U.S. patent application number 09/577182 was filed with the patent office on 2002-11-07 for tensioning device for chains.
Invention is credited to Ullein, Thomas.
Application Number | 20020165056 09/577182 |
Document ID | / |
Family ID | 7909115 |
Filed Date | 2002-11-07 |
United States Patent
Application |
20020165056 |
Kind Code |
A1 |
Ullein, Thomas |
November 7, 2002 |
TENSIONING DEVICE FOR CHAINS
Abstract
A tensioning device for a chain (1) comprising a housing (3),
said housing (3) carries a first sliding shoe (6) for contact with
a first side (7) of the chain (1) with the tensioning device
further comprising a tensioning piston (5,23) that is guided on the
housing (3) and comprises a second sliding shoe (8,24) for contact
with a second side (9) of the chain (1) whereby in an economic and
simple-to-manufacture tensioning device, the housing (3) and the
first sliding shoe (6) are made in one piece with each other.
Inventors: |
Ullein, Thomas; (Stegaurach,
DE) |
Correspondence
Address: |
BIERMAN MUSERLIAN AND LUCAS
600 THIRD AVENUE
NEW YORK
NY
10016
|
Family ID: |
7909115 |
Appl. No.: |
09/577182 |
Filed: |
May 23, 2000 |
Current U.S.
Class: |
474/110 ;
474/109; 474/111; 474/140 |
Current CPC
Class: |
F16H 7/0848 20130101;
F16H 7/08 20130101; F16H 2007/0812 20130101; F16H 2007/0806
20130101; F16H 2007/0874 20130101; F16H 2007/0859 20130101; F16H
2007/0878 20130101 |
Class at
Publication: |
474/110 ;
474/111; 474/140; 474/109 |
International
Class: |
F16H 007/08; F16H
007/22; F16H 007/18 |
Foreign Application Data
Date |
Code |
Application Number |
May 26, 1999 |
DE |
199 23 905.3 |
Claims
What is claimed is:
1. A chain tensioning device comprising a housing carrying a first
sliding shoe for contact with a first side of a chain and a
tensioning piston guided on the housing, said tensioning piston
comprising a second sliding shoe for contact with a second side of
the chain, the housing and the first guiding shoe being made in one
piece with each other.
2. A tensioning device of claim 1 wherein the first sliding shoe
and the housing are made of plastic.
3. A tensioning device of claim 2 wherein the plastic is
polyamide.
4. A tensioning device of claim 2 wherein the plastic of the
housing is reinforced with fibers.
5. A tensioning device of claim 4 wherein the fibers are glass
fibers.
6. A tensioning device of claim 1 wherein the housing comprises a
reception for the tensioning piston.
7. A tensioning device of claim 6 wherein the reception is a
bore.
8. A tensioning device of claim 1 wherein the housing comprises two
mounting eyes for insertion of a connecting means.
9. A tensioning device of claim 8 wherein the connecting means is
configured as screws.
10. A tensioning device of claim 8 wherein the mounting eyes are
lengthened by sleeve-like extensions formed integrally on the
housing.
11. A tensioning device of claim 10 wherein metal inserts are
inserted into the mounting eyes.
12. A tensioning device of claim 1 wherein the housing and the
first sliding shoe are connected rigidly to each other by
integrally formed stiffening ribs.
13. A tensioning device of claim 1 wherein the tensioning piston
and the second sliding shoe are made in one piece with each
other.
14. A tensioning device of claim 13 wherein the tensioning piston
and the second sliding shoe are made of plastic.
15. A tensioning device of claim 14 wherein the plastic is
polyamide.
16. A tensioning device of claim 14 wherein the tensioning piston
is reinforced with fibers.
17. A tensioning device of claim 16 wherein the fibers are glass
fibers.
18. A tensioning device of claim 1 wherein the tensioning piston
comprises a recess for a spring which is supported at one end on
the housing and at another end on the tensioning piston.
19. A tensioning device of claim 18 wherein the spring is a coiled
compression spring.
20. A tensioning device of claim 1 wherein a transition from the
tensioning piston to the second sliding shoe in running directions
of the chain is configured as a flared enlargement.
21. A tensioning device of claim 1 wherein a transition from the
housing to the first sliding shoe in running directions of the
chain is configured as a flared enlargement.
Description
FIELD OF THE INVENTION
[0001] The present invention concerns tensioning devices,
particularly tensioning devices that can be used in the camshaft
drive of internal combustion engines.
