JP4052521B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to a control device for an internal combustion engine that can use a fuel containing alcohol as a fuel for the internal combustion engine.

  As fuel for internal combustion engines mounted on vehicles, there are alcohols such as ethanol and methanol, or mixed fuels in which alcohol and gasoline are mixed. Alcohol fuels containing these alcohols are gasoline Compared with, the volatility at low temperature is low (that is, the combustibility is poor), and when alcohol fuel is used, the startability at low temperature and the drivability after starting tend to deteriorate.

  As a countermeasure against this, as described in Patent Document 1 (Japanese Patent Laid-Open No. 58-48737), an auxiliary having higher volatility than the main fuel is provided separately from the main fuel injection device that supplies alcohol fuel as the main fuel. An auxiliary fuel supply device for supplying fuel (for example, gasoline) is provided so that highly volatile auxiliary fuel is supplied in addition to the main fuel when the cooling water temperature detected by the cooling water temperature sensor is below a predetermined temperature. There is what I did. Further, taking into consideration that the alcohol fuel has lower volatility as the alcohol concentration becomes higher, the alcohol of the main fuel detected by the alcohol concentration sensor in the low temperature range where the cooling water temperature detected by the cooling water temperature sensor is lower than a predetermined temperature. In some cases, auxiliary fuel is supplied when the concentration is in a high concentration region of a predetermined concentration or more.

  In addition, since the theoretical air-fuel ratio of alcohol fuel (for example, 8.9 in the case of 100% ethanol) is smaller than the theoretical air-fuel ratio of gasoline (for example, 14.7), under the same conditions as gasoline when alcohol fuel is used. When the fuel injection control is executed, it is inevitable that the fuel injection amount is insufficient and exhaust emission and drivability deteriorate.

As a countermeasure against this, as described in Patent Document 2 (Japanese Patent Publication No. 64-11811), there is one in which the fuel injection amount is corrected to be increased according to the alcohol concentration of the fuel detected by the alcohol concentration sensor. . Furthermore, taking into account that the volatility of the alcohol fuel decreases at lower temperatures, the fuel injection amount is increased and corrected according to the cooling water temperature detected by the cooling water temperature sensor and the alcohol concentration of the fuel detected by the alcohol concentration sensor. There is also something like that.
JP-A-58-48737 (first page to second page, etc.) Japanese Examined Patent Publication No. 64-11811 (first page, etc.)

  As described above, in the auxiliary fuel supply control in which the auxiliary fuel is supplied when the cooling water temperature detected by the cooling water temperature sensor is in the low temperature region and the alcohol concentration of the main fuel detected by the alcohol concentration sensor is in the high concentration region, If the standard cooling water temperature after warming up (for example, 80 ° C.) is used as substitute information for the cooling water temperature as a fail-safe when the water temperature sensor is abnormal, the actual cooling water temperature is in the low temperature region and the alcohol concentration of the main fuel is high. In the concentration range (that is, when the volatility of the main fuel cannot be secured sufficiently), the standard cooling water temperature after warm-up, which is substitute information for the cooling water temperature, does not fall within the low temperature region, so supplementary fuel will not be supplied. Therefore, startability at low temperatures and drivability immediately after start-up may be deteriorated.

  In fuel injection control that increases the fuel injection amount according to the cooling water temperature detected by the cooling water temperature sensor and the alcohol concentration of the fuel detected by the alcohol concentration sensor, warm-up is performed as a fail-safe when the cooling water temperature sensor is abnormal. If the later standard cooling water temperature (for example, 80 ° C.) is used as substitute information for the cooling water temperature, when the actual cooling water temperature is in the low temperature region and the alcohol concentration of the main fuel is in the high concentration region (that is, volatilization of the main fuel). Because the fuel injection amount increase coefficient is set using the standard cooling water temperature after warm-up, which is substitute information for the cooling water temperature, when there is insufficient fuel increase correction amount. Startability and drivability immediately after startup may be deteriorated.

  The present invention has been made in consideration of these circumstances. Accordingly, the object of the present invention is to improve startability and drivability when the coolant temperature sensor is abnormal in a system that can use alcohol-containing fuel. An object of the present invention is to provide a control device for an internal combustion engine.

  In order to achieve the above object, the invention according to claim 1 is applied to a system capable of supplying a main fuel containing alcohol as a fuel for an internal combustion engine and an auxiliary fuel having higher volatility than the main fuel. In the control device for an internal combustion engine that controls the supply of auxiliary fuel based on the cooling water temperature detected by the water temperature sensor and the alcohol concentration of the main fuel detected or estimated by the alcohol concentration acquisition means, when the cooling water temperature sensor is abnormal, The auxiliary fuel is supplied when the alcohol concentration of the main fuel is equal to or higher than a predetermined auxiliary fuel supply determination value.

  In this configuration, if the cooling water temperature sensor is abnormal, the auxiliary fuel can be used in the entire temperature region from the low temperature region to the high temperature region of the cooling water temperature if the alcohol concentration of the main fuel is a high concentration region that is equal to or higher than the auxiliary fuel supply determination value. Fuel supply will be implemented. As a result, when the actual cooling water temperature is in the low temperature region and the alcohol concentration of the main fuel is in the high concentration region (that is, when the volatility of the main fuel cannot be secured sufficiently), the auxiliary fuel can be reliably supplied. It is possible to improve the startability at a low temperature when the cooling water temperature sensor is abnormal and the drivability immediately after the start. Moreover, when the alcohol concentration of the main fuel is lower than the auxiliary fuel supply determination value, it can be determined that the alcohol concentration is sufficient to ensure the volatility of the main fuel, and the auxiliary fuel is not supplied. , Excessive use of auxiliary fuel can be prevented.

