FR2540558A1 - Fuel injected vehicle IC engine - Google Patents

Abstract

The air charged, fuel injection, vehicle IC engine has a refractory filter inserted in the exhaust line to separate out solid particles, partic. of soot. There is a periodically operable system for producing engine running conditions such that the accumulated particles are burnt. The filter has a catalytically acting coating on the surface exposed to the exhaust gas, and the system includes exhaust-recycling equipment which feeds at least part of the gas back into the induction circuit. When operating, this equipment alternates rapidly between a setting where gas is recycled and one where it is not.

Description

 The invention relates to an internal combustion air injection and compression machine for vehicles, in particular motor vehicles, comprising a heat-resistant filter placed in the exhaust pipe of the machine and intended in particular for separating particles. exhaust gas scale and a device operable periodically to determine a type of machine operation, and in which the particles accumulated in the filter are burned.

 Internal combustion air injection and compression machines having devices for regenerating the particle filters by periodic combustion of the particles accumulated in the filter are known for example from document DE-OS 26 55 932 and from the European patent. 10 384. In one of the cases, the regeneration device consists of a heating system having an ignition device and a system for supplying fresh air, and which however can only be in operation when the associated filter is not contacted by the exhaust gas.

For this purpose, two particle filters are provided, arranged in parallel and which are alternately contacted by the exhaust gas coming from the internal combustion machine, one of the filters being cleaned while the other filter undergoes the contact phase. the gas.

 In another known regeneration device, the combustion of the particles is triggered by the fact that a special throttling valve and disposed in the suction system of the internal combustion machine is actuated in the closing direction, so that the temperature exhaust gas from the internal combustion air injection and compression machine rises to the ignition temperature of the particles collected in the filter.

 The two known regeneration devices involve a significant multiple expense due to the provision of additional devices which are not per se necessary for the operation of the internal combustion machine.

 The problem which is the basis of the present invention consists in reducing the expense which the periodic cleaning of the particle filter causes in an internal combustion machine with air injection and compression of the type mentioned above.

 The solution to this problem consists in that the filter is provided on its surface exposed to the exhaust gas with a catalytically effective coating and in that the device consists of an exhaust gas return system intended to return to the minus part of the exhaust gas from the internal combustion machine in the suction line and which, during its operating time, can be placed at short time intervals back and forth, successively and alternately, between a position returning the exhaust gas and a position not returning this exhaust gas.

 According to the present invention, provision is therefore made, on the one hand, to provide the filter with a catalytically effective coating and, on the other hand, to actuate a device for returning the exhaust gases possibly present anyway according to a mode of special operation to create the conditions for raising the temperature in the particulate filter in this way, using the exhaust gas return device, enough gas in the suction line of the internal combustion machine so that an increased rejection of carbon waves and hydrocarbons results therefrom. These components, per se unwanted, of incomplete combustion are then catalytically oxidized in the particles, the working temperature of the particle filter can then rise by this exothermic reaction to the ignition limit of the scale particles accumulated in the filter.To obtain a sufficiently high filter temperature z, for example around 400-5000C, it may be necessary to return more exhaust gas in a short period of time than would otherwise be required for NOx reduction of engine exhaust gases.

 It is provided according to the present invention that during this cleaning phase, the exhaust gas return device is switched back and forth and constantly from an open position to a closed position. The exhaust gas return phases then constantly alternate with phases without exhaust gas return, the intermediate phases without exhaust gas return then serving to produce the air necessary for the combustion of accumulated scale particles. in the filter. During operation with exhaust gas return, the latter presents precisely only a very small proportion of excess air or oxygen and which, however, is not sufficient for the combustion of the scale particles accumulated in the filtered.

 Other characteristics and advantages of the present invention will result from the following description of a detailed embodiment and in the light of the drawing in which the single figure represents a schematic view of an internal combustion machine with injection and air compression according to the present invention which is given only by way of example.

 In the figure, the reference numeral 1 designates an internal combustion machine with conventional air injection and compression (diesel internal combustion machine) for vehicles, in particular passenger cars, in the exhaust pipe of gas 3 of which there is a filter 2 for separating the elements of solid particles contained in the exhaust gas of the machine. These particles consist essentially of scale, therefore of unburned carbon which, after a fairly long operating time, however fouls the filter.

 To avoid the necessity of having to change the filter after predetermined operating time intervals, provision is made according to the present invention to regenerate the filter by "periodic removal by combustion" of the scale particles. For this purpose, it is however necessary to have in the particle filter 2 an increased working temperature, for example 400-5000C, which in normal operation can hardly be reached by a diesel engine.

The increased working temperature is reached in the internal combustion injection machine according to the present invention because an exhaust gas return device is present, possibly for the reduction of the nitrogen oxide components of the exhaust gases of the diesel engine, is operated in a special way. This exhaust gas return device consists of a return pipe 5 which returns part of the exhaust gases from the machine 1 into the suction pipe 4 and in which there is a valve 6 which can be controlled by a control unit 7.

