JP3211573B2 - Engine ignition timing control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ignition timing control device for an engine.

[0002]

2. Description of the Related Art In general, there is known a control for measuring a rotational fluctuation rate of an engine and, when the fluctuation rate is less than an allowable value, retarding an ignition timing to a stability limit in order to reduce HC emission (JP-A-Hei. 4-66750).

[0003] Explaining this, the reason why the HC emission is reduced by retarding the ignition timing is that the main combustion end timing is delayed by the retardation of the ignition timing and the exhaust gas temperature rises. This is because unburned gas (HC) accumulated in the gap between the piston and the cylinder is discharged in the later stage of combustion, but this HC is burned.) In addition, since the ignition timing retards the temperature in the cylinder (combustion gas temperature) and suppresses the generation of NOx,
NOx emissions will also be reduced.

On the other hand, as shown in FIG. 42, the more the ignition timing is retarded, the greater the surge torque becomes (the engine rotation becomes unstable). Therefore, the ignition timing is retarded to the stability limit. In the drawing, MBT is the minimum advance value at which the maximum torque is obtained.

[0005]

By changing the temperature conditions and the fuel properties (specifically, the volatility), the effect of the retardation of the ignition timing on the HC emission was examined.
The results as shown in FIGS. 43 and 44 were obtained. FIG. 43 shows the characteristics when the cooling water temperature is low, and FIG. 44 shows the characteristics when the cooling water temperature is high. From the figure, it can be seen that at low temperatures when heavy gasoline is used, the amount of HC emission increases, contrary to what was conventionally thought (see the thick solid line in FIG. 43).

However, in the above device, the ignition timing is retarded to the stability limit irrespective of the fuel properties and temperature conditions. Therefore, when heavy gasoline is used, the HC emission is increased at low temperatures. It will be lost.

Accordingly, an object of the present invention is to reduce the amount of HC emission even at a low temperature using heavy gasoline by advancing the ignition timing from a stability limit at a low temperature using heavy gasoline. And

[0008]

According to a first aspect of the present invention, as shown in FIG. 45, a means 41 for searching a stability limit by retarding an ignition timing and detecting a fuel property of a fuel used at the time of starting. Means 42 and a limit engine temperature at which a limit engine temperature at which HC emission decreases due to retardation of ignition timing is defined as a limit temperature LTW.
A means 43 for calculating in accordance with the detected value of the fuel property Te,
A means 44 for detecting an engine temperature (for example, a cooling water temperature Tw), a means 45 for determining whether the engine temperature is lower than the limit temperature LTW or higher than the limit temperature LTW, and a determination result indicating that the engine temperature is lower than the limit temperature LTW. A means 46 for advancing the ignition timing from the stability limit searched by the stability limit search means 41 in the temperature range of the above; and a search by the stability limit search means 41 when the temperature range becomes equal to or higher than the limit temperature LTW based on the determination result. Means 47 for retarding the ignition timing until the stability limit is reached.

The second invention is, as shown in FIG. 46, a means 41 for searching for a stability limit by delaying the ignition timing, and a catalyst temperature of a catalyst interposed near an engine out (for example, an exhaust manifold). Means 5 for detecting CAT
1; a first temperature range determining means 52 for determining whether the catalyst temperature CAT is lower than or equal to an activation temperature T50 of the catalyst or higher than the activation temperature T50;
The means 53 for delaying the ignition timing from immediately after the start to the stability limit searched by the stability limit search means 41 in the temperature range of the activation temperature T50 or less from the determination result of 2, and detecting the fuel property of the fuel used at the time of the start. Means 42 for limiting the engine temperature at which the HC emission is reduced due to the retardation of the ignition timing.
Means 43 for calculating the boundary temperature LTW according to the detected value of the fuel property; and an engine temperature (for example, a cooling water temperature T).
w), a second temperature range determining unit 54 for determining whether the engine temperature is lower than the limit temperature LTW or higher than the limit temperature LTW, and a second temperature range determining unit 54. From the stability limit searched by the stability limit search means 41 in the temperature range exceeding the activation temperature T50 and the temperature range below the limit temperature LTW from the determination result of the first temperature range determination means 52 and the determination result of the first temperature range determination means 52. When the temperature range is equal to or higher than the limit temperature LTW based on the determination result of the second temperature range determination unit 54, the ignition timing is retarded again to the stability limit searched by the stability limit search unit 41. Means 47 are provided.

The third invention comprises a means 41 for searching for a stability limit by retarding the ignition timing, a means 44 for detecting an engine temperature (for example, a cooling water temperature Tw), as shown in FIG. Third temperature range determining means 61 for determining whether the engine temperature is less than a predetermined value HCTW or not less than a predetermined value HCTW; and a temperature range less than a predetermined value HCTW based on the determination result of the third temperature range determining means 61. Means 62 for advancing the ignition timing from the stability limit searched by the stability limit search means 41, and the catalyst temperature CAT of the catalyst interposed at a position far away from the engine out (for example, behind the front tube of the exhaust pipe). Means 6 for detecting
3, a first temperature range determining means 52 for determining whether the catalyst temperature CAT is equal to or lower than the activation temperature T50 of the catalyst or has exceeded the activation temperature T50;
2 and the determination result of the third temperature range determination means 61, a temperature range equal to or higher than the predetermined value HCTW and the activation temperature T50.
The stability limit search means 41 determines the ignition timing in the following temperature range.
And means 53 for retarded to the searched stability limit, and means 42 for detecting a fuel property of fuel used during startup, the engine temperature <br/> of the limit HC emissions reduced by retarding the ignition timing a means 43 for calculating in accordance with the detected value of the fuel property as a temperature limit LTW, the engine temperature detecting means 44
A second temperature range determining means 54 for determining whether the detected engine temperature is lower than the limit temperature LTW or higher than the limit temperature LTW;
4 and the determination result of the first temperature range determination means 52, the temperature range exceeding the activation temperature T50 and the limit temperature LT.
A means 46 for advancing the ignition timing from the stability limit searched by the stability limit search means 41 in a temperature range lower than W, and a limit temperature LT based on the determination result of the second temperature range determination means 54.
Means 47 is provided for delaying the ignition timing again to the stability limit searched by the stability limit search means 41 when the temperature range becomes equal to or higher than W.

A fourth invention is the second invention or the third invention, wherein the activation temperature T as shown in FIG.
The means 71 for setting 50 is a means 72 for calculating the operation history of the catalyst since it was new, and the means for correcting the activation temperature T50f of the catalyst when it is new as the operation history becomes longer as the operation history becomes longer. Means 73 for calculating the temperature T50.

In a fifth aspect based on any one of the first to fourth aspects, the advance amount SADV is a value that increases as the detected value of the fuel property increases.

In a sixth aspect based on any one of the first to fourth aspects, the advance amount SADV is a value that increases as the engine temperature decreases.

According to a seventh aspect of the present invention, in any one of the first to sixth aspects of the present invention, only when there is a rapid rise in engine temperature during the advance from the stability limit, the stability is reduced. Is stopped and the stability limit is searched.

According to an eighth aspect of the present invention, in any one of the first to seventh aspects, as shown in FIG. 49, the fuel property detecting means 42 detects the basic advance value BADV by using a heavy gasoline ( When the target is heavy gasoline having various degrees of heaviness, the heaviest one is selected from among them) means 81 for setting at the stability limit, and the retard amount FADV of a gradually increasing value 82, a means 83 for calculating the engine rotation fluctuation rate σn,
means 84 for determining whether n is equal to or less than a predetermined value β or exceeding a predetermined value β;
Is equal to or less than a predetermined value β, the basic advance value BADV is corrected by the retard amount FADV to calculate the ignition advance value ADV, and the means 86 for performing ignition with the ignition advance value ADV 86
Means 87 for calculating a fuel property index Fuel based on the retardation amount FADV when the rotation fluctuation rate σn exceeds a predetermined value β based on the determination result.

