FR2927360A1 - Exhaust gas treating method for diesel engine of motor vehicle, involves heating metallic converter by using energy obtained during deceleration of vehicle, where energy produced during deceleration is converted into electrical energy - Google Patents

Abstract

The method involves heating a metallic catalytic converter (16) by using energy obtained during deceleration of a vehicle (10). A heated part of the converter corresponds to an upstream portion of the converter in a flow direction of exhaust gases. The energy produced during deceleration of the vehicle is converted into electrical energy for heating the converter using an electric machine, where the machine includes units for authorizing and defining a recovery braking operating mode of the machine. An independent claim is also included for a device for treating exhaust gas in a vehicle.

Description

The present invention relates to a method and an apparatus for treating exhaust gas. The combustion of fossil fuel such as oil or coal in a combustion system can lead to the production of significant amounts of pollutants that can be released into the atmosphere and degrade the environment. This is particularly the case when fuel is burned by engines mounted in motor vehicles. Thus, in order to meet current anti-pollution standards and reduce the pollution of the atmosphere caused by the exhaust gas, the circuit of these gases in vehicles is equipped with a catalytic converter. A catalytic converter transforms the harmful chemical species emitted during the combustion of fuel into non-polluting substances through a post-combustion catalysis process. However, it is known for example from FR-A-2 878 899 that there is an initiation temperature for the catalytic reaction in the catalytic converter. This priming temperature is close to 350 ° C for a gasoline engine and 150 ° C for a diesel engine. In an optimal operation of the catalytic converter, the temperature of the catalytic converter is at least greater than the ignition temperature of the catalytic converter. The temperature of the catalytic converter is particularly insufficient when starting the vehicle.

[0006] Several solutions exist to remedy this problem. Documents US-A-5 529 759, FR-A-2 847 618 and FR-A-2 878 899 thus describe various solutions for electrically heating the catalyst.

But, the heater used is powered by a battery or by the alternator of the vehicle which consumes energy. In addition, in some cases, the battery can be oversized to supply the heater which can cause mass problems. There is therefore a need to heat energy efficiently a catalytic converter vehicle.

This problem is solved according to the invention by a vehicle exhaust gas treatment method comprising a step of heating a catalytic converter by using the energy obtained during the deceleration of the vehicle. Advantageously, the method may also include the following variants: • The catalytic converter is partially heated, the heated portion preferably corresponding to an upstream portion of the catalytic converter in the direction of flow of the exhaust gas. • The energy obtained during the deceleration of the vehicle is converted into electrical energy for heating the catalytic converter. The deceleration energy of the vehicle is converted into electrical energy by an electric machine whose control means comprise means for authorizing and defining a regenerative braking operating mode of the electric machine. This problem is solved according to the invention by a vehicle exhaust gas treatment method comprising a step of heating a catalytic converter by using the energy obtained during the deceleration of the vehicle.

The invention also relates to an exhaust gas treatment device comprising a catalytic converter for treating the exhaust gases and a catalytic converter heating element by using the energy of the deceleration of the exhaust gas. vehicle. Advantageously, this device may comprise the following variants: • The heater is an electrical machine whose control means 25 comprises means for authorizing and defining a regenerative braking operating mode of the electric machine. • The catalytic converter (16) is metallic. • The catalytic converter (16) comprises a catalyst (26), preferably a three-way catalyst. The catalytic converter (16) further comprises a precatalyst (24). Other features and advantages of the invention will appear on reading the following description of the embodiments of the invention, given by way of example and with reference to the appended figures which show: FIG. 1 an example of an exhaust gas treatment device; • Figure 2, another example of exhaust gas treatment device.

There is provided a vehicle exhaust gas treatment method comprising a step of heating the catalytic converter of the vehicle by using the energy obtained during the deceleration of the vehicle. In this way, the heater is not powered by the battery or alternator of the vehicle. Thus, the battery or the alternator need not be oversized to allow the catalytic converter to be heated. The mass of the vehicle is thereby decreased.

[0014] Figures 1 and 2 are examples of exhaust gas treatment devices.

A vehicle 10 comprises an internal combustion engine 12. The motor 12 makes it possible to transform the energy resulting from the combustion of a mixture of fuel and air into mechanical energy.

The vehicle 10 further comprises a line 14 for exhausting the gases. Line 14 serves to treat the pollutants released by the engine 12 to prevent these pollutants are released into the atmosphere.

Line 14 comprises a catalytic converter 16 or catalytic converter which ensures the purification of the exhaust gases. The catalytic converter 16 transforms the polluting species into species that are harmless to the environment by means of a catalysis process. The catalytic converter has a priming temperature that depends in particular on the nature of the engine 12. This priming temperature is close to 350 ° C for a gasoline engine and 150 ° C for a diesel engine.

The vehicle 10 further comprises a member 18 for heating. The member 18 ensures that the temperature of the catalytic converter 16 is greater than its priming temperature. The member 18 is powered by using the energy obtained during the deceleration of the vehicle. The braking energy can be recovered by converting the kinetic energy produced by the rotation of the wheels 22 of the vehicle into electrical energy. This conversion can for example be performed by an electric motor used as a generator and driven by the vehicle.

Since the member 18 is powered by using the energy obtained during the deceleration of the vehicle, the member 18 is not powered by other power supplies that can include the vehicle 10. A battery or alternator are examples of such power supplies which are no longer dedicated to supply the member 18. Thus, the dimensions of the vehicle power supplies are reduced. As a result, the weight of the power supplies is lower, which consequently decreases the total mass of the vehicle.