  In this case, when the cooling water temperature sensor is abnormal as in claim 2, the auxiliary fuel is supplied when the internal combustion engine is in an inoperative state and the alcohol concentration of the main fuel is equal to or higher than the auxiliary fuel supply determination value. You may do it. In this way, when the cooling water temperature sensor is abnormal, the auxiliary fuel is supplied only when the internal combustion engine is in a start-disabled state and the alcohol concentration of the main fuel is equal to or higher than the auxiliary fuel supply determination value. When it is possible to start the engine, it can be determined that the volatility of the main fuel can be sufficiently secured even if the alcohol concentration of the main fuel is equal to or higher than the auxiliary fuel supply determination value. Consumption can be reduced.

  Further, the auxiliary fuel supply determination value may be changed according to at least one of the intake air temperature and the fuel temperature of the internal combustion engine. In other words, if the auxiliary fuel supply determination value is changed according to the intake air temperature or fuel temperature, which is the temperature information of the internal combustion engine, the volatility of the main fuel changes according to the temperature of the internal combustion engine, and the auxiliary fuel needs to be supplied. The auxiliary fuel supply determination value can be changed to an appropriate value in response to the change in the alcohol concentration.

  Further, since the coolant temperature immediately before the previous stop of the internal combustion engine and the stop time from the previous stop to the current start are also the temperature information of the internal combustion engine, the cooling immediately before the previous stop of the internal combustion engine as in claim 4. The auxiliary fuel supply determination value may be changed according to the water temperature and the stop time from the previous stop to the current start. Even in this case, the auxiliary fuel supply determination value is set to an appropriate value in response to the change in the alcohol concentration at which the auxiliary fuel needs to be supplied due to the change in the volatility of the main fuel depending on the temperature of the internal combustion engine. Can be changed.

  Hereinafter, the best mode for carrying out the present invention will be described using two Examples 1 and 2.

A first embodiment of the present invention will be described with reference to FIGS.
First, a schematic configuration of the entire engine control system will be described with reference to FIG. An air cleaner 13 is provided at the most upstream portion of the intake pipe 12 of the engine 11 that is an internal combustion engine, and an air flow meter 14 that detects the intake air amount is provided downstream of the air cleaner 13. A throttle valve 16 whose opening is adjusted by a motor 15 and a throttle opening sensor 17 for detecting the opening (throttle opening) of the throttle valve 16 are provided on the downstream side of the air flow meter 14.

  Further, a surge tank 18 is provided on the downstream side of the throttle valve 16, and an injection nozzle 19 for injecting auxiliary fuel described later is attached to the surge tank 18. The surge tank 18 is provided with an intake manifold 20 that introduces air into each cylinder of the engine 11, and a fuel injection valve 21 that injects main fuel, which will be described later, in the vicinity of the intake port of the intake manifold 20 of each cylinder. It is attached. An ignition plug 22 is attached to the cylinder head of the engine 11 for each cylinder, and the air-fuel mixture in the cylinder is ignited by spark discharge of each ignition plug 22.

  On the other hand, the exhaust pipe 23 of the engine 11 is provided with an exhaust gas sensor 24 (air-fuel ratio sensor, oxygen sensor, etc.) for detecting the air-fuel ratio or rich / lean of the exhaust gas. A catalyst 25 such as a three-way catalyst for purifying gas is provided.

  A cooling water temperature sensor 26 that detects the cooling water temperature and a crank angle sensor 28 that outputs a pulse signal each time the crankshaft 27 of the engine 11 rotates a predetermined crank angle are attached to the cylinder block of the engine 11. Based on the output signal of the crank angle sensor 28, the crank angle and the engine speed are detected. Further, the intake air temperature is detected by the intake air temperature sensor 42.

  As the fuel of the engine 11, alcohol such as ethanol or methanol, or a mixed fuel obtained by mixing alcohol and gasoline can be used. The alcohol fuel containing these alcohols is supplied to the engine 11 as a main fuel. A mixed fuel, gasoline or the like having higher volatility than the main fuel is supplied to the engine 11 as an auxiliary fuel. A main fuel pump 31 that pumps up the main fuel is provided in the main fuel tank 30 that stores the main fuel. The main fuel discharged from the main fuel pump 31 is sent to the delivery pipe 33 through the fuel pipe 32 and is distributed from the delivery pipe 33 to the fuel injection valve 21 of each cylinder. A filter 34 and a pressure regulator 35 are connected to the fuel pipe 32 in the vicinity of the main fuel pump 31. The pressure regulator 35 regulates the discharge pressure of the main fuel pump 31 to a predetermined pressure. The surplus is returned to the main fuel tank 30 by the fuel return pipe 36.

  In addition, the delivery pipe 33 is provided with an alcohol concentration sensor 37 (alcohol concentration acquisition means) for detecting the alcohol concentration (for example, ethanol concentration) of the main fuel. The alcohol temperature sensor 37 detects a fuel temperature. Are provided integrally. The alcohol concentration sensor 37 and the fuel temperature sensor may be provided separately.

  On the other hand, a sub fuel pump 39 for pumping up auxiliary fuel is provided in the sub fuel tank 38 for storing auxiliary fuel. The auxiliary fuel discharged from the sub fuel pump 39 is injected from the injection nozzle 19 through the fuel pipe 40. Further, the fuel pipe 40 is provided with a duty control valve 41, and the auxiliary fuel injection amount of the injection nozzle 19 is adjusted by controlling the opening degree of the duty control valve 41.

