JP2010001769A - Control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve torque control accuracy by setting a torque allowable value of torque reserve control at a proper value in response to an alcohol concentration of fuel. <P>SOLUTION: During the torque reserve control, the device calculates a basic torque allowable value in response to an engine operation state (for instance, engine rotation speed, load or the like), various correction factors (vehicle speed correction factor, cooling water correction factor, atmospheric pressure correction factor, steering angle correction factor or the like), and alcohol concentration correction factor in response to the alcohol concentration of the fuel and cooling water temperature (engine temperature information). The final torque allowable value is obtained by multiplying the basic torque allowable value by the various correction factors and alcohol concentration correction factor, so that the torque allowable value is corrected to be set at a proper value in response to alcohol concentration of fuel by coping with the change in torque and combustion stability of the engine due to the alcohol concentration of the fuel and engine temperature. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention offsets the intake air amount control parameter in the torque increasing direction by a predetermined torque margin value during idling operation of the internal combustion engine, and offsets the torque control parameter in the torque decreasing direction so as to cancel the torque increase. The present invention relates to a control device for an internal combustion engine that performs torque reserve control.

  In torque control of an internal combustion engine, torque fluctuation due to load fluctuations of auxiliary equipment such as an air conditioner compressor and a power steering pump during idling is calculated as throttle opening (throttle valve opening) or ISC valve opening (idle speed). Even if an attempt is made to suppress by correcting the intake air amount by correcting the opening of the control valve) until the torque changes due to the actual change in the cylinder charge air amount after the throttle opening or the ISC valve opening changes. Since the response delay is relatively large, the torque fluctuation (idle rotation fluctuation) due to the load fluctuation of the auxiliary machinery cannot be suppressed with good response in the correction of the throttle opening or the ISC valve opening.

  Therefore, as described in Patent Document 1 (Japanese Patent Application Laid-Open No. 2006-138300), focusing on the fact that the ignition timing retard / advance correction appears in the torque change with good response, the auxiliary machine during idle operation There is a type in which torque fluctuation due to load fluctuation is suppressed with good response by correcting the ignition timing.

  In general, the ignition timing of the internal combustion engine is controlled so as to approach the optimum ignition timing MBT at which the torque / fuel consumption rate is the best, but if the ignition timing is too close to the optimum ignition timing MBT, the load on the auxiliary machinery Even if you attempt to suppress the torque fluctuation by compensating the torque decrease due to the fluctuation with the torque increase due to the ignition timing advance angle correction, the ignition timing advance angle correction will compensate for the torque increase due to the load fluctuation of the auxiliary machinery. As a result, there is no room to ensure, and torque fluctuations (idle rotation fluctuations) cannot be sufficiently suppressed.

As a countermeasure, in the torque control of Patent Document 1, the throttle opening set according to the required torque is offset in the torque increasing direction by a predetermined torque margin value, and the torque increase due to the offset of the throttle opening is set to the ignition timing. By performing torque reserve control that cancels by offsetting in the retarding direction (torque decreasing direction) to achieve the required torque, the torque increase that compensates for the torque decrease due to load fluctuations of auxiliary machinery is advanced. A margin to be secured by angle correction is provided.
JP 2006-138300 A (see page 2)

  In recent years, in response to social demands such as CO2 emission reduction and the use of alternative fuels for oil, internal combustion engines that can use gasoline, alcohol (ethanol, methanol, etc.), and alcohol-mixed fuels that are a mixture of gasoline and alcohol can be used as fuels. The demand for onboard vehicles is increasing.

  In general, alcohol fuel (alcohol or alcohol blended fuel) has a higher octane number than gasoline and the knock limit of the ignition timing is on the advance side. Output (torque) can be increased. In addition, alcohol fuel has a larger latent heat of vaporization than gasoline and has a higher cooling effect on the air-fuel mixture due to the latent heat of vaporization, which improves the in-cylinder filling efficiency and synergies with the above-described advance correction of the ignition timing. The effect is that the output (torque) of the internal combustion engine can be increased efficiently. For this reason, the torque of the internal combustion engine increases as the alcohol concentration of the fuel increases. On the other hand, alcohol fuel has a larger latent heat of vaporization than gasoline and is difficult to vaporize at low temperatures. Therefore, combustion stability decreases as the alcohol concentration of the fuel increases at low temperatures.

