WO2020074283A1

WO2020074283A1 - Optimized recuperation strategy for a hybrid vehicle with electrically heatable catalytic converter

Info

Publication number: WO2020074283A1
Application number: PCT/EP2019/076279
Authority: WO
Inventors: Dietmar Ellmer
Original assignee: Vitesco Technologies GmbH
Priority date: 2018-10-08
Filing date: 2019-09-27
Publication date: 2020-04-16
Also published as: DE102018217161A1

Abstract

The invention relates to a control system and a method for reducing the cooling of a catalytic converter, in particular for a hybrid vehicle. The control system (100) has an internal combustion engine (310) and an electric machine (320). Additionally, the control system (100) has a catalytic converter (200) and at least one actuator (270) which is arranged in a gas path (210). The control system (100) also has a controller (150) which is designed to determine a target braking power in a drag mode of the internal combustion engine (310), operate the electric machine (320) in a generator mode at the target braking power when the target braking power is less than a maximum recuperation power of the electric machine (320) in the generator mode, and increase a mass flow flowing through the gas path (210) by means of the at least one actuator (270).

Description

description

Optimized recuperation strategy for a hybrid vehicle with an electrically heated catalytic converter

The invention relates to a control system and a method for reducing the cooling of a catalytic converter, in particular for a hybrid vehicle. The invention further relates to a program element, a computer-readable medium and a use.

Many vehicles with internal combustion engines have a catalytic converter to reduce pollutant emissions. A minimum temperature is required for the safe catalysis of all relevant pollutants. This minimum temperature, also called "light-off temperature", is, for example, in the case of exhaust gas from ot tomotors in the range from 250 to 300.degree. C. For CNG (methane), this threshold is, for example, above 400.degree of the internal combustion engine - as can occur in hybrid vehicles in particular - the temperature can drop below the light-off temperature, so that safe catalysis is no longer guaranteed when the internal combustion engine is restarted.

The object of the invention is to at least partially overcome the disadvantages of the prior art, in particular to at least partially reduce the cooling of the catalyst.

This object is achieved by the subject matter of the independent claims. Further developments of the invention result from the subclaims and the following description.

One aspect of the invention relates to a control system for reducing the cooling down of a catalytic converter, for an internal combustion engine of a hybrid vehicle, the hybrid vehicle comprising the internal combustion engine and an electric machine having. The control system has a catalytic converter which is arranged in a gas path of the internal combustion engine and at least one actuator in the gas path.

The so-called gas path of the internal combustion engine, through which a fluid - e.g. Fresh air or exhaust gas - flows, can be roughly divided into a so-called fresh air path, which is arranged in front of the internal combustion engine, and a so-called exhaust gas path, which is arranged after the internal combustion engine. The mass flow (also gas throughput or volume flow) of the fluid flow through the gas path can be varied by a number of devices. The number and type of these devices can vary depending on the engine. In the following, all devices in the gas path which allow a variation of the mass flow through the catalytic converter or parts of the catalytic converter and thus a variation of the space velocity are referred to as "actuators". The space velocity is a measure of the quantity of the mass flow of the fluid through a The space velocity is the reciprocal of the dwell time of a gas. The "actuator" in the gas path can be, for example, a throttle valve, air cycle valve, swirl flap (tumble), actuator, valve lift variation on the inlet or outlet side, stowage flap, exhaust flap, flap for exhaust gas recirculation (EGR), gas cycle valve, gas diverter flap, secondary air pump, wastegate and / or variable turbine geometry charger (VTG charger) of a turbocharger, electric compressor, gas cycle valve or any other actuator that changes due to its active operation causes the space velocity of the catalyst.

The control system furthermore has a controller which is set up to determine a target braking power when the internal combustion engine is being towed, and, if the target braking power is less than a maximum recuperation power of the electric machine in generator mode, the electric machine in to operate the generator operation with the target braking power and to increase a mass flow through the gas path by means of the at least one actuator. The internal combustion engine is in towing mode when the internal combustion engine is no longer used to drive the vehicle. This may include switching off the fuel and / or air supply and / or the ignition. If the internal combustion engine is no longer coupled to the moving vehicle or if the vehicle is at a standstill, this can include a standstill of the internal combustion engine. The target braking power can be derived, for example, from a driver's request, for example via the so-called braking target value (BSW). The target braking power can be determined by an assistance system, particularly in the case of at least partially automated vehicles.

