JP2008151004A - Fuel moisture content detecting method and heater current-carrying starting timing setting method using this method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem of increasing cost, since a sensor is conventionally incorporated only for detecting the alcohol concentration in fuel, when detecting the fuel moisture content. <P>SOLUTION: This fuel moisture content detecting device has a cylinder internal pressure sensor 20 detecting pressure P in a combustion chamber 14, a fuel injection quantity setting part 39 setting a supply quantity of the fuel to the combustion chamber 14, a crank angle sensor 37 detecting a crank angle phase, a combustion chamber volume calculating part 41 calculating the volume V of the combustion chamber 14 when detecting the pressure P in the combustion chamber 14 by the cylinder internal pressure sensor 20, a low calorific value index calculating part 43 calculating a control parameter on a calorific value of the fuel from the supply quantity of the fuel, the pressure P and the volume V of the combustion chamber 14, and a fuel moisture content calculating part 44 calculating the moisture content W of use fuel from a rate of a value of the calculated control parameter to a value of a control parameter in the preset predetermined moisture content. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for detecting the moisture content of fuel supplied to an engine, and a method for setting an energization start timing for a heater for heating a sensor disposed in an exhaust passage of the engine.

  In recent years, ethanol fuel has attracted attention due to resource depletion and environmental concerns. This ethanol fuel is an inexpensive and realistic environmental conservation fuel that can be produced relatively easily from cellulose, corn, natural gas, etc., and the development of FFV (Flex Fuel Vehicle) corresponding to such fuel has been developed. I'm in a hurry.

On the other hand, since ethanol has a hygroscopic property as well known, the quality is likely to vary depending on the production area and manufacturing factory, and even if it is a fuel of E100 (ethanol 100%), it is caused by the mixing of moisture in the production process. It is inevitable to have a certain moisture content. Normally, the higher the moisture content in the fuel, the greater the amount of moisture contained in the exhaust gas. Therefore, in O ₂ sensors and A / F sensors using ceramics such as zirconia that are vulnerable to thermal shock, It is necessary to pay attention to such accidents. That is, since the temperature at which the detection elements of these sensors are activated is 600 ° C. or higher, a heater for heating the detection elements is incorporated in these sensors in order to activate the sensors quickly when the engine is started. Yes. When the engine starts cold, especially in cold regions, when water droplets condensed on the inner wall of the exhaust pipe touch the detection element of the sensor being heated by the heater, a crack is generated in the detection element due to thermal shock. There is a possibility of waking up.

  In Patent Document 1, an alcohol concentration sensor is incorporated in the middle of the fuel supply path to detect the alcohol concentration in the fuel, and based on this, the amount of water contained in the exhaust gas is estimated, and a sensor disposed in the exhaust passage A technique for controlling the start of energization of the heater is disclosed. According to this, as the amount of moisture increases, the energization start time is delayed to more reliably evaporate water droplets in the exhaust passage, and it is possible to suppress a sensor damage accident caused by water-cracking of the detection element.

JP 2005-344550 A

  In patent document 1, since the sensor only for detecting the alcohol concentration in fuel is built in, the cost increase for that cannot be avoided.

  A main object of the present invention is to provide a method capable of detecting the moisture content of a fuel without using a dedicated sensor for detecting the properties of the fuel.

  Another object of the present invention is to provide a method for detecting the fuel moisture content in advance of the energization start timing of the heater after the engine is started with respect to a sensor that is arranged in the exhaust passage of the engine and is activated by heating with a heater. It is to provide a method that can be set by using.

  The amount of heat generated in one cycle of engine combustion is completely proportional to the fraction of carbon and hydrogen in the combustion component (CnHmO) of the fuel supplied to the engine. Therefore, for example, the heat generation amount of E95 alcohol fuel containing 5% of water is 5% lower than the heat generation amount when using E100 alcohol fuel when other impurities are not taken into consideration. That is, when the amount of heat generated in the alcohol fuel of E100 is known in advance, the moisture content can be estimated by obtaining the amount of heat generated in the fuel supplied to the engine.

  The present invention has been made in view of such knowledge, and a first mode thereof is a step of detecting the pressure in the combustion chamber of the engine, and the fuel supplied to the engine based on the detected pressure in the combustion chamber. A fuel moisture content detection method comprising the step of estimating a moisture content.

  In the fuel moisture content detection method according to the first aspect of the present invention, the step of estimating the moisture content of the fuel includes the step of estimating the moisture content of the fuel from the detected pressure of the combustion chamber and the volume of the combustion chamber at this time. And a step of calculating a ratio of the calculated value of the control parameter to the value of the control parameter at a predetermined moisture content set in advance. In this case, the method further includes the step of determining whether or not the operating state of the engine is in a steady state, and executing the step of estimating the moisture content of the fuel when it is determined that the operating state of the engine is in the steady state. It is preferable.

  The step of estimating the moisture content of the fuel is a step of calculating a control parameter relating to the heat generation amount of the fuel from the detected pressure of the combustion chamber, the volume of the combustion chamber at this time, and the amount of fuel supplied to the combustion chamber. And a step of calculating a ratio of the value of the calculated control parameter to the value of the control parameter in the case of a predetermined moisture content set in advance.

  The step of detecting the pressure in the combustion chamber includes the step of calculating the maximum pressure in the combustion chamber as an average value in a plurality of combustion cycles, and the step of estimating the moisture content is a maximum in the combustion chamber at a preset predetermined moisture content. The method may include a step of calculating a ratio of the calculated average maximum pressure in the combustion chamber to the pressure. In this case, the method further includes a step of determining whether or not the engine operating state is in a steady state. Here, the step of detecting the maximum pressure in the combustion chamber when the engine operating state is determined to be in a steady state is executed. It is preferable to do.

