JP5152134B2 - Automatic engine stop control device - Google Patents

Description

  The present invention relates to an engine automatic stop control device.

When the driver detects that the accelerator pedal has been released or the brake pedal has been pressed, the engine is automatically stopped based on that information, and the driver has released the brake or operated the accelerator when the engine has stopped. There is known an idle stop system that detects this and automatically starts the engine based on the information.
In such a system that automatically stops and starts the engine, if the engine is restarted frequently after an idle stop, the start shock at the time of restart becomes a problem, so the air / fuel ratio is leaner than the stoichiometric air / fuel ratio. To restart the engine.
However, when the engine is started at a lean air-fuel ratio, although the three-way catalyst is active, nitrogen oxides NOx may be discharged and the emission may be deteriorated. Therefore, in Patent Document 1, the air-fuel ratio is made rich immediately before the engine is automatically stopped, and the three-way catalyst is made rich to prepare for engine restart at a lean air-fuel ratio.

JP 2003-148201 A

  In the above-mentioned patent document, in order to control the air-fuel ratio richly before the engine is automatically stopped, a predetermined delay period is set after the engine automatic stop condition is satisfied, and the air-fuel ratio is controlled in a rich state during that period, and thereafter Need to stop the engine. However, in this case, even if the engine automatic stop condition is satisfied, there is a delay period until the engine is actually stopped. During this period, when the driver depresses the accelerator pedal and re-accelerates, The stop condition is canceled, and the rich control executed during the delay period may cause the catalyst to become excessively rich, leading to a reduction in exhaust purification performance and deterioration of emissions.

  The present invention has been made paying attention to such a problem, and in the case of controlling the air-fuel ratio richly before the engine is automatically stopped, the driver depresses the accelerator pedal and re-accelerates to automatically stop the condition. An object of the present invention is to provide an automatic engine stop control device that can suppress the deterioration of emissions even when the engine is canceled.

  The present invention solves the above problems by the following means. In addition, in order to make an understanding easy, although the code | symbol corresponding to embodiment of this invention is attached | subjected, it is not limited to this.

The present invention, automatic stop request determining unit determines the presence or absence of the automatic stop request engine (the step S3), and when it is determined that there is an automatic stop request of the engine by the automatic stop request determining unit, the air-fuel ratio A rich control unit before engine automatic stop (step S5) that performs rich control and an automatic engine stop request are issued by the automatic stop request determination unit, but a cancel request based on the driver's accelerator operation before the engine actually stops An erroneous increase counter determination unit (step S4) for determining whether or not an erroneous increase counter that counts up every time exceeds a reference value, and the rich control unit before engine automatic stop when the erroneous increase counter exceeds a reference value a prohibition or inhibit an automatic engine stop before rich control suppressing portion enrichment of the air-fuel ratio due to (step S6), and the automatic engine stop conditions are And determining stop condition determining unit whether the stand (step S7), and the automatic stop of the engine automatic stop conditions are automatically stopping the engine Once satisfied (step S8), and characterized by having a.

  According to the present invention, when the exhaust emission deteriorates due to the enrichment control of the air-fuel ratio before the engine is automatically stopped along with the cancel request for the engine automatic stop based on the driver's request, the rich before the engine is automatically stopped The purification performance is given priority by prohibiting or suppressing the gasification control, and it is possible to prevent the exhaust purification performance from being deteriorated and the emission from being deteriorated.

It is a schematic block diagram which shows one Embodiment of the automatic stop control apparatus of the engine by this invention. It is a flowchart which shows an example of the control logic of the automatic stop control apparatus of the engine by this invention. It is a timing chart explaining the operation | movement when a control logic is performed.

  Hereinafter, the best mode for carrying out the present invention will be described with reference to the drawings.

  The vehicle according to the present embodiment employs a hybrid system that uses a motor (not shown) as a driving force in addition to the engine 1.

  FIG. 1 is a schematic configuration diagram showing an engine automatic stop / start control device according to the present embodiment.

