EP2066881A1

EP2066881A1 - Control device for an engine assembly with a diesel engine that makes possible an improved particle filter regeneration strategy

Info

Publication number: EP2066881A1
Application number: EP07823694A
Authority: EP
Inventors: Hamid Lahjaily; Sebastien Capelle; Benoit Bouvier
Original assignee: Renault SAS
Current assignee: Renault SAS
Priority date: 2006-09-26
Filing date: 2007-08-06
Publication date: 2009-06-10
Also published as: WO2008037902A1; FR2906310A1; FR2906310B1

Abstract

The invention relates to a control device for an engine assembly with a diesel engine for a motor vehicle. When a predetermined value of pressure difference on either side of a particle filter has been reached but when a predetermined particle filter inlet temperature value has not been reached and the discharge valve is not open to its maximum level, the control device is designed so as to deliver, in addition to an order to activate the particle filter regeneration, an order to increase the level of discharge valve opening.

Description

DEVICE FOR CONTROLLING A DIESEL ENGINE ENGINE ASSEMBLY ENABLING A REGENERATION STRATEGY

IMPROVED PARTICLE FILTER

DESCRIPTION

TECHNICAL FIELD The present invention relates generally to the field of the regeneration of a particulate filter arranged in an exhaust circuit associated with a diesel engine for a motor vehicle.

More specifically, the invention relates to a control device of a diesel engine engine assembly for a motor vehicle, for applying an improved strategy of regeneration of the particulate filter.

In addition, the invention relates to a motor assembly 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 particle 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, in order to ensure the elimination of these soot, and thus to cause the regeneration of the filter to 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, it 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 respect, 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 late and very late postinjections, 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 it unburned. Even if this technique proves to be relatively efficient in terms of temperature level conferred, it nevertheless remains very penalizing in terms of cost.

In addition, there is known a solution as described in JP-A-62 255511, 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 make openings of the discharge valve when the required temperature level is already sufficient, this which consequently generates unnecessary motor consumption resulting from the opening of the discharge valve bypassing the passage of the exhaust gases by the turbine of the turbocharger.

STATEMENT OF THE INVENTION

The main purpose of the invention is thus to propose a control device for a motor vehicle engine assembly for a motor vehicle, making it possible to improve the regeneration strategy of the particulate filter fitted to the motor assembly. To do this, the subject of the invention is a device for controlling a diesel motor engine assembly for a motor vehicle, the device comprising: means for comparing a pressure difference value between an input and an output of a particle filter equipping the motor 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 motor assembly, the device being designed to deliver a control order activating the 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 being also designed so as to be able to deliver an order for increasing the opening level of the discharge valve, via the means for controlling the discharge valve; opening of this valve. In addition, when the predetermined value of pressure is reached but the predetermined value temperature is not reached and that 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 preferably being 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 exhaust gases. the exhaust by-passing the turbine of the turbocharger via the discharge valve, and thus maintaining a higher temperature level likely to be sufficient for the regeneration of 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. Moreover, the principle adopted in the present invention makes it possible especially to limit the intensity and the field of application of the post-injection, when the Regeneration strategy is based on such a post-injection technique. This last advantage results in a significant decrease in the dilution of the oil by the fuel, and therefore 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. As such, as mentioned above, it is designed so as to perform a regeneration of the particulate filter by late post-injections to increase the temperature of the exhaust gas at the cylinder head, very late post-injections can also be adjoined to late post-injections, to increase the level of unburned out of breech.

Finally, the subject of the invention is also a method for controlling a diesel engine assembly for a motor vehicle, implemented using a control device as described above, this method consisting, 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 maximal, to be delivered, prior to the activation order 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 in 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 diesel engine 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 Figure 1, we can see a motor assembly 1 for a motor vehicle, this assembly 1 including a diesel engine 2, an air inlet 4, and an exhaust circuit 6 equipped with a 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 Figure 1, the engine assembly 1 further comprises a turbocharger 14 having a compressor 16 placed in the air inlet 4, and rotated by a turbine 18 located between an exhaust duct 20 and a turbine outlet duct 22 of the exhaust circuit 6, the downstream end of the turbine outlet duct 22 opening into the catalyst 8. In addition, a discharge valve 24 , also called waste gate valve, is arranged between the exhaust duct 20 and the turbine outlet duct 22. In known manner, this valve 24 makes it possible to limit the supercharging pressure level at high speeds / high loads, by permitting 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 become more clearly apparent below, one of the peculiarities of the present invention consists in affording the possibility of controlling the discharge valve during the regeneration phases of the filter 10, in order to allow the exhaust gases to pass through. by 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.

Indeed, it is firstly indicated that the control device 12 is designed so as to be able to deliver an order of activation of the regeneration of the particulate filter, using appropriate means 25, but is also designed to in order to be able to deliver an order to increase the opening level of the discharge valve. As can be seen in FIG. 1, the device 12 comprises means 26 making it possible to 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, 30 respectively placed at the inlet and the outlet of the filter 10.

In addition, the device 12 includes means 32 for controlling the opening of the discharge valve 24, and means for comparing an input temperature value of the particulate filter at a predetermined temperature value. As an indication, these 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 for determining an opening level of the discharge valve 24, these means 34 can be integrated within a single assembly with the aforementioned means 32.

Referring now to Figure 2 schematically the principle of operation 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 ΔP between the input and the output of the particle filter 10, and the predetermined pressure value Vpp. Overall and as is known to those skilled in the art, when said value Vpp is reached, reflecting a need to initiate a regeneration of the 10 filter overloaded with soot, the device is designed to deliver the order of activation of the regeneration of the filter. On the other hand, as long as the value Vpp is not reached, the control device 12 delivers no order.

However, before delivering the activation order of the regeneration to the engine 2 by means of the appropriate means, the device is designed to make a comparison between the input temperature value of the particulate filter 10, and the predetermined value of temperature 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 being In addition, it is necessary to increase the opening level of the valve 24. The activation order of the regeneration can then be directly delivered using the appropriate means to the engine 2.

On the other hand, 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 this 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 valve of discharge 24 are used to compare this level to 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 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 benefit at best from the high thermal level associated with the exhaust gases passing through this valve.

In addition, it is preferably only after this opening command 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 of the main injection, to which one or more late post-injections are associated with the aim of increasing the temperature level of the exhaust gas at the cylinder head outlet. 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 are then burnt in the catalyst 8, already primed, and thus allow to further increase the temperature level upstream of the particulate filter 10. Of course, various modifications may be made by those skilled in the art to the invention which has just been described, solely by way of non-limiting examples.

Claims

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 inlet and an outlet 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 order 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 particulate filter with a predetermined temperature value; and

means (34) for determining an opening level of said discharge valve (24), said device being also designed so as 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 that when said predetermined pressure value is reached but said predetermined temperature value is not reached and said determined opening level of said valve discharge device is not maximal, said control device is designed to deliver, in addition to the order of activation of the regeneration of said particulate filter (10), said order of increase of 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 maximum, said control device is designed to deliver said command to increase 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.

4. Engine assembly (1) with a diesel engine (2) for a motor vehicle, comprising a device for control (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 temperature of the exhaust gas at the outlet breech.

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 of 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 maximal, to be delivered, in addition to the order of activating the regeneration of said particulate filter, said order of increasing the opening level of the discharge valve.