According to a ninth aspect of the present invention, in the eighth aspect of the present invention, FIG.
As shown in FIG. 0, the fuel property index calculating means 87 calculates a basic fuel having a value that increases as the retard amount FADV increases based on the retard amount FADV when the rotational fluctuation rate σn exceeds a predetermined value β. It comprises means 91 for calculating the property index Fuel0 and means 92 for calculating the fuel property index Fuel by correcting the basic fuel property index Fuel0 to a value that increases as the engine temperature decreases.

In a tenth aspect based on any one of the first to seventh aspects, the fuel property detecting means 42 is provided.
Is a sensor that directly detects fuel properties.

[0018]

According to the first aspect of the present invention, during low temperature starting using heavy gasoline, the ignition timing is advanced from the stability limit until the engine temperature reaches the limit temperature LTW from the detection timing of the fuel property, and the engine temperature is increased. When the temperature exceeds the limit temperature LTW, the ignition timing is retarded to the stability limit. Therefore, during the period from the fuel property detection timing to the time when the engine temperature reaches the limit temperature LTW, H during the engine-out is reduced.
C emissions decrease.

In the second aspect of the present invention, when a catalyst is interposed near the engine out, when starting the engine at low temperature using heavy gasoline, the catalyst temperature CAT is changed from the fuel property detection timing to the catalyst activation temperature T50. Until the catalyst temperature CAT exceeds the activation temperature T50 until the engine temperature reaches the limit temperature LTW until the engine temperature reaches the limit temperature LTW. When the engine temperature becomes higher than the limit temperature LTW, the ignition timing is retarded to the stability limit. Therefore, the engine is stopped even after the catalyst temperature CAT exceeds the activation temperature T50 until the engine temperature reaches the limit temperature LTW. In addition to the decrease in the amount of HC emitted by the catalyst, the catalyst temperature CAT becomes the activation temperature T of the catalyst from the detection timing of the fuel property.
Until 50, HC emission at the catalyst outlet is reduced.

In the third aspect of the present invention, when a catalyst is interposed at a position far from the engine out, at the time of low temperature starting using heavy gasoline, the engine temperature is set to a predetermined value HCTW based on the fuel property detection timing. The ignition timing is advanced from the stability limit until the catalyst temperature reaches the predetermined value HCTW, and the ignition timing is delayed to the stability limit until the catalyst temperature CAT exceeds the catalyst activation temperature T50. The ignition timing is advanced from the stability limit until the engine temperature reaches the limit temperature LTW from the time when the catalyst temperature CAT exceeds the activation temperature T50 until the engine temperature reaches the limit temperature LTW. The ignition timing is retarded until the engine is out at the time of low temperature using heavy gasoline. Activation because the catalyst even when not so fast, HC emission amount at the catalyst exit is reduced.

In the fourth invention, according to the deterioration of the catalyst,
Since the activation temperature of the catalyst becomes higher as the operation history becomes longer, even when the catalyst is deteriorated at the time of the cold start using heavy gasoline, the early activation of the deteriorated catalyst is performed without excess or shortage.

In the fifth aspect, the advance amount SADV is a value that increases as the detected value of the fuel property becomes heavier.
As long as the engine temperature at the time of matching the advance correction amount SADV is the same, the advance correction amount SADV is given without excess or deficiency even if the fuel properties are different.

In the sixth aspect, the advance amount SADV is a value that increases as the engine temperature decreases. Therefore, if the fuel property is the same as the fuel property when matching the advance angle correction amount SADV, even if the engine temperature is different, , The advance correction amount SADV is given without excess or deficiency.

According to the seventh aspect, the advance from the stability limit is stopped and the stability limit is searched only when there is a rapid rise in the engine temperature during the advance from the stability limit. At a low temperature using gasoline, the time during which the ignition timing is advanced from the stability limit becomes longer, and accordingly, the amount of HC emission at the time of engine out decreases.

According to the eighth aspect of the present invention, there is no need to provide a sensor for directly detecting the fuel property, so that the cost does not increase.

According to the ninth aspect, even when the engine temperature is different, the fuel property index Fuel can be given without excess or deficiency.

In the tenth aspect, at the time of low-temperature starting using heavy gasoline, the timing of starting the advance from the stability limit is earlier than when estimating the fuel property from the engine rotation fluctuation rate. HC emission will be reduced.

[0028]

In FIG. 1, air is sucked into an engine from an air cleaner 2 through an intake pipe comprising an intake duct 3, a throttle chamber 4 and an intake manifold 5.

Each branch of the intake manifold is provided with a fuel injector 6 comprising an electromagnetic open / close valve that opens when energized to a solenoid coil and closes when energization is stopped. While the pressure is at the high level, the fuel adjusted by the pressure regulator 7 so that the pressure difference with the intake pipe becomes constant is intermittently injected and supplied in synchronization with the rotation of the engine.

This injected fuel forms an air-fuel mixture with air and is ignited and burned by spark ignition in a cylinder.
The exhaust gas is discharged from the exhaust manifold 8 via the three-way catalyst 9.

Reference numeral 12 denotes a hot-wire type air flow meter provided immediately downstream of the air cleaner, and outputs a signal corresponding to the intake air flow rate Q. Reference numeral 13 denotes a crank angle sensor, which is a Ref signal (in the case of a four-cylinder engine, a signal at every 180 ° crank angle) and a Pos signal (1 ° crank angle).
Unit signal). A water temperature sensor 14 detects a cooling water temperature Tw of a water jacket of the engine.

The signals from these sensors, together with the signal from the O ₂ sensor 15 which outputs a signal corresponding to the oxygen concentration in the exhaust gas, are mainly composed of a microcomputer.
The ECU 11 controls the fuel supply to the engine while executing feedback control of the air-fuel ratio and learning control of the air-fuel ratio.

The air-fuel ratio control in the ECU 11 is as follows.

The fuel injector 6 is driven in synchronization with the Ref signal. For example, in the sequential injection method, once every two revolutions of the engine, and for each cylinder, Ti = 2 × Te + Ts (1) where Te: effective pulse width Ts: injection pulse given by the formula of invalid pulse width according to battery voltage Injector 6 with width Ti
Operate. Ts is a correction value for compensating for an error with the actual injection amount due to the operation of the injector. In addition,
In the case of the simultaneous injection system, the injector 6 has an injection pulse width Ti given by the following equation: Ti = Te + Ts once for every rotation of the engine and simultaneously for all cylinders.
Operate.

FIG. 2 is a flow chart for calculating the effective pulse width Te of the above equation (1).
Execute in ec).

In step 1, the basic pulse width Tp is calculated from the air flow rate Q detected by the air flow meter 12 and the engine speed N detected by the crank angle sensor 13, as follows: Tp = (Q / N) × K (3) : Calculated by the formula of constant. The air-fuel ratio determined by this Tp is called the base air-fuel ratio.

In step 2, the effective pulse width Te is calculated by using the basic pulse width Tp, and Te = Tp × Co × {(α + αm-100) / 100} (4) where Co: various correction coefficients α: air-fuel ratio feedback Correction coefficient [%] αm: Air-fuel ratio learning value [%]

The various correction coefficients Co in the equation (4) are values for ensuring smooth operation under various conditions. For example, at start-up, warm-up, and high load, the basic pulse width T is determined based on signals from the water temperature sensor 15 and other sensors.
Correct p. At this time, the value of the air-fuel ratio feedback correction coefficient α is clamped at 100%.

FIG. 3 is a flowchart for calculating the fuel injection pulse width Ti and executing the injection, which is executed in synchronization with the Ref signal.

Step 11 for sequential injection
Then, the fuel injection pulse width Ti of the above equation (1) is calculated, and this is transferred to the output register of the CPU (one of the components of the microcomputer) in step 12. Assuming that the ignition order in the four-cylinder engine is # 1- # 3- # 4- # 2, the input of the Ref signal this time causes the T
If the fuel corresponding to i is supplied, the next (that is, one time later) input of the Ref signal causes the third cylinder to receive the R signal two times later.
The fuel of Ti is supplied to the fourth cylinder by the input of the ef signal and to the second cylinder by the input of the Ref signal three times later.