  However, in the torque control of Patent Document 1 described above, the torque of the internal combustion engine and the change in combustion stability due to the change in the alcohol concentration of the fuel are not taken into consideration at all. If the combustion stability changes, the torque reserve control torque margin value may become excessive or insufficient, and the torque control accuracy may be reduced. For example, if the torque margin value becomes too large, the torque becomes excessive, and the idle rotation speed may exceed the target idle rotation speed, and on the contrary, if the torque margin value becomes too small, There is a possibility that the idle rotation speed becomes lower than the target idle rotation speed due to insufficient torque.

  The present invention has been made in consideration of such circumstances, and therefore the object of the present invention is to set the torque reserve control torque margin value to an appropriate value according to the alcohol concentration of the fuel, An object of the present invention is to provide a control device for an internal combustion engine capable of improving torque control accuracy.

  In order to achieve the above object, according to the first aspect of the present invention, an intake air amount control parameter (for example, throttle opening) is offset in a torque increasing direction by a predetermined torque margin value during idling of the internal combustion engine. In a control device for an internal combustion engine that performs torque reserve control for offsetting a torque control parameter (for example, ignition timing) in a torque decreasing direction so as to cancel a torque increase, an alcohol concentration determination unit that determines an alcohol concentration of fuel supplied to the internal combustion engine The torque margin value is corrected by the torque margin value correcting means according to the alcohol concentration.

  In this configuration, since the torque margin value can be corrected according to the alcohol concentration of the fuel, the torque margin value is set in response to changes in the torque and combustion stability of the internal combustion engine according to the alcohol concentration of the fuel. By correcting, the torque margin value can be set to an appropriate value. As a result, even if there is a situation where the torque or combustion stability of the internal combustion engine changes depending on the alcohol concentration of the fuel, the torque margin value for torque reserve control performed during idle operation is set to an appropriate value according to the alcohol concentration of the fuel. Thus, the torque control accuracy can be improved, and the idle rotation speed can be stabilized.

  As shown in FIG. 2, in general, alcohol fuel (alcohol or alcohol-mixed fuel) is easily vaporized in a high temperature region where the temperature of the internal combustion engine (for example, cooling water temperature) is relatively high. Engine torque tends to increase. On the other hand, in a low temperature region where the temperature of the internal combustion engine is relatively low, the alcohol fuel is less likely to be vaporized, so that the combustion stability tends to decrease as the alcohol concentration of the fuel increases.

  In consideration of such characteristics, the temperature of the internal combustion engine or information related thereto (hereinafter referred to as “engine temperature information”) is detected or estimated by the engine temperature information determination means as in claim 2, and alcohol The torque margin value may be corrected in consideration of the engine temperature information in addition to the concentration. In this way, the torque margin value is corrected so that the torque margin value is accurately adjusted to an appropriate value in response to changes in the torque and combustion stability of the internal combustion engine depending on the alcohol concentration of the fuel and the temperature of the internal combustion engine. Can be set.

  Specifically, as in claim 3, it is preferable that the torque margin value be corrected to be smaller as the alcohol concentration is higher when the engine temperature information is in a predetermined high temperature region. In this way, when the engine temperature information is in a high temperature region where the alcohol fuel is easily vaporized, the torque margin value is reduced in response to the increase in the torque of the internal combustion engine as the alcohol concentration of the fuel increases. Is possible.

  Further, as in claim 4, when the engine temperature information is in a predetermined low temperature region, the torque margin value may be corrected so as to increase as the alcohol concentration increases. In this way, when the engine temperature information is in a low temperature region where the alcohol fuel is difficult to vaporize, the torque margin value is increased corresponding to the fact that the combustion stability of the internal combustion engine decreases as the alcohol concentration of the fuel increases. Control becomes possible.

