JP2007278174A - Fuel cut control device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cut control device of an internal combustion engine by which a user can enjoy the advantage of an improvement in fuel economy by fuel cut. <P>SOLUTION: This internal combustion engine comprises a fuel cut means for cutting a fuel to the engine under predetermined decelerating conditions, a fuel cut retarding means for retarding the start of the fuel cut by the fuel cut means after the predetermined deceleration conditions are established, and a pre-fuel cut ignition timing updating retard angle means for retarding an ignition timing while updating during the retarding of the start of the fuel cut by the fuel cut retarding means. The internal combustion engine further comprises a deceleration determination means for determining the magnitude of the deceleration of the engine or a vehicle and an ignition timing retard angle updating speed changing means for changing the ignition timing retard angle updating speed in the pre-fuel cut ignition timing updating retard angle means according to the magnitude of the deceleration by the deceleration determination means. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a fuel cut control device for an internal combustion engine, and more particularly, to a fuel cut control device for an internal combustion engine that can fully enjoy the benefits of fuel efficiency improvement due to fuel cut.

  Generally, in an internal combustion engine, in order to improve fuel efficiency, under a predetermined deceleration operation condition, for example, on the condition that the throttle valve is substantially fully closed and the engine speed is higher than a predetermined fuel cut speed, The fuel supply is cut off. However, as a result of the torque reduction due to such fuel cut, a torque step is generated and a shock is generated. Therefore, various techniques for reducing such a shock have been proposed.

  For example, in Patent Document 1, in an internal combustion engine that includes a fuel cut unit that cuts fuel supply to an engine under a predetermined deceleration operation condition, fuel from the fuel cut unit is established when a predetermined deceleration operation condition such as an idle switch ON is established. A fuel cut delay means for delaying the start of the cut for a first predetermined time is provided, and a second predetermined time shorter than the first predetermined time elapses from the satisfaction of the predetermined deceleration operation condition during the fuel cut delay time. A technique for providing ignition timing retarding means for gradually retarding the ignition timing later is disclosed. The first and second predetermined times are set to be shorter on the high speed side depending on the engine speed.

  Thus, not only waiting for the torque to decrease when the throttle valve is fully closed, but also gradually reducing the ignition timing during the delay time, thereby reducing the torque more effectively and reducing the torque step. In addition, by shortening the first and second predetermined times on the high rotation side, the start of fuel cut is accelerated, and fuel efficiency is improved.

Japanese Patent Laid-Open No. 10-30477

  By the way, the one disclosed in Patent Document 1 shortens the first and second predetermined times on the high rotation side so as to accelerate the start of fuel cut and improve fuel efficiency. The time from the start of retarding to the start of fuel cut, that is, the retarding time is made constant regardless of the engine speed. More specifically, the angle is gradually retarded at a constant update rate. As a result, for example, when the deceleration is large and the engine speed is drastically reduced, there is a problem that the fuel cut time is not sufficient and the fuel consumption cannot be sufficiently improved. This is because when the deceleration is large, the engine speed drops to the fuel cut return speed relatively quickly, so the fuel cut timing is delayed and the fuel cut time becomes extremely short, or the fuel cut time Because there will be no.

  The present invention has been made in view of the above-described conventional problems, and an object of the present invention is to provide a fuel cut control device for an internal combustion engine that can enjoy the benefits of fuel efficiency improvement due to fuel cut.

  In order to achieve the above object, a fuel cut control device for an internal combustion engine according to an aspect of the present invention includes a fuel cut means for cutting fuel to the engine under a predetermined deceleration operation condition, and establishment of a predetermined deceleration operation condition. Fuel cut delay means for delaying the start of fuel cut by the fuel cut means, and ignition timing update delay means before fuel cut for retarding while updating the ignition timing during the fuel cut start delay by the fuel cut delay means In the internal combustion engine, the deceleration determination means for determining the magnitude of the deceleration of the engine or the vehicle, and the ignition timing update delay before the fuel cut according to the magnitude of the deceleration by the deceleration determination means Ignition timing retard angle update speed changing means for changing the ignition timing retard angle update speed in the means.

  Here, it is preferable that the ignition timing retard update speed changing means increases the ignition timing retard update speed when the deceleration is large.