The air-fuel ratio feedback correction coefficient α in the equation (4) is a value obtained in synchronization with the Ref signal by proportional integral control (a type of feedback control) based on the output of the O ₂ sensor 15, and the value of α is 100% Is exceeded, from equation (4), the air-fuel ratio is returned to the rich side, and if it is less than 100%, the air-fuel ratio is returned to the lean side. Due to this α, the actual air-fuel ratio changes at a cycle of approximately 1-2 Hz,
That is, the average air-fuel ratio is maintained within the window (a predetermined air-fuel ratio range around the stoichiometric air-fuel ratio).

On the other hand, it is generally known to control the engine rotation fluctuation rate, and when the fluctuation rate is less than the allowable value, retard the ignition timing to the stability limit in order to reduce the amount of HC emission when the engine is out. However, experiments have shown that when the ignition timing is retarded to a low temperature when heavy gasoline is used, the amount of HC emission at the engine out increases rather.

When the combustion analysis is performed to find out the cause, the relationship between the main combustion period θ _10-90 and the ignition timing and the relationship between the main combustion end timing θ ₉₀ and the ignition timing are as shown in FIG. 4 and FIG. 6 and 7 show the relationship between the combustion parameters θ _10-90 and θ ₉₀ and the amount of HC emission. As the ignition timing is retarded, the main combustion period θ _10-90 is longer (see FIG. 4), the main combustion end timing θ ₉₀ is later (see FIG. 5), and when θ _{90 is} constant, θ _10-90 is longer. The HC discharge amount increases (see FIG. 6), and when θ _10-90 is constant, the HC discharge amount decreases as θ ₉₀ comes to the retard side (see FIG. 7). That is, if the ignition timing is retarded, θ _10-90 becomes longer, so that H
While C emissions increases, theta ₉₀ exhaust temperature rises because coming retarded, HC emission amount decreases. There are two contradictory factors to HC emissions. Note that θ
_10-90 is 9% starting from 10% fuel burning
The period until 0% burns, and θ ₉₀ is the time when the fuel burns to 90%.

FIGS. 8 and 9 summarize the above results separately for a case where the cooling water temperature is high and a case where the temperature is low when heavy gasoline is used. When the coolant temperature is high, more of the effects of HC reduction by retarding theta ₉₀ is, theta _10-90 for over tendency of HC emission amount increases by the longer, the HC emission amount in retardation of the ignition timing On the other hand, when heavy gasoline was used and the temperature was low, θ
The tendency of the increase in HC emission due to the increase of _10-90 became relatively large, and the HC emission was supposed to increase (see FIG. 9).

This phenomenon can be explained by considering the following.

FIG. 10 schematically shows the respective HC emissions at the end of the main combustion and at the engine out. HC emissions at the end the main combustion in the figure becomes the unburned HC is dominant after the main combustion, combustion this unburned HC is has a correlation with the theta _10-90 after the main combustion (theta _10-90 becomes long HC emission increases due to deterioration), and the HC emission of the engine out is reduced by a certain ratio due to afterburning of HC at the end of main combustion. Therefore, the reduction ratio of HC emission due to afterburning ( corresponds to the slope of the illustrated linear) has a correlation with θ ₉₀ (θ ₉₀
Is retarded, afterburning is promoted, and the amount of HC emission decreases).

Using this figure, when the cooling water temperature is high, as shown in FIG. 11, the retardation of θ ₉₀ is larger than the increase of unburned HC after the main combustion due to the increase of θ _10-90. It is considered that the effect of afterburning due to the above becomes relatively large, and the HC emission as a whole is reduced. On the other hand, at a low temperature when heavy gasoline is used, as shown in FIG. 12, the influence of the unburned HC increase after the main combustion due to θ _10-90 being longer than the afterburning effect is shown. It is considered that the total amount of HC emissions increased because the value was relatively large. Therefore, the characteristics at the time of low temperature when heavy gasoline is used, as shown in FIG. 13, are that the amount of HC emission rather increases due to the retardation of the ignition timing.

In order to deal with this, the control unit 11, as shown in FIG. 14, sets a boundary (boundary temperature) at a boundary (boundary temperature) at which the amount of HC emission at the engine out decreases due to the retardation of the ignition timing. In the region above the line (hatched region), the ignition timing is retarded to the stability limit, and in the region below the boundary line, the ignition timing is advanced from the stability limit by an optimal amount determined by the fuel property.

In FIG. 14, since the boundary temperature LTW is determined according to the fuel properties and becomes higher as the fuel becomes heavier, the cooling water temperature Tw is compared with the boundary temperature LTW, so that the area above the boundary line can be determined. It is determined whether or not it is in the lower area. For example, in the case of a cold start using heavy gasoline, the ignition timing is advanced from the stability limit in a water temperature range below the boundary temperature LTW, and thereafter, after the cooling water temperature Tw reaches the boundary temperature LTW, That is, the ignition timing is retarded to the stability limit. On the other hand, when the lightest gasoline is used, the cooling water temperature Tw is always equal to or higher than the boundary temperature LTW, so that the ignition timing is retarded to the stability limit over the entire cooling water temperature.

Although the NOx emission increases with the advance of the ignition timing, the most concern in the exhaust performance at low temperatures is the HC emission. Therefore, in the present invention, the ignition timing is advanced. No consideration is given to an increase in NOx when this is done.

FIG. 15 is a flow chart for calculating the fuel property index Fuel, which is executed in synchronization with the Ref signal at the time of startup (ends at the time when Fuel is calculated).

First, at step 21, the cooling water temperature Tw [° C.]
And the engine speed N [rpm] are read.

In step 22, the basic advance value BADV [°] is calculated from the rotation speed N and the basic pulse width (engine load equivalent amount) Tp [ms] with reference to the map shown in FIG.
In step 23, the coolant temperature correction amount CADV of the ignition timing is referred from the cooling water temperature Tw with reference to the table containing the contents of FIG.
[°] is determined. Since the basic pulse width Tp is obtained by calculating the fuel injection pulse width Ti, the basic pulse width Tp is read from the memory containing the value of Tp.

In step 24, it is checked whether or not the rotation fluctuation rate σn has been obtained. Since the rotational fluctuation rate σn cannot be determined until after the engine rotational speed N has been sampled by a predetermined number, as will be described later, if the rotational fluctuation rate σn is not determined, the ignition advance value ADV [°] is determined in step 25. ADV ← BADV + CADV (5) The calculated value is transferred to the output register in step 26.

The value of the ignition advance value ADV in the equation (5) is expressed by Re
It is a value measured in a direction in which the crank angle decreases from the f signal (rising at a predetermined crank angle position before the compression top dead center of each cylinder). That is, the ignition timing is advanced as the value of ADV increases. For example, the rise of the Ref signal is 70 ° before the compression top dead center,
Assuming that ADV is 40 °, the output register cuts off the primary current of the ignition coil (ignition execution) at the timing of counting (70-40) unit crank angles from the input of the Ref signal.

As shown in FIG. 16, the basic advance value BADV on the right side of the equation (5) is a value on the retard side (for example, 10 ° BTDC) as the rotational speed and load become lower. This is to avoid knocking at a low rotation speed and a high load, even if the supplied fuel amount is the same. The actual data of the basic advance value BADV is matched with the water temperature correction amount CADV described below so as to reach the stability limit when using heavy gasoline.

The water temperature correction amount CADV in the equation (5) is calculated as shown in FIG.
As shown in (2), the value increases as the cooling water temperature Tw decreases (the advance correction amount ADV increases). Even if the supplied fuel amount and the basic advance value BADV are the same, since the engine rotation becomes unstable and a surge is likely to occur as the temperature decreases, the CADV value should be increased as the temperature decreases (advance the ignition timing). This stabilizes the engine rotation in the low temperature range.

