Field of Invention
[0001] The present invention relates to a tensioning apparatus for
an internal combustion engine and, more particularly, to a tensioning apparatus for a chain drive of an internal combustion engine such as an oil pump chain drive, the said tensioning device having a tensioning arm preloaded by a spring device and mounted to a support point.
Description of Prior Art
[0002] In an internal combustion engine, the burning of air-fuel
mixture takes place inside the engine cylinder. This combustion forces the piston residing in the cylinder block to reciprocate and hence rotate the crankshaft. This process generates enormous pressure and heat. To operate the engine within the optimal temperature range, cooling oil routes are provided which is sprinted by an oil pump.
[0003] Generally oil pumps are driven by a chain drive coupled to
them by known means. A chain drive such as the oil pump chain of automobile engine, is used for transmitting rotation between two or more spaced shafts. Chain drives generally have a slack side. This slack can hamper the performance of the engine by causing vibrations and noise and by not responding or by delaying response when needed. A tensioner lever is therefore commonly employed in internal combustion engines to remove slack.

[0004] Fig. 6 shows one example of a conventional tensioner lever
used in internal combustion engines. The tensioner lever A1 is rotatably
supported on a mount surface R of an engine body by means of a pivot
shaft A2. A shoe surface S provided in a longitudinal direction of the
tensioner lever A1 is adapted to be held in sliding contact with the outer
circumferential surface of a slack run of an endless chain A3. A torsion coil
spring A5 is wound around and supported by a support pin A4 projecting
from the mount surface R. The torsion coil spring A5 has one arm a
engaged with a surface of the tensioner lever which is located on a side
opposite to the shoe surface S. The other arm b of the torsion coil spring
A5 is in engagement with a retaining member Q provided on the mount
surface R. By the force of the torsion coil spring S5, the tensioner lever A1
is urged to turn about the pivot shaft A2 in the clockwise direction shown in
Figure 6. As a result, the shoe surface S presses or forces at all times the
outer peripheral surface of the chain slack side toward the interior side of
the chain A3, thereby preventing the chain from becoming loose.
However, in this arrangement, since the torsion coil spring A5 and the
spring support pin A4 are disposed on a side of the tensioner lever A1,
these parts requires greater installation space on the mount surface R
which is provided on the exterior side of the endless chain A3.
[0005] Fig. 7 and Fig. 8 illustrates another example of a
conventional tensioner lever. The illustrated tensioner lever B1 has the same function as the tensioner lever A1 show in Fig. 6 but differs in this

regard that a torsion coil spring B3 used for urging a shoe surface S
against a chain B2 has a helically coiled portion supported concentrically
with a pivot shaft B4 on which the tensioner lever B1 is rotatably
supported with respect to a mount surface R. As shown in Fig. 8,
tensioner lever B1 has a boss B5 projecting toward the mount surface R.
The coiled portion of the torsion coil spring B3 is fitted around the boss B5.
One arm a' of the torsion coil spring B3 is engaged with the tensioner lever
B5, and the other arm b' of the tensioner lever B1 is engaged with a spring
retainer pin B6 projecting from the mount surface R. In the conventional
tensioner lever B1 shown in Fig. 7 and Fig. 8, since the torsion coil spring
B3 is supported on the pivot shaft B4 together with the tensioner lever B1,
space for installation of these parts on the mount surface R is relatively
small. However, due to the provision of the boss B5 disposed between the
tensioner lever B1 and the mount surface R, the overall height of the
tensioner lever B1 as measured from the mount surface R is made large.
Additionally, in the foregoing conventional tensioner levers, since the
torsion coil spring is assembled with the tensioner lever when the
tensioner lever is mounted to the mount surface, the assemblage of the
conventional tensioner levers is relatively low in efficiency.
[0006] It would therefore by very desirable to have a tensioning
apparatus which consumes very less space when installed, is suitable for series manufacture and that which can be easily and speedily assembled onto the mount surface.

into pressure contact with the chain drive thereby preventing slackening of the chain drive.
[0009] These and other features, aspects, and advantages of the
present invention will be better understood with reference to the following description, the appended claims and the accompanying drawings. This summary is not intended to limit the scope of the claimed subject matter.
Brief Description of Drawings
[0010] The above and other features, aspects, and advantages of
the present invention are further illustrated by the accompanying drawings.
The drawings are given by way of illustration only and are not limitative of
the present invention. A brief description of the drawings is as follows:
Fig. 1 illustrates a side view of a conventional three-wheeled vehicle.
Fig. 2 illustrates a front view of an internal combustion engine integrated
with the present invention.
Fig. 3 illustrates a top view of the present invention mounted to a chain
drive.
Fig. 4 illustrates an isometric view of the present invention.
Fig. 5(a) illustrates an isometric view of the tensioner guide as per the
present invention.
Fig. 5(b) illustrates an isometric view of the torsion spring as per the
present invention.

