JP3800082B2 - Fuel cut control device for internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fuel cut control device for an internal combustion engine, and more particularly to a technique for reducing the occurrence of shock due to fuel cut.
[0002]
[Prior art]
Generally, in an internal combustion engine, in order to improve fuel efficiency, the engine is triggered by a predetermined deceleration operation condition, specifically, when the throttle valve is substantially fully closed and the engine speed is higher than a predetermined fuel cut speed. However, the fuel cut causes a torque step and generates a shock.
[0003]
Therefore, in the technique described in Japanese Patent Application Laid-Open No. 10-30477, the ignition timing is retarded prior to the fuel cut. Specifically, the start of the fuel cut is established for a predetermined time from the establishment of a predetermined deceleration operation condition. By delaying the ignition timing during the delay time, the torque is effectively reduced prior to the fuel cut, thereby reducing the torque step at the time of the fuel cut transition and reducing the shock. The generation is prevented.
[0004]
[Problems to be solved by the invention]
However, in the prior art, the torque reduction before the fuel cut is performed by retarding the ignition timing, so that during the retard control of the ignition timing, the fuel consumption performance deteriorates due to the ignition timing being separated from the MBT. There was a problem.
In view of such a conventional problem, the present invention can devise a torque reduction method before fuel cut, that is, can arbitrarily control the opening / closing operation of two intake valves provided in each cylinder. It is an object of the present invention to further improve fuel efficiency and reduce torque shock by cutting fuel by using a variable valve gear.
[0005]
[Means for Solving the Problems]
Therefore, according to the first aspect of the present invention, there is provided a variable valve gear that can arbitrarily control the opening / closing operation of two intake valves provided for each cylinder, and fuel to the engine under predetermined deceleration operation conditions. In an internal combustion engine having a fuel cut means for performing fuel cut for stopping supply, a fuel cut delay means for delaying a start of fuel cut by the fuel cut means for a predetermined time from the establishment of the predetermined deceleration operation condition, and the fuel cut during the delay time, performs a stop one intake valve for stopping the operation of either one of the intake valves in a closed state, and an intake piece valve stopping means for increasing the number of cylinders which performs intake piece valve stop with the passage of time , characterized in that the provided.
[0006]
According to a second aspect of the present invention, the fuel cut delay means performs a fuel cut after a lapse of a first predetermined time from the establishment of the predetermined deceleration operation condition, and the intake single valve stop means In this case, the intake single valve is stopped after the elapse of a second predetermined time shorter than the first predetermined time from the establishment of the deceleration operation condition.
The invention according to claim 3 is characterized in that the first and second predetermined times are set to be shorter on the high rotation side than on the low rotation side, respectively, according to the engine speed.
[0007]
According to a fourth aspect of the present invention, the intake single valve stop means increases the number of cylinders that perform the single intake valve stop every third predetermined time by one cylinder or one group cylinder.
The invention according to claim 5 is characterized in that the third predetermined time is set to be shorter on the high rotation side than on the low rotation side in accordance with the engine speed.
According to a sixth aspect of the present invention, during the fuel cut, all the intake valves of the cylinders during the fuel cut are held in a closed state.
According to a seventh aspect of the present invention, the intake single valve stop means alternately switches the intake valve that stops the single valve every cycle in each cylinder.
[0008]
【The invention's effect】
According to the first aspect of the invention, the torque shock at the time of fuel cut can be relieved by stopping the intake single valve prior to the fuel cut.
Further, the delay of the fuel cut, not only waiting the torque decreases at a fully closed state of the throttle valve, have rows stop one intake valve during the delay time, and the number of cylinders which performs stop one intake valve Time By increasing the torque with the passage of time and reducing the torque more effectively, the torque step at the time of the fuel cut transition can be reduced and the occurrence of shock can be prevented.
[0009]
In particular , according to the invention of claim 2 , after the predetermined deceleration operation condition is established, the intake single valve is stopped after the second predetermined time, and the fuel cut is performed after the first predetermined time (> second predetermined time). By delaying the intake single valve stop during the fuel cut delay time, the torque decrease in the fully closed state of the throttle valve becomes relatively gradual, and then the intake single valve stop is performed. By compensating for the decrease in torque, the torque can be reduced more smoothly.
[0010]
In particular , according to the fourth aspect of the present invention, when the intake single valve is stopped, the torque is gradually decreased by increasing the number of cylinders that stop the intake single valve every third predetermined time by one cylinder or one group cylinder. Thus, it is possible to prevent the occurrence of shock due to the intake single valve stop.
