JP2007187134A - Hydrocarbon adsorbing material purge controller for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an HC adsorbing material purge controller for an internal combustion engine capable of reducing deterioration of fuel economy when purge control is unnecessary. <P>SOLUTION: The internal combustion engine provided with an HC adsorbing material adsorbing HC remaining in an intake system during engine stoppage, is provided with a purge executing means for introducing purge air to the HC adsorbing material and discharging the HC into intake air, an HC discharge amount estimating means for estimating an HC discharge amount discharged from the HC adsorbing material, a determining means for determining whether or not the HC discharge amount acquired by the HC discharge amount estimating means exceeds a predetermined value, and a purge execution stopping means for stopping purge execution by the purge executing means when it is determined that the HC discharge amount from the HC adsorbing material is less than the predetermined value by the determining means. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a hydrocarbon adsorbent purge control device for an internal combustion engine that reduces the amount of hydrocarbon (hereinafter referred to as “HC”) discharged from the internal combustion engine.

  In general, in recent automobiles, in order to reduce the amount of HC emitted, the amount of unburned HC is reduced by improving the combustion of the engine, and a catalyst such as a three-way catalyst is installed in the exhaust system to discharge HC from the engine. To purify.

  By the way, after the engine is stopped, a part of the fuel injected during the previous operation remains in the intake passage such as the surge tank due to blow-back or the like, and when the engine is stopped, the fuel is little by little from the fuel injection valve. It may leak and diffuse into the intake passage. There is known an internal combustion engine including a hydrocarbon adsorbent that adsorbs hydrocarbons remaining in the intake system in order to prevent the fuel (HC) diffused in the intake passage from being released into the atmosphere as it is. Yes.

  On the other hand, the fuel (HC) diffused into the intake passage and stopped by the hydrocarbon adsorbent after the engine is stopped is sucked into the cylinder at the next engine start. However, immediately after the start of cranking, the fuel injection of the fuel injection valve is not started until the cylinder discrimination is completed, and combustion does not occur in the cylinder. Therefore, the HC sucked into the cylinder is not combusted in the exhaust pipe. To be discharged. In addition, at the time of cold start, since the exhaust system catalyst is in an inactive state, HC in the exhaust cannot be sufficiently purified. As a result, the HC adsorbed on the hydrocarbon adsorbent may be discharged into the atmosphere as it is.

  Therefore, in Patent Document 1, HC remaining in the intake passage of the internal combustion engine while the engine is stopped is adsorbed by the hydrocarbon adsorbent and adsorbed by the hydrocarbon adsorbent after the activation of the catalyst and / or after the activation of the exhaust gas sensor. A hydrocarbon adsorbent purge control technique is disclosed in which the released HC is released into the intake air by the hydrocarbon release control means.

JP 2002-39025 A

  According to the technique disclosed in Patent Document 1, even if HC released from the hydrocarbon adsorbent is not sufficiently burned in the cylinder and discharged to the exhaust pipe, the HC is purified by the catalyst in the active state. The In general, the fuel injection amount is corrected to decrease in accordance with the amount of HC released by air-fuel ratio feedback control based on detection of the air-fuel ratio by an exhaust gas sensor (air-fuel ratio sensor, oxygen sensor, etc.) that is activated prior to the catalyst. Therefore, the amount of HC discharged from the internal combustion engine is reduced.

  However, in the hydrocarbon adsorbent purge control technique disclosed in Patent Document 1, after the amount of HC adsorption in the hydrocarbon adsorbent decreases, in other words, even after the HC adsorption capacity of the hydrocarbon adsorbent recovers, The introduction of purge air to the adsorbent continues, and intake resistance is generated accordingly. As a result, the introduction of purge air into the hydrocarbon adsorbent for hydrocarbon adsorbent purge control, which is required for a short time after the engine is started, is continued during engine operation, resulting in a deterioration in fuel consumption due to the intake resistance. Have come.

  An object of the present invention is to provide a hydrocarbon adsorbent purge control device for an internal combustion engine that can solve such a conventional problem and can reduce deterioration of fuel consumption when purge control is unnecessary.

