JP2002242739A - Control device for diesel engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively prevent a misfire right after a low temperature start and prevent discharge of white smoke and a rotational fluctuation of an engine. SOLUTION: In idling during a warm up, when an air-fuel ratio AFR exceeds a predetermined upper limit AFRUPR, a target idle rotational frequency is increased by the predetermined rotational frequency (an idle rotational frequency correction amount Nup of S14), and the air-fuel ratio AFR is lowered by increasing a fuel injection quantity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control apparatus for a diesel engine which prevents or effectively suppresses the emission of white smoke immediately after a low temperature start.

[0002]

2. Description of the Related Art In general, in a control system for a diesel engine, a starting mode is defined as a period from cranking by a starter motor to a predetermined engine speed. The target fuel injection amount is set with reference to a map corresponding to the engine temperature (cooling water temperature).

When the engine speed reaches the predetermined speed, the engine is switched to a normal operation mode, and it is determined whether or not the engine is in an idling operation mode in accordance with an accelerator opening and the like. When it is determined that the engine is in the idling operation mode, the target idle speed is set based on the engine temperature and the battery voltage, and the engine speed detected by the rotation speed sensor is substantially equal to the target idle speed. The fuel injection amount is feedback-controlled so as to match.

Here, when the engine is started in a low temperature state, the combustion chamber temperature is low, and the ignition and combustion of the fuel are likely to be incomplete, so that the misfire deteriorates the operability and generates white smoke. There is a problem that it is easy to do. Japanese Unexamined Patent Publication No. 6-294327 discloses a solution to this problem, in which a mechanically driven supercharger is provided, and a valve interposed in a passage for bypassing a working gas of the supercharger is changed according to an operating state. It discloses a method of opening and closing by opening and closing. That is, in the operation state immediately after the low temperature start, the combustion chamber temperature is low, and white smoke is easily generated, the valve is closed and the work (load) of the supercharger is maximized, so that the warm-up is quickly performed. ,
This reduces white smoke emissions.

[0005]

However, this method is effective in that the amount of emitted white smoke is reduced by shortening the warm-up time. However, this method is a method for suppressing the generation of white smoke itself. Are not always effective. It is for the following reasons. When the supercharger is driven, the amount of intake air increases due to an increase in intake pressure. Here, even if the fuel injection amount is increased in accordance with the increase in the work of the turbocharger, the air-fuel ratio is rather increased due to the increase in the intake air amount. If the air-fuel ratio increases during warm-up, the fuel falls into a state in which ignition is impossible, which may cause deterioration of white smoke and fluctuations in engine rotation.

Accordingly, an object of the present invention is to provide a diesel engine control device capable of effectively preventing white smoke from being emitted by effectively avoiding misfire immediately after a low temperature start.

[0007]

Therefore, a diesel engine control apparatus according to the first aspect of the present invention is a control apparatus for a diesel engine that feedback-controls an engine speed to a target idle speed during idle operation. A misfire state detecting means for detecting the occurrence of a misfire state during idling operation during warm-up, and when the misfire state detection means detects the occurrence of a misfire state during idling operation during warm-up, Air-fuel ratio lowering means for lowering the air-fuel ratio by feedback control.

[0008] A control apparatus for a diesel engine according to a second aspect of the invention is characterized in that the misfire state detecting means detects the occurrence of the misfire state based on an air-fuel ratio. According to a third aspect of the invention, there is provided a diesel engine control device, wherein the misfire state detection means has an air-fuel ratio of the first type.
When the air-fuel ratio exceeds a predetermined air-fuel ratio, the occurrence of the misfire state is detected.

According to a fourth aspect of the present invention, in the control apparatus for a diesel engine, the misfire state detecting means variably sets the first predetermined air-fuel ratio in accordance with a current combustion chamber temperature. Features. The diesel engine control device according to claim 5, wherein the second predetermined air-fuel ratio is lower than the first predetermined air-fuel ratio after the misfire state detecting means detects the occurrence of the misfire state. , The occurrence of the misfire state is detected continuously.

According to a sixth aspect of the present invention, in the control apparatus for a diesel engine, the misfire state detection means variably sets the second predetermined air-fuel ratio in accordance with a current combustion chamber temperature. Features. A control apparatus for a diesel engine according to a seventh aspect of the invention is characterized in that the misfire state detecting means detects the occurrence of the misfire state based on a fuel injection amount.

In a preferred embodiment of the present invention, the misfire state detecting means detects the occurrence of the misfire state when the fuel injection amount falls below a first predetermined injection amount. It is characterized by the following. A control apparatus for a diesel engine according to a ninth aspect of the invention is characterized in that the misfire state detection means variably sets the first predetermined injection amount in accordance with a current combustion chamber temperature. .

