JP3890460B2 - Automatic engine stop device - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to an automatic engine stop device that automatically and temporarily stops an engine according to a driving state of a vehicle.
[0002]
[Prior art]
For the purpose of improving fuel consumption and suppressing exhaust gas, an automatic engine stop device that automatically stops the engine when the vehicle is in a stop state such as waiting for a signal is known. JP-A-8-291725 discloses such an engine stop device. An engine automatic stop device is disclosed.
[0003]
[Problems to be solved by the invention]
By the way, it is also possible to combine a direct injection stratified gasoline engine with such an automatic engine stop device, and in this case, further improvement in fuel efficiency can be expected. There is a problem that a lot of vibrations occur.
[0004]
This is because, in an engine capable of stratified combustion, such as a direct injection stratified gasoline engine, the idle state after complete warm-up is often operated by stratified combustion. In the stratified combustion state, the intake air amount (= cylinder) This is due to the large amount of air.
[0005]
In other words, when the fuel injection and ignition are stopped, the engine is stopped due to the braking caused by the mechanical friction and reaction force accompanying pumping. However, if the amount of air charged in the cylinder is large in stratified combustion, the compression reaction caused by pumping is stopped. This is because the force increases, and so-called “shakeback” occurs without being able to resist the inertia.
[0006]
The present invention has been made in view of the above technical problem, and an object of the present invention is to eliminate the unpleasant vibration generated when the engine is automatically stopped when the engine automatic stop device and the direct injection stratified gasoline engine are combined.
[0007]
[Means for Solving the Problems]
According to a first aspect of the present invention, there is provided an engine capable of operating by switching between two combustion states of homogeneous combustion and stratified combustion, and target combustion state selecting means for selecting a target combustion state of the engine in accordance with the operating conditions; An engine automatic stop device comprising: a stop state determination unit that determines that the vehicle is in a stop state; and an idle stop unit that automatically stops the engine when it is determined that the vehicle is in a stop state. When it is determined that the vehicle is in a stopped state, stratified combustion prohibiting means for prohibiting stratified combustion of the engine before starting automatic engine stop and selecting homogeneous combustion, and intake air amount for detecting the intake air amount of the engine Detecting means, and after the idle stop means is prohibited from stratified combustion by the stratified combustion prohibiting means, the intake air amount is reduced to a value equivalent to that during homogeneous combustion. Is characterized in that stops the engine when.
[0010]
According to a third aspect of the present invention, there is provided an engine capable of operating by switching between two combustion states of homogeneous combustion and stratified combustion, and target combustion state selection means for selecting a target combustion state of the engine according to the operation conditions. An engine automatic stop device comprising: a stop state determination unit that determines that the vehicle is in a stop state; and an idle stop unit that automatically stops the engine when it is determined that the vehicle is in a stop state. When it is determined that the vehicle is stopped, the engine stratified combustion is prohibited before the engine is automatically stopped, and stratified combustion prohibiting means for selecting homogeneous combustion and the target equivalence ratio of the fuel mixture It includes the actual combustion state determining means for determining an actual combustion state, and the idle stop means, predetermined time after receiving the homogenous determination from said combustion state determining means It is characterized in that stopping the engine after a lapse.
[0011]
2nd and 4th invention is equipped with the actual combustion state determination means which determines the actual combustion state of the engine based on the target equivalence ratio of the fuel mixture in the 1st and 3rd inventions, and the vehicle is stopped. If it is determined that there is a homogeneity determination from the combustion state determination means before it is determined that a predetermined time has elapsed since the determination of the homogeneity determination, the idle stop means determines that the vehicle is in a stopped state. The engine is immediately stopped.
[0012]
[Action and effect]
According to the first and third inventions, when the engine is automatically stopped, the engine is stopped after the stratified combustion of the engine is prohibited and switched to the homogeneous combustion, and the intake air amount is reduced. As a result, the amount of air charged in the cylinder when the engine is stopped decreases, so that it is possible to suppress the occurrence of vibration due to the reaction force when compressing the air in the cylinder.