  The air taken into the engine 1 passes through the air cleaner 2, is measured for flow rate by the air flow meter 3, and is guided to the electric throttle valve 4. The electric throttle valve 4 controls the intake air amount. Thereafter, the intake air passes through the intake collector 5 and the intake manifold 6 and is introduced into the combustion chamber 8 via the intake valve 7.

  The combustion injection valve 9 injects fuel to the intake air in the combustion chamber 8 to form an air-fuel mixture, and the spark plug 10 ignites and burns this air-fuel mixture. Then, the combustion exhaust is discharged to the exhaust passage 12 through the exhaust valve 11. An exhaust purification catalyst 13 is provided in the exhaust passage 12.

  The exhaust purification catalyst 13 includes, for example, platinum (Pt) -rhodium (Rh) or palladium (Pd) -rhodium-based noble metal (catalyst component) and additives (co-catalyst) such as ceria (CeO2) and lanthanum (La). Is a three-way catalyst in which NO, which are harmful components in exhaust gas, are purified with high efficiency at a stoichiometric air-fuel ratio.

  An oxygen concentration sensor 14 for detecting the oxygen concentration in the exhaust gas is provided on the upstream side of the exhaust purification catalyst 13. When the engine 1 is operated at the stoichiometric air-fuel ratio, the oxygen concentration sensor 14 is used for fuel injection control. Air-fuel ratio feedback control based on the output signal is executed. The electric control throttle 4, the fuel injection valve 9 and the spark plug 10 are driven by the controller 20.

  The controller 20 includes an intake air amount Qm detected by the air flow meter 3 and an output signal of the oxygen concentration sensor 14, an accelerator opening APO detected by the accelerator pedal sensor 21, and an engine rotation detected by the crank angle sensor 22. Speed Ne, engine coolant temperature Tw detected by water temperature sensor 23, intake pressure Pa detected by intake pressure sensor 24, vehicle speed V detected by vehicle speed sensor 25, brake detected by brake sensor 26 (not shown) (ON / OFF), the shift lever position of the automatic transmission (not shown) detected by the shift lever position sensor 27, and the like are input.

  During normal operation, the controller 20 calculates the required torque of the engine 1 mainly based on the accelerator opening APO, and based on the required torque tTe, the engine rotational speed Ne, the engine coolant temperature Tw, and the like. A target equivalent ratio TFBYA is calculated. This target equivalent ratio TFBYA is the reciprocal of the excess air ratio λ, and is 1.0 for the theoretical air-fuel ratio, a value smaller than 1 for the lean air-fuel ratio, and a value larger than 1 for the rich air-fuel ratio. Then, the electric throttle valve 4 is driven so as to obtain an air amount necessary for realizing the target equivalent ratio TFBYA.

  Further, the basic fuel injection amount Tp = K × Qm / Ne (K; constant) is calculated from the intake air amount Qm and the engine rotational speed Ne, and this is multiplied by the target equivalent ratio TFBYA to obtain the final fuel injection. The amount Ti = Tp × TFBYA × COEF (COEF; various correction coefficients) is calculated. The fuel injection valve 9 is driven by outputting a fuel injection pulse signal having a pulse width corresponding to the final fuel injection amount Ti. The ignition timing by the spark plug 10 is controlled based on the engine speed Ne, the required torque tTe, and the like.

  Further, the controller 20 automatically stops the engine 1 when a predetermined engine automatic stop condition is satisfied, and the predetermined engine automatic start condition is satisfied, for example, the driver depresses the accelerator pedal after the engine is stopped once. In this case, a so-called idle stop (automatic stop / automatic start) control is executed in which the starter 15 is automatically driven to restart the engine 1.

  Since the present embodiment is applied to a hybrid system, it detects that the driver has released the accelerator even when the vehicle is running, and actively stops the engine automatically. For this reason, automatic stop / automatic start is frequently performed as compared with a system in which an ordinary vehicle is in an idle state and performs an idle stop.