The recuperation power is a kinetic energy of the vehicle, which can be recovered as electrical energy during a deceleration of the vehicle, for example during a braking operation, using the electric machine in generator mode. In many vehicles, this is seen as an essential contribution to reducing fuel consumption and reducing CCg. The maximum recuperation power of the electric machine in generator operation can be determined by the dimensioning and the type of the electric machine.

In the prior art, the fluid flow through the gas path is minimized during towing, for example in order to use the braking effect of the engine and thereby relieve the brakes, for example. In contrast to this, in the present invention the gas path is at least partially "throttled", ie the mass flow through the gas path, for example through the engine, is increased by means of the at least one actuator. As a result, the loss torque is reduced by at least some 25% in some internal combustion engines According to the invention, this can be used, for example, to increase the recuperation power of the electric machine in generator operation, which can contribute to a further reduction in the fuel consumption or the CO ₂ emissions of the vehicle. In a variation of the invention, the dethrottling can finally be carried out if this leads to a further increase in the recuperation energy.

In one embodiment, the control is also set up when, in towing operation, the braking power is equal to or greater than the recuperation power, to operate the electric machine in generator mode with the recuperation power and to reduce the mass flow by means of the at least one actuator.

In this embodiment, a possible cooling of the catalytic converter is reduced by the fact that the mass flow through the gas path is reduced in operating phases in which the recuperation power has been exhausted. As a result, less (possibly cooling) fluid flows through the catalyst. In addition, the braking effect of the internal combustion engine can be increased.

In one embodiment, the control system also has a first temperature sensor which is arranged in the region of the catalytic converter and which is set up to determine a first actual temperature of the catalytic converter. The controller is also set up to increase the mass flow by means of the at least one actuator depending on the first actual temperature.

The temperature sensor can be arranged inside the catalytic converter, directly at the catalytic converter or in the vicinity of the catalytic converter. The temperature sensor can be on a catalyst

based temperature model, which may be supported, corrected, adapted and / or optimized by additional sensors. Such a catalyst temperature model can show the local temperatures in the catalyst both in the flow direction (axial) and in the transverse direction (radial, in cylindrical form).

In this embodiment, the increase in the mass flow is dependent on the first actual temperature. This dependency includes that the first actual temperature should be well above the light-off temperature to ensure safe catalysis. If this is the case, a dethrottling strategy can be determined. This can take into account, for example, the difference between the light-off temperature; this can be done, for example, in such a way that the higher the first one, the greater the dethrottling of the gas path

Actual temperature is above the light-off temperature. The dethrottling strategy can also use cooling models of the catalytic converter, for example in such a way that a time remaining until cooling is predicted. The predicted remaining time can take into account, for example, the first actual temperature, exhaust gas temperature models, route-specific parameters (e.g. terrain, wind strength, wind direction) and the traffic situation and determine the dethrottling of the gas path. In general, the dethrottling can be designed so that the shorter the predicted remaining time until it cools down, the lower it is. With this e.g. A balanced optimum can be achieved from an environmental point of view, because both the energy recuperated and the catalyst function are taken into account.

In one embodiment, the control system also has a second temperature sensor, which is arranged in the exhaust gas path and which is set up to have a second one

To determine the actual temperature of the exhaust gas path, wherein the control is also set up to increase the fluid flow by means of the at least one actuator, as a function of the second actual temperature.

The first actual temperature of the catalytic converter can be calculated from the second actual temperature, for example on the basis of temperature models, and one of the dethrottling strategies explained above can be selected as a function thereof. In addition, the determination of the second actual temperature enables the exhaust gas temperature to be taken into account. This extends the dethrottling strategies explained above to the extent that the thermal inertia of the internal combustion engine is also incorporated into the Prediction of the remaining time and may contribute to a further increase in the recuperated energy.

In one embodiment, the control system also has a heat source which is arranged in the region of the catalytic converter, the control system being further set up to do so when the first actual temperature and / or the second

Actual temperature is less than a predefined temperature, to apply a predefined power to the heat source in order to reach the predefined temperature.

