JP3966216B2 - Fuel injection control device for internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fuel injection control device for an internal combustion engine, and more particularly to a fuel injection control device for suitably controlling a fuel injection amount or fuel injection timing in a period from the beginning of engine startup to a complete explosion.
[0002]
[Prior art]
When the internal combustion engine is started at a low temperature, the fuel injection amount is usually warmed up during the period from the start of cranking to the complete explosion. This warm-up increase is performed in order to compensate for fuel adhering to the port or cylinder wall surface and insufficient fuel vaporization. For example, an increase correction coefficient is set in accordance with the temperature of the cooling water temperature when the engine is started.
[0003]
[Problems to be solved by the invention]
However, here, there is a desire to quickly increase the engine speed during the period until the internal combustion engine reaches the complete explosion. On the other hand, in the existing technology, the desired vaporized fuel cannot be introduced into the cylinder mainly due to fuel adhesion (port wet) to the port wall surface, resulting in poor combustion such as misfire. For this reason, combustion immediately after the start of the internal combustion engine becomes unstable, resulting in inconveniences such as an increase in the rotational speed until the complete explosion is delayed or the ride comfort (starting feeling) of the vehicle is deteriorated.
[0004]
The present invention has been made paying attention to the above-mentioned problems, and an object of the present invention is to provide a fuel injection control device for an internal combustion engine that can improve the startability of the internal combustion engine.
[0005]
[Means for Solving the Problems]
  In order to achieve the above object, according to the first aspect of the present invention, the starting injection amount calculating means calculates the starting injection amount of the next combustion cylinder when the internal combustion engine is in the starting state before the complete explosion. To do. When the internal combustion engine is in the starting state before the complete explosion,Accompanying the first explosionPredict the increase in engine speed due to combustion. The valve closing injection amount calculating means calculates a fuel amount injected when the intake valve is closed, out of the starting injection amount, based on the predicted increase in engine speed. The injection amount correction means corrects the start-up injection amount by an increase based on the calculated injection amount when the intake valve is closed.
[0006]
By shifting the injection timing to the retarded side from the normal fuel injection timing under the start-up state before the complete explosion, fuel injection synchronized with the intake stroke (intake valve opening timing) can be performed even in the minute rotation range. Can be implemented. Therefore, the amount of wet fuel can be reduced, and a desired combustion torque can be obtained. As a result, when the engine is started, the rotational speed can be increased quickly and stably, and as a result, the startability of the internal combustion engine can be improved.
[0007]
However, when the intake stroke synchronous injection is performed, the fuel injection amount that becomes the injection outside the intake stroke, that is, the fuel injected at the time of closing immediately before the intake valve is opened does not flow into the cylinder on the intake flow, It adheres to the port wall surface as a port wet before flowing into the cylinder. Therefore, when the engine speed starts and the engine speed suddenly increases with the first explosion, if the fuel injection by the injector takes place when the intake valve is closed (the period before the intake stroke), it will be The amount of fuel flowing into the cylinder is insufficient, which adversely affects engine startability.
[0008]
On the other hand, according to the above configuration, the fuel injection amount that is the injection when the intake valve is closed is accurately grasped according to the increase in the engine speed, and the start-up injection amount is corrected to increase according to the injection amount. To do. Therefore, the shortage of fuel due to the wetness of the intake valve closing injection is solved, and as a result, the startability of the internal combustion engine can be improved.
[0009]
Incidentally, in this specification, “complete explosion” means a state in which the internal combustion engine can maintain its rotation by itself after application of initial rotation by a starter motor or the like when starting the engine.
[0010]
In the first aspect of the invention, as described in claim 2, the injection amount correction value is obtained based on the in-cylinder inflow rate of the intake valve opening-time injection and the intake valve closing-time injection. The injection amount at start-up may be corrected using the injection amount correction value. That is, when the in-cylinder inflow rate of the injected fuel when the intake valve is opened is compared with the inflow rate of the injected fuel when the intake valve is closed, the latter is considerably smaller (see FIG. 19). This is considered to be caused by a difference in the amount of fuel remaining in the intake port as a port wet. In such a case, it is possible to perform more appropriate fuel injection by giving an injection amount correction value in consideration of this in-cylinder inflow rate.
[0011]
Since the fuel injection amount when the intake valve is closed remains in the intake port as wet, it is conceivable to evaporate the fuel adhering to the wall of the port after fuel injection in order to flow this fuel wet into the cylinder. . Therefore, in the invention according to claim 3, the fuel amount obtained by adding the calculated fuel injection amount at the time of closing the intake valve and the corrected injection amount corresponding to the injection amount at the time of closing the valve is calculated as the intake amount of the combustion cylinder at that time. The fuel is divided and injected at a timing earlier than the stroke. As a result, the fuel divided and injected at a timing prior to the intake stroke of the combustion cylinder once adheres to the wall surface of the port, but gradually evaporates during the period up to the intake stroke, and then in the cylinder as the intake valve opens. Is flowed into. This configuration also solves the shortage of fuel that should flow in. As a result, the fuel can be efficiently flowed into the cylinder and the engine startability can be improved.
[0012]
  According to the fourth aspect of the present invention, the fuel injection timing is corrected based on the predicted increase in the engine speed so that the end of the fuel injection at start-up is not later than the closing timing of the intake valve (fuel injection timing). Correction means). If fuel injection by the injector takes place after the intake stroke, the amount of fuel inflow into the cylinder will be reduced by that amount, but the above problem can be avoided by correcting the fuel injection timing according to the increase in engine speed. .In the invention according to claim 5, the fuel injection timing is not corrected at the time of fuel injection from the start of cranking to the first explosion. During this period, the injection timing correction is prohibited because it is not affected by the increase in rotation due to combustion. Thereby, unnecessary correction processing can be omitted.
[0013]
  Claim6In the invention described in (1), the rotation increase predicting means predicts an increase in the engine speed from the number of injections from the start of the engine and the engine temperature. In this case, the influence of friction (sliding friction) is reflected in the rotation speed prediction, and the increase in the rotation speed can be accurately predicted. As the engine temperature, the temperature of engine cooling water, the temperature of the cylinder wall surface, or the like can be applied.
[0014]
  Claim7In the invention described inFrom the start of cranking to the first explosionDuring fuel injection,The fuel injection amount is not corrected. During this period, the injection amount correction is prohibited because the rotation is not affected by the combustion. Thereby, unnecessary correction processing can be omitted.
