JP4055542B2 - Fuel property discrimination device for internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fuel property determination device for an internal combustion engine.
[0002]
[Prior art]
In an internal combustion engine such as an automobile engine, a fuel having a property corresponding to the use state of the engine is used. For example, light fuel with high volatility is used in winter and cold regions, and heavy fuel with low volatility is used in summer and warm regions. In addition, fuels having different octane numbers may be selected depending on the driver of the automobile.
[0003]
In an internal combustion engine, the optimal fuel injection amount, fuel injection timing, ignition timing, and the like differ in obtaining a good engine operation due to differences in fuel properties such as volatility and octane number of fuel used. Therefore, in order to obtain good engine operation, it is preferable to determine the properties of the fuel used in the internal combustion engine and control the fuel injection amount, fuel injection timing, ignition timing, and the like according to the fuel properties.
[0004]
As a method for discriminating the fuel property of an internal combustion engine, for example, methods disclosed in the following Patent Documents 1 and 2 are known.
[Patent Document 1]
Paying attention to the fact that the volatility of the fuel affects the air-fuel ratio of the internal combustion engine during a predetermined period after the fuel injection amount increase at the time of acceleration, Judge that the fuel being used is a heavy fuel with low volatility. On the other hand, if the air-fuel ratio is not lean for a predetermined time or more during the above period, it is determined that the fuel being used is normal (light fuel). As described above, the property determination according to the volatility of the fuel can be performed based on the air-fuel ratio during the predetermined period after the fuel injection amount increase at the time of acceleration. The lower the fuel volatility, the fuel at the time of acceleration. This is because the volatilization of the injected fuel is difficult to proceed after the injection amount increase, and the air-fuel ratio of the internal combustion engine tends to be lean. Whether or not the air-fuel ratio of the internal combustion engine is lean can be determined based on a detection signal from an oxygen sensor that outputs a rich signal or a lean signal in accordance with the oxygen concentration of exhaust gas in the engine.
[0005]
[Patent Document 2]
Regarding knocking of an internal combustion engine, when the frequency of occurrence is large, it is determined that the fuel used in the engine is a high octane number with high knock resistance, and when the frequency of occurrence is low, it is used in the engine. It is judged that the fuel is low octane number with low knock resistance. Note that the frequency of occurrence of knocking in the internal combustion engine can be determined based on a detection signal of a knock sensor that outputs a signal corresponding to the occurrence of knocking.
[0006]
[Patent Document 1]
JP-A-4-58051
[Patent Document 2]
JP-A 63-176737
[0007]
[Problems to be solved by the invention]
However, none of the fuel property discrimination methods disclosed in Patent Documents 1 and 2 can complete the fuel property discrimination early after the start of the internal combustion engine.
[0008]
That is, in the method of the cited document 1, it is necessary to increase the fuel injection amount accompanying the acceleration in order to discriminate the fuel property. However, such acceleration is rarely performed immediately after the start of the engine, and usually the engine is started. This is done after the car starts running after completion. For this reason, the fuel property cannot be determined from the start of the internal combustion engine to the acceleration state, and it is difficult to complete the determination early after the start of the engine.
[0009]
Further, in the method of the cited document 2, it is necessary to be in an engine warm-up completion state in which knocking may occur in order to determine the fuel property, and a predetermined number for knowing the occurrence frequency of knocking after the engine warm-up is completed. A period is also required. For this reason, the fuel property cannot be determined from the start of the internal combustion engine until the warm-up is completed and the predetermined period elapses, and it is difficult to complete the determination early after the start of the engine. become.
[0010]
By the way, from the start of the engine start until the fuel property determination is completed, it is possible to perform optimum engine operation control according to the fuel property, for example, fuel injection amount control, fuel injection timing control, ignition timing control, etc. Therefore, there is a possibility that engine operation control inappropriate for the actual fuel property is performed. Therefore, if the determination of the fuel properties is not completed early after the start of the engine start, the time until the engine operation control suitable for the actual fuel properties is performed after the start of the engine start becomes long. It is disadvantageous for good engine operation.
[0011]
The present invention has been made in view of such circumstances, and an object of the present invention is to provide a fuel property determination device for an internal combustion engine that can determine the fuel property at an early stage after the start of the engine.
[0012]
[Means for Solving the Problems]
  In the following, means for achieving the above object and its effects are described.
  In order to achieve the above object, according to the first aspect of the invention, from the start of engine startAt the time when a predetermined time has passedOf fine particles mainly composed of soot in the exhaustamountAnd determining means for determining the properties of the fuel used in the internal combustion engineThe predetermined time is longer than the time required for the amount of the fine particles to reach the peak value..
[0015]
  When the internal combustion engine is started, the fuel supplied by injection exists in the combustion chamber in a liquid state, and combustion is performed in this state, thereby generating fine particles mainly composed of soot.The amount of fine particles generated in the exhaust gas after starting the engine gradually decreases after rising to the peak value. The decreasing tendency after reaching the peak value of the amount of fine particles varies depending on the fuel properties. Therefore, whether the engine startsAboveFine particlesofThe amount of time is longer than it takes to reach the peak valuePredeterminedFine particles in the exhaust at the timeofBased on the quantity, it is possible to accurately determine the properties of the fuel used in the internal combustion engine.Thus, by determining the fuel property using the fine particles generated at the time of starting the engine, the fuel property can be determined at an early stage after the start of the engine.
[0016]
  Claim2In the described invention,The main component is soot in the exhaust when a predetermined time has elapsed since the start of engine startup.Fine particlesofBased on quantityUsed in internal combustion enginesDiscrimination of fuel properties according to the octane number of the fuelThe discriminating means is provided.
[0017]
  In the fuel of an internal combustion engine, an aromatic component (aroma component) is added to increase the octane number. And in the exhaust after starting the engineThe main ingredient is salmonAs for the fine particles, the more aromatic components (aroma content) contained in the fuel used in the internal combustion engine, the more gradual the decrease tendency after reaching the peak value of the fine particle amount. Fine particles are generated. This is because in aromatic components, the benzene ring is stably bonded, so it becomes difficult for carbon and oxygen to bond due to the decomposition of the benzene ring during combustion of the fuel. This is because the generation is difficult to converge. Therefore, the higher the octane number fuel with more aromatic components, the greater the amount of particulates in the exhaust when a predetermined time has elapsed since the start of engine start. It can be carried out.Thus, by determining the fuel property using the fine particles generated at the time of starting the engine, the fuel property can be determined at an early stage after the start of the engine.
