JP2006194143A - Control device for engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control device for an engine capable of preventing misfiring due to rapid rising of an in-cylinder EGR ratio in the engine constituted such that fuel feeding is stopped at a predetermined timing after deceleration requirement of the vehicle is detected. <P>SOLUTION: The engine control unit presumes the in-cylinder EGR ratio E based on the number of revolution N of the engine, a suction pressure Ap, opening θe of the EGR valve and when the deceleration requirement is detected, it stops reflux of an exhaust gas. Further, it maintains opening θs of a throttle valve to the opening at the time when the deceleration requirement is detected during when the in-cylinder EGR ratio exceeds a predetermined value Eo. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an engine control device configured to stop fuel supply at a predetermined time after a deceleration request is detected, and belongs to the technical field of engine control.

  In a vehicle, for example, when a deceleration request is detected for the purpose of improving fuel efficiency (for example, when the accelerator opening is zero when the vehicle speed and the engine speed are each equal to or greater than a predetermined value), the fuel to the engine A so-called fuel cut control to stop the supply may be performed, but if the fuel cut is executed immediately when the deceleration request is detected, a shock may occur due to torque fluctuation, and this can be mitigated as a technology For example, Patent Document 1 discloses a technique that delays execution of fuel cut for a predetermined time.

JP-A-56-050232

  By the way, an engine may be provided with an EGR passage that recirculates exhaust gas from an exhaust passage to an intake passage downstream of the throttle valve, and an EGR valve that opens and closes the passage in the middle of the EGR passage. However, in such a case, when the technique described in Patent Document 1 is applied, the following problems may occur.

  That is, when the deceleration request is detected, the throttle valve is normally fully closed and the EGR valve is simultaneously closed. In this case, supply of new intake air to the downstream side of the throttle valve is promptly performed. Although the EGR valve is provided in the middle of the EGR passage, the exhaust gas remaining on the intake passage side from the EGR valve in the EGR passage even when the EGR valve is closed. The gas continues to be supplied into the cylinder for a while, and as a result, the in-cylinder EGR rate (the amount of recirculated exhaust gas / (the amount of recirculated exhaust gas + the amount of fresh air)) suddenly increases, and a misfire occurs before the predetermined time has elapsed. There is a risk of inviting and shocking.

  Therefore, the present invention provides an engine control device capable of preventing misfire due to a sudden rise in the in-cylinder EGR rate in an engine configured to stop fuel supply at a predetermined time after a deceleration request is made. The task is to do.

  In order to solve the above-described problems, the present invention is configured as follows.

  First, the invention according to claim 1 of the present application stops the fuel supply to the engine at a predetermined time after the deceleration request detecting means for detecting the deceleration request and the deceleration request detecting means detects the deceleration request. An engine control device comprising a fuel supply stop means, an electric intake throttle valve, throttle valve control means for controlling the throttle valve, and exhaust gas from an exhaust passage to an intake passage downstream of the throttle valve EGR means for recirculating gas; operating state detecting means for detecting the operating state of the engine; and EGR rate estimating means for estimating an in-cylinder EGR rate based on the operating state of the engine detected by the operating state detecting means; When the deceleration request detection means detects the deceleration request, the EGR means stops exhaust gas recirculation, and the throttle valve The control unit maintains the throttle valve opening at the opening when the deceleration request is detected while the in-cylinder EGR rate estimated by the EGR rate estimating unit exceeds a predetermined value. It is characterized by.

  According to a second aspect of the present invention, in the first aspect of the present invention, gear stage detecting means for detecting a gear position of the transmission is provided, and the throttle valve control means is configured to estimate the EGR rate. When the in-cylinder EGR rate estimated by the means is equal to or lower than a predetermined value and the electric intake throttle valve is closed, the speed of the closing operation is increased as the gear position is higher. .

  According to a third aspect of the present invention, in the second aspect of the present invention, when the fuel supply to the engine is stopped by the fuel supply stop means after the electric intake throttle valve is closed. Torque difference calculation means for calculating an engine torque difference before and after the fuel supply stop is provided, and the fuel supply stop means is configured so that the engine torque difference calculated by the torque difference calculation means is less than or equal to a predetermined torque difference. The fuel supply is stopped.