Fig. 5(c) illustrates an isometric view of the tensioner mounting bolt as per
the present invention.
Fig. 6 illustrates a front view of a chain drive coupled with a conventional
tensioning apparatus.
Fig. 7 illustrates a front view of a chain drive coupled with another
conventional tensioning apparatus.
Fig. 8 illustrates a sectional view of the chain drive tensioning apparatus
illustrated in Fig.7
Detailed Description of Invention
[0011] The present invention is hereinafter described with reference
to the accompanying drawings. It is to be noted that like reference
numerals designate corresponding or identical elements throughout the
various drawings. The terms front and rear, and left and right as used
indicate the front and rear and the left and right directions when viewed by
a rider seated on a vehicle seat. For the sake of explanatory convenience,
the present invention will be described hereinafter as being embodied in
an internal combustion engine used in a three-wheeled vehicle.
[0012] Fig. 1 illustrates the side view of a typical three wheeled
passenger carrier vehicle 100, driven by an internal combustion engine (not shown in the drawing). It has a front panel 101 along with a windscreen 102. The lower portion of the front panel 101 is connected to a front wheel 104 with a wheel cover 103 stationed in between. A handle bar

assembly 109 which is used to operate the three-wheeled vehicle 100 is
provided behind the front panel 101. The three-wheeled vehicle 100 is
laterally divided into two halves, along line A-A, the first half comprises a
driver's seat 107, while the second half has a long passenger seat 108
with a seating capacity of minimum three passengers. The internal
combustion engine is located below the passenger seat 108. The rear
panel 106 along with the second half of the vehicle containing the
passenger seat 108 is supported on a pair of rear wheels 105 located on
either side of the longitudinal axis of the three-wheeled vehicle 100.
[0013] Fig. 2 demonstrates the present invention integrated to an
internal combustion engine. Fig.2 is a front view of the engine open from
right hand side. As shown, a crankcase 200 is installed with the chain
drive tensioner apparatus 300 as per the present invention. A crankshaft
340 coupled with a drive sprocket 301 propels a chain drive 330, which in
turn rotates a driven sprocket 310 to pump oil through an oil pump 210.
[0014] Fig. 3 illustrates a top view of the present invention mounted
to the slack side of the chain drive 330. As aforementioned, the chain drive 330 is in mesh with a drive sprocket 301 mounted on the crankshaft 340, and a driven sprocket 310, mounted on a shaft 350 for driving the oil pump 210.
[0015] Fig. 4 illustrates the tensioner apparatus 300 as per the
present invention. The tensioner apparatus 300 comprises a tensioner guide 400, a torsion spring 420 and a tensioner mounting bolt 410. The

tensioner guide 400 has a curved side wall 510 extending in the longitudinal direction and an end wall 511 perpendicular to the curved side wall 510. The curved side wall 510 and the end wall 511 form boundaries of a contoured inner peripheral surface. The contoured inner peripheral surface makes sliding contact with the chain drive 330. The tensioner mounting bolt 410 pivotally mounts the tensioner guide 400 and anchors it to the crankcase by way of a plurality of coaxial through holes 520 formed on the end wall 511. The torsion spring 420 is wound around the outer surface of the tensioner mounting bolt 410. As shown, a tensioner guide groove 430 formed on the curved side wall 510 of the tensioner guide 400 accommodates one end of the torsion spring 420. The other end of the torsion spring is provided with a bend 440 to facilitate the oscillatory motion of tensioner guide 400.
[0016] Fig. 5(a) illustrates an isometric view of the tensioner guide
400. The tensioner guide 400 has a body 500 molded of synthetic resin and pivotally mounted at its one end to a crankcase 200 by means of a tensioner mounting bolt 410. The tensioner mounting bolt 410 is coupled with the body 500 through the plurality of coaxial through holes 520 formed on the body 500. The body 500 is urged by the force of a torsion spring 420 to turn about an axis of the pivot tensioner mounting bolt 410 in a direction to force the curved surface 510 into pressure contact with the chain drive 330 thereby preventing the chain drive 330 from becoming slack or loose.