According to a tenth aspect of the present invention, in the control apparatus for a diesel engine, after the misfire state detecting means detects the occurrence of the misfire state, the second fuel injection amount is larger than the first predetermined injection amount. The occurrence of the misfire state is continuously detected until the predetermined injection amount is reached.
The control apparatus for a diesel engine according to the present invention is characterized in that the misfire state detecting means variably sets the second predetermined injection amount in accordance with a current combustion chamber temperature. .

A control apparatus for a diesel engine according to a twelfth aspect of the invention is characterized in that the air-fuel ratio lowering means lowers the air-fuel ratio in relation to the current combustion chamber temperature. A diesel engine control device according to a thirteenth aspect of the invention is characterized in that the air-fuel ratio lowering means decreases the amount of the air-fuel ratio reduction in accordance with an increase in the temperature of the combustion chamber.

A control apparatus for a diesel engine according to a fourteenth aspect of the present invention is characterized in that the air-fuel ratio lowering means increases the target idle speed by a predetermined speed when the air-fuel ratio is lowered. . According to a fifteenth aspect of the present invention, in the diesel engine control device, the air-fuel ratio lowering unit sets the predetermined rotational speed based on a current combustion chamber temperature.

A control apparatus for a diesel engine according to a sixteenth aspect of the present invention includes an auxiliary device driven by an engine drive shaft, wherein the air-fuel ratio lowering means reduces the air-fuel ratio when the air-fuel ratio is reduced. The driving load is increased by a predetermined load amount. The control device for a diesel engine according to the invention according to claim 17, wherein the air-fuel ratio lowering unit includes:
The predetermined load amount is set based on a current combustion chamber temperature.

A control apparatus for a diesel engine according to the present invention is characterized in that the misfire state detecting means determines whether or not the engine is being warmed up based on the temperature of the combustion chamber. A diesel engine control device according to a nineteenth aspect of the present invention is characterized by including a combustion chamber temperature estimating means for estimating the combustion chamber temperature based on a cooling water temperature and an elapsed time after starting.

[0017]

According to the first aspect of the present invention, when the occurrence of a misfire state during idle operation during warm-up is detected,
Since the air-fuel ratio is configured to be lower than the air-fuel ratio for performing feedback control to the target idle speed, it is possible to maintain the ignitable air-fuel ratio when the engine is started in a low temperature state, thereby avoiding misfiring. In addition, the emission of white smoke and fluctuations in engine speed can be prevented.

According to the second aspect of the present invention, the occurrence of a misfire state can be accurately detected based on the air-fuel ratio. According to the third aspect of the invention, the occurrence of the misfire state can be easily detected by a simple comparison with the first predetermined air-fuel ratio. Furthermore, according to the fourth aspect of the invention, the first predetermined air-fuel ratio is variably set in accordance with the current combustion chamber temperature, so that the detection accuracy can be improved and misfire can be reliably avoided. It becomes possible.

According to the fifth aspect of the present invention, when the lowering of the air-fuel ratio is stopped due to the second predetermined air-fuel ratio reaching the relatively low air-fuel ratio, the air-fuel ratio at that time and the first air-fuel ratio are reduced. It is possible to provide a sufficient margin between the predetermined air-fuel ratio. This prevents the air-fuel ratio from reaching the first predetermined air-fuel ratio immediately thereafter. Therefore, since the air-fuel ratio lowering means does not excessively reduce and stop the air-fuel ratio, a stable combustion state can be obtained.

Further, according to the invention described in claim 6,
Since the second predetermined air-fuel ratio is variably set in accordance with the current combustion chamber temperature, a margin between the first predetermined air-fuel ratio and the first predetermined air-fuel ratio can be made suitable for the current situation. According to the invention described in claim 7, the occurrence of a misfire state can be easily detected based on the fuel injection amount, and the control logic for implementing the present invention is simplified. It becomes possible.

According to the present invention, the occurrence of a misfire state can be easily detected by a simple comparison with the first predetermined injection amount. Furthermore, according to the ninth aspect of the present invention, the first predetermined injection amount is variably set in accordance with the current combustion chamber temperature, so that the detection accuracy can be improved and misfire can be reliably avoided. It becomes possible.

According to the tenth aspect of the present invention, when the decrease in the air-fuel ratio is stopped because the fuel injection amount has reached the second predetermined injection amount, which is relatively large, the fuel injection amount at that time and the fuel injection amount It is possible to provide a sufficient margin between the predetermined injection amount and the predetermined injection amount. Thus, it is possible to prevent the fuel injection amount from reaching the first predetermined injection amount immediately thereafter. Therefore, the air-fuel ratio is not excessively reduced and stopped by the air-fuel ratio lowering means, so that a stable combustion state can be obtained.