[0013]
Also, after forming layer prohibition command, the intake air amount considering the response delay until the reduction, to stop the engine and wait for the amount of intake air is reduced to a considerable time homogeneous combustion. As a result, the amount of air in the cylinder when the engine is stopped decreases, so that the occurrence of vibration due to the compression reaction force can be reliably suppressed. In particular, in the first invention, switching to homogeneous combustion can be determined more directly based on the intake air amount, and in the third invention, the actual combustion state of the engine is determined based on the target equivalence ratio. Therefore, it is possible to accurately determine the switch to homogeneous combustion even under a large amount of EGR.
[0014]
According to the second and fourth aspects of the invention, when the idling stop transition enabling condition is satisfied, the idling stop transition is performed when the homogenous combustion state has already been reached due to a request such as brake master back negative pressure or air-fuel ratio learning. As soon as possible conditions are met, the engine is stopped. Thereby, the time until the engine is stopped can be shortened, and the fuel consumption of the vehicle that automatically stops the engine can be further improved.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, reference examples of the present invention will be described with reference to the accompanying drawings.
[0016]
FIG. 1 is a schematic configuration diagram of a vehicle provided with an engine automatic stop device according to the present invention.
[0017]
The engine 1 is a so-called direct injection stratified gasoline engine that directly injects fuel into a cylinder and performs stratified combustion. The combustion state is stratified combustion (ultra lean combustion), homogeneous lean combustion, or stoichiometric combustion (theoretical air-fuel ratio combustion). It can be switched and operated. The output torque of the engine 1 is transmitted to the drive wheels 6 via the torque converter 3, the forward / reverse switching mechanism 4 and the belt type continuously variable transmission 5.
[0018]
A motor generator 2 capable of switching between driving and power generation is interposed between the engine 1 and the torque converter 3, and the motor generator 2 drives the vehicle by power running when starting or accelerating and decelerating. At times, regenerative operation is performed to charge a battery (not shown).
[0019]
The intake passage of the engine 1 is provided with an air flow meter 7 for measuring the intake air amount and an electronically controlled throttle 8 (hereinafter referred to as an electric throttle 8) that can be controlled independently of the driver's accelerator operation. Yes.
[0020]
In addition to the air flow meter 7, the controller 9 including a microprocessor or the like detects a crank angle sensor 10 that detects the engine speed and phase, a vehicle speed sensor 11 that detects the vehicle speed, and a brake pedal depression by the driver. Signals from the brake switch 12, the accelerator sensor 13 for detecting the accelerator operation amount, the idle switch 14 for detecting that the accelerator pedal is not depressed, the sensor 15 for detecting the master back negative pressure of the brake cylinder, and the like are also inputted. 9 judges the driving conditions of the vehicle based on these, and controls the engine 1, the motor generator 2, the continuously variable transmission 5 and the like in an integrated manner.
[0021]
In particular, when the combustion state of the engine 1 is switched, the controller 9 adjusts the intake air amount by adjusting the opening degree of the electric throttle 8 so that no step is generated in the output torque. For example, since air is required for stratified combustion than for homogeneous combustion, the opening degree of the electric throttle 8 is adjusted to the larger side when switching from homogeneous combustion to stratified combustion.
[0022]
Further, the controller 9 determines whether or not the vehicle is in a stopped state, and performs automatic stop and restart (idle stop control) of the engine 1 when it is determined that the vehicle is in a stopped state. Specifically, the controller 9 automatically stops the engine 1 by prohibiting stratified combustion and stopping fuel injection and ignition when a predetermined idle stop transition condition such as the vehicle speed being zero and the brake switch 12 being ON is satisfied. Let Then, when it is determined that the depression of the brake pedal is released thereafter, a motor generator control signal is output to drive the motor generator 2 to start cranking and restart fuel injection and ignition to restart the engine 1. .