  A hydrocarbon adsorbent purge control device for an internal combustion engine according to an aspect of the present invention that solves the above-described problems is an internal combustion engine that includes a hydrocarbon adsorbent that adsorbs hydrocarbons remaining in an intake system while the engine is stopped. Purge execution means for introducing purge air into the hydrocarbon adsorbent and releasing hydrocarbons into the intake air at a predetermined condition after start-up, and hydrocarbon release for estimating the amount of hydrocarbon released from the hydrocarbon adsorbent Amount estimation means, determination means for determining whether the hydrocarbon release amount obtained by the hydrocarbon release amount estimation means exceeds a predetermined value, and the hydrocarbon release amount from the hydrocarbon adsorbent by the determination means Purge execution stop means for stopping purge execution by the purge execution means when it is determined that the value is equal to or less than a predetermined value.

  According to this aspect, when the hydrocarbon release amount obtained by the hydrocarbon release amount estimation means for estimating the hydrocarbon release amount released from the hydrocarbon adsorbent is determined to be equal to or less than the predetermined value by the determination means, the purge is executed. The purge execution by the purge execution means is stopped by the stop means. As a result, the introduction of purge air introduced to the hydrocarbon adsorbent to release the hydrocarbon adsorbed on the hydrocarbon adsorbent into the intake air is stopped, so intake resistance does not occur and fuel consumption deterioration is reduced. Is done.

  Here, the hydrocarbon emission amount estimation means is a supply air-fuel ratio determined by a cylinder intake air amount detected by an intake air flow rate sensor and a fuel injection amount from a fuel injection valve, and an exhaust gas detected by an air-fuel ratio sensor. It is preferable that the hydrocarbon release amount is estimated based on the hydrocarbon adsorbent purge air-fuel ratio determined by the air-fuel ratio and the purge air flow rate detected by the purge air flow rate sensor.

  According to this aspect, the supply air-fuel ratio is obtained from the detected value of the cylinder intake air amount detected by the intake air flow rate sensor and the fuel injection amount that is the set value, and the exhaust air-fuel ratio is detected by the air-fuel ratio sensor. Therefore, the hydrocarbon adsorbent purge air-fuel ratio can be determined more accurately. Since the purge air flow rate, which is one element for calculating the hydrocarbon adsorbent purge air-fuel ratio, is obtained as a detection value by the purge air flow rate sensor, the hydrocarbon discharge amount can be estimated more accurately.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
As shown in FIG. 1, a throttle valve 14 is provided in an intake pipe 12 of an engine 10 that is an internal combustion engine, and a surge tank 16 is provided downstream of the throttle valve 14. The surge tank 16 communicates with an intake manifold 18 for introducing air into each cylinder of the engine 10, and a fuel injection valve 20 for injecting fuel is attached in the vicinity of the intake port of the intake manifold 18 of each cylinder. . The intake pipe 12, the surge tank 16, and the intake manifold 18 constitute an intake passage.

  Further, the surge tank 16 is provided with an HC adsorbent 22 as a hydrocarbon adsorbent at the bottom thereof, so that the HC remaining in the intake passage when the engine is stopped is adsorbed by the HC adsorbent 22. . The HC adsorbent 22 is formed of activated carbon or a catalyst component having an HC adsorption action (for example, a noble metal such as Pd). Alternatively, the HC adsorbent 22 may be formed by supporting Pd or the like on an alumina layer, or may be formed of zeolite. Of course, the HC adsorbent 22 may be formed by combining two or more of activated carbon, zeolite, and catalyst components.

  In this embodiment, the recess 24 is formed at the bottom of the surge tank 16, and most of the HC adsorbent 22 is accommodated in the recess 24, so that the cross-sectional area of the surge tank 16 is narrowed by the HC adsorbent 22. Not to be. Further, a purge air introduction pipe 26 for introducing purge air into the HC adsorbent 22 is connected between the upstream side of the throttle valve 14 of the intake pipe 12 and the recess 24 of the surge tank 16. In the middle of this, for example, a valve 28 constituted by an electromagnetic valve is provided. When the valve 28 is closed, the introduction of purge air to the HC adsorbent 22 is stopped, and the state in which the HC adsorbent 22 has adsorbed HC and the state in which the release has been completed is maintained. On the other hand, when the valve 28 is opened, purge air is introduced into the HC adsorbent 22 and the purge air flows into the surge tank 16 through a large number of gaps in the HC adsorbent 22. HC is released into the intake air.

  An intake air flow rate sensor 30 for measuring the flow rate of air introduced into the engine 10 is provided on the upstream side of the throttle valve 14 of the intake pipe 12, and on the downstream side of the valve 28 of the purge air introduction pipe 26, A purge air flow sensor 32 for measuring the purge air flow rate is provided.