  As described above, in the conventional method, in order to control the air-fuel ratio richly before the engine is automatically stopped, a predetermined delay period is set after the engine automatic stop condition is satisfied, and the air-fuel ratio is controlled in a rich state during that period. Then, it is necessary to stop the engine.

  However, in this case, even if the engine automatic stop condition is satisfied, there is a delay period until the engine is actually stopped. During this period, when the driver depresses the accelerator pedal and re-accelerates, It has been found by the present inventors that the stop condition is canceled and the rich control executed during the delay period results in an excessive catalyst rich state, resulting in a deterioration in exhaust gas purification performance and emission.

  In particular, in the hybrid system, the engine is automatically stopped while the vehicle is running. Therefore, when the driver frequently accelerates and re-accelerates, it is easy to enter the automatic stop condition. Conditions are easy to cancel. As a result, the air-fuel ratio rich control before the automatic stop is performed without the lean control at the automatic start, and the emission is deteriorated at the time of reacceleration.

  Therefore, in the present embodiment, by determining whether or not the driver's accelerator operation easily enters such a condition, the driver depresses the accelerator pedal after the engine automatic stop condition is satisfied and before the engine is actually stopped. In many cases, the air-fuel ratio rich control before the automatic engine stop and the air-fuel ratio lean control during the automatic engine start are prohibited or suppressed.

  Therefore, specific control contents will be described below.

  FIG. 2 is a flowchart showing an example of the control logic of the engine automatic stop control device according to the present invention. As described above, the accelerator pedal after the engine automatic stop condition is established and before the engine is actually stopped. When the count value exceeds a predetermined value, the air-fuel ratio rich control before the engine is automatically stopped and the air-fuel ratio lean control when the engine is automatically started are prohibited or suppressed.

  The controller 20 repeatedly executes this process in a cycle of several milliseconds.

  In step S1, the controller 20 determines whether or not the engine is automatically stopped. If the engine is automatically stopped, the controller 20 proceeds to step S11, and if not, the controller 20 proceeds to step S2.

  In step S <b> 2, the controller 20 determines whether or not a cancel request has been made before the engine is automatically stopped. If there is a cancel request, the controller 20 proceeds to step S10, and if there is no cancel request, the controller 20 proceeds to step S3. The cancel request is, for example, an acceleration request due to depression of an accelerator pedal.

  In step S3, the controller 20 determines whether or not there is an engine automatic stop request. If there is a request, the controller 20 proceeds to step S4, and if there is no request, the controller 20 exits the process. The engine automatic stop request is, for example, that the accelerator pedal is released.

  In step S4, the controller 20 determines whether or not the erroneous increase counter is smaller than the reference value. If the controller 20 is small, the process proceeds to step S5. If the controller 20 is large, the process proceeds to step S6.

  In step S5, the controller 20 executes a fuel injection increase process before the automatic stop.

  In step S6, the controller 20 performs processing while suppressing an increase in fuel injection before the automatic stop. It should be noted that the suppressed increase amount should be smaller than the increase amount in step S5, and is set to zero in FIG. Further, the rich value itself may be prohibited instead of setting the increase value to zero.

  In step S7, the controller 20 determines whether or not an engine automatic stop condition is satisfied. The process exits until it is established, and when it is established, the process proceeds to step S8.

  In step S8, the controller 20 automatically stops the engine.

  In step S9, the controller 20 decrements the erroneous increase counter by 1 from the previous value.

  In step S10, the controller 20 adds 5 to the previous value of the erroneous increase counter.

  In step S11, the controller 20 determines whether or not an engine automatic start condition is satisfied. The controller 20 exits the process until it is satisfied, and when it is satisfied, shifts the process to step S12.

  In step S12, the controller 20 finishes the automatic engine stop and automatically starts the engine.

  FIG. 3 is a timing chart for explaining the operation when the control logic is executed.

  The above control logic is executed and operates as follows.

  Initially, the engine is running. Until there is an automatic engine stop request, the controller 20 repeatedly executes steps S1 → S2 → S3.

