The present invention relates to a tensioning device for
Endless drives, in particular chain drives of an internal combustion engine,
with a housing, one in the housing along
movably guided clamping piston, one between housing
and piston formed pressure chamber for receiving a hydraulic fluid
and a damping stop.
Such a tensioning device is from the WO 2006 / 045406A1
known. Such hydraulic clamping systems usually work with a leakage gap between the housing receiving bore and the clamping piston in order to obtain a damping in the clamping system. When the internal combustion engine is at rest there is a pressure reduction in the pressure chamber of the tensioning device, since hydraulic fluid escapes via the leakage gap. When starting the internal combustion engine, it may then lead to the development of sufficient pressure in the pressure chamber to noise because the Endlostrieb is not sufficiently stretched. In chain drives the clamping piston of the clamping device usually presses against a pivotally mounted clamping rail, which in turn presses against the chain. In most cases, there is also a compression spring in the pressure chamber, which is in contact with the tensioning piston over the entire tensioning travel. Unless sufficient hydraulic fluid with sufficient pressure is present in the pressure chamber during the starting process, it may come to striking the tensioning rail or due to lack of damping effect to increased noise. For this purpose, an elastic end stop is provided in the known tensioning device. This is configured as a sleeve with frusto-conical end and is seated on the end face of the housing. The tensioning piston extends through the elastic end stop. If insufficient pressure is available in the pressure chamber during start-up, the tensioning rail can hit this end stop and buffer the movement of the tensioning rail. However, these designs require longer clamping devices with longer clamping pistons. In addition, the clamping rail must be matched to the clamping device, so that it can rest on the end stop.
Now is the object of the present invention, a clamping device
to provide the type mentioned, the possible
little constructive changes in terms of common
Require jig designs without limit stop.
is inventively provided that the tensioning piston
has a stop surface with the damping end stop
for damped stopping of the retraction movement of the clamping piston
can be brought to a stop. The invention is therefore a different one
Path. It will not be the tensioning rail opposite the housing
the tensioning device stopped in their movement, but the tensioning piston
even drives on a damping end stop,
which pretends its retracted end position. This will additionally
achieved that in highly dynamic systems, the Aufdrückfläche
the tensioning piston does not lift off the tensioning rail, for example
but remains in permanent contact. A striking of the tensioning piston
At the bottom of the housing has always been by a particularly strong
Pressure spring inside the pressure chamber prevented. The compression spring provides
but no damping stop as it over
the entire travel with the tensioning piston in contact
stands. As a second possible solution are numerous
Design variants are known in which attempts are made to fill the oil
to get in the pressure room. Also locking devices are known which
limit the retraction movement of the piston and wear out of the
Adjust chain drive from detent to detent. These constructions
are extremely complicated and therefore expensive. About that
In addition, the Einfahrendposition changes constantly
and a muted strike is not provided. Of the
Tensioning piston of the tensioning device according to the invention
therefore has a fixed or fixed end position of the retraction movement
on, which remains the same over the entire service life.
Also known are special designs that use additional damping devices. As an example, here is the DE 44 43 095 A1
called. However, such a construction does not serve to dampen the retraction movement of the tensioning piston, but to reduce high-frequency vibrations in the damping system.
particularly simple variant is that the damping end stop
is arranged in the pressure chamber. For all common clamping devices
is due to the compression spring always a certain distance between
the clamping piston and the bottom of a receiving bore in the housing available.
This existing space can be used to attach the damping end stop
be used. But that also means that conventional
Clamping equipment retrofitted or simple
can be converted without being otherwise
must change the design. It can therefore be existing
Parts are used. The damping end stop
should then consist of suitable materials that meet the requirements
grown in the pressure chamber and exposure to the hydraulic fluid
Conveniently, for this purpose, the housing have a receiving bore for the clamping piston and the Dämpfungsendanschlag at a stage be arranged in the receiving bore. As a step here also simply the reason of the receiving bore can be used, in the mostly opens the inlet opening for the hydraulic fluid.
In order to
Even with the tensioning piston already common parts without redesign
can be used, the stop surface
from the housing end surface of the
Tensioning piston be formed. Accordingly, the damping end stop is preferred
arranged at the bottom of the receiving bore and the end face
The tensioning piston can then be supported on this. It
is therefore no longer absolutely necessary, an oversized
Use compression spring, which is a striking between housing
and to prevent tensioning piston.
A further embodiment provides that a
Pressure chamber inlet for the inflow of hydraulic fluid present
is, which extends through the damping end stop.
Especially with Einschraubkettenspannern the supply takes place
with hydraulic fluid usually centrally over the base area
the receiving bore. In this variant, this can continue,
because the damping end stop the pressure chamber inlet annular
the damping end stop is designed as a ring element,
can in a further variant in the opening at least
a portion of a check valve disposed in the pressure chamber inlet
be arranged. This results in a space-saving overall structure.
Due to the mostly hollow design of the clamping piston whose end face
Also do not drive on the check valve, so that
the damping function by the damping end stop
and the inflow function through the check valve
be provided in the same length section.