Further, according to the eleventh aspect of the present invention, the second predetermined injection amount is variably set in accordance with the current combustion chamber temperature. The margin can be made suitable for the current situation. Claim 12
According to the invention described in (1), the air-fuel ratio is reduced in relation to the current combustion chamber temperature, and in particular, as in the invention according to claim 13, the amount of the decrease is reduced in accordance with the increase in the combustion chamber temperature. Thus, it is possible to reliably avoid misfire and prevent unnecessary deterioration of fuel efficiency due to unnecessary decrease in air-fuel ratio.

According to the fourteenth aspect of the present invention, the fuel injection amount is increased with the feedback control to the target idle speed after the engine speed is increased.
The air-fuel ratio can be easily reduced. According to the invention described in claim 15, by setting the increase amount of the target idle speed based on the current combustion chamber temperature, misfire can be reliably avoided and the temperature of the combustion chamber becomes relatively high. Therefore, deviation from the original target idle speed can be suppressed.

According to the present invention, by lowering the air-fuel ratio by increasing the driving load of the auxiliary equipment, even if the fuel injection amount is increased, the engine speed can be reduced from the target idle speed. Can be suppressed. Therefore, when the clutch is connected or the range is changed from the N range to the D range in the automatic mode, the operability and the operability are not deteriorated.

According to the seventeenth aspect of the invention, the amount of increase in the auxiliary equipment load is set based on the current combustion chamber temperature, so that the auxiliary equipment load is increased as much as necessary to avoid misfire, and the engine is driven. Unnecessary consumption of power can be prevented. Claim 1
According to the invention described in Item 8, it is possible to accurately determine whether the vehicle is warming up based on the temperature of the combustion chamber.

According to the nineteenth aspect, the temperature of the combustion chamber can be easily and relatively accurately estimated based on the temperature of the cooling water and the elapsed time after the start.

[0028]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a first embodiment of the present invention.
1 schematically shows a configuration of a control device of a diesel engine (hereinafter, referred to as “engine”) 1 according to the embodiment. In FIG. 1, the engine 1 includes a common rail fuel injection system including a supply pump (not shown), a common rail 2 and an injector 3. Here, the injector 3 is opened and closed by an electromagnetic valve based on a fuel injection control signal from an electronic control unit 11 described later, and turns on and off the fuel injection.

An air-fuel ratio sensor 21 for detecting an air-fuel ratio AFR of the exhaust gas is attached to the exhaust passage 4 from the combustion chamber of the engine 1. An electronic control unit (hereinafter referred to as “ECU”) 11 includes an air-fuel ratio sensor 2.
1, the engine speed sensor 22,
Detection signals from various operation state detection sensors including the accelerator opening sensor 23 and the water temperature sensor 24 are input. EC
U11 has a function of calculating a target fuel injection amount of the injector 3 based on these detection signals.

Further, the ECU 11 calculates the opening time of the solenoid valve of the injector 3 based on the calculated target fuel injection amount and the pressure in the common rail 2 (detected by a pressure sensor (not shown)). It is output as an operation command signal (fuel injection control signal) to the solenoid valve. Next, the ECU
The eleventh function will be described with reference to the flowcharts shown in FIGS. These flowcharts show the control contents during the idling operation of the engine 1.

Step (hereinafter simply referred to as "S") 1
Then, the engine speed Ne detected by the engine speed sensor 22, the accelerator opening Acc detected by the accelerator opening sensor 23, the cooling water temperature (hereinafter referred to as “water temperature”) Tw detected by the water temperature sensor 24, and Tw. The air-fuel ratio AFR detected by the air-fuel ratio sensor 21 is read.

At S2, referring to the map having the tendency shown in FIG. 4, based on the water temperature Tw and the elapsed time after the engine is started (can be automatically measured by the ECU 11 having a counter function) TIM. Combustion chamber temperature T
Estimate CW. This map is set so that the estimated value of the combustion chamber temperature TCW increases as the water temperature Tw increases and the elapsed time TIM increases. S2
Constitutes a combustion chamber temperature estimating means according to the present invention.

In step S3, referring to the table having the tendency shown in FIG. 5, based on the combustion chamber temperature TCW, the air-fuel ratio upper limit value AFR as a threshold value for detecting the occurrence of a misfire state.
Set the UPR. This table shows the combustion chamber temperature TCW
Is higher, the air-fuel ratio upper limit value AFRUP at that time
R is set to a large value (toward the lean side). The air-fuel ratio upper limit AFRUPR corresponds to a first predetermined air-fuel ratio according to the present invention.

In S4, the basic target idle speed Nidleb is set based on the water temperature Tw with reference to the table having the tendency shown in FIG. In S5, it is determined whether or not the engine 1 is being warmed up by comparing the combustion chamber temperature TCW with a predetermined combustion chamber temperature TCW1 for determining a warm-up state. The combustion chamber temperature TCW is equal to a predetermined temperature T
If it is smaller than CW1, it is determined that the engine 1 is being warmed up, the process proceeds to S6, and after setting an idle speed correction amount Nup for a target idle speed correction described later, the process proceeds to S6.
Proceed to 8.

