JP2008280941A - Residual gas estimation device for engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device capable of estimating residual gas with an extremely simple method. <P>SOLUTION: This device is provided with a fuel supply device 21, an ignition device 14, an idling rotation speed reduction means 31 temporarily reducing engine rotation speed under an idling rotation condition of an engine, and a residual gas estimation means 31 estimating residual gas in a combustion chamber based on reduction quantity of idling rotation speed or reduction rate of idling rotation speed. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an engine residual gas estimation device.

There is one that detects the rate of increase of the engine speed during the explosion stroke and estimates the residual gas rate in the combustion chamber based on this value (see Patent Document 1).
JP 2004-176669 A

  By the way, since combustion in the combustion chamber varies from cycle to cycle, the residual gas rate in the combustion chamber is not calculated based on the rotational speed increase rate in one explosion stroke, as in the technique of Patent Document 1 above. The residual gas rate in the combustion chamber cannot be accurately estimated.

  Accordingly, an object of the present invention is to provide an apparatus capable of estimating residual gas by a very simple method.

  The first invention includes a fuel supply device, an ignition device, and idle rotation speed reduction means for temporarily reducing the engine rotation speed in an idle rotation state of the engine, and the idle rotation speed reduction means is in the idle rotation state. When the idle rotation speed, which is the engine rotation speed of the engine, is reduced, the residual gas in the combustion chamber is estimated based on the reduction rate of the idle rotation speed or the decrease rate of the idle rotation speed.

  According to the present invention, since the residual gas in the combustion chamber is estimated based on the idle rotation speed reduction allowance or the idle rotation speed reduction rate when the idle rotation speed is temporarily reduced, an extremely simple measurement method is used. Residual gas can be estimated. In addition, no new sensor is required, and it is only necessary to have a rotational speed sensor already provided in the engine that can measure the rotational speed of the engine, thereby preventing an increase in cost.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 shows a schematic configuration of an engine residual gas estimation device.

  The air metered by the intake throttle valve 23 is stored in the intake collector 2 and then introduced into the combustion chamber 5 of each cylinder via the intake manifold 3. Fuel is injected and supplied into the intake port 4 at a predetermined timing from a fuel injection valve 21 (fuel supply device) disposed in the intake port 4 of each cylinder. The fuel injection amount given to the fuel injection valve 21 depends on the intake air flow rate detected by the air flow meter 32 by the engine controller 31 and the engine speed calculated based on the signals from the crank angle sensors (33, 34). Is calculated.

  The fuel injected toward the intake valve 15 is mixed with intake air to form an air-fuel mixture. The air-fuel mixture is confined in the combustion chamber 5 by closing the intake valve 15 and compressed by the rise of the piston 6, and the spark plug 14 (ignition device) ignites and burns. The gas pressure due to the combustion works to push down the piston 6, and the reciprocating motion of the piston 6 is converted into the rotational motion of the crankshaft 7. The combusted gas (exhaust gas) is discharged into the exhaust passage 8 when the exhaust valve 16 is opened.

  The intake throttle valve 23 is driven by a throttle motor 24. Since the torque required by the driver appears in the amount of depression of the accelerator pedal 41 (accelerator opening), the engine controller 31 determines a target torque based on a signal from the accelerator sensor 42, and a target air for realizing this target torque. The amount is determined, and the opening degree of the intake throttle valve 23 is controlled via the throttle motor 24 so that this target air amount is obtained.

  A variable valve mechanism (hereinafter referred to as “VEL mechanism”) 26 configured by a multi-node link mechanism that continuously and variably controls the valve lift amount and the operating angle of the intake valve 15, the crankshaft 7, and the intake valve And a variable valve timing mechanism (hereinafter referred to as a “VTC mechanism”) 27 that advances and retards the valve timing of the intake valve 15 by continuously variably controlling the rotational phase difference with the camshaft 25 for use. These VEL mechanism 26 and VTC mechanism 27 constitute a variable valve gear. Since the specific configuration of each of the mechanisms 26 and 27 is known from Japanese Patent Laid-Open No. 2003-3872, detailed description thereof is omitted. Note that the present invention is not limited to this case, and only one of the two mechanisms 26 and 27 may be provided. The variable valve mechanism can also be provided on the exhaust valve 16 side.