  According to one aspect of the present invention, the deceleration determination means determines the magnitude of the engine or vehicle deceleration, and the ignition timing retard update speed change means changes the fuel according to the determined deceleration magnitude. The ignition timing retard update speed in the pre-cut ignition timing update retard means is changed. Therefore, by retarding the ignition timing, it is possible to more effectively reduce the torque prior to the fuel cut, to reduce the torque step at the time of the fuel cut transition, to prevent the occurrence of shock, Since the ignition timing retard update speed can be changed in accordance with the magnitude of the deceleration, there is an effect that the fuel cut start delay time can be set to a time that does not cause deterioration of fuel consumption.

  Further, according to the mode in which the ignition timing retard update speed changing means increases the ignition timing retard update speed when the deceleration is large, the fuel cut start delay time is shortened when the deceleration is large, Since the start of cutting is advanced, fuel efficiency can be improved.

  Hereinafter, an embodiment of the present invention will be described. FIG. 1 is a system configuration diagram of a fuel cut control device for an internal combustion engine according to the present invention.

  An internal combustion engine (hereinafter also referred to as an engine) 10 includes a cylinder block 11 in which a plurality of cylinders are formed, a cylinder head 12 connected to the upper part of the cylinder block 11, and a reciprocating motion in each cylinder of the cylinder block 11 in the vertical direction. And a piston 13 that performs. A crankshaft 14 is connected to the lower end portion of the piston 13, and the crankshaft 14 is rotated when the piston 13 moves up and down.

  Further, a crank position sensor 40 is disposed in the vicinity of the crankshaft 14. The crank position sensor 40 is, for example, an electromagnetic pickup sensor, and is a magnetic rotor 10 connected to the crankshaft 14. It is possible to detect the crank rotation signal including the top dead center position and the crank speed, that is, the engine speed NE, by detecting the crank rotation signal at every ° and detecting the missing tooth position.

  In addition, the space defined by each cylinder block 11 and the inner wall of the cylinder head 12 and the top of the piston 13 functions as a combustion chamber for burning the air-fuel mixture. A spark plug 16 for igniting the fuel is disposed so as to protrude into the combustion chamber.

  Each spark plug 16 is connected to an ignition coil 19. An ignition signal is input to the ignition coil 19 from an ECU 70, which will be described later, at an ignition timing corresponding to the operating state of the engine 10, the primary coil is shut off, a high voltage is generated in the secondary coil, and the spark plug 16 is ignited. Is done.

  The cylinder block 11 is provided with a water temperature sensor 43 for detecting the temperature of the cooling water flowing through the cooling water passage (cooling water temperature). The cylinder head 12 has an intake port 22 and an exhaust port 32, the intake passage 20 is connected to the intake port 22, and the exhaust passage 30 is connected to the exhaust port 32. An intake valve 21 is disposed in the intake port 22 of the cylinder head 12, and an exhaust valve 31 is disposed in the exhaust port 32.

  An intake side camshaft 23 for opening and closing the intake valve 21 is disposed above the intake valve 21, and an exhaust side camshaft 33 for opening and closing the exhaust valve 31 is disposed above the exhaust valve 31. Is arranged. An intake side timing pulley and an exhaust side timing pulley are mounted on one end of each camshaft 23, 33, and each timing pulley is connected to the crankshaft 14 via a timing belt (not shown). Yes.

  Accordingly, when the engine 10 is operated, the rotational driving force is transmitted from the crankshaft 14 to the camshafts 23 and 33 via the timing belt and the timing pulleys, and the camshafts 23 and 33 are rotated to rotate the intake valves 21 and The exhaust valve 31 is opened / closed. These valves 21 and 31 are synchronized with the rotation of the crankshaft 14 and the vertical movement of the piston 13, that is, in a series of four strokes in the engine 10 including an intake stroke, a compression stroke, an explosion / expansion stroke, and an exhaust stroke. It is driven at a predetermined opening / closing timing in synchronization.

  Further, a cam position sensor 44 for detecting the valve timing of the intake valve 21 is disposed in the vicinity of the intake side camshaft 23 in the present embodiment. And a magnetic rotor (not shown) and an electromagnetic pickup (not shown) connected to each other. A plurality of teeth are formed at equal angles on the outer periphery of the magnetic rotor. For example, before the compression TDC of a predetermined cylinder, the intake camshaft 23 rotates between BTDC 90 ° and 30 °. The accompanying cam angle signal (displacement timing signal) is detected.