In particular , according to the invention of claim 6 , during the fuel cut, all the intake valves of the cylinders during the fuel cut are held in the closed state so that the intake air on the side that has been injected before the fuel cut and stopped one-way. It is possible to prevent the fuel accumulated on the upstream side of the valve from flowing into the combustion chamber and discharging it as raw gas, thereby deteriorating the exhaust performance.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a system diagram of an internal combustion engine (hereinafter referred to as an engine) showing an embodiment of the present invention, and FIG. 2 is a schematic plan view of a main part of the engine.
The combustion chamber 3 defined by the piston 2 of each cylinder of the engine 1 is provided with two electromagnetically driven intake valves 5A and 5B and exhaust valves 6A and 6B so as to surround the spark plug 4. . 7 is an intake passage and 8 is an exhaust passage.
[0012]
FIG. 3 shows the basic structure of the electromagnetic drive devices (variable valve operating devices) for the intake valves 5A and 5B and the exhaust valves 6A and 6B. A plate-like movable element 22 is attached to the valve shaft 21 of the valve body 20, and the movable element 22 is biased to a neutral position by springs 23 and 24. A valve opening electromagnetic coil 25 is disposed below the mover 22, and a valve closing electromagnetic coil 26 is disposed above the movable element 22.
[0013]
Therefore, when opening the valve, after energization of the upper valve closing electromagnetic coil 26 is stopped, by energizing the lower valve opening electromagnetic coil 25 and attracting the mover 22 downward, The valve body 20 is lifted and opened. Conversely, when closing the valve, by energizing the lower valve opening electromagnetic coil 25 and then energizing the upper valve closing electromagnetic coil 26 to attract the mover 22 upward, The valve body 20 is seated on the seat portion and closed.
[0014]
Returning to FIG. 1, an electric throttle valve 9 is provided in the intake passage 7 upstream of the intake manifold.
The intake passage 7 is also provided with an electromagnetic fuel injection valve 10 for each cylinder at each branch portion (position facing the intake port on the cylinder head side) of the intake manifold.
[0015]
As shown in FIG. 2, the fuel injection valve 10 is a two-hole type injecting fuel in two directions and is located at the upstream side collecting portion of the Siamese-type intake ports P1 and P2, and each intake valve 5A, Fuel is injected toward 5B.
Here, the operations of the intake valves 5A and 5B, the exhaust valves 6A and 6B, the electric throttle valve 9, the fuel injection valve 10 and the spark plug 4 are controlled by the control unit 11, and the control unit 11 is provided for engine rotation. A crank angle sensor 12 that outputs a crank angle signal in synchronism and detects the engine speed Ne together with the crank angle position, an accelerator pedal sensor 13 that detects an accelerator opening (accelerator pedal depression amount) APO, and an intake passage 7 Signals are input from an air flow meter 14 for detecting the intake air amount Qa upstream of the throttle valve 9, a throttle sensor 15 for detecting the opening TVO of the throttle valve 9, a water temperature sensor 16 for detecting the engine coolant temperature Tw, and the like. . The accelerator pedal sensor 13 or the throttle sensor 15 is provided with an idle switch that is turned on at the accelerator or throttle fully closed position, and the switch signal is also input.
[0016]
Regarding the control of the fuel injection of the fuel injection valve 10 by the control unit 11, the basic fuel injection amount Tp = K · Qa / Ne (K is a constant) is calculated based on the intake air amount Qa and the engine speed Ne. The final fuel injection amount Ti = Tp · COEF (COFF is various correction coefficients) is determined by applying various corrections to the cylinder, and each cylinder is driven at a predetermined timing synchronized with the engine rotation of a drive pulse signal having a pulse width corresponding to Ti. Is output to the fuel injection valve 10 for fuel injection.
[0017]
However, when a fuel cut command (FC = 1) is issued by a fuel cut control routine of FIG. 4 to be described later, output of the drive pulse signal to the fuel injection valve 10 is stopped and fuel cut is performed.
Prior to this fuel cut, an intake piece that stops the operation of one of the two intake valves 5A, 5B in a closed state so that the engine is operated with only one intake valve. Stop the valve (also called single valve operation).
[0018]
Next, the fuel cut control routine including the intake single valve stop of FIG. 4 will be described. This routine is executed every predetermined time (ΔT).
