Endless belt power transmission systems or components – Means for adjusting belt tension or for shifting belt,... – Tension adjuster has surface in sliding contact with belt
Reexamination Certificate
2001-01-22
2002-09-24
Bucci, David A. (Department: 3682)
Endless belt power transmission systems or components
Means for adjusting belt tension or for shifting belt,...
Tension adjuster has surface in sliding contact with belt
C074S57700S, C074S533000
Reexamination Certificate
active
06454672
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a ratchet tensioner used to provide an appropriate tension to a timing belt or a timing chain of a vehicle engine, and more particularly to a ratchet tensioner having a mechanism for locking and releasing a plunger.
2. Description of the Related Art
The ratchet tensioner has been widely used for suppressing vibrations generated when a timing belt or a timing chain is traveling to transmit rotation between a crankshaft and a camshaft of an engine, and for maintaining an appropriate tension in the timing belt or chain. Such ratchet tensioner is constructed such that a plunger protruding from a housing of the tensioner presses the rear side of a free end portion of a tensioner lever pivotally mounted to a body of the engine, so that a shoe surface of the tensioner lever slidably contacts with a slack side of the chain to give an appropriate tension to the chain (see Japanese Patent Publication No. HEI-3-8415, Japanese Patent Laid-Open Publication No. HEI-10-2386, and Japanese Patent Laid-Open Publication No. HEI-11-344086).
A typical example of the known ratchet tensioners is shown in
FIGS. 6 and 7
. The tensioner
31
includes a housing
32
, a plunger
33
slidably mounted in the housing
32
and urged by a plunger spring
36
so that one end
33
A of the plunger
33
projects outward from the front surface of the housing
32
. The tensioner
31
further has a ratchet pawl body
34
pivotally mounted by a shaft
34
A to the housing
32
. The ratchet pawl body
34
is received in a recess
32
E defined between opposed side walls
32
C,
32
D in the housing
32
, and urged by a ratchet pawl spring
38
. The ratchet pawl body
34
has a ratchet pawl
34
B engaged with a ratchet tooth
33
B formed on a side surface of outer periphery of the plunger, so that a backward displacement of the plunger
33
is suppressed.
The ratchet tensioner
31
includes a buffer mechanism using a flow resistance of oil, and a backlash is maintained between the ratchet tooth
33
B and the ratchet pawl
34
B, so that the oil (not shown) is introduced into the interior of the plunger
33
from an external oil pump operating in synchronism with the engine via a check valve mechanism
35
. When the plunger
33
receives shock from the tensioner lever, the plunger
33
is retracted against the force of a plunger spring
36
within a range of the backlash in a state that the ratchet tooth
33
B and the ratchet pawl
34
B are engaged. At that time, the check valve mechanism
35
is closed to leak the oil in the plunger
33
from between the outer peripheral surface of the plunger
33
and the inner peripheral surface of a plunger-accommodating hole of the housing
32
, so that a shock force is relieved. Furthermore, reference numeral
32
B in
FIGS. 6 and 7
indicates a mounting hole for mounting the ratchet tensioner
31
to the engine body.
Additionally, the ratchet tensioner
31
comprises a plate
37
secured to an end of the shaft
34
A of the ratchet pawl body projecting outside the housing
32
. When the ratchet tensioner
31
is shipped or to be mounted to the engine, as shown in
FIGS. 8 and 9
, a stopper pin
39
is inserted into a pin inserting hole
37
A of the plate
37
to contact with an outer wall end surface
32
A of the housing
32
in a state that the ratchet tooth
33
B and the ratchet pawl
34
B are engaged, and thus the plunger
33
is retained so as not to fly out from the housing
32
. In this case, after mounting the ratchet tensioner
31
to the engine, the stopper pin
39
is removed to place the tensioner
31
in an operating condition.
Furthermore, as other means for holding the plunger
33
in position against movement in the projecting direction when shipping the ratchet tensioner, as shown in
FIGS. 10 and 11
, the ratchet pawl body
34
is rotated by the rotation of the outer plate
37
to engage the ratchet tooth
33
B with the ratchet pawl
34
B, and then the stopper pin
39
is inserted through the pin inserting hole
37
A of the outer plate
37
into a stopper hole
32
C formed in the housing
32
.
In the ratchet tensioner, it is necessary to pull in the plunger
33
that has been projected in case of repairing the engine, removing or mounting the chain. However, the prior ratchet tensioner has problems that the plunger
33
cannot be pushed simply into the interior of the housing, and the work for removing or mounting the chain cannot be performed simply, since the outer plate
37
is rotated to rotate the ratchet pawl body
34
so that it is possible to release the engagement of the plunger
33
serving as one-way mechanism, but there is not a mechanism for maintaining the state in that the engagement is released. Furthermore, it is difficult to insert a driver from a small window hole such as an engine service hole etc., for rotating the outer plate, and it is not capable of maintaining the disengagement state of the plunger. The ratchet tensioner further has problem that an extra component is necessary since the outer plate, which is a separate member, is mounted to a ratchet shaft secured to the ratchet pawl body.
SUMMARY OF THE INVENTION
Therefore, in view of the aforementioned problems, an object of the present invention is to provide a ratchet tensioner which is capable of rotating a ratchet pawl body in a direction to engage a ratchet pawl with a ratchet tooth formed on a plunger, thereby maintaining the plunger in its engaged state, or being capable of rotating the ratchet pawl body in the other direction to disengage a ratchet pawl from a ratchet tooth on the plunger, thereby easily releasing the engagement of the plunger and easily maintaining the plunger in its disengaged state, or being capable of rotating the ratchet pawl body in a direction or the other direction to engage a ratchet pawl with a ratchet tooth on a plunger, thereby maintaining the plunger in its engaged state or being capable of rotating the ratchet pawl body in the other direction to disengage a ratchet pawl with a ratchet tooth on the plunger, thereby easily releasing the engagement of the plunger and easily maintaining the plunger in its disengaged state.
To accomplish the above object, according to a first aspect of the present invention, there is provided a ratchet tensioner comprising: a housing having two opposed side walls defining therebetween a recess; a plunger retractably mounted in the housing with one end projecting outward from the housing, the plunger having a series of ratchet teeth formed on an outer peripheral surface of the plunger, a plunger spring acting between the housing and the plunger and urging the plunger in a direction to project outward from the housing; a ratchet pawl body received in the recess of the housing and pivotally mounted by a shaft to the housing, the ratchet pawl body having a ratchet pawl formed at one end of the ratchet pawl body; a ratchet pawl spring acting between the housing and the ratchet pawl body and urging the ratchet pawl body to turn about the axis of the shaft in a direction to engage the rachet pawl with the ratchet teeth on the plunger, thereby preventing the plunger from moving backward; and a plunger locking mechanism for locking the plunger in position against movement relative to the housing. The plunger locking mechanism has a lever-like pin contact portion formed integrally with the other end of the ratchet pawl body, a pin member-fitting hole formed in the opposed side walls of the housing in registry with the lever-like pin contact portion of the ratchet pawl body such that there being two pin-accommodating spaces defined between the lever-like pin contact portion and an inner peripheral surface of the pin member-fitting hole on opposite sides of the lever-like pin contact portion, and a pin member removably inserted in one of the pin-accommodating spaces to turn the ratchet pawl body in one direction to keep the engagement between the ratchet pawl and the ratchet teeth on the plunger.
According to a second aspect of the present invention
Bucci David A.
Dann Dorfman Herrell and Skillman
Johnson Vicky A.
Skillman Henry H.
Tsubakimoto Chain Co.
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