  Further, the invention according to claim 4 is the invention according to claim 3, wherein the predetermined torque difference is set to a smaller value as the shift speed detected by the shift speed detection means is closer to the lower speed. It is characterized by that.

  Next, the effect of the present invention will be described.

  First, according to the first aspect of the invention, when the deceleration request is detected, the electric intake throttle valve is not immediately closed, but the in-cylinder EGR rate exceeds a predetermined value. Since the opening is maintained at the time when the deceleration request is detected, fresh air continues to be supplied into the cylinder. As a result, even if the exhaust gas remaining in the EGR passage continues to be supplied in the cylinder after a deceleration request, the in-cylinder EGR rate does not rise rapidly, and the occurrence of misfire is reliably prevented. .

  By the way, when the in-cylinder EGR rate estimated by the EGR rate estimating means becomes equal to or less than a predetermined value, the electric intake throttle valve is closed, but if the closing operation speed is not properly controlled, During operation, a drive system such as an engine may resonate, and the vibration is transmitted to the vehicle body, which may cause a tip-out shock (for example, vibration in the vehicle longitudinal direction). In particular, the closer the gear position is to the higher speed side, the lower the moment of inertia of the drive system, and the higher the resonance frequency of the drive system (the shorter the resonance cycle). Even if the closing operation is performed, vibration due to resonance is likely to occur during the closing operation, and as a result, the tip-out shock is more likely to occur.

  However, according to the second aspect of the invention, the closer the gear stage is to the high speed stage, the faster the closing operation speed of the electric intake throttle valve is, that is, the resonance is less likely to occur on the high speed stage side. Since the closing operation speed is controlled, the tip-out shock is effectively prevented at any shift speed.

  Here, when the fuel supply is stopped, the engine torque will be lower than before the stop, but if the torque difference at that time is large, there is a risk that a shock will occur in the vehicle body.

  However, according to the third aspect of the present invention, the fuel supply is stopped when the difference in engine torque before and after the stop of the fuel supply that occurs when the fuel supply to the engine is stopped becomes equal to or less than the predetermined torque difference. Therefore, the shock that occurs in the vehicle body due to the stop of the fuel supply is prevented.

  Note that the shock accompanying the stop of fuel supply is more likely to occur due to the torque difference being amplified by the transmission on the low speed side even when the engine torque difference is the same.

  However, according to the fourth aspect of the present invention, the predetermined torque difference is set to a smaller value as the shift speed detected by the shift speed detection means is closer to the lower speed, so at any shift speed. Even in some cases, it is possible to reliably prevent a shock caused by stopping the fuel supply.

  Hereinafter, the best mode for carrying out the present invention will be described.

  FIG. 1 shows an overall configuration of an engine 1 according to an embodiment of the present invention. The engine 1 is a multi-cylinder engine in which a plurality of cylinders (only one is shown) are arranged in series. A piston 4 connected to the crankshaft 2 by a connecting rod 3 defines a combustion chamber 5 in each cylinder. An ignition plug 6 is disposed above each combustion chamber 5, and intake and exhaust ports that are opened and closed by an intake valve 7 and an exhaust valve 8 are opened. The intake port continues to the intake passage 10, and the exhaust port continues to the exhaust passage 20.

  In the intake passage 10, an air cleaner 11, an intake air temperature sensor 12, an air flow meter 13, an intake throttle valve 14, and an intake pressure sensor 15 are disposed in order from the upstream side, and an injector 16... 16 ( Only one cylinder is shown). The intake throttle valve 14 is an electric type and can operate independently of the accelerator pedal operation.

  An EGR passage 30 is disposed between a relatively upstream portion of the exhaust passage 20 and a relatively downstream portion of the intake passage 10, and an EGR valve 31 that adjusts an exhaust gas recirculation amount on the passage 30, and the EGR valve An EGR valve opening sensor 32 for detecting the opening of 31 is provided.