  An air cleaner 24 is connected to the air intake side of the intake passage 20, and a throttle valve 26 that is not directly linked to the accelerator pedal and is opened and closed by an electronically controlled throttle motor 25 is provided in the middle of the intake passage 20. It is arranged. An air flow meter 46 with a built-in intake temperature sensor is provided on the upstream side of the throttle valve 26 to detect the intake air amount.

  A throttle position sensor 45 for detecting the throttle opening is disposed in the vicinity of the throttle valve 26. The throttle position sensor 45 can reliably detect that the throttle opening is 0 °. High precision. However, instead of this, an idle contact may be provided. Further, a surge tank 27 for suppressing intake pulsation is formed on the downstream side of the throttle valve 26. The surge tank 27 in this embodiment is provided with a resonator. In addition, an injector 17 for supplying fuel to the combustion chamber is disposed in the vicinity of the intake port 22 of each cylinder. Each injector 17 is an electromagnetic valve that is opened by energization, and fuel that is pumped from a fuel pump (not shown) is supplied to each injector 17.

  Therefore, when the engine 10 is operating, the air filtered by the air cleaner 24 is taken into the intake passage 20 and fuel is injected from each injector 17 toward the intake port 22 simultaneously with the intake of the air. As a result, an air-fuel mixture is generated at the intake port 22 and the air-fuel mixture is sucked into the combustion chamber as the intake valve 21 is opened in the intake stroke.

  An upstream side three-way catalyst 36 for purifying exhaust gas is mounted immediately below the exhaust manifold in the exhaust passage 30, and a downstream side three-way catalyst 37 is disposed downstream thereof. In addition, an air-fuel ratio (A / F) sensor 47 with a heater for detecting the air-fuel ratio of the exhaust gas is disposed upstream of the upstream side three-way catalyst 36 in the middle of the exhaust passage 30, and the upstream side three-way catalyst is provided. An oxygen sensor 48 with a heater for detecting the oxygen concentration in the exhaust gas is disposed downstream of 36 and upstream of the downstream side three-way catalyst 37. In addition, an output shaft rotational speed sensor 49 that detects the rotational speed of the output shaft of the transmission is also connected to the ECU 70 described later.

  In the engine system according to the present embodiment, a variable valve timing mechanism (hereinafter referred to as “a hydraulic valve control mechanism”) that is hydraulically controlled via the hydraulic control valve 50 in order to change the valve overlap amount by changing the opening / closing timing of the intake valve 21. VVT ") is provided. This VVT is a mechanism for continuously changing the valve timing of the intake valve 21 by changing the phase angle of the intake camshaft 23 with respect to the rotation of the crankshaft 14. The phase angle can be detected.

  An electronic control unit (hereinafter referred to as ECU) 70 has a built-in microcomputer, performs arithmetic processing based on signals from the various sensors described above, and an injector 17 and an ignition coil provided for each cylinder of the engine 10. 19 operation is controlled.

  The ECU 70 has a ROM that stores various control programs. In the ROM, as various control programs, the fuel injection amount is calculated in accordance with the operating state of the engine 10 and the fuel injection control processing program for executing the fuel cut (F / C) processing, and the operating state of the engine 10 are set. Accordingly, an ignition timing control processing program for calculating the ignition timing and advancing or retarding the ignition timing is stored.

  Next, an example of a control routine for the F / C process and the ignition timing retarding control process before the F / C process in the present embodiment configured as described above will be described with reference to the flowchart of FIG. Note that this control routine is executed in synchronization with the ignition cycle, for example, every 60 ° crank angle before top dead center.

First, when the control is started, it is determined in step S201 whether an F / C processing condition is satisfied. That is, it is determined whether or not the engine 10 (vehicle) is in a deceleration state. Specifically, whether or not the throttle opening detected by the throttle position sensor 45 is fully closed (= 0 °), and the engine speed NE detected by the engine speed sensor 41 is a predetermined speed. It is determined whether or not the engine speed is equal to or higher than a certain F / C engine speed N _CUT . Here, F / C engine speed N _CUT is a threshold value for determining whether the engine 10 is in the F / C process executable engine rotational speed NE, the engine speed NE F / When the engine speed N _CUT or higher and the throttle opening is 0 °, the engine 10 can execute the F / C process, that is, the F / C process condition is satisfied. Become. In the case where the transmission is provided with a fluid transmission device such as a torque converter, it is preferable to add whether or not a lockup clutch in the torque converter is engaged as a determination factor. The driving force transmitted from the drive wheel is low in transmission efficiency to be transmitted to the engine via the torque converter, and if the F / C processing is executed in a state where the lockup clutch is not engaged, the engine speed NE This is because it may decrease quickly and cause an engine stall. When the F / C processing condition is not satisfied, this routine is terminated.

