Patent Application
20130306156
The invention relates to an apparatus having an exhaust-gas treatment device for the purification of exhaust gases of an internal combustion engine, having at least one injector which serves for the supply of a fluid into the exhaust-gas treatment device. A device of that type is provided, in particular, in a land-based motor vehicle. The invention also relates to a motor vehicle having the apparatus and a method for operating the vehicle.
Exhaust-gas treatment devices in which a fluid is added to the exhaust gas have become increasingly widely used in recent times. Such exhaust-gas treatment devices are, for example, exhaust-gas purification devices in which, inter alia, the selective catalytic reduction [SCR] method is carried out. In that method, a reducing agent is supplied to the exhaust gas, in such a way that nitrogen oxide compounds in the exhaust gas can be reduced in an effective manner. Ammonia is often used as a reducing agent. In motor vehicles in particular, ammonia is typically not stored directly but rather in the form of a reducing agent precursor, which is then converted into ammonia. The conversion (thermolysis and/or hydrolysis) often takes place in the exhaust gas. The reducing agent precursor may then be supplied directly to the exhaust gas. A commonly used reducing agent precursor is urea-water solution. A 32.5% urea-water solution which is used as a reducing agent is available, for example, under the trademark AdBlue®. When the reducing agent precursor is supplied to the exhaust gas, it is converted into ammonia due to the high temperature of the exhaust gas. The expressions “reducing agent” and “reducing agent precursor solution” will hereinafter be used synonymously for one another. For simplicity, reducing agent precursor solution will also be referred to as reducing agent.
At least one injector is typically used for the supply of the reducing agent into the exhaust-gas treatment device. The injector may, for example, be positioned on a section of the exhaust line, in particular upstream of a so-called hydrolysis catalytic converter and/or a so-called SCR catalytic converter. In a motor vehicle, the components are situated at least partially in the underbody region.
Exhaust-gas treatment devices are also known to which a hydrocarbon-containing fluid (such as, for example, fuel) is supplied through an injector. The addition of (unburned) hydrocarbons to exhaust-gas treatment devices is normally carried out in order to increase the temperature in the exhaust-gas treatment device. When the hydrocarbons impinge on an oxidation catalytic converter, the hydrocarbons burn with an exothermic reaction. By using such a temperature increase, it is possible in particular for the conversion of pollutants in the exhaust gas to be improved if appropriate, and/or for soot deposits to be eliminated.
A problem with the use of such injectors for the supply of a fluid into an exhaust-gas treatment device is typically the positioning of the injector directly on the exhaust-gas treatment device or at least close to the exhaust-gas treatment device. High temperatures, and a particularly intense temperature change between a cold rest state and the operating temperature, typically prevail there. This can lead to a) thermal overloading of the injectors, in such a way that the latter are damaged and can possibly no longer precisely dose the fluid, and b) a change in the fluid characteristics, thus influencing operational reliability.
It is accordingly an object of the invention to provide an apparatus having an exhaust gas treatment device with an injector for supplying a fluid, a motor vehicle having the apparatus and a method for operating the motor vehicle, which overcome the hereinafore-mentioned disadvantages and solve or alleviate the highlighted problems of the heretofore-known apparatuses, vehicles and methods of this general type. It is sought, in particular, to specify a device in which thermal overloading of the injector, and a change of the supplied fluid, is prevented in an effective manner.
With the foregoing and other objects in view there is provided, in accordance with the invention, an apparatus comprising an exhaust-gas treatment device for the purification of exhaust gases of an internal combustion engine, at least one injector for the supply of a fluid into the exhaust-gas treatment device, and at least one blower for delivering ambient air to the injector in order to cool the injector.
