JP7522243B2 - METHOD FOR HEATING EXHAUST GAS SYSTEM, ... AND MOTOR VEHICLE - Patent application - Google Patents

Description

The present invention relates to a method for heating an exhaust gas system of a motor vehicle, an exhaust gas system of a motor vehicle, and a motor vehicle equipped with such an exhaust gas system.

To ensure low emissions, the heating disk can be used to preheat the exhaust gas system of a motor vehicle. For this purpose, a carrier mass flow (e.g. air) flows around or perfuses an electrically heated heating disk and heats the downstream catalytic converter. If the carrier mass flow is absent or insufficient, overheating or damage to the heating disk can occur.

Patent document 1 discloses a system and method for estimating the temperature of an exhaust gas system having an electrically heatable catalytic converter, where the temperature of the exhaust gas system is estimated by the electrical characteristics of the electrically heatable catalytic converter.

The disadvantage here is that the absence or insufficient carrier mass flow cannot be reliably detected and the heating disk cannot be protected from damage due to overheating.

U.S. Pat. No. 5,740,675

The problem addressed by the present invention is to provide a method for heating an exhaust gas system of a motor vehicle, an exhaust gas system of a motor vehicle, and a motor vehicle equipped with such an exhaust gas system, which is capable of reliably detecting the absence or insufficient carrier mass flow and which prevents damage to the heating disk due to overheating.

This problem is solved by a method for heating an exhaust gas system of a motor vehicle according to claim 1, an exhaust gas system of a motor vehicle according to claim 8, and a motor vehicle according to claim 10.

A method according to the invention for heating an exhaust gas system of a motor vehicle equipped with a catalytic converter, in particular a method for heating or preheating the catalytic converter, in which the exhaust gas system comprises an electrically heatable heating disk arranged in front of the catalytic converter of the exhaust gas system in the flow direction of the carrier mass flow (e.g. air), the method comprising the following steps:

Determining the (current) values (e.g., readings) of one or more electrical properties at time intervals, particularly at regular intervals, during heating of the electrically heatable heating disk.

Determining whether sufficient carrier mass flow is present by evaluating a determined value of one or more electrical properties of the electrically heatable heating disk.

Insufficient carrier mass flow may be caused, for example, by leaking or pinched valves in the lines leading to the heating disk and the carrier mass flow. Insufficient carrier mass flow may be carrier mass flow that is absent and/or interrupted for intervals of time. Insufficient carrier mass flow may also be when carrier mass flow is (constantly) present but insufficient (i.e., not enough to dissipate the thermal energy from the heated heating disk, which may cause overheating of the heating disk).

By evaluating the determined values of one or more electrical properties, it can be reliably determined whether a carrier mass flow is present and whether it is sufficient to dissipate thermal energy from the heated heating disk. If it is determined that the carrier mass flow is not sufficient, the heating disk can, for example, be switched off, thus preventing overheating of the heating disk.

Preferably, the carrier mass flow in the exhaust gas system can be provided by a secondary air pump or an electric turbocharger.

The one or more electrical properties of the electrically heatable heating disk are preferably the current, electrical resistance, voltage, and/or power of the electrically heatable heating disk.

Power cannot be determined directly. However, it can be found, particularly by calculation, for example, by determining voltage and amperage.

Preferably, the evaluation of the determined values of one or more electrical properties may include:

Generating at least one time-based function from the determined values of the at least one electrical characteristic. Preferably, a characteristic curve is generated from the determined values of the characteristic and the time intervals over which the values were determined. In other words, the determined values of the characteristic are graphed over time on a diagram, resulting in the characteristic curve.

Determining and evaluating at least one derivative (or slope) of a time-based function of the determined value of at least one electrical characteristic of the electrically heatable heating disk.

Here, derivative means the first derivative. Derivative specifically corresponds to differentiation in the mathematical sense, i.e. the slope of a time-based function from a determined (measured) value of an electrical characteristic.