Hereinafter, an embodiment embodying the best mode for carrying out the present invention will be described.
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 intake pipe pressure sensor 19 for detecting the intake pipe pressure is provided in the surge tank 18. The surge tank 18 is provided with an intake manifold 20 for introducing air into each cylinder of the engine 11, and a fuel injection valve 21 for injecting fuel is attached in the vicinity of the intake port of the intake manifold 20 of each cylinder. Yes. Further, a spark plug 22 is attached to each cylinder of the cylinder head of the engine 11, and the air-fuel mixture in the cylinder is ignited by the spark discharge of each spark 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.

  Further, a cooling water temperature sensor 26 (engine temperature information determining means) for detecting a cooling water temperature (engine temperature information) and a knock sensor 29 for detecting knocking vibration are attached to the cylinder block of the engine 11. A crank angle sensor 28 that outputs a pulse signal every time the crankshaft 27 rotates by a predetermined crank angle is attached to the outer peripheral side of the crankshaft 27. Based on the output signal of the crank angle sensor 28, the crank angle and engine The rotation speed is detected.

  The engine 11 can use any of gasoline, alcohol (ethanol, methanol, etc.), and alcohol mixed fuel obtained by mixing alcohol in gasoline as fuel, and any one of these gasoline, alcohol, alcohol mixed fuel can be refueled. The engine 11 is supplied. A fuel pump 31 that pumps up the fuel is provided in the fuel tank 30 that stores the fuel. The fuel discharged from the 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.

  Further, an alcohol concentration sensor 34 (alcohol concentration determination means) for detecting the alcohol concentration (for example, ethanol mixing ratio) of the fuel is provided at an appropriate location in the fuel supply system from the fuel tank 30 to the fuel injection valve 21. In this embodiment, an alcohol concentration sensor 34 is provided integrally with a fuel pump 31 disposed in the fuel tank 30. The alcohol concentration sensor 34 may be any type of alcohol concentration sensor. For example, a capacitance-type alcohol concentration sensor that detects the alcohol concentration by measuring the capacitance according to the dielectric constant of the fuel. Alternatively, an optical (transmission type) alcohol concentration sensor that measures the amount of light transmitted through the fuel (transmittance) to detect the alcohol concentration may be used.

  Outputs of these various sensors are input to an engine control circuit (hereinafter referred to as “ECU”) 35. The ECU 35 is mainly composed of a microcomputer, and executes various engine control programs stored in a built-in ROM (storage medium) to thereby determine the fuel injection amount of the fuel injection valve 21 according to the engine operating state. The ignition timing of the spark plug 22 is controlled.

  Further, the ECU 35 offsets the throttle opening (intake air amount control parameter) set according to the required torque during the idling operation of the engine 11 in the torque increasing direction by a predetermined torque margin value. Torque reserve control for canceling the torque increase due to the offset by offsetting the ignition timing (torque control parameter) in the retard direction (torque decreasing direction) to achieve the required torque is performed. With this torque reserve control, there is a margin to secure a torque increase by compensating for the ignition timing advance to compensate for the torque decrease due to load fluctuations in auxiliary equipment such as air conditioner compressors and power steering pumps. . At this time, the ECU 35 executes a torque margin value setting routine shown in FIG. 6 described later, so that the alcohol concentration of the fuel detected by the alcohol concentration sensor 34 and the coolant temperature (engine temperature information) detected by the coolant temperature sensor 26 are obtained. Accordingly, the torque margin value is corrected.

Hereinafter, the torque reserve control of this embodiment will be described with reference to FIGS.
As shown in FIG. 3, first, a basic torque margin value corresponding to an engine operating state (for example, engine speed and load) is calculated using a map or a mathematical formula. In addition, various correction coefficients such as a vehicle speed correction coefficient according to the vehicle speed, a cooling water temperature correction coefficient according to the cooling water temperature, an atmospheric pressure correction coefficient according to the atmospheric pressure, and a steering steering angle correction coefficient according to the steering angle are respectively mapped. Or it calculates by numerical formula etc.

