Patent Description:
The present invention relates to the thermal management of an after treatment system of an internal combustion engine.

An after treatment system (ATS) is connected on the exhaust line of the diesel internal combustion engine, which comprises a certain number of devices to reduce/eliminate pollutants contained in the exhaust gas, such as NOx, HC, particulate matter.

The most implemented configuration for diesel engines has, according to the gas flow direction, a DOC (Diesel oxidation catalyst), a DPF (Diesel particulate filter) and active SCR (selective reduction catalyst). This configuration is called "traditional ATS" in the following. The SCR contributes to the elimination/abatement of NOx, however, it needs to reach at least the so-called "light off" temperature of about <NUM> - <NUM>.

At cold start, the SCR is practically unable to convert NOx. The DOC is usually arranged upstream of the SCR to produce NO2 needed for the SCR working in the NOx conversion.

DOC and DPF have a relevant mass that drains a relevant heat amount during ATS warm up, therefore, the SCR warm up takes a relevant time, especially during cold winter nights.

Technical regulations require the ATS be effective also at cold start, therefore, several possible solutions have been considered to fulfil such restrictive requirements.

<CIT> discloses an engine having an exhaust gas cleaner/catalytic converter and a storage volume for part of the exhaust flow after starting the engine. The vacuum in the storage volume is maintained by a shut-off valve when the engine is stopped. An under pressure pump to evacuate the storage volume is connected to it with its intake side. The feed side of the pump is connected to intake unit of the engine, and/or to the exhaust pipe upstream of the exhaust gas cleaner/main catalytic converter.

<CIT> discloses an exhaust line having two heat exchangers and a catalyst between such heat exchangers. A heat transfer medium flows along a circuit, through the two heat exchangers and through a tank. An ECU controls the flow of the heat transfer medium according to an exhaust gas temperature.

<CIT> and <CIT> disclose solutions provided with an exhaust system section surrounded by a jacket, where vacuum can be generated.

<CIT> discloses an exhaust system section provided with a heat exchanger receiving an engine cooling liquid. The engine cooling liquid flows also in another heat exchanger for conditioning a vehicle passenger compartment.

Therefore, the main object of the present invention is to provide for improving the thermal management of an after treatment system (ATS) of an internal combustion engine.

The basic idea of the present invention is to implement a jacket enveloping at least a portion of the ATS and to introduce a thermal liquid in said jacket, so as to exchange heat between the thermal liquid and said at least a portion of the ATS when the engine is operative, and to store said thermal liquid in a well-insulated tank when the engine is shut-off in order to store its heat content. This is described in independent claim <NUM>.

According to a preferred embodiment of the invention, a switch or button can be manipulated or pressed to activate or enable a thermal management function, which causes the introduction of the thermal liquid into the tank.

According to a preferred embodiment, the thermal management function activation commands a vacuum pump arranged to produce vacuum within the jacket for a better insulation.

When the engine is started at low temperatures, the vacuum is released after the ATS temperature is raised above a first temperature threshold. This in order to avoid deformation of the wall and/or ATS canning.

According to a preferred embodiment of the invention, the thermal management function activation commands a pump arranged to move the warm thermal liquid from the ATS jacket to the well-insulated tank.

According to an embodiment, when the engine is started at low temperatures, the pump is arranged to move back the stored warm thermal liquid from the well-insulated tank to the ATS jacket, so as to help the ATS to increase its temperature.

In particular, the thermal management function activation causes, first, the thermal liquid motion from the ATS jacket to the well-insulated tank, afterwards the vacuum pump activation to generate vacuum within the jacket. After the engine re-start, the vacuum itself can be useful to suck the thermal liquid from the well-insulated tank into the jacket.

If the temperature of the stored thermal liquid, at the re-start of the engine, is not useful to increase the ATS temperature, such liquid is gradually moved into the jacket only when the ATS temperature is over the above-mentioned light-off temperature threshold.

According to another embodiment of the invention, the jacket is exploited also to adjust the ATS temperature, in particular to maintain the temperature of the ATS close to such light-off threshold. Indeed, in such conditions, the dosing module arranged immediately upstream of the SCR (Selective catalytic reduction) is capable to evaporate the liquid urea based reducing agent, and, at the same time, the ammonia storage efficiency of the SCR is optimal.

At the same time, the excess of thermal energy is stored in the thermal liquid itself. Therefore, when the engine is switched off for a long period, before vacuum generation in the ATS jacket, such thermal liquid is moved into the above well-insulated tank.

