JP7522051B2 - A/F sensor characteristic information generating system and engine control system - Google Patents

Description

The present invention relates to an A/F sensor characteristic information generating system and an engine control system.

Conventionally, engine control devices (ECUs (Electronic Control Units)) installed in automobiles perform feedback control to correct the amount of fuel injected into the engine so that the actual air-fuel ratio converges to a target air-fuel ratio based on the air-fuel ratio detected by an air-fuel ratio sensor (A/F (Air/Fuel ratio) sensor) installed in the exhaust passage of the engine. For example, Patent Document 1 discloses a technology related to engine control that corrects the amount of fuel injected into the engine using the detection value of the A/F sensor.

Moreover, the A/F sensors used for engine control of the above-mentioned automobiles are mainly of the so-called zirconia type, and this zirconia type A/F sensor is disclosed in Patent Document 2.
The zirconia type A/F sensor described in Patent Document 2 includes a zirconia element, an atmosphere side electrode provided on one side (inner surface) of the zirconia element, an exhaust side electrode provided on the other side (outer surface) of the zirconia element, a ceramic coating that covers the exhaust side electrode, and a heater that heats the zirconia element. The A/F sensor also includes a cover that covers the "zirconia element, atmosphere side electrode, exhaust side electrode, and ceramic coating."

JP 2018-145943 A JP 2007-315855 A

However, the zirconia type A/F sensor described above has the problem of poor responsiveness. Therefore, even if the engine control unit (ECU) of the automobile uses the detection value of the zirconia type A/F sensor, which has poor responsiveness, to control the amount of fuel injected into the engine, there is a risk that the engine will not be controlled to operate optimally.

The present invention has been made in consideration of the above problems, and has an object to provide an A/F sensor characteristic information generation system for improving the responsiveness of an A/F sensor. The present invention also has an object to provide an engine control system that controls an engine using the A/F sensor characteristic information generated by the A/F sensor characteristic information generation system.

A first aspect of the present invention for solving the above problem is an A/F sensor characteristic information generation system including an A/F sensor installed in an exhaust pipe of an engine installed in an engine testing device to detect a measured air-fuel ratio of a fluid discharged into the exhaust pipe, a high-response flow meter connected to an intake pipe of the engine to measure an air flow rate of the fluid flowing into the intake pipe, a pressure gauge installed in the intake pipe to measure an intake pipe pressure, a thermometer installed in the intake pipe to measure an intake pipe temperature, and a measuring device to calculate A/F sensor characteristic information, the engine testing device is configured to operate the engine so that the engine injects a predetermined injection amount of fuel and the air flow rate flowing into the engine changes sharply for each cycle, and the measuring device is configured to calculate A/F sensor characteristic information based on the engine's characteristics. The engine testing device is characterized by having a data acquisition unit that acquires the measured air-fuel ratio detected by the A/F sensor, the air flow rate flowing into the intake pipe measured by the high-response flow meter, the intake pipe pressure measured by a pressure gauge, and the intake pipe temperature measured by a thermometer while the engine is operating; a valve-passing flow rate calculation unit that calculates the valve-passing flow rate of the fluid passing through the intake valve of the engine using the acquired air flow rate, intake pipe pressure, and intake pipe temperature; and an A/F sensor characteristic information calculation unit that calculates a reference air-fuel ratio by dividing the calculated valve-passing flow rate by the specified injection amount, and calculates a regression transfer function of the A/F sensor as the A/F sensor characteristic information using the reference air-fuel ratio and the acquired measured air-fuel ratio.

The reason for the above configuration is that the inventors of the present application discovered that if they could accurately calculate the value of the valve-passing flow rate of the fluid passing through the valve of an engine installed and operating in an engine testing device, they could obtain a value that approximates the true value of the air-fuel ratio of the fluid flowing into the engine's exhaust pipe by dividing the valve-passing flow rate by the engine's "predetermined amount of fuel injection."

Therefore, the inventors of the present application have adopted a configuration in which a configuration for calculating the flow rate through the valve as described above (high response flow meter, pressure gauge, thermometer, data acquisition unit, flow rate through valve calculation unit) is provided, and an A/F sensor characteristic information calculation unit calculates a reference air-fuel ratio by dividing the calculated "flow rate through the valve" by the "predetermined amount of fuel injection", and then uses this calculated reference air-fuel ratio and the measured air-fuel ratio detected by the A/F sensor to calculate a regression transfer function of the A/F sensor as A/F sensor characteristic information.
Then, by correcting the measurement value (measured air-fuel ratio) detected by the "A/F sensor" using the "A/F sensor characteristic information (regression transfer function)" obtained according to one aspect of the present invention, an accurate air-fuel ratio can be calculated. That is, according to one aspect of the present invention, a "zirconia type A/F sensor" that is generally used to control automobile engines and has poor responsiveness can be made to function as an "A/F sensor" with high responsiveness.

It is also desirable that the A/F sensor characteristic information calculation unit is configured to use the reference air-fuel ratio as an input value, use a measured air-fuel ratio detected by the A/F sensor corresponding to the reference air-fuel ratio as an output value, perform a Fourier analysis calculation to calculate a transfer characteristic of the A/F sensor, calculate a transfer function from the calculated transfer characteristic, and calculate the regression transfer function from the transfer function.
Moreover, it is preferable that the high-response flowmeter is an ultrasonic flowmeter or a laminar flowmeter.