  If there is an engine automatic stop request at time t1, the controller 20 advances the process from step S3 to S4. At time t1, since the erroneous increase counter is smaller than the reference value, the controller 20 advances the process from step S4 → S5 → S7 to execute the fuel injection increase process before the automatic stop (FIG. 3 (C)). If the accelerator pedal is depressed before the engine automatically stops, the next cycle is processed in steps S1 → S2 → S10, and as shown in FIG. 3 (B), the erroneous increase counter is incremented by 5 from the previous value. The

  When there is an engine automatic stop request again at time t2, the controller 20 advances the process from step S3 to S4. At time t2, since the erroneous increase counter is smaller than the reference value, the controller 20 advances the process from step S4 → S5 → S7 to execute the fuel injection increase process before the automatic stop (FIG. 3 (C)). If the accelerator pedal is depressed before the engine automatically stops, the next cycle is processed in steps S1 → S2 → S10, and as shown in FIG. 3 (B), the erroneous increase counter is incremented by 5 with respect to the previous value. The

  When the automatic engine stop condition is satisfied at time t3, the controller 20 advances the process from step S7 → S8 → S9 to stop the engine (FIG. 3A), and the erroneous increase counter is 1 minus the previous value. (FIG. 3B).

  Until time t4, the engine is stopped and the engine automatic start condition is not satisfied. At this time, the controller 20 advances the process from step S1 to S11.

  When the engine automatic start condition is satisfied at time t4, the controller 20 advances the process from step S11 to step S12 and restarts the engine (FIG. 3A).

  Until the time t5, since the engine is operating and there is no request for automatic engine stop, the controller 20 repeatedly executes steps S1-> S2-> S3.

  If there is an automatic engine stop request at time t5, the controller 20 advances the process from step S3 to S4. At time t5, since the erroneous increase counter is smaller than the reference value, the controller 20 advances the process from step S4 to S5, and executes the fuel injection increase process before the automatic stop (FIG. 3C). When the automatic engine stop condition is satisfied, the engine is stopped (step S8; FIG. 3A), and the erroneous increase counter is decremented by 1 from the previous value (step S9; FIG. 3B).

  Until time t6, the engine is stopped and the engine automatic start condition is not satisfied. At this time, the controller 20 advances the process from step S1 to S11.

  When the engine automatic start condition is satisfied at time t6, the controller 20 advances the process from step S11 to step S12 and automatically starts the engine (FIG. 3A).

  When there is an engine automatic stop request at time t7, the controller 20 advances the process from step S3 to S4. At this time, since the erroneous increase counter is smaller than the reference value, the controller 20 advances the process in steps S4 → S5 → S7 and executes the increase process of fuel injection before the automatic stop (FIG. 3C).

  At time t8, since the erroneous increase counter exceeds the reference value, the increase in fuel injection before the automatic stop is suppressed (step S6), that is, in this embodiment, the engine is stopped without increasing the fuel (step S8). FIG. 3 (A)), the erroneous increase counter decrements 1 from the previous value (step S9; FIG. 3 (B)).

  When the engine automatic start condition is satisfied at time t9, the controller 20 advances the process from step S11 to step S12 and restarts the engine (FIG. 3A).

  Since the erroneous increase counter exceeds the reference value at time t10, the increase in fuel injection before the automatic stop is suppressed (step S6), that is, in this embodiment, the engine is stopped without increasing the fuel (step S8). FIG. 3 (A)), the erroneous increase counter decrements 1 from the previous value (step S9; FIG. 3 (B)).

  When the engine automatic start condition is satisfied at time t11, the controller 20 advances the process from step S11 to step S12 and restarts the engine (FIG. 3A).

  Since the erroneous increase counter exceeds the reference value at time t12, the increase in fuel injection before the automatic stop is suppressed (step S6), that is, in this embodiment, the engine is stopped without increasing the fuel (step S8). FIG. 3 (A)), the erroneous increase counter decrements 1 from the previous value (step S9; FIG. 3 (B)).