  In any case, it is effective that the fuel having a predetermined moisture content set in advance is a fuel having a nominal moisture content to be supplied to the engine, and it can be said that it is particularly suitable for alcohol fuel having a high hygroscopic property.

  The second aspect of the present invention estimates the moisture content of the fuel supplied to the engine based on the in-cylinder pressure sensor for detecting the pressure in the combustion chamber of the engine and the pressure in the combustion chamber detected by the in-cylinder pressure sensor. A fuel moisture content detection device comprising a moisture content estimation means.

  The fuel moisture content detection device according to the second aspect of the present invention further includes a crank angle sensor for detecting the crank angle phase of the engine, and the moisture content estimation means is based on the detection signal from the crank angle sensor and is used as the in-cylinder pressure sensor. Combustion chamber volume calculating means for calculating the volume of the combustion chamber at the time when the pressure in the combustion chamber is detected by means of, and the combustion chamber volume calculated by the combustion chamber volume calculating means and the combustion chamber volume detected by the in-cylinder pressure sensor. A parameter calculation means for calculating a control parameter relating to the heat generation amount of the fuel from the pressure, and a fuel used from a ratio of the control parameter value calculated by the parameter calculation means to a control parameter value at a predetermined predetermined moisture content It may have a moisture content calculating means for calculating the moisture content. In this case, the engine further includes an operation state determination unit that determines whether or not the engine operation state is in a steady state. When the operation state determination unit determines that the engine operation state is in a steady state, the moisture content It is preferable to calculate the fuel moisture content by the calculating means.

  The operating state determination means includes a throttle opening sensor that detects the opening of a throttle valve disposed in the middle of the intake passage or an air flow sensor that detects the flow rate of intake air in the intake passage, and this throttle opening sensor / air flow sensor It may be determined whether the engine operating state is in a steady state based on the detection information from the engine and the detection information from the crank angle sensor.

  The fuel supply amount setting means for setting the fuel supply amount to the combustion chamber and a crank angle sensor for detecting the crank angle phase of the engine are further provided, and the moisture content estimation means is based on the detection signal from the crank angle sensor, Combustion chamber volume calculating means for calculating the volume of the combustion chamber when the pressure in the combustion chamber is detected by the in-cylinder pressure sensor, and the fuel supply amount set by the fuel supply amount setting means, and detected by the in-cylinder pressure sensor Parameter calculation means for calculating a control parameter related to the heat generation amount of the fuel from the pressure of the combustion chamber and the volume of the combustion chamber calculated by the combustion chamber volume calculation means, and a parameter for the value of the control parameter at a preset predetermined moisture content A moisture content calculating means for calculating the moisture content of the fuel used from the ratio of the value of the control parameter calculated by the calculating means. Good me.

  The parameter calculation means includes averaging means for calculating the maximum pressure in the combustion chamber as an average value in a plurality of combustion cycles, and the moisture content estimation means is an average for the maximum pressure in the combustion chamber at a preset predetermined moisture content. The moisture content calculating means for calculating the moisture content of the used fuel from the ratio of the average maximum pressure in the combustion chamber calculated by the converting means can be included. In this case, further comprising an operation state determination means for determining whether or not the engine operation state is in a steady state, and when the operation state determination means determination means determines that the engine operation state is in a steady state, It is preferable to calculate the fuel moisture content by the moisture content calculating means.

  In any case, it is effective that the fuel having a predetermined moisture content set in advance is a fuel having a nominal moisture content to be supplied to the engine, and is particularly suitable for alcohol fuel having a high hygroscopic property.

  According to a third aspect of the present invention, there is provided a method for controlling the energization start timing for a heater incorporated in a sensor arranged so as to face an exhaust passage after the engine has been restarted. The method comprises the steps of: estimating the moisture content contained in the fuel by the method; and setting the energization start timing for the heater after the engine is restarted based on the estimated fuel moisture content. is there.

  In the heater energization start timing setting method according to the third aspect of the present invention, it is desirable that the energization start timing for the heater be delayed as the moisture content in the fuel increases.

  According to a fourth aspect of the present invention, there is provided an apparatus for controlling the energization start timing for a heater incorporated in a sensor disposed so as to face an exhaust passage after the restart of the engine, the fuel moisture content detection according to the present invention. And an energization start timing setting means for setting an energization start timing for the heater after the engine is restarted based on the fuel moisture content estimated by the fuel moisture content detection apparatus. .

  According to the fuel moisture content detection method of the first aspect of the present invention, the pressure in the combustion chamber of the engine is detected, and the moisture content of the fuel supplied to the engine is estimated based on the detected pressure in the combustion chamber. Therefore, the moisture content of the fuel can be estimated without using a special sensor such as an alcohol concentration sensor.

  When estimating the moisture content of the fuel, a control parameter relating to the heat generation amount of the fuel is calculated from the detected pressure of the combustion chamber and the volume of the combustion chamber at this time, and the value of the control parameter at a preset predetermined moisture content On the other hand, when the ratio of the calculated control parameter value is calculated, the fuel moisture content can be estimated with higher accuracy. In particular, when it is determined whether or not the engine operating state is in a steady state, and it is determined that the engine operating state is in a steady state, the fuel moisture content is further increased. It can be estimated with high accuracy.