The second aspect of the present invention is an engine control system having an engine control device that stores the regression transfer function generated by the A/F sensor characteristic information generation system, and an engine equipped with the A/F sensor, wherein the A/F sensor is installed in an exhaust pipe of the engine to measure the air-fuel ratio of a fluid discharged into the exhaust pipe and transmit the measured air-fuel ratio to the engine control device, and the engine control device acquires the air-fuel ratio measured by the A/F sensor, calculates a corrected air-fuel ratio by correcting the acquired air-fuel ratio using the stored regression transfer function, and controls the amount of fuel injected into the engine using the corrected air-fuel ratio.

According to a second aspect of the present invention, in an engine control system that controls an engine equipped with a zirconia-type A/F sensor with poor response, the air-fuel ratio of the fluid flowing through the exhaust pipe measured by the A/F sensor can be corrected to an accurate value, and then the amount of fuel injected into the engine can be controlled. Therefore, the engine control device of the present invention achieves highly accurate engine control.

According to the present invention, it is possible to provide an A/F sensor characteristic information generation system for improving the responsiveness of an A/F sensor. In addition, according to the present invention, it is possible to provide an engine control system that controls an engine using the A/F sensor characteristic information generated by the A/F sensor characteristic information generation system.

1 is a schematic diagram showing a configuration of an A/F sensor characteristic information generating system according to an embodiment of the present invention; 5 is a schematic diagram for explaining a valve passing flow rate calculation process performed by the A/F sensor characteristic information generating system according to the embodiment of the present invention. FIG. 4 is a schematic diagram showing the relationship between the air flow rate measured by a high-response flow meter of the A/F sensor characteristic information generating system according to an embodiment of the present invention and the valve passing flow rate calculated by the A/F sensor characteristic information generating system. FIG. 4 is a flowchart showing a procedure of an A/F sensor characteristic information generating process performed by the A/F sensor characteristic information generating system according to the embodiment of the present invention. 2 is a schematic diagram showing the input/output relationship of the transfer characteristic of the A/F sensor calculated by the A/F sensor characteristic information generating system according to the embodiment of the present invention; FIG. 4 is a schematic diagram for explaining a process of fitting a transfer function to the transfer characteristic of the A/F sensor calculated by the A/F sensor characteristic information generating system according to the embodiment of the present invention to identify the transfer characteristic. FIG. FIG. 1 is a schematic diagram for explaining an example of utilization of A/F sensor characteristic information generated by an A/F sensor characteristic information generating system according to an embodiment of the present invention, and shows an engine control system having an engine control device that stores the A/F sensor characteristic information. 1 is a graph showing the relationship between a regression air-fuel ratio obtained by regressing a detection value of an A/F sensor using A/F sensor characteristic information calculated by an A/F sensor characteristic information generating system according to an embodiment of the present invention, a measured air-fuel ratio detected by the A/F sensor, and a target air-fuel ratio. 1 is a graph showing the relationship between a regression air-fuel ratio obtained by regressing a detection value of an A/F sensor using A/F sensor characteristic information calculated by an A/F sensor characteristic information generating system according to an embodiment of the present invention, a measured air-fuel ratio detected by the A/F sensor, and a target air-fuel ratio.

The following describes an embodiment of the A/F sensor characteristic information generation system of the present invention with reference to the drawings.

First, the configuration of an A/F sensor characteristic information generation system according to an embodiment of the present invention will be described with reference to FIG.

Here, FIG. 1 is a schematic diagram showing the configuration of the A/F sensor characteristic information generation system of this embodiment.

As shown in the figure, the A/F sensor characteristic information generating system W of this embodiment has an A/F sensor 20 installed in the exhaust pipe 6 of an engine E installed on an engine bench (engine testing equipment) B, which detects the air-fuel ratio (measured air-fuel ratio) of the fluid discharged into the exhaust pipe 6, a high-response flowmeter 21 connected to the intake pipe 5 of the engine E and measuring the air flow rate of the fluid flowing into the intake pipe 5, a "pressure gauge 22 and thermometer 23" installed inside the intake pipe 5, and a measuring device 110 that calculates A/F sensor characteristic information (transfer function, regression transfer function).
The A/F sensor characteristic information generating system W also has a fuel supply device 31 that supplies fuel to a fuel injection device (injector) 9 of an engine E installed on an engine bench B, and a fuel flow meter 32 that measures the fuel flow rate of the fuel supplied to the fuel injection device 9.
In the illustrated example, the fuel injection device 9 is configured to inject fuel into the intake pipe 5, but this is just an example. This embodiment can also be applied to a direct injection engine in which the fuel injection device 9 directly injects fuel into the cylinder 11.

In addition, in the data measurement processing step (see S1 in FIG. 4) in which each sensor (A/F sensor 20, high-response flow meter 21, pressure gauge 22, thermometer 233, and fuel flow meter 32) measures the measurement values used to calculate the A/F sensor characteristic information (transfer function, regression transfer function), engine bench B operates engine E so that engine E injects a predetermined amount of fuel and the air flow rate flowing into engine E changes sharply for each cycle.