On the other hand, if the combustion chamber temperature TCW is equal to or higher than the predetermined temperature TCW1 in S5, it is determined that the warm-up of the engine 1 has been completed, and the process proceeds to S7, in which the idle speed correction amount Nup is set to 0. , To S8. In S8, the corrected idle speed Nidle (which is equal to the basic target idle speed Nidleb after the warm-up is completed) is obtained by adding the idle speed correction amount Nup set in S6 to the basic target idle speed Nidleb. . As a result, the engine 1 is adjusted to the corrected idle speed Nidle.

In step S9, the idle speed correction amount Nup and a flag (which is an index for identifying that the target idle speed correction is being performed, and is initially set to 0) are stored in the memory. Write to. Next, the contents of the above-described S6 (setting of the idle rotation speed correction amount Nup) will be described in detail with reference to FIG.

In S11, it is determined whether or not the target idle speed correction flag FLAG is 0. Since the initial value of FLAG is 0, the process proceeds to S12. In S12, it is determined whether or not the current air-fuel ratio AFR is higher than the air-fuel ratio upper limit value AFRUPR. The air-fuel ratio AFR is equal to the air-fuel ratio upper limit value AFRU
If it is equal to or less than PR, it is determined that the occurrence of the misfire state has not been detected, the process proceeds to S13, the idle speed correction amount Nup is set to 0, and the routine returns. On the other hand, when the current air-fuel ratio AFR is higher than the air-fuel ratio upper limit value AFRUPR, it is determined that the occurrence of the misfire state has been detected, and the process proceeds to S14.

It should be noted that S12 can also include the contents of the warm-up determination in S5. That is, in S3 (FIG. 5), the air-fuel ratio upper limit AF is set within the range of TCW ≧ TWC1.
If RUPR is always set to the maximum value,
When TCW ≧ TWC1, as a result of the determination in S12, the flow always proceeds to S13. Therefore, the processing of S5 (and the accompanying S7) can be omitted.

In S14, the idling speed correction amount Nup is set based on the combustion chamber temperature TCW with reference to the tendency table shown in FIG. This table shows that the higher the combustion chamber temperature TCW, the smaller the idle rotation speed correction amount Nup is set to a smaller value, in other words, the idle rotation speed correction amount Nup decreases as the combustion chamber temperature TCW increases. Is set to However, the idle rotation speed correction amount Nup can be set to be constant irrespective of the combustion chamber temperature TCW.

Further, after changing the flag FLAG to 1 in S15, the routine returns. Flag FLAG
Is changed to 1, since a negative determination is made in S11, the flow proceeds to S16. In S16,
It is determined whether the difference between the air-fuel ratio upper limit value AFRUPR and the air-fuel ratio AFR is larger than a predetermined value AFm. This judgment is
It is determined whether or not the air-fuel ratio AFR has a predetermined margin with respect to the air-fuel ratio upper limit value AFRUPR.
In other words, after the occurrence of the misfire state is detected in S12, it is determined whether or not the air-fuel ratio AFR has reached a predetermined air-fuel ratio lower limit value (= AFRUPR-AFm) lower than the air-fuel ratio upper limit value AFRUPR. Nothing else. In the present embodiment, the predetermined value AFm is fixed, but according to the present invention, the predetermined value AFm can be variably set according to the current combustion chamber temperature TCW. The lower limit of the air-fuel ratio corresponds to a second predetermined air-fuel ratio according to the present invention.

In S16, the upper limit value of the air-fuel ratio AFRUP
While it is determined that the difference between R and the air-fuel ratio AFR is equal to or less than the predetermined value AFm, the process proceeds to S17, and the combustion chamber temperature TC
Based on W, an idle speed correction amount Nup is set (see the table in FIG. 7). On the other hand, the air-fuel ratio upper limit value A
If it is determined that the difference between FRUPR and the air-fuel ratio AFR is larger than the predetermined value AFm, the process proceeds to S18, where the idling speed correction amount Nup is set to 0, and in S19, the flag FL is set.
After changing AG to 0, the routine returns.

Here, S3, 11, 12, 15, 16, and S19 constitute a misfire state detecting means according to the present invention.
S5, 8, 14, and 17 constitute the air-fuel ratio lowering means according to the present invention. Next, effects of the functions of the ECU 11 will be described. For easy understanding of the effects of the present embodiment, first, a case of a control apparatus for a diesel engine that does not employ the configuration according to the present invention will be described with reference to FIG. FIG. 8 schematically shows a result of a diesel engine start experiment in this case.