[0023]
The contents of the idle stop control performed by the controller 9 will be described below with reference to the flowcharts shown in FIGS. Each flow is repeatedly executed by the controller 9 every predetermined time (for example, every 10 msec).
[0024]
First, the flowchart shown in FIG. 2 will be described. In this flowchart, it is determined whether an idle stop transition enabling condition is satisfied, and an idle stop transition flag #FISTPOK is set. Specifically, the following conditions (a) to (e) in steps S101 to S105 are as follows:
(a) The engine 1 has been warmed up (for example, the coolant temperature TW of the engine 1 is equal to or higher than a predetermined value)
(b) The brake pedal is depressed (brake switch 12 = ON)
(c) Vehicle speed VSP is zero
(d) The accelerator pedal is not depressed (idle switch 14 = ON)
(e) It is determined that the engine speed is the idling engine speed, and when all of these conditions are satisfied, the process proceeds to step S106, and the idling stop transition flag #FISTPOK indicates that the condition for allowing the idling stop transition is satisfied. Set. On the other hand, if any one of these conditions is not established, the process proceeds to step S107, and the idle stop transition flag #FISTPOK is set to zero, assuming that the idle stop transition enabling condition is not established.
[0025]
Therefore, by processing this flow, it is determined whether or not an idle stop transition enabling condition is satisfied. When the condition is satisfied, 1 is set to the idle stop transition flag #FISTPOK. However, even if 1 is set in this idle stop transition flag #FISTPOK, the engine is not stopped immediately, and the engine is stopped after an idle stop permission condition described later is satisfied.
[0026]
Next, the flowchart shown in FIG. 3 will be described. This is to select a target combustion state (stratified combustion, homogeneous lean combustion, or stoichiometric combustion) of the engine 1 in accordance with operating conditions and the like. Specifically, in steps S201 to S205, the following conditions (h) to (l),
(h) Idle stop transition enabling condition is not satisfied (# FISTPOK = 0 )
(i) The coolant temperature TW of the engine 1 is within a predetermined range (TWL ≦ TW ≦ TWH)
(j) The air-fuel ratio learning of engine 1 has converged
(k) The master back negative pressure of the brake cylinder is greater than the specified value
(l) It is determined that all devices such as EGR (exhaust gas recirculation device), swirl control valve, and VTC (variable valve timing device) are operating correctly, and if all of these conditions are met, the process proceeds to step S206 and subsequent steps. The target combustion state is selected according to the engine speed NRPM, the engine load TTC, and the vehicle speed VSP. On the other hand, if any of these conditions is not satisfied, the routine proceeds to step S225, where stoichiometric combustion is selected.
[0027]
The processing after step 206 will be described. In step S206 to step S211, a value is set in the flag #FMPCNE according to the read engine speed NRPM. Similarly, in steps S212 to S217 and steps S218 to S223, the engine load TTC and the vehicle speed VSP are read and values are set in the flags #FMPCTC and #FMPCVS, respectively.
[0028]
In step S224, the minimum values of the flags #FMPCNE, #FMPCTC, #FMPCVS are set in the flag #FMAPCH, and the combustion state of the engine 1 is selected. By performing the processing from step S206 to step S224, normally, stratified combustion (# FMAPCH = 2) is performed during low-load operation, homogeneous lean combustion (# FMAPCH = 1) is performed during medium-load operation, and homogeneous combustion (# FMAPCH = 1) during medium-high load operation. # FMAPCH = 0) is selected.
[0029]
In this way, the target combustion state of the engine 1 is selected in accordance with the operating conditions, etc., but in this flow, especially when the conditions for enabling the idle stop transition are satisfied (# FISTPOK = 1) Is selected as a target combustion state unconditionally without considering other conditions (stratified combustion prohibition command).