  If the fuel injection by the fuel injection valve 21 and the spark ignition by the spark plug 14 are appropriately performed while cranking the crankshaft 7 with the starter motor at the start, the rotational speed of the crankshaft 7 (= engine rotational speed) tends to overshoot. After reaching a peak, it reverses and settles to the engine speed in the idling state.

  On the other hand, the exhaust passage 8 includes three-way catalysts 9 and 10. Of these, the upstream three-way catalyst 9 is mounted near the engine outlet where a high exhaust temperature is obtained, so that it is integrated with the exhaust manifold, and the downstream three-way catalyst 10 is provided under the floor of the vehicle. When these three-way catalysts 9 and 10 have the air-fuel ratio of the exhaust gas from the engine in the aforementioned window, the conversion efficiency of NOx, CO, and HC is optimized, but the temperature of the three-way catalysts 9 and 10 increases. Since a sufficient conversion rate cannot be obtained unless it is activated, it is necessary to raise the inlet temperature of the upstream three-way catalyst 9 immediately after the cold start.

  In order to satisfy the requirement for the early temperature increase of the upstream side three-way catalyst 9 immediately after the cold start and to suppress the overshoot of the engine speed that occurs during the transition from the start to the idle rotation state (starting process), the engine The controller 31 performs feedback control of the engine rotation speed (hereinafter referred to as “idle rotation speed”) in the idle rotation state. The idle rotation speed feedback control includes ignition timing feedback control and intake air amount feedback control. For example, the ignition timing is delayed when the actual idle rotation speed is higher than the allowable range centered on the target rotation speed during idling (hereinafter simply referred to as “target rotation speed”) while the intake amount is maintained in the initial state. The idle rotation speed is returned to the target rotation speed by turning the angle, and conversely, when the actual idle rotation speed is lower than the allowable width centered on the target rotation speed, the ignition timing is advanced to advance the idle rotation. Return the speed to the target speed. Further, when the actual idle rotation speed is higher than the allowable range provided around the target rotation speed while maintaining the ignition timing in the initial state, the opening (intake amount) of the intake throttle valve 23 is decreased to reduce the idle rotation. By returning the speed to the target rotational speed, and conversely, when the actual idle rotational speed is lower than the allowable width provided around the target rotational speed, the opening (intake amount) of the intake throttle valve 23 is increased. Return the idle speed to the target speed.

  Further, in the present invention, immediately after shifting to the idle rotation state, the idle rotation speed is temporarily reduced, and the residual gas in the combustion chamber is estimated based on the idle rotation speed decrease rate or the idle rotation speed decrease rate at that time. To do.

Here, the residual gas estimation principle will be described. FIG. 2 shows that the ignition timing is retarded by a predetermined value ΔADV from the ignition timing ADV0 at the start in a state where the intake air amount (intake air amount) Qa is kept constant in the idling rotation state. It shows how the actual idling speed changes when the idling speed is temporarily reduced. That is, the idle rotation speed decreases by 800 rpm (target rotation speed) from the timing t1 when the ignition timing is retarded by the predetermined value ΔADV, and the engine has a constant value at the timing t2 after the elapse of the predetermined time Δt from t1. The rotational speed (800−Δn _e ) is settled. In this case, the value of the drop allowance [Delta] n _e divided by a predetermined time Delta] t of the idle rotational speed, represents the actual rate of decrease in idle speed, reduction rate [Delta] n _e / Delta] t of the actual idle speed is the combustion chamber 5 It depends on the residual gas inside. That is, if the idle rotation speed decrease rate Δn _e / Δt is large, the residual gas in the combustion chamber is large. On the other hand, when the idle rotation speed decrease rate Δn _e / Δt is small, the residual gas in the combustion chamber is small. It is done. In order to calculate the idle rotation speed decrease rate Δn _e / Δt, it is not necessary to wait for the predetermined time Δt to elapse. In short, the idle rotation speed is assumed to decrease linearly, and the slope of the straight line is calculated. do it.