The exhaust-gas treatment device is preferably an exhaust-gas treatment device in which the method of selective catalytic reduction can be carried out. The fluid is then preferably a reducing agent for the SCR method. Furthermore, an SCR catalytic converter is generally provided in the exhaust-gas treatment device downstream of the injector in a flow direction of the exhaust gases. The SCR catalytic converter has a catalytic coating on which nitrogen oxide compounds in the exhaust gas can be converted together with the reducing agent. Furthermore, between the SCR catalytic converter and the injector, there may also be provided a hydrolysis catalytic converter through the use of which a conversion of the reducing agent or of the reducing agent precursor takes place. The reducing agent precursor, urea-water solution, is converted into ammonia in the exhaust gas either thermally and/or with assistance from a hydrolysis catalytic converter. In the SCR catalytic converter, the ammonia reacts with the nitrogen oxide compounds in the exhaust gas to form non-hazardous substances such as nitrogen, water and carbon dioxide.
The invention can, however, also be used for an exhaust-gas treatment device in which a fuel, such as for example gasoline or diesel, is supplied by an injector.
It is preferable for the at least one injector to be mounted on a section of an exhaust-gas conducting line. In this case, the line may conduct the entire exhaust-gas flow or else only a part thereof (bypass). The line generally has, for the injector, an opening and an injector seat on which the injector is disposed (in an exhaust-gas-tight manner) in such a way that, for example, its nozzle portion extends into or at least adjoins inner regions of the line. The injector is thus exposed to high temperatures as a result of contact with the hot exhaust line and/or thermal radiation and/or convection, in particular if the injector is positioned on the main exhaust-gas line (if appropriate also close to the internal combustion engine).
It is basically possible, in part, for such an injector to be cooled by relative wind. For this purpose, it is possible for guide plates to be provided on the vehicle, in particular in the region of the vehicle floor, in which the guide plates effect (passive) cooling during driving operation. It is now (also) proposed herein to provide controlled, active cooling when the vehicle is for example not moving, for instance during refueling, at traffic signals, after a shut-down, etc. For this purpose, the device includes at least one blower. It is basically possible for a plurality of (for example two) blowers to be provided per injector and/or for one blower to be assigned to multiple injectors. It is, however, preferable for exactly one blower to be assigned to (each) one injector. The blower may be provided in the direct vicinity (for example on the motor vehicle), so as to permit, for example, a direct supply of the ambient air, although it is also (alternatively or additionally) possible for a supply of an ambient air flow generated by the blower to take place indirectly through guide plates, guide tubes, etc.
The blower is accordingly preferably an active blower. In other words, this also means that the blower is activated and deactivated according to demand, independently of driving operation. For this purpose, the active blower has, if appropriate, a dedicated (electromotive) drive which is controlled by a controller. The blower may, for example, be a fan, a Roots blower or some other device for actively delivering ambient air. The blower preferably includes movable parts which serve for the delivery of the ambient air. If appropriate, the parts may, upon contact with the relative wind, be (passively) concomitantly moved in order to generate a supplementary (passive) ambient air flow to the injector. In order to ensure that the injector is cooled in a particularly effective manner by the ambient air delivered by the blower, the injector may have heat exchange surfaces which ensure an improved interaction of the ambient air with the injector for the purpose of temperature exchange.
In accordance with another particularly preferable feature of the apparatus of the invention, the at least one blower has a drive or drive device. The drive may, for example, be an electric drive, in particular an electric motor. It is, however, also possible for the drive to be a drive turbine which is driven by compressed air or exhaust gas, and/or for the drive to be formed by the internal combustion engine. If the drive is formed by the internal combustion engine, then the blower is preferably connected to the drive shaft of the internal combustion engine through a shaft or a gearing, a V-belt or some other motion and force transmission device.
In accordance with a further feature of the apparatus of the invention, at least one flow-guiding device is provided on the at least one injector. Ambient air can be conducted to the at least one injector by the at least one flow-guiding device. The flow-guiding device is preferably disposed at least partially between the blower and the injector, in such a way that the flow-guiding device diverts ambient air from the blower to the injector. The flow-guiding device may, for example, also be constructed as a flow diverting device. The flow-guiding device preferably includes at least one of the following components: at least one guide plate, at least one pipe section, at least one flow duct, at least one nozzle, at least one regulating flap. The flow-guiding device may also be disposed at least partially upstream of the blower as viewed in the flow direction of the ambient air. The flow-guiding device can thus ensure a particularly advantageous impingement of flow on the blower. The at least one flow-guiding device may also be disposed so as to deliver ambient air (in particular relative wind) to the injector when the blower is not being driven.