BACKGROUND OF THE INVENTION
[0002] DE 196 51 091 A1, for example, discloses a tensioning device
for chains which comprises a housing having a hollow bore in which
a hollow piston is mounted for sliding and biased in outward
direction against the chain by a spring. On its chain-proximate
end, the piston carries a separate sliding shoe that is in contact
with the chain. The housing comprises a further sliding shoe that
is configured as a separate element and loads the side of the chain
situated opposite thereto. Sliding shoes are generally made of a
material having good sliding properties, preferably of plastic, and
are either slipped onto or formed by injection on the element
concerned. Both the housing and the tensioning piston are normally
made of metal. In such tensioning devices, measures for connecting
the sliding shoes that are preferably made of plastic, have to be
implemented both on the housing and on the tensioning piston. In
the aforesaid document, DE 196 51 091 A1, for example, the housing
comprises bores into which the material of the sliding shoes
penetrates to form an interlocked connection between the housing
and the sliding shoe.
OBJECTS OF THE INVENTION
[0003] It is an object of the invention to improve a tensioning
device of the pre-cited type so that it is simple and economic to
manufacture.
[0004] This and other objects and advantages of the invention will
become obvious from the following detailed description.
SUMMARY OF THE INVENTION
[0005] The invention achieves the above objects by the fact that
the housing and the sliding shoe are made in one piece with each
other. A particular advantage of this is that it is no longer
necessary to work with two or more materials but a single material
is sufficient to make both the housing and the sliding shoe. A
further advantage is that no special measures have to be
implemented on the housing to assure a reliable connection between
the housing and the sliding shoe. Still another advantage is that
one work step is totally dispensed with because the attachment of a
separate sliding shoe on the housing is no longer required.
[0006] According to a particularly favorable feature of the
invention, the first sliding shoe and the housing are made of
plastic, preferably polyamide. The housing and the first sliding
shoe can be injection molded in a common injection mold. Especially
for large series such as are required in the automobile sector, the
tensioning devices of the invention can be manufactured very
economically. It has been determined that the use of polyamide in
the present invention offers very great advantages.
[0007] For example, if the housing comprises a cylindrical recess
for the tensioning piston, the tensioning piston can be perfectly
guided on the cylinder wall and the good sliding properties of
polyamide permit a low-friction guidance. The material used for
making the sliding shoe must be tough and must possess high
abrasion resistance and good sliding properties. All these
requirements are met by polyamide. Since polyamide possesses
properties that meet the requirements made both of the housing and
the sliding shoe, it is obvious that this material is most suitable
for forming the housing and the sliding shoe together in one
piece.
[0008] Advantageously, the housing may be reinforced with fibers,
especially glass fibers. The glass fibers are inserted into the
part of the injection mold which is intended for the housing, while
the sliding shoe is preferably not reinforced.
[0009] If it is more advantageous for special uses to make the
housing and the sliding shoe of different materials or plastics,
this can be done without any problem using the two-component
injection method. In this method, a first plastic is filled into
the part of the injection mold meant for the sliding shoe and the
other material is filled into the part of the injection mold meant
for the housing. An integrally connected structure is assured.
[0010] Two mounting eyes can be provided in the housing through
which fixing means, particularly screws can be inserted. Normally,
engine blocks or cylinder heads of internal combustion engines
comprise threaded bores into which the screws can be screwed. This
enables a secure fixing of the housing on the engine block or the
cylinder head.
[0011] The mounting eyes can be lengthened by an integral formation
of sleeve-like extensions on the housing. This is intended to
assure that the housing cannot tilt on the shanks of the screws. It
can also be advantageous to strengthen the mounting eyes with metal
inserts which may be pressed, glued or welded in place or covered
with the plastic by injection.
[0012] If the housing and the first sliding shoe are made by
injection molding or casting, it is no problem to connect the
housing and the first sliding shoe rigidly to each other with the
help of integrally formed stiffening ribs. The stiffening ribs can
be provided in a simple manner in the injection mold.
[0013] In another embodiment of the invention, the tensioning
piston and the second sliding shoe are also made in one piece with
each other. Substantially the same advantages are obtained with
this one-piece structure as with the one-piece structure comprising
the housing and the first sliding shoe described above. Thus, in a
very economic embodiment of the tensioning device of the invention,
polyamide is chosen as the material for the tensioning piston and
the second sliding shoe as well. Ideally, the tensioning device of
the invention is therefore made entirely of one single
material.
[0014] Similar to the housing, if necessary, the tensioning piston
can also be reinforced with fibers, especially glass fibers.
[0015] The tensioning piston may comprise a recess for a spring,
particularly a coiled compression spring which is supported at one
end on the housing and at the other end on the tensioning piston.