Preferably, the evaluation of the derivative may include:
Comparing the characteristics of the derivative (or slope) to the characteristics of an ideal derivative determined from an ideal function generated from ideal predetermined ideal values. The ideal derivative is also a first derivative in the mathematical sense.

In other words, the actual gradient (of the derivative) can be compared to a target gradient (of the ideal derivative, ideal). It is also conceivable that the evaluation of the value is performed by comparing a time-based function from the determined value to an ideal function, or by comparing the individual value to an ideal value.

The ideal function can be generated (determined) from ideal values corresponding to the carrier mass flow, which are sufficiently large, i.e. in normal conditions. If deviations are found in the comparison, an absence of carrier mass flow and/or an insufficient carrier mass flow can be inferred.

Preferably, the evaluation of the derivative may include:
Comparing the starting value of the derivative to the ideal starting value of the ideal derivative.

In particular, the deviation of the values (i.e. the distance between the respective X-values in the characteristic curve diagram) may be maximum here. Thus, for example, as soon as the heating phase of the heating disk begins, the absence of a carrier mass flow can be inferred and appropriate measures can be taken, such as switching off the heating disk and/or outputting an alarm signal (acoustically and/or visually) to the user or driver of the motor vehicle.

Preferably, the evaluation of the derivative may include:
Determining the period of time required to achieve a predetermined threshold value of the derivative.

Comparing the determined period to the ideal period required to achieve a predetermined threshold of the ideal derivative.

If there is a deviation between the determined period and the ideal period, an absence of carrier mass flow and/or an insufficient carrier mass flow can be inferred.

According to the invention, an exhaust gas system for a motor vehicle is proposed, comprising at least one catalytic converter and at least one electrically heatable heating disk, the exhaust gas system being configured to be able to determine (measure) at least one value of an electrical characteristic of the electrically heatable heating disk.

The exhaust gas system may include a secondary air pump or an electric exhaust gas turbocharger.

Preferably, the exhaust gas system may be configured to be heated by the method according to the above description. With regard to the advantages that may be achieved in this way, reference is made to the relevant description of the method. The measures described and/or discussed below in relation to the method may be useful for the further design of the exhaust gas system.

In particular, the method can heat the catalytic converter of the exhaust gas system.

According to the invention, a motor vehicle is proposed that is equipped with an exhaust gas system according to the above-mentioned embodiment. With regard to the advantages that can be achieved in this way, reference is made to the relevant description of the exhaust gas system. The measures described and/or discussed below in relation to the exhaust gas system can be useful for the further design of the motor vehicle.

The motor vehicle may be equipped with a secondary air pump or an electric exhaust gas turbocharger.

Further advantages and embodiments of the present invention will become apparent from the following description and drawings.

1 shows a schematic diagram of an exhaust gas system for a motor vehicle; The behavior of voltage over time is shown. 1 illustrates the difference between sufficient carrier mass flow present and absent carrier mass flow over time. The behavior of the exhaust gas system under constant voltage is shown as a time-dependent function of the determined values of the characteristics. The behavior of the exhaust gas system under constant voltage is shown by the derivative of the time-dependent function of the determined value of the characteristic. The behavior of the exhaust gas system under constant voltage is shown as a time-dependent function of the determined values of the characteristics. The behavior of the exhaust gas system under constant voltage is shown by the derivative of the time-dependent function of the determined value of the characteristic. The behavior of the exhaust gas system under constant voltage is shown as a time-dependent function of the determined values of the characteristics. The behavior of the exhaust gas system under constant voltage is shown by the derivative of the time-dependent function of the determined value of the characteristic. An enlarged view of the view in FIG. 2d is shown. Shows the behavior of power over time. Shows the difference between present and absent carrier mass flows over time The behavior of the exhaust gas system under constant power is shown as a time-dependent function of the determined values of the characteristics. The behavior of the exhaust gas system under constant power is shown by the derivative of the time-dependent function of the determined value of the characteristic. The behavior of the exhaust gas system under constant power is shown as a time-dependent function of the determined values of the characteristics. The behavior of the exhaust gas system under constant power is shown by the derivative of the time-dependent function of the determined value of the characteristic. The behavior of the exhaust gas system under constant power is shown as a time-dependent function of the determined values of the characteristics. The behavior of the exhaust gas system under constant power is shown by the derivative of the time-dependent function of the determined value of the characteristic. An enlarged view of the view in FIG. 4h is shown.