  When estimating the moisture content of the fuel, control parameters relating to the heat generation amount of the fuel are calculated in advance from the detected pressure of the combustion chamber, the volume of the combustion chamber at this time, and the amount of fuel supplied to the combustion chamber. When the ratio of the calculated control parameter value to the control parameter value at the set predetermined moisture content is calculated, the fuel moisture content even if the engine is in a transient operating state such as during acceleration / deceleration Can be estimated.

  When the pressure in the combustion chamber is detected, the maximum pressure in the combustion chamber is calculated as an average value in a plurality of combustion cycles, and when the moisture content is estimated, the maximum pressure in the combustion chamber at a predetermined moisture content set in advance is calculated. When calculating the calculated ratio of the average maximum pressure in the combustion chamber, the fuel moisture content can be estimated extremely simply. In particular, when determining whether or not the engine operating state is in a steady state, and detecting the maximum pressure in the combustion chamber when it is determined that the engine operating state is in a steady state, the fuel moisture content is more accurately detected. Can be estimated.

  According to the fuel moisture content detection device of the second aspect of the present invention, the cylinder pressure sensor for detecting the pressure in the combustion chamber of the engine and the pressure supplied to the engine based on the pressure in the combustion chamber detected by the cylinder pressure sensor. Since the moisture content estimating means for estimating the moisture content of the fuel is provided, the moisture content of the fuel can be estimated without using a special sensor such as an alcohol concentration sensor.

  A crank angle sensor for detecting the crank angle phase of the engine is further provided, and the volume of the combustion chamber at the time when the moisture content estimation means detects the pressure in the combustion chamber by the in-cylinder pressure sensor based on the detection signal from the crank angle sensor. And a parameter calculation for calculating a control parameter relating to the heat generation amount of the fuel from the combustion chamber volume calculated by the combustion chamber volume calculation unit and the pressure in the combustion chamber detected by the in-cylinder pressure sensor. And a moisture content calculating means for calculating the moisture content of the fuel used from the ratio of the value of the control parameter calculated by the parameter calculating means with respect to the value of the control parameter at a predetermined moisture content set in advance. The fuel moisture content can be estimated with higher accuracy. In particular, it further comprises an operating state determining means for determining whether or not the operating state of the engine is in a steady state, and when the operating state determining means determines that the operating state of the engine is in a steady state, the moisture content calculating means When the fuel moisture content is calculated by this, the fuel moisture content can be estimated with higher accuracy.

  The fuel supply amount setting means for setting the fuel supply amount to the combustion chamber and a crank angle sensor for detecting the crank angle phase of the engine are further provided, and the moisture content estimation means is based on the detection signal from the crank angle sensor, Combustion chamber volume calculation means for calculating the volume of the combustion chamber when the pressure in the combustion chamber is detected by the in-cylinder pressure sensor, and the fuel supply amount set by the fuel supply amount setting means and the in-cylinder pressure sensor Parameter calculation means for calculating a control parameter relating to the calorific value of the fuel from the pressure of the combustion chamber and the volume of the combustion chamber calculated by the combustion chamber volume calculation means, and a parameter for the value of the control parameter at a preset predetermined moisture content Moisture content calculating means for calculating the moisture content of the fuel used from the ratio of the value of the control parameter calculated by the calculating means If, even in transient operating conditions, such as during engine acceleration or deceleration can be estimated fuel moisture content.

  The parameter calculating means includes an averaging means for calculating the maximum pressure in the combustion chamber as an average value in a plurality of combustion cycles, and is calculated by the averaging means for the maximum pressure in the combustion chamber at a preset predetermined moisture content. If the moisture content estimating means has a moisture content calculating means for calculating the moisture content of the used fuel from the ratio of the average maximum pressure in the combustion chamber, the fuel moisture content can be estimated very simply. In particular, it further comprises an operating state determining means for determining whether or not the engine operating state is in a steady state, and the moisture content is determined when the operating state determining means determining means determines that the engine operating state is in a steady state. When the fuel moisture content is calculated by the calculating means, the fuel moisture content can be estimated with higher accuracy.

  According to the heater energization start timing setting method of the third aspect of the present invention, the moisture content contained in the fuel is estimated by the fuel moisture content detection method of the present invention, and the engine restart is performed based on the estimated fuel moisture content. Since the start time of energizing the heater is set later, the start time of energizing the heater after starting the engine is set without using a special sensor such as an alcohol concentration sensor, thereby reducing damage caused by water cracking of the sensor. Can be made.

  When setting the energization start timing for the heater, if the heater energization start timing is set to be delayed as the moisture content in the fuel increases, the damage accident due to moisture cracking of the sensor can be reduced more reliably.

  According to the heater energization start timing setting device of the fourth aspect of the present invention, the heater after the engine is restarted based on the fuel moisture content detection device according to the present invention and the fuel moisture content estimated by the fuel moisture content detection device. Energization start time setting means for setting the energization start time for the heater, and without using a special sensor such as an alcohol concentration sensor, the energization start time for the heater after the engine is started is set and the sensor cover is set. Damage accidents due to water cracking can be reduced.

  An embodiment in which the present invention is applied to a spark ignition type internal combustion engine in which an A / F sensor is incorporated in an exhaust passage will be described in detail with reference to FIGS. It should be noted that the present invention is not limited to such an embodiment, and may be applied to other arbitrary techniques belonging to the spirit of the present invention, as necessary, by combining some of these embodiments with each other. it can.