[0015]
  Claim8According to the invention described above, there is provided means for counting the number of combustion cycles from the start of engine starting when all the cylinders of the internal combustion engine are combusted as one cycle, and the starting injection amount calculating means includes the internal combustion engine The starting injection amount is calculated based on the number of combustion cycles from the start of starting. In fact, the claim9As described above, the injection amount may be reduced as the number of combustion cycles increases.
[0016]
That is, at the beginning of engine startup, the fuel injection amount is increased in consideration of the fuel wet amount. However, the fuel wet approaches the saturation point each time the combustion cycle is repeated, and the fuel injection amount gradually becomes unnecessary. Therefore, as the number of combustion cycles increases, the injection amount is reduced to suppress excessive fuel injection.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
(First embodiment)
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings.
[0018]
The fuel injection control apparatus according to the present embodiment is a system that controls fuel injection to an engine by an electronic control unit (hereinafter referred to as ECU) mainly composed of a well-known microcomputer, and in particular, fuel injection timing at engine start-up. It is related with the apparatus which controls appropriately. First, with reference to FIG. 1, the structure of the apparatus of this Embodiment and the internal combustion engine to which the apparatus is applied will be described.
[0019]
The engine 10 is a four-cylinder spark ignition type internal combustion engine having four cylinders of first to fourth (# 1 to # 4), and the combustion order is # 1 → # 3 → # 4 → # 2. Yes. Each cylinder is provided with an injector 1 as shown. Fuel pumped from a fuel supply system (not shown) is distributed and supplied to the injectors 1 of the respective cylinders through the delivery pipe 2. When the injector 1 is valve-opened for a time corresponding to the fuel injection amount commanded by the ECU 30, fuel is injected and supplied to the intake ports 3 of the corresponding cylinders.
[0020]
On the other hand, the fuel injected and supplied by the injector 1 is mixed with the air sucked through the air cleaner 12, the throttle valve 14 and the surge tank 15 provided in the intake pipe 11 of the engine 10. This air-fuel mixture is introduced into the combustion chamber 18 in the cylinder 17 via the intake valve 16.
[0021]
Here, the throttle valve 14 is a valve that adjusts the amount of air taken into the intake pipe 11 and mixed with the injected fuel, for example, in conjunction with an accelerator pedal (not shown) of the vehicle. The surge tank 15 is disposed to suppress pulsation of air sucked through the throttle valve 14.
[0022]
The air-fuel mixture introduced into the combustion chamber 18 in the cylinder 17 is compressed therein and is ignited and explodes when an ignition spark is emitted from the spark plug 19. The engine 10 obtains rotational torque by this explosion. Further, the burned gas is discharged to the exhaust pipe 21 through the exhaust valve 20 as exhaust gas. Note that the spark plug 19 generates the ignition spark by application of a high voltage boosted by the ignition coil 22 and distributed to each cylinder by the distributor 23.
[0023]
The starter motor 28 applies initial rotation to the engine 10 at the time of start-up, and is driven to rotate by receiving power supply from the battery 50 in accordance with an ON operation of the starter switch 40.
[0024]
On the other hand, in the above apparatus, the operating state of the engine 10 is detected through various sensors as described below. An intake pressure sensor 13 is disposed in the surge tank 15 of the intake pipe 11, and the sensor 13 measures the pressure (intake pressure) of air taken into the intake pipe 11. The distributor 23 is provided with a rotation speed sensor 24 that detects the rotation speed and rotation angle of the engine 10. Here, the rotation speed sensor 24 outputs a pulsed rotation angle signal (NE pulse) every 30 ° CA. Further, a water temperature sensor 26 is disposed in the cylinder 17 (water jacket) of the engine 10, and the sensor 26 detects the temperature of the engine cooling water. The outputs of these sensors are all taken into the ECU 30.
[0025]
The ECU 30 detects control parameters such as the intake pressure PM, the engine speed NE, and the water temperature Tw based on the detection outputs from the various sensors 13, 24, and 26.
Based on these data, the fuel injection amount (time) and ignition timing to the engine 10 are calculated. And the drive of the said injector 1 and the ignition coil 22 is controlled based on the said calculation result.
[0026]
In particular, in the present embodiment, fuel is injected in a predetermined period during which the engine 10 shifts from the exhaust stroke to the intake stroke, and this injected fuel is injected into the cylinder (inside the combustion chamber 18) as the intake valve 16 is opened in the intake stroke. The so-called “intake stroke synchronized injection” is introduced into the engine. In this case, the fuel injection is performed in the exhaust stroke of the engine 10 to form a uniform air-fuel mixture in the intake port 3 and then the air-fuel mixture flows into the cylinder. The timing will be set to the retard side. In the injection outside the intake stroke, the fuel injection is started near 150 ° CA to 90 ° CA before the intake TDC, whereas in the intake stroke synchronous injection, the fuel injection is started near 60 ° CA before the intake TDC. .
[0027]
Further, the operation information (ON / OFF signal) of the starter switch 40 is also taken into the ECU 30, and the ECU 30 determines whether or not the engine 10 is started based on the operation information of the starter switch 40. The ECU 30 receives power from the battery 50 and executes various controls including fuel injection control described later with the battery voltage VB.
[0028]
Next, the operation of the fuel injection control device configured as described above will be described. FIG. 2 is a flowchart showing a fuel injection control routine, which is executed by the ECU 30 for each fuel injection of each cylinder, that is, every 180 ° CA.
[0029]
When the routine of FIG. 2 starts, the ECU 30 first determines in step 101 whether or not the complete explosion flag XST is “0”. The complete explosion flag XST indicates whether or not the engine 10 after the start has reached a complete explosion, and XST = 0 indicates that it is before the complete explosion, and XST = 1 indicates that it is after the complete explosion. . Incidentally, the flag is initialized to “0” when the ECU 30 is initially turned on.
[0030]
If XST = 0, the ECU 30 proceeds to step 102 and reads various information required for fuel injection control at the time of engine start. That is, the engine rotational speed NE detected by the rotational speed sensor 24, the intake pressure PM detected by the intake pressure sensor 13, the water temperature Tw detected by the water temperature sensor 26, etc. are read.