The A/F sensor 20 is also installed in the exhaust pipe 6 that discharges fluid from the engine cylinder 11, and detects the air-fuel ratio (measured air-fuel ratio) of the fluid flowing through the exhaust pipe 6. The A/F sensor 20 is also electrically connected to a measurement device 110, and upon detecting the air-fuel ratio (measured air-fuel ratio) of the fluid discharged or input into the engine E, the A/F sensor 20 transmits the detected air-fuel ratio (measured air-fuel ratio) to the measurement device 110.
In this embodiment, the A/F sensor 20 is, as an example, a conventional "zirconia type A/F sensor."

The high response flowmeter 21 is connected to one end of the intake pipe 5 that sends air into the engine cylinder 11, and measures the air flow rate (air flow rate) of the fluid (air) flowing into the engine E. The high response flowmeter 21 is also electrically connected to the measurement device 110, and upon measuring the air flow rate of the fluid flowing into the engine E, transmits the measured air flow rate to the measurement device 110.
The high-response flowmeter 21 is an air flowmeter that is more responsive (faster) to fluctuations in air flow rate than the "hot-wire airflow sensor" that is commonly installed in automobile engines E. For example, an ultrasonic flowmeter or a laminar flowmeter (laminar flow type flowmeter) can be used as the high-response flowmeter 21. In the illustrated example, the high-response flowmeter 21 is a laminar flowmeter.

The pressure gauge 22 is installed in the intake pipe 5 and measures the intake pipe pressure. The pressure gauge 22 is also electrically connected to the measurement device 110 and transmits the measured intake pipe pressure to the measurement device 110 upon measuring the intake pipe pressure.
The thermometer 23 is installed in the intake pipe 5 and measures the intake pipe temperature. The thermometer 23 is also electrically connected to the measurement device 110 and transmits the measured intake pipe temperature to the measurement device 110 upon measuring the intake pipe temperature.

Furthermore, the fuel flow meter 32 is provided in a fuel supply pipe connecting the fuel supply device 31 and the fuel injection device 9. Furthermore, the fuel flow meter 32 is electrically connected to the measurement device 110, and measures the flow rate of fuel supplied to the fuel injection device 9 (the amount of fuel injected by the fuel injection device 9). When the fuel flow meter 32 measures the "amount of fuel injection," it transmits the measured "amount of fuel injection" to the measurement device 110.
In this embodiment, the fuel injection device 9 is set to inject a predetermined injection amount (predetermined injection amount), and the predetermined injection amount of fuel is supplied from the fuel supply device 31 to the fuel injection device 9.

The measuring device 110 receives the measurement values (measured air-fuel ratio, air flow rate, intake pipe pressure, intake pipe temperature, fuel injection amount) sent from each sensor (A/F sensor 20, high-response flow meter 21, pressure gauge 22, thermometer 23, fuel flow meter 32). The control device 110 also uses the "air flow rate, intake pipe pressure, intake pipe temperature" from the received measurement values to calculate the "valve passing flow rate" of the fluid passing through the valve of engine E.

The measurement device 110 also calculates a reference air-fuel ratio by dividing the calculated "flow rate through the valve" by the amount of fuel injected by the fuel injection device 9 of the engine E (predetermined injection amount). The measurement device 110 also calculates the transfer function (Gx(s)) of the A/F sensor 20 using the calculated reference air-fuel ratio and the measurement value (measured air-fuel ratio) obtained from the A/F sensor 20, and generates and stores a regression transfer function (Gy(s)) from the transfer function (Gx(s)).

Furthermore, engine bench B includes a dynamometer 50 that applies a load to engine E, which is the test subject, a shaft 53 that connects the rotating shaft of the dynamometer 50 with the rotating shaft of engine E, a dynamo control device 51 that controls the operation of dynamometer 50, and an engine control device 60 that controls the operation of engine E. Engine control device 60 provides control parameters such as valve timing, throttle opening, and ignition advance to engine E, and controls the opening/closing state of throttle valve 7, the valve angle of the intake valve, etc., to control the operation of engine E.
Since the engine bench B is based on a known technique, detailed description thereof will be omitted. Also, since the engine E to be tested is of a known configuration, only the parts directly related to the A/F sensor characteristic information generating system W of this embodiment are shown in the figure.

Next, the functional configuration of the measurement device 110 constituting the A/F sensor characteristic information generating system W of this embodiment will be described with reference to FIG. 1, FIG. 2 and FIG.
Here, Fig. 2 is a schematic diagram for explaining the valve passing flow rate calculation process performed by the A/F sensor characteristic information generating system of this embodiment. Fig. 3 is a schematic diagram showing the relationship between the air flow rate measured by the high response flow meter of the A/F sensor characteristic information generating system of this embodiment and the valve passing flow rate calculated by the A/F sensor characteristic information generating system.

As shown in FIG. 1, the measurement device 110 has a control unit 111, a data acquisition unit 112, a valve passing flow rate calculation unit 113, and an A/F sensor characteristic information calculation unit 114.

