FR2906310A1 - DEVICE FOR CONTROLLING A DIESEL ENGINE ENGINE ASSEMBLY FOR ENHANCED PARTICLE FILTER REGENERATION STRATEGY. - Google Patents

Abstract

The invention relates to a control device of a diesel engine engine assembly for a motor vehicle. When a predetermined value of pressure difference on either side of a particle filter is reached but a predetermined value of the input temperature of particle filter is not reached and the opening level of the discharge valve is not maximum, the control device is designed to deliver, in addition to an order of activation of the regeneration of the particle filter, an order of increasing the opening level of the discharge valve.

Description

DEVICE FOR CONTROLLING A DIESEL-ENGINE ENGINE ASSEMBLY ENABLING A

  TECHNICAL FIELD The present invention relates generally to the field of regeneration of a particulate filter arranged in an exhaust circuit associated with a diesel engine for a motor vehicle. SUMMARY OF THE INVENTION More specifically, the invention relates to a device for controlling a diesel engine engine assembly for a motor vehicle, making it possible to apply an improved strategy for regenerating the particle filter. In addition, the invention relates to a motor assembly 20 for a motor vehicle comprising such a control device, and a control method of an engine assembly implemented by the same device. STATE OF THE PRIOR ART The use of a particulate filter to significantly reduce the amount of soot at the exhaust outlet of a diesel engine usually requires a high temperature level at the inlet of the filter, to ensure the removal of these soot, and thus to cause the regeneration of the filter to 2906310 2 particles. Indeed, the regeneration of the filter consists of burning the soot accumulated in the latter. The known techniques for such regeneration are various. First of all, one is known to delay the main injection, which is associated with one or more late post-injections in order to increase the temperature of the exhaust gas at the cylinder head outlet. In this regard, it is noted that this technique can be supplemented by the addition of one or more post-injections said very late, to increase the level of unburned output of the cylinder head. These unburnt are then burned in the catalyst, already primed, and thus allow to further increase the temperature level upstream of the particulate filter. The main disadvantage of these techniques lies in the creation of a substantial dilution of the oil by the fuel. Indeed, the piston being close to the bottom dead center during the late and very late post-injections, the fuel jets inevitably impact the barrel wall. This impact then generates a dilution of the oil film by the fuel injected in this way, which degrades the quality of the oil, and therefore affects the overall quality of the engine lubrication. Naturally, this detrimental effect of diluting the oil is all the more restrictive that the post-injected quantity required, in order to obtain a sufficient temperature level, is important.

Another known technique is to implant a low pressure injector in the exhaust line upstream of the catalyst, to increase the latter unburned. Even if this technique proves to be relatively efficient in terms of the temperature level conferred, it nevertheless remains very penalizing in terms of cost. Furthermore, there is known a solution as described in JP-A-62255511, of opening the discharge valve fitted to the motor assembly, to supply hot gases to the inlet of the particulate filter. This strategy is triggered as soon as the pressure difference between the inlet and the outlet of the particulate filter reaches a predetermined pressure value, indicating that regeneration of the filter is necessary. However, this type of strategy, the purpose of which is to increase the temperature at the inlet of the particulate filter, sometimes leads to making openings of the discharge valve when the required temperature level is already sufficient, which consequently leads to unnecessary motor consumption resulting from the opening of the discharge valve bypassing the passage of the exhaust gas by the turbine of the turbocharger.

SUMMARY OF THE INVENTION The main purpose of the invention is therefore to propose a device for controlling a motor vehicle diesel engine assembly, making it possible to improve the regeneration strategy of the particulate filter fitted to the engine assembly. .

For this purpose, the subject of the invention is a device for controlling a diesel engine engine assembly for a motor vehicle, the device comprising: means for comparing a pressure difference value between an input and an output a particulate filter fitted to the engine assembly, at a predetermined pressure value; means for controlling the opening of a discharge valve arranged between an exhaust duct and a turbine outlet duct of a turbocharger fitted to the engine unit, the device being designed to deliver a activation order of regeneration of the particulate filter, when the predetermined pressure value is reached. According to the invention, the control device also comprises: means for comparing an input temperature value of the particulate filter with a predetermined temperature value; and - means for determining an opening level of the discharge valve, the device also being designed so as to be able to deliver an order of increasing the opening level of the discharge valve, via the means for order the opening of this valve.