  Outputs of the various sensors described above are input to a control circuit (hereinafter referred to as “ECU”) 29. The ECU 29 is mainly composed of a microcomputer, and executes various engine control programs stored in a built-in ROM (storage medium), so that the main fuel injection amount of the fuel injection valve 21 according to the engine operating state. And the auxiliary fuel injection amount of the injection nozzle 19 and the ignition timing of the spark plug 22 are controlled.

  At that time, the ECU 29 controls the supply of the auxiliary fuel as follows by executing an auxiliary fuel supply control program of FIG. 13 described later. When the cooling water temperature sensor 26 is normal within a predetermined period from the start of startup, the cooling water temperature detected by the cooling water temperature sensor 26 and the alcohol concentration (for example, ethanol concentration) of the main fuel detected by the alcohol concentration sensor 37 are normal auxiliary fuel. It is determined whether or not it is within the supply area. As shown in FIG. 2, the normal auxiliary fuel supply region is a region where the cooling water temperature is a predetermined water temperature (for example, 15 ° C.) or lower and the alcohol concentration of the main fuel is a predetermined concentration (for example, 80%) or higher. This is a region where sufficient volatility (that is, combustibility) cannot be secured.

  When the cooling water temperature and the alcohol concentration of the main fuel are within the normal auxiliary fuel supply area, it is determined that sufficient volatility of the main fuel cannot be secured, and the auxiliary fuel having higher volatility than the main fuel is supplied. To do. On the other hand, when the cooling water temperature and the alcohol concentration of the main fuel are outside the normal auxiliary fuel supply region, it is determined that the volatility of the main fuel can be sufficiently secured, and the auxiliary fuel is not supplied.

  On the other hand, when the cooling water temperature sensor 26 is abnormal within a predetermined period from the start of the start, it is determined whether or not the alcohol concentration of the main fuel is within the auxiliary fuel supply region when the cooling water temperature sensor is abnormal. As shown in FIG. 2, the auxiliary fuel supply area when the cooling water temperature sensor is abnormal is an area where the alcohol concentration of the main fuel is equal to or higher than a predetermined auxiliary fuel supply determination value (for example, 70%). A normal auxiliary fuel supply area is included in the auxiliary fuel supply area.

  When the alcohol concentration of the main fuel is within the auxiliary fuel supply area when the cooling water temperature sensor is abnormal, it is determined that there is a possibility that the volatility of the main fuel may not be sufficiently secured, and the auxiliary fuel having higher volatility than the main fuel. Implement fuel supply. On the other hand, when the alcohol concentration of the main fuel is outside the auxiliary fuel supply region when the cooling water temperature sensor is abnormal, it is determined that the volatility of the main fuel can be sufficiently secured, and the auxiliary fuel is not supplied.

  The ECU 29 executes a fuel injection control program (not shown), thereby functioning as fuel injection control means in the scope of claims. As shown in the following equation, the warm-up increase coefficient and the air-fuel ratio F are added to the basic injection amount. The main fuel injection amount is obtained by multiplying the / B (feedback) correction value, the air-fuel ratio learning value, the alcohol concentration correction value, and the like.

Main fuel injection amount = Basic injection amount x Warm-up increase coefficient
X Air-fuel ratio F / B correction value x Air-fuel ratio learning value x Alcohol concentration correction value Here, the basic injection amount is determined based on a map or the like according to the engine operating state (for example, engine speed, intake air amount, etc.) calculate. The air-fuel ratio F / B correction value is a correction amount calculated by PID control or the like so that the air-fuel ratio of the exhaust gas matches the target air-fuel ratio based on the output of the exhaust gas sensor 24. The air-fuel ratio learning value is a predetermined value. The learning value is obtained by learning and storing the air-fuel ratio F / B correction value at the learning timing.

  For the alcohol concentration correction value, an alcohol concentration correction value corresponding to the alcohol concentration of the main fuel is calculated with reference to the alcohol concentration correction value map shown in FIG. In general, since the theoretical air-fuel ratio decreases as the alcohol concentration of the main fuel increases, the map of the alcohol concentration correction value shown in FIG. 3 shows that the alcohol concentration correction value increases as the alcohol concentration of the main fuel increases. Is set to increase.

  The warm-up increase coefficient is calculated by referring to the map of the warm-up increase coefficient shown in FIG. 4 according to the coolant temperature and the alcohol concentration of the main fuel. In general, the lower the coolant temperature, the lower the volatility of the main fuel, and the higher the alcohol concentration of the main fuel, the lower the volatility of the main fuel. Therefore, the map of the warm-up increase coefficient shown in FIG. It is set so that the warm-up increase coefficient increases and the main fuel injection amount increases as the value decreases, and the warm-up increase coefficient increases and the main fuel injection amount increases as the alcohol concentration of the main fuel increases. If the cooling water temperature sensor 26 is abnormal, the warm-up increase coefficient is calculated using the pseudo water temperature as substitute information for the cooling water temperature.

  At that time, the ECU 29 sets a pseudo water temperature as follows by executing a pseudo water temperature setting program of FIG. 14 to be described later. If the cooling water temperature sensor 26 is abnormal when the engine is started, first, the pseudo water temperature initial value corresponding to the alcohol concentration of the main fuel is calculated with reference to the pseudo water temperature initial value map shown in FIG. As shown by the solid line in FIG. 5, the map of the pseudo water temperature initial value is fixed to the standard cooling water temperature after warming up (for example, 80 ° C.) in the region where the alcohol concentration of the main fuel is equal to or lower than the predetermined concentration. In the region where the alcohol concentration of the main fuel is higher than the predetermined concentration, the simulated water temperature is set to be lower than the standard cooling water temperature after warm-up, and the simulated water temperature is lowered in proportion to the increase in the alcohol concentration of the main fuel. Has been.