Generally, immediately after shifting from the start mode to the idle operation mode, the lubricating oil temperature of each sliding portion such as the piston and each bearing portion is low and the friction is large.
The fuel injection amount for maintaining the engine speed at the predetermined speed is set relatively large (A in the figure). Thereafter, as the temperature of the bearing portion and the like increases and the viscosity of the lubricating oil temperature decreases, the fuel injection amount required to maintain the predetermined rotation speed gradually decreases (B in the figure). As the fuel injection amount further decreases, the air-fuel ratio becomes larger (lean) than a value suitable for ignition. As a result, the combustion becomes slow, and in some cases, a misfire occurs, a high concentration of white smoke is emitted, and the fluctuation of the engine speed becomes large (C in the figure).

Thus, the effect of the present embodiment will be described with reference to FIG. FIG. 9 schematically shows a result of a start experiment of the engine 1 according to the present embodiment.
(A) combustion chamber temperature TCW, (b) air-fuel ratio AFR, (c)
Changes in the fuel injection amount Qm and (d) the engine speed Ne are shown with respect to time. When the air-fuel ratio AFR exceeds the air-fuel ratio upper limit value AFRUPR at time A, the ECU 11
The occurrence of a misfire state is detected (S12), and the basic target idle speed Nidleb is increased by the idle speed correction amount Nup (S8).

Then, feedback control for adjusting the actual engine rotational speed Ne to the corrected idle rotational speed Nidle functions, and the fuel injection amount Qm becomes larger than the original injection amount (when this control is not performed). As a result, the air-fuel ratio AFR decreases, so that the air-fuel ratio upper limit value AFRUPR
, It is possible to avoid the generation of white smoke, and to prevent the rotation fluctuation of the engine 1 due to misfire.

At time B, the air-fuel ratio AFR falls below the air-fuel ratio lower limit value (= AFRUPR-AFm).
It is determined that the possibility of misfire has been eliminated (S16), and the correction of the target idle speed is stopped (S18). Thereafter, the air-fuel ratio AFR slightly increases, and follows the value of the air-fuel ratio equilibrium state when this control is not performed. When the combustion chamber temperature TCW exceeds a predetermined temperature TCW1 (for warm-up determination) at time C (S5), it is determined that warm-up has been completed, and the present control is terminated (S7). This predetermined temperature TCW1 is set within a region where the air-fuel ratio AFR in the idle state reaches an equilibrium state.

Here, the idle rotation speed correction amount Nup is
As shown in FIG. 7, the air-fuel ratio AFR is set so as to decrease as the combustion chamber temperature TCW increases.
Until it reaches time B after it has dropped relatively
It rises while approaching the air-fuel ratio when this control is not performed. In the table of FIG. 7, as the reduction rate of the idle rotation speed correction amount Nup with respect to the combustion chamber temperature TCW increases,
The speed approaching the air-fuel ratio when this control is not performed increases. However, if this speed is too high, a situation occurs in which the air-fuel ratio upper limit value AFRUPR is exceeded again until time C, and the correction of the target idle speed and the stop thereof are repeated.

Conversely, the smaller the decrease rate is, the lower the speed is, and the longer the fuel injection amount increasing period. For this reason, although the control acts on the safe side, the fuel efficiency is deteriorated. Therefore, it is preferable that the above-mentioned reduction rate be set so that the air-fuel ratio AFR reaches the air-fuel ratio lower limit value (= AFRUPR-AFm) immediately before the warm-up is completed and the air-fuel ratio AFR reaches the equilibrium state.

Once the idle speed correction amount Nup is allocated in the table of FIG. 7, the air-fuel ratio AFR does not exceed the air-fuel ratio upper limit value AFRUPR again after detecting the occurrence of the misfire state. Equilibrium state (TC
W ≧ TCW1). For this reason, the processing of S5 (and the accompanying S7) can be omitted.

Next, a second embodiment of the present invention will be described. In the first embodiment described above, when the occurrence of a misfire state is detected during idling operation during warm-up, the air-fuel ratio AF
While the target idle speed is increased when R is decreased, the second embodiment is characterized in that the auxiliary equipment load is increased. FIG. 10 schematically shows a configuration of a control device of a diesel engine (hereinafter, referred to as “engine”) 101 according to the present embodiment. Note that the same components as those of the engine 1 according to the first embodiment are denoted by the same reference numerals.

The engine 101 has a common rail fuel injection system including a common rail 2, an injector 3, and a supply pump (not shown), as in the first embodiment. In the figure, reference numeral 31 is
The alternator is driven by a crankshaft of the engine 101. The generated power is supplied to the battery 32
Is charged. The amount of power generated by the alternator 31 is controlled by the amount of field current controlled by the field current regulator 33.