  The concept of the engine system in this embodiment is shown in FIG. 1, and its control block is shown in FIG. The engine 10 in this embodiment is of a type in which an alcohol fuel (anhydrous ethanol) of E100 as fuel is injected into the intake port 12 from the fuel injection valve 11 and ignited by the spark plug 13.

  A valve operating mechanism including an intake valve 17 that opens and closes the intake port 12 and an exhaust valve 18 that opens and closes the exhaust port 15 is incorporated in the cylinder head 16 in which the intake port 12 and the exhaust port 15 facing the combustion chamber 14 are formed. ing. In addition to the previous fuel injection valve 11, the ignition plug 13 that ignites the air-fuel mixture in the combustion chamber 14, and the ignition coil 19 that generates a spark in the ignition plug 13, a cylinder for detecting the pressure in the combustion chamber 14 The internal pressure sensor 20 is also mounted on the cylinder head 16. A signal detected by the in-cylinder pressure sensor 20 is output to the ECU 21.

  At the upstream end side of the intake pipe 23 connected to the cylinder head 16 so as to communicate with the intake port 12 and defining the intake passage 22 together with the intake port 12, dust and the like contained in the atmosphere are removed to remove the intake passage 22. An air cleaner 24 is provided for guiding the air. A throttle valve 25 that adjusts the opening degree of the intake passage 22 based on the amount of depression of an accelerator pedal (not shown) that is operated by the driver is incorporated in the portion of the intake pipe 23 that is located downstream of the air cleaner 24. ing. The throttle valve 25 is provided with a throttle opening degree sensor 26 for detecting the opening degree, and the detection information is output to the ECU 21. In this embodiment, the accelerator pedal and the throttle valve 25 are mechanically connected. However, the depression operation of the accelerator pedal and the opening / closing operation of the throttle valve 25 are separated, and the opening / closing operation of the throttle valve 25 is performed using an actuator. It may be one that can be electrically controlled.

  A surge tank 27 is formed in the middle of the intake pipe 23 between the throttle valve 25 and the air cleaner 24, and flows in the intake passage 22 in the middle of the intake pipe 23 between the surge tank 27 and the air cleaner 24. An air flow meter 28 that detects the intake air flow rate and outputs it to the ECU 21 is attached. The attachment position of the air flow meter 28 in the intake pipe 23 may be upstream from the attachment position of the throttle valve 25, and is not limited to the position shown in FIG.

  In the middle of the exhaust pipe 30 connected to the cylinder head 16 so as to communicate with the exhaust port 15 and defining the exhaust passage 29 together with the exhaust port 15, harmful substances generated by combustion of the air-fuel mixture in the combustion chamber 14 are present. A three-way catalyst 31 for detoxification is incorporated. It is also effective to incorporate a plurality of three-way catalysts 31 in series along the exhaust passage 29. In the middle of the exhaust pipe 30 between the three-way catalyst 31 and the exhaust port 15, an A / F sensor 32 that detects the air-fuel ratio in the exhaust gas flowing in the exhaust passage 29 and outputs it to the ECU 21 is provided. . Since the A / F sensor 32 in this embodiment uses zirconia as a detection element, a heater 32a that promotes activation thereof is incorporated in the A / F sensor 32. The heater 32a receives electric power from the ECU 21 and quickly raises the detection element to its activation temperature.

  Therefore, the intake air supplied from the intake pipe 23 into the combustion chamber 14 through the air cleaner 24 forms an air-fuel mixture with the fuel injected from the fuel injection valve 11 into the intake port 12 and is ignited by the spark of the spark plug 13. The exhaust gas thus generated is exhausted through the three-way catalyst 31 from the exhaust pipe 30 to the atmosphere.

  A crank angle sensor 37 that detects the rotational phase of the crankshaft 36 to which the piston 33 is coupled via the connecting rod 35, that is, the crank angle, and outputs the detected crank angle to the ECU 21 is attached to the cylinder block 34 in which the piston 33 reciprocates. It has been.

  The ECU 21 operates the engine 10 smoothly according to a preset program based on the signal from the ignition key switch 38 and the detection information from the sensors 20, 26, 32, 37 and the air flow meter 28 described above. Further, the operation of the fuel injection valve 11, the ignition coil 19, the heater 32a of the A / F sensor 32, and the like are controlled. Further, the fuel injection amount from the fuel injection valve 11 is set in the ECU 21 so as to be a predetermined ratio with respect to the intake amount corresponding to the opening degree of the throttle valve 25 based on the depression amount of an accelerator pedal (not shown). It is set by the fuel injection amount setting unit 39 as the fuel supply amount setting means incorporated in the present invention. Further, the energization timing for the ignition coil 19 is set by the ignition timing setting unit 40 of the ECU 21 based on information from the throttle opening sensor 26, the crank angle sensor 37, and the like.

  The ECU 21 in the present embodiment also has a function of estimating the moisture content in the fuel and setting the energization start timing for the heater 32a based on this. Therefore, in addition to the previous fuel injection amount setting unit 39, the combustion chamber volume calculation unit 41, the heat generation amount index calculation unit 42, the lower heating value index calculation unit 43 as the parameter calculation means in the present invention, the fuel It has a moisture content calculation unit 44, a comparison unit 45, an energization start time calculation unit 46, and a storage unit 47.

  The combustion chamber volume calculation unit 41 calculates the volume V of the combustion chamber 14 at the time when the pressure in the combustion chamber 14 is detected by the in-cylinder pressure sensor 20 based on information from the crank angle sensor 37, and this is the heat generation amount. The data is output to the index calculation unit 42. The volume V of the combustion chamber 14 at the time when the pressure P in the combustion chamber 14 is detected can be naturally obtained from the crank angle phase detected by the crank angle sensor 37, and the combustion chamber volume calculation unit 41 in the present embodiment is It has this as mapped data.

