Patent Description:
It is well known to provide a vehicle exhaust gas treatment system in which a urea solution is injected into a catalytic converter located in the exhaust system of an internal combustion engine, to significantly reduce the level of exhaust pollutants such as carbon monoxide, nitrogen oxide and particulate matter in the exhaust gases.

Problems arise with such treatment systems since if the temperature of the urea exceeds <NUM> degrees centigrade, due to exposure to the sun or the close proximity of hot components on the vehicle, the urea starts to break down into corrosive constituents which can damage the components of the treatment system. Therefore, the urea itself and/or components (delivering the urea), such as urea dosing module, are often provided with cooling means.

Cooling is typically carried out by directing engine coolant, e.g. water glycol mixture, via the dosing module, the coolant being circulated by the engine coolant pump. The cooling of the dosing module is especially important as this component is in contact with the hot exhaust gas and faces high heat impact. Such a system is disclosed in <CIT>.

A problem arises immediately after when the engine is shut down, especially when operating in a hot environment and/or after a long duration of operation. The engine water pump, driven by the engine, ceases to propel engine coolant through the dosing module.

<CIT> and <CIT> both suggest to provide an additional electrically driven auxiliary fluid pump which serves to force the cooling fluid around the fluid circuit to the dosing module, wherein the auxiliary pump is activated automatically when the engine is shut down. This solution requires additional components, connecting lines and a dedicated control system which increases costs and installation space.

It is an object of the present invention to provide an improved form of cooling system for the urea solution and especially components in the above exhaust treatment systems.

Accordingly, there is provided a vehicle as defined in claim <NUM>.

Advantageously, evaporation bubbles can be effectively routed and coolant supplied such that the urea dosing module is effectively cooled. Further advantageously, the bypass line allows pressures to be balanced between the feed and return lines of the cooling system.

References to "substantially vertical" herein will be understood to include exactly vertical, and to be in the range <NUM> - <NUM> degrees angle to the horizontal.

Preferably, at least one of the second portion and secondary portion may have a cross-sectional area greater than the cross sectional area of the first portion and the primary portion.

Advantageously, the increased cross sectional area allows for an increased volume of coolant to be held.

Preferably, with the axis C in a substantially vertical orientation, the first port and the second port may be at the same level relative to the ground. Alternatively, with the axis C in a substantially vertical orientation, one of the first port and the second port may be positioned at a higher level relative to the ground than the other of the first port and the second port.

Advantageously, positioning the ports at appropriate relative heights allows evaporation bubbles to collect in predetermined positions at various inclinations of the cooling system and exhaust package.

Preferably, the second portion and secondary portion may function as coolant reservoirs.

Advantageously, this allows for a greater amount of coolant and thus thermal mass to be provided and thereby increases the cooling capacity of the system.

The catalytic converter may be parallel to the axis C. Alternatively, the catalytic converter may be inclined relative to the axis C, or be perpendicular to it.

Advantageously, the effective cooling of the urea supply module allows a tractor to operate more cleanly and reduce emissions.

The drawings are provided by way of reference only, and will be acknowledged as not to scale.

With reference to <FIG>, an engine exhaust gas treatment system <NUM> is shown. The engine exhaust gas treatment system <NUM> has a urea solution supply tank <NUM> which supplies urea to a urea supply module <NUM>. The urea supply module <NUM> next supplies a urea dosing module <NUM> via the urea feed lines 14a, 14b and urea return lines 15a, 15b (indicated by arrows F - feed and R - return respectively). An alternative construction of the exhaust gas treatment system <NUM> including an exhaust silencer <NUM> is shown in dotted lines and can be better seen in <FIG>.

In some embodiments and configurations, the urea return line 15b may not be required.

Dosing module <NUM> injects the urea into a Selective Catalytic Reduction (SCR) catalytic converter <NUM> which is longitudinally aligned along the axis C - which is substantially vertical, in the general direction of the exhaust gas stream indicated by arrow G out of an exhaust pipe 21a. The SCR and exhaust pipe 21a are aligned to have the gas flow passing there through substantially aligned with an axis C, the axis C being substantially perpendicular to the ground.

The vehicle is also provided with an engine cooling system <NUM> comprising a heat exchanger <NUM>, a fan <NUM> and an engine coolant pump <NUM> to supply cooling fluid, further referred to as coolant, to various components of the tractor.

The engine cooling system <NUM> may comprise further components such as sensors, valves etc. to control and the engine cooling system <NUM>.