  On the other hand, if it is determined that the F / C processing condition is satisfied, the process proceeds to step S202, and it is determined whether or not the ignition timing retardation control execution condition before F / C is satisfied. The ignition timing retardation control execution condition may be, for example, whether or not a predetermined time Td (for example, several tens of ms) has elapsed since it is determined that the above deceleration state has been reached. This predetermined time Td is immediately retarded because the air existing in the intake passage 20 including the surge tank 27 downstream of the throttle valve 26 is supplied to the engine 10 immediately after the throttle opening becomes 0 °. It is set to avoid torque steps that can sometimes occur. If it is determined that the pre-F / C retard angle control execution condition is satisfied, the process proceeds to step S203, and if not, the routine is temporarily terminated.

  In step S203, it is determined whether or not this routine cycle is the first time. The process proceeds to step S204 only when it is the first time, and the process proceeds to step S205 otherwise.

Therefore, in step S204, the ignition timing eabfc is set to a base value (for example, 20 ° CA before top dead center) when the throttle valve 26 is fully closed, and the process proceeds again to step S205 via step S203. In step S205, a deceleration is obtained. That is, in a subroutine executed every predetermined time (for example, 16 ms), the deceleration edlnosm calculated by, for example, the amount of change in the rotational speed of the output shaft of the automatic transmission is detected by the output shaft rotational speed sensor 49. Used. The deceleration edlnosm is calculated by the difference between the output shaft rotational speed N _{i + 1,} which is detected by the detected output shaft rotational speed N _i and the routine cycles at the previous routine cycle, the previous output shaft speed When the difference between _Ni and the current output shaft rotational speed _{Ni + 1} is large, it means that the deceleration is large. For example, the deceleration X when the difference is 5rpm the output shaft rotational speed N _{i + 1} of the current and the output shaft rotational speed N _i of the previous and the time of 10rpm and deceleration Y, the Y> X. Note that the deceleration described above is obtained based on the detected value by the acceleration / deceleration sensor provided in the vehicle or the brake master pressure, in addition to the change amount of the output shaft rotation speed detected by the output shaft rotation speed sensor 49. It may be.

  Next, in step S206, the F / C pre-retard angle update amount edlabfc is obtained from the map from the deceleration calculated as described above and the engine speed NE. This F / C pre-retard angle update amount edlabfc is a value obtained in advance by experiments or the like and stored in the map. For example, when the engine speed NE is 4000 rpm and the deceleration is X as described above, edlabfc = a In the case of ° CA (crank angle) and Y, edlabfc = b ° CA, where b> a. Further, when the engine speed NE is 2400 rpm and the deceleration is X as described above, it is 1.1a ° CA and when it is Y, it is 1.2b ° CA. Depending on the magnitude of the deceleration, before the F / C By changing the magnitude of the retard update amount edlabfc, the ignition timing retard update speed, which is the update retard amount per predetermined unit time, is changed. These relationships are shown in the figure as a map in FIG.

  In the next step S207, the ignition timing eabfc is updated for each routine cycle with the pre-F / C retard angle update amount edlabfc obtained in step S206. Specifically, the current ignition timing eabfc is set by subtracting the F / C pre-retard angle update amount edlabfc from the previous ignition timing eabfc.

Then, the process proceeds to step S208, where it is determined whether or not the current ignition timing eabfc has reached the F / C permission ignition timing, and the process returns to the above step S202 unless the F / C permission ignition timing is reached. The routine cycle is repeated. On the other hand, when the F / C permission ignition timing is reached, the routine proceeds to step S209, where F / C is instructed, and fuel cut is actually executed. When the engine speed NE reaches the F / C return rotation speed _NRTN after the start of fuel cut execution, the F / C process is stopped and normal fuel injection control is performed as is well known.

  Here, in the above-described embodiment, the steps S201 to S209 correspond to the fuel cut means, and the steps S202 to S208 correspond to the fuel cut delay means. Step S205 corresponds to deceleration determination means, and steps S206 and S207 correspond to ignition timing update retarding means before fuel cut and ignition timing retard update speed changing means.