[0017] Fig. 5(b) illustrates an isometric view of the torsion spring
420. A coiled portion 563 of the torsion spring 420 is wound loosely on the
outer circumferential surface 552 of the tensioner mounting bolt 410, which
is coaxial with the plurality of through holes 520 in the body 500. A
cylindrical extension 561 of the torsion spring 420, which is a continuation
of the coiled portion 563 of the torsion spring 420, is seated in the
tensioner guide groove 430, as shown in Fig. 4 so that it can press against
the inside of a portion of the side wall of the body 500 on which the curved
surface 510 is formed. A bend 440, at the opposite end of the torsion
spring 420 and also continuous with the coiled portion 563, extends out of
the body 500, so that a part of bend 440 can be coupled with crankcase
200. When the cylindrical extension 561 is engaged with the tensioner
guide groove 430, the bend 440 coupled with crankcase 200 generates a
torque which biases the lever about its tensioner mounting bolt 410, so
that the curved surface 510 of the tensioner guide 400 presses against
chain drive 330 consequently restricting the slack in chain drive 330.
[0018] Fig. 5(c) illustrates an isometric view of the tensioner
mounting bolt 410. Numeral 551 is designated to the head of tensioner mounting bolt 410. Underneath the head 551 is the smooth cylindrical portion 552 of the tensioner mounting bolt 410, this portion facilitates the mounting of torsion spring 420 and further provides latitude for the movement of torsion spring 420. The tensioner mounting bolt also has a

grooved portion 553 which fastens the tensioner apparatus 300 to the crankcase 200.
[0019] The foregoing description is a specific embodiment of the
present invention and has been described for the purpose of illustration only. Persons skilled in the art may practice numerous alterations and modifications of the present invention without departing from its spirit and scope. It is intended that all such modifications and alterations be included insofar as they come within the scope of the invention as claimed or the equivalents thereof.

We claim:
1. A tensioner apparatus 300 for a chain drive 330 of an internal
combustion engine, said tensioner apparatus 300 comprising:
a tensioner guide 400 having a curved side wall 510 extending in the longitudinal direction thereof and an end wall 511 perpendicular to the curved side wall 510, said end wall 511 and said curved side wall 510 forming boundaries of a contoured inner peripheral surface which enables sliding contact with the chain drive 330, said tensioner guide 400 pivotaliy mounted and anchored to a mount surface by a tensioner mounting bolt 410, said tensioner mounting bolt 410 received by a plurality of coaxial through holes 520 formed on one end of the end wall 511;
a torsion spring 420 having a coiled portion 563 wound around an outer circumferential surface 552 of the tensioner mounting bolt 410, said torsion spring having a bend 440 at its one end and a cylindrical extension 561 at its other end, said bend 440 secured to the mount surface and said cylindrical extension 561 seated in a tensioner guide groove 430 formed on the curved side wall 510.
2. The tensioner apparatus 300 for a chain drive 330 of an internal
combustion engine as claimed in claim 1, wherein said tensioner
mounting bolt 410 further comprises a head portion 551 and a
grooved portion 553, said grooved portion 553 secures the
tensioner apparatus 300 to the mount surface.

3. The tensioner apparatus 300 for a chain drive 330 of an internal combustion engine as claimed in claim 1 or claim 2, wherein said mount surface is a crankcase 200.
4. The tensioner apparatus 300 for a chain drive 330 of an internal combustion engine as claimed in claim 1, wherein said chain drive 330 is preferably an oil pump chain drive.
5. The tensioner apparatus 300 for a chain drive 330 of an internal combustion engine as claimed in claim 1,wherein the torsion spring 420 forces the curved side wall 510 into pressure contact with the chain drive 330 thereby preventing slackening.
6. The tensioner apparatus 300 for a chain drive 330 of an internal combustion engine as hereinabove described in the specification and illustrated in the accompanying drawings.