Controlling an exhaust gas temperature of a vehicle upstream of a catalyst

Abstract

A control method is implemented in a vehicle comprising a thermal engine whose operating speed is determined by a first setpoint representing a supply air torque, and which produces exhaust gases that feed a catalytic converter exhaust system. This method includes a step (10-30) in which a second setpoint is determined, representing a reserve of air torque intended to heat the catalytic converter and intended to be combined with the first setpoint, and a first exhaust gas temperature upstream of the catalytic converter is regulated according to this second setpoint to promote the achievement of a second chosen exhaust gas temperature in the catalytic converter.

Description

Technical field of the invention

[0001] The invention relates to vehicles comprising at least one thermal engine producing exhaust gases feeding a catalytic exhaust line, and more specifically the regulation of at least one exhaust gas temperature upstream of such a catalyst. State of the art

[0002] Some vehicles, possibly automobiles, include a powertrain (or PWM) comprising at least one internal combustion engine that produces exhaust gases feeding a catalytic converter exhaust system. It should be noted that the invention also relates to hybrid PWMs and therefore also includes a non-internal combustion engine (for example, electric).

[0003] As those skilled in the art know, for an exhaust catalytic converter to function optimally, its internal temperature (resulting at least from the passage of exhaust gases) must reach a predefined temperature range determined by its internal arrangement and the catalytic components it contains. It has therefore been proposed to implement in the vehicles described above a process that allows for a very rapid increase in exhaust gas temperature by increasing the amount of air in the air / fuel mixture feeding the internal combustion engine, thereby reducing the amount of polluting emissions released into the outside air.

[0004] This process (sometimes called "enthalpic boost" – a rapid increase in enthalpy) generally involves, when the operating speed of the internal combustion engine is primarily determined by a first setpoint representing a supply air torque, determining a second setpoint representing a reserve of air torque intended to heat the catalytic converter and which is then combined with the first setpoint. This reserve of air torque results in what is called a "torque structure loop" and therefore a demand for a reduction in ignition timing to meet the current torque demand determined for the internal combustion engine.

[0005] While such a process allows the catalyst to operate optimally and very quickly, it frequently happens that the internal temperature of the catalyst exceeds the upper limit of its predefined temperature range. In this case, at least some of the catalytic components may be degraded, resulting in a decrease in the catalyst's ability to reduce pollutant emissions.

[0006] The invention is therefore intended, in particular, to improve the situation. Presentation of the invention

[0007] In particular, it proposes for this purpose a regulation method, on the one hand, intended to be implemented in a vehicle comprising a thermal engine having in operation a regime based on a first setpoint representing a torque of supply air, and producing exhaust gases supplying an exhaust line with a catalyst, and, on the other hand, comprising a step in which a second setpoint is determined, representing a reserve of air torque intended to heat the catalyst and intended to be combined with the first setpoint.

[0008] This regulation process is characterized by the fact that in its first step, a first temperature of the exhaust gases upstream of the catalyst is regulated according to the second setpoint in order to promote obtaining a second chosen temperature of the exhaust gases in the catalyst.

[0009] Thus, the probability that the internal temperature of the catalyst exceeds the upper limit of its predefined temperature range is (almost) zero, and therefore there is no longer any risk of degradation of at least some of the catalyst's catalytic components due to the realization of a very rapid increase in exhaust gas temperature phase.

[0010] The regulation method according to the invention may include other features which may be taken separately or in combination, and in particular: in its step, after obtaining the second chosen temperature, the second setpoint can be regulated so that the exhaust gases in the catalyst have a temperature less than or equal to the second chosen temperature; in its step, a proportional type regulation of the first temperature can be carried out as a function of a difference between the second chosen temperature and a third temperature of the exhaust gases measured in the catalyst, and of a coefficient which is a function of this difference and between predefined minimum and maximum values;In the presence of the last option, in its stage, when the thermal engine is subject to thermal control by a heat transfer fluid having a fourth temperature, it is possible to determine, on the one hand, a first value which is representative of a nominal air torque reserve intended to heat the catalyst when the coefficient is equal to the predefined maximum value, depending on the regime and first setpoint, and, on the other hand, a second value which is representative of an air torque reserve to implement a function intended to heat the catalyst when the coefficient is equal to the predefined minimum value, depending on the regime, fourth temperature and first setpoint, and a third value representing a chosen physical quantity, then the second setpoint can be determined as a function of the first and second values ​​determined and the coefficient;In the presence of the last sub-option, in its step, when the predefined minimum and maximum values ​​are respectively equal to zero and one, the second setpoint can be determined by summing a first product of the first value determined by the coefficient and a second product of the second value determined by a fourth value equal to one minus the coefficient; also in the presence of the last sub-option, in its step, the second value can be determined by calculating the difference between a fifth value, a function of the engine speed, fourth temperature and first setpoint, and the third value; also in the presence of the last sub-option, in its step, the physical quantity can be chosen from an estimated energy accumulated in the catalyst over a chosen period and an atmospheric pressure outside the vehicle.