[0018]
  Claim3In the described inventionThe machineIn the exhaust after startingThe main ingredient is salmonBased on the peak amount of fine particles,Used in internal combustion enginesDetermining fuel propertiesA discrimination means was provided.
[0019]
  Generated in the exhaust after starting the engineThe main ingredient is salmonThe amount of fine particles gradually decreases after rising to the peak value. The peak value of such fine particle amount varies depending on the fuel properties. Therefore, the properties of the fuel used in the internal combustion engine can be accurately determined based on the peak value of the amount of fine particles in the exhaust gas after starting the engine.Thus, by determining the fuel property using the fine particles generated at the time of starting the engine, the fuel property can be determined at an early stage after the start of the engine.
[0020]
  Claim4In the described invention, the claims3In the described invention, the discriminating means discriminates the fuel property according to the volatility of the fuel based on the peak value.
  In the fuel of an internal combustion engine, the heavier the fuel with lower volatility, the more difficult the volatilization of the injected fuel proceeds, so the combustion in the state where the liquid fuel is present in the combustion chamber is likely to be performed, and the combustion The amount of generated fine particles increases. Therefore, the heavier fuel with lower volatility has a higher peak value of the amount of particulates in the exhaust after the start of the engine, and the fuel property can be accurately determined according to volatility based on this peak value. .
[0021]
  Claim5In the described inventionThe machineDuring the exhaust from the start of SekiThe main ingredient is salmonBased on time until fine particles are generatedUsed in internal combustion enginesDetermining fuel propertiesA discrimination means was provided.
[0022]
  Generated in the exhaust after starting the engineThe main ingredient is salmonThe amount of fine particles gradually decreases after rising to the peak value. The generation start time of such fine particles varies depending on the fuel properties. Therefore, the properties of the fuel used in the internal combustion engine can be accurately determined based on the time from the start of the engine to the generation of fine particles in the exhaust.Thus, by determining the fuel property using the fine particles generated at the time of starting the engine, the fuel property can be determined at an early stage after the start of the engine.
[0023]
  Claim6In the described invention, the claims5In the described invention, the discriminating means discriminates the fuel property according to the volatility of the fuel based on the time.
  In the fuel of internal combustion engines, the heavier the fuel with lower volatility, the more difficult the volatilization of the fuel supplied by the injection progresses.Therefore, good combustion is slowed down and the temperature in the combustion chamber is difficult to rise. The generation time of fine particles due to combustion is also delayed. Therefore, the heavier fuel with lower volatility has a longer time from the start of the engine to the generation of fine particles, and based on this time, the fuel property can be accurately determined according to the volatility.
[0024]
  Claim7In the described invention, claims 1 to6In the invention according to any one of the above, the discrimination meansSaidFine particlesofThe fuel property is determined based on the detection signal from the detecting means for detecting the amount.
[0025]
According to the above configuration, since the amount of particulates in the exhaust gas can be monitored by the detection signal from the detection means, the generation mode of particulates in the exhaust gas from the start of the engine is accurately detected, and the fuel property is accurately discriminated. Can be.
[0026]
  Claim8In the described invention, claims 1 to7The gist of the invention is that the internal combustion engine is a direct injection internal combustion engine that directly injects fuel into the combustion chamber.
[0027]
In a cylinder injection internal combustion engine, the time from when fuel is injected into the combustion chamber to when combustion starts is shorter than that of an internal combustion engine that injects fuel into the intake passage. For this reason, it becomes difficult for the fuel injected and supplied into the combustion chamber to be volatilized by the time of ignition, and it tends to exist in a liquid state, and the generation of fine particles due to combustion in that state is likely to occur. Therefore, it becomes easy to determine the fuel property based on the generation mode of the particulates in the exhaust after starting the engine.
[0028]
  Claim9In the described invention, claims 1 to8In the invention according to any one of the above, the determining means determines the fuel property at least when the engine is started from a cold state.
[0029]
When the engine is started from a cold state, the volatilization of the injected fuel in the combustion chamber is difficult to proceed. Therefore, combustion in the state where the liquid fuel is present in the combustion chamber is likely to occur, and particulates are likely to be generated in the exhaust gas. Accordingly, when the fuel property is determined based on the generation mode of the particulates in the exhaust gas when the engine is started from the cold state, the determination becomes easy.
[0030]
DETAILED DESCRIPTION OF THE INVENTION
[First Embodiment]
Hereinafter, a first embodiment in which the present invention is applied to an in-cylinder injection spark ignition engine for an automobile will be described with reference to FIGS.
[0031]
In the engine 1 shown in FIG. 1, an ignition plug is used for an air-fuel mixture comprising air sucked from the intake passage 2 into the combustion chamber 3 and fuel injected from the fuel injection valve 4 into the combustion chamber 3. Ignition by 5 is performed. When the air-fuel mixture in the combustion chamber 3 is combusted by this ignition, the piston 6 reciprocates due to the combustion energy at that time, and the air-fuel mixture after combustion is sent to the exhaust passage 7 as exhaust gas.
[0032]
The exhaust gas of the engine 1 contains fine particles (particulates) whose main component is soot. Such particulates are generated when combustion is performed in a state where liquid fuel is present in the combustion chamber 3 such as when the engine is started, and is sent to the exhaust passage 7 together with the exhaust gas. The amount of particulates in the exhaust is detected by a particulate detection sensor 34 provided in the exhaust passage 7.
[0033]
As the particulate detection sensor 34, for example, a laser beam is irradiated so as to pass through the exhaust gas in the exhaust passage 7, and the laser beam after passing through the exhaust gas is received, and a signal corresponding to the transmittance of the laser beam is received. Is used. The signal output from the particulate detection sensor 34 corresponds to the amount of particulates in the exhaust.
[0034]
On the other hand, the reciprocating movement of the piston 6 based on the combustion energy of the air-fuel mixture is converted into rotation of the crankshaft 9 that is the output shaft of the engine 1 by the connecting rod 8. When the crankshaft 9 rotates, a signal corresponding to the rotation is output from the crank position sensor 10, and the rotation is transmitted to the tire of the automobile via a transmission or the like. When the engine 1 is driven as described above, the engine 1 is cooled by the cooling water, and the temperature of the cooling water is detected by the water temperature sensor 36.