The heat generation amount index calculating unit 42 is a product PV ^κ of the pressure in the combustion chamber 14, that is, the cylinder pressure P and the value obtained by raising the volume V of the combustion chamber 14 at the time of detection of the cylinder pressure P by a predetermined index ^κ. Is calculated as a control parameter related to the instantaneous heat generation amount h when the in-cylinder pressure P is detected, that is, as a heat generation amount index. The product of the in-cylinder pressure P and the value V ^{κ obtained} by raising the volume V of the combustion chamber 14 to the exponent κ at the time of detection of the in-cylinder pressure P (hereinafter referred to as a heat generation amount parameter) PV ^κ and the instantaneous heat generation amount The fact that h has a correlation, that is, h∽PV ^κ has been described in detail in JP-A-2005-36754 and is well known. The heat generation amount parameter PV ^κ calculated by the heat generation amount index calculation unit 42 is output to the lower heating value index calculation unit 43.

The lower heating value index calculation unit 43 supplies the amount of fuel per cycle to one cylinder in which the heat generation amount parameter PV ^κ is set by the fuel injection amount setting unit 39 (hereinafter referred to as a set injection amount). The value divided by τ is calculated as a control parameter related to the lower heating value Q that is the heating value of the true fuel without considering the latent heat of water contained in the fuel, that is, the lower heating value index h / τ. The lower heating value Q is obtained by dividing the instantaneous heat generation amount h by the set injection amount τ, and can be expressed as Q∽PV ^κ / τ from the relationship of h∽PV ^κ described above.

The lower heating value Q tends to decrease as the fuel moisture content W increases, resulting in a downward-sloping graph as shown in FIG. The region where the fuel water content W is _RH or more predetermined value W is impossible in practice area, in a range fuel moisture content W of 0 to w _RH%, the fuel moisture content W and the lower heating value Q Will be understood to be proportional. Therefore, by obtaining the low heat value Q _E100 in the fuel water content W of 0%, that is, the fuel of E100 in advance, the value of the low heat value index h / τ calculated by the low heat value index calculation unit 43 is obtained. The corresponding fuel moisture content W can be obtained from W = (Q−Q _E100 ) / α using the relationship of Q = αW + Q _E100 (where α <0) using the proportional relationship. The fuel moisture content calculation unit 44 stores the graph shown in FIG. 3 as a map, and estimates the fuel moisture content W from the lower heating value index h / τ calculated by the lower heating value index calculation unit 43. Is output to the comparison unit 45.

When the operating state of the engine 10 is in a steady state, that is, when the engine speed and the throttle valve opening are within a substantially constant range, the heat generation amount index PV is calculated without calculating the lower heating value index h / τ described above. It is also possible to estimate the fuel moisture content W from ^κ . Specifically, the heat generation amount index PV ^κ when the operating state of the engine 10 is in a steady state is calculated a plurality of times, and the average value PV ^κ _m is obtained as a control parameter. From the ratio of the average value PV ^κ _m of the heat generation amount index PV ^{κ to} the heat generation amount H _E100 , the corresponding fuel moisture content W can be calculated by W = 1− (PV ^κ _m / H _E100 ).

However, by calculating the lower heating value index h / τ based on the heat generation amount index PV ^κ and the set fuel injection amount τ as in the present embodiment, the operating state of the engine 10 is not a steady state but is accelerated / decelerated. Even in a transient state such as time, there is an advantage that the fuel moisture content W can be accurately calculated.

The comparison unit 45 determines whether or not the fuel moisture content W calculated by the fuel moisture content calculation unit 44 is less than a predetermined value _WRH set in advance, and determines that the fuel moisture content W is less than the predetermined value _WRH Then, the fuel moisture content W calculated by the fuel moisture content calculator 44 is output to the energization start timing calculator 46. However, when the fuel moisture content W is _RH or more predetermined value W, since the fuel moisture content W calculated by the fuel moisture content calculator 44 is impossible value, the energization start timing calculation unit to cancel this value No output to 46.

The energization start timing calculation unit 46 calculates the energization start timing T for the heater 32a of the A / F sensor 32 after restarting the engine 10 based on the fuel moisture content W output from the comparison unit 45, and stores this. To the unit 47. The energization start time T tends to be delayed as the fuel moisture content W increases, and has a relationship as shown in FIG. The energization start time calculation unit 46 stores the graph shown in FIG. 4 as a map, and such a map is empirically obtained through experiments and the like. The region where the fuel moisture content W is less than or equal to the predetermined value _WRL set in advance is a region where the effect of delaying the energization start timing T for the heater 32a of the A / F sensor 32 from the time when the engine 10 is started is not recognized. is there. In other words, even if energization of the heater 32a of the A / F sensor 32 is performed simultaneously with the start of the engine 10, the accident occurrence probability of water cracking does not change, so when the fuel moisture content W is equal to or less than the predetermined value _WRL , It is effective to immediately conduct the combustion feedback control by energizing the heater 32a of the A / F sensor 32 simultaneously with the start of the engine 10.

  The storage unit 47 stores the energization start timing T calculated by the energization start timing calculation unit 46 immediately before the engine 10 is stopped, and energizes the heater 32a of the A / F sensor 32 when the engine 10 is restarted. The start time is set to the energization start time T stored here.

