Internal-combustion engines – Cooling – With cooling of additional parts or materials
Reexamination Certificate
2000-11-07
2002-03-26
Kamen, Noah P. (Department: 3747)
Internal-combustion engines
Cooling
With cooling of additional parts or materials
C123S041330, C123S1960AB
Reexamination Certificate
active
06360702
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a system for cooling an EGR (exhaust gas recirculation) gas and lubrication oil with engine cooling water.
2. Description of the Related Art
Systems for cooling an EGR gas with engine cooling water are known in the art. By cooling the EGR gas, the gas density is raised and EGR efficiency is improved. This type of conventional systems is called an EGR cooler, and one example thereof is disclosed in Japanese Patent Application, Laid Open Publication No. 10-169514 and illustrated in
FIG. 8
of the accompanying drawings.
The EGR cooler
70
includes a generally cylindrical casing
72
extending between an exhaust gas line of an engine (exhaust manifold) and an intake air line (intake manifold). The casing
72
is divided into three chambers, namely, a gas inlet chamber
74
, cooling water chamber
76
and gas outlet chamber
78
, by two partition walls
80
. A plurality of heat exchange pipes
82
extend in the cooling water chamber
78
and span the partition walls
80
. The cooling water chamber
76
has a cooling water inlet
84
for introducing part of water, which is primarily used for cooling an engine, into the cooling water chamber. The cooling water chamber
76
also has a cooling water outlet
86
for discharging the water therefrom. An air ventilation
88
is further provided on the cooling water chamber
76
for allowing air, which is generated from the heated water, to escape from the cooling water chamber
76
.
When the exhaust gas (high temperature gas) discharged from the exhaust manifold is partly recirculated to the intake manifold by an EGR line, that exhaust gas flows in the heat exchange pipes
82
and is cooled by the cooling water flowing in the cooling water chamber
76
. This raises gas density of the exhaust gas and in turn EGR efficiency.
The EGR cooler
70
should be located between the exhaust and intake manifolds, but there is a cylinder head near the manifolds. Thus, only a limited space is available for the EGR cooler
70
. Further, an engine hood and other structures associated with a vehicle body also exist in this area. In actuality, therefore, it is sometimes difficult to install the EGR cooler
70
.
Moreover, since the cooling water is taken from the engine, introduced into the EGR cooler
70
and returned to the engine again, water pipes are required to connect the engine to the water inlet
84
and the water outlet
86
to the engine and at least one air pipe is needed for the air outlet
88
. These pipes are subjected to vibrations when the engine is running and vehicle is cruising, and may have crack. To avoid it, the pipes must be firmly secured onto the engine with brackets and the like.
In addition, the EGR cooler
70
is completely independent from an oil cooler for cooling an engine lubrication oil, if any, so that it is not possible for the EGR gas to heat the lubrication oil (engine oil) in the oil cooler. Viscosity of the engine oil is generally low at low temperature starting.
Japanese Patent Application Laid-Open Publication No. 10-2256 discloses an EGR gas cooler using engine cooling water, and 7-42628 discloses an EGR gas cooler attached to a lateral wall of a cylinder block.
SUMMARY OF THE INVENTION
An object of the present invention is to overcome the above described problems.
Specifically, one object of the present invention is to provide a compact arrangement for cooling an EGR gas.
Another object of the present invention is to provide an EGR gas cooling system which is resistive to vibrations.
Still anther object of the present invention is to provide an EGR cooling arrangement which can also heat a lubrication oil when the lubrication oil temperature (or engine temperature) is low.
From another point of view, one object of the present invention is to provide an arrangement for cooling an EGR gas and lubrication oil, which is compact, does not vibrate and can heat the lubrication oil while cooling the EGR gas.
According to one aspect of the present invention, there is provided a system for cooling EGR gas and oil including a housing directly attached to a cylinder block such that engine cooling water flows in the housing, an EGR gas heat exchanger placed in the housing such that EGR gas flows in the EGR gas heat exchanger, and an oil heat exchanger placed in the housing adjacent to the EGR gas heat exchanger such that a lubrication oil flows in the oil heat exchanger. Since the two heat exchangers are located adjacent to each other and immersed in the cooling water in the housing, no piping is needed for introducing the cooling water into the housing. This improves resistance to vibration and reduces installation space. Further, since the two heat exchangers are closely located, heat of the high temperature EGR gas flowing in the EGR heat exchanger is transferred to the low temperature lubrication oil flowing in the oil heat exchanger via the cooling water when the engine is started under a cold condition. Thus, the lubrication oil is heated and its viscosity is lowered. This is particularly advantageous at the cold starting of the engine because the engine oil has high viscosity and the heated oil assists easier start up of the engine and reduces oil pump friction.
An opening may be formed in a lateral wall of the cylinder block such that part of a water jacket is exposed, and the housing (or a cover) covers the opening watertight such that the engine cooling water flows into the cover from the water jacket and vice versa. The EGR gas heat exchanger and oil heat exchanger are placed in the cover. Since the single opening is shared by the two heat exchangers, rigidity deterioration of the cylinder block due to making an opening is suppressed to the minimum. This also contributes to vibration reduction.
The oil heat exchanger may include a plurality of thin plate-like hollow members immersed in the engine cooling water in the housing, and the EGR gas heat exchanger may likewise include a plurality of thin plate-like hollow members immersed in the engine cooling water in the housing. The cooling system may include a first passage for introducing an exhaust gas to the EGR gas heat exchanger from an exhaust manifold and a second passage for introducing the exhaust gas to an intake manifold from the EGR gas heat exchanger. The housing may be shaped to guide air generated upon heating of the engine cooling water in the housing to a water jacket thereby allowing the air to escape to a cylinder head Therefore, the air ventilation pipe required in the conventional EGR cooler shown in
FIG. 8
is unnecessary for the cooling system of the invention.
Additional objects, benefits and advantages of the present invention will become apparent to those skilled in the art to which this invention relates from the subsequent description of the embodiments and the appended claims, taken in conjunction with the accompanying drawings.
REFERENCES:
patent: 07042628 (1995-02-01), None
patent: 10002256 (1998-01-01), None
patent: 10169514 (1998-06-01), None
Isuzu Motors Limited
Kamen Noah P.
McCormick Paulding & Huber LLP
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