The ECU 11 receives various operation state detection signals from an engine speed sensor 22, an accelerator opening sensor 23, a water temperature sensor 24, and the like. ECU 11
Calculates the target fuel injection amount based on these detection signals, calculates the opening time of the solenoid valve of the injector 3 based on the calculated target fuel injection amount and the pressure in the common rail 2, As an operation command signal (fuel injection control signal). Further, the ECU 11 calculates and outputs a command signal to the field current regulator 33.

Next, the function of the ECU 11 will be described with reference to FIG.
This will be described with reference to the flowcharts shown in FIGS. S
At 21, the engine speed Ne detected by the engine speed sensor 22, the accelerator opening Acc detected by the accelerator opening sensor 23, and the water temperature (cooling water temperature) Tw detected by the water temperature sensor 24 are read.

In S22, the required fuel injection amount Qm is set based on the read various control information. In the operation state other than the idle state, the required fuel injection amount Qm is set mainly based on the accelerator opening Acc (using a known method for setting the fuel injection amount). On the other hand, in the idle state, a value automatically controlled to maintain the engine speed Ne at or near the target idle speed is set.

In step S23, referring to a map having a tendency similar to the tendency of the map shown in FIG.
11 enables automatic measurement. ) Estimate the combustion chamber temperature TCW based on the TIM. S23 constitutes the combustion chamber temperature estimating means according to the present invention. In S24, it is determined whether or not the combustion chamber temperature TCW is lower than a predetermined combustion chamber temperature TCW1 for determining a warm-up state. When the combustion chamber temperature TCW is lower than the predetermined temperature TCW1,
It is determined that the engine 101 is being warmed up, and the process proceeds to S25.
On the other hand, when the combustion chamber temperature TCW is equal to or higher than the predetermined temperature TCW1, it is determined that the warm-up of the engine 101 has been completed, and the control is stopped.

In S25, based on the combustion chamber temperature TCW, referring to a table having a tendency shown in FIG. 13, two limit values (injection amount lower limit value QLWR) relating to the fuel injection amount are set.
And a larger injection amount upper limit value QUAPR). This table is set so that these injection amount limit values QLWR and QUAR decrease as the combustion chamber temperature TCW increases. In the present embodiment, the difference between the injection amount upper limit QUAR and the injection amount lower limit QLWR is kept constant irrespective of the fuel chamber temperature TCW. Note that the injection amount lower limit QLWR corresponds to a first predetermined injection amount according to the present invention, and the injection amount upper limit QUAR corresponds to a second predetermined injection amount according to the present invention.

In S26, field current control is performed as described later with reference to FIG. This step is skipped after the warm-up is completed, so that the field current control is performed only during the warm-up. In S27, the field current amount IALT and the field current control flag FLAG are written in the memory.

Next, with reference to FIG.
(Field current control) will be described in detail. In S31, it is determined whether the required fuel injection amount Qm is smaller than the injection amount lower limit value QLWR. If the required fuel injection amount Qm is equal to or greater than the injection amount lower limit value QLWR, it is determined that the occurrence of a misfire state has not been detected, and the process proceeds to S32, where a field current control flag (whether the field current control is operating It is an index for identifying whether or not it is, and is initially set to 0.)
Is not 1, and the routine returns.
On the other hand, when the required fuel injection amount Qm is smaller than the injection amount lower limit value QLWR, it is determined that the occurrence of the misfire state is detected.
Proceed to S33.

In S33, the field current amount IALT is increased by a predetermined amount ICOR. This ICOR is the combustion chamber temperature T
Although it is easy to make it constant regardless of CW, it can be set so as to decrease as the combustion chamber temperature TCW rises, as in the case of the idle speed correction amount Nup described above.
In S34, the field current control flag FLAG is changed to 1.

By increasing the field current amount IALT in S33, the power generation amount of the alternator 31 increases and the load on the engine 101 increases. Therefore, the required fuel injection amount Qm for maintaining the engine speed Ne at the target idle speed is maintained.
Is increased. As the required fuel injection amount Qm is increased, the required fuel injection amount Qm is reduced in S31 to the injection amount lower limit value QL.
If it is determined that it is equal to or greater than WR, the process proceeds to S32.

At S32, the field current control flag FLAG
Is 1 or not. Field current control flag FL
If AG is 1, the process proceeds to S35. In S35,
It is determined whether or not the required fuel injection amount Qm is larger than the injection amount upper limit QUAR. The required fuel injection amount Qm is equal to the injection amount upper limit Q
If it is equal to or less than the UPR, the routine returns as it is to increase the field current amount IALT (= IA
LT + ICOR) and the field current control flag FLAG = 1
To maintain. On the other hand, if it is determined that the required fuel injection amount Qm is larger than the injection amount upper limit QUAR, the process proceeds to S36.

In S36, the field current amount IALT is reduced by a predetermined amount ICOR. Then, in S37, the field current control flag FLAG is changed to 0, and the field current control is stopped. By reducing the field current amount IALT in S36, the power generation amount of the alternator 31 is reduced, and the engine 101
, The required fuel injection amount Qm is reduced in order to maintain the engine speed Ne at the target idle speed.