[0011] The invention also proposes a computer program product comprising a set of instructions which, when executed by processing means, is suitable for implementing the regulation process of the type presented above in a vehicle comprising a thermal engine having in operation a regime as a function of a first setpoint representative of a supply air torque, and producing exhaust gases supplying a catalytic exhaust line, to regulate at least a first temperature of the exhaust gases upstream of the catalyst.

[0012] The invention also proposes a regulation device, on the one hand, intended to equip a vehicle comprising a thermal engine having in operation a regime based on a first setpoint representing a torque of supply air, and producing exhaust gases supplying an exhaust line with a catalyst, and, on the other hand, comprising at least one processor and at least one memory arranged to perform the operations consisting of determining a second setpoint, representing a reserve of air torque intended to heat the catalyst and intended to be combined with the first setpoint.

[0013] This regulation device is characterized by the fact that its processor and memory are also arranged to perform the operations consisting of triggering a regulation of a first temperature of the exhaust gases upstream of the catalyst according to the second setpoint in order to promote obtaining a second chosen temperature of the exhaust gases in the catalyst.

[0014] The invention also proposes a vehicle, possibly of the automobile type, comprising, on the one hand, a thermal engine having in operation a regime as a function of a first setpoint representing a torque of supply air, and producing exhaust gases supplying an exhaust line with a catalyst, and, on the other hand, a regulation device of the type of that presented above. Brief description of the figures

[0015] Other features and advantages of the invention will become apparent upon examination of the detailed description below, and the accompanying drawings, in which: [ Fig. 1 ] schematically and functionally illustrates an example of the embodiment of a vehicle comprising a control device according to the invention, and a purely thermal powertrain and supervisory computer, [ Fig. 2 ] schematically and functionally illustrates an example of the implementation of a supervisory computer comprising a control device according to the invention, and [ Fig. 3 ] schematically illustrates an example of an algorithm implementing a regulation process according to the invention. Detailed description of the invention

[0016] The invention aims in particular to propose a method of regulation, and an associated regulation device, intended to allow regulation of at least a first temperature T1 of the exhaust gases upstream of a catalyst CL of an exhaust line LE associated with the thermal engine MMT of a vehicle V.

[0017] In what follows, vehicle V is considered, as a non-limiting example, to be of the automobile type. For example, it could be a car, as illustrated in the figure 1 But the invention is not limited to this type of vehicle. It relates in fact to any type of vehicle (land, sea (or river), or air) comprising a powertrain including at least one thermal engine producing exhaust gases feeding a catalytic converter exhaust system.

[0018] Furthermore, in what follows, we consider, by way of non-limiting example, that the powertrain is purely thermal (and therefore comprises only at least one thermal power unit). However, the invention is not limited to this type of powertrain. It also relates to hybrid powertrains, and therefore those comprising at least one thermal power unit and at least one non-thermal power unit (for example, electric).

[0019] We have schematically represented on the figure 1 a vehicle V comprising a purely thermal GMP transmission chain (and therefore comprising at least one thermal drive machine MMT associated with an LE exhaust line with a CL catalyst) and supervised by a CS supervision computer, and a DR regulation device according to the invention.

[0020] As illustrated, the transmission chain also includes, here, an AM drive shaft, a DC coupling device, a BV gearbox, and an AT transmission shaft.

[0021] The operation of the transmission chain (and therefore the powertrain) is supervised by the CS supervisory computer.