  On the other hand, the exhaust pipe 34 of the engine 10 is provided with a catalyst 36 such as a three-way catalyst for purifying HC and NOx in the exhaust gas, and an air-fuel ratio for detecting the air-fuel ratio of the exhaust gas upstream of the catalyst 36. A sensor 38 is provided.

  An engine electronic control circuit (hereinafter referred to as “ECU”) 40 is mainly composed of a microcomputer, controls the fuel injection amount and ignition timing in accordance with the engine speed and load, and is a ROM (storage medium). The HC adsorbed on the HC adsorbent 22 while the engine is stopped is released into the intake air after the air-fuel ratio sensor 38 and the catalyst 36 are activated. Based on the amount of HC released from the HC adsorbent 22, the timing for stopping the adsorbent purge control is determined.

  Hereinafter, an example of the processing procedure of the adsorbent purge control program according to the embodiment of the present invention will be described with reference to the flowcharts shown in FIGS. This program is executed, for example, after an ignition switch (not shown) is turned on. When this program is activated, it is first determined in step S201 whether purge control is being executed. The execution of the purge control is executed when the air-fuel ratio sensor 38 is in an active state based on the determination as to whether the air-fuel ratio sensor 38 is in an active state. This is because during the period when the air-fuel ratio sensor 38 is inactive, the air-fuel ratio of the exhaust gas cannot be detected and the air-fuel ratio feedback control cannot be performed. Note that whether or not the air-fuel ratio sensor 38 is in an active state can be determined based on, for example, the coolant temperature or the elapsed time after startup. When the purge control is executed, the valve 28 is kept open, purge air is introduced into the HC adsorbent 22, and the purge air passes through a large number of gaps in the HC adsorbent 22 and the surge tank 16. And HC is discharged from the HC adsorbent 22 into the intake air.

  If it is determined in step S201 that the purge control is being executed, the process proceeds to step S202, and the HC release amount Fp per unit time from the HC adsorbent 22 is estimated. The estimation of the HC release amount will be described later with reference to the flowchart shown in FIG. 3 executed as a subroutine.

  Next, the process proceeds to step S203, and it is determined whether or not the HC release amount Fp per unit time from the HC adsorbent 22 obtained in step S202 is equal to or greater than a predetermined value C. Here, the predetermined value C is set based on the HC adsorption rate in the HC adsorbent 22. That is, when the maximum HC adsorption capacity of the HC adsorbent 22 is 100%, the value corresponding to the amount of HC released from the HC adsorbent 22 per unit time when the HC adsorption rate is, for example, several percent. is there. As a result of the purge execution, when the HC adsorption rate in the HC adsorbent 22 decreases, the amount of HC released per unit time also gradually decreases, so the purge is executed in a state where the HC release amount Fp is below a predetermined value C. Even so, an effective HC desorption action cannot be expected so much, and only the intake resistance is provided for the amount of purge air introduced into the purge air introduction pipe 26. Furthermore, in the state where the HC adsorption rate in the HC adsorbent 22 is reduced to the extent that the HC release amount Fp falls below the predetermined value C, it can be considered that the HC adsorption capacity has been recovered.

  Therefore, when the determination in step S203 shows that the HC release amount Fp per unit time from the HC adsorbent 22 is less than the predetermined value C, the process proceeds to step S204, and the purge control is stopped. That is, the valve 28 is closed and the introduction of purge air into the purge air introduction pipe 26 is stopped.

Here, the estimation routine of the HC release amount in step S202 described above will be described with reference to the flowchart of FIG. In this HC release amount estimation routine, first, in step S301, a supply air-fuel ratio (hereinafter referred to as supply A / F) is acquired. This supply A / F is determined by the in-cylinder intake air amount Ga as a detection value detected by the intake air flow rate sensor 30 and the fuel injection amount Fj injected from the fuel injection valve 20.
“Supply A / F = Ga / Fj (1)”
Is obtained by calculation. The fuel injection amount Fj is obtained in advance by experiments or the like corresponding to the rotational speed and load of the engine 10, and is obtained as a set value from a map stored in the ROM of the ECU 40.