  Further, the alcohol concentration correction coefficient setting unit 36 maps the alcohol concentration correction coefficient according to the alcohol concentration of the fuel detected by the alcohol concentration sensor 34 and the cooling water temperature (engine temperature information) detected by the cooling water temperature sensor 26 as a map or formula. Etc. are calculated.

  As shown in FIG. 2, in general, alcohol fuel (alcohol or alcohol-mixed fuel) is liable to vaporize in a high temperature region where the coolant temperature is relatively high. Therefore, the torque of the engine 11 tends to increase as the alcohol concentration of the fuel increases. There is. On the other hand, in a low temperature region where the cooling water temperature is relatively low, the alcohol fuel is less likely to vaporize, and therefore, the combustion stability tends to decrease as the alcohol concentration of the fuel increases.

  In consideration of such characteristics, as shown in FIG. 4A, the map of the alcohol concentration correction coefficient indicates that the higher the alcohol concentration of the fuel, the higher the alcohol concentration of the fuel when the cooling water temperature is in a high temperature region where the alcohol fuel is easily vaporized. Corresponding to the increase in the torque 11, the alcohol concentration correction coefficient is set to be smaller and the torque margin value is decreased as the alcohol concentration of the fuel is higher.

  On the other hand, as shown in FIG. 4B, the alcohol concentration correction coefficient map shows that the combustion stability of the engine 11 decreases as the alcohol concentration of the fuel increases when the cooling water temperature is in a low temperature region where the alcohol fuel is difficult to vaporize. Correspondingly, the higher the alcohol concentration of the fuel is, the higher the alcohol concentration correction coefficient is set to increase the torque margin value.

Thereafter, in the torque margin value correction unit 37 (torque margin value correcting means), various correction coefficients (vehicle speed correction coefficient, cooling water temperature correction coefficient, atmospheric pressure correction coefficient, steering steering angle correction coefficient, etc.) and alcohol are added to the basic torque margin value. By multiplying the concentration correction coefficient to obtain a final torque margin value, a corrected torque margin value is set according to the alcohol concentration of the fuel and the coolant temperature (engine temperature information).
Torque margin value = basic torque margin value x various correction factors x alcohol concentration correction factor

Thus, the torque margin value is corrected and the torque margin value is accurately set to an appropriate value in response to changes in the torque and combustion stability of the engine 11 depending on the alcohol concentration of the fuel and the engine temperature.
After the torque margin value is set in this manner, the torque reserve control unit 38 sets the throttle opening and ignition timing as follows.

  As shown in FIG. 5, when setting the throttle opening, first, a driver request torque is calculated based on the accelerator opening, the engine rotation speed, and the like, and this driver request torque is determined by ISC (idle rotation speed control). The required torque is obtained by adding the torque increase / decrease and various loss torques (internal loss torque, external loss torque, etc.). Here, the internal loss torque is a mechanical friction loss, a pumping loss, etc., and the external loss torque is a load torque of auxiliary machinery (air conditioner compressor, alternator, power steering pump, etc.) driven by the power of the engine 11. It is.

  Then, after obtaining a value obtained by adding a torque margin value to the required torque (hereinafter referred to as “request torque + torque margin value”), the throttle opening corresponding to this “request torque + torque margin value” is mapped, etc. And the throttle opening corresponding to “request torque + torque margin value” is set at the base ignition timing (for example, the optimal ignition timing MBT at which the torque / fuel consumption rate is optimal). As a result, the throttle opening is offset in the torque increasing direction by the torque margin value.

  When setting the ignition timing, first, a ratio between the required torque and “requested torque + torque margin value” is calculated as torque efficiency. The method for calculating the torque efficiency may be changed as appropriate. For example, the estimated torque at the optimal ignition timing MBT is calculated based on the engine operating state (for example, engine speed, intake air amount, air-fuel ratio, etc.) A ratio between the required torque and the estimated torque at the optimum ignition timing MBT may be calculated as torque efficiency.