In step 1 (denoted as S1 in the figure, the same applies hereinafter), it is determined whether or not the fuel is being cut (fuel cut flag FC = 1).
When the fuel cut is not in progress (when FC = 0), the idle switch is turned on in step 2 (accelerator or throttle full throttle) to determine whether or not a predetermined deceleration operation condition (hereinafter referred to as fuel cut condition) to be cut. In step 3, it is determined whether or not the engine speed Ne is equal to or higher than a predetermined fuel cut speed Nfc. In addition, although it is normal that the water temperature Tw is equal to or higher than a predetermined value, it is omitted in this flow.
[0019]
If these conditions are not satisfied, the fuel cut is not performed, so the routine proceeds to step 4, the timers TM1 and TM2 are set to 0, and this routine is terminated.
When these conditions are satisfied, that is, when the idle switch is ON (accelerator or throttle fully closed) and the engine speed Ne is equal to or higher than the predetermined fuel cut speed Nfc, the deceleration operation condition for fuel cut is satisfied. Therefore, the process proceeds to step 5 and subsequent steps.
[0020]
In step 5, the first predetermined time (fuel cut delay time) T1, the second predetermined time (intake single valve stop delay time) T2, and the third predetermined time are set according to the current engine speed Ne level. Time (execution interval for each cylinder in which the intake valve is stopped) T3 is set. However, this setting is made only for the first time immediately after the fuel cut condition is established.
Here, the first predetermined time T1 sets a fuel cut delay time from the establishment of the fuel cut condition, and is set to be shorter on the high speed side depending on the engine speed Ne. At low speeds and high speeds, the torque decreases more rapidly after the throttle valve is fully closed at high speeds. Therefore, on the high speed side, the first predetermined time (delay of fuel cut) This is because the fuel consumption is improved by shortening T1 and shortening the fuel cut.
[0021]
Further, the second predetermined time T2 sets a delay time for stopping the intake single valve from the establishment of the fuel cut condition when the intake single valve is stopped prior to the fuel cut, and T2 <T1 is assumed. This is also set to be shorter on the high rotation side depending on the engine speed Ne. Regardless of the change in the fuel cut delay time, the time (T1-T2) from the start of the intake single valve stop to the start of the fuel cut, that is, the time during which the intake single valve is stopped is secured, and the effect of the intake single valve stop This is to ensure Although the setting of the third predetermined time T3 will be described later, basically, T3 <T1-T2.
[0022]
In step 6, the value of the timer TM1 is increased by the execution time interval ΔT of this routine (TM1 = TM1 + ΔT) to measure the delay time after the fuel cut is established.
In step 7, the value of the timer TM1 is compared with the second predetermined time T2, and this routine is terminated while TM1 <T2.
When TM1 ≧ T2 (that is, when the second predetermined time T2 has elapsed since the fuel cut condition is satisfied), the routine proceeds to step 8 and subsequent steps to stop the intake single valve.
[0023]
In step 8, the timer TM2 is decreased by the execution time interval ΔT of this routine (TM2 = TM2−) in order to measure the time interval when increasing the number of cylinders for each cylinder (or for each group of cylinders) that stop the intake single valve. ΔT).
In Step 9, the value of the timer TM2 is compared with 0. Since TM2 ≦ 0 at first, the process proceeds to Step 10.
[0024]
In step 10, the cylinder (or cylinder group) in which the intake single valve is stopped is determined, and in the next step 11, the intake single valve of the cylinder is stopped.
In step 12, the value of T3 is substituted for timer TM2 (TM2 = T3).
Therefore, after the intake one valve of one cylinder (or one group cylinder) is stopped, the timer TM2 = T3 and TM2 = TM2-ΔT is set in step 8 in the routine after the next time, so TM2 = 0. When the third predetermined time T3 has elapsed since the intake single valve of one cylinder (or one group cylinder) has stopped, the process proceeds from step 9 to steps 10 and 11, and the next cylinder (or next group) Cylinder) is stopped.
[0025]
In step 13, the value of the timer TM1 is compared with the first predetermined time T1, and this routine is terminated while TM1 <T1. During this time, the intake single valve stop gradually proceeds.
When TM1 ≧ T1 (that is, when the first predetermined time T1 elapses from the establishment of the fuel cut condition), the routine proceeds to step 14 and thereafter in order to start the fuel cut.