In addition, when the predetermined pressure value is reached but the predetermined temperature value is not reached and the determined opening level of the discharge valve is not maximum, the control device is designed to deliver, in addition to the activation order of the regeneration of the particulate filter, the order of increasing the opening level of the discharge valve. Preferably, the order of increasing the opening level of the valve is delivered prior to the activation order of the regeneration, the increase order being preferably in a maximum opening order of the valve, also called waste gate valve. Thus, the invention generally has the particularity of adding to the basic regeneration strategy, when a too low temperature level is detected at the inlet of the particulate filter to be regenerated, a heat input from the gases Bypassing the turbine of the turbocharger through the discharge valve, and thereby maintaining a higher temperature level may be sufficient to regenerate the filter. This procedure avoids the systematic opening of the discharge valve during regeneration phases, expensive fuel and especially useless when the temperature level at the filter inlet is sufficient. Thus, the motor consumption can advantageously be optimized. In addition, the principle adopted in particular to limit the application of the present invention allows the intensity and post-injection field, when the regeneration strategy is based on such a post-injection technique. This latter advantage results in a substantial decrease in the dilution of the oil by the fuel, and thus advantageously by improved engine lubrication. The invention also relates to a diesel engine engine assembly for a motor vehicle, comprising a control device as described above. In this respect, as mentioned above, it is designed so as to be able to regenerate the particulate filter by late post-injections aimed at increasing the temperature of the exhaust gases at the outlet of the cylinder head, since very late post-injections can also be added to the 15 late post-injections, in order to increase the level of unburnt at the end of the breech. Finally, the subject of the invention is also a method of controlling a diesel engine assembly for a motor vehicle, implemented with the aid of a control device as described above, this method consisting of when the predetermined pressure value is reached but the predetermined temperature value is not reached and the determined opening level of the discharge valve 25 is not maximum, to be delivered, prior to the order of activation of the regeneration of the particulate filter, the order of increasing the opening level of the discharge valve. Other advantages and features of the invention will become apparent from the detailed non-limiting description below.

BRIEF DESCRIPTION OF THE DRAWINGS This description will be made with reference to the appended drawings among which; Figure 1 shows a schematic view of a motor vehicle engine assembly for a motor vehicle, comprising a control device of the assembly according to a preferred embodiment of the present invention; and FIG. 2 represents a flowchart schematizing the operation of the control device shown in FIG. 1. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS Referring firstly to FIG. 1, a motor unit 1 for a vehicle 15 can be seen. automobile, this assembly 1 including a diesel engine 2, an air inlet 4, and an exhaust circuit 6 equipped with an oxidation catalyst 8 and a particulate filter 10, conventional or catalytic. In addition, the assembly 1 is provided with a control unit (not shown) of the diesel engine 2, this control unit comprising conventional means and known to those skilled in the art, as well as a control device 12 according to a preferred embodiment of the present invention, this device 12 being essentially associated with the control of the regeneration of the particulate filter 10. As can be seen in FIG. 1, the engine assembly 1 furthermore comprises a turbocharger 14 having a compressor 16 placed in the air inlet 4, and driven in rotation by a turbine 18 located between an exhaust duct 20 and a turbine outlet duct 22 of the exhaust circuit 6, downstream end of the turbine outlet duct 22 opening into the catalyst 8.

In addition, a discharge valve 24, also called a wastegate valve, is arranged between the exhaust duct 20 and the turbine outlet duct 22. As is known, this valve 24 makes it possible to limit the boost pressure level. at 10 high speeds / high loads, allowing the exhaust gas to pass to a downstream portion of the exhaust system 6 where the catalyst 8 and the filter 10 are located without passing through the turbine 18. As will appear more clearly One of the peculiarities of the present invention is to offer the possibility of controlling the discharge valve during the regeneration phases of the filter 10, in order to allow the exhaust gases passing through this valve 24 to maintain a high temperature level conducive to the removal of soot, due to the fact that they do not undergo expansion within the turbine 18. In fact, it is firstly indicated that the comma device 12 is designed to be able to deliver an order of activation of regeneration of the particulate filter, using appropriate means 25, but is also designed so as to be able to issue an order of increasing the level of the particle filter. opening of the discharge valve.