[0030]
Next, the flowchart shown in FIG. 4 will be described. In this flowchart, it is determined whether or not the idle stop permission condition is satisfied, and a value is set in the idle stop permission flag #FISPEX according to the determination result.
[0031]
First, in step S301, the value of the idle stop transition flag #FISTPOK is determined. If the value of flag #FISTPOK is 1, the process proceeds to step S302, and the value of the delay timer TMISHNH is set to the previous value TMISHNH (old) by a predetermined value TJOB #. It is updated to the value added with. The predetermined value TJOB # is the execution interval of this flow. On the other hand, if the value of the flag #FISTPOK is zero, the process proceeds to step S303, and the value of the delay timer TMISHNH is reset to zero.
[0032]
In step S304, it is determined whether the value of the delay timer TMISINH is equal to or greater than a predetermined value DISINH #. As a result, if the value of the delay timer TMISINH is equal to or greater than the predetermined value DISINH #, that is, if the predetermined time DISINH # or more has elapsed since the condition for enabling the idle stop transition has been satisfied, the process proceeds to step S305. The idle stop permission flag #FISPEX is set to 1 indicating that the idle stop permission condition is satisfied. When the idle stop permission flag #FISPEX is set to 1, the controller 9 stops the fuel supply and ignition to the engine 1 and stops the engine 1.
[0033]
On the other hand, when the value of the delay timer TMISHNH is smaller than the predetermined value DISINH #, the process proceeds to step S306, and the idle stop permission flag #FISPEX is set to zero indicating that the idle stop permission condition is not satisfied.
[0034]
Therefore, by processing this flow, when the idle stop transition enabling condition is satisfied, the controller 9 permits the idle stop after a predetermined time DISINH # has elapsed, and stops the engine 1. As described above, since the stratified charge combustion is prohibited when the idle stop transition permission condition is satisfied and the homogeneous combustion is selected as the target combustion state (step S201, step S225), as a result, the stratified charge combustion is prohibited and predetermined. The engine 1 is stopped after a lapse of time.
[0035]
Next, the effect | action by performing this idle stop control is demonstrated, referring the time chart shown in FIG.
[0036]
FIG. 5 shows the selected combustion state, throttle opening, intake air amount TP, idle stop transition flag #FISTPOK and idle stop permission flag #FISTPEX when the vehicle is stopped due to a signal or the like and idle stop is executed. It shows how the value changes.
[0037]
According to this, when the vehicle is stopped at time t1 and a predetermined idle stop transition permission condition is satisfied (# FISTPOK = 1), first, a stratified combustion prohibition command is issued to the engine 1, and the combustion targeted for homogeneous combustion is performed. Selected as a state.
[0038]
Along with this, the target throttle opening decreases instantaneously to an opening corresponding to homogeneous combustion, but the actual throttle opening does not decrease immediately but decreases with dead time and delay. Further, the intake air amount TP is delayed with respect to the change in the throttle opening, and responds with a first order delay with respect to the throttle opening area.
[0039]
In this way, even if homogeneous combustion is selected, there is a certain delay until the intake air amount TP becomes equivalent to that during homogeneous combustion.Therefore, the idle stop permission determination is made for a predetermined time DISINH # after the stratification prohibition command is issued. The time t2 when the intake air amount TP decreases and the combustion state is switched to the homogeneous combustion is issued. The predetermined time DISINH # is set in consideration of the response delay of the electric throttle 8 and the response delay of the intake air amount TP with respect to the throttle opening. Here, the time until the intake air amount TP decreases to a value equivalent to that at the time of homogeneous combustion. Set to Although depending on the responsiveness of the electric throttle 8, the predetermined time DISINH # is set to a value of about 1 second.
[0040]
The engine 1 is automatically stopped after a predetermined time DISINH # has elapsed after the idling stop is permitted. In this way, the engine 1 is not stopped in the stratified combustion state, and the intake air amount TP is in the homogeneous combustion. By preventing the engine 1 from being stopped before switching considerably, it is possible to suppress the engine from being stopped in a state where the amount of air charged in the cylinder is large and causing unpleasant vibration due to the compression reaction force of the air in the cylinder. .