[0031]
Thereafter, the ECU 30 searches the map for the complete explosion determination rotational speed STBNE in step 103. Specifically, in accordance with the relationship of FIG. 4, the complete explosion determination rotational speed STBNE corresponding to the water temperature Tw at that time is set. According to FIG. 4, STBNE = 800 rpm is set when Tw <−20 ° C., STBNE = 600 rpm is set when Tw = −20 to 0 ° C., and STBNE = 400 rpm is set when Tw> 0 ° C.
[0032]
Thereafter, in step 104, the ECU 30 compares the engine rotational speed NE with the complete explosion determination rotational speed STBNE. If NE <STBNE, the ECU 30 regards it as being before the complete explosion, makes a negative determination in step 104, and proceeds to step 105. In step 105, the ECU 30 searches the map for the predicted engine speed (next predicted NE) in the next combustion cylinder using FIG. According to FIG. 5, the next expected NE is obtained from the engine speed NE and the intake pressure PM before the complete explosion.
[0033]
In step 106, the ECU 30 calculates the valve opening time (valve valve opening time Tin) of the intake valve 16 in the next combustion cylinder. More specifically, as shown in FIG. 6, the exhaust valve 20 opens immediately before BDC, and closes immediately after TDC (intake TDC). The intake valve 16 opens immediately before the intake TDC, and closes immediately after the BDC. When the period during which the lift amount of the intake valve 16 exceeds the predetermined threshold value Lr is “valve valve opening time Tin”, the valve valve opening time Tin [msec] is:
Tin = 30 / NE · 1000 · K
Is calculated by Here, “K” is a coefficient for obtaining the time during which the valve lift amount exceeds the threshold value Lr in the intake stroke (180 ° CA) when the intake valve 16 opens (K <1). Incidentally, in the above equation, in order to increase the reliability of the NE value, if Tw <0 ° C., the instantaneous rotational speed from TDC to ATDC 30 ° CA is used as NE [rpm], and if Tw ≧ 0 ° C., ATDC 30 ° CA The instantaneous rotational speed at ~ ATDC 60 ° CA may be used as NE [rpm].
[0034]
As described above, the valve opening time Tin can be set in a period in which the intake flow velocity is relatively fast by obtaining the valve opening time Tin in a period in which the valve lift amount> Lr. That is, the Tin value can be set except for a region where the intake air flow rate is slow and the wet amount of fuel increases (before and after Tin).
[0035]
Thereafter, in step 107, the ECU 30 calculates a fuel injection amount TAU at the time of engine start. At this time, for example, the starting fuel amount TAUST is calculated according to the water temperature Tw according to the relationship of FIG. 7, and the fuel injection amount TAU [msec] in units of time is obtained by performing a rotational speed correction on the starting fuel amount TAUST. Calculated.
[0036]
Thereafter, the ECU 30 compares the calculated valve opening time Tin with the fuel injection amount TAU in step 108. If Tin ≧ TAU, the ECU 30 regards that the desired fuel amount (TAU) can be injected and supplied within the next valve opening time Tin, and makes a negative determination in step 108 and proceeds to step 109. In step 109, the ECU 30 sets the injection start timing by the injector 1 to “ATDC 30 ° CA (30 ° CA after intake TDC)”. Note that setting the injection start timing = ATDC 30 ° CA means that the fuel injection is performed at the timing when the intake air flow velocity becomes maximum when the engine 10 is started at a low temperature.
[0037]
Thereafter, the ECU 30 proceeds to step 110, sets the set injection start timing (ATDC 30 ° CA) in the output compare register, and once ends this routine.
[0038]
If Tin <TAU in step 108, the ECU 30 regards that the desired fuel amount (TAU) cannot be injected and supplied within the next valve opening time Tin, and makes an affirmative determination in step 108 and proceeds to step 120. . In such a case, the ECU 30 sets the injection start timing in accordance with the procedure of FIG. After setting the injection start timing, the ECU 30 proceeds to step 110, sets the injection start timing in the output compare register, and once ends this routine.
[0039]
On the other hand, if NE ≧ STBNE (when step 104 is YES), the ECU 30 regards that a complete explosion has occurred and proceeds to step 111. The ECU 30 sets “1” to the complete explosion flag XST in step 111, and calculates the TAU value after the start in step 112. At this time, in general, the basic injection amount is calculated according to the engine speed NE and the engine load (intake pressure PM), and air-fuel ratio correction is performed on the basic injection amount to calculate the TAU value. The
[0040]
Thereafter, the ECU 30 sets the injection start timing after starting (normal time) in step 113. Specifically, the injection start timing is “BTDC 60 ° CA (60 ° CA before intake TDC)”. After setting the injection start timing, the ECU 30 proceeds to step 110, sets the injection start timing in the output compare register, and once ends this routine.
[0041]
After the complete explosion flag XST is set to “1”, the determination at step 101 is negative every time, and the ECU 30 proceeds directly from step 101 to step 112 to calculate the TAU value after starting (normal fuel injection control is performed). carry out).
[0042]
Next, the procedure for setting the injection start timing in step 120 of FIG. 2 will be described with reference to FIG. In FIG. 3, the ECU 30 calculates the injection start timing according to the engine speed NE at that time in accordance with the relationship of FIG. 8 in step 121. According to FIG. 8, with ATDC 30 ° CA as a reference, the injection start timing shifts to the advance side as the engine speed NE increases. Moreover, ECU30 calculates the injection start timing according to the water temperature Tw at that time in step 122 according to the relationship of FIG. According to FIG. 9, on the basis of ATDC 30 ° CA, the injection start timing shifts to the advance side as the water temperature Tw increases.
[0043]
In subsequent step 123, ECU 30 determines whether or not the respective injection start timings calculated in steps 121 and 122 coincide with each other. If step 123 is YES (value by NE = value by Tw), ECU 30 proceeds to step 124. In step 124, the ECU 30 sets the calculated value (value by NE or value by Tw) according to either FIG. 8 or FIG. 9 as the current injection start timing, and then returns to the original routine of FIG.
[0044]
If step 123 is NO (if the value of NE is not equal to Tw), the ECU 30 proceeds to step 125. Then, the ECU 30 sets either the calculated value according to FIG. 8 (value by NE) or the calculated value by FIG. 9 (value by Tw) as the current injection start timing based on the determination result of step 125 ( Steps 126 and 127), returning to the original routine of FIG. In steps 125 to 127, the retarded injection start timing is selected from the calculated values according to FIG. 8 or FIG.