  As a result, when the actual cooling water temperature is in the low temperature region and the alcohol concentration of the main fuel is in the high concentration region (that is, when the volatility of the main fuel cannot be sufficiently secured), the simulated cooling water temperature is lower than the standard cooling water temperature after warming up. The warm-up increase coefficient of the main fuel injection amount is set using the water temperature, and the main fuel injection amount is sufficiently increased and corrected.

  In addition, the map of the pseudo water temperature initial value is such that, as indicated by a broken line in FIG. 5, the degree of decrease in the pseudo water temperature increases as the alcohol concentration of the main fuel increases in a region where the alcohol concentration of the main fuel is higher than the predetermined concentration. It may be set to. As a result, as the alcohol concentration of the main fuel increases, the degree of decrease in volatility increases, so that the degree of decrease in the pseudo water temperature can be increased and the amount of increase correction in the main fuel injection amount can be increased.

  Thereafter, the first pseudo water temperature lower limit guard value corresponding to the intake air temperature is calculated with reference to the map of the first pseudo water temperature lower limit guard value shown in FIG. The map of the first pseudo water temperature lower limit guard value is created based on the relationship between the intake air temperature and the cooling water temperature, and the first pseudo water temperature lower limit guard value is the minimum value in the region where the intake air temperature is equal to or lower than the low temperature side predetermined value. In the region where the intake air temperature is higher than the predetermined value on the low temperature side and lower than the predetermined value on the high temperature side, the first pseudo water temperature lower limit guard value increases as the intake air temperature increases, and the intake air temperature is equal to or higher than the predetermined value on the high temperature side. In this area, the first pseudo water temperature lower limit guard value is set to be fixed at the maximum value.

Note that the first pseudo water temperature lower limit guard value corresponding to the fuel temperature may be calculated by referring to the map of the first pseudo water temperature lower limit guard value shown in FIG. 7 instead of the map of FIG. .
Further, referring to the map of the second pseudo water temperature lower limit guard value shown in FIG. 8, the cooling water temperature and the engine stop time (stop time from the previous engine stop to the current engine start) immediately before the previous engine stop are determined. A corresponding second pseudo water temperature lower limit guard value is calculated. The map of the second pseudo water temperature lower limit guard value is created based on the relationship between the coolant temperature immediately before the last engine stop, the engine stop time, and the coolant temperature at the current engine start, and the cooling immediately before the last engine stop. The second pseudo water temperature lower limit guard value is set to be lower as the water temperature is lower, and the second pseudo water temperature lower limit guard value is set to be lower as the engine stop time is longer.

  Thereafter, the first pseudo water temperature lower limit guard value according to the intake air temperature (or fuel temperature) and the second pseudo water temperature lower limit guard value according to the cooling water temperature and the engine stop time immediately before the previous engine stop are set to the initial pseudo water temperature. By correcting the pseudo water temperature initial value by guarding the value, the error of the pseudo water temperature initial value with respect to the actual cooling water temperature is reduced, and the setting accuracy of the pseudo water temperature initial value is improved.

  In this way, after setting the pseudo water temperature initial value, referring to the map of the pseudo water temperature after starting shown in FIG. 9, according to the cooling water temperature just before the previous engine stop and the elapsed time after the current engine starting. Calculate the simulated water temperature. This simulated water temperature map after starting is created based on the relationship between the cooling water temperature just before the previous engine stop, the elapsed time after the current engine start, and the cooling water temperature. The simulated water temperature is set so that the simulated water temperature gradually rises and approaches the standard cooling water temperature after warming up (for example, 80 ° C.) as the simulated water temperature becomes higher and the elapsed time after the engine start becomes longer. Thereby, the pseudo water temperature is changed in the same manner as the actual behavior of the cooling water temperature after the engine is started, and the setting accuracy of the pseudo water temperature after the start is improved.

  Instead of the map in FIG. 9, referring to the pseudo water temperature map after starting shown in FIG. 10, information on the cooling water temperature just before the previous engine stop and the operation amount after the current engine start (for example, the integrated rotation speed) Any one of the number of times of cumulative injection, the number of times of ignition, the cumulative travel distance, etc.) may be calculated.

  Further, as shown by a solid line in FIG. 11, when the output of the exhaust gas sensor 24 becomes rich after the engine is started, the speed at which the pseudo water temperature approaches the standard cooling water temperature after warming up is increased at that time. good. When the output of the exhaust gas sensor 24 becomes rich, it can be determined that the air fuel ratio has become rich because the volatility of the main fuel has increased because the engine temperature has increased. Therefore, when the output of the exhaust gas sensor 24 becomes rich, the engine temperature rises and the actual cooling water temperature rises faster, so the speed at which the pseudo water temperature approaches the standard cooling water temperature after warming up correspondingly. Make it faster.

  In addition, as shown by a solid line in FIG. 12, when the cooling water temperature sensor 26 becomes abnormal during the air-fuel ratio F / B control after the engine is started, the abnormality of the cooling water temperature sensor 26 has occurred since the engine was started ( In the region where the alcohol concentration of the main fuel is higher than the predetermined concentration, the pseudo water temperature initial value is set to the high temperature side or the pseudo water temperature initial value is set to the standard cooling water temperature after warming up. good. Since the air-fuel ratio F / B control is started after the cooling water temperature has risen to some extent, if the cooling water temperature sensor 26 becomes abnormal during the air-fuel ratio F / B control, the pseudo-water temperature initial value is set after the warm-up. By setting the pseudo water temperature initial value to a higher temperature side than when the engine is started, the pseudo water temperature initial value can be brought closer to the actual cooling water temperature. It is possible to improve the setting accuracy of the pseudo water temperature initial value.