  Note that the ECU 21 determines whether the engine 10 is stopped when the ignition key switch 38 is off or the engine 10 is stopped if the engine speed is lower than a predetermined value lower than the idle speed for a predetermined time. It is judged. The engine 10 is determined to be started when the ignition key switch 38 is on and the engine speed is equal to or higher than the idle speed for a predetermined time.

A procedure for setting the energization start timing T for the heater 32a of the A / F sensor 32 according to the present embodiment will be described with reference to FIG. First, in step S11, the heat generation amount index PV ^κ is calculated by the heat generation amount index calculation unit 42, and in step S12, the lower heating value index h / τ is calculated by the lower heating value index calculation unit 43. In step S13, the fuel moisture content W is calculated by the fuel moisture content calculator 44. Next, it is determined at comparator unit 45 or less or not than the set value W _RH improbable fuel moisture content W calculated in step S14.

If it is determined in step S14 that the fuel moisture content W is equal to or greater than the set value _WRH , that is, the calculated fuel moisture content W is a value that is not actually possible, an error may be considered. Returning to the step, the fuel moisture content W is calculated again. On the other hand, when the comparison unit 45 determines in step S14 that the fuel moisture content W is less than the set value _WRH , the process proceeds to step S15 and the energization start timing T is calculated by the energization start timing calculation unit 46. After the calculation, it is determined in step S16 whether or not the engine 10 is stopped.

  Here, when it is determined that the engine 10 is not stopped, the process returns to the step of S11 and the energization start time T is calculated again. If the ECU 21 determines that the engine 10 is stopped in step S16, the process proceeds to step S17 and the latest energization start time T calculated in step S15 is stored in the storage unit 47. To do.

  Thus, the calculation of the energization start time T is always repeated until the engine 10 is stopped, and the latest energization start time T is stored and updated in the storage unit 47.

  Energization of the heater 32a of the A / F sensor 32 after the engine 10 is started is performed according to the procedure shown in FIG. That is, it is determined in step S21 whether or not the engine 10 has been started. If the engine 10 has not been started, the process ends without doing anything. If the ECU 21 determines that the engine 10 has been started in step S21, the timer starts counting up in step S22 and is stored in the storage unit 47 in step S23. The energization start time T is read. In step S24, it is determined whether or not the timer count value TC is equal to or greater than the read energization start time T, and the timer counts up until the timer count value TC is equal to or greater than the energization start timing T. to continue. Then, when the count value TC of the timer becomes equal to or greater than the energization start timing T, the process proceeds to step S25, and energization of the heater 32a of the A / F sensor 32 is performed.

  As described above, even if the water droplets condensed in the exhaust passage 29 are vaporized as the high-temperature exhaust gas flows and the water droplets adhere to the element of the A / F sensor 32 while the timer is counting up. This is surely vaporized. For this reason, even if energization to the heater 32a is started and the element is raised to the activation temperature, accidents such as water cracking can be prevented more reliably. Further, it is possible to start the feedback control using the A / F sensor 32 after the engine 10 is started without unnecessarily delaying the feedback control.

Incidentally, the maximum value P _X of cylinder pressure, since the difference by property of the fuel, it is possible to predict the water content W of the fuel from the maximum value P _X of the cylinder pressure. 7, E100 (solid line) and E95 shows the change of the in-cylinder pressure P corresponding to the crank angle phase in the case of using the fuel (dashed line), maximum value P _X of the higher fuel moisture content W cylinder pressure Will be recognized as a drop. FIG. 8 shows a control block of another embodiment of the present invention based on such a principle, and FIG. 9 shows the control procedure. Elements having the same functions as those of the previous embodiment are denoted by the same reference numerals. Therefore, duplicate explanations are omitted.

  In this embodiment, the ECU 21 includes a steady state determination unit 48, a maximum pressure, in addition to the fuel injection amount setting unit 39, the fuel moisture content calculation unit 44, the comparison unit 45, the energization start timing calculation unit 46, and the storage unit 47. A detection unit 49, an average maximum pressure calculation unit 50, and a counter 51 are included.

  The steady state determination unit 48 determines whether or not the operating state of the engine 10 is in a steady state based on detection signals from the throttle valve opening sensor 26 and the crank angle sensor 37. Specifically, if the change rate of the throttle valve opening and the change rate of the engine speed are within a predetermined range over a predetermined period, it is determined that the operating state of the engine 10 is in a steady state. The determination result is output to the maximum pressure detection unit 49 and the counter 51.

Maximum pressure detecting unit 49 based on the detection signal from the cylinder pressure sensor 20, is calculated this by calculating the maximum pressure P _X for every one cycle of the average maximum pressure calculating unit 50.

The average maximum pressure calculation unit 50 functioning as a parameter calculation unit in the present invention together with the above-described maximum pressure detection unit 49 is an average value P _Xm of the maximum pressure P _X of the in-cylinder pressure for n cycles output from the maximum pressure detection unit 49. Is output to the fuel moisture content calculation unit 44.

Counter 51 counts the maximum number of times of detecting the pressure P _X of the in-cylinder pressure at the maximum pressure detecting unit 49.

The fuel moisture content calculation unit 44 as the moisture content estimation means in the present invention is an average maximum pressure calculation unit 50 for the maximum pressure P _XE100 in the combustion chamber 14 when a fuel having a preset moisture content of 0% is used. Based on the ratio of the average maximum pressure P _Xm in the combustion chamber 14 calculated in step 1, the water content W of the fuel used is calculated from W = 1− (P _Xm / P _E100 ).