The hardware configuration of the measuring device 110 is not particularly limited, but the measuring device 110 can be configured, for example, by a computer (one or more computers) equipped with a CPU, an auxiliary storage device (storage unit), a main storage device (storage unit), a network interface, and an input/output interface. In this case, the "A/F sensor 20, high-response flow meter 21, pressure gauge 22, thermometer 23, and fuel flow meter 32" are connected to the input/output interface. The auxiliary storage device also stores programs for implementing the functions of the "control unit 111, data acquisition unit 112, valve-passing flow rate calculation unit 113, and A/F sensor characteristic information calculation unit 114." The functions of the "control unit 111, data acquisition unit 112, valve-passing flow rate calculation unit 113, and A/F sensor characteristic information calculation unit 114" are implemented by the CPU loading the programs into the main storage device and executing them.

The control unit 111 controls the overall operation of the measurement device 110, and receives various settings and inputs from the user, as well as operation requests to the A/F sensor characteristic information generating system W.
The data acquisition unit 112 acquires the measurement values (measured air-fuel ratio, air flow rate, intake pipe pressure, intake pipe temperature, and fuel injection amount) measured by each sensor (A/F sensor 20, high response flow meter 21, pressure gauge 22, thermometer 23, and fuel flow meter 32) at a predetermined measurement timing.

As shown in FIG. 2, the valve passing flow calculation unit 113 calculates the valve passing flow rate m iv using the air flow rate m _l flowing into the intake pipe 5 measured by the high response flowmeter 21, the intake pipe pressure P _in measured by the pressure gauge 22, the intake pipe temperature T _in measured by the thermometer ₂₃ , the volume V _in of the intake pipe 5, and the following formulas (Equation 1) and (Equation 2).
Here, the "volume V _in of the intake pipe 5" is preset in the valve passing flow calculation unit 113. For example, as a preparation process before performing the A/F sensor characteristic information generation process, the "volume V in of the intake pipe 5 _" is stored in the memory unit of the measurement device 110 (the auxiliary memory unit and main memory unit of the measurement device 110). When calculating the "valve passing flow rate m _iv ", the valve passing flow calculation unit 113 reads out the "volume V _in of the intake pipe 5" from the memory unit and uses it in the calculation process of the "valve passing flow rate m _iv ".

The "air flow rate m _l " measured by the high response flowmeter 21 is approximately the same as the "air flow rate m _th " passing through the throttle valve 7. Therefore, in this embodiment, the valve passing flow rate calculation unit 113 sets the value of the "air flow rate m _l " measured by the high response flowmeter 21 to be the same as the "air flow rate m _th " passing through the throttle valve 7 (see Equation 1 below).
Then, the through-valve flow rate calculation unit 113 substitutes the "intake pipe pressure P _in " measured by the pressure gauge 22, the "intake pipe temperature T _in " measured by the thermometer 23, and the "volume V _in of the intake pipe 5" into the pressure differential equation shown in the following (Equation 2). The through-valve flow rate calculation unit 113 also substitutes the value of the "air flow rate m _l " measured by the high response flowmeter 21 into the "air flow rate m _th " in the pressure differential equation shown in the following (Equation 2). In this way, the "through-valve flow rate m _iv " is calculated.

FIG. 3 shows the relationship between the "valve passing flow rate m _iv " calculated by the valve passing flow rate calculation unit 113 and the "air flow rate m _l " measured by the high response flowmeter 21.
As shown in the figure, the "air flow rate m _l " measured by the high response flowmeter 21 has a delayed response due to the influence of the intake pipe volume, and the flow rate does not become 0 even when the lift amount of the intake valve is closed. On the other hand, the "valve flow rate m _iv " calculated using the above formulas (1) and (2) becomes 0 at the point where the lift amount is closed, which indicates that the flow rate flowing into the cylinder can be calculated appropriately.

Furthermore, the A/F sensor characteristic information calculation unit 114 acquires the fuel injection amount (predetermined injection amount) from the data acquisition unit 112. Then, the A/F sensor characteristic information calculation unit 114 divides the calculated "flow rate through the valve m _iv " by the acquired "fuel injection amount (predetermined injection amount)" to calculate a reference air-fuel ratio.
In addition, the A/F sensor characteristic information calculation unit 114 uses the calculated reference air-fuel ratio and the measurement value (measured air-fuel ratio) obtained from the A/F sensor 20 to calculate the transfer function (Gx(s)) of the A/F sensor 20, and generates and stores a regression transfer function (Gy(s)) from the transfer function (Gx(s)).

Next, the procedure of the A/F sensor characteristic information generating process performed by the A/F sensor characteristic information generating system W of this embodiment will be described with reference to the above-mentioned FIGS. 1 and 2 and FIGS.
Here, Fig. 4 is a flow chart showing the procedure of the A/F sensor characteristic information generation process performed by the A/F sensor characteristic information generation system of this embodiment. Fig. 5 is a schematic diagram showing the input/output relationship of the transfer characteristic of the A/F sensor calculated by the A/F sensor characteristic information generation system of this embodiment. Fig. 6 is a schematic diagram for explaining the process of fitting a transfer function to the transfer characteristic of the A/F sensor calculated by the A/F sensor characteristic information generation system of this embodiment to identify it.

As shown in FIG. 4, first, the A/F sensor characteristic information generating system W performs data measurement processing (S1).