[0026]
In step 14, the fuel cut flag FC = 1 is set and fuel cut is performed. The fuel cut here may be performed for all cylinders or only for some cylinders. At the same time as the start of the fuel cut, for the cylinder where the fuel was cut, the intake single valve stop is terminated and all the intake valves are held in the closed state.
In step 15, the timers TM1 and TM2 are set to 0, and this routine is terminated.
[0027]
After the start of the fuel cut, the determination in step 1 is FC = 1, so the process proceeds to steps 16 and 17 to determine whether or not the fuel cut release condition is satisfied.
That is, it is determined in step 16 whether or not the idle switch is OFF (accelerator pedal is depressed), and in step 17 it is determined whether or not the engine speed Ne is equal to or lower than a predetermined recovery speed Nre.
[0028]
If none of these conditions is satisfied, the fuel cut is continued, and this routine is terminated.
If any one of these conditions is satisfied, the routine proceeds to step 18 to cancel the fuel cut.
In step 18, the fuel cut flag FC = 0 is set, and fuel supply is resumed (fuel recovery). It goes without saying that the normal operation (double valve operation) is performed on the intake valve from this time.
[0029]
In this embodiment, the steps 2, 3, and 14 correspond to the fuel cut means, and the step 13 corresponds to the fuel cut delay means. Steps 10 and 11 correspond to intake single valve stop means.
Next, the operation in this embodiment will be described with reference to the time chart of FIG. As shown in FIG. 5, during the fuel cut delay time T <b> 1 after the fuel cut condition is satisfied, the torque decreases as the boost decreases in the throttle valve fully closed state.
[0030]
Then, after the fuel cut condition is satisfied, the intake single valve stop is started after the second predetermined time T2, and the intake single valve stop cylinder is gradually increased as time elapses.
Here, if the intake valve is stopped at the same time as when the throttle valve is fully closed, a shock may occur at that time, and immediately after the throttle valve is fully closed, the torque decreases relatively greatly, Since the subsequent torque decrease is relatively gradual, the intake single valve is not stopped while the torque is relatively large, and the intake single valve stop is started from the point when the torque decrease is relatively gradual. Reduce torque smoothly and sufficiently.
[0031]
The method of stopping the intake single valve here is as follows.
Cylinders (or cylinder groups) that reach the intake stroke at the first time after the passage of the second predetermined time T2 after the fuel cut condition is satisfied (or that are in the exhaust stroke at the time T2 has elapsed) are determined, and the determined cylinder (or cylinder) Start the intake single valve stop from the group.
Whether the intake single valve stop for each cylinder (sequential stop) or the single intake valve stop (group stop) for each cylinder group is determined by the strength of the torque reduction request. When required (in the case of high rotation), the group is stopped, and in the case of a relatively slow torque reduction request (in the case of low rotation), the sequential stop is performed.
[0032]
In addition, in the intake single valve stop, in each cylinder, an intake valve that stops one valve every cycle is alternately switched (intake single valve alternate stop). That is, when the intake valve 5A is stopped in the first cycle, the intake valve 5B is stopped in the next cycle, and thereafter, the intake valve that stops one valve every cycle is alternately switched.
By such an intake single valve alternate stop, the air-fuel ratio can be made lean as follows.
[0033]
Assuming a two-way fuel injection valve that injects fuel toward each of the two intake valves, the fuel injected into the intake valve on the stop side is It is not sucked into the cylinder in the intake stroke and remains as a wall flow (may be present near the intake port in the vaporized state). When the remaining fuel shifts from stop to movable in the next cycle, the remaining fuel is combined with the newly injected fuel and is sucked into the cylinder or becomes a wall flow. At this time, the reverse intake valve is stopped and similarly not sucked into the cylinder.
[0034]
As a result, the air-fuel ratio lean occurs for a while after the intake single valve stop starts. However, if the cylinder intake air amount and the fuel injection amount are constant, the fuel carried forward by repeated stop and move is sucked into the cylinder. Therefore, the amount of fuel injected and the amount of injected fuel reach an equilibrium state, so that the air-fuel ratio almost before the stop of the intake single valve stop is restored.
Therefore, by increasing the number of cylinders that stop the intake single valve by one cylinder (or by one group of cylinders) every third predetermined time T3, the air-fuel ratio can be gradually made lean and the torque can be reduced.
[0035]
Accordingly, the third predetermined time T3, which is the time interval for each cylinder where the intake single valve is stopped, is set as follows.