The heat source can be designed as a single heat source or as several heat sources. In the case of the individual heat source in particular, the heat source can be arranged in the catalytic converter or close to the catalytic converter upstream, that is to say between the internal combustion engine and the catalytic converter. The heat source can e.g. be designed as an electrically heated heating disc.

The predefined temperature can be in the range of

Light-off temperature of the catalyst are or at a distance above the light-off temperature that a certain "reserve temperature" remains for safe catalysis. If the first actual temperature and / or the second actual temperature is lower than the predefined temperature, the control system applies a predefined power to the heat source, so that the predefined temperature is reached, thus preventing an unacceptable deterioration in the conversion behavior of the catalytic converter.

In one embodiment, the application of the catalyst is dependent on the state of charge of the energy source

Vehicle, such as the car battery, triggered. This can prevent an early discharge of the energy source.

In one embodiment, the controller is set up to interrupt the application of the heat source in order to observe the thermal inertia of the heat source. For example, a excessive power consumption by the heat source and / or excessive and / or unnecessary heating of the heat source can be avoided. Models can also be used for the heating process.

In one embodiment, the predefined power for applying the heat source is at least partially derived from a current recuperation power of the electric machine.

So should the case occur that a local temperature in the catalytic converter during towing falls below a threshold that causes an unacceptable deterioration in the conversion behavior of the catalytic converter when the internal combustion engine is reinserted, the heat source of the catalytic converter is activated for a certain time. This time and the spatial speed set with the aid of the at least one actuator is selected so that the cooled area is quickly and sustainably heated. In terms of energy, the step, insofar as it becomes necessary in a special case, is inexpensive because the directly recuperated energy can be used directly for heating. This leads to better efficiency in contrast to temporary storage in the vehicle's energy source, e.g. the battery.

In one embodiment, current information, such as Fuel quality, individual vehicle characteristics (e.g. vehicle age, driving history, component status, etc.), environmental parameters such as outside temperature, air humidity, traffic density, construction sites, prior knowledge (e.g. a known route profile, driver information (such as the type of driver), or also AI-based system information can be used to adjust all of the above thresholds and setpoints.

In one embodiment, the thresholds and setpoints given above may depend on the available ones

Amount of energy, the energy storage or by the specifications of a comprehensive energy management can be increased or decreased.

Another aspect of the invention relates to a method for reducing the cooling of a catalyst, for an internal combustion engine of a hybrid vehicle, the hybrid vehicle having the internal combustion engine and an electric machine, with the steps:

- Determine, in the trailing operation of the internal combustion engine, a target braking power; and

- If the target braking power is less than the maximum recuperation power of the electric machine in generator mode, operate the electric machine in generator mode with the target braking power and increase the mass flow by means of the at least one actuator.

In one embodiment, the method has the following further steps:

- Determine, by means of a first temperature sensor, which is arranged in the region of the catalytic converter, a first one

Actual temperature of the catalytic converter, and / or, by means of a second temperature sensor which is arranged in the exhaust gas path, a second actual temperature of the exhaust gas path; and

- Increase the mass flow, by means of the at least one actuator, in a positive dependence on the first

Actual temperature.

In one embodiment, the method has the further step:

- If the first actual temperature and / or the second

Actual temperature is less than a predefined temperature, apply a predefined power to a heat source in order to reach the predefined temperature.

Another aspect of the invention relates to a program element which, when executed on a controller, guides the controller to carry out the method described here. Another aspect of the invention relates to a computer-readable medium on which the program element described here is stored.

Another aspect of the invention relates to the use of a control system, as described above, for reducing the cooling of a catalytic converter in an exhaust gas stream, for an internal combustion engine of a hybrid vehicle.

For further clarification, the invention is described on the basis of embodiments shown in the figures. These embodiments are only to be understood as an example, but not as a limitation.

It shows:

1 shows a schematic illustration of a vehicle with a control system according to an embodiment of the present invention;

Fig. 2 is a schematic representation of a dethrottled

Gas paths according to an embodiment of the present invention;

Fig. 3 is a schematic representation of a dethrottled

Gas paths according to an embodiment of the present invention;

Fig. 4 is a flowchart with a method according to a

Embodiment of the present invention.