[0045]
Actually, if the water temperature Tw is, for example, −20 ° C. or higher, the calculated value according to FIG. 8 (calculated value by NE) is selected, and if the water temperature Tw is, for example, less than −20 ° C., the calculated value according to FIG. (Calculated value by Tw) is selected.
[0046]
FIG. 10 is a time chart showing the above control operation more specifically. FIG. 10 shows a fuel injection operation at the start of the engine 10 when the engine 10 is started at a low temperature (Tw = about −20 to 0 ° C.). The crank angle counter in the figure is a counter that is counted up every NE pulse (every 30 ° CA), and every combustion of each cylinder of # 1 to # 4 is completed every 720 ° CA (every cycle). ) Is cleared to “0”. The counter is counted within the range of “0 to 24”. The counting operation of the counter is performed in the fuel injection control routine of FIG. 2, but the illustration thereof is omitted in FIG.
[0047]
The injection signal to each cylinder is output from the ECU 30 in the order of # 1 → # 3 → # 4 → # 2. At the beginning of engine startup, the complete explosion flag XST is initialized to “0” (not shown). At the time of cranking by the starter motor 28, the engine speed NE is in a minute speed range, and according to the routines of FIGS. 2 and 3, for example, using the relationship of FIG. 8, the injection starts according to the engine speed NE Timing is set. That is,
・ In the period from the beginning of engine start to time t1, the injection start timing = ATDC 30 ° CA is
In the period from time t1 to t2, the injection start timing = intake TDC is
In the period from time t2 to t3, the injection start timing = BTDC 30 ° CA is set, and in the period after time t3, the injection start timing = BTDC 60 ° CA is set.
[0048]
Thus, when the engine 10 is started at a low temperature, the injection start timing is switched in the order of ATDC 30 ° CA → intake TDC → BTDC 30 ° CA → BTDC 60 ° CA as the engine speed NE increases. In other words, the injection start timing is advanced as NE increases.
[0049]
In the present embodiment, step 104 in FIG. 2 corresponds to the complete explosion determination means described in claims, and steps 105 to 109, 120 correspond to the start-up injection timing setting means. Of these, step 108 corresponds to the comparison means, step 109 corresponds to the first setting means, and step 120 (routine of FIG. 3) corresponds to the second setting means.
[0050]
According to the embodiment described in detail above, the following effects can be obtained.
[0051]
(A) In the present embodiment, it is determined whether or not the engine 10 is in a starting state before the complete explosion, and when it is determined that the engine 10 is before the complete explosion, The injection start timing is set on the retard side from the injection start timing (fuel injection timing). According to the above configuration, the intake stroke (opening timing of the intake valve 16) can be achieved even in the minute rotation range by shifting the same timing to the retard side from the normal injection start timing in the starting state before the complete explosion. ) Can be performed in synchronization with Therefore, the amount of wet fuel can be reduced, and a desired combustion torque can be obtained. As a result, the rotational speed increases quickly and stably at the time of starting the engine, and as a result, the startability of the engine 10 is improved. Moreover, according to the said structure, defective combustion, such as misfire resulting from a port wet etc., is improved and the riding comfort (starting feeling) of a vehicle is also improved.
[0052]
(B) The valve opening time (Tin) of the intake valve 16 in the next combustion cylinder is compared with the fuel injection time (TAU) in the next combustion cylinder. As a result of the comparison, the valve opening time Tin is more If longer, the start start timing by the injector 1 is set to a predetermined time (ATDC 30 ° CA). As a result of the comparison, if the fuel injection time TAU is longer, the injection start timing by the injector 1 is shifted to the advance side (see FIGS. 8 and 9).
[0053]
In other words, when the engine 10 starts rotating, the valve opening time Tin gradually decreases along with this, but there is an inconvenience that the fuel injection timing by the injector 1 is too late to be in time for closing the intake valve 16. This can be avoided and the injected fuel surely flows into the cylinder. Therefore, the injected fuel does not become wet in the intake port 3, and the problem that the control accuracy of the air-fuel ratio deteriorates due to this wet can be avoided.
[0054]
(C) The valve opening time Tin is calculated in a period in which the valve lift amount is a predetermined value or more. That is, even if the intake valve 16 is opened, if the valve lift is small, the intake flow rate is slow and the amount of fuel wet increases. Therefore, the valve opening time Tin is defined as described above, and the fuel is allowed to flow in a period in which the intake air flow velocity is relatively fast.
[0055]
(D) When the engine is started, the injection start timing is calculated individually according to the engine speed NE and the water temperature Tw (FIGS. 8 and 9), and the retard side value is selected from these individual injection start timings. I tried to do it. In this case, by selecting the injection start timing on the retarded angle side, excessive advance angle control is suppressed, and wetness due to fuel stagnation (stagnation before the intake valve 16 is opened) in the intake port 3 is reduced. It is solved more reliably.
[0056]
(E) In FIG. 8, the injection start timing is gradually shifted to the advance side as the engine speed NE increases, and in FIG. 9, the injection start timing is gradually set to the advance side as the water temperature Tw increases. It was made to move. In such a case, the injection start timing until the complete explosion can be set appropriately, and when the complete explosion is reached, it is possible to smoothly shift to normal fuel injection (intake stroke synchronized injection).
[0057]
(F) Further, the complete explosion determination rotational speed STBNE is variably set according to the water temperature Tw, and it is determined whether or not the engine 10 has reached a complete explosion according to the complete explosion determination rotational speed STBNE. In this case, even if the rotational speed at which the engine 10 can maintain the rotation by itself varies depending on the water temperature Tw (engine temperature), the proper fuel injection amount control can be continued in the period until the complete explosion actually occurs.
[0058]
(G) Since the fuel injection control at the time of starting the engine can be performed properly, the effect of reducing the emission emission amount at the time of starting is also obtained.
[0059]
Next, second to fifth embodiments of the present invention will be described. However, in the configuration of each of the following embodiments, components that are equivalent to those of the first embodiment described above are given the same reference numerals in the drawings and the description thereof is simplified. In the following description, differences from the first embodiment will be mainly described.