  Hereinafter, processing contents of the auxiliary fuel supply control program of FIG. 13 and the pseudo water temperature setting program of FIG. 14 executed by the ECU 29 will be described.

[Auxiliary fuel supply control]
The auxiliary fuel supply control program shown in FIG. 13 is executed at a predetermined cycle while the ECU 29 is turned on, and serves as auxiliary fuel supply control cutoff means in the claims. When this program is started, first, in step 101, it is determined whether or not it is within a predetermined period from the start of startup. This predetermined period is, for example, a time or a crank angle set according to at least one of the coolant temperature, the intake air temperature, the fuel temperature, and the like.

  If it is determined in this step 101 that it is within a predetermined period from the start of the start, the process proceeds to step 102 and it is determined whether or not the cooling water temperature sensor 26 is normal based on an abnormality diagnosis result of the cooling water temperature sensor 26 or the like. . When it is determined that the cooling water temperature sensor 26 is normal, the process proceeds to step 103, where it is determined whether or not the cooling water temperature detected by the cooling water temperature sensor 26 is equal to or lower than a predetermined water temperature (for example, 15 ° C.). In step 104, it is determined whether or not the alcohol concentration of the main fuel detected by the alcohol concentration sensor 37 is equal to or higher than a predetermined concentration (for example, 80%), so that the cooling water temperature and the alcohol concentration of the main fuel are supplied with normal auxiliary fuel. It is determined whether or not it is within the area (see FIG. 2).

  When it is determined in these steps 103 and 104 that the cooling water temperature and the alcohol concentration of the main fuel are within the normal auxiliary fuel supply region (that is, the cooling water temperature is equal to or lower than the predetermined water temperature and the alcohol concentration of the main fuel is equal to or higher than the predetermined concentration). If it is determined that the main fuel is not sufficiently volatile, the process proceeds to step 108, where auxiliary fuel having higher volatility than the main fuel is supplied.

  On the other hand, when it is determined in steps 103 and 104 that the cooling water temperature and the alcohol concentration of the main fuel are not within the normal auxiliary fuel supply region (that is, it is determined that the cooling water temperature is higher than the predetermined water temperature). Or if the alcohol concentration of the main fuel is determined to be lower than the predetermined concentration), it is determined that the volatility of the main fuel can be sufficiently secured, and the routine proceeds to step 109 and the auxiliary fuel is not supplied. .

  On the other hand, if it is determined in step 102 that the cooling water temperature sensor 26 is abnormal (not normal), the process proceeds to step 105, and the simulated water temperature is set to the standard cooling water temperature after warming up (for example, 80 ° C.). The simulated water temperature is used as substitute information for the cooling water temperature. However, when calculating the warm-up increase coefficient of the main fuel injection amount, the simulated water temperature set by the simulated water temperature setting program of FIG. 14 described later is used as substitute information for the cooling water temperature.

  Thereafter, the routine proceeds to step 106, where it is determined whether or not the engine 11 is in a state where the engine 11 cannot be started, for example, depending on whether or not a state in which the engine speed does not exceed the complete explosion determination value has continued for a predetermined period. If it is determined that the engine 11 is not ready to start, the routine proceeds to step 107, where it is determined whether or not the alcohol concentration of the main fuel is equal to or higher than the auxiliary fuel supply determination value (for example, 70%). It is determined whether or not the alcohol concentration of the fuel is within the auxiliary fuel supply region (see FIG. 2) when the cooling water temperature sensor is abnormal.

  In step 106, it is determined that the engine 11 cannot be started, and in step 107, the alcohol concentration of the main fuel is within the auxiliary fuel supply region when the cooling water temperature sensor is abnormal (that is, the alcohol concentration of the main fuel is the auxiliary fuel). If it is determined that there is a possibility that the volatility of the main fuel may not be sufficiently secured, the process proceeds to step 108 and the auxiliary fuel having higher volatility than the main fuel is determined. Implement the supply.

  On the other hand, when it is determined in step 106 that the engine 11 can be started, or in step 107, the alcohol concentration of the main fuel is not within the auxiliary fuel supply region when the cooling water temperature sensor is abnormal (that is, the main fuel). If it is determined that the alcohol concentration of the fuel is lower than the auxiliary fuel supply determination value), it is determined that the volatility of the main fuel can be sufficiently ensured, and the process proceeds to step 110, and the auxiliary fuel is not supplied. Therefore, when the engine 11 can be started, the auxiliary fuel is not supplied even if the alcohol concentration of the main fuel is equal to or higher than the auxiliary fuel supply determination value.

[Pseudo water temperature setting program]
The simulated water temperature setting program shown in FIG. 14 is executed at a predetermined cycle while the ECU 29 is turned on, and serves as a simulated water temperature setting means in the claims. When this program is started, first, in step 201, it is determined whether or not the cooling water temperature sensor 26 is normal based on an abnormality diagnosis result of the cooling water temperature sensor 26 or the like. If it is determined that the cooling water temperature sensor 26 is normal, the program is terminated without executing the processing from step 202 onward.