Figure 3 shows how the idling speed N _e is how changes when changing the residual gas ratio in the combustion chamber and the retard amount of the ignition timing in the range of 0-30% in the model. According to FIG. 3, if the ignition timing retard amount is the same, the residual gas ratio in the combustion chamber increases from 0% → 10% → 20% → 30% from the idle rotation speed when the ignition timing retard amount is zero. it can be seen that drop allowance of the idle rotational speed N _e is increased.

Therefore, when the horizontal axis shows the amount of residual gas (or residual gas rate) again and the vertical axis shows the idle rotation speed decrease rate Δn _e / Δt, the characteristics shown in FIG. 4 are obtained. FIG. 4 shows that the decrease rate Δn _e / Δt of the idle rotation speed tends to increase as the amount of residual gas (residual gas rate) increases. In this way, a characteristic representing the relationship between the amount of residual gas in the combustion chamber and the idle rotation speed reduction rate Δn _e / Δt was obtained. Based on FIG. 4, the idle rotation speed reduction rate Δn _e / Δt is based. For example, the amount of residual gas in the combustion chamber can be estimated.

  The contents of this control executed by the engine controller 31 will be described in detail according to the flowchart of FIG.

  The flowchart of FIG. 2 shows a time-series processing procedure. However, it is assumed that the engine is in an idle rotation state.

  In step 10, the cooling water temperature detected by the water temperature sensor 37 (see FIG. 1) is read, and in step 11, it is determined whether or not the read cooling water temperature is stable at around 80 ° C. When the cooling water temperature is not stable at 80 ° C. or lower, it is determined that the cooling water temperature is immediately after the cold start, and the process returns to step 10.

  If the cooling water temperature is stable at around 80 ° C., the process proceeds to step 12 to read the actual idle rotational speed (abbreviated as “ENG rotational speed” in the figure), and in step 13, the actual idle rotational speed is 800 rpm (target rotational speed). Check if it is stable near (speed). When the actual idle rotation speed is not stable around 800 rpm, the process returns to step 12. The engine speed is calculated based on signals from a POS sensor (position sensor) 33 and a PHASE sensor (phase sensor) 34.

  If the actual idling speed is stable at around 800 rpm, the process proceeds from step 13 to step 14 to control the ignition timing (abbreviated as “ADV” in the figure) to settle the idling speed near the target speed. Or stop the feedback control of the intake air amount.

  In step 15, the actual idle speed is read again, and in step 16, it is determined whether or not the actual idle speed is stable near 800 rpm. When the actual idle rotation speed is not stable around 800 rpm, the process returns to step 14.

  Even if the feedback control of the ignition timing and the feedback control of the intake air amount are stopped, if the actual idle speed is stabilized at around 800 rpm, the routine proceeds from step 16 to step 17 where the ignition timing is retarded by a predetermined value ΔADV. The predetermined value ΔADV is determined in advance by matching.

The reason for retarding the ignition timing is that when the ignition timing is retarded, the idle rotational speed decreases, and the idle rotational speed decrease rate Δn _e / Δt depends on the amount of residual gas in the combustion chamber. This is because the amount of residual gas in the combustion chamber is estimated from the decrease rate Δn _e / Δt.

In step 18, the actual idle speed is read again, and in step 19, it is checked whether or not the actual idle speed has decreased below 800 rpm. When the actual idle rotation speed is decreased to less than 800 rpm due to the ignition timing retard, the process proceeds from step 19 to step 20 to calculate the actual idle rotation speed decrease rate Δn _e / Δt. As described above, it is not necessary to calculate the idle rotation speed reduction rate Δn _e / Δt after waiting for the idle rotation speed to settle to a constant value, and the actual idle rotation speed decreases linearly. Then, it is sufficient to calculate the slope of the straight line.