[0035]
In the intake passage 2, a throttle valve 11 that opens and closes to adjust the amount of air sucked into the combustion chamber 3 (intake air amount) is provided at an upstream portion thereof, and the intake passage 2 is disposed downstream of the throttle valve 11. A vacuum sensor 12 for detecting the internal pressure (intake pressure) is provided. The opening degree of the throttle valve 11 (throttle opening degree) is adjusted according to the depression amount (accelerator depression amount) of the accelerator pedal 13 operated by the driver of the automobile. The accelerator depression amount is detected by the accelerator position sensor 14, and the throttle opening is detected by the throttle position sensor 15.
[0036]
In the engine 1, the fuel injection amount and injection timing from the fuel injection valve 4, the ignition timing of the spark plug 5, and the opening degree of the throttle valve 11 are controlled by an electronic control device 35 mounted on the automobile to control the operation of the engine 1. Done through. The electronic control unit 35 receives detection signals from various sensors such as the crank position sensor 10, the vacuum sensor 12, the accelerator position sensor 14, the throttle position sensor 15, the particulate detection sensor 34, and the water temperature sensor 36.
[0037]
Next, the calculation procedure of the ignition timing command value used for the ignition timing control of the engine 1 will be described with reference to the flowchart of FIG. 2 showing the ignition timing command value calculation routine. This ignition timing command value calculation routine is executed through the electronic control unit 35 by, for example, an angle interruption for each predetermined crank angle.
[0038]
In the ignition timing command value calculation routine, first, whether or not the high octane flag F1 used to determine whether or not the fuel used in the engine 1 is high octane number fuel is “1 (high octane number)”. It is determined whether or not (S101).
[0039]
If the determination is negative, the ignition timing command value is calculated using a map for low octane (S103). That is, the base value of the ignition timing command value is calculated with reference to the map based on the engine rotational speed and the engine load, and the ignition timing command value is calculated by adding the advance / retard angle correction according to the presence or absence of knocking to the base value. Is calculated. Based on the ignition timing command value calculated in this manner, the ignition timing is controlled through the electronic control unit 35.
[0040]
The engine rotation speed is obtained based on a detection signal from the crank position sensor 10. The engine load is obtained based on a parameter related to the intake air amount of the engine 1 and the engine speed. The parameters related to the intake air amount are obtained based on the accelerator depression amount obtained from the detection signal of the accelerator position sensor 14, the throttle opening obtained based on the detection signal of the throttle position sensor 15, and the detection signal of the vacuum sensor 12. Intake pressure or the like is used.
[0041]
On the other hand, if the determination in step S101 is affirmative, an ignition timing command value is calculated using a map for high octane (S102). That is, the base value of the ignition timing command value is calculated with reference to the map based on the engine rotational speed and the engine load, and the ignition timing command value is calculated by adding the advance / retard angle correction according to the presence or absence of knocking to the base value. Is calculated. The ignition timing command value calculated in this way is an advanced value than when the ignition timing command value is calculated using the low-octane map under the same engine operating condition as this time. .
[0042]
Therefore, for the ignition timing of the engine 1, the ignition timing command value calculated using the low-octane map is controlled by controlling the ignition timing based on the ignition timing command value calculated using the high-octane map. Therefore, the ignition timing is adjusted to be more advanced than when the ignition timing is controlled. This is because when high-octane fuel is used, it becomes difficult to knock when the ignition timing is advanced. Therefore, it is possible to increase the engine output by advancing the ignition timing as much as the knocking resistance is improved. This is because it is preferable.
[0043]
As described above, by performing the ignition timing control according to the octane number of the fuel, it becomes possible to maximize the output performance of the engine 1 while accurately suppressing knocking.
[0044]
Next, the property determination of the fuel used in the engine 1, that is, the property determination of the fuel according to the octane number will be described with reference to FIGS.
FIG. 3 is a time chart showing the transition of the particulate amount in the exhaust gas after the start of the engine 1 is started. The particulate amount is obtained from the detection signal of the particulate detection sensor 34.
[0045]
As shown in the figure, when fuel is injected and supplied into the combustion chamber 3 after the start of the engine 1, combustion is performed in a state where liquid fuel is present in the combustion chamber 3, and the amount of particulates in the exhaust gas Gradually increases to reach the peak value. When the vaporization of the liquid fuel is promoted by the heat during combustion and the liquid fuel in the combustion chamber 3 decreases, the amount of particulates in the exhaust gas gradually decreases from the peak value.
[0046]
In the fuel of the engine 1, an aromatic component (aroma component) is added to increase the octane number. The more this aromatic component is contained in the fuel, in other words, the higher the octane number, the more gradually the particulate amount contained in the exhaust gas reaches the peak value after the start of the engine start. This is because in aromatic components, since the benzene ring is stably bonded, the bond between carbon and oxygen accompanying the decomposition of the benzene ring during combustion of the fuel is difficult to proceed. This is because the generation is difficult to converge.
[0047]
In the present embodiment, the characteristic that the decreasing amount of the particulate amount after the particulate amount contained in the exhaust gas reaches the peak value after the start of the engine starts is different depending on the octane number of the fuel. Determine the fuel properties.
[0048]
That is, after the start of the engine, when a predetermined time a longer than the time required for the particulate amount to reach the peak value has elapsed (timing T1), the particulate amount P in the exhaust gas has a predetermined determination value b. If it is greater, the fuel used in the engine 1 is judged to have a high octane number. On the other hand, when the particulate amount P is equal to or less than the determination value b, it is determined that the fuel used in the engine 1 has a low octane number.
[0049]
As described above, the characteristics of the fuel used in the engine 1 (octane number) is determined based on the generation mode of the particulates generated in the exhaust when the engine starts. The fuel properties can be determined. As a result, engine operation control (ignition timing control) according to the octane number of the fuel can be executed at an early stage after the start of the engine start, and the engine start is to maximize the output performance of the engine 1 while suppressing knocking. It can be realized early after the start.
[0050]
FIG. 4 is a flowchart showing a fuel property determination routine for determining the fuel property according to the octane number and setting the high octane flag F1 according to the determination result. This fuel property determination routine is executed through the electronic control unit 35 by, for example, a time interruption every predetermined time.