Next, the operation in the present embodiment will be further described with reference to the time chart of FIG. As shown in the time chart of FIG. 4, at time T ₀ , the throttle opening is fully closed by the detection of the throttle position sensor 45, and the engine speed NE detected by the engine speed sensor 41 is the F / C engine. If the F / C processing condition equal to or greater than the rotational speed N _CUT is satisfied, the pre-F / C retard angle control is started at time T ₁ after a predetermined time Td. This F / C pre-retarding angle control is typically illustrated by a broken line when the deceleration is small X and a solid line when the deceleration is large Y, respectively.

When the deceleration is small X, the ignition timing retard update speed is relatively slow, and the retard amount gradually accumulates and increases over time as in the conventional case, and the ignition timing becomes F / C possible ignition timing. fuel cut is started at time T _X which has reached the. This fuel cut state continues until time T _EX when the engine speed NE reaches the F / C return speed N _RTN . Thus, when the deceleration is small X, as shown by F / C (X) in FIG. 4, in the period F / C (X) from time T _X to time T _EX , the fuel cut time is can get.

On the other hand, when the deceleration is large Y, the ignition timing retard update speed is relatively fast, is increased retard amount is rapidly with time, the ignition timing at time T _Y having reached the F / C can ignition timing Fuel cut is started. This fuel cut state is continued until time T _EY when the engine speed NE reaches the F / C return speed N _RTN . Thus, even when the deceleration is large Y, as shown in FIGS. 4 F / C (Y), the period from the time _{T Y} to time _{T EY F / C (Y)} , the fuel cut time can get.

Now, when the deceleration is large Y, a predetermined delay time is ensured regardless of the effect of this embodiment and the magnitude of the deceleration in the prior art (ignition timing retard update speed is set to a predetermined value). This will be explained in comparison with the action of the above. Here, assuming that the ignition timing retard update speed of the prior art is equal to the ignition timing retard update speed when the deceleration according to the present embodiment is small X, in the prior art, regardless of the magnitude of the deceleration, so that the fuel cut is started at time T _X. When the deceleration is small, the fuel cut time is obtained in the period F / C (X) up to the time T _EX , but when the deceleration is large, the F / C return rotational speed of the engine speed NE is obtained. Since the arrival at _NRTN is fast, the process is terminated at time _TEY . Thus, in the illustrated example, at time T _X period from to time T _EY F / C (P) only, only the fuel cut time is obtained.

In contrast, according to this embodiment, when the deceleration is large, the ignition timing delay update rate in accordance with which it is fast, the start of fuel cut is earlier from the time T _X at time T _Y, the fuel cut duration is ensured longer from the time T _Y to time T _EY. Thus, the fuel consumption is improved.

1 is a system configuration diagram showing a fuel cut control device for an internal combustion engine according to the present invention. It is a flowchart which shows an example of the control routine about the ignition timing retardation control process before F / C processing and F / C processing in embodiment of this invention. In the embodiment of the present invention, it is a map in which the F / C pre-retard angle update amount (edlabfc) set based on the deceleration and the engine speed is stored. It is a time chart for demonstrating the effect | action of embodiment of this invention by contrast with a prior art.

Explanation of symbols

10 Internal combustion engine
16 Spark plug 17 Injector 19 Ignition coil 26 Throttle valve 45 Throttle position sensor 49 Output shaft rotational speed sensor 70 ECU

Claims (2)

Fuel cutting means for cutting fuel to the engine under predetermined deceleration operation conditions;
Fuel cut delay means for delaying start of fuel cut by the fuel cut means from establishment of a predetermined deceleration operation condition;
In an internal combustion engine comprising: a fuel cut pre-cut ignition timing update retarding means for retarding while updating the ignition timing during a fuel cut start delay by the fuel cut delay means,
Deceleration determining means for determining the magnitude of deceleration of the engine or vehicle;
An ignition timing retard update speed changing means for changing an ignition timing retard update speed in the pre-fuel cut ignition timing update retard means in accordance with the magnitude of the deceleration by the deceleration determination means;
A fuel cut control device for an internal combustion engine, comprising: 2. The fuel cut control device for an internal combustion engine according to claim 1, wherein the ignition timing retard angle update speed changing means increases the ignition timing retard angle update speed when the deceleration is large.

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