  On the other hand, when it is determined in step 201 that the cooling water temperature sensor 26 is abnormal (not normal), the processing after step 202 is executed as follows. First, in step 202, it is determined whether or not it is at the time of start (before completion of start), for example, by whether or not it is before complete explosion determination. If it is determined in step 202 that the engine is at the time of starting, the process proceeds to step 203, and the pseudo water temperature initial value corresponding to the alcohol concentration of the main fuel is determined with reference to the map of the pseudo water temperature initial value shown in FIG. By calculating, in the region where the alcohol concentration of the main fuel is higher than the predetermined concentration, the pseudo water temperature is set to be lower than the standard cooling water temperature after warming up.

  Thereafter, the process proceeds to step 204, and the first pseudo water temperature lower limit guard value corresponding to the intake air temperature (or fuel temperature) is referred to with reference to the map of the first pseudo water temperature lower limit guard value shown in FIG. 6 (or FIG. 7). And a second pseudo water temperature lower limit guard value corresponding to the cooling water temperature and engine stop time immediately before the previous engine stop is calculated with reference to the map of the second pseudo water temperature lower limit guard value shown in FIG. To do.

  After this, the routine proceeds to step 205, where the first pseudo water temperature lower limit guard value corresponding to the intake air temperature (or fuel temperature) and the second pseudo water temperature lower limit guard corresponding to the cooling water temperature and engine stop time immediately before the previous engine stop. The pseudo water temperature initial value is guarded by the value to correct the pseudo water temperature initial value, thereby reducing the error of the pseudo water temperature initial value with respect to the actual cooling water temperature.

  Thereafter, when it is determined in the above step 202 that it is not at the time of starting (after the completion of starting), the process proceeds to step 206, and a map of the pseudo water temperature after starting shown in FIG. 9 (or FIG. 10) is referred to. In accordance with the cooling water temperature immediately before the previous engine stop and the elapsed time after the current engine start (or any one of the cumulative number of revolutions, the cumulative number of injections, the total number of ignitions, the total travel distance, etc.) By calculating the water temperature, the simulated water temperature after startup is changed so that the simulated water temperature after startup gradually increases and approaches the standard cooling water temperature after warming up.

  Further, as shown by a solid line in FIG. 11, when the output of the exhaust gas sensor 24 becomes rich after the engine is started, the speed at which the pseudo water temperature approaches the standard cooling water temperature after warming up is increased at that time. good.

  In addition, as shown by a solid line in FIG. 12, when the cooling water temperature sensor 26 becomes abnormal during the air-fuel ratio F / B control after the engine is started, the abnormality of the cooling water temperature sensor 26 has occurred since the engine was started ( In the region where the alcohol concentration of the main fuel is higher than the predetermined concentration, the pseudo water temperature initial value is set to the high temperature side or the pseudo water temperature initial value is set to the standard cooling water temperature after warming up. good.

  In the first embodiment described above, when the coolant temperature sensor 26 is abnormal, the auxiliary fuel is supplied when the alcohol concentration of the main fuel is equal to or higher than the auxiliary fuel supply determination value. If the alcohol concentration is a high concentration region that is equal to or higher than the auxiliary fuel supply determination value, the auxiliary fuel is supplied in the entire temperature region from the low temperature region to the high temperature region of the cooling water temperature. As a result, when the actual cooling water temperature is in the low temperature region and the alcohol concentration of the main fuel is in the high concentration region (that is, when the volatility of the main fuel cannot be sufficiently secured), the auxiliary fuel can be reliably supplied. In addition, it is possible to improve the startability at a low temperature when the cooling water temperature sensor 26 is abnormal and the drivability immediately after the start. In addition, when the alcohol concentration of the main fuel is lower than the auxiliary fuel supply determination value, it is determined that the volatility of the main fuel can be sufficiently secured, and the auxiliary fuel is not supplied. Use can be prevented.

  In addition, in the first embodiment, when the cooling water temperature sensor 26 is abnormal, the auxiliary fuel is supplied only when the engine 11 is in an inoperative state and the alcohol concentration of the main fuel is equal to or higher than the auxiliary fuel supply determination value. When the engine 11 can be started, it is determined that the volatility of the main fuel can be sufficiently secured even if the alcohol concentration of the main fuel is equal to or higher than the auxiliary fuel supply determination value, so that the auxiliary fuel is not supplied. The amount of fuel used can be reduced.

  In the first embodiment, when the cooling water temperature sensor 26 is abnormal, a pseudo water temperature lower than the standard cooling water temperature after warming up is set when the alcohol concentration of the main fuel is high, and this pseudo water temperature is set as the cooling water temperature. The warm-up increase coefficient of the main fuel injection amount is calculated using this as substitute information. As a result, when the actual cooling water temperature is in the low temperature range and the alcohol concentration of the main fuel is in the high concentration range (that is, when the volatility of the main fuel cannot be sufficiently secured), it is set lower than the standard cooling water temperature after warm-up. Since the warm-up increase coefficient of the main fuel injection amount can be calculated using the simulated water temperature, the injection amount of the main fuel can be sufficiently increased and corrected, and the cooling water temperature sensor 26 can be started at a low temperature when an abnormality occurs. And drivability immediately after start-up can be improved, and the startable area can be expanded.

  Moreover, in the first embodiment, the pseudo water temperature gradually rises as the elapsed time after engine startup becomes longer and approaches the standard coolant temperature after warm-up, so that the behavior of the actual coolant temperature after engine startup is increased. The pseudo water temperature can be changed in the same manner as described above, and the setting accuracy of the pseudo water temperature and thus the calculation accuracy of the warm-up increase coefficient using the pseudo water temperature can be improved.

Next, Embodiment 2 of the present invention will be described with reference to FIGS.
In the first embodiment, the auxiliary fuel supply determination value when the cooling water temperature sensor is abnormal is a fixed value. However, in the second embodiment, the auxiliary fuel supply control program of FIG. The auxiliary fuel supply determination value E is changed according to the intake air temperature.