[0051]
In the fuel property determination routine, it is determined whether or not the engine 1 has started to start based on the engine speed or the like (S201).
If the determination is affirmative, the predetermined time a is set as a time longer than the time required for the particulate amount to reach the peak value based on the cooling water temperature at the start of engine start obtained from the detection signal of the water temperature sensor 36. Is set (S201). The predetermined time a set in this way becomes a shorter value as the cooling water temperature (engine temperature) at the time of starting the engine is higher. This is because the higher the cooling water temperature at the start of the engine, the easier the vaporization of the fuel proceeds when the fuel is injected into the combustion chamber 3 at the start of the engine start, and the change in the amount of particulates after the start of the engine starts. This is to make it possible to appropriately determine the fuel property according to the octane number regardless of this, although it is accelerated as a whole.
[0052]
Subsequently, the determination value b for determining whether or not the fuel has a high octane number is calculated based on the coolant temperature (engine temperature) at the start of engine start (S203). The determination value b calculated in this way becomes smaller as the cooling water temperature is higher. This is because the higher the coolant temperature at the start of engine start, the easier the vaporization of the fuel progresses when the fuel is injected into the combustion chamber 3 at the start of engine start, and the liquid that exists in the combustion chamber 3 at the time of combustion. This is because the amount of particulates generated in the exhaust gas is reduced when the predetermined time a elapses when the amount of fuel is reduced.
[0053]
Thereafter, on condition that the elapsed time t from the start of engine start is the predetermined time a (S204: YES), it is determined whether or not the particulate amount P is larger than the determination value b (S205). . If the determination is affirmative, it is determined that the fuel used in the engine 1 has a high octane number, and the high octane flag F1 is set to “1 (high octane number)” (S206).
[0054]
The high octane flag F1 is reset to “0 (low octane number)” every time the engine is stopped. Therefore, when the fuel used in the engine 1 has a low octane number, when the elapsed time t from the start of the engine reaches the predetermined time a (S204: YES), the particulate amount P is determined as the determination value b. The high octane flag F1 remains “0 (low octane number)” as follows.
[0055]
As described above, the high octane flag F1 is set to “1 (high octane number)” or “0 (low octane number)” at an early stage after the start of the engine according to the octane number of the fuel used in the engine 1, and its value. Accordingly, appropriate ignition timing control corresponding to the octane number of the fuel is executed.
[0056]
According to the embodiment described in detail above, the following effects can be obtained.
(1) When the engine is started, the fuel supplied by injection exists in the combustion chamber 3 in a liquid state, and particulates are generated by combustion in that state. The mode of generation of such particulates from the start of engine start differs depending on the octane number of the fuel used in the engine 1. In other words, the amount of particulates generated in the exhaust gas after starting the engine gradually increases after reaching the peak value, but this decrease in the amount of particulates increases the aromatic component (aromatic component) in order to increase the octane number. ), The more fuel is added, the more moderate. Therefore, if the fuel used in the engine 1 has a high octane number, the particulate amount P when the elapsed time t from the start of the engine reaches the predetermined time a is greater than the determination value b. Therefore, based on whether the particulate amount P is greater than the determination value b, whether high-octane fuel is used early after the start of the engine or whether low-octane fuel is used Can be accurately determined.
[0057]
(2) As engine operation control according to the property of the fuel used in the engine 1, ignition timing control according to the octane number of the fuel is performed. That is, when high-octane fuel is used, knocking is less likely to occur when the ignition timing is advanced than when low-octane fuel is used. It is controlled to the advance side rather than the hour. Thus, by performing the ignition timing control according to the octane number of the fuel, it is possible to maximize the output performance of the engine 1 while suppressing knocking. In addition, since the determination of the octane number of the fuel can be completed early after the start of the engine start, the ignition timing control according to the octane number of the fuel in order to maximize the output performance of the engine 1 while suppressing knocking, This can be realized early after the start of the engine.
[0058]
(3) Since the particulate quantity in the exhaust gas can be monitored by the detection signal from the particulate detection sensor, the mode of generation of the particulate quantity in the exhaust gas after the start of engine start is accurately detected, and the fuel property (octane number) ) Can be made accurate.
[0059]
(4) In the in-cylinder injection type engine 1, the time from when fuel is injected into the combustion chamber 3 to when combustion starts is shorter than that of an engine that supplies fuel to the intake passage 2. For this reason, it becomes difficult for the fuel injected and supplied into the combustion chamber 3 to be volatilized by the time of ignition, and it tends to exist in a liquid state, and particulates are easily generated due to combustion in this state. Accordingly, it becomes easy to determine the fuel property (octane number) based on the particulate amount in the exhaust gas when the predetermined time a has elapsed after the start of the engine start.
[0060]
(5) When the engine is started from a cold state, the volatilization of the injected fuel in the combustion chamber 3 is difficult to proceed. Therefore, combustion in a state where liquid fuel is present in the combustion chamber 3 is likely to occur, and the particulates are generated. It tends to occur. Therefore, when starting the engine from a cold state, it becomes easy to determine the fuel property (octane number) based on the particulate amount in the exhaust when the predetermined time a has elapsed from the start of the start.
[0061]
[Second Embodiment]
Next, a second embodiment of the present invention will be described with reference to FIGS.
In this embodiment, the fuel property is determined according to the volatility of the fuel used in the engine 1, and the fuel injection amount control and the fuel injection timing control according to the fuel property (volatility) are performed.
[0062]
FIG. 5 is a flowchart showing a fuel injection amount command value calculation routine for calculating a fuel injection amount command value used for fuel injection amount control of the engine 1. This fuel injection amount command value calculation routine is executed through an electronic control unit 35, for example, by an angle interruption for each predetermined crank angle.
[0063]
In the fuel injection amount calculation routine, the fuel injection amount command value is calculated by adding corrections with various correction values such as a post-start increase value to the base value of the fuel injection amount obtained from the engine speed and the engine load. Based on the fuel injection amount command value calculated in this way, the fuel injection amount is controlled through the electronic control unit 35.
[0064]
The post-start increase value is for realizing stable operation after completion of engine start, and is obtained based on the coolant temperature at the start of engine start, and gradually increases with the passage of time after the start of engine starts. This value is reduced to “0”. Therefore, the fuel injection amount increase correction based on the post-start increase value becomes the maximum after the engine start is completed, and is gradually decreased to “0” as time elapses thereafter.