Next, in step S302, an exhaust air-fuel ratio (hereinafter referred to as exhaust A / F) is acquired. The exhaust A / F is obtained as a detection value detected by the air-fuel ratio sensor 38. In step S303, the HC adsorbent purge air-fuel ratio (hereinafter referred to as HC adsorbent purge A / F) is calculated by the following equation (2).
“HC adsorbent purge A / F = exhaust A / F−supply A / F (2)”
In step S304, the purge air flow rate Gp obtained as a detection value detected by the purge air flow rate sensor 32 is acquired. Further, the process proceeds to step S305, and the HC release amount Fp per unit time from the HC adsorbent 22 is reduced by the purge air flow rate Gp acquired in step S304 and the HC adsorbent purge A / F calculated in step S303. Calculated by equation (3).
“HC adsorbent purge A / F = Gp / Fp → Fp = Gp / (HC adsorbent purge A / F) (3)”
Thus, in the present embodiment, the supply A / F is obtained from the detected value of the cylinder intake air amount Ga detected by the intake air flow rate sensor 30 and the fuel injection amount Fj that is the set value, and the exhaust A Since / F is obtained from the detection value detected by the air-fuel ratio sensor 38, the HC adsorbent purge A / F by these is obtained more accurately. Since the purge air flow rate Gp, which is one element for calculating the HC adsorbent purge A / F, is obtained as a detected value by the purge air flow rate sensor 32, the HC release amount Fp can be estimated more accurately. .

  Here, returning to the flowchart of FIG. 2, the HC release amount Fp per unit time from the HC adsorbent 22 obtained in the HC release amount estimation routine (steps S301 to S305) in step S202 described above is a predetermined value C. If it is determined in step S203 that it is above, this routine is once ended, the valve 28 is opened, and a predetermined purge air flow rate Gp is introduced into the HC adsorbent 22 through the purge air introduction pipe 26. Purge control for releasing HC from the HC adsorbent 22 is continued.

  Further, as described above, when the HC release amount Fp per unit time from the HC adsorbent 22 is below the predetermined value C in the determination in step S203, the process proceeds to step S204, and the valve 28 is set so that the purge control is stopped. Although the valve 28 is closed, the valve 28 may be kept closed during the same operation period after the engine is started once the purge control is stopped to stop the purge control. This is because there is almost no HC adsorption to the HC adsorbent 22 during this period.

  In this embodiment, the purge control is executed when the air-fuel ratio sensor 38 is in the active state. However, this is executed after both the air-fuel ratio sensor 38 and the catalyst 36 are in the active state. It may be. In this case, even if the HC released from the HC adsorbent 22 is not sufficiently burned in the cylinder and discharged to the exhaust pipe 34, the HC can be purified by the active catalyst 36.

  According to the present embodiment described above, when the HC release amount obtained by the HC release amount estimation means for estimating the HC release amount released from the HC adsorbent 22 is determined to be equal to or less than the predetermined value by the determination means, the purge is performed. Since the purge execution by the purge execution unit is stopped by the execution stop unit, the introduction of the purge air introduced into the HC adsorbent 22 in order to release the HC adsorbed by the HC adsorbent 22 into the intake air is stopped. No resistance is generated and fuel consumption is reduced.

It is a schematic diagram which shows the outline | summary of one embodiment of this invention. It is a flowchart which shows one form of control of embodiment of this invention. It is a flowchart which shows one form of control of embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Engine 20 Fuel injection valve 22 HC adsorption material 26 Purge air introduction pipe 28 Valve 30 Intake air flow rate sensor 32 Purge air flow rate sensor 36 Catalyst 38 Air fuel ratio sensor 40 ECU

Claims (2)

In an internal combustion engine provided with a hydrocarbon adsorbent that adsorbs hydrocarbons remaining in the intake system while the engine is stopped,
Purge execution means for introducing purge air into the hydrocarbon adsorbent and releasing hydrocarbons into the intake air at a predetermined condition after engine startup;
A hydrocarbon release amount estimation means for estimating a hydrocarbon release amount released from a hydrocarbon adsorbent, and a determination for determining whether or not the hydrocarbon release amount obtained by the hydrocarbon release amount estimation means exceeds a predetermined value Means,
A purge execution stop means for stopping the purge execution by the purge execution means when the determination means determines that the hydrocarbon release amount from the hydrocarbon adsorbent is equal to or less than a predetermined value;
A hydrocarbon adsorbent purge control device for an internal combustion engine, comprising: The hydrocarbon emission amount estimation means is based on the supply air-fuel ratio determined by the in-cylinder intake air amount detected by the intake air flow rate sensor and the fuel injection amount from the fuel injection valve, and the exhaust air-fuel ratio detected by the air-fuel ratio sensor. 2. The carbonization of an internal combustion engine according to claim 1, wherein the hydrocarbon release amount is estimated based on a determined hydrocarbon adsorbent purge air-fuel ratio and a purge air flow rate detected by a purge air flow rate sensor. Hydrogen adsorbent purge control device.

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