Here, S25, 31, 32, 34, 35
And 37 constitute a misfire state detecting means according to the present invention,
S24, S33 and S36 constitute the air-fuel ratio lowering means according to the present invention. Next, effects of the functions of the ECU 11 will be described. FIG. 14 schematically shows the results of a start experiment of the engine 101 according to the present embodiment, in which (a) the combustion chamber temperature TCW, (b) the air-fuel ratio AFR,
(C) auxiliary equipment driving load, (d) fuel injection amount Qm and (e)
The change of the engine speed Ne is shown with respect to time.

When the required fuel injection amount Qm falls below the injection amount lower limit value QLWR at time A, occurrence of a misfire state is detected (S
31), accessory drive load (alternator power generation IALT)
Is increased by ICOR (S33). This allows
The required fuel injection amount Qm increases, and the air-fuel ratio AFR decreases as compared with the case where this control is not performed. Here, assuming that the operating state of the auxiliary machine does not change, the increase in the auxiliary machine driving load IC
Since OR is constant, the air-fuel ratio AFR increases while maintaining a substantially constant difference from the air-fuel ratio when this control is not performed.

When the required fuel injection amount Qm exceeds the injection amount upper limit value QUPR at time B, it is determined that the possibility of misfire has been eliminated (S35), and the increase of the auxiliary equipment load is stopped (S36). ). Thereafter, the required fuel injection amount Qm is controlled to adjust the engine speed Ne to the target idle speed. During this time, the ECU 11 repeats the determination in S31. However, if the combustion chamber temperature TCW exceeds the predetermined temperature TCW1 at time C, the ECU 11 determines that warm-up has been completed (S24) and stops this control.

As described above, according to the present invention,
When the occurrence of a misfire state is detected during the idling operation during warm-up, the air-fuel ratio AFR is made lower than the air-fuel ratio for feedback-controlling the engine speed Ne to the target idle speed. In the case where the engine is started, the ignitable air-fuel ratio can be maintained, so that misfire can be avoided, and emission of white smoke and fluctuation of engine rotation can be prevented.

According to the first embodiment, the occurrence of a misfire state can be accurately detected based on the air-fuel ratio AFR. According to the second embodiment, the occurrence of a misfire state can be detected by a simple control logic based on the required fuel injection amount Qm. This is because the control of the intake air amount such as the intake throttle, the exhaust throttle, the EGR, and the supercharging is generally not performed during the warm-up after the cold start. Therefore, by setting the lower limit (QLWR) of the required fuel injection amount Qm, the upper limit (AFRUPR) of the air-fuel ratio AFR is set.
Can be obtained, and it is possible to avoid a misfire without using an air-fuel ratio sensor (using the existing equipment for idle speed control as it is).

In the second embodiment, the engine 10
Alternator 31 as an auxiliary machine for controlling the load
I use. The present invention is not limited to this, and it is possible to employ auxiliary equipment other than the alternator 31 as long as the engine output can be stored as energy. Examples of such auxiliary machines include a compressor for an air conditioner, an oil pump for a power steering, and an oil pump for an automatic transmission. Also, in a so-called hybrid vehicle in which an internal combustion engine and an electric motor are combined, the electric motor can be used as a generator, so that the present invention can be applied.

In the above description, the combustion chamber temperature TCW
Is simply estimated based on the water temperature Tw and the elapsed time after starting TIM. The present invention is not limited to this, and may be calculated based on the engine compression ratio (preferably corrected by the intake air amount Qa) εr and the intake air temperature Tin. In this case, the calculated combustion chamber temperature TC
W may be corrected by the water temperature Tw.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing a configuration of a control device for a diesel engine according to a first embodiment of the present invention.

FIG. 2 is a flowchart showing control contents of the control device.

FIG. 3 is a flowchart of an idle speed correction amount setting routine;

FIG. 4 is a combustion chamber temperature estimation map.

FIG. 5 is an air-fuel ratio upper limit value setting table.

FIG. 6 is a basic target idle speed setting table.

FIG. 7 is an idle speed correction amount setting table;

FIG. 8 is a schematic diagram showing an engine operating state at the time of a low temperature start.

FIG. 9 is a time chart of a combustion chamber temperature, an air-fuel ratio, a fuel injection amount, and an engine speed according to the first embodiment of the present invention.

FIG. 10 is a diagram schematically showing a configuration of a control device for a diesel engine according to a second embodiment of the present invention.

FIG. 11 is a flowchart showing control contents of the control device.

FIG. 12 is a flowchart of a field current control routine.

FIG. 13 is a fuel injection amount limit value setting table.