Figure 1 shows a schematic diagram of an exhaust gas system 10 of a motor vehicle with a catalytic converter 12. The exhaust gas system comprises an electrically heatable heating disk 14. In this case, the carrier mass flow 16 is supplied by a secondary air pump 18 or an electric turbocharger 20. The carrier mass flow 16 flows around or perfuses the heating disk 14 and then enters the catalytic converter 12. In other words, the heating disk 14 is arranged in front of the catalytic converter 12 in the exhaust gas system 10 in the flow direction of the carrier mass flow 16.

When the heating disk 14 is heated (indicated by the arrows), the temperature of the heating disk 14 increases and heats the carrier mass flow 16, which flows around and perfuses the heating disk 14. The thus heated carrier mass flow 16 further heats the catalytic converter 12. In the absence or insufficient presence of the carrier mass flow, thermal energy is not or is only insufficiently removed from the heating disk 14, which may result in overheating of the heating disk 14. This can be prevented by determining and evaluating the characteristic value of at least one electrical characteristic of the heating disk 14.

Figures 2a-2h show the behavior of the exhaust gas system 10 under constant voltage (U). In other words, the voltage (U) over time (t) is constant (see Figure 2a). In this case, Figure 2b shows the difference over time (t) between a present sufficient carrier mass flow 16 (mSL) (solid line) and an absent carrier mass flow 16 (mSL) (dashed line).

2c, 2e and 2g each graph a time-based function 22 of the determined value of the characteristic over time (t). The values of the time-based functions 22 were determined with an absent carrier mass flow 16. These time-based functions 22 are shown by respective dashed lines. Additionally, an ideal function 28 over time (t) is shown by a dashed line. Each ideal function 28 corresponds to an ideal value measured with a present carrier mass flow 16. Thus, the deviation of each value of each characteristic is shown as a function of the present or absent carrier mass flow 16, respectively.

In Figure 2c, the characteristic is graphed as current (I) over time (t). In Figure 2e, the characteristic is graphed as resistance (R) over time (t). In Figure 2g, the characteristic is graphed as power (P) over time (t).

Figures 2d, 2f, and 2h respectively show the derivative 24 of the time-based function 22, as well as the ideal derivative 26 of the ideal function 28. Thus, in Figure 2d, the derivative of current (I') is plotted over time (t). In Figure 2f, the derivative of electrical resistance (R') is plotted over time (t). In Figure 2h, the derivative of power (P') is plotted over time (t).

Figure 3 shows an expanded view of the diagram of Figure 2d. It can be seen that the start value 30 of the derivative 24 deviates significantly from the ideal start value 32 of the ideal derivative 26. In this case, a comparison of these two start values 30, 32 can indicate the presence or absence of a carrier mass flow 16. In this case, the start value 30 is less than the ideal start value 32.

Furthermore, the time required to reach a given threshold 36 can be determined from the respective derivatives 24, 26. Thus, this threshold 36 is reached after a period 34 in the derivative 24. In an ideal derivative 26, this threshold 36 is reached after an ideal period 38. In this case, a comparison of these two periods 34, 38 may indicate the presence or absence of a carrier mass flow 16. In this case, the period 34 is shorter than the ideal period 38.

Figures 4a-4h show the behavior of the exhaust gas system 10 under constant power (P). In other words, the power (P) is constant over time (t) (see Figure 4a). In this case, Figure 4b shows the difference over time (t) between the present carrier mass flow 16 (mSL) (solid line) and the absent carrier mass flow 16 (mSL) (dashed line) (t).