  In order to reduce the shock at the time of automatic engine start and prevent deterioration of exhaust emission, the engine is stopped after controlling the air-fuel ratio to the catalyst richly just before the automatic engine stop. A method of restarting at an air-fuel ratio leaner than the air-fuel ratio has been known. As described above, in order to actually control the air-fuel ratio to be rich before the engine is automatically stopped, a predetermined delay period is set after the engine automatic stop condition is satisfied, during which the air-fuel ratio is controlled in a rich state, and thereafter Need to stop the engine.

  However, even if the engine automatic stop condition is satisfied, there is a delay period until the engine is actually stopped.Therefore, when the driver depresses the accelerator pedal and accelerates again during this period, the engine automatic stop condition is It has been found by the present inventors that the rich state of the catalyst becomes excessive due to the rich control executed during the delay period, the exhaust purification performance is lowered, and the emission is deteriorated.

  Therefore, when the automatic stop condition is often canceled after the engine automatic stop condition is satisfied and the driver often depresses the accelerator pedal before the engine actually stops, this state is detected. The air-fuel ratio rich control before the engine is automatically stopped and the air-fuel ratio lean control when the engine is automatically started are prohibited or suppressed.

  In this way, if exhaust emissions worsen due to shock countermeasures at the time of automatic engine start, the shock countermeasures at the time of automatic engine start (rich control immediately before engine automatic stop) can be prohibited or suppressed. The purification performance is given priority, and it is possible to prevent the exhaust purification performance from deteriorating and the emission from deteriorating.

  Without being limited to the embodiments described above, various modifications and changes are possible within the scope of the technical idea, and it is obvious that these are also included in the technical scope of the present invention.

  For example, in the present embodiment, the case where the fuel injection increase before the automatic stop is set to zero in step S6 has been described as an example, but it may be suppressed to be smaller than the increase in step S5.

  Further, in the present embodiment, the erroneous increase counter is decremented when the engine is automatically stopped normally after the rich control is performed. However, this may not be performed, and the automatic stop is canceled with a minus value. Similarly to the case value (the value on the plus side), it may be -5.

  Further, in the present embodiment, the air-fuel ratio rich control before the next automatic engine stop is suppressed or prohibited only after the erroneous increase counter exceeds the reference value. The subsequent enrichment control may be prohibited when the cancel condition is satisfied.

  This embodiment can be applied not only to an engine of a hybrid vehicle that uses a motor in combination with an engine for driving the vehicle, but also to a normal engine vehicle engine that uses only an engine.

1 Engine 9 Combustion Injection Valve 13 Exhaust Purification Catalyst 20 Controller Step S3 Automatic Stop Request Determination Unit Step S5 Rich Control Unit Before Engine Automatic Stop Step S6 Rich Control Suppression Unit Before Engine Automatic Stop

Claims (2)

An automatic stop request determination unit for determining whether or not there is an automatic engine stop request;
A rich control unit before automatic engine stop for controlling the air-fuel ratio to be rich when it is determined by the automatic stop request determination unit that there is an automatic engine stop request;
Whether or not the automatic stop request determination unit has made an automatic engine stop request, but the erroneous increase counter that counts up every time there is a cancel request based on the driver's accelerator operation before the engine actually stops exceeds a reference value. An erroneous increase counter determination unit for determining whether or not
A rich control suppression unit before engine automatic stop that inhibits or suppresses enrichment of the air-fuel ratio by the rich control unit before engine automatic stop when the erroneous increase counter exceeds a reference value ;
A stop condition determination unit that determines whether or not an engine automatic stop condition is satisfied;
An automatic stop unit that automatically stops the engine when the engine automatic stop condition is satisfied;
An engine automatic stop control device comprising: In the engine automatic stop control device according to claim 1 ,
A subtracting unit that subtracts the erroneous increase counter when the automatic stop request determining unit determines an engine automatic stop request and then stops the engine without a cancel request based on the driver's accelerator operation;
An engine automatic stop control device characterized by that.

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