  Thereafter, the required torque is realized by calculating the ignition delay amount R according to the torque efficiency with reference to the map of the ignition delay amount R (offset amount in the retard direction from the optimal ignition timing MBT). An ignition retard amount R required for the calculation is obtained. The map of the ignition retard amount R is set so that the ignition retard amount R = 0 when the torque efficiency = 1, and the ignition retard amount R increases as the torque efficiency becomes smaller than 1. .

  Thereafter, an ignition timing retarded by an ignition retardation amount R from the optimal ignition timing MBT is calculated. Thus, the ignition timing is offset in the retarding direction (torque decreasing direction) by the torque margin value so as to realize the required torque, and the torque increase due to the offset of the throttle opening is canceled.

  Hereinafter, the processing contents of the torque margin value setting routine of FIG. 6 executed by the ECU 35 during the torque reserve control described above will be described. The torque margin value setting routine of FIG. 6 is repeatedly executed at a predetermined cycle during engine operation. When this routine is started, first, in step 101, a basic torque margin value corresponding to the engine operating state (for example, engine speed and load) is calculated using a map or a mathematical formula, and then the process proceeds to step 102, where the vehicle speed is increased. Various correction factors such as a vehicle speed correction coefficient according to the cooling water temperature, a cooling water temperature correction coefficient according to the cooling water temperature, an atmospheric pressure correction coefficient according to the atmospheric pressure, a steering steering angle correction coefficient according to the steering angle, respectively, a map or a numerical formula, etc. Calculated by

Thereafter, the process proceeds to step 103, where an alcohol concentration correction coefficient corresponding to the alcohol concentration of the fuel detected by the alcohol concentration sensor 34 and the cooling water temperature (engine temperature information) detected by the cooling water temperature sensor 26 is calculated by a map or a mathematical expression. After that, the routine proceeds to step 104, where the basic torque margin value is multiplied by various correction coefficients (vehicle speed correction coefficient, cooling water temperature correction coefficient, atmospheric pressure correction coefficient, steering steering angle correction coefficient, etc.) and alcohol concentration correction coefficient. By obtaining the torque margin value, a corrected torque margin value is set according to the alcohol concentration of the fuel and the coolant temperature.
Torque margin value = basic torque margin value x various correction factors x alcohol concentration correction factor

  In the present embodiment described above, the torque margin value is corrected in accordance with the alcohol concentration of the fuel and the coolant temperature (engine temperature information). Therefore, the torque and combustion stability of the engine 11 are controlled according to the alcohol concentration of the fuel and the engine temperature. Accordingly, the torque margin value can be corrected and the torque margin value can be set to an appropriate value with high accuracy. Thus, even if the torque and combustion stability of the engine 11 change depending on the alcohol concentration of the fuel and the engine temperature, the torque margin value of the torque reserve control performed during the idling operation is changed to the alcohol concentration of the fuel and the engine temperature. It is possible to set an appropriate value in accordance with it, to improve the torque control accuracy, and to stabilize the idle rotation speed.

  In the above embodiment, the alcohol concentration correction coefficient corresponding to the alcohol concentration of the fuel and the coolant temperature is calculated, and the basic torque margin value is multiplied by this alcohol concentration correction factor to obtain the final torque margin value. However, the method of correcting the torque margin value according to the alcohol concentration of the fuel and the cooling water temperature may be changed as appropriate.For example, the alcohol concentration correction amount according to the alcohol concentration of the fuel and the cooling water temperature is calculated. The final torque margin value may be obtained by adding (or subtracting) this alcohol concentration correction amount to the basic torque margin value.

  Alternatively, the basic torque margin value is calculated using a map or a mathematical formula that calculates the basic torque margin value using the alcohol concentration of the fuel, the coolant temperature, and the engine operating state (for example, engine speed and load) as parameters. Anyway.

  In the above embodiment, the coolant temperature detected by the coolant temperature sensor 26 is used as the engine temperature information. However, the oil temperature detected by the oil temperature sensor may be used instead of the coolant temperature. Alternatively, the engine temperature may be estimated based on at least one of the cooling water temperature and the oil temperature.

  In the above embodiment, the torque margin value is corrected according to both the alcohol concentration of the fuel and the engine temperature (for example, the coolant temperature). However, the torque margin value is corrected only according to the alcohol concentration of the fuel. Anyway.

