[0001] The present invention relates to a silencer device to reduce noises and sounds generated
by exhaust gases in otto- or diesel-cycle engines, when an exhaust brake is applied
to said engines.
[0002] Various exhaust-brake devices are currently being used on internal combustion engines,
suitable to increase the braking effect of the engine, transforming the engine itself
into an air compressor.
[0003] The fuel supply is eliminated:
- in injection engines through a direct control ("engine stop" control already existing),
that zeroes the flow-rate of the injection pump;
- in carburation engines, opening an air intake of the atmosphere to the induction manifold
(lateral passage to the carburettor): with this, the fuel induction stops and there
occurs, like in diesel engines, a free intake of fresh air.
[0004] The inconvenience with said exhaust brakes is the noise generated by the expansion,
in exhaust ducts, of the air compressed by the pistons, that cannot be dampened by
the exhaust muffler, since it is designed to absorb the sound waves produced by the
combustion burst.
[0005] In fact, the gases burnt in internal combustion engines, that cyclically flow into
the exhaust manifold through the exhaust valves, produce, when the valves are being
opened, a deafening noise with free exhaust; therefore, to reduce this free exhaust
noise, an exhaust muffler is applied to the exhaust pipe end. This muffler, built
for that purpose, has no effect when the fuel supply is stopped when it is time to
operate on the exhaust brake: the combustion noise is then replaced by the noise of
the compressed air going out of the exhaust manifolds and expanding; this noise, being
of a different nature and frequency from the one typical of the combustion, will not
be able to be absorbed by the traditional exhaust muffler.
[0006] Purpose of the present invention is eliminating or substantially reducing the noise
generated by the air compressed by the pistons of an internal combustion engine, when
this is subjected to the exhaust brake action, operating upstream of the muffler and
in series with it, exploiting the principle of sound energy (and therefore noise)
reduction, through the wave reflection on the conducing pipe walls, following diameter
variations of the pipes themselves (it is in fact known that the increase of a pipe
section generates the decrease of low-frequency noises).
[0007] Another purpose is of the device is being suitable to any diameter of exhaust manifolds
and mufflers connected to it, and therefore being able to be used for any engine displacement.
[0008] A further purpose of the device is being easily manufactured at low costs, due to
assembling rationality and linearity.
[0009] The above purposes of the invention are reached by a silencer device operating on
the compressed air that expands in exhaust ducts of internal combustion engines (otto
or diesel ones) equipped with exhaust brake, characterized in that it is composed
of a hollow body whose shape is substantially spheroidal and whose section is approximately
ovoidal, assembled downstream of the exhaust manifold of the engine and upstream of
the muffler, and equipped with an inlet opening and an outlet opening connected, through
adequate ducts, to exhaust manifold and muffler, respectively.
[0010] According to another characteristic of the invention, the inlet and outlet openings
of the silencer can lay not on the same axis.
[0011] According to a further characteristic of the invention, the silencer axis can be
not perpendicular to the exhaust manifold and the muffler ones, and can be raking
with respect to them.
[0012] A preferred embodiment of the invention will now be described, as a non-limiting
example, with reference to the enclosed drawings, in which:
- fig. 1 is a diagrammatic front view of the device;
- fig. 2 is a diagrammatic view along the section II-II of the device in fig. 1;
- fig. 3 is a diagrammatic side view of the device in fig. 1 in its preferred operating
assembly on a vehicle.
[0013] Referring to fig. 2 and 3, the device 1 is composed of a hollow body 3, usually made
of steel, whose shape is substantially spheroidal and whose section is approximately
ovoidal, equipped with an inlet opening 5 connected, through a duct 7, to the exhaust
mainfold 9 of the turbo 10ΜΈ of the engine 11 equipped with an exhaust brake 12, and
with an outlet opening 13 connected, through a duct 15, to the muffler 17. The compressed
air going out of the manifold enters into the device 1 from the inlet opening 5 and,
since the section of the device 1 is greater than that of the exhaust manifold 9 and
of the muffler 17, and since said opening 5 does not lay on the same axis as that
of the outlet one 13, and since the axis of the device 1 is raking with respect to
those of the two openings 5 and 13, said air reflects expanding inside the hollow
body 3, losing kinetic energy, and the sound waves related to it are damped; the compressed
air that expands in the exhaust ducts, afterwards, gose out through the outlet opening
13 towards the muffler 17.
1. Silencer device (1) operating on the exhaust gases of internal combustion engines
(otto or diesel ones) (11) equipped with exhaust brake (12), characterized in that
it is composed of a hollow body (3) whose shape is substantially spheroidal and whose
section is approximately ovoidal, assembled downstream of the exhaust manifold (9)
of the engine (11) and upstream of the muffler (17), and equipped with an inlet opening
(5) and an outlet opening (13) connected, through adequate ducts (7, 15), to exhaust
manifold (9) and muffler (17), respectively.
2. Silencer device according to claim 1, characterized in that the inlet opening (5)
and the outlet opening (13) do not lay on the same axis.
3. Silencer device according to claim 1 or 2, characterized in that the axis of the silencer
device (1) is not perpendicular to the exhaust manifold (9) and the muffler (17) ones,
but is raking with respect to them.