In this data measurement process (S1), the engine bench B is driven, and the engine E installed on the engine bench B injects a predetermined amount of fuel, and the engine E is operated so that the air flow rate flowing into the engine changes sharply for each cycle.
In this embodiment, the engine bench B, for example, provides the engine E with a control parameter for controlling valve timing and controls the valve angle of the intake valve to operate the engine E so that the air flow rate flowing into the engine changes sharply for each cycle. Alternatively, the engine bench B provides the engine E with a control parameter for controlling a throttle opening and controls the throttle opening to operate the engine E so that the air flow rate flowing into the engine changes sharply for each cycle.
The engine bench B fixes the amount of fuel injected into the engine E. That is, the engine bench B operates the engine E so that the engine E injects a predetermined amount of fuel in each cycle.

Then, in the data measurement process (S1), while the engine E is operating as described above, the data acquisition unit 112 of the measuring device 110 acquires the measured air-fuel ratio detected by the A/F sensor 20, the "air flow rate m _l " flowing into the intake manifold 5 measured by the high-response flow meter 21, the "intake manifold pressure P _in " of the intake manifold 5 measured by the pressure gauge 22, the "intake manifold temperature T _in " measured by the thermometer 23, and the fuel injection amount (predetermined injection amount) measured by the fuel flow meter 32.
In addition, the data acquisition unit 112 associates the acquired measurement values (measured air-fuel ratio, air flow rate m _l , intake pipe pressure P _in , intake pipe temperature T _in, injection amount (predetermined injection amount)) for each measurement time and stores them (for example, in a memory unit (auxiliary memory device and main memory device of the measuring device 110) not shown).

Next, the A/F sensor characteristic information generating system W calculates the flow rate through the valve using the measurement value acquired in S1 (S2).
Specifically, in S2, first, the valve-passing flow rate calculation unit 113 of the measurement device 110 acquires "air flow rate m _l , intake pipe pressure P _in , and intake pipe temperature T _in " from the data acquisition unit 112. In addition, the valve-passing flow rate calculation unit 113 reads out "volume V _in of the intake pipe 5" from the memory unit (the auxiliary memory device and main memory device of the measurement device 110).
In addition, in S2, the valve passing flow calculation unit 113 calculates the valve passing flow rate m iv using the "air flow rate m _l flowing into the intake pipe 5" measured by the high response flowmeter 21, the "intake pipe pressure P _in " measured by the pressure gauge 22, the "intake pipe temperature T _in " measured by the thermometer 23, the "volume _{V in} of the intake pipe 5", and the above-mentioned "(Equation 1) and (Equation 2)".

Next, the A/F sensor characteristic information generating system W performs a process of calculating a reference air-fuel ratio (S3).
Specifically, in S3, the A/F sensor characteristic information calculation unit 114 of the measurement device 110 acquires the "fuel injection amount (predetermined injection amount)" from the data acquisition unit 112, and acquires the above calculated "valve passing flow rate m _iv " from the valve passing flow rate calculation unit 113. Then, the A/F sensor characteristic information calculation unit 114 calculates a value obtained by dividing the above "valve passing flow rate m _iv " by the above "fuel injection amount (predetermined injection amount)" as the "reference air-fuel ratio."
In this embodiment, the fuel injection amount (predetermined injection amount) measured by the fuel flow meter 32 is used to calculate the "reference air-fuel ratio", but this is not particularly limited. In this embodiment, since the fuel injection amount injected into the engine E is fixed, the fixed fuel injection amount (predetermined injection amount) may be stored in advance in the storage unit of the measurement device 110. In this case, the "reference air-fuel ratio" may be calculated using the "fuel injection amount (predetermined injection amount)" read out by the A/F sensor meter characteristic information calculation unit 114 from the storage unit.

Next, the A/F sensor characteristic information generating system W performs a process of calculating a transfer function (S4).
In the transfer function calculation process (S4), first, as shown in FIG. 5, the A/F sensor characteristic information calculation unit 114 of the measurement device 110 performs a Fourier analysis calculation using the reference air-fuel ratio (A/F) calculated in S3 as an input value and the air-fuel ratio measured by the A/F sensor 20 at the measurement time corresponding to the reference air-fuel ratio (A/F) (measured air-fuel ratio (A/F')) as an output value, to calculate the transfer characteristic (Gx'(s)) of the A/F sensor.
In addition, the gain diagram of FIG. 6 shows an example of the transfer characteristic (Gx'(s)) obtained by the above-mentioned Fourier analysis calculation.
Furthermore, in S4, the A/F sensor characteristic information calculation unit 114 fits an arbitrary transfer function (Gx(s)) to the calculated transfer characteristic (Gx'(s)) and identifies the parameters of the transfer function (Gx(s)) so that "Gx'(s) = Gx(s)" (see FIG. 6).

なお、Ａ/Ｆセンサ特性情報算出部１１４は、図示しない記憶部（計測装置１１０の補助記憶装置及び主記憶装置）に、Ｓ４で算出した「伝達特性（Ｇｘ’（ｓ））、伝達関数（Ｇｘ（ｓ））」と、Ｓ５で算出した回帰伝達関数（Ｇｙ（ｓ））に記憶させる。 Next, the A/F sensor gauge characteristic information generating system W performs a process of calculating a regression transfer function (S5).
In this regression transfer function calculation process (S5), the A/F sensor characteristic information calculation unit 114 of the measurement device 110 uses the transfer function (Gx(s)) calculated in S4 to calculate the regression transfer function (Gy(s)) shown in the following (Equation 3).
The "lowpass filter" has the characteristic of not interfering with Gx(s) by using a filter with a cutoff set at a higher frequency than the band of Gx(s).