[0065]
In the process of step S301 in the fuel injection amount command value calculation routine, the heavy flag F2 used to determine whether or not the fuel used in the engine 1 is a heavy fuel with low volatility is “1 ( Heavy)). If the determination is affirmative, the post-startup increase value is adjusted to the increase side (S302).
[0066]
The adjustment of the increase value after start-up includes switching the increase value after start-up to a different value depending on whether the fuel is heavy (“F = 1”) or light (“F = 0”), or the fuel is heavy. It is conceivable to correct the increase value after the start depending on whether it is light.
[0067]
It should be noted that it is preferable to increase the post-startup increase value as the heavier fuel having lower volatility as shown in FIG. This is because when the fuel used in the engine 1 is heavy and has low volatility, the fuel supplied to the combustion chamber 3 is less likely to volatilize and the engine operation is stabilized after the start is completed. This is because it is preferable to increase the fuel injection amount increase correction based on the increase amount after starting.
[0068]
For this reason, the increase value after starting is set to a larger value when heavy fuel with low volatility is used than when light fuel with high volatility is used. Further, when the fuel injection amount command value is calculated in consideration of the increase value after the start (S303), when the heavy fuel is used for the command value, it is more than when the light fuel is used. It becomes the value on the increase side. Accordingly, the fuel injection amount of the engine 1 from the completion of the engine start until the post-start increase value becomes “0” is increased when the heavy fuel is used rather than when the light fuel is used. It becomes a trend.
[0069]
As described above, by controlling the increase in the fuel injection amount after completion of the engine start according to the volatility of the fuel, the increase can be made appropriate for obtaining a stable engine operation after the completion of the engine start. .
[0070]
FIG. 7 is a flowchart showing a fuel injection timing command value calculation routine for calculating a fuel injection timing command value used for fuel injection timing control of the engine 1. This fuel injection timing command value calculation routine is executed through an electronic control unit 35 by, for example, an angle interruption for each predetermined crank angle.
[0071]
In the fuel injection timing command value calculation routine, when the engine 1 is not in the stratified charge combustion operation (S401: NO), or when the heavy flag F2 is “0 (light)” (S402: NO), it is as usual. A fuel injection timing command value is calculated (S404). Here, for example, when the stratified charge combustion operation is being performed (S401: YES) and the heavy flag F2 is “0 (light)” (S402: NO), the stratified charge combustion is supported based on the engine speed and the engine load. The fuel injection timing command value is calculated with reference to the light quality map. Based on the fuel injection timing command value calculated in this way, the fuel injection timing at the time of stratified combustion is controlled through the electronic control unit 35.
[0072]
On the other hand, when the engine 1 is in the stratified charge combustion operation (S401: YES) and the heavy flag F2 is “1 (heavy)” (S402: YES), the heavy load corresponding to the stratified charge combustion is used. The fuel injection timing command value is calculated using the map (S403). That is, the fuel injection timing command value is calculated with reference to the map based on the engine speed and the engine load.
[0073]
At the time of stratified combustion operation, it is necessary to perform ignition in a state in which an air-fuel mixture containing combustible fuel (combustible air-fuel mixture) exists around the spark plug 5. The slower the quality fuel. This is because the heavier the fuel, the longer it takes for the fuel injected into the combustion chamber 3 to volatilize, and it takes time for the amount of vaporized fuel around the spark plug 5 to reach an ignitable value after fuel injection. It is. For this reason, the fuel injection timing command value during the stratified combustion operation is set to a more advanced value for a heavier fuel with lower volatility as shown in FIG. 8, and the time from fuel injection to ignition is made longer. It is preferable to ensure good engine operation in the stratified charge combustion operation after starting the engine.
[0074]
Therefore, the fuel injection timing command value at the time of stratified combustion operation is a value on the advance side when heavy fuel is used ("F = 1") than when light fuel is used. Will come to be. As a result, the fuel injection timing during the stratified combustion operation is more advanced when the heavy fuel is used than when the light fuel is used.
[0075]
As described above, by performing the fuel injection timing control during the stratified combustion operation according to the volatility of the fuel, the fuel injection timing can be made appropriate for good engine operation during the stratified combustion operation. .
[0076]
Next, characteristic determination of the fuel used in the engine 1, that is, characteristic determination of the fuel according to volatility will be described with reference to FIGS.
FIG. 10 is a time chart showing the transition of the particulate amount in the exhaust gas after the start of the engine 1 is started.
[0077]
As shown in the figure, when fuel is injected and supplied into the combustion chamber 3 after the start of the engine 1, combustion is performed in a state where liquid fuel is present in the combustion chamber 3, and the amount of particulates in the exhaust gas Gradually increases to reach the peak value. When the vaporization of the liquid fuel is promoted by the heat during combustion and the liquid fuel in the combustion chamber 3 decreases, the amount of particulates in the exhaust gas gradually decreases from the peak value.
[0078]
As the fuel of the engine 1 becomes heavier and less volatile, the peak value Pmax of the particulate amount after the start of the engine increases. This is because, as the volatility of the fuel is lower, the volatilization of the fuel injected and supplied into the combustion chamber 3 after the engine start is less likely to proceed. This is because the amount of particulates generated by the combustion increases.
[0079]
In the present embodiment, the fuel property is determined according to the volatility by utilizing the characteristic that the peak value Pmax of the particulate amount in the exhaust gas after the start of the engine varies depending on the volatility of the fuel.
[0080]
That is, after the start of the engine, when the particulate amount reaches a peak value (timing T2), if the peak value Pmax is equal to or greater than the determination value c, the fuel used in the engine 1 is volatile. It is judged that it is a heavy fuel with a low level. On the other hand, when the peak value Pmax is less than the determination value c, it is determined that the fuel used in the engine 1 is a light fuel with high volatility.
[0081]
As described above, by determining the property (volatility) of the fuel used in the engine 1 based on the generation mode of the particulates generated in the exhaust at the start of the engine start, the volatility occurs early after the start of the engine. The fuel property can be determined according to the conditions. As a result, engine operation control (fuel injection amount control, fuel injection timing control) according to the volatility of the fuel can be executed at an early stage after the start of the engine. That is, an increase in the fuel injection amount corresponding to the increase value after the engine start after completion of the engine start is appropriate according to the volatility of the fuel, and ensuring stable engine operation after the engine start is completed after the engine start is started. It can be realized early. In addition, the fuel injection timing is appropriate according to the volatility of the fuel at the time of stratified combustion operation after the start of engine start, and good engine operation at the time of stratified charge combustion operation is obtained early after the start of engine start be able to.