[0060]
(Second Embodiment)
FIG. 11 is a flowchart showing a fuel injection control routine in the second embodiment. The routine shown in FIG. 2 is obtained by changing a part of the routine shown in FIG. 2, and the processing in steps 105 to 109 and 120 in FIG. 2 is changed to the processing in steps 201 and 202 in FIG. .
[0061]
In FIG. 11, the difference from FIG. 2 will be described. After setting the fuel injection TAU at the start at step 201, the ECU 30 sets the injection start timing at step 202. In this case, for example, the injection start timing is set according to the engine speed NE using the relationship shown in FIG. Alternatively, the injection start timing is set according to the water temperature Tw using the relationship shown in FIG. In short, in FIG. 11, unlike FIG. 2, processing such as calculation of the valve opening time Tin and comparison between the Tin value and the fuel injection amount TAU is omitted.
[0062]
As described above, according to the present embodiment, as in the first embodiment, the engine speed is increased quickly and stably at the start of the engine, and the startability of the engine 10 is improved. An effect is obtained.
[0063]
(Third embodiment)
Next, a third embodiment will be described with reference to FIGS. In the first and second embodiments, the injection start timing at the time of engine start is variably set. However, in the present embodiment, the injection start timing is variably set as described above. In addition, it is characterized in that surplus fuel that cannot be supplied within the valve opening time is carried over to fuel injection of the next combustion cylinder.
[0064]
FIG. 12 is a flowchart showing a part of the fuel injection control routine in the present embodiment. In FIG. 12, the ECU 30 calculates ΔTAU by subtracting the previous valve opening time [msec] from the previous fuel injection amount [msec] in step 301.
[0065]
Next, the ECU 30 determines in step 302 whether ΔTAU is larger than “0”. If ΔTAU ≦ 0 (step 302 is NO), the ECU 30 proceeds to step 304 after setting “ΔTAU = 0” in step 303. If ΔTAU> 0 (step 302 is YES), the ECU 30 proceeds to step 304 as it is.
[0066]
In step 304, the ECU 30 adds “ΔTAU · Ke” to the current injection amount, and sets the added value as the fuel injection amount TAU. Here, “Ke” is an evaporation rate correction coefficient for correcting the evaporation rate of the fuel, and is set according to the relationship of FIG. 14, for example. That is, the evaporation rate correction coefficient Ke is set according to the outside air temperature (Ke> 1) under the condition that the outside air temperature (or intake air temperature) is, for example, −10 ° C. or higher. Thereafter, the ECU 30 sets a predetermined injection start timing in the output compare register in step 305.
[0067]
On the other hand, FIG. 13 is a flowchart showing an NE interrupt routine by the ECU 30 (however, this process only needs to be performed before the complete explosion). In FIG. 13, the ECU 30 determines in step 401 whether or not the current crank angle has reached the “injection end timing”. Here, the injection end timing corresponds to the end timing of opening of the intake valve 16.
[0068]
In step 402, it is determined whether or not fuel injection has already been completed. Then, if step 401 is YES and step 402 is NO, the ECU 30 proceeds to step 403 and immediately stops fuel injection. That is, at the crank angle at the end of injection, the fuel injection that has been continued until then is forcibly terminated.
[0069]
When the fuel injection is interrupted in the middle of the routine of FIG. 13, the surplus of the fuel that could not be injected is calculated as ΔTAU in step 301 of FIG. Then, “ΔTAU · Ke” is added to the next injection amount to obtain the fuel injection amount TAU, and the fuel corresponding to the TAU is injected and supplied to the engine 10 (steps 304 and 305).
[0070]
According to the present embodiment, as in the first and second embodiments, the engine speed can be increased quickly and stably at the start of the engine, and the startability of the engine 10 can be improved. Excellent effect is obtained.
[0071]
In particular, in the third embodiment, when the engine is started, the surplus fuel (ΔTAU) injected and supplied in a time longer than the valve opening time is added to the fuel injection amount in the next combustion cylinder. did. At this time, when the fuel injection by the injector 1 continues to a predetermined crank angle, the fuel injection at that time is stopped. Therefore, even when the injection start timing is set to the retard side when the engine is started, and the predetermined fuel injection amount cannot be injected within the valve opening time of the intake valve 16, the surplus fuel is used for the next combustion. The desired combustion torque can be secured by carrying over. Furthermore, since the ΔTAU is multiplied by the fuel evaporation rate correction coefficient Ke, more accurate fuel injection control can be realized.
[0072]
In the third embodiment, the injection end timing at the time of engine start (the injection end timing in step 401 in FIG. 13) may be set variably. Specifically, for example, the injection end timing is set based on the engine speed NE in accordance with the relationship of FIG. In FIG. 15, the injection end timing is set within the range of ATDC 150 ° CA to ATDC 30 ° CA according to the NE value before the complete explosion, and the injection end timing is set to the retard side as the NE becomes lower. As a result, both the injection start timing and the injection end timing shift to the advance side as the rotation rises, and the inflow of fuel into the cylinder at the optimum time can be realized.
[0073]
(Fourth embodiment)
Next, a fourth embodiment will be described with reference to FIGS. In the present embodiment, out of the fuel injection amount at the time of starting the engine, the fuel amount that is injected when the intake valve is closed and becomes the port wet is obtained, and the injection amount correction is performed according to the fuel amount. The aim is to improve the engine startability by eliminating the fuel shortage caused by the wet.
[0074]
16 and 17 show a fuel injection control routine in the present embodiment, which is executed in place of, for example, the routine of FIG. The ECU 30 first determines in step 501 of FIG. 16 whether or not the engine is currently being started. In this case, for example, it is determined whether or not the engine rotational speed NE has reached the complete explosion determination rotational speed (the value set in FIG. 4). It is considered to be.
[0075]
When it is determined that the engine is starting (when step 501 is YES), the ECU 30 proceeds to step 502, and after IG is turned on, reads the number of injections and the number of combustion cycles after cranking is started. The number of combustion cycles is a numerical value that is counted up when fuel injection of all cylinders of the engine 10 is completed (every 720 ° CA). "Incremented by one. Each value of the number of injections and the number of combustion cycles is counted by other processing (not shown).