If the rotational fluctuation rate .sigma.n has been determined, the routine proceeds from step 24 to step 27, where the rotational fluctuation rate .sigma.n
[%] And a predetermined value (for example, 8%) β, and σn ≦ β
If so, it is determined that the ignition timing is more advanced than the stability limit, and in order to retard the ignition timing to the stability limit, the ignition advance value ADV [°] is set to ADV ← BADV + CADV-FADV in step 28 (6). However, FADV is calculated by the equation of retard variable [°], and this is transferred to the output register in step 26.

The value of the retard variable FADV in the equation (6) is a value that gradually increases from 0 (initial value) as long as the determination in step 27 is σn ≦ β (described later). If the rotation speed N and the basic pulse width Tp are almost the same, the ignition timing is gradually retarded (the engine rotation becomes unstable) by repeating steps 27, 28 and 26, and eventually. In step 27, σ
If n> β, it can be determined that the stability limit has been reached.

When the stability limit is reached, step 29
Advances the ignition advance value ADV by 1 °, and transfers this to the output register in step 30. The reason why the angle is advanced by 1 ° is that the engine rotation is unstable if σn> β.

At step 31, the retard variable FA at that time is
The fuel property index Fuel [absolute number] is obtained from the DV value and the cooling water temperature Tw with reference to a map having the contents shown in FIG.

The larger the value of the fuel property index Fuel, the lighter the fuel property index. As shown in FIG. 18, when the cooling water temperature Tw is constant, the larger the value of the retard variable FADV, the larger the fuel property index Fuel. ), And the retard variable FADV
When the cooling water temperature Tw is lower, the temperature becomes larger. This is because, given that the basic advance value BADV and the value of the coolant temperature correction amount CADV are the same, if the coolant temperature Tw is constant,
The lighter the engine, the more stable the engine rotation and the retard variable FAD
Since V increases, as the value of FADV increases, F
This is because the value of uel must be increased (that is, lightened). Further, when the value of FADV is constant, the engine rotation becomes more stable as the cooling water temperature Tw becomes higher.
Even if the value of FADV is the same, the lower the cooling water temperature Tw, the higher the F
The value of uel must be increased.

In step 32, the value of the flag F (initial value is "0") is set to "1", and in step 33, the cooling water temperature Tw is inserted into a variable Tw1 [° C.] representing the previous cooling water temperature, and FIG. End the routine. F = 1 is the fuel property index F
This means that the calculation of uel has been completed.

FIG. 19 is a flowchart for controlling the ignition timing in a normal state, and is executed in synchronization with the Ref signal. The reason for synchronizing with the Ref signal is that there is no interrupt processing in the ignition timing control unlike the fuel injection control.

At step 41, the value of the flag F is checked and F =
If it is 0, it is determined that the fuel property index Fuel has not been calculated yet, and the routine in FIG. 19 ends.

After F = 1, the routine proceeds to step 42 and on, where normal ignition timing control is performed. While F = 0, the ignition timing control is performed in FIG.
It is normal time after that.

In step 42, the cooling water temperature Tw is read, and the boundary temperature LTW is obtained from the fuel property index Fuel obtained in FIG. 15 by referring to the table in FIG. 20 in step 43.

The boundary temperature LTW is the cooling water temperature at the boundary where HC emission decreases due to the retardation of the ignition timing as shown in FIG. 14, and the fuel property index Fuel is large as shown in FIG. (Ie, lighter) the lower the temperature.

This boundary temperature LTW is compared with the cooling water temperature Tw in step 44, and if Tw <LTW, step 4
At 5, control is performed to advance from the stability limit, and Tw ≧ LT
When it becomes W, control is performed in step 46 to retard the ignition timing to the stability limit.

FIG. 21 is a flowchart of the advance angle control from the stability limit (that is, the details of step 45 in FIG. 19), which is executed in synchronization with the Ref signal.

At step 51, the rotational speed N is read, and at step 52, the value of the flag F2 is checked. In the first time, since F2 = 0, the process proceeds to step 53, and the difference between the value entered in the variable Tw1 [° C.] representing the previous cooling water temperature and the current water temperature Tw [° C.] is entered in the variable ΔTw, and this variable ΔTw [ .Degree. C.] and a predetermined value (for example, 3.degree. C.). Gamma.

Since the value of ΔTw represents an increase in water temperature from the previous time, if ΔTw <γ, it is determined that there is no rapid temperature increase, and in step 55, the cooling water temperature Tw and the fuel property index Fue are determined.
1 to determine a spark advance correction amount SADV [°] with reference to FIG.
V is updated by the formula of ADV ← ADV + SADV (7), and this is transferred to the output register in step 57.

ADV on the right side of the equation (7) is the ignition advance value at the stability limit, and the advance is corrected from this value by the value of SADV.

As shown in FIG. 22, the advance correction amount SADV
Is a value that increases as the value of Fuel decreases (as the fuel becomes heavier) and as the cooling water temperature Tw decreases.

In step 58, the cooling water temperature Tw is moved to the variable Tw1 representing the previous cooling water temperature, and the routine of FIG. 21 is terminated.

On the other hand, if it is determined in step 54 that there is a sharp rise in temperature due to ΔTW ≧ γ, step 59
To set the flag F2 to "1", and then to steps 60, 61, 62, 63 and 64 to search for the stability limit. The search for the stability limit is performed only when there is a sharp temperature rise for the following reason. T
The ignition timing will be advanced based on the stability limit in the temperature range of w <LTW. However, it takes time to search for the stability limit (during which time, the advance cannot be made). If you are looking for the stability limit every time, the time that the ignition timing is advanced from the stability limit becomes shorter,
The effect of this control may be reduced. Therefore, the stability limit is searched only when the stability limit itself is deviated due to a rapid rise in cooling water temperature, so that the ignition timing is advanced from the stability limit as long as possible.

At the next control, since F2 = 1, the process proceeds from step 52 to step 60, and the stability limit is continuously searched. When the stability limit is reached, the process proceeds from step 62 to step 65 and thereafter, and in step 67, the flag F2 is reset to “0”. When the next control is performed by resetting the flag F2, the flow proceeds from step 52 to step 53. If ΔTw <γ, the advance control from the stability limit is continued again (steps 54 to 5).
8).

Steps 65, 66, 69 not described
Are the same as steps 29, 30, and 33 in FIG. In step 68, the initial value 0 is set in the retard variable FADV in preparation for the next search for the stability limit.

FIG. 23 (details of step 46 in FIG. 19) is a control for retarding to the stability limit, which is the same as the conventional control.

FIG. 24 is a flowchart for calculating the engine rotation fluctuation rate σn, which is executed continuously by a background job (for example, at a period of 10 msec).

In step 81, it is determined whether or not the engine rotation has been stabilized after the engine is started.
Sample the engine speed N.

In step 83, it is determined whether or not the number of samples of the rotation speed N has reached a predetermined value (for example, 20 times).
If the engine speed N is equal to or more than the predetermined value, the process proceeds to step 84, and the maximum value Nmax [rpm] and the minimum value Nmin [rp] are selected from the past predetermined number (20 times) of the sampled engine speed N.
m]. In step 85, the average value Nave [rpm] of a predetermined number of sample data in the past is calculated.

In step 86, the rotational fluctuation rate σn [%] is calculated by the following equation: σn = {(Nmax−Nmin) / Nave} × 100 (8)

FIG. 25 is a flowchart for gradually increasing the retard variable FADV, which is executed at a constant period (for example, 1 sec). The reason why the increase cycle of FADV is set relatively long at 1 sec is to take into account the time required for the rotation fluctuation to settle at the 1 ° ignition timing delay accompanying the search for the stability limit.