In accordance with an added feature of the apparatus of the invention, a controller is provided which is set up to activate and deactivate the at least one blower according to demand. The controller may also be integrated into a so-called engine controller of a motor vehicle. In this way, the controller can evaluate, in particular on the basis of (stored) characteristic maps, measurement data or the like, whether there is presently a risk of thermal overloading of the injector and/or particularly precise dosing of the fluid is necessary, and can then activate the blower and deactivate the blower again at predefined times. In particular, the controller can also deactivate the blower again if adequate cooling of the injector is ensured again even without the blower. A deactivation of the fan by the controller may take place, in particular, if a flow-guiding device which is impinged on, for example, by the relative wind of a motor vehicle is capable of ensuring adequate cooling of the injector. When adequate cooling of the injector is no longer being provided, the controller should be set up to identify such situations and reactivate the blower.
In accordance with an additional advantageous feature of the apparatus of the invention, a temperature sensor is provided on the exhaust-gas treatment device, through which the cooling or the temperature of the injector can be monitored. Such a temperature sensor is preferably disposed directly on the injector and/or a housing of the injector. It is self-evidently also possible for a temperature sensor of that type to be disposed so as to be in contact with the exhaust gas and/or with the exhaust-gas-conducting line, wherein then, the temperature of the injector can be inferred from those measurement results. Furthermore, a temperature sensor of that type is preferably connected to a controller which is set up to deactivate and activate the blower. In this case, it is also preferable for the controller to also take into consideration a present operating state of the internal combustion engine, such as for example the traveling speed.
With the objects of the invention in view, there is also provided a motor vehicle, comprising an internal combustion engine and an apparatus described above having an exhaust-gas treatment device. The motor vehicle is preferably a road-going passenger motor vehicle or utility motor vehicle or truck. The invention may also be used in mobile and static working machines.
In accordance with another particularly advantageous feature of the motor vehicle of the invention, the motor vehicle has a controller which is set up so as to deactivate the at least one blower when a speed of the motor vehicle exceeds a threshold speed, and to activate the at least one blower when a speed of the motor vehicle falls below the threshold speed. In particular, if the motor vehicle is traveling at an elevated speed, it may be the case that sufficient ambient air is already delivered to the injector by using a provided flow-guiding device and the relative wind of the motor vehicle, without active operation of the blower being necessary. In order to then realize a shut-down of the blower, a controller in the motor vehicle may be used. The controller may, for example, be connected (indirectly) to a tachometer in the motor vehicle in order to determine the traveling speed of the motor vehicle.
In accordance with a further preferable feature of the motor vehicle of the invention, at least one blower for cooling the at least one injector also serves for cooling the cooling water or coolant of the internal combustion engine. For example, the fan which is disposed on a cooling-water heat exchanger in the front region of a motor vehicle may be constructed to also generate a cooling flow to the injector.
With the objects of the invention in view, there is concomitantly provided a method for operating a motor vehicle having an apparatus including at least one injector, the method comprising the following steps:
In step a), the injector reference temperature may be a present (measured or calculated) value of the injector, of the exhaust gas and/or of the exhaust line. Step b) may likewise be measured and/or calculated on the basis of (stored) characteristic maps and/or sensors. Predefined driving states may, for example, be “high load,” “normal load,” “overrun operation” and “low load”. “High load” then relates, for example, to high engine speed/high torque at low vehicle speed, and “low load” relates, for example, to a rest state and/or idle operation. It is not necessary for the execution of the method, for both steps a) and b) to be repeated during every repetition. Different checking time intervals may be predefined in this case. It is likewise possible for the sequence to be reversed and/or for steps a) and b) to take place simultaneously.