The coolant is provided to the urea dosing module <NUM> via a coolant feed line branch <NUM> (in a direction indicated by respective arrow 40a) which is connected to coolant feed port 13a of dosing module <NUM>.

The coolant is returned to heat exchanger <NUM> via a coolant return line branch <NUM> (in a direction indicated by respective arrow 50a) which is connected to coolant return port 13b of dosing module <NUM>.

In normal operation, the engine coolant pump <NUM> is constantly circulating the coolant through coolant line branches <NUM>, <NUM> so that the dosing module <NUM> is protected from overheating.

Upon shut down of the engine, the circulation of coolant stops and remaining coolant in the dosing module <NUM> may start to heat up excessively and may be consequently damaged.

With reference to <FIG>, the coolant feed line branch <NUM>, seen in coolant flow direction indicated with arrow 40a, is provided with a first feed pipe section <NUM> extending vertically upwards above the horizontal level H of the ports 13a and 13b of the dosing module <NUM>.

A second feed pipe section <NUM>, is u-shaped or syphon shaped with the ends directed downwards, i.e. towards the ports 13a, and 13b of the dosing module <NUM>.

One end of the second feed pipe section <NUM> is connected to and follows on from the first feed pipe section <NUM> and the second end and is connected to a vertical third feed pipe section <NUM> which ends at port 13a.

The vertical first feed pipe section <NUM> and the vertical third feed pipe section <NUM> form a first portion and a second portion respectively of the coolant feed line <NUM>.

The coolant return line branch <NUM> contains coolant that flows in the opposite direction to that of the coolant in the coolant feed line branch <NUM>, and flows in a direction indicated by arrow 50a. The coolant return line branch <NUM> is provided with a first return pipe section <NUM> extending vertically upwards above the horizontal level H of the ports 13a, and 13b of the dosing module <NUM>.

A second return pipe section <NUM>, is u-shaped or syphon shaped with the ends directed downwards, i.e. towards the ports 13a, and 13b of the dosing module <NUM>.

One end of the second return pipe section <NUM> is connected to and follows on from the first return pipe section <NUM> and the second end and is connected to a vertical third return pipe section <NUM> which ends at port 13b.

The vertical first return pipe section <NUM> and the vertical third return pipe section <NUM> form a primary portion and a secondary portion respectively of the coolant return line <NUM>.

During normal operation, coolant coming from engine coolant pump <NUM> passes first feed pipe section <NUM> upwards and is directed downwards by u-shaped second feed pipe section <NUM> into a vertical third feed pipe section <NUM> to enter the dosing module <NUM> via at port 13a.

The coolant then exits the dosing module <NUM> via port 13b and flows upwards in third return pipe section <NUM> to be directed downwards by u-shaped second return pipe section <NUM> and then passes through first return pipe section <NUM>.

Upon shut down of the engine, with the engine coolant pump <NUM> not operating, the coolant in third feed pipe section <NUM> and third return pipe section <NUM> is trapped due to syphon action in the design.

Remaining coolant in the dosing module <NUM> is further heated up and starts to evaporate.

The evaporation of the coolant in the pipes causes evaporation bubbles to ascend in either third feed pipe section <NUM> or third return pipe section <NUM>, depending on the inclination of the vehicle.

If the vehicle stands inclined in a direction indicated with Arrow A such that axis A' is substantially vertical, port 13a of dosing module <NUM> is at a higher level compared to port 13b.

Because of this, evaporation bubbles will ascend into third feed pipe section <NUM> and displace the remaining coolant into first feed pipe section <NUM> whilst in the third return pipe section <NUM>, no evaporation bubbles occur.

If the vehicle stands inclined in the opposite direction indicated with Arrow B such that axis B' is substantially vertical, port 13b of dosing module <NUM> is at a higher level compared to port 13a.

Because of this evaporation bubbles will ascend into third return pipe section <NUM> and displace the remaining coolant into first return pipe section <NUM> while in the third feed pipe section <NUM>, no evaporation bubbles occur.

In an example embodiment, the third feed pipe section <NUM> and or the third return pipe section <NUM> extends in a substantially vertical direction from said ports (13a, 13b) and forms a reservoir in which coolant is trapped after engine shut down.

As evaporation bubbles reduce the density of the fluid in the respective pipe sections, the trapped fluid in the other section flows into the dosing module <NUM> to provide extra coolant for keeping the acceptable temperature level.