[0082]
FIG. 9 is a flowchart showing a fuel property determination routine for determining the fuel property according to volatility and setting the heavy flag F2 according to the determination result. This fuel property determination routine is executed through the electronic control unit 35 by, for example, a time interruption every predetermined time.
[0083]
In the fuel property determination routine, it is first determined whether or not the engine 1 has started (S501). If the determination is affirmative, the determination value c for determining whether or not the fuel is heavy fuel with low volatility is calculated based on the coolant temperature (engine temperature) at the start of engine start and the like. (S502). The determination value c calculated in this way becomes smaller as the cooling water temperature is higher. This is because the higher the coolant temperature at the start of engine start, the easier the vaporization of the fuel proceeds when the fuel is injected into the combustion chamber 3 at the start of engine start, and the liquid that exists in the combustion chamber 3 at the time of combustion. This is because the amount of fuel decreases and the peak value of the particulate amount decreases.
[0084]
Thereafter, based on whether or not the transition of the particulate amount has shifted from rising to falling, it is determined whether or not the particulate amount has reached a peak value (S503). When it is determined that the particulate amount has reached the peak value, it is determined whether the particulate amount peak value Pmax is equal to or greater than the determination value c (S504). If the determination is affirmative, it is determined that the fuel used in the engine 1 is a heavy fuel with low volatility, and the heavy flag F2 is set to “1 (heavy)” (S505).
[0085]
The heavy flag F2 is reset to “0 (low octane number)” every time the engine is stopped. Therefore, when the fuel used in the engine 1 is a light fuel with high volatility, when the particulate amount in the exhaust after the start of the engine reaches a peak value (S503: YES), the peak value Pmax Becomes less than the judgment value c, and the heavy flag F2 remains “0 (light)”.
[0086]
Thus, the heavy flag F2 is set to “1 (heavy)” or “0 (light)” early after the start of the engine according to the volatility of the fuel used in the engine 1, and its value Accordingly, as described above, appropriate fuel injection amount control and fuel injection timing control corresponding to the volatility of the fuel are executed.
[0087]
According to the embodiment described in detail above, the following effects can be obtained.
(6) The amount of particulates generated in the exhaust gas after starting the engine gradually increases after reaching the peak value. The peak value of such particulate amount is the more heavy fuel with low volatility. growing. Therefore, if the fuel used in the engine 1 is heavy, the peak value Pmax of the particulate quantity is equal to or greater than the determination value c. Therefore, based on whether the peak value Pmax is equal to or greater than the determination value c, it is accurately determined whether heavy fuel is used or light fuel is used early after the start of the engine. can do.
[0088]
(7) As engine operation control in accordance with the properties of the fuel used in the engine 1, the increase control (increase correction) corresponding to the increase value after the start of the fuel injection amount after the completion of the engine start corresponds to the volatility of the fuel. Implemented in a manner. That is, when heavy fuel with low volatility is used, the volatilization of the fuel injected into the combustion chamber 3 is less likely to proceed than when light fuel with high volatility is used. By adjusting the increase value after starting to a large value, the increase in the fuel injection amount is increased, and thus the engine operation is accurately stabilized after the start is completed. Further, since the determination of the volatility of the fuel can be completed at an early stage after the start of the engine, the amount of increase after the start corresponding to the volatility of the fuel in order to stabilize the engine operation after the completion of the start. The increase control of the fuel injection amount can be realized early after the start of the engine.
[0089]
(8) Further, as the engine operation control according to the property of the fuel used in the engine 1, the fuel injection timing control at the time of the stratified combustion operation after the start of the engine is also executed in a mode corresponding to the volatility of the fuel. The Rukoto. That is, when heavy fuel with low volatility is used, the fuel injection timing is controlled to be advanced compared to when light fuel with high volatility is used. At the time of stratified combustion operation, it is necessary to perform ignition in a state in which an air-fuel mixture containing combustible fuel (combustible air-fuel mixture) exists around the spark plug 5, and the timing at which such a state is reached is low in volatility. The slower the quality fuel. This is because the heavier the fuel, the longer it takes for the fuel injected into the combustion chamber 3 to volatilize, and the longer it takes for the amount of vaporized fuel around the spark plug 5 to reach an ignitable value. Therefore, the engine start is started by performing fuel injection timing control according to the volatility of the fuel, that is, the fuel injection timing when the heavy fuel is used is advanced than that when the light fuel is used. Good engine operation can be ensured during subsequent stratified combustion operation. In addition, fuel property determination according to fuel volatility can be completed at an early stage after the start of the engine start, so that the volatility of the fuel to ensure good engine operation in the stratified combustion operation after the start of the engine start. The control of the fuel injection timing according to the above can be realized early after the start of the engine.
[0090]
(9) In the in-cylinder injection type engine 1, particulates are likely to be generated in the exhaust after the start of the engine. Therefore, it becomes easy to determine the fuel property (volatility) based on the peak value Pmax of the particulate amount after starting the engine.
[0091]
(10) When starting the engine from a cold state, particulates are likely to be generated in the exhaust. Therefore, at the time of starting the engine from a cold state, it becomes easy to determine the fuel property (volatility) based on the peak value Pmax of the particulate amount after the start of the engine.
[0092]
[Third Embodiment]
Next, a third embodiment of the present invention will be described with reference to FIGS.
In this embodiment, the fuel property is determined according to the volatility of the fuel used in the engine 1 based on the time t until particulates are generated in the exhaust gas after the start of the engine.
[0093]
FIG. 11 is a time chart showing the transition of the particulate amount in the exhaust gas after the start of the engine 1 is started.
As shown in the figure, when fuel is injected and supplied into the combustion chamber 3 after the start of the engine 1, combustion is performed in a state where liquid fuel is present in the combustion chamber 3, and the amount of particulates in the exhaust gas Gradually increases to reach the peak value. When the vaporization of the liquid fuel is promoted by the heat during combustion and the liquid fuel in the combustion chamber 3 decreases, the amount of particulates in the exhaust gas gradually decreases from the peak value.