In addition, the catalytic converter 16 may be partially heated to reduce the energy requirement. In particular, the heated portion of the catalytic converter 16 may be a part upstream in the direction of flow of the gases in the line 14. The ignition of the catalytic converter 16 cold in fact takes place upstream. For example, only the first third of the catalytic converter 16 in the direction of the line 14 traveled by the engine 12 to the outside can be heated since it is in the first third that the priming of the catalytic converter 16 cold .

In addition, the catalytic converter 16 may be partially or completely metallic. The catalytic converter 16 is then heated by applying an electric current to this metal part. The electric current is obtained by converting the deceleration energy of the vehicle 10 into electrical energy, using for example an alternator, noting that according to the invention, the electrical energy is directly used, the need being present at the time of the deceleration, therefore at the very moment when this energy is exploited for the filter, and therefore without consequences for the network. Advantageously, this alternator may be that associated with a vehicle equipped with a stop-and-start type function associated with a function called regenerative braking for energy recovery in case of deceleration, as known for example from patent FR2902705, that is to say by a rotating electrical machine that can be mechanically coupled to the engine of the vehicle to generate current or drive the engine especially during startup (alternator-starter), equipped with control means for controlling modes operating means, said control means comprising supervisory means which determine a vehicle situation and which comprise means for authorizing and defining a regenerative braking operating mode of the electric machine.

In the example of Figure 1, the catalytic converter 16 comprises a single catalyst 26.

In FIG. 2, the catalytic converter 16 comprises, in addition to the catalyst 26, a precatalyst 24. The catalyst 26 is situated downstream of the precatalyst 24 on the line 14. The catalyst 26 is therefore in a position further away from the motor 12 as the precatalyst 24.

In this example, the member 18 can heat the precatalyst 24 and the catalyst 26 to ensure a good depollution of the line 14. In particular, in order to limit the energy consumption, only the precatalyst 24 can be heated because it is upstream in the direction of flow of the gases occurs the priming of the catalytic converter 16 cold.

In an example of use, the catalytic converter 16 may comprise a three-way catalyst or trifunctional. A three-way catalyst provides a triple function of oxidation of unburnt hydrocarbons (HC), oxidation of carbon monoxide (CO) to carbon dioxide (CO2) and reduction of nitrogen oxides (NOx) to nitrogen gas (N2). In this case, the temperature of the three-way catalyst to be reached by heating by the member 18 is about 300 ° C.

In another example of use, the motor 12 is a stratified combustion engine (turbocharger for example). It is interesting to use such a motor 12 because the stratified combustion reduces fuel consumption when the engine 12 operates at low speed and is not fully loaded.

However, stratified combustion generates high combustion temperatures and high oxygen presences that promote the formation of nitrogen oxides (NOx). Thus, in this example, the catalytic converter 16 comprises a NOx trap used as a precatalyst 24. The NOx trap makes it possible to treat NOx by chemical reduction reactions.

The NOx reduction chemical reactions in the NOx trap can be done only beyond a certain temperature threshold. However, when stratified combustion is used at its maximum potential in terms of consumption reduction, the exhaust temperatures of the gases are too low to ensure proper operation of the NOx trap.

Currently, to solve this problem, the maximum potential of stratified combustion is not exploited. The reduction in fuel consumption is therefore not as great as possible.

In contrast, in this example of use, the NOx trap is heated by the member 18. Therefore, even if the temperature of the exhaust gas is low at the exit of the combustion, the exhaust gas can be brought to a sufficiently high temperature to ensure good NOx treatment. The temperature to be attained for the NOx trap by heating by the member 18 is about 200 ° C.

In this way, the maximum potential of stratified combustion in terms of consumption reduction can be used. Fuel consumption is reduced.

The method and the exhaust gas treatment device of the invention therefore make it possible to heat a vehicle catalytic converter economically in energy.

Claims (10)

A method of treating vehicle exhaust gas comprising a step of heating a catalytic converter (16) by using the energy obtained during the deceleration of the vehicle (10). The process of claim 1, wherein the catalytic converter (16) is partially heated. 3. The method of claim 2, wherein the heated portion of the catalytic converter (16) corresponds to an upstream portion of the catalytic converter (16) in the direction of flow of the exhaust gas. 4. The method according to one of claims 1 to 3, wherein the energy obtained during the deceleration of the vehicle (10) is converted into electric heating energy of the catalytic converter (16). 5. The method according to one of claims 1 to 4, wherein the deceleration energy of the vehicle is converted into electrical energy by an electric machine whose control means comprise means for authorizing and defining a braking operating mode recuperative of the electric machine. An exhaust gas treatment device comprising an exhaust gas treatment catalytic converter (16) and a catalytic converter (16) heating member (18) by using the energy of the deceleration of the exhaust gas. vehicle. 7. The device according to claim 6, wherein the heating member (18) is an electrical machine whose control means comprise means for authorizing and defining a regenerative braking operating mode of the electric machine. 8. The device according to one of claims 6 or 7, wherein the catalytic converter (16) is metallic. 9. The device according to one of claims 6 to 8, wherein the catalytic converter (16) comprises a catalyst (26), preferably a three-way catalyst. 10. The device according to one of claims 6 to 9, wherein the catalytic converter (16) further comprises a precatalyst (24).