  In the above embodiment, the alcohol concentration sensor 34 detects the alcohol concentration of the fuel. However, in the case of a system that does not include the alcohol concentration sensor 34, for example, an air-fuel ratio feedback correction amount, a deviation of the air-fuel ratio. The alcohol concentration of the fuel may be estimated based on at least one of the amount, the combustion stability (engine rotation fluctuation), the engine torque, the fuel pressure increase rate at the time of high temperature start, and the like.

  Further, in the above embodiment, torque reserve control is performed in which the throttle opening is offset in the torque increasing direction by a predetermined torque margin value during idle operation, and the torque increase is canceled by offsetting the ignition timing in the torque decreasing direction. However, the present invention is not limited to this. For example, in the case of a system equipped with an ISC valve (idle speed control valve), the ISC valve opening is increased by a predetermined torque margin during idle operation. The torque reserve control may be performed so that the torque increase is canceled by offsetting the increase in torque to the torque decrease direction of the ignition timing.

  Further, torque reserve control is performed so that the torque increase due to the offset of the throttle opening or the ISC valve opening is canceled by the offset in the torque decreasing direction of the torque control parameter (for example, intake valve timing, etc.) other than the ignition timing. May be.

  In addition, the present invention is not limited to the intake port injection type engine as shown in FIG. 1, but includes an in-cylinder injection type engine, and both an intake port injection fuel injection valve and an in-cylinder injection fuel injection valve. It can also be applied to dual-injection engines.

It is a schematic block diagram of the whole engine control system in one Example of this invention. It is a figure explaining the relationship between the alcohol concentration of a fuel, cooling water temperature, and engine characteristics (torque and combustion stability). It is a block diagram which shows roughly the function of torque reserve control. (A) is a figure which shows notionally an example of the map of the alcohol concentration correction coefficient in a high temperature area | region, (b) is a figure which shows notionally an example of the map of the alcohol concentration correction coefficient in a low temperature area | region. It is a block diagram explaining the function of a torque reserve control part. It is a flowchart explaining the flow of a process of a torque margin value setting routine.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Engine (internal combustion engine), 12 ... Intake pipe, 16 ... Throttle valve, 21 ... Fuel injection valve, 22 ... Spark plug, 23 ... Exhaust pipe, 26 ... Cooling water temperature sensor (engine temperature information determination means), 30 ... Fuel Tank, 31 ... Fuel pump, 34 ... Alcohol concentration sensor (alcohol concentration determination means), 35 ... ECU, 36 ... Alcohol concentration correction coefficient setting unit, 37 ... Torque margin value correction unit (torque margin value correction unit), 38 ... Torque Reserve control section

Claims (4)

During the idling operation of the internal combustion engine, torque reserve control is performed to offset the intake air amount control parameter in the torque increasing direction by a predetermined torque margin value and offset the torque control parameter in the torque decreasing direction so as to cancel the torque increase. In a control device for an internal combustion engine to perform,
Alcohol concentration determination means for detecting or estimating the alcohol concentration of fuel supplied to the internal combustion engine;
A control apparatus for an internal combustion engine, comprising: torque margin value correcting means for correcting the torque margin value according to the alcohol concentration. Engine temperature information determination means for detecting or estimating the temperature of the internal combustion engine or information related thereto (hereinafter referred to as “engine temperature information”);
2. The control apparatus for an internal combustion engine according to claim 1, wherein the torque margin value correcting means corrects the torque margin value in consideration of the engine temperature information in addition to the alcohol concentration.   3. The internal combustion engine according to claim 2, wherein the torque margin value correcting means corrects the torque margin value so that the torque margin value decreases as the alcohol concentration increases when the engine temperature information is in a predetermined high temperature range. Control device.   The said torque margin value correction | amendment means correct | amends so that the said torque margin value may be enlarged, so that the said alcohol concentration becomes high, when the said engine temperature information is a predetermined | prescribed low temperature area | region. Control device for internal combustion engine.

Images