Further, a compression spring may be arranged in the pressure chamber, the
between housing and the clamping piston acts and the
with the housing facing end on the Dämpfungsendabschlag
supported. The compression spring therefore also serves for fixation
the damping end stop, so that this to the bottom
the receiving hole is pressed. In a simplified
Variant, the compression spring, however, at the bottom of the mounting hole
support while the damping end stop
surrounds the end of the compression spring.
In another embodiment, the damping end stop is seated
on a flange portion of the check valve, wherein
the check valve in its position in another
Stage is secured in the receiving bore thereby. The damping end stop
accordingly holds the check valve in its receiving stage.
It is particularly favorable if the damping end stop
again pressed by the compression spring in its position
becomes. The compression spring thus secures the damping end stop
and the check valve.
can the damping end stop of at least one elastic
Ring element be formed. Here are suitable elastic bases
or rubber materials are used, but also suitable
Spring elements made of harder materials can
find application here.
Variant provides that an elastic ring element of a plate spring
is formed. Here can z. B. an entire plate spring package can be used.
In the following an embodiment of the present invention will be explained in more detail with reference to a drawing. The only figure shows:
a Einschraubkettenspanner with damping end stop in full cut.
The chain tensioner shown in the figure 1 has a screw-in 2 with a threaded section 3 and a screw-in 4 as well as in the screw-in housing 2 slidably guided tensioning piston 5 on. For holding the tensioning piston 5 is the screw-in housing 2 with a receiving hole 6 Mistake. The tensioning piston 5 and the mounting hole 6 have a slight play on each other, so that however there is a leakage gap, located in the front area to the annular gap 7 extended. For this purpose, the tensioning piston is in the front section 5 reduced in diameter, but increases again to Aufdrückkopf 8th with the impression surface 9 out.
The tensioning piston 5 is designed as a hollow body and has at its Aufdrückkopf 8th a vent 10 on. Between the tensioning piston 5 and the screw-in housing 2 is a pressure room 11 formed, which also partially into the interior of the tensioning piston 5 extends. Inside the tensioning piston 5 is a compression spring 12 placed a mushroom-shaped packing 13 presses against the inner end of the tensioning piston. The filler 13 is made of plastic and has its mushroom head 14 a vent groove 15 on. The compression spring 12 rests on the underside of the mushroom head 14 and pushes it against the tensioning piston 5 ,
At the bottom of the pressure chamber 11 is the receiving hole 6 double stepped. The first level becomes of the reason 16 the receiving bore 6 formed, in turn, the second stage 17 is provided. On the ground 16 the receiving bore 6 sits a schematically illustrated damping end stop 18 up, from the compression spring 12 is pressed into its position.
In the second stage 17 sits a commercial check valve 19 whose valve cage is partially in the opening 20 of the annular damping end stop 18 extends. The opening direction of the check valve 19 is chosen so that hydraulic fluid in the pressure chamber 11 can flow in. The check valve 19 is preceded by an inlet opening 21 with cross hole 22 , These holes 21 and 22 and the check valve 19 together form the pressure chamber inlet.
Below the screw-in head 4 of the screw-in housing 2 there is a sealing ring 23 ,
The damping end stop 18 may be a ring member made of an elastic material. It is also possible to use a plate spring or a plate spring package here. The lower end face 24 of the tensioning piston 5 serves as a stop surface on the damping end stop 18 runs.
The following is the operation and operation of the chain tensioner described above 1 explained in more detail.
The chain tensioner 1 is screwed at a suitable location in the engine block of an internal combustion engine (not shown) until the sealing ring 23 comes to the plant. In this position is the cross hole 22 automatically with the engine oil hydraulics. When starting, therefore, engine oil flows through the transverse bore 22 and the inlet hole 21 through the check valve 19 in the pressure room 11 , The tensioning piston 5 is extended and pushes with his impression surface 9 against a tensioning rail (not shown). During this starting process is the damping effect of the chain tensioner 1 not yet fully given. In addition, prevails in the pressure room 11 still no sufficient fluid pressure. Due to vibrations in the chain drive, the tensioning piston 5 retract further than desired. The damping end stop 18 ensures that the impact of the face 24 on the screw-in housing 2 not too hard. In particular, during the starting process of an internal combustion engine, it is thus possible to prevent or at least minimize rattling or overall noise generation. In operation, with sufficient pressure in the pressure chamber 11 , the damping stop will become 18 no longer needed, as the tensioning piston 5 is sufficiently extended. The Spannkolbenweg is determined so that in normal operation, a sufficient distance of the end face 24 to the damping end stop 18 remains. Even when the internal combustion engine is switched off, the hydraulic pressure only slowly breaks down through the leakage gap. In addition, the force of the compression spring 12 chosen so that it does not lead to an impact on the damping end stop 18 comes. To be damped mainly vibrations that may occur during the starting process of the internal combustion engine. For the design in operation the damping end stop plays 18 therefore a minor role, as this can only be used in a specific operating condition. As a result, as far as possible a separation of functions between chain tensioner design or tensioner position and the starting flapper problem is achieved.
QUOTES INCLUDE IN THE DESCRIPTION
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Cited patent literature
- - WO 2006/045406 A1 
- - DE 4443095 A1