1 shows a schematic illustration of a vehicle 300 with a control system 100 according to an embodiment of the present invention. The vehicle 300 is designed as a hybrid vehicle 300, with an internal combustion engine 310 and an electric machine 320, which are coupled by means of a coupling element 315. The coupling element 315 can rigidly be guided or have a clutch to separate the combustion engine 310 and the electric machine 320 if necessary. The internal combustion engine 310 has a gas path 210, the gas, for example an exhaust gas, flowing in the direction of the arrow 215 to a catalytic converter 200. An actuator 270 is arranged between the internal combustion engine 310 and the catalytic converter 200. A first temperature sensor 251 is arranged in the region of the catalyst 200. The first temperature sensor 251 supplies a first actual temperature Til of the catalytic converter 200 to a controller 150. The controller 150 is set up to control the actuator 270, the internal combustion engine 310 and the electric machine 320.

FIG. 2 shows a schematic illustration of an unthrottled gas path 210 of the internal combustion engine 310 (see FIG. 1) according to an embodiment of the present invention. The gas path 210 has a fresh air path 212 and an exhaust gas path 211. The catalytic converter 200 is arranged in the exhaust gas path 211. A heat source 205 is arranged in the region of the catalyst 200. Furthermore, a first temperature sensor 251 is arranged in the region of the catalytic converter 200 and a second temperature sensor 252 is arranged in the exhaust gas path 211. The actuators 270, which are each arranged in the fresh air path 212 and in the exhaust gas path 211, are shown in a dethrottled position so that the fluid or gas can flow through the gas path 210 in the direction of the arrow 215. The dethrottled position differs from the throttled position in that a mass flow through the gas path 210 is increased by means of at least one actuator 270. The actuators in gas path 210 can be, for example, a throttle valve, air cycle valve, tumble flap tumbler, actuator, valve lift variation on the inlet or outlet side, damper valve, exhaust gas valve, flap for EGR exhaust gas recirculation, gas cycle valve, gas deflection valve, secondary air pump, wastegate and / or variable-turbine geometry superchargers, turbochargers, electric compressors, gas stroke valves or any other actuator which, through its active operation, brings about a change in the space velocity of the catalytic converter 200. 3 shows a schematic illustration of a throttled gas path 210 according to an embodiment of the present invention. The elements shown and the reference numerals correspond to the elements and reference numerals shown in FIG. 2. The only difference from FIG. 2 is that the actuators 270, which are respectively arranged in the fresh air path 212 and in the exhaust gas path 211, are shown in a throttled position. In the throttled position, the actuators 270 are in a position in which the mass flow through the gas path 210 is reduced in comparison to the dethrottled position by means of at least one of the actuators 270.

4 shows a flow diagram 400 with a method according to an embodiment of the present invention. The method starts with a step 401. In a step 402 it is checked whether the internal combustion engine 310 (see FIG. 1) is in a towing mode. If no, the method is ended in a step 403. If so, then a target braking power is determined in a step 404. In a step 405, it is then queried whether the catalytic converter 200 has a predefined temperature above the light-off temperature. If this is not the case, in a step 410, the heat source 205, in the region of the catalyst 200, is acted upon by the controller 150 with a predefined power Pv in order to reach the predefined temperature Tv. If the catalytic converter 200 has the predefined above the light-off temperature, the electric machine 320 is operated in generator mode in a step 406. In a step 407, it is determined whether a

Target braking power, e.g. was requested by a driver is less than a maximum recuperation power

Electric machine 320 in a generator mode. If this is the case, then in a step 408, the electric machine 320 is operated in generator mode with the target braking power and a mass flow through the gas path 210 is increased by means of the at least one actuator 270. If the target braking power is greater than or equal to the maximum recuperation power, then, in a step 409, the electric machine 320 is operated with the maximum recuperation power and the mass flow is by means of of the at least one actuator 270. The method is ended in a step 411. After the end of the method in step 403 or 411, the method can be started again in step 401. In one embodiment there is a repetition, in particular a regular repetition, of the method.