[0022] The MMT (thermal drive unit) includes a crankshaft (not shown) that is fixedly attached to the engine shaft AM to drive the latter (AM) in rotation. This MMT is designed to be coupled to the gearbox BV via the DC coupling device. Furthermore, it (MMT) is designed to provide engine torque to move the vehicle V, as instructed by the CS control unit.

[0023] This DC coupling device delivers motor torque for at least one TR1 set of drive wheels of vehicle V when it is in at least a partially coupled (or closed) position and therefore when it couples the MMT thermal drive machine to the AP primary shaft of the BV gearbox.

[0024] For example, the TR1 axle assembly can be located in the front PVV section of vehicle V. It is preferably, as illustrated, coupled to the AT driveshaft via a (here, front) DV differential. However, in a variant, this TR1 axle assembly could be the one referenced as TR2, which is located in the rear PRV section of vehicle V.

[0025] For example, the DC coupling device can also be a clutch (single or double). But it could also be a torque converter or a dog clutch.

[0026] The gearbox (BV) can optionally be automated. In this case, it can be of the type known as a "dual-clutch (or DCT)". But this is not mandatory.

[0027] In the example illustrated (though not exhaustively), the crankshaft of the MMT internal combustion engine is also coupled to a belt (CC), which is itself coupled to a starter-alternator (AD) that is electrically powered by a service battery (BS) (and can also recharge the latter (BS)). Thus, the starter-alternator (AD) can supply torque to the belt (CC), which can then supply this torque to the crankshaft.

[0028] The MMT thermal power unit is also associated with a LE exhaust system with a CL catalyst, which it supplies with exhaust gases during operation. This CL catalyst functions optimally when its internal temperature (resulting at least from the passage of exhaust gases) is within a predefined temperature range determined by its internal arrangement and the catalytic components it contains.

[0029] It should also be noted that, during operation, the MMT thermal power unit has a motor speed (rm) which is a function of an initial setpoint (c1) representing a supply air torque. For example, this initial setpoint (c1) can be provided by the CS supervisory computer.

[0030] As mentioned above, the invention proposes in particular a regulation method intended to allow the regulation of at least a first temperature T1 of the exhaust gases upstream of the catalyst CL of the exhaust line LE of the vehicle V.

[0031] For example, this initial temperature T1 could be the temperature of the exhaust gases exiting the exhaust valves of the MMT internal combustion engine. However, this is not mandatory. Indeed, the initial temperature T1 could be the temperature of the exhaust gases at any point between the exhaust valve outlets and a zone located just before (and therefore upstream of) the inlet of the CL catalyst.

[0032] This (regulatory) process can be implemented at least partially by the DR regulatory device (illustrated at least partially on the Figures 1 And 2) which includes for this purpose at least one PR1 processor, for example a digital signal processor (or DSP), and at least one MD memory. This DR regulation device can therefore be implemented in the form of a combination of electrical or electronic circuits or components (or "hardware") and software modules (or "software").

[0033] The MD memory is random access memory (RAM) to store instructions for the PR1 processor to implement at least part of the control process. The PR1 processor may include integrated circuits (or printed circuit boards), or several integrated circuits (or printed circuit boards) connected by wired or wireless connections. An integrated circuit (or printed circuit board) is defined as any type of device capable of performing at least one electrical or electronic operation.

[0034] In the example illustrated, but not limited to the Figures 1 And 2The DR control unit is part of the CS supervisory control unit. However, this is not mandatory. Indeed, the DR control unit could include its own dedicated control unit, which can then be coupled to the CS supervisory control unit, or it could be part of another control unit embedded in the vehicle V and performing at least one other function within it (V).

[0035] As illustrated, but not limited to, on the figure 3 The (regulation) method according to the invention includes a step 10-30 which is implemented each time a phase of very rapid increase in exhaust gas temperature is triggered so that the CL catalyst can operate optimally as quickly as possible ((almost) without risk of degradation of its catalytic components), in order to reduce the amount of polluting emissions released into the outside air.

[0036] Step 10-30 of the process includes a substep 10 in which a second setpoint, c2, is determined (for example, by the DR control device). This second setpoint represents a reserve of air torque intended to heat the CL catalyst and is to be combined with the first setpoint, c1. For example, this combination could consist of adding the first c1 and second c2 setpoints. However, this is not mandatory. Indeed, more complex combinations using at least one weighting factor can be considered.