A controller then evaluates, for example, the results from steps a) and b), and initiates active cooling of the injector if the (present and/or predicted future) thermal loading becomes too high. This may take place on the basis of a (stored) injector threshold temperature (condition i)) and/or on the basis of a “low load” or “high load” driving state in which, for example due to a lack of relative wind, there is a (future) threat of thermal overloading.
The method may be realized, in particular, with the apparatuses and motor vehicles according to the invention described herein. In this respect, all measures and explanations that have been explained and given in conjunction with the apparatuses and motor vehicles likewise apply in this case.
Other features which are considered as characteristic for the invention are set forth in the appended claims, noting that the features specified individually in the claims may be combined with one another in any desired technologically meaningful way and may be supplemented by explanatory facts from the description, with further structural variants of the invention being highlighted.
Although the invention is illustrated and described herein as embodied in an apparatus having an exhaust gas treatment device with an injector for supplying a fluid, a motor vehicle having the apparatus and a method for operating the motor vehicle, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawing.
The FIGURE of the drawing is a schematic and block diagram of a motor vehicle having an exemplary embodiment of an exhaust-gas treatment device with an injector and a blower.
Referring now in detail to the single FIGURE of the drawing, there is seen a motor vehicle 9 having an internal combustion engine 2 and an apparatus 17 with an exhaust-gas treatment device 1 for the purification of exhaust gases of the internal combustion engine 2. The exhaust-gas treatment device 1 has an injector 3 for the supply of a fluid and an SCR catalytic converter 10 for carrying out the method of selective catalytic reduction in the exhaust-gas treatment device 1. Fluid is supplied to the injector 3 from a tank 11 through a line 16. The fluid is preferably a reducing agent for the SCR method or a reducing agent precursor (urea-water solution). A blower 4, which is provided at the exhaust-gas treatment device 1, delivers ambient air to the injector 3. The ambient air is indicated by an arrow. Furthermore, a flow-guiding device 6, which may be provided at the exhaust-gas treatment device 1, diverts the ambient air to the injector 3. The blower 4 is preferably driven by a drive or drive device 5. The drive device 5 can be controlled by a controller 7. The controller 7 can also process data from a temperature sensor 8 which is configured to monitor the temperature of the injector 3 and thereby establish the extent to which cooling of the injector 3 is required. The controller 7 then regulates the blower 4 with the aid of the temperature sensor 8. Various decoupling devices 13, which may also be provided at the injector 3, prevent or reduce a transfer of heat from the exhaust-gas treatment device 1 to the injector 3. Shield plates 14, which reduce thermal radiation from the exhaust-gas treatment device 1 to the injector, are illustrated herein by way of example as such decoupling devices 13. Bores 15 in the injector 3 or in a housing of the injector 3, are also provided in this case by way of example as decoupling devices 13. The bores reduce the heat-conducting cross section of the injector 3 or of a housing of the injector 3. The heat conduction through the injector 3 or through a housing of the injector to the critical functional components of the injector, can thus be reduced. Such decoupling devices 13 can interact in an effective manner with the blower 4 and with the flow-guiding device 6 in order to cool the injector 3.
The blower 4 and the flow-guiding device 6 are preferably disposed in an underbody region 12 of the motor vehicle 9 and, in the case of working machines, in the engine hood. This applies, in particular, if the motor vehicle 9 is a passenger motor vehicle or a utility motor vehicle or truck. It can be ensured in this way that the flow-guiding device 6 is capable of diverting ambient air to the injector 3 even when the blower 4 is not being driven by the drive device 5.
| Number | Date | Country | Kind |
|---|---|---|---|
| 102011009620.5 | Jan 2011 | DE | national |
This is a continuation application, under 35 U.S.C. §120, of copending International Application No. PCT/EP2012/050825, filed Jan. 20, 2012, which designated the United States; this application also claims the priority, under 35 U.S.C. §119, of German Patent Application DE 10 2011 009 620.5, filed Jan. 28, 2011; the prior applications are herewith incorporated by reference in their entirety.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/EP2012/050825 | Jan 2012 | US |
| Child | 13952828 | US |