  In the auxiliary fuel supply control program shown in FIG. 15, it is determined whether or not the cooling water temperature sensor 26 is normal within a predetermined period from the start of start (steps 101 and 102). If the cooling water temperature sensor 26 is normal, By determining whether or not the cooling water temperature is equal to or lower than a predetermined water temperature (for example, 15 ° C.) and the alcohol concentration of the main fuel is equal to or higher than a predetermined concentration (for example, 80%), the cooling water temperature and the alcohol concentration of the main fuel are It is determined whether or not it is within the fuel supply region (see FIG. 17) (steps 103 and 104).

  As a result, when it is determined that the cooling water temperature and the alcohol concentration of the main fuel are within the normal auxiliary fuel supply region, the auxiliary fuel having higher volatility than the main fuel is supplied (step 108). On the other hand, when it is determined that the cooling water temperature and the alcohol concentration of the main fuel are not within the normal auxiliary fuel supply region, the auxiliary fuel is not supplied (step 109).

  On the other hand, when the cooling water temperature sensor 26 is abnormal, the pseudo water temperature is set to a standard cooling water temperature after warming up (for example, 80 ° C.), and then it is determined whether or not the engine 11 is in an inoperative state (step 105). 106). If it is determined that the engine 11 is not ready to start, the routine proceeds to step 107a, where the auxiliary fuel supply determination value E corresponding to the intake air temperature is determined with reference to the auxiliary fuel supply determination value E table shown in FIG. calculate.

  In general, the higher the engine temperature, the higher the intake air temperature, and the higher the engine temperature, the higher the volatility of the main fuel and the higher the alcohol concentration at which auxiliary fuel needs to be supplied. Therefore, the table of auxiliary fuel supply determination value E shown in FIG. 16 shows that the auxiliary fuel supply determination value E increases as the intake air temperature, which is information on the engine temperature, increases, and the alcohol concentration of the main fuel that supplies the auxiliary fuel becomes higher. It is set to be high. Further, in a region where the intake air temperature is equal to or higher than a predetermined value (for example, 30 ° C.), the auxiliary fuel supply determination value E is set to a value (for example, 110%) larger than 100% so that the auxiliary fuel is not supplied. ing.

  Thereafter, the process proceeds to step 107b, and it is determined whether or not the alcohol concentration of the main fuel is equal to or higher than the auxiliary fuel supply determination value E, whereby the auxiliary fuel supply region when the alcohol concentration of the main fuel is abnormal in the cooling water temperature sensor (FIG. 17)).

  If it is determined in step 106 that the engine 11 is in an unstartable state, and it is determined in step 107b that the alcohol concentration of the main fuel is within the auxiliary fuel supply region when the cooling water temperature sensor is abnormal, the main fuel The auxiliary fuel having higher volatility is supplied (step 108). On the other hand, when it is determined in step 106 that the engine 11 can be started, or in step 107b, it is determined that the alcohol concentration of the main fuel is not within the auxiliary fuel supply region when the cooling water temperature sensor is abnormal. In such a case, the auxiliary fuel is not supplied (step 110).

  In the second embodiment described above, the auxiliary fuel supply determination value E is changed in accordance with the intake air temperature, which is information on the engine temperature. Therefore, the volatility of the main fuel is changed in accordance with the engine temperature, and the auxiliary fuel is changed. The auxiliary fuel supply determination value E can be changed to an appropriate value in response to a change in the alcohol concentration of the main fuel that needs to be supplied, and an excessive supply of auxiliary fuel can be prevented.

In the second embodiment, the auxiliary fuel supply determination value E is changed according to the intake air temperature. However, the auxiliary fuel supply determination value E may be changed according to the fuel temperature.
Further, as shown in FIG. 18, an estimated coolant temperature is calculated according to the coolant temperature immediately before the previous engine stop and the engine stop time, and the auxiliary fuel supply determination value E is changed according to the estimated coolant temperature. May be. In this case, the auxiliary fuel supply determination value E increases as the estimated cooling water temperature, which is information on the engine temperature, increases, and the alcohol concentration of the main fuel that supplies the auxiliary fuel is increased. Further, in the region where the estimated cooling water temperature is equal to or higher than a predetermined value (for example, 60 ° C.), the auxiliary fuel supply determination value E is set to a value larger than 100% (for example, 110%) so that the auxiliary fuel is not supplied. To.

  Even in this case, the auxiliary fuel supply judgment value E is set appropriately in response to the change in the volatility of the main fuel according to the engine temperature and the change in the alcohol concentration of the main fuel that requires the supply of the auxiliary fuel. Can be changed to a value.

[Other Examples]
In each of the first and second embodiments, the pseudo water temperature initial value corresponding to the alcohol concentration of the main fuel is calculated, the pseudo water temperature lower limit guard value corresponding to the intake air temperature is calculated, and then the pseudo water temperature corresponding to the alcohol concentration of the main fuel is calculated. The water temperature initial value is guarded with the pseudo water temperature lower limit guard value corresponding to the intake air temperature to correct the pseudo water temperature initial value. However, referring to the two-dimensional map of the pseudo water temperature initial value shown in FIG. The pseudo water temperature initial value corresponding to the alcohol concentration and the intake air temperature may be calculated. Alternatively, the pseudo water temperature initial value corresponding to the alcohol concentration of the main fuel and the fuel temperature may be calculated.