Besides the advantage of saving space required for the spring, this
embodiment has the further advantage that the tensioning piston is
optimized for purposes of injection molding because the provision
of the recess leads to the formation of an annular cylindrical wall
of uniform wall thickness which can be manufactured in a perfect
manner. In the case of a solid tensioning piston, irregular cooling
can result in an undesired distortion of the piston.
[0016] The transition from the tensioning piston to the sliding
shoe in the running directions of the chain is preferably a flared
enlargement. In this way is not only a desired stiffening obtained
but notch effect is also excluded which should be avoided because
of the high-frequency vibratory loading.
[0017] For the same reasons, it is advantageous to configure the
transition from the housing to the first sliding shoe in the
running directions of the chain likewise as a flared
enlargement.
[0018] The invention will now be described more closely with the
help of three examples of embodiment illustrated in the five
appended figures.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] FIG. 1 is a top view of a tensioning device of the
invention,
[0020] FIG. 2 shows a modified tensioning device of the
invention,
[0021] FIG. 3 is a sectional representation along line III-III of
FIG. 2,
[0022] FIG. 4 is a sectional representation along line IV-IV of
FIG. 2, and
[0023] FIG. 5 shows a further tensioning device of the
invention.
DETAILED DESCRIPTION OF THE DRAWINGS
[0024] FIG. 1 shows a tensioning device of the invention which is
arranged between two parallel camshafts, not shown, of an internal
combustion engine. A chain 1 is wrapped round chain pulleys 2 each
of which is connected to one of the camshafts. The tensioning
device of the invention comprises a housing 3 in whose bore 4 a
tensioning piston 5 is arranged for longitudinal displacement. A
first sliding shoe 6 is integrally connected to the housing 3 and
bears against the slack side 7 of the chain 1. A second sliding
shoe 8 that is integrally connected to the tensioning piston 5
bears against the tension side 9 of the chain 1.
[0025] The transition from the tensioning piston 5 to the second
sliding shoe 8 and from the housing 3 to the first sliding shoe 6
are both configured as flared enlargements 10, 11 to guarantee
rigid connections of stable shape. The housing 3 further comprises
mounting eyes 12 which are lengthened by sleeve-like extensions 13
formed integrally on the housing in a direction perpendicular to a
plane enclosed by the chain.
[0026] The device further comprises stiffening ribs 14 that merge
integrally into the sleeve-like extensions 13 and the first sliding
shoe 6. In this way, the first sliding shoe 6 and the sleeve-like
extensions 13 are connected rigidly to the housing 3.
[0027] The housing 3, the first sliding shoe 6, the tensioning
piston 5 and the second sliding shoe 8 are all made of polyamide,
the housing 3 being reinforced with glass fibers, not shown, that
are embedded in the polyamide.
[0028] The tensioning piston 5 comprises a recess 15 in which a
coiled compression spring 16 is arranged that is supported at one
end on the housing 3 and at the other end on the tensioning piston
5. The tensioning piston 5, and with it the integrally formed
second sliding shoe 8, is biased against the tension side 9 of the
chain 1 by the spring force of the coiled compression spring 16. A
hydraulic damping device 17, known, per se, assures in a known
manner a damping of inward movements of the tensioning piston
5.
[0029] FIG. 2 shows a tensioning device of the invention similar to
the device of FIG. 1 but without a hydraulic damping element and
with a larger recess 18 for the coiled compression spring 16. The
tensioning piston 5 is shown both in a retracted and an extended
position.
[0030] As clearly discernible in FIG. 4, metal inserts 19 are
inserted into the mounting eyes 12.
[0031] The housing 3 comprises an oil feed bore 20 through which
engine oil is conveyed into the bore 4 of the housing 3. This
engine oil can flow out through a throttling bore 21 that is
provided in the tensioning piston 5 and ends on the surface of the
second sliding shoe 8. The out-flowing engine oil serves at the
same time to lubricate the chain.
[0032] The oil feed bore 20 and the throttling bore 21 can be
clearly seen in FIG. 3. This figure further shows a clip 22 that
holds the tensioning piston 5 and the housing 3 together in a
pre-determined position. After the assembly of the tensioning
device of the invention, the clip 22 is removed, so that the
tensioning piston 5 is biased against the chain by the force of the
coiled compression spring 16.
[0033] FIG. 4 clearly shows the metal inserts 19 that are inserted
into the mounting eyes 12 of the housing 3.
[0034] FIG. 5 shows a further tensioning device of the invention.
The essential difference of this device from the device of FIG. 1
is that a sliding shoe 24 made as a separate part is seated on a
tensioning piston 23.
* * * * *