In step 91, the rotational fluctuation rate σn is compared with a predetermined value β, and if σn ≦ β, in order to find a stability limit, in step 92, the retard variable FADV is increased by 1 °.

Here, the operation of this example will be described with reference to FIG. 26. FIG. 26 is a characteristic diagram from a cold start when heavy gasoline is used.

In this example, the stability limit is searched at the time of starting, and the retard variable FAD at the timing when the stability limit is reached is obtained.
The fuel property index Fuel is calculated based on V.

The ignition timing is advanced from the stability limit during the period from the calculation of the fuel property index Fuel (ie, the timing of fuel property detection) to the time when the cooling water temperature Tw reaches the limit temperature LTW. As shown in FIG. 26, the amount of HC emission when the engine is out is smaller than that of the conventional device (shown by a broken line) (see a solid line). At a low temperature when heavy gasoline is used, the amount of HC emission by the area of the hatched region in FIG. 26 is smaller than that of the conventional device.

On the other hand, when the advance correction amount SADV is a fixed value SAD
V0, and the value of Fuel is a predetermined value Fuel0.
Heavy gasoline and a predetermined value Tw at which the cooling water temperature Tw is low.
When the matching is performed when the value is 0, the value of Fuel is set to a predetermined value Fuel1 by setting Tw0 constant based on Tw.
Even when heavy gasoline (Fuel1> Fuel0) is used, if the advance correction amount of SADV0 is used, the advance is insufficient, and the amount of reduction in the amount of HC emission when the engine is out is reduced. . Further, when the fuel value is heavy gasoline having a predetermined value Fuel0, the lead angle becomes insufficient even if the lead angle correction amount of SADV0 is used when Tw is a low temperature predetermined value Tw2 (Tw2> Tw0). In addition, the amount of decrease in the amount of HC emission when the engine is out is reduced.

On the other hand, in this example, the advance correction amount SA
The DV is not a fixed value, and the advance correction amount SADV increases as the value of Fuel decreases (as the fuel value increases) and the cooling water temperature Tw decreases, so that even if the fuel properties and water temperature conditions are different, excessive The advance correction amount SADV can be given without any shortage.

Further, the search for the stability limit in the temperature range of Tw <LTW is performed only when the stability limit itself is deviated due to a rapid rise in the cooling water temperature, so that the ignition timing is advanced from the stability limit. The squaring time can be made as long as possible, and accordingly, the amount of HC emission at the engine out can be reduced.

Further, since a sensor for detecting the fuel property is not provided, the cost is not increased.

FIGS. 27, 29 and 30 show a second embodiment.
FIGS. 27 and 29 correspond to FIG. 15, and FIG. 30 corresponds to FIG. Note that the same steps as those in the previous embodiment (first embodiment) are denoted by the same reference numerals.

In this example, a pressure sensor for detecting a fuel saturated vapor pressure GP in a fuel tank and a fuel saturated vapor temperature GT are used.
Is provided, and the fuel property index Fuel is calculated from these detected values.

FIG. 27 is a flowchart for calculating the fuel property index Fuel, which is executed only once at the time of starting. What is different from FIG. 15 is steps 101 and 102.

In step 101, the saturated vapor pressure GP of the fuel
And the saturated steam temperature GT, and in step 102, a fuel property index Fuel is obtained from these values by referring to a map having contents shown in FIG. 28. In step 32, a flag is set to indicate that the calculation of the fuel property index Fuel has been completed. Set the value of F to "1".

As shown in FIG. 28, if the saturated steam temperature GT is constant, the value of the fuel property index Fuel becomes larger (lighter) as the saturated vapor pressure GP becomes higher, and the value of the saturated vapor pressure GP becomes constant. In this case, the value becomes larger as the saturated steam temperature GT is lower.

FIG. 29 is a flowchart for searching the stability limit, which is executed in synchronization with the Ref signal at the time of starting. The content of the portion for searching for the stability limit is the same as in FIG. 15, and the flag F3 (initial value is “0”) at the timing when the stability limit is reached
Is set to "1" only in FIG. 15 (step 111).

FIG. 30 is a flowchart for performing ignition timing control in a normal state, and is executed in synchronization with the Ref signal. In FIG. 30, step 121 is newly added, and step 1
In step 21, the value of the flag F3 is checked, and if F3 = 1, it is determined that the search for the stability limit has already been performed, and step 4
Proceed to 1 or later. The reason why the step 121 is necessary is that in order to perform the advance angle control from the stability limit in the step 45, it is necessary to search the stability limit as a precondition.

In this example, unlike the previous embodiment (first embodiment), it is not necessary to control the fuel property index Fuel to the stability limit in order to calculate the fuel property index Fuel. Is calculated, the timing of starting the advance from the stability limit is earlier than in the previous embodiment. FIG. 31 shows a comparison with the first embodiment (see the broken line). In this example, the amount of HC emission at the time of engine out is smaller than that of the first embodiment by the area of the hatched region.

FIG. 32 shows a third embodiment.
Corresponds to 7.

The second embodiment detects values (saturated vapor pressure GP and saturated vapor temperature GT) correlated with the fuel properties and calculates the fuel property index Fuel from these detected values. Another value (refractive index of the fuel) correlated with the fuel property is detected, and the fuel property index Fuel is calculated from the detected value.

The configuration itself of the sensor element for detecting the refractive index of the fuel is known from Japanese Patent Application Laid-Open No. H01-017173. In FIG. 34, a sensor element 22 is provided in a fuel pipe 21. The arrow is the fuel flow direction.

In FIG. 34, the light from the light emitting diode 24 is converted into parallel light by the collimating lens 25 and is irradiated into the rod prism 26. Rod prism 26
The light that has passed through the inside is refracted at the interface with the fuel according to the ratio of the refractive indexes of the two, is reflected by the reflecting mirror 27, is refracted again at the interface with the fuel, and then is condensed by the condenser lens 28.
Is focused on a PSD (one-dimensional position detecting element) 29. PSD29 Ueno converging position is determined in accordance with the refractive index of the fuel, to obtain an output voltage V _F converts the photocurrent of PSD29 to voltage.

Here, in the output characteristics of FIG. 35, the point is B for normal gasoline and A for heavy gasoline.
Points. This is because the refractive index of gasoline has a relationship with the specific gravity of gasoline, and the specific gravity has a relationship with the octane number (that is, fuel properties) of gasoline.

[0106] Returning to Figure 32, reads the output voltage V _F in step 131, step 132 from the output voltage V _F
The fuel property index Fuel is obtained by referring to the table having the contents shown in FIG.

[0107] As shown in FIG. 33, the value of the Fuel is larger value as the output voltage V _F becomes smaller (becomes lighter). This (as will light), the more the refractive index than the characteristic of FIG. 35 decreases the output voltage V _F becomes smaller, to represent that the light as the value of the Fuel is increased, the value of the Fuel and output it is necessary to make showing the relationship between the voltage V _F in Figure 33.

Since the refractive index of the fuel is affected by the fuel temperature, a sensor 31 for detecting the fuel temperature is provided in the fuel pipe 21 (see FIG. 34), and correction can be made in accordance with the fuel temperature. . When showing the output characteristics with respect to the fuel temperature V _FT in Figure 36, for example, because when the fuel temperature V _FT is higher than the reference value is lower than the reference value the output voltage V _F is the difference between the reference value according to the characteristics of FIG. 36 By performing the output correction, the effect of the fuel temperature can be eliminated.

Also in this example, as in the second embodiment, the timing for calculating the fuel property index Fuel is earlier than in the first embodiment, and the amount of HC emission from the engine out is smaller than that in the first embodiment. .

FIG. 37 shows a fourth embodiment.
9 corresponds. This example corresponds to FIG.
The catalyst 9 provided in the exhaust manifold by adding 1,142
CAT (detected by a temperature sensor) and the catalyst activation temperature T50 (for example, 250 ° C.)
When ≦ T50, it is determined that the catalyst is not activated,
The retard control to the stability limit is performed (steps 142 and 46).