As only a small inclination of the vehicle is enough to cause the evaporation through one of ports 13a and 13b, only one of third feed pipe section <NUM> or third return pipe section <NUM> may face evaporation bubbles while the other third feed pipe section <NUM> or third return pipe section <NUM> can provide extra coolant.

Even if both ports 13a and 13b are at an exact horizontal level, the evaporation bubbles will ascend in only one of third feed pipe section <NUM> or third return pipe section <NUM>.

In some installations, it is enough to provide the third feed pipe section <NUM> or third return pipe section <NUM> with the same inner diameter then the other sections of the feed line branch <NUM> or return line branch <NUM> to form a reservoir which sufficient to provide extra coolant.

In further embodiments, the third feed pipe section <NUM> or third return pipe section <NUM> may have an diameter expansion <NUM>, <NUM> (e.g. in form of a rubber hose inserted on a pipe on both ends, see <FIG>, <FIG> and <FIG>). Thereby the volume of coolant trapped can be increased or expanded as required.

With reference to <FIG>, an example is shown wherein the dosing module <NUM> is provided with ports 13a and 13b not aligned horizontally. As port 13b is on higher level H1 while port 13a is on lower level H2, the port 13b would always be above port 13a at every possible/allowable inclination of the vehicle.

This ensures that evaporation always takes place through port 13b. As a consequence, only third feed pipe section <NUM> and expansion <NUM> is necessary to provide extra coolant for the case of engine shut-off.

In an example according to the invention, a bypass line <NUM> is provided between third feed pipe section <NUM> and third return pipe section <NUM>.

In some circumstance, the evaporation of coolant may result in an excessive high pressure trapped in pipe section <NUM>, <NUM>. This high pressure would prevent coolant from the other pipe section to flow into the dosing module. The bypass line <NUM> serves to balance the pressure in pipe section <NUM> and <NUM> so that coolant can freely flow.

<FIG> and <FIG> show the components of the cooling system installed on a tractor (not shown).

The first feed pipe section <NUM> and second feed pipe section <NUM> are integrated in one steel pipe <NUM>. Similarly, first return pipe section <NUM> and second return pipe section <NUM> are integrated in one steel pipe <NUM>.

The third feed pipe section <NUM> and the third return pipe section <NUM> are constructed from rubber hoses having a relative large diameter compared to the other pipe section to which they are attached and thus form diameter expansion <NUM>, <NUM>.

In <FIG>, the third feed pipe section <NUM> and third return pipe section <NUM> are shown in dotted lines to show the compact installation by placing the lines in close vicinity and one behind the other to reduce necessary installation space.

<FIG> shows a Selective Catalytic Reduction (SCR) catalytic converter <NUM> and dosing module <NUM> both installed in a vertical direction along axis C and suitable for installation at the right A-pillar of a cab of a tractor (not shown) similar to the installation described in <CIT>. The components of the feed line branch <NUM> and coolant return line branch <NUM> are supported by a sheet metal support <NUM> which is suitable for attachment to the A-pillar of an associated tractor.

As shown with <FIG>, representing a sectional view of <FIG> at a plane X perpendicular to axis C, the sheet metal support <NUM> is situated in-between the Selective Catalytic Reduction (SCR) catalytic converter <NUM> and the third feed pipe section <NUM> along with diameter expansion <NUM>, and third return pipe section <NUM>, along with diameter expansion <NUM> and thereby provides a thermal or heat shield.

Because of this arrangement, the coolant trapped in third feed pipe section <NUM>, along with diameter expansion <NUM>, and third return pipe section <NUM>, along with diameter expansion <NUM> is kept at a relatively lower temperature, than if there were no heat shield, to provide more cooling capacity for the dosing module <NUM>.

Additionally, this enables third feed pipe section <NUM>, along with diameter expansion <NUM>, and third return pipe section <NUM>, along with diameter expansion <NUM>, to be made of rubber (hoses) or other material with low thermal resistance as they are protected by the thermal shielding.

The first feed pipe section <NUM> and first return pipe section <NUM> are positioned in between sheet metal support <NUM> and catalytic converter <NUM> as the heat impact is of minor relevance since steel pipes are used.

With reference to <FIG>, Selective Catalytic Reduction (SCR) catalytic converter <NUM>, dosing module <NUM> and major parts of the components are hidden by covers <NUM>, <NUM> to prohibit an operator from contacting the hot parts.

In an alternative embodiment as best seen in <FIG> an exhaust gas treatment <NUM>' is shown.

