant face, de la rainure annulaire (16). Les pistons (10) sont guidés dans l'élément intérieur (5) par l'intermédiaire d'une butée de torsion (19). On obtient ainsi un élément de couplage (1) possédant un mécanisme de couplage de réalisation simple qui ne génère qu'une faible sollicitation des composants.

Claims

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 or 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 step (12) is positioned centrally.


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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 (18) 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 or 5, 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.

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Description

CA 02479264 2004-08-19
(0001) SWI'I'CHING ELEMENT k'OR A VALVE DRIVE OF AN INTERNAL
COMDUSTrON ENGINE
[0002]
[0003)
[0004] &E~.CKGROUND
[0006] 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 whdse bore an inner element is axially movable, the external part and tha
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 tkie direction of the other recess, displaceable coupling means are
mutually
applied in the relati~re position for coupling the inner element with the
external part.
[0006] Such a switching element, constructed here as a cam follower iu a
tappet push rod gear, is known from DE 199 1C 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.
[00071 SttIdMARY
[0008] 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.
[0009) 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
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CA 02479264 2004-08-19
of the inner element, and which diametrically oppose one anotb.er there, the
recess
of the external part being formed there ae an anzwlar groove in the 'bore, and
the
piston at its underside remote firora the cam, starting from its radially
eternal en.d
face, aect~.or~ally has a planar transverse szu-face 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.
[0010] A switching element with a very secure coupling mechanism is hereby
provided. The component loading, and likeWi~se 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 presexit in the exte~cnal part
because of
the recess in the external part being formed as a peripheral annulax groove.
According to the invention, the pistons have on their underside a planar
surface as
contact region for the annular groove, eo that the surface pressure is greatly
reduced here. In other words, txurough the measures according to the
i~rmention, the
cam stroke is transferred to the inner part over very large bearing surfaces.
If
necesearp, more than two coupling means can be arranged in the inner element;
preferably these are then symmetrically distributed,
[0011] So that the planar transverse surface is always in contact with the
annular surface of the annular groove, the pistons are fated 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 agaix~ rotation
in
their recess by means of flats oar spring groove embodiments.
(0012) An a further development of the invention, it is proposed to provide a
stop for the piston in the inner element. ~'hie is arranged centrally, so that
both
pistons always have the same travel path 1'adially outward,
(0013] Preferably the radial bore in the inner element is made as a through
bore_ An offset or stepped construction ig however also conceivable, so that
the said
opting ring' yr a similar means can be dispensed with.
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CA 02479264 2004-08-19
[0014] It is particularly adbantageous if the radially outward end face of the
piston, at Ieast in the edge rsgion toward the transverse surface, has a
curvature
correlating with the bore of the inner element. It ie thus Blear that s good
bearing
region is already provided with even the smallest travel of the piston into
the
annular groove of the external part.
[0015] A further particularly preferrred 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
Iike a roof. It is thus clear that by means of these simple measures the
pistons can
travel out radislly very far in the annular groove in the case of coupling,
and thus
form an outstanding support pattern.
[0016] The scope of this invention t'elates expressly to atll kinds of
switcking
elements in valve drives such as cam ~ollowera in tappet push rod drives,
support
elements for finger levers, buelrst tappets, etc.
[0017] BRIEF DESCRIPTION OF THE DR~A.WIN~GS
10018] The iaventioa is appropriately deset~bed with reference to the
drawings.
j4029] Figure 1 is a longitudinal section through a switchixig element
constructed as a xoller tappet according to the invention,
[0020] figure 2 is a partial longitudinal section, turned through 90°
accordi-ng to Fig. Z,
[0021] Figure 3 is a partial longitudinal section similar to Figure 2,
[0022] Figure 4 is a bottom view of a piston as coupling means,
[0023] Figure 5 ie a cross-sectional view of the piston, and
10024] figures fi and 7 show alternatsve exnbodinaents to Figures 4 and 5.
(0026) DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0026] Figures 1-3 disclose a switching element 1 for a valve drive of an
internal combustion engine. This is constructed here as a roller fiappet for a
tappet
push rod drive. It includes an eztern.al pelt 2, in whose bore 9 the external
surface 4
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_ _r__ ... __.



CA 02479264 2004-08-19
of an agally movable inner element ~ runs. The external part 2 and the Tuner
element b are urged apart by a lost motion spring 6, not fux'ther described.
(002?] 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 atlaular groove 2, The
recess
8 in the inner element 5, on the contrary, is made as a through bore
exteudi_ng
radially. A path like a bowstring chord, or skew, is likewise conceivable.
(0028] Two diametrically opposed coupling means 9 are arranged in the
recess 8 of the inner element 6. These are formed as pistons 10 here, and are
urged
span by a. co~oapression spring means 11. A stop for the pistons 10 is
provided
centrally is the recess 8. This is provided as an annular part such as a
s~o~ap ring.
Thus in a decouplf ng position of the pistons 10, their central position and
thus equal
travel path is guaranteed.
(0029] As shown in detail in Figures 4-7, the pistons IO 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 h'igs 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.
(0030] The and face 13 of the piston 10 can be curved, as shown in Figure 4,
as can the bore 3 of the external part 2. Thus a good bearing pattern is
immediately
set up when the piston IO travels into the annular groove 36. So-called edge
suppox-ts are effectively avoided,
[0031] As can be seen from la5igures 4 and 6, an end side 18 of the piston 10
connecting the transverse surface 14 with an underside lT remote from the cam
is
likewise provided with a curvature correlating with the bore 3 of the external
part 2
or, as shown in Figure 6, is beveled like a mof.
(00821 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 Figure 2).
This
comprises an annular part such as a snap ring, which is arranged in an annular
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CA 02479264 2004-08-19
groove 20 on the external surface 4 of the inner eleuient 5. The rotational
sec~urement 19 runs at such a height as to engage under the transverse surface
14 of
the pistons lo.
[0033] figure 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.
[0084) Thus a switchipgr element is present which has a very secure and
simply built coupling mechanism which produces only a very small component
loading.
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CA 02479264 2004-08-19
[0035] List of Reference Numerals
x switchir~.g element


2 external part


3 bore


4 external surface


inner element


6 lost motion spring


7 recess


8 recess


9 oouplW g means


piston


11 compression spring mesas


12 stop


13 end surface


14 transverse surface


annular surface


16 annular groove


17 underside


18 end side


19 rotation securement


annular portion


21 pin component


22 edge region


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Representative Drawing