[0094]
As the fuel of the engine 1 is heavier and less volatile, the time at which particulates are generated in the exhaust after the start of the engine start is delayed. This is because the lower the volatility of the fuel, the more difficult the volatilization of the fuel injected and supplied into the combustion chamber 3 after the start of the engine starts. This is because it is difficult to rise, and the timing of particulate generation due to the combustion is delayed.
[0095]
In the present embodiment, the fuel property is determined according to the volatility by utilizing the characteristic that the time t from the start of the engine to the generation of particulates in the exhaust gas varies depending on the volatility of the fuel.
[0096]
That is, when the time t from when the engine starts to when particulates are generated in the exhaust (timing T3) is equal to or greater than the determination value d, the fuel used in the engine 1 is heavy and has low volatility. Judge that it is fuel. On the other hand, when the time t is less than the determination value d, it is determined that the fuel used in the engine 1 is a light fuel with high volatility.
[0097]
As described above, by determining the property (volatility) of the fuel used in the engine 1 based on the generation mode of the particulates generated in the exhaust gas at the start of the engine start, the volatility occurs early after the start of the engine. The fuel property can be determined according to the conditions.
[0098]
FIG. 12 is a flowchart showing a fuel property determination routine for determining the fuel property according to volatility as described above and setting the heavy flag F2 according to the determination result. This fuel property determination routine is executed through the electronic control unit 35 by, for example, a time interruption every predetermined time.
[0099]
In the fuel property determination routine, first, it is determined whether or not the engine 1 has started (S601). If the determination is affirmative, the determination value d for determining whether or not the fuel is heavy fuel with low volatility is calculated based on the coolant temperature (engine temperature) at the start of engine start and the like. (S602). The determination value d calculated in this way becomes smaller as the cooling water temperature is higher. This is because the higher the coolant temperature at the start of engine start, the easier the vaporization of the fuel proceeds when the fuel is injected and supplied into the combustion chamber 3 at the start of engine start. This is because the temperature in the chamber 3 is likely to rise, and the generation time of particulates in the exhaust becomes earlier.
[0100]
Thereafter, it is determined whether particulates are generated during exhaust (S603). When it is determined that particulates have occurred, it is determined whether or not time t from the start of engine start to particulate generation is equal to or greater than the determination value d (S604). If the determination is affirmative, it is determined that the fuel used in the engine 1 is a heavy fuel with low volatility, and the heavy flag F2 is set to “1 (heavy)” (S605).
[0101]
The heavy flag F2 is reset to “0 (low octane number)” every time the engine is stopped. Therefore, when the fuel used in the engine 1 is a light fuel with high volatility, the time t from the start of the engine to the generation of particulates is less than the determination value d, and the heavy flag F2 is set to “0 (light ) ”. In this way, the heavy flag F2 is set to “1 (heavy)” or “0 (light)” at an early stage after the start of the engine according to the volatility of the fuel used in the engine 1. Become.
[0102]
According to the embodiment described in detail above, the following effects can be obtained.
(11) The generation timing of particulates in the exhaust gas after the start of the engine is delayed as the fuel used in the engine 1 is heavy and has low volatility. Therefore, if the fuel used in the engine 1 is heavy, the time t from the start of the engine to the generation of particulates is equal to or greater than the determination value d. Therefore, based on whether or not the time t is equal to or greater than the determination value d, it is accurately determined whether heavy fuel is used or light fuel is used early after the start of the engine. be able to.
[0103]
(12) In the in-cylinder injection type engine 1, particulates are likely to be generated in the exhaust after the start of the engine. Accordingly, it becomes easy to determine the fuel property (volatility) based on the time t from the start of the engine to the generation of particulates.
[0104]
(13) When starting the engine from a cold state, particulates are likely to be generated in the exhaust. For this reason, when the engine is started from a cold state, it becomes easy to determine the fuel property (volatility) based on the time t from the start of the engine to the generation of particulates.
[0105]
In addition, each said embodiment can also be changed as follows, for example.
In each of the above embodiments, the fuel property may be determined only when the engine is started from a cold state. In this case, the determination values b, c, and d may be fixed values instead of variable values according to the cooling water temperature.
[0106]
-In the first embodiment, as the fuel property determination according to the octane number, the fuel is classified into two types, one having a high octane number and one having a low octane number. However, according to the octane number, three or more types are discriminated. May be.
[0107]
-In 2nd and 3rd embodiment, as fuel characteristic discrimination according to the volatility of fuel, it discriminate | determined into two types, a heavy thing with low volatility, and a light thing with high volatility. Depending on the level of volatility, three or more types may be discriminated.
[0108]
  Next, technical ideas other than the claims that can be grasped from the above embodiments will be described below together with the effects thereof.
  (1) Claims 1 to9The fuel property determination device for an internal combustion engine according to any one of the above, further comprising control means for executing engine operation control corresponding to the property of the fuel based on the property of the fuel determined by the determination means. A fuel property discrimination device for an internal combustion engine.
[0109]
When the internal combustion engine is started, the fuel supplied by injection exists in the combustion chamber in a liquid state, and combustion is performed in this state, thereby generating fine particles mainly composed of soot. Since the generation mode of such fine particles from the start of engine start varies depending on the fuel properties such as volatility and octane number, the fuel property can be determined based on the generation mode. Thus, by determining the fuel property using the fine particles generated at the time of starting the engine, the fuel property can be determined at an early stage after the start of the engine. As a result, good engine operation can be obtained by executing the engine operation control corresponding to the fuel properties at an early stage after starting the engine.
[0110]
(2) In the fuel property determination device for an internal combustion engine according to (1), the determination means determines the fuel property according to the octane number of the fuel, and the control means determines the determination An apparatus for determining a fuel property of an internal combustion engine, which performs ignition timing control corresponding to the property of the fuel.
[0111]
As for the ignition timing of the internal combustion engine, the higher the octane number of the fuel, the less likely knocking occurs during advance. For this reason, it is preferable to increase the engine output by controlling the ignition timing to the advance side as the octane number of the fuel increases. Therefore, by determining the fuel properties according to the octane number as described above and performing the ignition timing control corresponding to the determined octane number of the fuel, the output performance of the internal combustion engine can be maximized while suppressing knocking. Can do. In addition, since the determination of the fuel property according to the octane number can be completed at an early stage, the ignition timing control according to the octane number of the fuel is performed in order to maximize the output performance of the internal combustion engine while suppressing knocking. This can be realized early after starting.