In step 21, the actual idle rotation speed decrease rate Δn _e / Δt is compared with a predetermined value (see FIG. 4). When the actual idle speed reduction rate Δn _e / Δt is equal to or greater than a predetermined value, the routine proceeds to step 22 where the amount of residual gas in the combustion chamber is large (the residual gas rate in the combustion chamber is large). When the rotational speed reduction rate Δn _e / Δt is less than the predetermined value, the routine proceeds to step 23 where it is determined that the residual gas in the combustion chamber is small (the residual gas rate in the combustion chamber is small).

  In this manner, since the predetermined value determines whether the residual gas in the combustion chamber is large or small (whether the residual gas ratio in the combustion chamber is large or small), the predetermined value is determined in advance by matching.

  On the other hand, even if the ignition timing is retarded in step 17, if the actual idle rotation speed has not decreased below 800 rpm in step 19, the process proceeds from step 19 to step 24, and the variable valve mechanism comprising the VEL mechanism 26 and VTC mechanism 27. Is used to reduce the valve overlap width of the intake and exhaust valves 15 and 16 and retard the ignition timing by a predetermined value. The reason for further retarding the ignition timing is to increase the exhaust gas temperature by retarding the ignition timing and to promote the activation of the catalyst. In this case, the overlap width is reduced for the following reason. That is, although the exhaust temperature rises due to the ignition timing retard, the combustion becomes unstable. Therefore, the overlap between the intake and exhaust valves 15 and 16 is reduced to reduce the residual gas in the combustion chamber so that the combustion does not become unstable even if the ignition timing is retarded.

  Here, the effect of this embodiment is demonstrated.

According to the present embodiment (the invention described in claim 1), the fuel injection valve 21 (fuel supply device), the ignition plug 14 (ignition device), and the idle rotation speed reduction means for temporarily reducing the idle rotation speed. (Refer to step 17 in FIG. 5), the residual gas in the combustion chamber is reduced based on the decrease rate Δn _e / Δt of the idle rotation speed when the idle rotation speed reduction means temporarily decreases the idle rotation speed. Since the estimation is performed (see steps 20 to 23 in FIG. 5), it is possible to estimate whether the residual gas in the combustion chamber is large or small by an extremely simple measurement method.

  Further, no new sensor is required, and the engine rotational speed sensor (33, 34) already provided in the engine that can measure the engine rotational speed may be used, so that an increase in cost can be prevented.

According to the present embodiment (the invention described in claim 2), the actual idle speed reduction rate Δn _e / Δt is compared with a predetermined value, and the idle speed reduction rate Δn _e / Δt is larger than the predetermined value. When the residual gas amount in the combustion chamber is large, it is estimated that the residual gas amount in the combustion chamber is small when the decrease rate Δn _e / Δt of the idle rotation speed is smaller than a predetermined value (see step 21 in FIG. 5). In this embodiment, it is only necessary to adapt the predetermined value, and therefore, the matching man-hours can be reduced compared with the conventional apparatus in which a map of the residual gas ratio is prepared in advance using the engine load and the rotational speed as parameters. It can be greatly reduced.

  According to this embodiment (the invention described in claim 3), the catalyst 9 for purifying harmful components in the exhaust gas is provided, and the idle rotation is performed by retarding the ignition timing before the catalyst 9 completes warming up. Since the speed is reduced, the activation of the catalyst 9 can be promoted.

  According to the present embodiment (the invention described in claim 4), the variable valve device (26, 27) is provided, and when the idling rotation speed does not decrease when the ignition timing is retarded (retarded), this variable operation is performed. Since the valve overlap width of the intake and exhaust valves is reduced using the valve device and the ignition timing is further retarded (see steps 17 to 19 and 24 in FIG. 5), the exhaust temperature can be further increased. Activation of the catalyst 9 can be promoted.