 The particular mode of operation of this exhaust gas return device consists in that the gas return valve 6 is switched back and forth constantly and in a pulsating manner between an open position and a closed position. during the operating time of the exhaust gas return device for the purpose of regenerating the particulate filter 2. Thus, alternating periods of operation with gas return and periods without return of exhaust gas are continuously alternated with short The phases with exhaust gas return cause an enhanced emission of CO and HC from the internal combustion machine with injection and clear compression 1 when the excess of air or oxygen is reduced, while in phases without exhaust gas return, the usual excess air is contained in the machine's exhaust gas.

 The increased content of CO and HC in the exhaust gas offers the possibility of increasing the working temperature of the particle filter 2. For this purpose, this filter has a catalytic coating on its surface contacted by the exhaust gas. , so that in this filter, a catalytic oxidation reaction with exothermic effect is produced which greatly increases the temperature in the particle filter. In order for the temperature in the filter to reach that necessary to ignite the scale particles, the exhaust gas return must be calculated so that sufficient quantities of CO and HC are produced.

Possibly, the exhaust gas return in order to regenerate the particulate filter is of a larger amplitude, the exhaust gas return valve 6 must therefore be opened more strongly than is generally necessary for reduce NO. As however during these phases of
x operation, the excess air or oxygen in the exhaust gas of the internal combustion machine 1 decreases sharply and is no longer sufficient for the combustion of scale particles, these exhaust gas return phases necessary to increase the temperature in the filter 2 must alternate with phases in which sufficient oxygen is present in the exhaust gas. To do this, the exhaust gas return valve 6 is always closed so pulsating during the operation of the exhaust gas return device, so that the return of gas is interrupted and sufficient oxygen is produced for the combustion of scale.

 It is assumed, for example, that the entire duration of the regeneration of the particle filter 2 takes place for approximately 90 seconds. During this time, the exhaust gas return valve is opened and closed several times, roughly equal opening and closing phases can then be provided.

For example, the valve can be opened or closed each time for half a second, approximately 60 to 708 of the exhaust gas then being returned during the opening phase of the exhaust gas line 3 to the line 4 d fresh air intake, so that the internal combustion machine 1 lets escape an exhaust gas which contains for example 2% of CO and only 3% of 02. During the phase without return of exhaust gas which 7 as indicated, can also last half a second, then an exhaust gas largely free of CO escapes with approximately 4% of O2 and of which the oxygen surplus is sufficient for the oxidation of the particles of scale accumulated in the filter of particles.

 It may possibly be appropriate for the particle filter to be provided with means for accumulating oxygen so as to further improve the combustion process of the scale particles by maintaining oxidation also during the exhaust gas return phases. .

 The periodic implementation of the filter cleaning device according to the present invention can now take place as a function of determined operating conditions of the engine and / or of the vehicle.

Thus, it is possible to carry out the described cleaning process each time that a predetermined route has been made. I1 is also possible to directly take the exhaust gas back pressure, which increases by the fouling of the filter 2, as a criterion for the implementation of the cleaning device.

 It is interesting to note that no expenditure large enough to produce periodic cleaning and regeneration of the particle filter is involved, in particular when the internal combustion machine with injection and air compression is already equipped with a device. exhaust gas return to reduce nitrogen oxide components in the exhaust gas. It is only necessary to provide the filter with a catalytically effective coating known per se and to operate the exhaust gas return device according to a particular method, namely according to a pulsating operation in which successively alternate at short phase intervals. with exhaust gas return and phases without exhaust gas return.

 It may also be appropriate to take measures which ensure that the cleaning device is used only under specific operating conditions which do not disturb the particular operation of the vehicle or do not influence it negatively. It is then possible to produce the control device 7 so that it acts on the exhaust gas return valve 6 only under specified operating conditions selected from the internal combustion machine for the periodic return of the gases d exhaust and regeneration.

Claims (4)

 1. Internal combustion air injection and compression machine for vehicles, in particular motor vehicles, comprising a heat-resistant filter placed in the exhaust pipe of the machine and intended in particular to separate particles from exhaust gas scale and a device operable periodically to determine a type of machine operation, and in which the particles accumulated in the filter are burned, characterized in that the filter (2) is provided on its surface exposed to the gas of a catalytically effective coating and in that the device consists of an exhaust gas return system (5-7) intended to return at least part of the exhaust gas from the internal combustion machine (1) in the suction line (4), and which during its operating time, can be placed at short time intervals back and forth, successively and alternately, between a position r sending the exhaust gas and a position not returning this exhaust gas.  2. Machine according to claim 1, characterized in that the exhaust gas return device is constituted by a return pipe (5) returning the exhaust gas into the suction pipe (4) of the machine internal combustion (1) and comprising a valve (6) arranged inside, the valve being able to be controlled by a control device (7) so that it can be switched alternately back and forth between an open position and a closed position.  3. Machine according to claim 1 or claim 2, characterized in that the exhaust gas return device (5-7) can be switched on each. once you have traveled a predetermined path length.  4. Machine according to claim 1 or claim 2, characterized in that the exhaust gas return line (5-7) can be switched on each time after having exceeded a predetermined exhaust gas backpressure.