  An engine speed sensor 41 is provided in the vicinity of the crankshaft 2, and a water temperature sensor 42 is provided in the cylinder block. An accelerator opening sensor 43 that detects the amount of depression of the accelerator pedal (accelerator opening) is provided in the passenger compartment, and a vehicle speed sensor 44 is provided in the vicinity of the axle.

  The control unit (ECU) 50 of the engine 1 is based on the intake air temperature, intake air amount, intake air pressure, engine speed, cooling water temperature, engine load (accelerator opening), vehicle speed, etc. detected by the sensors. The fuel injection amount and injection timing control (fuel injection control) by the injector 16 and the ignition timing by the spark plug 6 are calculated, and the corresponding control signals are output to the injector 16 and the spark plug 6.

  Further, the ECU 50 calculates the opening degree θs of the intake throttle valve 14 and the opening degree θe of the EGR valve 31 based on the signals and the gear stage signal from the gear stage detection means 45, and controls corresponding thereto. A signal is output to the throttle valve 14 and the EGR valve 31. Note that the gear position detection means 45 is, for example, a transmission control unit, and a gear position signal from the unit may be input.

  Next, the control by the ECU 50 will be described in detail using the flowchart shown in FIG.

  First, in step S1, the engine speed N, the vehicle speed S, the accelerator opening degree θa, the intake pressure Ap, the shift stage Sp, and the EGR valve opening degree θe detected by the various sensors are input.

  Next, at step S2, the presence or absence of a deceleration request is determined based on the engine speed N, the vehicle speed S, and the accelerator opening degree θa. Here, the conditions for determining that there is a deceleration request (YES) are that the engine speed N is equal to or higher than the predetermined speed, the vehicle speed S is equal to or higher than the predetermined vehicle speed, and the accelerator opening θa is zero (accelerator 3) that the pedal is not depressed). Otherwise, it is determined that there is no deceleration request (NO).

  Then, when there is no deceleration request (NO), the process returns as it is, and when there is a deceleration request (YES), the processing after step S3 is performed. That is, in step S3, full-closed control of the EGR valve 31 is executed, and in step S4, until the engine flows into the cylinder based on the engine speed N, the intake pressure Ap, and the opening degree θe of the EGR valve 31. An in-cylinder EGR rate E (recirculation exhaust gas amount / (recirculation exhaust gas amount + new air amount)) that takes into account the response delay is calculated.

  Next, in step S5, it is determined whether or not the in-cylinder EGR rate E calculated in step S4 is equal to or less than a predetermined value Eo. Here, the predetermined value Eo is set to a value smaller than the maximum value of the in-cylinder EGR rate that does not cause misfire. If it is not less than the predetermined value Eo in this determination (NO), the throttle opening θs is maintained at the opening before the deceleration request is generated in step S11, and the process returns. On the other hand, when the value is equal to or less than the predetermined value Eo (YES), the valve closing speed of the throttle valve 14 is set by applying the rotation speed N and the gear stage Sp to the map shown in FIG. Here, as shown in FIG. 3, this valve closing speed is set to be faster as the engine speed N is lower and as the gear stage Sp is on the higher gear side (three lines in FIG. 3). Is displayed in order to show the tendency of the valve closing speed obtained from this map, and values corresponding to the rotational speed N and the gear stage Sp exist in portions other than these lines). This is because, as the engine speed N is smaller, the moving speed of the intake air in the intake passage 10 is slower. Therefore, even if the throttle valve 14 is fully closed, the intake air existing on the downstream side of the throttle valve 14 for a while after that. This is because, in order to realize fuel cut at the earliest possible time, it is necessary to close the valve faster as the engine speed N is smaller. Further, the closer the gear stage Sp is to the high speed stage side, the smaller the moment of inertia of the drive system composed of the engine 1, the transmission, etc., and the higher the resonance frequency of the drive system (the shorter the resonance period). Therefore, even if the closing operation is performed at the same speed, vibration due to resonance occurs in the drive system during the closing operation of the throttle valve 14 and is transmitted to the vehicle body. As a result, a tip-out shock (for example, vibration in the vehicle longitudinal direction) is generated. It tends to occur. Therefore, in order to avoid this tip-out shock, the valve closing speed is set faster as the gear stage Sp is on the higher gear stage side.