In Figures 4c, 4e and 4g, time-based functions 22 of the determined values of the properties over time (t) are respectively plotted. The values of the time-based functions 22 were determined with an absent carrier mass flow 16. These time-based functions 22 are shown by respective dashed lines. Additionally, ideal functions 28 over time (t) are shown by respective dashed lines. The ideal functions 28 each correspond to an ideal value measured with an existing carrier mass flow 16. Thus, the deviation of the respective values of the respective properties are shown as a function of the existing or absent carrier mass flow 16, respectively.

In Figure 4c, the characteristic is graphed as current (I) over time (t). In Figure 4e, the characteristic is graphed as resistance (R) over time (t). In Figure 4g, the characteristic is graphed as voltage over time (t).

Figures 4d, 4f, and 4h respectively show the derivative 24 of the time-based function 22, as well as the ideal derivative 26 of the ideal function 28. Thus, in Figure 4d, the derivative of the current (I') is graphed over time (t). In Figure 4f, the derivative of the electrical resistance (R') is graphed over time (t). In Figure 4h, the derivative of the voltage (U') is graphed over time (t).

Figure 5 shows an expanded view of the diagram of Figure 4h. It can be seen that the start value 30 of the derivative 24 deviates significantly from the ideal start value 32 of the ideal derivative 26. In this case, a comparison of these two start values 30, 32 can indicate the presence or absence of carrier mass flow 16. In this case, the start value 30 is greater than the ideal start value 32.

Furthermore, the time required to reach a given threshold 36 can be determined from the respective derivatives 24, 26. Thus, this threshold 36 is reached after a period 34 in the derivative 24. In an ideal derivative 26, this threshold 36 is reached after an ideal period 38. In this case, a comparison of these two periods 34, 38 may indicate the presence or absence of a carrier mass flow 16. In this case, the period 34 is longer than the ideal period 38.

Claims (9)

A method for heating an exhaust gas system (10) of a motor vehicle equipped with a catalytic converter (12), the exhaust gas system (10) comprising an electrically heatable heating disk (14) arranged in front of the catalytic converter (12) in the exhaust gas system (10) in a flow direction of a heat carrying medium mass flow (16),
- determining values of one or more electrical properties at predetermined time intervals during said heating of said electrically heatable heating disk (14);
- determining whether there is sufficient heat carrier medium mass flow (16) by evaluating the determined values of the one or more electrical properties of the electrically heatable heating disk (14). The method according to claim 1, characterized in that the heat carrier mass flow (16) is supplied into the exhaust gas system (10) by a secondary air pump (18) or an electric exhaust gas turbocharger (20). The method of claim 1 or 2, characterized in that the one or more electrical properties of the electrically heatable heating disk (14) are the current, electrical resistance, voltage, and/or power of the electrically heatable heating disk (14). evaluating the determined values of the one or more electrical properties
- generating at least one time-based function (22) from said determined values of said at least one electrical characteristic;
- determining and evaluating at least one derivative (24) of the time-based function (22) of the determined value of the at least one electrical characteristic of the electrically heatable heating disk (14). The evaluation of the derivative (24)
- comparing the characteristics of the derivative (24) with characteristics of an ideal derivative (26) determined from an ideal function (28) created from ideal predefined ideal values. The evaluation of the derivative (24)
6. The method of claim 5 , further comprising: comparing a starting value (30) of said derivative (24) with an ideal starting value (32) of said ideal derivative (26). The evaluation of the derivative (24)
- determining a period (34) necessary to achieve a predetermined threshold (36) of said derivative (24);
- comparing the determined period (34) with an ideal period (38) required to achieve the predetermined threshold (36) of the ideal derivative ( 26 ). An exhaust gas system (10) of a motor vehicle comprising at least one catalytic converter (12) and at least one electrically heatable heating disk (14), the exhaust gas system (10) being configured such that at least one value of an electrical characteristic of the electrically heatable heating disk (14) can be determined and the exhaust gas system (10) is configured to be heated by the method of claim 1. A motor vehicle equipped with an exhaust gas system (10) according to claim 8.