The A/F sensor characteristic information calculation unit 114 stores the “transfer characteristic (Gx′(s)) and transfer function (Gx(s))” calculated in S4 and the regression transfer function (Gy(s)) calculated in S5 in a memory unit (auxiliary memory device and main memory device of the measuring device 110) not shown.

The reason why the A/F sensor characteristic information generating system W of this embodiment is configured as described above is that the inventors of the present application discovered that if it is possible to accurately calculate the value of the valve passing flow rate of the fluid passing through the valve of engine E, then by calculating a value obtained by dividing the valve passing flow rate by the "fuel injection amount" of engine E installed on engine bench B, it is possible to obtain a value that is close to the true value of the air-fuel ratio of the fluid discharged into the exhaust pipe 6.
In addition, the inventors of the present application have adopted a configuration in which a reference air-fuel ratio is calculated by dividing the "flow rate through the valve" by the "predetermined amount of fuel injected", and the calculated reference air-fuel ratio and the measured air-fuel ratio detected by the A/F sensor 20 are used to calculate a regression transfer function of the A/F sensor as A/F sensor characteristic information.
As a result, an accurate air-fuel ratio can be calculated by correcting the measurement value (measured air-fuel ratio) detected by the "A/F sensor" using the "A/F sensor characteristic information (regression transfer function)" obtained by this embodiment. In other words, according to this embodiment, a "zirconia type A/F sensor" that is generally used to control the engine E of an automobile and has poor responsiveness can be made to function as an "A/F sensor" with high responsiveness.

Specifically, the inventors of the present application have noticed that the flow rate of fluid passing through the intake valve of engine E is approximately the same as the flow rate of fluid passing through the exhaust valve of engine E, and have adopted a configuration in which a high-response flowmeter 21, such as a laminar flowmeter, is connected to the intake pipe 5 of the engine installed on engine bench B, and the high-response flowmeter 21 measures the "air flow rate of air (fluid) flowing into the intake pipe 5." With this configuration, even transient air flow rates, where the flow rate of air flowing into the intake pipe 5 of engine E changes sharply, can be measured with high response, and a highly accurate value of the air flow rate can be obtained.

In addition, the inventors of the present application have noted that the "valve passing flow rate m _iv of the fluid passing through the intake valve", which is approximately the same as the "valve passing flow rate of the fluid passing through the exhaust valve", can be calculated using the "air flow rate m _l flowing into the intake pipe 5", the "intake pipe pressure P _in ", the "intake pipe temperature T _in ", the "volume V _in of the intake pipe 5", and the "pressure differential equation" shown in the above-mentioned (Equation 2).
Therefore, the inventor of the present application has adopted a configuration in which "a pressure gauge 22 and a thermometer 23" are provided in the intake pipe 5 to measure "the intake pipe pressure P _in and the intake pipe temperature T _in ". In addition, the measuring device 110 is provided with a configuration of a valve passing flow rate calculation unit 113 that calculates the valve passing flow rate of the fluid passing through the valve of the engine E using the "air flow rate m _l " measured by the high response flow meter 21, the "intake pipe pressure P _in " measured by the pressure gauge 22, the "intake pipe temperature T _in " measured by the thermometer 23, the "volume V _in of the intake pipe 5", and the pressure differential equation of the above-mentioned (Equation 2). This makes it possible to obtain an accurate value of the "valve passing flow rate" of the engine E.

In addition, in this embodiment, since an accurate value of the "flow rate through the valve" can be calculated, the measurement device 110 is configured to calculate a "reference air-fuel ratio" by dividing the calculated "flow rate through the valve" by the "predetermined amount of fuel injected", and an A/F sensor characteristic information calculation unit 114 is provided to calculate a regression transfer function of the A/F sensor as A/F sensor characteristic information using the "reference air-fuel ratio" and the "measured air-fuel ratio" detected by the A/F sensor 20. An accurate air-fuel ratio can be calculated by using this "A/F sensor characteristic information (regression transfer function)" to correct the measurement value (measured air-fuel ratio) detected by the "A/F sensor".

Engine Control System of Application of the Present Invention
Next, a usage example of the A/F sensor characteristic information generated by the A/F sensor characteristic information generating system W of this embodiment will be described with reference to FIG.
Here, FIG. 7 is a schematic diagram for explaining an example of utilization of the A/F sensor characteristic information generated by the A/F sensor characteristic information generating system of this embodiment, and shows an engine control system having an engine control device that stores the A/F sensor characteristic information.

The engine control system shown in the figure has an engine E equipped with an A/F sensor 20, and an engine control unit (hereinafter referred to as "ECU") 200 that controls the operation of the engine E, and is installed in an automobile for use.

The ECU 200 controls the operation of the engine E mounted on the automobile, and includes an engine control unit 201 that controls the operation of the engine E, and a storage unit 203 that stores the "A/F sensor characteristic information (regression transfer function (Gy(s)))" generated by the A/F sensor characteristic information generating system W of the embodiment described above.