[0076]
Thereafter, in step 503, the ECU 30 calculates a starting basic injection amount TAUA based on the number of combustion cycles. The starting basic injection amount TAUA is set so as to decrease as the number of combustion cycles increases, but is given as the same value for all cylinders # 1 to # 4 having the same combustion cycle. In other words, the basic injection amount at the beginning of the start (first cycle) is added with an increase value in consideration of the wet amount of the injected fuel. On the other hand, after the second cycle, every time the combustion cycle is repeated, the wet amount approaches the saturation point, so the basic injection amount is reduced.
[0077]
Thereafter, in step 504, the ECU 30 calculates a water temperature correction coefficient FTHW based on the engine water temperature Tw. The water temperature correction coefficient FTHW is set to a larger value as the water temperature Tw is lower.
[0078]
Next, the ECU 30 multiplies the starting basic injection amount TAUA calculated in step 505 by the water temperature correction coefficient FTHW and sets the product as the starting injection amount TAUB (TAUB = TAUA · FTHW).
[0079]
Thereafter, the ECU 30 determines in step 506 in FIG. 17 whether or not the number of injections from the start of cranking is greater than “2”. If it is the first and second injections immediately after starting, the ECU 30 makes a negative determination in step 506. In step 507, the ECU 30 sets the injection amount correction value FDNE corresponding to the rotational speed increase ΔNE due to combustion to “0”, and in the next step 508, sets the injection timing correction value FTINJ corresponding to the rotational speed increase ΔNE to “ 0 ”.
[0080]
That is, the first and second injections at the start of the engine are not affected by the increase in the rotational speed due to the combustion, and therefore the correction based on the rotational speed increase ΔNE is prohibited. Incidentally, it is considered that rotation of about 360 ° CA is required from the start of cranking to the start of combustion.
[0081]
Further, after the third injection, the ECU 30 makes a positive determination in step 506. In step 509, the ECU 30 predicts an increase in rotational speed ΔNE due to combustion based on the number of injections from the start of startup. The ΔNE value is predicted from an increase in NE when it is assumed that normal combustion can be performed from the first start injection. In this case, as shown in the table value in the figure, the ΔNE value is obtained from the number of injections, and different characteristics are switched as appropriate for each water temperature Tw at the start (in the figure, Tw1> Tw2> Tw3).
[0082]
The NE rising behavior will be described with reference to the time chart of FIG. In the third and subsequent injections (after the injection of the # 4 cylinder in the figure) that is assumed to start combustion after the start, the NE increase degree differs depending on the water temperature Tw. In this case, the higher the water temperature Tw, the less the influence of engine friction. Therefore, if Tw1> Tw2, Tw1 has a higher NE increase degree (ΔNE value is larger).
[0083]
Next, the ECU 30 calculates an injection amount correction value FDNE based on the predicted ΔNE value in step 510. In this case, the predicted ΔNE value is added to the NE value in the intake TDC of the current combustion cylinder, and the intake valve opening time TVO is calculated from the added value (NE + ΔNE). Further, from the difference between the starting injection amount (injection time) TAUB and the intake valve opening time TVO, the surplus of the intake valve opening injection, that is, the intake valve closing injection amount TVC is calculated (TVC = TAUB−TVO). Then, an injection amount correction value FDNE corresponding to the insufficiency of the injection amount when the intake valve is closed is calculated from the table value in the figure according to the injection amount TVC when the intake valve is closed while matching the characteristics for each water temperature Tw.
[0084]
Here, the fuel inflow rate into the cylinder (inside the cylinder) at the same injection amount when the intake valve is opened and when the intake valve is closed has a relationship shown in FIG. 19, for example. That is, according to FIG. 19, the in-cylinder inflow rate is smaller in the intake valve closing injection than in the intake valve open injection, and the in-cylinder inflow rate is smaller as the water temperature Tw is lower. Therefore, the injection amount correction value FDNE is set in consideration that the in-cylinder inflow rate is relatively low and the inflow rate changes according to the water temperature Tw in the intake valve closing injection.
[0085]
In the time chart of FIG. 18, when calculating the injection amount correction value FDNE for the third injection, the intake valve opening time TVO is calculated from the expected rotation speed (NE + ΔNE (i)) in the intake TDC of the # 4 cylinder. From the TVO value, the intake valve closing injection amount TVC (the surplus of the intake valve opening injection) is calculated. Note that the rotational speed increase ΔNE (i) in the third injection corresponds to the rotational speed increase due to the combustion of the first injection (# 1 cylinder injection), and the rotational speed increase ΔNE (i + 1) in the fourth injection. Corresponds to an increase in rotation due to combustion of the second injection (# 3 cylinder injection).
[0086]
Further, the ECU 30 calculates a correction value FTINJ for the next injection timing based on the predicted ΔNE value in step 511. In this case, using the table values in the figure, the injection timing correction value FTINJ is set to the advance side correction value as the ΔNE value increases.
[0087]
Then, after calculating the correction values FDNE and FTINJ, the ECU 30 calculates the final injection amount TAU from the following equation in step 512.
[0088]
TAU = TAUB + FDNE
In step 513, the ECU 30 calculates the final injection timing TINJ from the following equation.
[0089]
TINJ = TINJB + FTINJ
However, “TINJB” is a fixed basic injection timing set in advance. Finally, the ECU 30 commands the fuel injection by the injector 1 based on the calculated TAU value and TINJ value in step 515 and ends this routine. On the other hand, when step 501 in FIG. 16 is NO (when the engine is not started), the ECU 30 proceeds to step 514 in FIG. 17 as it is, and performs normal fuel injection control after starting in steps 514 and 515.
[0090]
The control of the fuel injection amount and the fuel injection timing when starting the engine will be described more specifically with reference to FIGS. However, in FIGS. 20 and 21, for convenience, the fuel injection pulse is shown by setting the flight time of the injected fuel to “0”.
[0091]
As shown in FIG. 20A, in the first and second injections immediately after the start, the injection amount correction value FDNE is “0”, so the final injection amount TAU is set as “TAU = TAUB”. Further, as shown in FIG. 20B, after the third injection, the intake valve closing injection amount TVC and the injection amount correction value FDNE corresponding to the ΔNE value are calculated, and based on the calculation results, “ The final injection amount TAU is set as “TAU = TAUB + FDNE”.