Note that T50 is a temperature at which the conversion of the catalyst becomes 50%. Since T50 is generally used as an index indicating that the catalyst has been activated, T50 is used here as the temperature at which the catalyst is activated.

If there is a catalyst in the exhaust manifold,
Activating the catalyst at an early stage is effective in reducing HC emission at the catalyst outlet. Although it has been described above that the influence of the retard of the ignition timing on the HC emission amount when the engine is out changes depending on the fuel properties and the temperature state of the engine, the exhaust temperature rises when the ignition timing is retarded. This does not depend on fuel properties or engine temperature conditions. Therefore, until the catalyst is activated,
At the expense of increased HC emissions from the engine out,
If the ignition timing is retarded to the stability limit, HC emission at the catalyst outlet can be reduced as a result.

FIG. 38 schematically shows, along a temporal flow, how the ignition timing control of this example will be performed when a cold start is performed using heavy gasoline. In this example, the ignition timing is first retarded to the stability limit in order to activate the catalyst as soon as the fuel property index Fuel is calculated after the start. Due to this retardation, the catalyst temperature CAT rapidly rises.

The catalyst temperature CAT is equal to the catalyst activation temperature T5.
After the temperature exceeds 0 (the catalyst is activated), it is more important to reduce the amount of HC emission at the engine out than to increase the exhaust gas temperature. Therefore, the ignition timing is advanced by an optimum amount from the stability limit. Corner.

After that, the cooling water temperature Tw becomes the boundary temperature LTW.
Is exceeded, the ignition timing is retarded again to the stability limit.

The time from the start timing to the calculation timing of the fuel property index Fuel is shown in FIG. 38 and FIG.
In comparison with FIG. 6, although FIG. 26 looks longer, both have different time scales and the actual time is almost the same.

In this example, at the time of cold start using heavy gasoline, when a catalyst is provided in the exhaust manifold near the engine out, ignition is performed until the catalyst is activated (catalyst temperature CAT exceeds T50). By controlling the timing to the stability limit, it is possible to reduce the amount of HC emission at the catalyst outlet during the cold start using heavy gasoline.

Note that NOx and CO are reduced regardless of fuel properties and temperature due to retarded ignition timing when the engine is out, and further reduced at the catalyst outlet due to early activation of the catalyst.

FIG. 39 shows a fifth embodiment.
7, steps 151 and 152 are added.

This embodiment is the same as the fourth embodiment in that both the temperature state of the engine and the catalyst temperature CAT are considered, but the catalyst is provided not at the exhaust manifold near the engine out but at the engine out. At a large distance (for example, behind the front tube of the exhaust pipe,
The mounting position is under the floor of the vehicle).

Unlike the fourth embodiment, when the catalyst is at a position distant from the engine out, it takes time for the catalyst to be activated after a cold start, so that the catalyst will be activated in the same manner as in the fourth embodiment. If the ignition timing is retarded to the stability limit, the amount of HC emission at the catalyst outlet will rather increase. Therefore, in FIG. 39, even if the catalyst temperature CAT is equal to or lower than the catalyst activation temperature T50 in step 142, if the cooling water temperature Tw is equal to or lower than the predetermined value HCTW (for example, 30 ° C.) in step 152, it takes time to activate the catalyst. When it is determined that this is the case, the routine proceeds to step 45 in order to reduce the amount of HC emission when the engine is out, and the ignition timing is advanced from the stability limit.

Also in this example, FIG. 40 schematically shows a temporal flow of the ignition timing control when cold starting is performed using heavy gasoline, corresponding to FIG. In this example, the ignition timing is advanced from the stability limit first from the timing at which the fuel property index Fuel is calculated, thereby reducing the amount of HC emission from the engine out during cold using heavy gasoline.

Thereafter, the cooling water temperature Tw is reduced to a predetermined value HCTW.
After reaching, the ignition timing is retarded to the stability limit in order to activate the catalyst early, assuming that the engine has warmed up to some extent.

Thereafter, when the catalyst temperature CAT exceeds the catalyst activation temperature T50, the ignition timing is advanced again in order to reduce the amount of HC emission from the engine out.

Thereafter, the cooling water temperature Tw becomes the limit temperature LTW.
After that, since the HC emission amount is reduced by retarding the ignition timing, the ignition timing is retarded to the stability limit.

As described above, by controlling the ignition timing in four stages, at the time of cold start using heavy gasoline,
Even when the catalyst is not activated very quickly because the catalyst is located far away from the engine out, the HC emission can be reduced.

FIG. 41 shows a sixth embodiment in which the activation temperature T50 of the catalyst is set not as a fixed value but as a variable value.

When the catalyst is new, T50 has a specific value (constant value) depending on the type of the catalyst, but T50 tends to gradually increase due to deterioration of any of the catalysts. Therefore, when the catalyst is in a deteriorated state, FIG.
Although the catalyst temperature CAT has not yet reached T50 in FIG.
And the activation of the catalyst becomes insufficient.

Therefore, in this example, as shown in FIG. 41, T50 ← T50f + k × L (9) where T50 increases as the deterioration of the catalyst progresses, where T50f: T50 k when the catalyst is new. : Positive constant L: The activation temperature T50 of the catalyst is calculated by the following equation (steps 161 and 162).

The accumulated running distance L in equation (9) is representative of the operating history of the catalyst since it was new, and is not limited to this, and may be an integrated value of the engine speed, an integrated value of the operating time, or the like. Absent.

In this example, even when the catalyst is deteriorated during the cold start using heavy gasoline, the catalyst is quickly activated without excess or shortage, thereby reducing the amount of HC emission at the catalyst outlet. be able to.

[0132]

According to the first invention, means for searching for a stability limit by retarding the ignition timing, means for detecting the fuel property of the fuel used at the time of starting, and HC emission by retarding the ignition timing are provided. Decrease the limit engine temperature to the limit temperature
Means for calculating according to the detected value of the fuel property, and means for detecting an engine temperature, and means for determining whether the engine temperature is the one or limiting temperature or less than the limit temperature, the determination Means for advancing the ignition timing from the stability limit searched by the stability limit search means in a temperature range lower than the limit temperature based on the result; and, when the temperature range is equal to or higher than the limit temperature based on the determination result, the stability limit search means. A means for retarding the ignition timing to the searched stability limit is provided, so even when starting with low temperature using heavy gasoline,
It is possible to reduce the amount of HC emission when the engine is out.

According to a second aspect of the present invention, there is provided a means for searching for a stability limit by retarding the ignition timing, a means for detecting a catalyst temperature of a catalyst interposed near an engine out, and a means for detecting the catalyst temperature. First temperature range determining means for determining whether the temperature is equal to or lower than the activation temperature or exceeding the activation temperature; and Means for retarding to the stability limit searched by the degree limit search means, means for detecting the fuel property of the fuel used at the time of starting, and the engine temperature at which HC emission decreases due to retardation of ignition timing to the limit temperature.
Means for calculating according to the detected value of the fuel property as,
Means for detecting an engine temperature, second temperature range determining means for determining whether the engine temperature is lower than or equal to the limit temperature, and a determination result of the second temperature range determining means, Means for advancing the ignition timing from the stability limit searched by the stability limit search means in a temperature range exceeding the activation temperature and a temperature range below the limit temperature from the determination result of the first temperature range determination means; (2) means for delaying the ignition timing again to the stability limit searched by the stability limit search means when the temperature range is equal to or higher than the limit temperature from the determination result of the temperature range determination means, so that heavy gasoline is used. When a catalyst is interposed in the vicinity of the engine at the time of low temperature start, the amount of HC emission at the catalyst outlet can be further reduced.