[0037] Step 10-30 of the process also includes a substep 20 in which the first temperature T1 of the exhaust gases upstream of the catalyst CL is regulated (for example the DR control device triggers a regulation of) according to the second setpoint c2 (determined in substep 10) to promote obtaining a second chosen temperature T2 of the exhaust gases in the catalyst CL.

[0038] It will be understood that this second chosen temperature T2 falls within the predefined temperature range in which the CL catalyst operates optimally. This second chosen temperature T2 may be predefined or variable depending on atmospheric conditions and / or the estimated condition of the CL catalyst.

[0039] Thanks to this regulation of the initial temperature T1, the probability that the internal temperature of the CL catalyst will exceed the upper limit of its predefined temperature range is (virtually) zero. Consequently, there is (virtually) no longer any risk of degradation of at least some of the catalytic components of the CL catalyst, and therefore the latter (CL) is no longer at risk of a reduction in its capacity to decrease pollutant emissions due to a very rapid increase in exhaust gas temperature.

[0040] It should be noted that this first regulation (of the first temperature T1) is done by the generation (for example by the regulation device DR) of messages including a first instruction for the regulation of the first temperature T1.

[0041] For example, and as illustrated but not limited to the figure 3Step 10-30 of the process may also include a substep 30 in which, after the second selected temperature T2 has been reached, the second setpoint c2 can be regulated (for example, the DR control device can trigger regulation) so that the exhaust gases in the catalyst CL have a temperature that is less than or equal to the second selected temperature T2. This second regulation, this time of the second setpoint c2, is intended to ensure that the internal temperature of the catalyst CL remains within its predefined temperature range once the first regulation has achieved the second selected temperature T2.

[0042] It should be noted that this second regulation (of the second setpoint c2) is done by the generation (for example by the regulation device DR) of messages including a second instruction for the regulation of the second setpoint c2.

[0043] For example, in substep 20 of step 10-30, proportional regulation of the first temperature T1 can be performed (for example, the DR control device can trigger it). In this case, this initial regulation is based on the difference dT between the second selected temperature T2 and a third temperature T3 of the exhaust gases measured in the catalytic converter CL, and on a coefficient cd that is a function of this difference dT and falls between predefined minimum cdmin and maximum cdmax values. We then have dT = T2 - T3, and cd = f(dT).

[0044] For example, a first lookup table tc1, establishing a correspondence between temperature differences and coefficients, can be used to determine the coefficient cd that corresponds to the current temperature difference dT. This first lookup table (or map) tc1 can be obtained in the laboratory or during testing while developing a vehicle similar to vehicle V. It can be stored in the DR control device.

[0045] It should be noted that instead of using a first tc1 correspondence table, we could at least use a mathematical formula giving the evolution of the coefficient cd as a function of the current difference dT.

[0046] It should also be noted that other types of initial regulation known to those skilled in the art can be considered, including an integral type of initial regulation.

[0047] It should also be noted that the MMT thermal power machine can be subjected to thermal control by a heat transfer fluid (generally water, possibly with an additive) having a fourth temperature T4. In this case, in sub-step 20 of step 10-30, one (for example, the DR control device) can begin by determining the first v1 and second v2 values ​​useful for the first control.

[0048] The first value v1 represents a nominal air torque reserve intended to heat the CL catalyst when the coefficient cd is equal to the predefined maximum value cdmax. It is determined as a function of the engine speed rm and the first setpoint c1.

[0049] For example, a second lookup table, tc2, can be used to establish a correspondence between engine speed pairs and initial setpoints and initial values, to determine the first value, v1, that corresponds to the current engine speed rm and initial setpoint c1. This second lookup table (or map), tc2, can be obtained in the laboratory or during testing while developing a vehicle similar to vehicle V. It can be stored in the DR control unit.

[0050] It should be noted that instead of using a second tc2 lookup table, we could at least use a mathematical formula giving the evolution of the first value v1 as a function of the engine speed rm and first setpoint c1 in progress.

[0051] The second value, v2, represents a reserve of air torque to implement a function designed to (very rapidly) heat the CL catalyst when the coefficient cd equals the predefined minimum value cdmin. It can be determined based on the engine speed rm, the fourth temperature T4, the first setpoint c1, and a third value, v3, which represents a chosen physical quantity. For example, this function could be the enthalpy boost function.