[0112]
(3) In the fuel property determination device for an internal combustion engine according to (1), the determination means determines the fuel property according to the volatility of the fuel, and the control means determines the determination. A fuel property determination device for an internal combustion engine, which performs fuel injection amount control corresponding to the property of the fuel.
[0113]
In the internal combustion engine, the fuel injection amount is increased after the start for the purpose of stabilizing the engine operation. As for the increase in the fuel injection amount, it is preferable to increase the fuel injection amount so as to be a heavy fuel having low volatility in order to ensure stable engine operation after the engine is started. Therefore, by determining the fuel according to the volatility as described above, and controlling the increase in the fuel injection amount after the engine start as the fuel injection amount control corresponding to the determined volatility of the fuel, Can be appropriate for ensuring stable engine operation after the engine is started. Further, since the determination of the fuel property according to the volatility can be completed at an early stage, the fuel injection amount according to the volatility of the fuel for controlling the increase in the fuel injection amount after the engine start to an appropriate value Control can be realized early after the start of the engine.
[0114]
(4) In the fuel property determination device for an internal combustion engine described in (1) above, the internal combustion engine performs stratified combustion, and the determination means determines the fuel property according to the volatility of the fuel. A fuel property determination device for an internal combustion engine, wherein the control means executes fuel injection timing control corresponding to the determined fuel property.
[0115]
At the time of stratified combustion of an internal combustion engine, it is necessary to perform ignition in a state in which an air-fuel mixture containing combustible fuel (combustible air-fuel mixture) exists around the ignition plug. The timing at which an air-fuel mixture including vaporized fuel that can be ignited around the spark plug becomes slower as the fuel is a heavier fuel with lower volatility. This is because the heavier fuel, the longer it takes for the injected fuel to volatilize, and the longer it takes for the amount of vaporized fuel around the spark plug to reach a value that can be ignited. For this reason, the fuel injection timing during the stratified combustion operation is delayed as the fuel is a heavy fuel with low volatility, and the longer the time from fuel injection to ignition, the better the engine operation in the stratified combustion operation. It is preferable in obtaining. Therefore, the fuel is determined according to the volatility as described above, and as the fuel injection timing control corresponding to the determined volatility of the fuel, the fuel injection timing control that delays the fuel injection timing as the fuel is heavy is performed. Thus, it is possible to perform a good engine operation during the stratified combustion operation. In addition, since the determination of the fuel property according to the volatility can be completed at an early stage, the fuel injection timing control according to the volatility of the fuel for performing good engine operation at the time of stratified combustion is performed after the engine is started. It can be realized early.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing an entire engine to which a fuel property determination apparatus according to a first embodiment is applied.
FIG. 2 is a flowchart showing a procedure for calculating an ignition timing command value.
FIG. 3 is a time chart showing the transition of the amount of particulates contained in the exhaust after starting the engine.
FIG. 4 is a flowchart showing a fuel property determination procedure according to the first embodiment.
FIG. 5 is a flowchart showing a procedure for calculating a fuel injection amount command value.
FIG. 6 is a graph showing how an optimal increase value after start changes according to a change in fuel volatility.
FIG. 7 is a flowchart showing a procedure for calculating a fuel injection timing command value.
FIG. 8 is a graph showing how an optimum fuel injection timing command value during stratified combustion operation changes according to a change in fuel volatility.
FIG. 9 is a flowchart showing a fuel property determination procedure according to the second embodiment.
FIG. 10 is a time chart showing the transition of the amount of particulates contained in the exhaust after starting the engine.
FIG. 11 is a time chart showing the transition of the amount of particulates contained in the exhaust after starting the engine.
FIG. 12 is a flowchart showing a fuel property determination procedure according to the third embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Engine, 2 ... Intake passage, 3 ... Combustion chamber, 4 ... Fuel injection valve, 5 ... Spark plug, 6 ... Piston, 7 ... Exhaust passage, 8 ... Connecting rod, 9 ... Crankshaft, 10 ... Crank position sensor, DESCRIPTION OF SYMBOLS 11 ... Throttle valve, 12 ... Vacuum sensor, 13 ... Accelerator pedal, 14 ... Accelerator position sensor, 15 ... Throttle position sensor, 34 ... Particulate detection sensor (detection means), 35 ... Electronic control device (discrimination means), 36 ... Water temperature sensor.

Claims (9)

Based on the amount of fine particles mainly composed of soot in the exhaust when a predetermined time has elapsed since the start of the engine, the determination means for determining the properties of the fuel used in the internal combustion engine ,
The fuel property determination apparatus for an internal combustion engine, wherein the predetermined time is longer than a time required for the amount of the fine particles to reach a peak value . Based on the amount of fine particles mainly containing soot in the exhaust at the time of the institutional beginning of startup predetermined time has elapsed, comprises determination means for determining fuel nature in accordance with the octane number of the fuel used in the internal combustion engine
A fuel property determination apparatus for an internal combustion engine. Provided with discriminating means for discriminating the properties of the fuel used in the internal combustion engine based on the peak value of the amount of fine particles mainly composed of soot in the exhaust gas after starting the engine
A fuel property determination apparatus for an internal combustion engine. 4. The fuel property determination device for an internal combustion engine according to claim 3 , wherein the determination means determines the fuel property according to the volatility of the fuel based on the peak value . Provided with discriminating means for discriminating the properties of the fuel used in the internal combustion engine based on the time from the start of the engine until the generation of fine particles mainly composed of soot in the exhaust gas
A fuel property determination apparatus for an internal combustion engine. 6. The fuel property discrimination device for an internal combustion engine according to claim 5 , wherein the discrimination means discriminates the fuel property according to the volatility of the fuel based on the time . The fuel property determination device for an internal combustion engine according to any one of claims 1 to 6 , wherein the determination unit determines a fuel property based on a detection signal from a detection unit that detects the amount of the particulates in the exhaust gas . 8. The fuel property determination apparatus for an internal combustion engine according to claim 1 , wherein the internal combustion engine is a direct injection internal combustion engine that directly injects fuel into a combustion chamber . The fuel property determination device for an internal combustion engine according to any one of claims 1 to 8, wherein the determination means determines the fuel property at least when the engine is started from a cold state .

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