According to a third aspect of the present invention, there is provided a means for searching for a stability limit by retarding the ignition timing, a means for detecting an engine temperature, and the engine temperature being lower than a predetermined value or higher than a predetermined value. A third temperature range determining means for determining whether the ignition timing is advanced from the stability limit searched by the stability limit searching means in a temperature range less than a predetermined value based on the determination result of the third temperature range determining means. Means for detecting a catalyst temperature of a catalyst interposed far from the engine out, and a first temperature range for determining whether the catalyst temperature is lower than or higher than an activation temperature of the catalyst. Determining means for determining the ignition timing in a temperature range equal to or higher than a predetermined value and equal to or lower than the activation temperature based on the determination result of the first temperature range determining means and the determination result of the third temperature range determining means. Search for Was and stability means to retard to the limit, and means for detecting a fuel property of fuel used during start-up, engine limits the HC emission amount decreases by retarding the ignition timing
Means for calculating according to the detected value of the fuel property the emission temperature as the limit temperature, the or detected <br/> engine temperature of the engine temperature detecting means is the one or limiting temperature or less than the limit temperature Second temperature range determining means for determining,
The stability limit searched by the stability limit search means in the temperature range exceeding the activation temperature and below the limit temperature based on the determination result of the second temperature range determination means and the determination result of the first temperature range determination means. Means for advancing the ignition timing from the second means, and means for again retarding the ignition timing to the stability limit searched by the stability limit search means when the temperature range is equal to or higher than the limit temperature based on the result of the determination by the second temperature range determination means. Therefore, when starting the engine at low temperature using heavy gasoline, even if the catalyst is not activated very quickly because the catalyst is interposed far away from the engine out, HC emission at the catalyst outlet The amount can be reduced.

In a fourth aspect based on the second aspect or the third aspect, the means for setting the activation temperature includes means for calculating an operation history from the time of new catalyst, and means for calculating the activation history as the operation history becomes longer. Since it is a means for calculating the activation temperature of the catalyst by correcting the activation temperature of the catalyst when it is new on the larger side, even when the catalyst is deteriorated during cold start using heavy gasoline, Early activation of the deteriorated catalyst can be performed without excess or shortage.

According to a fifth aspect of the present invention, in any one of the first to fourth aspects of the invention, the advance amount is a value that increases as the detected value of the fuel property becomes heavier. As long as the engine temperature is the same as when the correction amount is matched, even if the fuel properties are different, the advance correction amount can be given without excess or deficiency.

According to a sixth aspect of the present invention, in any one of the first to fourth aspects, since the advance amount is a value that increases as the engine temperature decreases, the advance angle correction amount is matched. If the fuel properties are the same, the advance correction amount can be given without excess or deficiency even if the engine temperature is different.

According to a seventh aspect of the present invention, in any one of the first to sixth aspects of the present invention, only when there is a sharp rise in the engine temperature during the advance from the stability limit, the stability is reduced. Is advanced and the stability limit is searched, so that the time when the ignition timing is advanced from the stability limit at a low temperature using heavy gasoline becomes longer, and the HC emission at the time of engine out is increased accordingly. Can be reduced.

In an eighth aspect based on any one of the first to seventh aspects, the fuel property detecting means sets a basic advance value at a stability limit of heavy gasoline, A means for calculating a retard amount of a gradually increasing value; a means for calculating a rotation fluctuation rate of the engine; a means for determining whether the rotation fluctuation rate is equal to or less than a predetermined value or exceeding a predetermined value; Means for calculating the ignition advance value by correcting the basic advance value with the retard amount when the rotation fluctuation rate is equal to or less than a predetermined value from the result; means for performing ignition with the ignition advance value; Means for calculating a fuel property index based on the retard amount when the rotation fluctuation rate exceeds a predetermined value.Therefore, there is no need to provide a sensor for directly detecting the fuel property, and the cost can be increased. Absent.

In a ninth aspect based on the eighth aspect, the fuel property index calculating means increases as the retard amount increases based on the retard amount when the rotation fluctuation rate exceeds a predetermined value. Means for calculating the basic fuel property index of the value and means for calculating the fuel property index by correcting the basic fuel property index to a value that increases as the engine temperature decreases. The property index can be given without excess or deficiency.

According to a tenth aspect, in any one of the first to seventh aspects, the fuel property detecting means is a sensor for directly detecting the fuel property. At the time of low temperature start, the timing of starting the advance from the stability limit becomes earlier than when estimating the fuel property from the engine rotation fluctuation rate, and the HC emission can be reduced accordingly.

[Brief description of the drawings]

FIG. 1 is a system diagram of an embodiment.

FIG. 2 is a flowchart for explaining calculation of an effective pulse width Te.

FIG. 3 is a flowchart for explaining calculation of fuel injection pulse width Ti and execution of injection.

FIG. 4 is a characteristic diagram showing a relationship between a main combustion period θ _10-90 and an ignition timing.

5 is a characteristic diagram showing a main combustion end timing theta ₉₀ and the ignition timing relationship.

6 is a characteristic diagram showing the relationship between the HC discharge quantity and the main combustion period theta _10-90 when the main combustion end timing theta ₉₀ was constant.

7 is a characteristic diagram showing the relationship between HC emissions and main combustion end timing theta ₉₀ when the primary combustion period theta _10-90 was constant.

FIG. 8 is a characteristic diagram of the amount of HC emission when the cooling water temperature is high.

FIG. 9 is a characteristic diagram of HC emission at low temperature when heavy gasoline is used.

FIG. 10 is a schematic diagram of each HC emission at the end of main combustion and at engine out.

FIG. 11 is a schematic diagram of each HC emission at the end of main combustion and when the engine is out when the cooling water temperature is high.

FIG. 12 is a schematic diagram of each HC emission amount at the end of main combustion at low temperature and engine out when heavy gasoline is used.

FIG. 13 is a characteristic diagram of HC emission and surge torque with respect to ignition timing at low temperature when heavy gasoline is used.

FIG. 14 is a characteristic diagram showing ignition timing control with respect to fuel properties and cooling water temperature.

FIG. 15 is a flowchart for explaining calculation of a fuel property index Fuel at the time of starting.

FIG. 16 is a characteristic diagram of a basic advance value BADV.

FIG. 17 is a characteristic diagram of a water temperature correction amount CADV.

FIG. 18 is a characteristic diagram of a fuel property index Fuel.

FIG. 19 is a flowchart for explaining ignition timing control in a normal state.

FIG. 20 is a characteristic diagram of a limit temperature LTW.

FIG. 21 is a flowchart for explaining advance angle control from a stability limit.

FIG. 22 is a characteristic diagram of the advance correction amount SADV.

FIG. 23 is a flowchart for explaining retard control to a stability limit.

FIG. 24 is a waveform chart for explaining calculation of a rotation fluctuation rate σn.

FIG. 25 is a flowchart illustrating the calculation of a retard variable FADV.

FIG. 26 is a waveform chart showing changes in the cooling water temperature Tw and the amount of HC emission from a cold start when heavy gasoline is used.

FIG. 27 is a fuel property index Fuel at the start of the second embodiment.
6 is a flowchart for explaining the calculation of.

FIG. 28 is a characteristic diagram of a fuel property index Fuel of the second embodiment.

FIG. 29 is a flowchart illustrating a search for a stability limit at the time of startup according to the second embodiment.

FIG. 30 is a flowchart for explaining ignition timing control in a normal state according to the second embodiment.

FIG. 31 is a change waveform diagram of the amount of HC emission from a cold start when the heavy gasoline of the second embodiment is used.

FIG. 32 is a fuel property index Fuel at the start of the third embodiment.
6 is a flowchart for explaining the calculation of.

FIG. 33 is a characteristic diagram of a fuel property index Fuel of the third embodiment.

FIG. 34 is a configuration diagram of a sensor element for detecting a refractive index of fuel according to a third embodiment.

FIG. 35 is a characteristic diagram of the output voltage V _F of the sensor element with respect to the refractive index of the third embodiment.

FIG. 36 is a characteristic diagram showing the relationship between the output voltage V _F and the fuel temperature V _FT sensor elements of the third embodiment.