After the air-fuel ratio of the cylinder becomes lean when the one-cylinder intake valve is stopped in a certain cylinder, the air-fuel ratio returns to the original air-fuel ratio for a predetermined time. If this time is TL, T3 is the time required for one stroke to TL Set between.
[0036]
Also, T3 is set shorter on the high rotation side depending on the engine speed. On the high speed side, it is better to reduce the torque by leaning rapidly as much as the torque decreases in a shorter time after the fuel cut condition is satisfied, so set T3 short (close to the time required for one stroke). Since it is desired to drop the torque more smoothly as the engine speed is lower, T3 is set longer in a range (<TL) in which the torque reduction effect by the air-fuel ratio lean can be obtained.
[0037]
After execution of such an intake single valve stop, when the first predetermined time T1 elapses from the establishment of the fuel cut condition, the fuel cut is started.
The torque step at the time of shifting to the fuel cut is smaller than that without the intake single valve stop control, so that the torque shock due to the fuel cut can be reduced.
[0038]
During this fuel cut, all the intake valves of the cylinders that are in the fuel cut state are kept closed, so that the fuel that has been injected before the fuel cut and accumulated on the upstream side of the intake valve that has been stopped one-way Flows into the combustion chamber and is discharged as raw gas to prevent the exhaust performance from deteriorating.
In the present invention, since the intake single valve is stopped prior to the fuel cut, the power consumption can be reduced by stopping the intake single valve when the electromagnetic variable valve operating device is used. In the electromagnetic variable valve operating apparatus according to the present embodiment, it is necessary to energize the valve closing electromagnetic coil 26 in FIG. 3 in order to hold the stop intake valve in the closed state when the single valve is stopped. Since the holding current for maintaining the valve closed state is extremely small as compared with the operation current required for the valve opening or closing operation, the power consumption can be greatly reduced.
[Brief description of the drawings]
FIG. 1 is a system diagram of an engine showing an embodiment of the present invention. FIG. 2 is a schematic plan view of an essential part of the engine. FIG. 3 is a basic structural diagram of an electromagnetic drive device for intake valves and exhaust valves. Flowchart of fuel cut control routine including single valve stop [Fig. 5] Time chart at the time of fuel cut transition [Explanation of symbols]
1 Engine 3 Combustion chamber 4 Spark plugs 5A, 5B Electromagnetically driven intake valves 6A, 6B Electromagnetically driven exhaust valve 9 Electric throttle valve 10 Two-way fuel injection valve 11 Control unit 12 Crank angle sensor 13 Accelerator pedal sensor 14 Air flow Meter 15 Throttle sensor

Claims (7)

Fuel cut that has a variable valve system that can arbitrarily control the opening / closing operation of two intake valves provided for each cylinder, and that performs fuel cut to stop fuel supply to the engine under predetermined deceleration operating conditions In an internal combustion engine having means,
Fuel cut delay means for delaying the start of fuel cut by the fuel cut means for a predetermined time from the establishment of the predetermined deceleration operation condition;
During the fuel cut delay time, an intake piece that stops the operation of one of the intake valves in a closed state , and increases the number of cylinders that perform the stop of the intake valve as time elapses. Valve stop means ;
A fuel cut control device for an internal combustion engine, comprising: The fuel cut delay means performs fuel cut after the first predetermined time has elapsed since the establishment of the predetermined deceleration operation condition.
The intake piece valve stopping means, the establishment of the predetermined decelerating condition, the the first after a short second predetermined time than the predetermined time, according to claim 1, characterized in that the stop one intake valve A fuel cut control device for an internal combustion engine. 3. The fuel cut of the internal combustion engine according to claim 2, wherein the first and second predetermined times are set to be shorter on the high rotation side than on the low rotation side, respectively, according to the engine speed. Control device.   The intake single valve stop means increases the number of cylinders that stop the intake single valve every third predetermined time by one cylinder or one group cylinder. A fuel cut control device for an internal combustion engine according to claim 1. 5. The fuel cut control device for an internal combustion engine according to claim 4, wherein the third predetermined time is set to be shorter on the high rotation side than on the low rotation side according to the engine speed. The fuel cut control device for an internal combustion engine according to any one of claims 1 to 5 , wherein all of the intake valves of the cylinders during the fuel cut are kept closed during the fuel cut. The fuel for an internal combustion engine according to any one of claims 1 to 6, wherein the intake single valve stop means alternately switches an intake valve that stops one valve every cycle in each cylinder. Cut control device.

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