The A/F sensor 20 is installed in the exhaust pipe 6 of the engine cylinder E, detects the air-fuel ratio of the fluid discharged from the engine E, and transmits the detected air-fuel ratio to the ECU 200.

In addition, when the engine control unit 201 of the ECU 200 receives the “air-fuel ratio” transmitted from the A/F sensor 20, it reads out the “regression transfer function (Gy(s))” stored in the memory unit 203, and applies the read-out “regression transfer function (Gy(s))” to the received “air-fuel ratio”, thereby correcting the “air-fuel ratio” measured by the A/F sensor 20 to a “corrected air-fuel ratio”.
Thereafter, the engine control unit 201 controls the amount of fuel injected by the engine E using the "corrected air-fuel ratio".

The illustrated ECU 200 uses the A/F sensor characteristic information (regression transfer function (Gy(s))) of the A/F sensor 20 generated by the A/F sensor characteristic information generating system W of the embodiment described above to correct the air-fuel ratio measured by the A/F sensor 20, and uses the corrected air-fuel ratio to control the operation of the engine E. Other than this function, the ECU 200 is the same as that of known technology, and detailed description thereof will be omitted.

In this manner, the A/F sensor characteristic information generating system W of this embodiment generates A/F sensor characteristic information indicating the characteristics of the A/F sensor 20 and stores it in the ECU 200, thereby making it possible to control the engine E using the measurement value (corrected air-fuel ratio) of the A/F sensor 20, which has improved responsiveness.
Therefore, for example, even in a vehicle equipped with an engine E equipped with a zirconia type A/F sensor, which is a mainstream component in automobiles, the engine E can be controlled to operate optimally by configuring it as in the above-mentioned ECU 200 (for example, by changing the program of an existing ECU).

Note that, although FIG. 7 above illustrates an engine control system that controls an engine E mounted on an automobile, the present invention is not limited to this. For example, the A/F sensor characteristic information (regression transfer function (Gy(s))) may be used in an engine testing device that tests an engine E equipped with a zirconia-type A/F sensor 20. In this case, the "regression transfer function (Gy(s))" may be stored in an engine control device that controls the operation of the engine E, and the engine control device may use the regression transfer function (Gy(s)) to correct the air flow rate measured by the A/F sensor 20, and use the corrected air flow rate to control the operation of the engine E and perform various engine tests.

In addition, in the above-described embodiment, an ultrasonic flowmeter or a laminar flowmeter was shown as an example of the high-response flowmeter 21, but any flowmeter that is more responsive (faster) to fluctuations in air flow rate than a hot-wire airflow sensor can be applied to the present invention.

For example, the high-response flowmeter 21 can use the flow measurement system described in the document filed by the applicant of the present application (JP Patent Publication No. 2020-1134243 (Patent Document 3)). In this flow measurement system, the characteristics (differential pressure sensor characteristic information) of the differential pressure sensor mounted on the laminar flowmeter (laminar flow type flowmeter) are calculated in advance, and the measurement value (air flow rate (differential pressure measured by the differential pressure sensor)) measured by the laminar flowmeter is corrected using the differential pressure sensor characteristic information, and the corrected value is regarded as the air flow rate.

Specifically, the laminar flowmeter of the flow measurement system described in Patent Document 3 above is provided with a main body in which a laminar flow element is provided, and a differential pressure sensor that measures and outputs the differential pressure between the static pressure upstream of the laminar flow element and the static pressure downstream of the laminar flow element.
The differential pressure sensor also has a first connecting pipe that acquires the static pressure in the upstream portion of the laminar flow element, a second connecting pipe that acquires the static pressure in the downstream portion of the laminar flow element, and a sensor portion to which the first and second connecting pipes are respectively connected and which measures the differential pressure between the static pressure in the upstream portion and the static pressure in the downstream portion.

The differential pressure sensor characteristic information is obtained by removing the differential pressure sensor from the laminar flowmeter before the process of calculating the intake air flow rate of the engine, connecting an air inlet passage to the first connecting pipe of the removed differential pressure sensor, and leaving one end of the second connecting pipe of the removed differential pressure sensor open to the atmosphere. In the above state, air is allowed to flow into the differential pressure sensor through the air inlet passage, measuring the pressure of the air inlet passage near the first connecting pipe as the first pressure, and having the differential pressure sensor measure the differential pressure between the pressure of the first connecting pipe and the pressure of the second connecting pipe as the second pressure. The relationship between the first pressure and the second pressure is converted into frequency characteristic information represented by gain and phase for each frequency, and the frequency characteristic information is represented by a transfer function.

When the flow measurement system described in Patent Document 3 is applied to the high response flowmeter 21 of the A/F sensor characteristic information generating system W of this embodiment, pre-calculated differential pressure sensor characteristic information is stored in the measuring device 110. A laminar flowmeter is used for the high response device 21 of the A/F sensor characteristic information generating system W. When the data acquiring unit 112 acquires a measurement value (for convenience of explanation, referred to as "laminar air flow rate") measured by the laminar flowmeter, it corrects the "laminar air flow rate" using the stored differential pressure sensor characteristic information, and the corrected air flow rate obtained by the correction is set as the "air flow rate m _l flowing into the intake pipe 5" of the above-mentioned embodiment.
In this case as well, the same effects as those of the above-described embodiment can be obtained.