The procedure for setting the energization start timing T for the heater 32a of the A / F sensor 32 according to this embodiment will be described with reference to FIG. First, in step S31, the steady state determination unit 48 determines whether the operating state of the engine 10 is in a steady state, and determines that the engine 10 is not in a steady state, that is, is in a transient state such as acceleration / deceleration. when the can not calculate an accurate fuel moisture content W, and resets the count value C _n of the transition to the counter 51 to step S32 to 0 to end the flow.

On the other hand, when it is determined that the operating state of the engine 10 is in a steady state, the process proceeds to step S33 and the counter 51 is counted up. In step S34, the maximum pressure detection unit 49 is detected from the in-cylinder pressure sensor 20. detecting a maximum pressure P _X based on the information, and outputs it to the average maximum pressure calculating unit 50. Then, although the count value C _n of the counter 51 at S35 in step determines whether has reached a predetermined value CR, initially returns to small since S31 in step than a predetermined value CR, the detection of maximum pressure P _X Data is accumulated in the average maximum pressure calculation unit 50. Thus, if the count value C _n of the counter 51 at S35 in step is determined to have reached the predetermined value CR, the average maximum pressure P at an average maximum pressure calculation unit 50 proceeds to S36 in step _Xm is calculated and output to the fuel moisture content calculation unit 44. Then, reset the count value C _n of the counter 51 to zero at step S37, it calculates the fuel water content W in the fuel moisture content calculator 44 in addition S38 in step.

Thereafter, the calculated fuel moisture content W is determined in step S39 whether or not larger than a predetermined value W _RL, fuel moisture content W is equal to or less than the predetermined value W _RL, fuel moisture content that is calculated When the comparison unit 45 determines that W is in an area that is not affected by the delay of the energization start timing T, the energization start timing T is set to 0 in step S40, and the process proceeds to step S41. It is determined whether or not the engine 10 is stopped. Further, when the fuel moisture content W determines the comparison unit 45 is greater than the predetermined value W _RL at S39 in step calculates the migrated energization start timing calculating section 46 is the energization start timing is T in step S42 After that, the ECU 21 determines whether or not the engine 10 is stopped by moving to the previous step of S41.

  If it is determined in step S41 that the engine 10 is not stopped, the process returns to step S31 and the energization start timing T is recalculated until it is determined that the engine 10 is stopped. If it is determined in step S41 that the engine 10 is stopped, the process proceeds to step S43, and the latest energization start timing T calculated by the energization start timing calculation unit 46 is stored in the storage unit 47. Let

  In this way, the calculation of the energization start time T is always repeated until the engine 10 is stopped, and the latest energization start time T is stored in the storage unit 47.

In the embodiment described above, the fuel moisture content W when the alcohol fuel of E100 is used is calculated. However, even when a mixed fuel of gasoline and alcohol is used, the control parameter value is read in the comparison unit 45 in advance as long as the mixing ratio serving as a reference of alcohol to gasoline is known in advance. Can be applied. In addition to the A / F sensor 32 described above, the present invention also applies to an engine system in which an O ₂ sensor or NO _X sensor that may cause an accident due to water cracking due to energization of the heater 32a is incorporated in the exhaust passage 29. Needless to say, can be applied to a compression ignition internal combustion engine as well.

  As described above, the present invention should be construed only from the matters described in the scope of the claims, and in the above-described embodiments, the matters described in all the changes and modifications included in the concept of the present invention are described. Other than possible. That is, all matters in the above-described embodiment are not intended to limit the present invention, and include any configuration not directly related to the present invention. To get.

1 is a conceptual diagram of an embodiment in which the present invention is applied to a spark ignition internal combustion engine. FIG. 2 is a control block diagram in the embodiment shown in FIG. 1. It is a graph showing the relationship between a fuel moisture content and a low calorific value index. It is a graph showing the relationship between a fuel moisture content and the energization start time with respect to a heater. It is a flowchart showing the setting procedure of the energization start time with respect to the heater in embodiment shown in FIG. It is a flowchart showing the procedure of electricity supply operation with respect to a heater. 4 is a graph schematically showing a relationship between an engine crank angle phase and an in-cylinder pressure. It is a control block diagram in other embodiments of the present invention. It is a flowchart showing the setting procedure of the energization start time with respect to the heater in embodiment shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Engine 11 Fuel injection valve 12 Intake port 13 Spark plug 14 Combustion chamber 15 Exhaust port 16 Cylinder head 17 Intake valve 18 Exhaust valve 19 Ignition coil 20 In-cylinder pressure sensor 21 ECU
DESCRIPTION OF SYMBOLS 22 Intake passage 23 Intake pipe 24 Air cleaner 25 Throttle valve 26 Throttle opening sensor 27 Surge tank 28 Air flow meter 29 Exhaust passage 30 Exhaust pipe 31 Three-way catalyst 32 A / F sensor 32a Heater 33 Piston 34 Cylinder block 35 Connecting rod 36 Crankshaft 37 Crank angle sensor 38 Ignition key switch 39 Fuel injection amount setting unit 40 Ignition timing setting unit 41 Combustion chamber volume calculation unit 42 Heat generation amount index calculation unit 43 Low heating value index calculation unit 44 Fuel moisture content calculation unit 45 Comparison unit 46 Energization Start time calculation unit 47 Storage unit 48 Steady state determination unit 49 Maximum pressure detection unit 50 Average maximum pressure calculation unit 51 Counter P Pressure in combustion chamber (in-cylinder pressure)
P _X Maximum in-cylinder pressure P _Xm Average maximum in-cylinder pressure V Volume of combustion chamber at detection of in-cylinder pressure h Instantaneous heat generation amount at detection of in-cylinder pressure Q Low heating value of fuel W Fuel moisture content T Heating start timing to heater κ Exponent τ Set injection amount