  In the first and second embodiments, when the cooling water temperature sensor 26 is abnormal, the supply of auxiliary fuel is performed only when the engine 11 is not startable and the alcohol concentration of the main fuel is equal to or higher than the auxiliary fuel supply determination value. However, when the process of determining whether or not the engine 11 is in an unstartable state is omitted and the cooling water temperature sensor 26 is abnormal, the alcohol concentration of the main fuel is equal to or higher than the auxiliary fuel supply determination value. At this time, the auxiliary fuel may be supplied.

  In each of the first and second embodiments, the alcohol concentration sensor 37 detects the alcohol concentration of the main fuel. However, in the case of a system that does not include the alcohol concentration sensor 37, the air-fuel ratio F / B correction value. The alcohol concentration may be estimated based on the above.

  In the first and second embodiments, the auxiliary fuel is supplied when the alcohol concentration of the main fuel is equal to or higher than a predetermined auxiliary fuel supply determination value when the cooling water temperature sensor is abnormal, and the main fuel when the cooling water temperature sensor is abnormal. Although the simulated water temperature is lower than the standard cooling water temperature after warming up when the alcohol concentration of the engine is high, both of these techniques are used to execute the technique of increasing the main fuel injection amount using this simulated water temperature. Only one of them may be executed.

  In addition, when the alcohol concentration of the main fuel is high when the cooling water temperature sensor is abnormal, a technology that sets a pseudo water temperature lower than the standard cooling water temperature after warm-up and uses this pseudo water temperature to correct the injection amount of the main fuel is increased. You may apply to the system which is not equipped with the auxiliary fuel supply apparatus.

It is a schematic block diagram of the whole engine control system in Example 1 of this invention. It is a figure which shows the auxiliary fuel supply area | region of Example 1. FIG. It is a figure which shows notionally an example of the map of alcohol concentration correction value. It is a figure which shows notionally an example of the map of a warm-up increase coefficient. It is a figure which shows notionally an example of the map (the 1) of a pseudo water temperature initial value. It is a figure which shows notionally an example of the map of the 1st pseudo | simulation water temperature minimum guard value (the 1). It is a figure which shows notionally an example of the map (the 2) of a 1st pseudo water temperature lower limit guard value. It is a figure which shows notionally an example of the map of a 2nd pseudo water temperature lower limit guard value. It is a figure which shows notionally an example of the map of the pseudo water temperature after the start (the 1). It is a figure which shows notionally an example of the map of the pseudo water temperature after the start (the 2). It is a figure which shows notionally an example of the map (the 3) of the pseudo water temperature after starting. It is a figure which shows notionally an example of the map (the 2) of a pseudo water temperature initial value. 3 is a flowchart illustrating a flow of processing of an auxiliary fuel supply control program according to the first embodiment. It is a flowchart which shows the flow of a process of the pseudo water temperature setting program of Example 1. It is a flowchart which shows the flow of a process of the auxiliary fuel supply control program of Example 2. FIG. It is a figure which shows notionally an example of the table of the auxiliary fuel supply determination value of Example 2. FIG. FIG. 6 is a diagram illustrating an auxiliary fuel supply region of Example 2. FIG. 10 is a diagram illustrating an auxiliary fuel supply region in a modified example of the second embodiment. It is a figure which shows notionally an example of the two-dimensional map of the pseudo water temperature initial value in another Example.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Engine (internal combustion engine), 12 ... Intake pipe, 16 ... Throttle valve, 19 ... Injection nozzle, 21 ... Fuel injection valve, 22 ... Spark plug, 23 ... Exhaust pipe, 24 ... Exhaust gas sensor, 26 ... Cooling water temperature sensor, 29 ... ECU (auxiliary fuel supply control means, fuel injection control means, pseudo water temperature setting means), 30 ... main fuel tank, 37 ... alcohol concentration sensor (alcohol concentration acquisition means), 38 ... sub fuel tank, 41 ... duty control valve

Claims (4)

Applied to a system capable of supplying a main fuel containing alcohol as a fuel for an internal combustion engine and an auxiliary fuel having higher volatility than the main fuel, and an alcohol concentration acquisition means for detecting or estimating the alcohol concentration of the main fuel; Controlling the supply of the auxiliary fuel based on a cooling water temperature sensor for detecting the cooling water temperature of the internal combustion engine, the cooling water temperature detected by the cooling water temperature sensor, and the alcohol concentration of the main fuel detected or estimated by the alcohol concentration acquisition means In an internal combustion engine control device comprising an auxiliary fuel supply control means,
When the cooling water temperature sensor is abnormal, the auxiliary fuel supply control means is configured to detect the auxiliary fuel when the alcohol concentration of the main fuel detected or estimated by the alcohol concentration acquisition means is equal to or higher than a predetermined auxiliary fuel supply determination value. A control apparatus for an internal combustion engine, characterized in that supply is performed.   When the cooling water temperature sensor is abnormal, the auxiliary fuel supply control means is in a state where the internal combustion engine cannot be started and the alcohol concentration of the main fuel detected or estimated by the alcohol concentration acquisition means is greater than or equal to the auxiliary fuel supply determination value. 2. The control apparatus for an internal combustion engine according to claim 1, wherein the auxiliary fuel is supplied at the time.   The control of the internal combustion engine according to claim 1 or 2, wherein the auxiliary fuel supply control means changes the auxiliary fuel supply determination value according to at least one of an intake air temperature and a fuel temperature of the internal combustion engine. apparatus.   The auxiliary fuel supply control means changes the auxiliary fuel supply determination value according to a coolant temperature immediately before the previous stop of the internal combustion engine and a stop time from the previous stop to the current start. The control device for an internal combustion engine according to any one of 1 to 3.

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