[0052] Also, for example, to determine the second value v2 we can use third tc3 and fourth tc4 lookup tables.

[0053] The third lookup table, tc3, establishes a correspondence between engine speed pairs and initial setpoints, and sixth values ​​to determine the sixth value, v6, which corresponds to the current engine speed rm and initial setpoint c1. It should be noted that this third lookup table, tc3, can be identical to the second lookup table, tc2. This third lookup table (or map), tc3, can be obtained in the laboratory or during testing while developing a vehicle similar to vehicle V. It can be stored in the DR control unit.

[0054] It should also be noted that instead of using a third tc3 correspondence table, we could at least use a mathematical formula giving the evolution of the sixth value v6 as a function of the engine speed rm and first setpoint c1 in progress.

[0055] The fourth lookup table, tc4, establishes a correspondence between fourth temperatures and seventh values ​​to determine the seventh value, v7, which corresponds to the current fourth temperature, T4. This fourth lookup table (or map), tc4, can be obtained in the laboratory or during testing while developing a vehicle similar to vehicle V. It can be stored in the DR control unit.

[0056] It should be noted that instead of using a fourth tc4 correspondence table, we could at least use a mathematical formula giving the evolution of the seventh value v7 as a function of the fourth temperature T4 in progress.

[0057] For example, the second value v2 can be equal to the difference between a fifth value v5 and the third value v3, i.e., v2 = v5 - v3. The fifth value v5 is, for example, a function of the engine speed rm, the fourth temperature T4, and the first setpoint c1. As an example, the fifth value v5 can be equal to the product of the sixth v6 and seventh v7 values, i.e., v5 = v6*v7.

[0058] Next, in substep 20 of step 10-30, one (for example the DR control device) can determine the second setpoint c2 as a function of the first v1 and second v2 values ​​determined and the coefficient cd.

[0059] It should also be noted that the predefined minimum (cdmin) and maximum (cdmax) values ​​of the coefficient cd can be equal to zero (0) and one (1), respectively. In this case, in substep 20 of step 10-30, the second setpoint c2 can be determined (for example, by the DR control device) by summing the first p1 and second p2 products, i.e., c2 = p1 + p2. The first product p1 is equal to the multiplication of the first determined value v1 by the coefficient cd, i.e., p1 = v1*cd. The second product p2 is equal to the multiplication of the second determined value v2 by a fourth value v4 equal to one minus the coefficient cd, i.e., p2 = v2*v4 = v2*(1 - cd). We then have c2 = [v1*cd] + [v2*(1 - cd)].

[0060] In other words, the second setpoint c2 is determined here by taking the centroid between the first v1 and second v2 values, each weighted by a coefficient equal to cd and (1 - cd) respectively. However, other, more complex formulas can be used to determine the second value v2 based on the first v1 and second v2 values ​​and the weighting coefficient cd.

[0061] For example, in substep 20 of step 10-30, one (e.g., the DR control device) can use a physical quantity (which is represented by the third value v3) chosen from the estimated energy accumulated in the catalyst CL over a chosen time period (e.g., a complete catalysis cycle) and the atmospheric pressure outside the vehicle V (measured in situ or provided by a database).

[0062] It should also be noted, as illustrated but not limited to the following, on the figure 2, that the CS supervisory computer (or the dedicated computer of the DR regulation device) may also include a mass memory MM1, in particular to store the engine speed rm, the first setpoint c1, the fourth temperature T4, the third temperature T3 and any second chosen temperature T2 and chosen physical quantity, as well as any intermediate data involved in all its calculations and processing.Furthermore, this CS supervisory computer (or the dedicated computer of the DR control device) may also include an IE input interface for receiving at least the engine speed rm, the first setpoint c1, the fourth temperature T4, the third temperature T3, and any second selected temperature T2 and a chosen physical quantity, for use in calculations or processing, possibly after shaping and / or demodulating and / or amplifying them, in a manner known per se, by means of a PR2 digital signal processor. In addition, this CS supervisory computer (or the dedicated computer of the DR control device) may also include an IS output interface, notably for delivering each message containing a first regulation instruction for the first temperature T1, and each possible message containing a second regulation instruction for the second setpoint c2.