When the thermal liquid coincides with the engine water, such water can be first circulated through the combustion engine at cold start and, after ATS light-off, circulated also through the ATS jacket.

According to a further object of the invention, also the engine oil is stored in a well-insulated tank, such that to save its heat content during long period shut off.

These and further objects are achieved by means of the attached dependent claims, which describe preferred embodiments of the invention, forming an integral part of the present description.

The invention will become fully clear from the following detailed description, given by way of a mere exemplifying and non limiting examples, to be read with reference to the attached drawing figures, wherein:.

The same reference numerals and letters in the figures designate the same or functionally equivalent parts.

According to the present invention, the term "second element" does not imply the presence of a "first element", first, second, etc.. are used only as labels for improving the clarity of the description and they should not be interpreted in a limiting way.

In some example embodiments, well-known processes, well-known device structures, and well known technologies are not described in detail.

According to the figures, a combustion engine <NUM>, such as a gasoline or diesel engine is provided with an intake <NUM> and one or more exhaust manifolds <NUM>.

The intake is connected operatively with an inlet line <NUM> provided with a filter box <NUM> suitable to filter the fresh air sucked by the internal combustion engine.

In the example, the engine implements two exhaust manifolds, however, one single manifold can be implemented to convey the exhaust gas produced by all the several cylinders defining the internal combustion engine <NUM>.

The after treatment system ATS includes for example a first pollutants abatement device <NUM>, a second <NUM> and a third abatement device <NUM>.

At least a portion of the ATS, for example at least one of the pollutants abatement devices, is wrapped within a jacket <NUM>. Preferably, the entire ATS is wrapped by the jacket. When the internal combustion engine is turbocharged, the jacket can wrap also the turbine. Thus, the turbine is intended, by a gas path and thermal point of view, as a portion of the ATS.

In the examples, two initial pipe portions <NUM> are directly connected to the internal combustion engine. Two first abatement devices <NUM> are present in parallel on the initial pipe portions <NUM>. In the example, just one of the two first abatement devices <NUM> is wrapped within the jacked <NUM>. This means that the devices that deserve to be wrapped can be selected according to the circumstances. The ATS comprises, for each first abatement devices <NUM>, a respective pipe portion <NUM>. The two pipe portions <NUM> convey into one single remaining pipe portion.

The jacket <NUM> is operatively connected to a vacuum pump <NUM> through a first piping <NUM> at the port <NUM> of the jacket.

The jacket is sealed and capable to maintain the vacuum generated by the vacuum pump.

An on/off valve <NUM> is arranged on the piping <NUM>, upstream or downstream of the vacuum pump.

A button (not disclosed) is arranged on the dashboard. When the driver supposes to leave the vehicle shut-off for a long period, after he has shut-off the engine, he/she can push such button to activate the thermal management function according to the present invention.

The vacuum pump can be activated immediately after the button pressing or only when the ATS temperature is under a predetermined temperature threshold, because, at high temperature some portions of the metal sheets defining the ATS canning of the abatement devices can be damaged by the vacuum.

The expression "long period" should be understood according to the circumstances. For example, in extreme environment conditions, such as during winter with temperatures lower than <NUM>-<NUM> under <NUM>, three hours can be considered as a "long period".

According to the option of <FIG>, after the vacuum pump <NUM> has reached a predetermined vacuum pressure within the jacket, the valve <NUM> is operated into close operation to seal the piping <NUM> and then the vacuum pump is stopped. In this way, a possible leakage through the vacuum pump is prevented.

After the internal combustion engine is re-started, with the thermal management function active, the valve <NUM> is operated into open position to release the vacuum within the jacket, only after the ATS temperature has reached a predetermined temperature threshold, so as to prevent the above-mentioned damaging of the metal sheets.

Therefore, the vacuum is released only if really needed and can depend on the structural characteristics of the canning of the abatement devices defining the ATS.

According to a second option, under the teachings of the invention, disclosed through <FIG>, the ATS, similarly as in <FIG>, is provided of a jacket <NUM> enveloping at least a portion of the ATS.

The lower portion of the jacket <NUM>, in operating condition, is connected to a lower portion of a well-insulated tank <NUM>, at least through one piping <NUM> on which a liquid pump <NUM> is arranged.

A tank thermal insulation can be realized according to any known method.

The liquid pump <NUM> is suitable to move a thermal liquid from the jacket <NUM> to the well-insulated tank <NUM>.