FIG. 14 shows a combustion chamber temperature according to a second embodiment of the present invention,
Time chart of air-fuel ratio, auxiliary equipment load, fuel injection amount and engine speed

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Diesel engine 2 ... Common rail 3 ... Injector 4 ... Exhaust path 11 ... Electronic control unit 21 ... Air-fuel ratio sensor 22 ... Engine rotation speed sensor 23 ... Accelerator opening sensor 24 ... Water temperature sensor 31 ... Alternator 32 ... Battery 33 ... Field Current regulator

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) F02D 45/00 314 F02D 45/00 314B 314C 322 322C 368 368Z F-term (reference) 3G084 AA01 BA03 BA08 BA13 BA34 CA02 CA03 DA02 DA04 DA06 DA08 DA10 EB13 EB16 FA10 FA13 FA19 FA20 FA22 FA26 FA33 3G301 HA02 JA02 JA03 JA04 JA06 JA18 JA23 JA26 KA05 KA07 LB11 LC01 MA01 MA11 NC02 ND03 ND04 NE01 NE06 NE18 NE20 NE21 NE23 PB03Z PC05Z PC09Z PD02Z PE01A03

Claims (19)

[Claims] 1. A control apparatus for a diesel engine for feedback-controlling an engine speed to a target idle speed during idling operation, comprising: misfire state detecting means for detecting occurrence of a misfire state during idling operation during warm-up; A diesel fuel characterized by: air-fuel ratio lowering means for lowering the air-fuel ratio below the air-fuel ratio by the feedback control when the misfire state detecting means detects the occurrence of a misfire state during idling operation during warm-up. Engine control device. 2. The diesel engine control device according to claim 1, wherein said misfire state detecting means detects occurrence of said misfire state based on an air-fuel ratio. 3. The control of a diesel engine according to claim 2, wherein said misfire state detecting means detects the occurrence of said misfire state when said air-fuel ratio exceeds a first predetermined air-fuel ratio. apparatus. 4. The control device for a diesel engine according to claim 3, wherein said misfire state detecting means variably sets said first predetermined air-fuel ratio in accordance with a current combustion chamber temperature. . 5. The misfire state detecting means, after detecting the occurrence of the misfire state, continues until the air-fuel ratio reaches a second predetermined air-fuel ratio lower than the first predetermined air-fuel ratio. The control device for a diesel engine according to claim 3 or 4, wherein the occurrence is detected. 6. The control apparatus for a diesel engine according to claim 5, wherein said misfire state detecting means variably sets said second predetermined air-fuel ratio in accordance with a current combustion chamber temperature. . 7. The diesel engine control device according to claim 1, wherein said misfire state detecting means detects the occurrence of said misfire state based on a fuel injection amount. 8. The diesel engine according to claim 5, wherein said misfire state detection means detects the occurrence of said misfire state when the fuel injection amount falls below a first predetermined injection amount. Control device. 9. The diesel engine control device according to claim 8, wherein said misfire state detecting means variably sets said first predetermined injection amount in accordance with a current combustion chamber temperature. . 10. The misfire state detecting means, after detecting the occurrence of the misfire state, continues until the fuel injection amount reaches a second predetermined injection amount larger than the first predetermined injection amount. The control device for a diesel engine according to claim 8, wherein the generation of the engine is detected. 11. The control apparatus for a diesel engine according to claim 10, wherein said misfire state detecting means variably sets said second predetermined injection amount in accordance with a current combustion chamber temperature. . 12. The control apparatus for a diesel engine according to claim 1, wherein said air-fuel ratio lowering means lowers the air-fuel ratio in relation to a current combustion chamber temperature. . 13. The control device for a diesel engine according to claim 12, wherein said air-fuel ratio lowering means reduces the amount of said air-fuel ratio reduction in accordance with an increase in the temperature of a combustion chamber. 14. The diesel engine according to claim 1, wherein the air-fuel ratio lowering means increases the target idle speed by a predetermined speed when lowering the air-fuel ratio. Engine control device. 15. The control device for a diesel engine according to claim 14, wherein said air-fuel ratio lowering means sets said predetermined rotational speed based on a current combustion chamber temperature. 16. An auxiliary device driven by an engine drive shaft, wherein said air-fuel ratio lowering means increases a drive load of said auxiliary device by a predetermined load when lowering the air-fuel ratio. Item 12. The control device for a diesel engine according to any one of Items 1 to 11. 17. The diesel engine control device according to claim 16, wherein said air-fuel ratio lowering means sets said predetermined load amount based on a current combustion chamber temperature. 18. A diesel engine according to claim 1, wherein said misfire state detecting means determines whether or not the engine is being warmed up based on a temperature of a combustion chamber. Control device. 19. A combustion chamber temperature estimating means for estimating the combustion chamber temperature based on a cooling water temperature and an elapsed time after starting.
The control device for a diesel engine according to any one of 3, 15, 17, and 18.