[0041]
In this reference example, it is determined that the engine 1 has been switched to the homogeneous combustion based on the elapsed time since the homogeneous combustion was selected, but the determination that the engine 1 has been switched to the homogeneous combustion can also be determined by other methods. Hereinafter, first and second embodiments employing different determination methods will be described.
[0042]
First, FIG. 6 shows a first embodiment of the present invention. This flowchart is for determining whether the idle stop permission condition is satisfied or not, and is executed in place of the flow shown in FIG.
[0043]
According to this flow, as in the flow shown in FIG. 4, first, the value of the idle stop transition flag #FISTPOK is determined in step S401. If the value of flag #FISTPOK is 1, the process proceeds to step S402. Go to and set the idle stop permission flag #FISTPEX to zero.
[0044]
In step S404, it is determined whether or not the intake air amount TP measured by the air flow meter 7 is equal to or less than a predetermined value TPITP # corresponding to the theoretical air-fuel ratio. If the flag #FISTPEX is set to 1, otherwise, the process proceeds to step S404, and the idle stop permission flag #FISTPEX is set to zero.
[0045]
Therefore, by processing this flow, the controller 9 permits the idle stop when the intake air amount TP of the engine 1 decreases to a predetermined value TPITP # corresponding to the theoretical air-fuel ratio after the condition for enabling the idle stop transition is satisfied. It will be.
[0046]
FIG. 7 shows how the combustion state, throttle opening, intake air amount TP, idle stop transition flag #FISTPOK, and idle stop permission flag #FISTPEX change when the idle stop is executed.
[0047]
As shown in this figure, even when a stratified combustion prohibition command is issued to the engine 1 at time t1 and homogeneous combustion is selected, the actual throttle opening is delayed with respect to the change in the target throttle opening, and the intake air amount TP is The delay is further delayed with respect to the change in the throttle opening. Therefore, here, the change in the intake air amount TP after the stratification prohibition command is issued is monitored, and the idle stop is permitted at time t2 when the intake air amount TP becomes equal to or less than the predetermined value #TPISTP equivalent to the time of homogeneous combustion. (FISTPEX # = 1).
[0048]
By determining whether or not the engine has switched to the homogeneous combustion based on the intake air amount TP instead of the elapsed time since the idle stop transition permission condition is established, it is more directly determined that the engine has actually switched to the homogeneous combustion. The determination accuracy can be improved.
[0049]
Next, it will be described with the second embodiment of the present invention with reference to FIG.
[0050]
The flowchart shown in FIG. 8 determines whether or not the idle stop permission condition is satisfied, and is executed in place of the flow shown in FIG.
[0051]
In this flow, first, in step S501, it is determined whether or not the engine target equivalent ratio TFBYA is larger than a predetermined value TFACH # (stratification limit equivalent ratio). The stratified limit equivalent ratio is a limit value in which stratified combustion is selected if the equivalent ratio of the fuel mixture is smaller than this, and homogeneous combustion is selected if larger. If the result is larger than the predetermined value TFACH #, the process proceeds to step S502, where the delay timer TMHMCMB is updated to the previous value TMHMCMB (old) plus the job execution interval TJOB #, and is smaller than the predetermined value TFACH #. In this case, the process proceeds to step S503, and the delay timer TMHMCMB is reset to zero.
[0052]
In step S504, it is determined whether or not the delay timer TMHMCMB is larger than the predetermined value DHMCMB #. If larger than the predetermined value DHMCMB #, the process proceeds to step S505. Otherwise, the process proceeds to step S507 and the idle stop permission flag #FISTPEX. Set to zero.