  If the ignition timing feedback control means for maintaining the actual idle rotation speed at the target rotation speed is provided, if the ignition timing feedback control is continued, the idle rotation speed will deviate from the target rotation speed. Therefore, the residual gas in the combustion chamber cannot be estimated. According to this embodiment (the invention according to claim 5), ignition for maintaining the actual idle rotational speed at the target rotational speed is possible. A timing feedback control means is provided, and when the residual gas in the combustion chamber is estimated, this ignition timing feedback control is stopped (see step 14 in FIG. 5), so that the actual idle rotation speed is maintained at the target rotation speed. Even when the ignition timing feedback control means is provided, the residual gas in the combustion chamber can be estimated.

In the embodiment it has been described in the case of estimating the residual gas in the combustion chamber based on the actual rate of decrease in idle speed [Delta] n _e / Delta] t, a residual in the combustion chamber based on the drop allowance [Delta] n _e of the actual idle speed The gas may be estimated. For example, compare the actual drop allowance [Delta] n _e and the predetermined value of the idle rotation speed, when drop allowance [Delta] n _e of the actual idle speed is greater than a predetermined value, the residual gas in the combustion chamber is large, the actual contrast when drop allowance [Delta] n _e of the idling rotational speed is smaller than a predetermined value, and estimates the residual gas in the combustion chamber is small.

BRIEF DESCRIPTION OF THE DRAWINGS The schematic block diagram of the residual gas estimation apparatus of the engine of 1st Embodiment of this invention. The wave form diagram which shows the change of an actual idle rotational speed when ignition timing is retarded in an idle rotational state. The characteristic diagram of the idle rotation speed with respect to the ignition timing retard amount and the residual gas ratio in the combustion chamber. The characteristic figure of the fall rate of idle rotation speed with respect to the residual gas rate in a combustion chamber. The flowchart for demonstrating estimation of the residual gas in a combustion chamber.

Explanation of symbols

4 Fuel injection valve (fuel supply device)
6 Spark plug (ignition device)
9 Upstream three-way catalyst (catalyst)
26 VEL mechanism (variable valve operating device)
27 VTC mechanism (Variable valve operating device)
31 Engine controller 33 POS sensor (Engine speed sensor)
34 PHASE sensor (engine speed sensor)

Claims (5)

A fuel supply device;
An ignition device;
Idle rotation speed lowering means for temporarily lowering the engine rotation speed in an idle rotation state of the engine;
A residual gas estimation device for an engine, comprising: residual gas estimation means for estimating residual gas in a combustion chamber based on a reduction rate of idle rotation speed or a decrease rate of idle rotation speed.   When the idle rotation speed decrease rate or idle rotation speed decrease rate is compared with a predetermined value and the idle rotation speed decrease rate or idle rotation rate decrease rate is greater than the predetermined value, the amount of residual gas in the combustion chamber is large or combustion When the residual gas rate in the chamber is large, the amount of residual gas in the combustion chamber is small or the residual gas rate in the combustion chamber is small when the reduction rate of idle rotation speed or the reduction rate of idle rotation speed is smaller than a predetermined value. The residual gas estimation device for an engine according to claim 1, wherein Equipped with a catalyst to purify harmful components in the exhaust,
2. The engine residual gas estimation device according to claim 1, wherein the idle rotation speed is lowered by retarding the ignition timing before the catalyst completes warm-up. Equipped with a variable valve gear,
The variable valve device is used to reduce the valve overlap width of the intake / exhaust valve and further retard the ignition timing when the idle rotation speed does not decrease when the ignition timing is retarded. Item 4. The engine residual gas estimation device according to Item 3. Provided with an ignition timing feedback control means for maintaining the idle rotational speed at the target rotational speed,
2. The engine residual gas estimation device according to claim 1, wherein feedback control of the ignition timing is stopped when the residual gas in the combustion chamber is estimated.

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