Claims (14)

Detecting the pressure in the combustion chamber of the engine;
Estimating the moisture content of the fuel supplied to the engine based on the detected pressure in the combustion chamber. The step of estimating the moisture content of the fuel is
Calculating a control parameter relating to the heat generation amount of the fuel from the detected pressure of the combustion chamber and the volume of the combustion chamber at this time;
The fuel moisture content detection method according to claim 1, further comprising: calculating a ratio of the calculated control parameter value to a control parameter value at a predetermined moisture content set in advance.   The method further comprises the step of determining whether or not the engine operating state is in a steady state, wherein the step of estimating the moisture content of the fuel is executed when it is determined that the engine operating state is in a steady state. The fuel moisture content detection method according to claim 2, wherein: The step of estimating the moisture content of the fuel is
Calculating a control parameter relating to the heat generation amount of the fuel from the detected pressure of the combustion chamber, the volume of the combustion chamber at this time, and the supply amount of fuel set to the combustion chamber;
The fuel moisture content detection method according to claim 1, further comprising: calculating a ratio of the calculated control parameter value to a control parameter value at a predetermined moisture content set in advance. Detecting the pressure in the combustion chamber includes calculating the maximum pressure in the combustion chamber as an average value in a plurality of combustion cycles;
The step of estimating the moisture content includes a step of calculating a ratio of the calculated average maximum pressure in the combustion chamber to the maximum pressure in the combustion chamber at a predetermined moisture content set in advance. The fuel moisture content detection method as described.   The method further includes the step of determining whether or not the operating state of the engine is in a steady state, wherein the step of detecting the maximum pressure in the combustion chamber is executed when it is determined that the operating state of the engine is in the steady state. The fuel moisture content detection method according to claim 5. An in-cylinder pressure sensor for detecting the pressure in the combustion chamber of the engine;
A fuel moisture content detecting device comprising: a moisture content estimating means for estimating the moisture content of the fuel supplied to the engine based on the pressure in the combustion chamber detected by the in-cylinder pressure sensor. A crank angle sensor for detecting a crank angle phase of the engine is further provided, and the moisture content estimation means is based on a detection signal from the crank angle sensor, and the combustion chamber at the time when the pressure in the combustion chamber is detected by the in-cylinder pressure sensor. Combustion chamber volume calculation means for calculating the volume of
Parameter calculation means for calculating a control parameter relating to the heat generation amount of fuel from the volume of the combustion chamber calculated by the combustion chamber volume calculation means and the pressure in the combustion chamber detected by the in-cylinder pressure sensor;
A moisture content calculating means for calculating the moisture content of the fuel used from the ratio of the value of the control parameter calculated by the parameter calculating means with respect to the value of the control parameter at a predetermined moisture content set in advance. The fuel moisture content detection device according to claim 7.   It further comprises an operating state determining means for determining whether or not the operating state of the engine is in a steady state, and when the operating state determining means determines that the operating state of the engine is in a steady state, the moisture content calculating means 9. The fuel moisture content detection device according to claim 8, wherein the fuel moisture content is calculated by the following. Fuel supply amount setting means for setting the fuel supply amount to the combustion chamber;
A crank angle sensor for detecting a crank angle phase of the engine; and
Combustion chamber volume calculation means for calculating the volume of the combustion chamber at the time when the pressure in the combustion chamber is detected by the in-cylinder pressure sensor based on a detection signal from the crank angle sensor;
Control relating to the amount of fuel heat generated from the fuel supply amount set by the fuel supply amount setting means, the pressure of the combustion chamber detected by the cylinder pressure sensor, and the volume of the combustion chamber calculated by the combustion chamber volume calculation means Parameter calculating means for calculating the parameters;
A moisture content calculating means for calculating the moisture content of the fuel used from the ratio of the control parameter value calculated by the parameter calculating means with respect to the control parameter value at a predetermined moisture content set in advance. The fuel moisture content detection device according to claim 7. The parameter calculation means includes averaging means for calculating the maximum pressure in the combustion chamber as an average value in a plurality of combustion cycles,
The moisture content estimating means calculates the moisture content of the fuel used from the ratio of the average maximum pressure in the combustion chamber calculated by the averaging means to the maximum pressure in the combustion chamber at a predetermined predetermined moisture content. The fuel moisture content detection device according to claim 7, further comprising a rate calculation unit.   Further comprising an operating state determining means for determining whether or not the engine operating state is in a steady state, and when the operating state determining means determining means determines that the engine operating state is in a steady state, the moisture content 12. The fuel moisture content detection device according to claim 11, wherein the fuel moisture content is calculated by a calculation means. A method for controlling energization start timing for a heater incorporated in a sensor arranged to face an exhaust passage after restarting an engine,
Estimating the moisture content contained in the fuel by the fuel moisture content detection method according to any one of claims 1 to 6;
A heater energization start timing setting method comprising: a step of setting an energization start timing for the heater after engine restart based on the estimated fuel moisture content. An apparatus for controlling energization start timing for a heater built in a sensor arranged to face an exhaust passage after restarting the engine,
A fuel moisture content detection device according to any one of claims 7 to 12,
A heater energization start timing setting device comprising: an energization start timing setting means for setting an energization start timing for the heater after restarting the engine based on the fuel moisture content estimated by the fuel moisture content detection device .

Images