[0092]
On the other hand, as shown in FIG. 21A, in the first and second injections immediately after the start, the injection timing correction value FTINJ is “0”, so that “TINJ = TINJB” is set as the final injection timing TINJ (injection start timing). ) Is set. Further, as shown in FIG. 21B, after the third injection, the injection timing correction value FTINJ is calculated according to the ΔNE value, and the final injection timing TINJ (injection start timing) is set as “TINJ = TINJB + FTINJ”. Is done. In FIG. 21 (b), the injection timing is corrected so as to be close to the end of the intake stroke (for example, BDC) based on the predicted rotation speed increase ΔNE. That is, the final injection timing TINJ is set so that the end of fuel injection at start-up does not become later than the closing timing of the intake valve 16.
[0093]
In the present embodiment, steps 503 to 505 in FIG. 16 are the starting injection amount calculation means, step 509 in FIG. 17 is the rotation increase prediction means, and step 510 is the valve closing injection amount calculation means. The steps 510 and 512 correspond to the injection amount correction means, and the steps 511 and 513 correspond to the fuel injection timing correction means.
[0094]
As described above, according to the fourth embodiment, the following effects can be obtained.
[0095]
(A ′) The increase in engine speed ΔNE is predicted when the engine is started, and the fuel injection amount when the intake valve is closed (the injection amount TVC when the intake valve is closed) out of the injection amount TAUB at the start based on the ΔNE value Was calculated. The starting injection amount TAUB is corrected to increase based on the intake valve closing injection amount TVC. According to the above configuration, even when the rotational speed NE increases suddenly when the engine is started and fuel injection by the injector 1 takes place when the intake valve is closed (period before the intake stroke), the intake valve is closed. The fuel shortage due to the wet injection is eliminated. As a result, the startability of the engine 10 can be improved.
[0096]
(B ′) An injection amount correction value FDNE is obtained based on the in-cylinder inflow rate of the intake valve 16 when the intake valve 16 is opened and when the valve 16 is closed, and injection is performed using the injection amount correction value FDNE. The amount TAUB was corrected. In such a case, it is possible to perform more appropriate fuel injection by giving an injection amount correction value FDNE that takes into account the in-cylinder inflow rate when the intake valve 16 is opened and closed.
[0097]
(C ′) The fuel injection timing is corrected on the basis of the predicted rotation speed increase ΔNE so that the end of fuel injection at start-up does not become later than the closing timing of the intake valve. If fuel injection by the injector 1 takes place after the intake stroke, the amount of fuel inflow into the cylinder will be reduced by that amount, but the above problem can be avoided by correcting the fuel injection timing according to the increase in rotational speed ΔNE. it can.
[0098]
(D ′) The increase in rotational speed ΔNE is predicted from the number of injections from the start of engine start and the temperature Tw. In this case, the influence of engine friction is reflected in the rotational speed prediction, and the rotational speed increase ΔNE can be accurately predicted.
[0099]
(E ') During fuel injection at the start of the engine, correction of the fuel injection amount or correction of the fuel injection timing is not performed. Thereby, unnecessary correction processing can be omitted.
[0100]
(F ′) The starting injection amount TAUB is calculated based on the number of combustion cycles from the start of the engine 10 and the water temperature Tw. The larger the number of combustion cycles, the lower the injection amount and the lower the water temperature Tw. The amount was increased. In this case, the starting injection amount TAUB can be set according to the degree of saturation of the fuel wet, and the inconvenience that an excessive amount of fuel is injected is suppressed.
[0101]
(Fifth embodiment)
Next, a fifth embodiment in which a part of the fourth embodiment is changed will be described. In this embodiment, in order to increase the in-cylinder inflow rate of fuel injected by the injector, the injection amount at start is divided and injected. This will be described with reference to the time chart of FIG.
[0102]
As shown in FIG. 22, at the time of fuel injection after the third injection (after injection of the # 4 cylinder), a part of the final injection amount TAU (shaded portion in the figure) is matched with the fuel injection timing of the previous combustion cylinder. Divide and spray. That is, the fuel amount (TVC + FDNE) obtained by adding the injection amount TVC when the intake valve is closed (the fuel injection amount when the intake valve is closed) and the injection amount correction value FDNE corresponding to the TVC value is the intake stroke of the combustion cylinder at that time The fuel is divided and injected at the earlier timing.
[0103]
According to the above configuration, the fuel separately injected at a timing earlier than the intake stroke of the combustion cylinder temporarily adheres to the wall surface of the intake port, but gradually evaporates during the period until the intake stroke and flows into the cylinder during the intake stroke. Is done. This solves the problem that the fuel injection amount when the intake valve is closed remains wet and remains in the intake port, and the amount of fuel that should flow in is insufficient. As a result, the fuel can be efficiently flowed into the cylinder and the engine startability can be improved.
[0104]
In FIG. 22, split injection (pre-injection) is performed in accordance with the fuel injection timing of the previous combustion cylinder, but the pre-injection timing is not limited to this. In short, it is sufficient if the fuel is injected at the previous timing in consideration of the evaporation time for fuel injection when the intake valve is closed. For example, when the evaporation time at the port wall surface is expected to be long, pre-injection should be performed at a relatively early time, and when the evaporation time is expected to be short, pre-injection should be performed at a relatively late time. .
[0105]
The embodiment of the present invention can be realized in the following form in addition to the above. In the first to third embodiments, the injection start timing is set according to the engine speed NE or the water temperature Tw when the engine is started, but this is changed. For example, the injection start timing is set according to the number of combustion cycles from the beginning of engine startup (when IG is on). In this case, a map in which the horizontal axis in FIG. 8 is replaced with the number of cycles may be used, and the injection start timing is gradually shifted to the advance side as the number of combustion cycles is counted up.
[0106]
Further, the injection start timing is set according to the elapsed time from the beginning of engine start (when IG is on). In this case, the injection start timing is shifted to the advance side as the elapsed time increases. Furthermore, when the injection start timing is set according to the engine speed NE, the water temperature Tw, the number of combustion cycles, the elapsed time, etc., the same timing may be changed linearly. Each of the above processes can be appropriately applied to step 202 in FIG. 11 in the second embodiment.
[0107]
Furthermore, the injection start timing (fuel injection timing) is changed by two values before and after the complete explosion of the engine. For example, the injection start timing = ATDC 30 ° CA before the complete explosion, and the injection start timing = BTDC 60 ° CA after the complete explosion. In short, when it is determined that it is before the complete explosion, it is sufficient if the same timing is set on the retard side from the normal injection start timing set after the complete explosion.