FIG. 37 is a flowchart for explaining ignition timing control in a normal state of the fourth embodiment.

FIG. 38 is a schematic diagram along a time flow of ignition timing control from a cold start using heavy gasoline of the fourth embodiment.

FIG. 39 is a flowchart for explaining ignition timing control in a normal state in the fifth embodiment.

FIG. 40 is a schematic diagram along a time flow of ignition timing control from a cold start using heavy gasoline of the fifth embodiment.

FIG. 41 is a flowchart for explaining calculation of an activation temperature T50 of a catalyst according to a sixth embodiment.

FIG. 42 is a characteristic diagram of the HC discharge amount and the surge torque with respect to the ignition timing at a high temperature in the conventional example.

FIG. 43 is a characteristic diagram showing a relationship between HC emission amount and ignition timing at low temperature in a conventional example.

FIG. 44 is a characteristic diagram showing a relationship between HC emission amount and ignition timing at a high temperature in a conventional example.

FIG. 45 is a diagram corresponding to claims of the first invention.

FIG. 46 is a diagram corresponding to the claims of the second invention.

FIG. 47 is a diagram corresponding to claims of the third invention.

FIG. 48 is a diagram corresponding to the claims of the fourth invention.

FIG. 49 is a diagram corresponding to the claims of the eighth invention.

FIG. 50 is a diagram corresponding to a claim of the ninth invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 ECU 12 Air flow meter 13 Crank angle sensor 41 Stability limit search means 42 Fuel property detection means 43 Limit temperature calculation means 44 Engine temperature detection means 45 Temperature range determination means 46 Advancement means from stability limit 47 Stability limit Retarding means 51 catalyst temperature detecting means 52 first temperature range determining means 53 retarding means to stability limit 54 second temperature range determining means 61 third temperature range determining means 62 advancing means from stability limit 63 catalyst temperature Detecting means 71 Activation temperature setting means 72 Operation history calculating means 73 Activation temperature calculating means 81 Basic advance value setting means 82 Retardation amount calculating means 83 Rotational variation rate calculating means 84 Judging means 85 Ignition advance value calculating means 86 Ignition Means 87 Fuel property index calculating means 91 Basic fuel property index calculating means 92 Fuel property index calculating means

────────────────────────────────────────────────── ─── front page continued (51) Int.Cl. ⁷ identifications FI F02D 45/00 364 G01K 7/00 321J G01K 7/00 321 G01N 21/41 Z G01N 21/41 F02P 5/15 a E L ( 58) Field surveyed (Int.Cl. ⁷ , DB name) F02P 5/15 F02D 45/00 312 F02D 45/00 362 F02D 45/00 364

Claims (10)

(57) [Claims] 1. A means for searching the stability limit by retarding the ignition timing, means for detecting a fuel property of fuel used during start-up, ene limit the HC emission amount decreases due to retardation of the ignition timing
Means for calculating a gin temperature as a limit temperature in accordance with the detected value of the fuel property; means for detecting an engine temperature; means for determining whether the engine temperature is lower than the limit temperature or higher than the limit temperature Means for advancing the ignition timing from the stability limit searched by the stability limit search means in a temperature range less than the limit temperature based on the determination result; and Means for retarding the ignition timing to the stability limit searched by the limit search means. 2. A means for searching a stability limit by retarding an ignition timing, a means for detecting a catalyst temperature of a catalyst interposed near an engine out, and whether the catalyst temperature is equal to or lower than an activation temperature of the catalyst. A first temperature range determining means for determining whether the temperature has exceeded an activation temperature; and a stability limit search means for determining an ignition timing from immediately after starting in a temperature range equal to or lower than the activation temperature based on a determination result of the first temperature range determining means. and searched stability means to retard to the limit, and means for detecting a fuel property of fuel used during start-up, ene limit the HC emission amount decreases due to retardation of the ignition timing
Means for calculating according gin temperature value detected by the fuel property as a temperature limit, the determined means for detecting an engine temperature, whether the engine temperature is the one or limiting temperature or less than the limit temperature A second temperature range determining means, and the stability limit in a temperature range exceeding the activation temperature and less than the limit temperature from the determination result of the second temperature range determining means and the determination result of the first temperature range determining means. A means for advancing the ignition timing from the stability limit searched by the search means; and a stability limit searched by the stability limit search means when the temperature range is equal to or higher than the limit temperature based on the determination result of the second temperature range determination means. An ignition timing control device for an engine, further comprising means for retarding the ignition timing. 3. A means for searching a stability limit by retarding an ignition timing, a means for detecting an engine temperature, and determining whether the engine temperature is less than a predetermined value or not less than a predetermined value. Third temperature range determining means; means for advancing the ignition timing from the stability limit searched by the stability limit searching means in a temperature range less than a predetermined value from the determination result of the third temperature range determining means; Means for detecting a catalyst temperature of a catalyst interposed at a position far from the outside; first temperature range determining means for determining whether the catalyst temperature is equal to or lower than the activation temperature of the catalyst or has exceeded the activation temperature; From the determination result of the first temperature range determining means and the determination result of the third temperature range determining means, the ignition timing is searched for by the stability limit searching means in a temperature range equal to or higher than a predetermined value and equal to or lower than the activation temperature. Every time Means for retarding to the field, means for detecting a fuel property of fuel used during start-up, ene limit the HC emission amount decreases due to retardation of the ignition timing
Means for calculating a gin temperature as a limit temperature in accordance with the detected value of the fuel property; and a second for determining whether the engine temperature detected by the engine temperature detection means is lower than the limit temperature or higher than the limit temperature. Temperature range determining means, and the stability limit search in a temperature range exceeding the activation temperature and below the limit temperature based on the determination result of the second temperature range determining means and the determination result of the first temperature range determining means. Means for advancing the ignition timing from the stability limit searched by the means; and, when the temperature range is equal to or higher than the limit temperature based on the determination result of the second temperature range determination means, ignition is performed to the stability limit searched by the stability limit search means. An ignition timing control device for an engine, further comprising means for retarding the timing. 4. The means for setting the activation temperature includes a means for calculating an operation history of the catalyst when it is new, and a means for correcting the activation temperature when the catalyst is new when the operation history becomes longer. The ignition timing control device for an engine according to claim 2 or 3, further comprising means for calculating an activation temperature of the catalyst. 5. The ignition timing control device for an engine according to claim 1, wherein the advance amount is a value that increases as the detected value of the fuel property increases. . 6. The engine ignition timing control device according to claim 1, wherein the advance amount is a value that increases as the engine temperature decreases. 7. The advancement from the stability limit is stopped and the stability limit is searched only when there is a sudden rise in engine temperature during the advancement from the stability limit. 7. The ignition timing control device for an engine according to any one of 1 to 6. 8. The fuel property detecting means includes means for setting a basic advance value at the stability limit of heavy gasoline, means for calculating a gradually increasing value of the retard amount, and a rate of rotation change of the engine. Calculating means for determining whether the rotation variation rate is equal to or less than a predetermined value or exceeding the predetermined value. Based on the determination result, when the rotation variation rate is equal to or less than the predetermined value, the basic advance value is set to the retard angle. Means for calculating an ignition advance value by compensating for the amount of fuel, means for igniting with this ignition advance value, and fuel based on the retard amount when the rotation fluctuation rate exceeds a predetermined value based on the determination result. The engine ignition timing control device according to any one of claims 1 to 7, comprising means for calculating a property index. 9. The fuel property index calculating means calculates a basic fuel property index of a value which increases as the retard amount increases based on the retard amount when the rotation fluctuation rate exceeds a predetermined value. And means for correcting the basic fuel property index to a value that increases as the engine temperature decreases, and calculating the fuel property index.
An ignition timing control device for an engine according to Claim 1. 10. An engine ignition timing control apparatus according to claim 1, wherein said fuel property detecting means is a sensor for directly detecting the fuel property.