As shown in FIG. 1, the device 12 comprises means 26 for comparing a pressure difference value between an inlet and an outlet of the particulate filter 10 at a predetermined pressure value. To do this, the means 26 are connected to pressure sensors 28, 5 respectively placed at the inlet and the outlet of the filter 10. In addition, the device 12 incorporates means 32 for controlling the opening of the discharge valve 24, and means for comparing a temperature value at the inlet of the particulate filter to a predetermined temperature value. As an indication, the latter means can be incorporated in the aforementioned means 26, the sensor 28 then being in such a case also capable of determining the inlet temperature of the filter 10. Finally, the control device 12 comprises means 34 enabling to determine an opening level of the discharge valve 24, these means 34 can be integrated within the same set with the aforementioned means 32. Referring now to Figure 2 schematizing the operating principle of the control device 12, it can be seen that the latter, using the means 26, establishes a periodic comparison between the pressure difference value AP between the inlet and outlet of the particulate filter 10, and the predetermined pressure value Vpp. Overall and as is known to those skilled in the art, when said Vpp value is reached, reflecting a need to initiate a regeneration of the soot-overloaded filter 10, the device is designed to deliver the order activating the regeneration of the filter. On the other hand, as long as the value Vpp is not reached, the controller 12 does not issue any commands. However, before issuing the regeneration activation command to the engine 2 by means of the appropriate means, the device is designed to make a comparison between the input temperature temperature value of the particle filter 10, and the predetermined temperature value Vpt. If the value Tent is greater than the predetermined value Vpt, this indicates that the thermal level at the filter inlet is sufficient for a simple activation of the regeneration to eliminate the soot trapped in this filter, without it it is necessary to proceed in addition to an increase in the opening level of the valve 24. The activation order of the regeneration can then be directly delivered using the appropriate means 25 to the engine 2. However if the value Tent is lower than the predetermined value Vpt, reflecting an insufficient thermal level at the input of the filter 10, the device 12 will then seek to increase the opening level of the valve 24 in the case where it is is still possible, in order to keep the exhaust gas a high thermal level unaltered by expansion through the turbine 18.

Thus, the means 34 for determining an opening level of the discharge valve 24 are used to compare this level with a maximum level Nmax, and, in the case where the determined level is below the maximum level Nmax , the device is designed to deliver the order of increasing the opening level via the means 32 for controlling the opening of this valve. Preferably, the order consists in applying a maximum opening of the discharge valve 24, in order to best benefit from the high thermal level associated with the exhaust gas passing through this valve. In addition, it is preferably only after this opening order that the activation order of the regeneration of the filter is delivered, as is schematized in FIG. 2.

In the opposite case where the maximum level Nmax is already reached, then the order of activation of the regeneration of the filter is directly delivered. As an indication, the order of activation of the regeneration of the filter preferably consists of ordering a delay in the main injection, to which one or more late post-injections are associated in order to increase the temperature level. exhaust gases at the outlet of the cylinder head. In this regard, it is noted that this known technique can be supplemented by the addition of one or more very late post-injections, in order to increase the level of unburnt at the outlet of the cylinder head. These unburnt materials are then burnt in the already primed catalyst 8 and thereby further increase the temperature level upstream of the particulate filter 10.

Naturally, various modifications may be made by those skilled in the art to the invention which has just been described, solely as non-limiting examples. 5

Claims (6)

  1. Control device (12) for a motor assembly (1) with a diesel engine (2) for a motor vehicle, said device comprising: - means (26) for comparing a pressure difference value between an input and a output of a particulate filter (10) fitted to said motor assembly (1) at a predetermined pressure value; - means (32) for controlling the opening of a discharge valve (24) arranged between an exhaust duct (20) and a turbine outlet duct (22) of a turbocharger (14) equipping said motor assembly (1), said device being designed to deliver an activation command of the regeneration of said particle filter, when said predetermined pressure value is reached, characterized in that said control device also comprises: - means (26) for comparing an input temperature value of the particle filter with a predetermined temperature value; and means (34) for determining an opening level of said discharge valve (24), said device being also designed to be able to deliver an increase order of said opening level of said discharge valve ( 24), via said means (32) for controlling the opening of said valve, and in that when said predetermined pressure value is reached but said predetermined temperature value is not reached and said level determined opening of said discharge valve is not maximal, said control device is designed to deliver, in addition to the activation order of the regeneration of said particulate filter (10), said control increasing the opening level of the discharge valve (24).   2. Device (12) according to claim 1, characterized in that when said predetermined pressure value is reached but said predetermined temperature value is not reached and that said determined opening level of said discharge valve n is not maximal, said control device is designed to deliver said order of increasing the opening level of said discharge valve prior to said activation order of the regeneration of said particulate filter.   3. Device (12) according to claim 1 or claim 2, characterized in that said order of increasing the opening level of said discharge valve consists of a maximum opening order of this valve. 30   4. Engine assembly (1) with a diesel engine (2) for a motor vehicle, comprising a control device (12) according to any one of the preceding claims.   5. The assembly (1) according to claim 4, characterized in that it is designed so as to be able to regenerate the particulate filter (10) by late post-injections aimed at increasing the temperatures of the exhaust gases. breech outlet. 10   6. A method of controlling a motor assembly (1) with a diesel engine (2) for a motor vehicle, implemented with the aid of a control device according to any one of claims 1 to 4, said method consisting, when said predetermined pressure value is reached but said predetermined temperature value is not reached and said determined opening level of said discharge valve is not maximum, to deliver, in addition to 20 activation order of the regeneration of said particulate filter, said order of increasing the opening level of the discharge valve. 25