[0108]
In the routine of FIG. 2, the complete explosion determination rotational speed STBNE is variably set according to the water temperature Tw, but this complete explosion determination rotational speed STBNE is set to a fixed value. In this case, the processing load on the ECU 30 can be reduced by omitting the STBNE value search process.
[0109]
In the fourth embodiment, whether or not “after the third injection” is determined as a reference for determining whether or not the injection amount correction and the injection timing correction at the start of the engine are necessary, but this is changed. For example, after cranking starts, it is determined whether or not the first explosion has come. Before the first explosion, injection amount correction and injection timing correction are prohibited (correction amount = 0), and after the first explosion, injection amount correction and injection timing correction are performed.
[0110]
In the fourth embodiment, the injection amount correction and the injection timing correction are performed according to the rotation speed increase ΔNE, but these are changed. With regard to the device that performs the injection amount correction according to at least the above procedure, the effect of eliminating the fuel shortage due to the wetness of the intake valve closing injection and improving the engine startability can be obtained.
[Brief description of the drawings]
FIG. 1 is an overall configuration diagram showing an outline of a fuel injection control device in an embodiment of the invention.
FIG. 2 is a flowchart showing a fuel injection control routine in the first embodiment.
FIG. 3 is a flowchart showing an injection timing setting subroutine.
FIG. 4 is a diagram showing a relationship between a water temperature and a complete explosion determination rotational speed STBNE.
FIG. 5 is a map for searching for an expected NE.
FIG. 6 is a diagram showing a relationship between a valve lift amount and an intake air flow rate.
FIG. 7 is a diagram showing a relationship between a water temperature and a starting fuel amount TAUST.
FIG. 8 is a diagram showing the relationship between engine speed and injection start timing.
FIG. 9 is a diagram showing the relationship between water temperature and injection start timing.
FIG. 10 is a time chart for explaining the outline of the operation.
FIG. 11 is a flowchart showing a fuel injection control routine in the second embodiment.
FIG. 12 is a flowchart showing a part of a fuel injection control routine in the third embodiment.
FIG. 13 is a flowchart showing an NE interrupt routine.
FIG. 14 is a diagram showing the relationship between the outside air temperature and the evaporation rate correction coefficient Ke.
FIG. 15 is a diagram showing the relationship between engine speed and injection end timing.
FIG. 16 is a flowchart showing a fuel injection control routine in the fourth embodiment.
FIG. 17 is a flowchart illustrating a fuel injection control routine continued from FIG. 16;
FIG. 18 is a time chart showing fuel injection and rotational rise behavior of each cylinder at the time of engine start.
FIG. 19 is a diagram showing the relationship between the water temperature and the in-cylinder inflow rate of fuel.
FIG. 20 is a diagram specifically showing injection amount correction.
FIG. 21 is a diagram specifically showing injection timing correction.
FIG. 22 is a time chart showing fuel injection and rotational increase behavior of each cylinder at the time of engine start in the fifth embodiment.
[Explanation of symbols]
1 ... Injector
3 ... Intake port,
10: Engine (internal combustion engine),
16 ... Intake valve,
24. A rotational speed sensor as a rotational speed detection means,
26 ... Water temperature sensor as temperature detecting means,
30: Complete explosion determination means, starting injection timing setting means, comparison means, first setting means, second setting means, starting injection amount calculation means, rotation rise prediction means, valve closing injection amount calculation means, injection ECU (electronic control unit) that constitutes a quantity correction means and a fuel injection timing correction means.

Claims (9)

A fuel injection control device for an internal combustion engine that is applied to an internal combustion engine that injects fuel from an injector to an intake port and performs fuel injection by the injector in response to an intake stroke period associated with opening of the intake valve,
A starting injection amount calculating means for calculating a starting injection amount of the next combustion cylinder when the internal combustion engine is in a starting state before the complete explosion;
Similarly, when the internal combustion engine is in the starting state before the complete explosion, a rotation increase prediction means for predicting an increase in the engine speed due to combustion accompanying the first explosion ,
Based on the predicted increase in engine speed, a closing-time injection amount calculation means for calculating a fuel amount to be injected when the intake valve is closed among the starting-time injection amounts;
A fuel injection control device for an internal combustion engine, comprising: an injection amount correcting means for increasing the starting injection amount based on the calculated injection amount when the intake valve is closed. The fuel injection control device according to claim 1,
The injection amount correction means obtains an injection amount correction value based on an in-cylinder inflow rate between the intake valve opening injection and the intake valve closing injection, and uses the injection amount correction value to start injection A fuel injection control device for an internal combustion engine that corrects the amount. In the fuel injection control device according to claim 1 or 2,
The fuel amount obtained by adding the calculated fuel injection amount when the intake valve is closed and the correction injection amount according to the injection amount when the valve is closed is divided and injected at a timing earlier than the intake stroke of the combustion cylinder at that time. A fuel injection control device for an internal combustion engine. In the fuel injection control device according to claim 1 or 2,
The fuel injection timing is corrected based on the predicted increase in engine speed so that the end of start-up fuel injection based on the fuel injection amount corrected by the injection amount correction means is not delayed later than the closing timing of the intake valve. A fuel injection control device for an internal combustion engine, comprising fuel injection timing correction means. The fuel injection control device according to claim 4, wherein
A fuel injection control device for an internal combustion engine that does not correct the fuel injection timing during fuel injection from the start of cranking to the first explosion . In the fuel-injection control apparatus in any one of Claims 1-5 ,
The rotation increase prediction means is a fuel injection control device for an internal combustion engine that predicts an increase in the engine speed from the number of injections from the start of the engine and the engine temperature. In the fuel-injection control apparatus in any one of Claims 1-6 ,
A fuel injection control device for an internal combustion engine, which does not correct the fuel injection amount by the injection amount correction means during fuel injection from the start of cranking to the first explosion . The fuel injection control device according to any one of claims 1 to 7,
Means for counting the number of combustion cycles from the start of the engine, with all the cylinders of the internal combustion engine combusting as one cycle,
The starting injection amount calculation means is a fuel injection control device for an internal combustion engine that calculates a starting injection amount based on the number of combustion cycles from the start of the internal combustion engine. The fuel injection control device according to claim 8 , wherein
The starting injection amount calculation means is a fuel injection control device for an internal combustion engine that reduces the injection amount as the number of combustion cycles increases.

Images