According to one embodiment of the present option, air replaces, into the jacket <NUM>, the thermal liquid that is moved by the pump <NUM> into the tank <NUM>. In particular, as shown in <FIG>, such air flows into the jacket <NUM> through the control of a valve <NUM>, e.g. defined by an on-off valve.

According to the relative position of the tank <NUM> and the jacket <NUM>, the thermal liquid can move from the tank <NUM> into the jacket <NUM> by gravity, or it can be pumped by reversing the liquid pump <NUM>.

In this situation (refilling of the space in the jacket <NUM> by menas of the liquid from the tank <NUM>), the air within the jacket <NUM> should be vented (e.g. discharged towards the outer environment or towards the tank <NUM>), while a corresponding amount of air should replace, within the tank <NUM>, the thermal liquid volume. Indeed, it is preferable that the tank <NUM> is closed. In any case, suitable venting valves, as valve <NUM> described below, can be implemented to manage air sucking/venting.

According to the example of <FIG>, the second (second does imply the presence of a first) piping <NUM> is connected to a lower portion of the tank <NUM>, such that the thermal liquid can fall naturally (i.e. by gravity) within the jacket <NUM>, while the air contained therein is being vented. Preferably, as mentioned above, a first piping <NUM> connects an operatively upper portion of the jacket <NUM> with an upper portion or zone of the tank <NUM> and a first on/off valve <NUM> is arranged thereon.

Once the valve <NUM> is closed, the thermal liquid cannot enter into the jacket <NUM>, because the gas herewith contained cannot reach the upper portion of the tank <NUM>. According to this embodiment, between the tank <NUM> and the jacket <NUM>, a closed circuit is realized. Therefore, instead of using air, a specific gas can be used as insulation, such as argon or the like.

Therefore, during cold nights, the driver can activate a thermal management function, in such a manner that a thermal insulation gas (e.g. air) moves within the jacket <NUM> (valve <NUM> is opened), while warm thermal liquid is pumped into the tank <NUM>; when the warm thermal liquid is replaced with gas in the jacket <NUM>, valve <NUM> is closed and pump <NUM> is stopped. On the other hand, during engine operation, the thermal liquid is moved within the jacket <NUM>.

<FIG> discloses one of several possible combinations of the two main options described through <FIG>. Here, with respect to <FIG>, a vacuum pump <NUM> is arranged on the first piping <NUM> and second on/off valve <NUM> is arranged on the second piping <NUM>.

When the driver activates the thermal management function, first and second on/off valves <NUM>, <NUM> are opened, then thermal liquid is pumped through the liquid pump <NUM> from the jacket <NUM> to the tank <NUM>. When all the liquid is replaced with gas in the jacket <NUM>, second on/off valve <NUM> closes and liquid pump <NUM> stops. Then, vacuum pump <NUM> is activated; afterwards, first on/off valve <NUM> is closed and vacuum pump <NUM> stops.

When the engine is re-started, or after a certain period, if the thermal liquid has a temperature above a predetermined threshold, the on/off valve <NUM> opens so as to immediately refill the jacket <NUM>. Otherwise, the thermal liquid is introduced into the jacket <NUM> gradually, after the ATS has reached the above light-off temperature, in order to maintain the ATS close to said light-off temperature.

It is clear to the skilled person in the art, that metering valves can be implemented instead of the cheaper on/off valves.

A suitable control unit can be implemented to control the vacuum pump <NUM> and/or the liquid pump <NUM> and the needed valves <NUM>, <NUM>, <NUM>, as a response of the pushing/manipulation of the switch or button. The control unit is arranged to monitor the operating conditions of the engine, ATS temperature, thermal liquid temperature, and so on, such that the thermal management function is activated only after the engine is switched off and suitably deactivated before or after engine re-start.

Indeed, when the stored thermal liquid has a heat content that can be suitably exploited, the thermal liquid is introduced within the jacket <NUM> at engine re-start or even before such re-start (i.e. in response to an event, e.g. the opening of a vehicle door, indicating to the control unit that the engine is about to be re-started). On the other hand, if the heat content is not relevant, the thermal liquid is introduced within the jacket <NUM> only after the ATS has reached the light-off temperature threshold.

Preferably, the heat content is indirectly measured through the measurement of the stored thermal liquid temperature.

In addition, the heat content is judged as "useful" if the stored thermal liquid temperature is higher than the ATS temperature. It is clear that the efficiency of the heat exchange between the thermal liquid and the ATS should be considered during such judgment.