[0063] It should also be noted that the invention also proposes a computer program product (or computer program) comprising a set of instructions which, when executed by processing means of the type of electronic circuits (or hardware), such as for example the PR1 processor, is suitable for implementing the regulation process described above to regulate at least the first temperature T1 of the exhaust gases upstream of the catalyst CL of the exhaust line LE of the vehicle V.

Claims

1. A control method for a vehicle (V) comprising a thermal engine (TEM) having, in operation, an operating speed based on a first setpoint representing a supply air torque, and producing exhaust gases supplying an exhaust line (EL) with a catalyst (CL), said method comprising a step (10-30) in which a second setpoint is determined, representing a reserve of air torque intended to heat said catalyst (CL) and intended to be combined with said first setpoint, characterized in that in said step (10-30) a first temperature of said exhaust gases upstream of said catalyst (CL) is regulated according to said second setpoint to promote obtaining a second chosen temperature of said exhaust gases in said catalyst (CL).

2. Method according to claim 1, characterized in thatin said step (10-30), after obtaining said second chosen temperature, said second setpoint is regulated so that said exhaust gases present in said catalyst (CL) a temperature less than or equal to said second chosen temperature.

3. Method according to claim 1 or 2, characterized in that in said step (10-30) a proportional type regulation of said first temperature is carried out as a function of a difference between said second chosen temperature and a third temperature of said exhaust gases measured in said catalyst (CL), and of a coefficient as a function of said difference and between predefined minimum and maximum values.

4. Method according to claim 3, characterized in thatin said step (10-30), in the presence of a thermal power machine (CPM) subject to thermal control by a heat transfer fluid having a fourth temperature, i) a first value representing a nominal air torque reserve intended to heat said catalyst (CL) when said coefficient is equal to said predefined maximum value, as a function of said regime and first setpoint, and ii) a second value representing an air torque reserve to implement a function intended to heat said catalyst (CL) when said coefficient is equal to said predefined minimum value, as a function of said regime, fourth temperature and first setpoint, and a third value representing a chosen physical quantity, then said second setpoint is determined as a function of said first and second determined values ​​and said coefficient.

5. Method according to claim 4, characterized in thatin said step (10-30), when said predefined minimum and maximum values ​​are respectively equal to zero and one, said second setpoint is determined by performing a sum of a first product of said first value determined by said coefficient and a second product of said second value determined by a fourth value equal to one less said coefficient.

6. Method according to claim 4 or 5, characterized in that in said step (10-30) said second value is determined by calculating the difference between a fifth value, based on said regime, fourth temperature and first setpoint, and said third value.

7. A method according to any one of claims 4 to 6, characterized in that in said step (10-30) said physical quantity is chosen from an estimated energy accumulated in said catalyst (CL) over a chosen time period and at an atmospheric pressure outside said vehicle (V).

8. Product computer program comprising a set of instructions which, when executed by processing means, is suitable for implementing the regulation method according to any one of claims 1 to 7, in a vehicle (V) comprising a thermal engine (MIE) having in operation a regime as a function of a first setpoint representative of a supply air torque, and producing exhaust gases supplying an exhaust line (LE) with a catalyst (CL), to regulate at least a first temperature of said exhaust gases upstream of said catalyst (CL).

9. Control device (DR) suitable for equipping a vehicle (V) comprising a thermal engine (MMT) having in operation a speed based on a first setpoint representing a supply air torque, and producing exhaust gases supplying an exhaust line (LE) with a catalyst (CL), said control device (DR) comprising at least one processor (PR1) and at least one memory (MD) arranged to perform the operations of determining a second setpoint, representing a reserve of air torque intended to heat said catalyst (CL) and intended to be combined with said first setpoint, characterized in thatsaid processor (PR1) and memory (MD) are further arranged to perform the operations consisting of triggering a regulation of a first temperature of said exhaust gases upstream of said catalyst (CL) according to said second setpoint to promote obtaining a second chosen temperature of said exhaust gases in said catalyst (CL).

10. Vehicle (V) comprising a thermal engine (MIE) having in operation a regime as a function of a first setpoint representative of a supply air torque, and producing exhaust gases supplying an exhaust line (LE) with a catalyst (CL), characterized in that it further includes a regulating device (DR) according to claim 9.

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