Dosing module <NUM> injects the urea into a Selective Catalytic Reduction (SCR) catalytic converter <NUM>' which is perpendicular aligned with respect to the axis C' and axis C - which are substantially vertical. The exhaust pipe 21a' and an exhaust silencer <NUM> are aligned with the axis C' and in the general direction of the exhaust gas stream indicated by arrow G' out of an exhaust pipe 21a'. The SCR <NUM>' longitudinally aligned with axis N. The axis N is arranged at an angle to the exhaust pipe 21a' and the exhaust silencer <NUM> which are aligned to have the gas flow passing there through substantially aligned with an axis C', the axis C' being substantially perpendicular to the ground. An exhaust connecting pipe 21c fluidly connects the SCR21' with the silencer <NUM>. The rest of the exhaust gas treatment system <NUM>' functions similarly to the exhaust gas treatment system <NUM>.

Importantly, in the embodiment of <FIG>, the SCR <NUM>' is inclined relative to the coolant pipes <NUM>, <NUM>, <NUM> and <NUM> which are positioned vertically relative to the ground as in the previous embodiment. For this embodiment it is only the orientation of the SCR2 <NUM>' which is changed relative to the rest of the cooling system <NUM>.

In yet a further embodiment, as is best seen in <FIG>, feed pipe section <NUM>'extends horizontally before extending vertically to meet with diameter expansion <NUM>.

Furthermore return pipe section <NUM>' extends vertically downwards/depends from the port 13b and sub section <NUM>" before extending vertically to meet with diameter expansion <NUM>. This arrangement may be used on either the Feed or Return ports 13a and 13b. As such, in alternative embodiments pipes connected to the ports 13a and 13b may depend from the ports before turning to extend vertically relative to the ground and substantially parallel to the axis C.

As such it will be appreciated that the portion of tube and /or pipe that exits either of port 13a and or 13b may extend in any direction relative to the ports 13a and/or 13b, before turning to extend substantially vertically relative to the ground. The pipe routings from the ports 13a and 13b may be symmetrical or different depending on the requirements of the construction.

It will be understood that the second feed and return pipe section <NUM>, <NUM> are in fluid communication with the third feed and return pipe section <NUM>, <NUM> either directly or via the diameter expansions <NUM>, <NUM>. Indeed in some embodiments the second feed and return pipe section <NUM>, <NUM> may be in direct communication with the ports 13a, and 13b respectively. The diameter expansions <NUM>, <NUM> may simply be formed as localised expansions of a continuous pipe.

Furthermore, in alternative embodiments the bypass line <NUM> may be positioned elsewhere so that the feed and return lines are in fluid communication. This could be between the second feed and return pipe sections <NUM>, <NUM> of for example the third feed and return pipe sections <NUM>, <NUM> or indeed between the diameter expansions <NUM>, <NUM>.

Claim 1:
A vehicle comprising:
an internal combustion engine;
an exhaust system for the internal combustion engine which comprises an exhaust pipe (21a, 21a') and a catalytic converter (<NUM>, <NUM>'), the catalytic converter being orientated relative to an axis C, axis C being substantially vertical to ground;
an exhaust gas treatment system including a urea dosing module (<NUM>) for injecting urea into the catalytic converter (<NUM>, <NUM>'), the urea dosing module having a first port (13a) and a second port (13b);
an engine cooling system (<NUM>), wherein the engine cooling system comprises a heat exchanger (<NUM>), a fan (<NUM>), and a coolant pump (<NUM>);
a cooling system (<NUM>) for the exhaust gas treatment system, the exhaust gas treatment system cooling system having a coolant feed line (<NUM>) and a coolant return line (<NUM>), each fluidly connected at one end with the engine cooling system (<NUM>) and at the other end with a respective one of the first and second ports (13a, 13b) of the urea dosing module;
characterised in that the coolant feed line (<NUM>) comprises a first portion (<NUM>) and a second portion (<NUM>), and the coolant return line (<NUM>) comprises a primary portion (<NUM>) and a secondary portion (<NUM>) and wherein each of the first portion, the second portion, the primary portion and the secondary portion are oriented longitudinally parallel to the axis C and extend upwardly above the first port (13a) and the second port (13b), and, wherein the second portion (<NUM>) is in fluid communication with the first port (13a), and the secondary portion (<NUM>) is in fluid communication with the second port (13b); and
a bypass line (<NUM>), the bypass line being in fluid communication with each of the second portion (<NUM>) and the secondary portion (<NUM>).