Endless belt power transmission systems or components – Means for adjusting belt tension or for shifting belt,... – Load responsive tension adjuster or shifter
Reexamination Certificate
2001-01-22
2003-09-02
Charles, Marcus (Department: 3682)
Endless belt power transmission systems or components
Means for adjusting belt tension or for shifting belt,...
Load responsive tension adjuster or shifter
C474S110000
Reexamination Certificate
active
06612951
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. 5 and 6
. 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
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. 5 and 6
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. 7 and 8
, 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. 9 and 10
, 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.
SUMMARY OF THE INVENTION
Therefore, in view of the aforementioned problems, an object of the present invention is to provide a ratchet tensioner including a plunger locking and releasing mechanism which is capable of holding a plunger selectively in a locking position where a ratchet pawl on the ratchet pawl body is in interlocking engagement with ratchet teeth on the plunger, and in a releasing position in which the ratchet pawl is disengaged from the ratchet teeth.
To accomplish the above object, according to the present invention, there is provided a ratchet tensioner comprising: a housing; 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 thereof; 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 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 and releasing mechanism for selectively locking and releasing the plunger with respect to the ratchet pawl.
The plunger locking and releasing mechanism has a pin-accommodating hole formed in an outside surface of the housing, an actuator plate disposed above the outside surface of the housing and secured to the shaft of the ratchet pawl body for co-rotation with the shaft and the ratchet pawl body, the actuator plate having a pin-insertion hole of a diameter smaller than the pin-accommodating hole, the actuator plate being manually movable about the axis of the shaft in opposite directions between a locking position in which the pin-insertion hole is in substantial alignment with the pin-accommodating hole and the engagement between the ratchet pawl and the ratchet teeth is maintained, and a releasing position in which the pin-insertion hole is out of alignment with the pin-accommodating hole, and the ratchet pawl is released from interlocking engagement with the ratchet teeth against the force of the ratchet pawl spring, a stopper pin removably inserted into the pin-accommodating hole either through the pin-insertion hole to keep the actuator plate in the locking position, or alternatively directly, with an outer edge of the actuator plate being in contact with the stopper pin, to keep the actuator plate in the releasing position.
In the ratchet tensioner of the foregoing constitution, the actuator plate is rotated to maintain interlocking engagement between the ratchet pawl and the ratchet tooth, so that the stopper pin is inserted into a pin-inserting hole of the actuator plate and a pin-accommodating hole of the housing, thereby maintaining the plunger in its engaged state. The plunger is prevented from moving forward in the projecting direction. When the actuator plate is rotated to disengage the ratchet pawl from the ratchet tooth,
Charles Marcus
Dann Dorfman Herrell and Skillman
Skillman Henry H.
Tsubakimoto Chain Co.
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