[0053]
As described above, the target equivalent ratio TFBYA is set to wait for a predetermined time DHMCMB # after the target equivalent ratio TFBYA becomes the stratification limit equivalent ratio. When the target equivalent ratio TFBYA becomes the stratification limit equivalent ratio TFACH #, the intake air amount TP This is because it has not been sufficiently reduced, and it takes a predetermined time DHMCMB # until the intake air amount TP is reduced to a value equivalent to that during homogeneous combustion. The predetermined time DHMCMB # can be determined from the difference between the predetermined time DISINH # and the time until the predetermined equivalent value TFACH # reaches the predetermined value TFACH # after the target equivalent ratio TFBYA starts to change. Set to a value.
[0054]
In step S505, it is determined whether or not the idle stop transition flag #FISTPOK is 1. If the idle stop transition flag #FISTPOK is 1, the process proceeds to step S506 and 1 is set in the idle stop permission flag #FISTPEX. If the idle stop transition flag #FISTPOK is zero, the process proceeds to step S507, and the idle stop permission flag #FISTPEX is set to zero.
[0055]
Therefore, by processing this flow, the controller 9 performs an actual combustion state determination based on the target equivalent ratio TFBYA, and after the target equivalent ratio TFBYA has reached the stratified limit equivalent ratio, continues for a predetermined time or more DHMCMB #. Allow idle stop.
[0056]
Normally, after switching to homogenous combustion after the conditions for transition to idle stop have been established, idle stop is permitted after a predetermined time DHMCMB # has elapsed after the transition determination has been made, but before the conditions for transition to idle stop have been met. In other cases, for example, when a predetermined time DHMCMB # has elapsed since the homogenous combustion state has already occurred due to a request from the master back negative pressure of the brake cylinder or air-fuel ratio learning, the transition stop condition is satisfied and the idle stop is performed at the same time. Allowed.
[0057]
FIG. 9 shows how the combustion state, throttle opening, intake air amount TP, target equivalence ratio TFBYA, idle stop transition flag #FISTPOK, and idle stop permission flag #FISTPEX change when the idle stop is executed.
[0058]
As shown in this figure, when the vehicle is stopped at time t1 and a predetermined idle stop transition permission condition is satisfied, a stratified combustion prohibition command is first issued and homogeneous combustion is selected. When the target combustion state is switched, the “map value” of the target equivalence ratio is switched stepwise (not shown), but the intake air amount changes with a delay until the actual combustion state is switched. Since there is a delay, if the target equivalent ratio TFBYA used to determine the actual fuel injection amount is switched to a step, a torque step will occur. Therefore, here, the target equivalence ratio TFBYA is gradually changed in accordance with the phase of the intake air amount TP in order not to generate a torque step.
[0059]
The actual combustion state of stratification and homogeneity is determined based on this target equivalent ratio TFBYA, and stratified combustion is performed at time t2 after the lapse of a predetermined time DHMCMB # after the stratified limit equivalent ratio TFACH # is reached. Is determined to have been switched to and idling stop is permitted (# FISTPEX = 1).
[0060]
In this way, by determining the actual combustion state based on the target equivalent ratio TFBYA, the actual combustion state can be achieved even when there is little change in the engine load value based on the intake air amount TP (fresh air amount) due to a large amount of EGR. Can be determined.
[0061]
Direct injection strata gasoline engines often perform a large amount of EGR (exhaust gas recirculation) to reduce NOx, but if a large amount of EGR is being performed, the amount of intake air even when switched to a state of homogeneous combustion and no EGR Since TP does not change significantly, it may be difficult to determine the combustion state based on the intake air amount TP. However, by judging the actual combustion state based on the target equivalent ratio TFBYA reflecting the combustion state, it is not affected by EGR (exhaust gas recirculation), and even when a large amount of EGR is being performed, the actual combustion state It becomes possible to judge the state accurately.
[0062]
Also, before the conditions for enabling idle stop transition are established, transition is possible if the brake cylinder master back negative pressure or air-fuel ratio learning is in a homogeneous combustion state, and a predetermined time DHMCMB # has elapsed since then. As soon as the condition is satisfied, idle stop is permitted. Thereby, the time until the engine is stopped is shortened, and the fuel consumption of the vehicle that performs such an idle stop can be further improved.