Next, the relationship between the regression result (A/F sensor regression value) obtained by correcting the actual measurement value of the A/F sensor 20 using the A/F sensor characteristic information (regression transfer function (Gy(s))) calculated by the A/F sensor characteristic information generating system W of this embodiment, the measurement value of the A/F sensor 20, and the target air-fuel ratio will be described with reference to Figures 8 and 9.

Here, Figures 8 and 9 are graphs showing the relationship between the regression value (regressed air-fuel ratio) obtained by regressing the detection value of the A/F sensor using the A/F sensor characteristic information calculated by the A/F sensor characteristic information generating system of this embodiment, the measurement value (measured air-fuel ratio) detected by the A/F sensor, and the target air-fuel ratio (true value of the air-fuel ratio).

FIG. 8 shows a graph in which the air flow rate is stepped by one cycle and the A/F ratio is changed sharply. As shown in the graph of FIG. 8, the measurement value of the A/F sensor 20 has poor response to the target air-fuel ratio (true value of the air-fuel ratio), and an instantaneous value cannot be obtained. On the other hand, FIG. 8 shows that the A/F sensor regression value (regression result) properly captures the instantaneous value. FIG. 9 shows the results of a similar investigation to FIG. 8, in which the air flow rate is stepped by one cycle in multiple conditions. As shown in FIG. 9, it can be seen that the regression result properly captures the target air-fuel ratio (true value) in other respects besides those shown in FIG. 8.
In this manner, it has been confirmed that, according to this embodiment, by calculating the A/F sensor characteristic information (regression transfer function (Gy(s)) of the A/F sensor 20, the "A/F sensor 20" having poor responsiveness can be made to function as an "A/F sensor" having high responsiveness, thereby improving the responsiveness of the A/F sensor 20.

W... A/F sensor characteristic information generating system 20... A/F sensor 21... high-response flow meter 22... pressure gauge 23... thermometer 31... fuel supply device 32... fuel gauge 110... measuring device 111... control unit 112... data acquisition unit 113... valve passing flow rate calculation unit 114... A/F sensor characteristic information calculation unit

B... Engine bench 50... Dynamometer 51... Dynamo control device 53... Shaft 60... Engine control device

E... engine 5... intake pipe 6... exhaust pipe 7... throttle valve 9... fuel injector 11... engine cylinder

Claims (4)

An A/F sensor characteristic information generating system including an A/F sensor installed in an exhaust pipe of an engine installed in an engine testing device, the A/F sensor detecting a measured air-fuel ratio of a fluid discharged into the exhaust pipe, a high-response flow meter connected to an intake pipe of the engine, the high-response flow meter measuring an air flow rate of the fluid flowing into the intake pipe, a pressure meter installed in the intake pipe, the pressure meter measuring an intake pipe pressure, a thermometer installed in the intake pipe, the temperature meter measuring an intake pipe temperature, and a measuring device calculating A/F sensor characteristic information,
the engine testing apparatus is adapted to operate the engine so that the engine injects a predetermined injection amount of fuel and so that an air flow rate into the engine changes sharply for each cycle;
The measuring device includes:
a data acquisition unit that acquires, while the engine testing device is operating the engine, a measured air-fuel ratio detected by the A/F sensor, an air flow rate flowing into the intake pipe measured by the high-response flow meter, an intake pipe pressure measured by a pressure gauge, and an intake pipe temperature measured by a thermometer;
a valve passing flow rate calculation unit that calculates a valve passing flow rate of a fluid passing through an intake valve of the engine using the acquired air flow rate, the intake pipe pressure, and the intake pipe temperature;
an A/F sensor characteristic information calculation unit that calculates a reference air-fuel ratio by dividing the calculated flow rate through the valve by the specified injection amount, and calculates a regression transfer function of the A/F sensor as the A/F sensor characteristic information using the reference air-fuel ratio and the acquired measured air-fuel ratio. The A/F sensor characteristic information generating system according to claim 1, characterized in that the A/F sensor characteristic information calculation unit uses the reference air-fuel ratio as an input value, uses a measured air-fuel ratio detected by the A/F sensor corresponding to the reference air-fuel ratio as an output value, performs a Fourier analysis calculation to calculate the transfer characteristics of the A/F sensor, calculates a transfer function from the calculated transfer characteristics, and calculates the regression transfer function from the transfer function. The A/F sensor meter characteristic information generating system according to claim 1 or 2, characterized in that the high-response flow meter is an ultrasonic flow meter or a laminar flow meter. An engine control system having an engine control device that stores the regression transfer function generated by the A/F sensor characteristic information generating system according to any one of claims 1 to 3, and an engine equipped with the A/F sensor,
the A/F sensor is installed in an exhaust pipe of the engine, measures an air-fuel ratio of a fluid discharged into the exhaust pipe, and transmits the measured air-fuel ratio to the engine control device;
The engine control system is characterized in that the engine control device acquires the air-fuel ratio measured by the A/F sensor, calculates a corrected air-fuel ratio by correcting the acquired air-fuel ratio using the stored regression transfer function, and controls the amount of fuel injection of the engine using the corrected air-fuel ratio.

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