When vacuum is realized within the jacket <NUM>, such vacuum is maintained as long as the canning can bears such depressurization during temperature increase, and in any case till the introduction of the thermal liquid into the jacket <NUM>.

To introduce the thermal liquid within the jacket <NUM>, second on/off valve <NUM> opens and, vacuum can be initially exploited to suck liquid from the tank <NUM>. Then first on/off valve <NUM> opens and the thermal liquid can pass within the jacket <NUM> by gravity and/or by suction and/or by the reverse activation of the liquid pump <NUM>.

<FIG> discloses another possible embodiment of the invention.

Here, the first piping <NUM> has a first end opening in the jacket <NUM>, wrapping at least a portion of the ATS, and a second end, opposite to the first one, communicating with the environment. On the first piping <NUM>, a vacuum pump <NUM> and a first on/off valve <NUM> is arranged to generate and maintain the vacuum when the thermal management function is active.

Here, the second piping <NUM> communicates, at one end, with a lower portion of the jacket <NUM> and, at a second opposite end, with a lower portion of the tank <NUM>.

On the second piping <NUM>, the liquid pump <NUM> and the second on/off valve <NUM> are arranged.

An upper portion of the tank <NUM> communicates with the environment through a venting valve <NUM>.

When the driver pushes the button to activate or enable the thermal management function, first the liquid is moved from the jacket <NUM> to the tank <NUM>. Thus, both the on/off valves <NUM> and <NUM> are open, and the liquid pump <NUM> causes the movement of the thermal liquid.

When the thermal liquid is completely moved to the tank <NUM>, second valve <NUM> closes and liquid pumps <NUM> stops. Then, vacuum pump <NUM> is activated till a predetermined vacuum pressure. Then, first on/off valve <NUM> closes and vacuum pump <NUM> stops.

The venting valve <NUM> permits to vent the air from the tank <NUM>. On the other hand, when the thermal liquid is pumped within the jacket <NUM>, the venting valve <NUM> permits air to replace the volume of thermal liquid moved to the jacket <NUM>. The venting valve <NUM> can be a spring loaded valve or can be an electric-controllable valve. In this second case, the motion by gravity of the thermal liquid from the tank <NUM> to the jacket <NUM> is simplified.

On the other hand, when the engine is re-started, the same steps disclosed for the example of <FIG> are carried out.

According to a preferred embodiment of the invention, the thermal liquid coincides with engine water, or engine cooling liquid, and the jacket <NUM> is connectable with the engine cooling circuit, such that when the driver opens the vehicle, the engine water is moved, though a dedicated circuit, from the tank <NUM> within the engine cooling circuit. Then, the thermal management of the ATS is carried out as described above.

Engine re-start is inhibited as long as the moving of the engine liquid from the tank <NUM> to the engine cooling circuit is not complete.

Many changes, modifications, variations and other uses and applications of the subject invention will become apparent to those skilled in the art after considering the specification and the accompanying drawings which disclose preferred embodiments thereof as described in the appended claims.

The features disclosed in the prior art background are introduced only in order to better understand the invention and not as a declaration about the existence of known prior art. In addition, said features define the context of the present invention, thus such features shall be considered in common with the detailed description.

Claim 1:
An After Treatment System (ATS) with a thermal management system, the ATS comprising a number of pollutants abatement devices and being conceived to convey and purify exhaust gas produced by an internal combustion engine (<NUM>), the thermal management system comprising:
- a jacket (<NUM>) wrapping at least a portion of said ATS,
- an insulated tank (<NUM>) suitable to store a thermal liquid,
- moving means for moving said thermal liquid between said jacket (<NUM>) and said insulated tank (<NUM>), said moving means comprising a piping connecting a lower portion of said jacket (<NUM>) with a lower portion of said insulated tank (<NUM>), and a liquid pump (<NUM>) suitable to move said thermal liquid from said jacket (<NUM>) to said insulated tank (<NUM>), characterized in that the thermal management system comprises
- control means configured to control said moving means
• to introduce said thermal liquid in said jacket (<NUM>), so as to exchange heat between the thermal liquid and said at least a portion of the ATS when the engine is operative, and
• to move the thermal liquid from said jacket (<NUM>) to said insulated tank (<NUM>) by said liquid pump (<NUM>) and store said thermal liquid in said insulated tank (<NUM>) when the engine is shut-off in order to store its heat content.