[0063]
As mentioned above, although embodiment of this invention was described, the structure of the vehicle which can apply this invention is not limited to the structure shown in FIG. 1, A direct injection stratified engine is provided and an engine is stopped automatically. It can be widely applied to vehicles. The above-described embodiments are illustrative, and all modifications that belong to the scope of the invention described in the claims are included in the scope of the present invention.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a vehicle including an engine automatic stop device according to a reference example of the present invention.
FIG. 2 is a flowchart showing the content of a determination process for an idle stop transition enabling condition.
FIG. 3 is a flowchart showing the contents of engine combustion state selection processing.
FIG. 4 is a flowchart showing details of an idle stop permission condition determination process.
FIG. 5 is a time chart for explaining the operation of a reference example of the present invention.
FIG. 6 is a flowchart showing a first embodiment of the present invention.
FIG. 7 is a time chart for explaining the operation of the first embodiment.
FIG. 8 is a flowchart showing a second embodiment of the present invention.
FIG. 9 is a time chart for explaining the operation of the second embodiment.
[Explanation of symbols]
1 Engine 2 Motor generator 7 Air flow meter 8 Electric throttle 9 Controller 12 Brake switch 14 Idle switch

Claims (4)

An engine capable of operating by switching between two combustion states of homogeneous combustion and stratified combustion;
Target combustion state selection means for selecting a target combustion state of the engine according to operating conditions;
Stop state determination means for determining that the vehicle is in a stop state;
Idle stop means for automatically stopping the engine when it is determined that the vehicle is stopped;
In the engine automatic stop device equipped with
When it is determined that the vehicle is in a stopped state, stratified combustion prohibiting means for prohibiting stratified combustion of the engine before engine automatic stop and selecting homogeneous combustion ;
An intake air amount detection means for detecting the intake air amount of the engine,
The engine automatic stop device according to claim 1, wherein the idle stop means stops the engine when the stratified charge combustion is prohibited by the stratified charge combustion prohibiting means and then the intake air amount is reduced to a value equivalent to that during homogeneous combustion . An actual combustion state determining means for determining an actual combustion state of the engine based on a target equivalent ratio of the fuel mixture;
  If the vehicle has been subjected to a homogeneity determination from the combustion state determination means before it is determined that the vehicle is in a stopped state, and a predetermined time has elapsed since the homogeneity determination has been received, the idle stop means The engine automatic stop device according to claim 1, wherein the engine is stopped immediately when it is determined that the engine is in the state. An engine capable of operating by switching between two combustion states of homogeneous combustion and stratified combustion;
  Target combustion state selection means for selecting a target combustion state of the engine according to operating conditions;
  Stop state determination means for determining that the vehicle is in a stop state;
  Idle stop means for automatically stopping the engine when it is determined that the vehicle is stopped;
In the engine automatic stop device equipped with
  When it is determined that the vehicle is in a stopped state, stratified combustion prohibiting means for prohibiting stratified combustion of the engine before engine automatic stop and selecting homogeneous combustion;
  An actual combustion state determination means for determining an actual combustion state of the engine based on a target equivalent ratio of the fuel mixture,
  The engine automatic stop device according to claim 1, wherein the idle stop means stops the engine after a predetermined time has elapsed after receiving the homogeneity determination from the combustion state determination means. An actual combustion state determining means for determining an actual combustion state of the engine based on a target equivalent ratio of the fuel mixture;
  If the vehicle has been subjected to a homogeneity determination from the combustion state determination means before it is determined that the vehicle is in a stopped state, and a predetermined time has elapsed since the homogeneity determination has been received, the idle stop means The engine automatic stop device according to claim 3, wherein the engine is stopped immediately when it is determined that the engine is present.

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