  Next, in step S7, the throttle valve 14 is fully closed at the valve closing speed obtained in step S6, and in step S8, fuel supply is stopped based on the engine speed N and the gear stage Sp (fuel cut). To calculate the torque difference Td of the engine torque T generated before and after that. Specifically, when the throttle valve 14 is closed as described above, the engine speed N starts to decrease. The deceleration of the engine speed N at this time is represented by the change in the detected engine speed N. 4 is applied to the map shown in FIG. 4 to obtain the torque difference Td (the three lines in FIG. 4 indicate the tendency of the torque difference Td obtained from this map). The values corresponding to the deceleration and the speed Sp are also present in portions other than these lines). Here, the engine torque difference Td tends to increase as the deceleration of the engine speed N increases, and the higher the gear stage Sp, the higher the speed stage, the higher the speed of the drive system including the engine 1 and the transmission. As the moment of inertia becomes smaller, it tends to increase. Therefore, the map shown in FIG. 4 takes this tendency into consideration.

  Next, in step S9, it is determined whether or not the engine torque difference Td calculated in step S8 is equal to or smaller than the allowable torque difference Tdo. Here, even if the engine torque difference Td is the same, due to the gear ratio, the torque variation of the transmission output decreases as the gear position Sp is closer to the high speed gear side, and the shock generated in the vehicle body becomes smaller. Therefore, as shown in FIG. 5, the allowable torque difference Tdo is set to a larger value as the shift speed Sp is closer to the higher speed. When the determination is not equal to or less than the allowable torque difference Tdo (NO), the process returns to step S8, the latest engine speed N and the gear stage Sp are read, and the deceleration is calculated again. The latest engine torque difference Td is calculated, and the determination in step S9 is performed again. When the engine torque difference Td becomes equal to or smaller than the allowable torque difference Tdo (YES), fuel cut control is executed in step S10.

  Here, the correspondence between the above steps and the claims will be described. Step S2 corresponds to the deceleration request detection means in the claims, step S3 corresponds to the EGR means, and step S4 corresponds to the EGR. Steps S5 to S7 and S11 correspond to throttle valve control means, Step S8 corresponds to torque difference calculation means, and Steps S9 and S10 correspond to fuel supply stop means.

  Next, the effect | action by the said control is demonstrated using the time chart shown in FIG. The solid line indicates that according to the present embodiment, and the dotted line indicates that according to the prior art.

  That is, if the vehicle is traveling at a predetermined vehicle speed or higher and the engine rotational speed N is traveling at a predetermined rotational speed or higher, the accelerator opening θa becomes zero (non-depressed state) by the occupant's accelerator pedal operation. It is determined that there is a deceleration request (when indicated by symbol a).

  Then, the fully closed control of the EGR valve 31 starts immediately. On the other hand, the fully closed control of the throttle valve 14 does not start immediately as in the prior art, and the throttle opening θs does not increase until the predicted value E of the in-cylinder EGR rate becomes equal to or less than the predetermined value Eo. The fully closed control is started only when the opening degree θso when it is determined that there is a deceleration request is maintained and the EGR rate E becomes equal to or less than the predetermined value Eo (indicated by symbol a).

  According to this, since it is determined that there is a deceleration request and until the predicted value E of the in-cylinder EGR rate becomes equal to or less than the predetermined value Eo, fresh air continues to be supplied to the in-cylinder. After the determination, even if the exhaust gas remaining on the downstream side of the EGR valve 31 in the EGR passage 30 continues to be supplied after being delayed into the cylinder, the actual in-cylinder EGR rate does not rapidly increase as in the prior art. The occurrence of misfire is surely prevented.

  In this case, as described above, the fully closed speed of the throttle valve 14 is set to a speed corresponding to the deceleration of the engine speed N and the gear stage Sp, and the gear stage is a drive system of the engine 1 or the like. However, the higher the speed is, the higher the speed is likely to cause resonance. According to this, during this full-closed control, the drive system such as the engine is less likely to resonate regardless of the shift stage Sp, and as a result, a tip-out shock is also prevented.

