Endless belt power transmission systems or components – Means for adjusting belt tension or for shifting belt,... – Tension adjuster or shifter driven by electrical or fluid motor
Reexamination Certificate
2002-01-10
2004-11-02
Charles, Marcus (Department: 3682)
Endless belt power transmission systems or components
Means for adjusting belt tension or for shifting belt,...
Tension adjuster or shifter driven by electrical or fluid motor
C474S109000
Reexamination Certificate
active
06811505
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a hydraulic tensioner for imparting a proper tension to a traveling chain, belt or the like, and particularly to a hydraulic tensioner in which the dropping-out of a metallic cylinder fitted into a cylindrical hole formed in the body of the tensioner is prevented by use of a compression spring provided so as to protrude the tip of a plunger from the body without fixing the cylinder by a separate fixing member or the like.
2. Description of the Prior Art
FIG. 6
shows a conventional hydraulic tensioner
51
as an example. This hydraulic tensioner
51
comprises an iron-based plunger
54
slidably fitted into a cylinder chamber
53
formed in an iron-made or aluminum alloy-made body
52
.
A hollow part
55
opened at the lower end is formed within the plunger
54
, and a compression spring
56
for energizing the plunger
54
to impart a proper tension to a chain, belt or the like (not shown) is housed in the hollow part
55
. A pressure oil chamber
57
is formed by the hollow part
55
and the cylinder chamber
53
of the body
52
, and a check valve
58
allowing the inflow of oil to the pressure oil chamber
57
but arresting the back flow thereof is provided on the bottom of the pressure oil chamber
57
.
The check valve
58
is formed of a ball seat
59
pressed into a cylindrical hole
63
in the lower part of the pressure oil chamber
57
, a check ball
61
provided on the upper part of the through-hole
60
of the ball seat
59
, a coil spring for energizing the check ball
61
toward the through-hole
60
, and a retainer
62
for supporting the end of the coil spring, and the check ball
61
functions as check valve.
The pressure oil chamber
57
is regularly filled with the oil externally supplied from an inlet port
64
and the through-hole
60
by a pump or the like through the check valve
58
. When the traveling chain, belt or the like gets loose, the plunger
54
regularly energized by the compression spring
56
is protruded, and the check valve
58
is opened to allow the oil to flow into the pressure oil chamber
57
. When the plunger
54
is pushed into the cylinder chamber
53
by an impact force worked from the chain, belt or the like to the tensioner, the oil pressure in the pressure oil chamber
57
is raised to close the check valve
58
.
When the check valve
58
is closed, the oil in the pressure oil chamber
57
is released from the lower end of the plunger
54
through a clearance (slight space) between the outer surface of the plunger
54
and the inside surface of the cylinder chamber
53
and discharged to the outside. At this time, the impact energy is absorbed by the flowing resistance of the oil passing through the clearance, and a cushion effect can be obtained.
However, since the body
52
consists of a die cast product of cast iron or aluminum alloy, the conventional hydraulic tensioner
51
has the problem of requiring film formation by coating, smoothing treatment, machining or the like to ensure the surface precision or durability of the cylinder chamber for sliding the plunger for the purpose of preventing the wear and seizure of the plunger. Further, it requires an improvement in precision of the cylindrical hole
63
since the ball seat
59
constituting the check valve
58
is pressed into the cylindrical hole
63
formed in the lower part of the pressure oil chamber
57
, which causes the problem of requiring the machining therefor.
When the surface precision and durability of the cylinder chamber is inferior as described above, it is also proposed to clearance-fit a metallic cylinder of separate part into the cylindrical hole formed in the body (Japanese Patent Application Laid-Open No. 2000-346152). In this case, however, it is necessary to form an annular recessed groove on the inside surface of the cylindrical hole and mount a snap ring on the recessed groove for the prevention of dropping-out of the cylinder, resulting in the necessity of processes for groove formation, snap ring mounting and the like, which increases the manufacturing cost for this portion.
Since the body consisting of the die cast product of cast iron, aluminum alloy or the like is heavyweight, it is also considered to make the body of plastics in order to reduce the weight. However, the insert molding of a reinforcing part such as metallic cylinder or the like is required because of the presence of problems such as insufficient durability of the sliding surface with the plunger, insufficient strength of each part or the like, causing the problem of complicating a metal mold to increase the cost. Further, a looseness is caused in a temperature rise by the difference in thermal expansion coefficient with a press-in member such as the ball seat of the check valve, so that high-pressure oil cannot be supplied to the pressure oil chamber.
SUMMARY OF THE INVENTION
In order to solve the problems of the prior arts as described above, this invention has objects to facilitate the mounting of a cylinder and the assembling of a tensioner by dispensing with the film formation, smoothing treatment, machining or the like of a cylinder chamber for sliding a plunger on the body of the tensioner and also dispensing with machining of hole surface or the like in the fitting of the metallic cylinder of separate article, and to prevent the dropping-out of the cylinder by use of a compression spring provided so as to protrude the plunger from the body without requiring any cylinder fastener such as snap ring of separate member. Further, it has objects to prevent also the dropping-out of a check valve mechanism by use of the bottom plate of the cylinder in the mounting of the check valve mechanism and to facilitate the assembling thereof.
In order to attain the above objects, a hydraulic tensioner according to a first aspect of this invention comprises a metallic cylinder fitted to a cylindrical hole formed in a body, a plunger provided within the cylinder so as to be energized by a compression spring to protrude the tip from the body, and a pressure oil chamber formed between the inner part of the plunger and the cylinder, wherein the cylinder is provided with a bottom plate having a through-hole allowing the inflow of oil in the center, and the bottom plate is prevented from dropping out from the body by being energized by the compression spring.
According to a second aspect of this invention, in the hydraulic tensioner of the first aspect, the cylindrical hole is provided with a cylindrical hole smaller in diameter than this cylindrical hole on the bottom side, and a check valve mechanism fitted to the minor diameter cylindrical hole is prevented from dropping out by the abutment on the bottom plate of the cylinder.
According to a third aspect of this invention, a hydraulic tensioner comprising a metallic cylinder fitted to a cylindrical hole formed in a body, a plunger provided within the cylinder so as to be energized by a compression spring to protrude the tip from the body, a pressure oil chamber formed between the inner part of the plunger and the cylinder, and a check valve mechanism allowing the inflow of oil to the pressure oil chamber but arresting the back flow thereof, wherein the cylinder is provided with a bottom plate having a through hole allowing the inflow of oil in the center, and the bottom plate being prevented from dropping out from the body by being energized by the compression spring, the check valve mechanism comprises a check ball provided so as to block an inflow hole of oil to the pressure oil chamber from above and a spring for energizing the check ball and the spring is supported by the bottom plate, is provided.
Further, according to a fourth aspect of this invention, a hydraulic tensioner according to the third aspect, wherein the check valve mechanism further comprises a lid for supporting the spring and being a preliminary assembled product, and the lid is supported by the bottom plate, is provided.
A hydraulic tensioner according to a fifth aspect of this invention c
Hashimoto Hiroshi
Miyake Hiroyuki
Charles Marcus
Dann Dorfman Herrell and Skillman
Skillman Henry H.
Tsubakimoto Chain Co.
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