Reference list

100 control system

150 control

200 catalyst

205 heat source

210 gas path

211 exhaust gas path

212 fresh air path

215 arrow direction

251 first temperature sensor

252 second temperature sensor

270 digits

300 vehicle

310 internal combustion engine

315 coupling element

320 electric machine

400 flowchart

401 - 411 steps

Claims

1. Control system (100) for reducing the cooling of a catalytic converter (200), for an internal combustion engine (310) of a hybrid vehicle (300), the hybrid vehicle (300) having the internal combustion engine (310) and an electric machine (320) comprising the control system (100):

a catalytic converter (200) which is arranged in a gas path (210) of the internal combustion engine (310), at least one actuator (270) in the gas path (210), and a controller (150) which is set up to be in a towing operation of the Determine internal combustion engine (310) a target braking power, and if the target braking power is less than a maximum recuperation power of the electric machine (320) in a generator operation, the electric machine (320) in the generator operation with the target braking power and one Increase mass flow through the gas path (210) by means of the at least one actuator (270).

2. Control system (100) according to claim 1, wherein the controller (150) is further configured to, if, in towing operation, the braking power is equal to or greater than the maximum recuperation power, the electric machine (320) in generator mode with the maximum recuperation power operate and reduce the mass flow by means of the at least one actuator (270).

3. Control system (100) according to claim 1 or 2, further comprising: a first temperature sensor (251) which is arranged in the region of the catalytic converter (200) and which is set up to determine a first actual temperature (Til) of the catalytic converter (200), the controller (150) also being set up to do so , increasing the mass flow, by means of the at least one actuator (270), depending on the first

Actual temperature (Til) to be carried out.

4. Control system (100) according to one of the preceding

Claims, further comprising a second temperature sensor (252) which is arranged in the exhaust gas path (211) and which is set up to determine a second actual temperature (Ti2) of the exhaust gas path (211), the controller (150), is furthermore set up to increase the mass flow by means of the at least one actuator (270) as a function of the second

Actual temperature (Ti2) to be carried out.

5. Control system (100) according to one of the preceding

Claims, further comprising a heat source (205), which is arranged in the region of the catalyst (200), wherein the controller (150) is also set up to do so when the first actual temperature (Til) and / or the second actual temperature (Ti2) is less than a predefined temperature (Tv), the heat source (205) is subjected to a predefined power (Pv) in order to reach the predefined temperature (Tv).

6. Control system (100) according to claim 5, the controller (150) being set up to interrupt the application of the heat source (205) in order to observe the thermal inertia of the heat source (205).

7. Control system (100) according to claim 5 or 6, wherein the predefined power (Pv) for acting on the heat source (205) is at least partially taken from a current recuperation power of the electric machine (320).

8. A method for reducing the cooling of a catalytic converter (200) for an internal combustion engine (310) of a hybrid vehicle (300), the hybrid vehicle (300) having the internal combustion engine (310) and an electric machine (320), with the steps:

- Determining, in the trailing operation of the internal combustion engine (310), a target braking power; and

- If the target braking power is less than the maximum recuperation power of the electric machine (320) in ge generator operation, operate the electric machine (320) in generator mode with the target braking power and increase the mass flow by means of the at least one actuator (270).

9. The method according to claim 8, with the further steps:

- Determining, by means of a first temperature sensor (251), which is arranged in the region of the catalyst (200), a first actual temperature (Til) of the catalyst (200), and / or, by means of a second temperature sensor (252), which the exhaust gas path (211) is arranged, a second actual temperature (Ti2) of the exhaust gas path (211); and - Increase the mass flow, by means of the at least one actuator (270), in a positive dependence on the first actual temperature (Til).

10. The method according to claim 8 or 9, with the further step:

If the first actual temperature (Til) and / or the second actual temperature (Ti2) is less than a predefined temperature (Tv), a heat source (205) is subjected to a predefined power (Pv) in order to reduce the predefined temperature ( Tv) to achieve.

11. Program element which, when executed on a controller (150), instructs the controller (150) to carry out the steps of the method according to one of claims 8 to 10.

12. Computer-readable medium on which a program element according to claim 11 is stored.

13. Use of a control system according to one of claims 1 to 7 or a method according to one of claims 8 to 10 for reducing the cooling of a catalyst (200) in an exhaust gas stream, for an internal combustion engine (310) of a hybrid vehicle (300).