  When the fully closed control of the throttle valve 14 is started as described above, the engine torque T starts to decrease correspondingly. Simultaneously with the start of the full-close control of the throttle valve 14, the calculation of the torque difference Td of the engine torque T generated before and after the fuel cut is started based on the engine speed N and the current gear stage Sp. Then, when the torque difference Td becomes the allowable torque difference Tdo (predetermined torque difference) (indicated by a symbol C), the fuel supply to the engine 1 is stopped.

  According to this, since the fuel supply is stopped when the torque difference Td of the engine torque T generated before and after the fuel cut becomes equal to or less than the allowable torque difference Tdo, the vehicle body is accompanied by the fuel cut (stop of fuel supply). The shock that occurs is prevented. In this case, the shock associated with the fuel cut is more likely to occur as the gear position is on the low speed side even when the torque difference Td is the same. However, according to the present embodiment, the allowable torque difference Tdo is equal to the gear stage Sp. Since the value is set to a smaller value as the speed is on the low speed side, the shock associated with the fuel cut can be surely prevented at any speed stage.

  In the above-described embodiment, the engine 1 that injects combustion into the intake passage 10 has been described. However, the present invention is not limited to this, and can be applied to, for example, a cylinder injection engine.

  The present invention can be widely applied to engines configured to stop fuel supply when a deceleration request occurs and to recirculate exhaust gas from the exhaust passage to the intake passage.

1 is a configuration diagram of an engine according to an embodiment of the present invention. It is an example of the flowchart of control of this engine. It is a map used when setting the valve closing speed of a throttle valve. It is a map used for the calculation of the engine torque difference which arises before and after a fuel cut. It is a characteristic view with respect to the gear position of the allowable torque difference. It is a time chart which shows an example of the effect | action of this control.

Explanation of symbols

1 Engine 10 Intake passage 14 Electric intake throttle valve 20 Exhaust passage 30 EGR passage (EGR means)
31 EGR valve (EGR means)
41 Engine speed sensor (operating state detection means)
45 gear detection means 50 engine control unit (deceleration request detection means, fuel supply stop means, throttle valve control means, EGR rate estimation means, torque difference calculation means)

Claims (4)

Engine control apparatus comprising: deceleration request detecting means for detecting a deceleration request; and fuel supply stopping means for stopping fuel supply to the engine at a predetermined time after the deceleration request is detected by the deceleration request detecting means Because
An electric intake throttle valve;
Throttle valve control means for controlling the throttle valve;
EGR means for recirculating exhaust gas from the exhaust passage to the intake passage downstream of the throttle valve;
An operating state detecting means for detecting an operating state of the engine;
EGR rate estimating means for estimating an in-cylinder EGR rate based on the engine operating state detected by the operating state detecting means,
When the deceleration request is detected by the deceleration request detection means, the EGR means stops the exhaust gas recirculation, and the throttle valve control means has a predetermined in-cylinder EGR rate estimated by the EGR rate estimation means. While the value is exceeded, the opening degree of the throttle valve is maintained at the opening degree when the deceleration request is detected. The engine control device according to claim 1,
Gear stage detecting means for detecting the gear stage of the transmission is provided,
When the in-cylinder EGR rate estimated by the EGR rate estimating unit is equal to or lower than a predetermined value and the electric intake throttle valve is closed, the throttle valve control unit closes as the gear position is higher. An engine control device characterized by increasing the speed of operation. The engine control device according to claim 2,
Torque difference calculation means is provided for calculating an engine torque difference before and after the fuel supply is stopped when fuel supply to the engine is stopped by the fuel supply stop means after the electric intake throttle valve is closed. ,
The fuel supply stop means stops the fuel supply when the engine torque difference calculated by the torque difference calculation means becomes a predetermined torque difference or less. The engine control device according to claim 3,
The engine control apparatus according to claim 1, wherein the predetermined torque difference is set to a smaller value as the shift speed detected by the shift speed detection means is closer to a lower speed.

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