JP2001152926A - Fuel injection control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To dissolve a problem that a feed amount of auxiliary fuel is differed every cylinder since auxiliary fuel is injected in an intake pipe regardless of a cycle of each cylinder only for a specified time after ON of a starter though it is known that an auxiliary fuel injection device is provided in an intake pipe to improve startability of an internal combustion engine. SOLUTION: By dividing an injection timing for auxiliary fuel, each division injection timing is synchronized with the suction stroke of each cylinder. Further, by correcting an injection amount of each division injection timing according to a suction rate, i.e., a distribution rate of auxiliary fuel differed classified by each cylinder, auxiliary fuel to all of cylinders is evenly distributed and startability is improved by improving a combustion state. 411-414 are taken as pulses at which main fuel is injected in a cylinder and 401-404 are taken as pulses corrected for injection of auxiliary fuel in an intake pipe.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection control device for obtaining good startability in an internal combustion engine.

[0002]

2. Description of the Related Art As a prior art, Japanese Patent Laid-Open Publication No.
As described in Japanese Patent No. 74, an auxiliary fuel injection device into an intake pipe for improving the startability of a direct injection internal combustion engine is known. However, in the prior art, only one auxiliary fuel injection device is installed in the surge tank for cost reduction, and auxiliary fuel injection is performed for a certain time immediately after the starter switch is turned on regardless of the crank angle. Since the fuel injected into the tank is not evenly distributed to each cylinder due to insufficient mixing with air, the fact is that the startability is not sufficiently improved.

[0003]

To solve this problem in the prior art, in the present invention, an intake pipe (intake passage) such as a surge tank is provided as only one common to each cylinder.
By improving the injection control method of only one auxiliary fuel injection device, the amount of auxiliary fuel sucked into each cylinder is equalized, and the startability of a direct injection type or intake port injection type internal combustion engine is improved. The purpose is to improve.

[0004]

According to the present invention, there is provided a fuel injection control device according to the present invention as means for solving the above-mentioned problems. In this device, the injection timing of the auxiliary fuel is divided so as to be synchronized with the intake timing of each cylinder, and the injection amount for each divided injection timing is corrected according to the intake rate of the auxiliary fuel of each cylinder, that is, the distribution rate. Therefore, the amount of fuel taken into each cylinder can be equalized, and the air-fuel ratio control of each cylinder, and hence the combustion state, is improved, so that the startability is improved. In the control device according to the second aspect, it is possible to predict the intake amount of the auxiliary fuel into each cylinder, and it is possible to determine appropriate injection control specifications.
In the control device according to the third aspect, since it is possible to cope with a change in the control method or a change in environmental conditions at the time of starting the engine, it is possible to determine a more appropriate injection control specification. In the control device according to claim 4,
By changing the opening degree of the intake air amount adjusting valve such as the throttle valve of the internal combustion engine, it is possible to obtain better startability. According to the control device of the fifth aspect, it is possible to prevent the discharge of unburned fuel due to ignition failure caused by injecting the main fuel before the auxiliary fuel reaches each cylinder.

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an example of the configuration of an in-cylinder fuel injection type internal combustion engine equipped with a conventionally known auxiliary fuel injection device at start-up. The internal combustion engine 100 includes an auxiliary fuel injection device 101, an intake pipe 102 provided with the auxiliary fuel injection device 101, a throttle valve 103, an intake valve 104, a spark plug 105, an exhaust valve 106, and a main fuel injection device for directly injecting fuel into each cylinder. 107, injector drive device 108, fuel injection control device 109, crank angle detection device 110, piston 11
1, a starter 112 and the like. Internal combustion engine 1
When starting 00, the piston 111 is moved by the starter 112 to compress the intake air in the cylinder, the fuel is injected from the injector 107, and the fuel is mixed with the compressed intake air. Perform ignition. When the internal combustion engine 100 starts, the power of the starter 112 is cut off, and the internal combustion engine 100 starts operating by itself. However, since it is difficult to obtain a good air-fuel mixture at a low temperature start, fuel is supplied from the auxiliary fuel injection device 101 to the intake pipe 10.
Injecting the fuel into the cylinder 2 and inhaling the fuel, which has been vaporized to some extent, together with the intake air into each cylinder, improves the startability.

In the conventional control method for the internal combustion engine 100, fuel is injected from the auxiliary fuel injection device 101 into the intake pipe 102 for a predetermined period regardless of the crank angle. As a result of the influence of the shape of the auxiliary fuel injection device 101, the installation position of the auxiliary fuel injection device 101, the injection start timing, etc., the distribution of the injected fuel to the respective cylinders becomes more frequent, and the cylinders do not have an appropriate air-fuel ratio. was there. Therefore, in the present invention, the auxiliary fuel injection at the time of starting is divided injection, and the timing (injection timing) and the injection amount (injection time) of each divided injection are specified in advance in consideration of the relationship between the injection timing and the cylinder distribution. By doing so, the distribution of auxiliary fuel to each cylinder is improved and equalized.

FIG. 2 is a block diagram showing the configuration of the entire system for implementing the present invention. This system includes an internal combustion engine main body 1305 including a control unit 1301, a crank angle detection unit 1302, a starting unit 1303, and an intake pipe auxiliary fuel injection unit 1304.

FIG. 3 shows the structure of the intake pipe 202 in the first embodiment of the present invention. Internal combustion engine 1305 in this example
Is an in-cylinder direct injection gasoline engine having four in-line four cylinders. An auxiliary fuel injection device 201 is installed in the intake pipe 202 immediately downstream of the throttle valve 203, and fuel is injected in the direction of arrow D. The intake pipe 202 is connected to one longitudinal end of a surge tank 202a, which is a part of the intake manifold, so that the auxiliary fuel is # 1.
It is assumed that the cylinders are distributed from cylinder # 4 to cylinder # 4 in the order of arrangement.
Other configurations are the same as those of the conventional system shown in FIG. However, the control means 1301
Needless to say, the content of the software of the control device 109 becomes different. The ignition order is # 1 → # 3 → #
4 → # 2.

FIG. 4 shows a flowchart of the fuel injection control in the first embodiment of the present invention. In step 301, when an engine switch (not shown) (i.e., an ignition switch and a starter switch) is turned on, when it is recognized in step 302 that the switch ST of the starter 112 is ON, step 304 is executed.
Move to. Control device 109 stores the crank angle at the time of stop before engine 100 (1305) is started by backup power, and can identify the crank angle immediately after the start of restart. In step 304, the crank angle is detected by the crank angle detection device 110, and it is determined whether the # 1 cylinder is in the intake stroke. If the intake stroke and proceeds to step 305, the calculation of the correction coefficient k ₁ of the auxiliary fuel injection amount for the # 1 cylinder (injection time). # 2 respectively perform condition determination in step 306, 308, 310 also # 4 cylinder, the calculation of the correction coefficient similarly #i cylinder in step 307,309,311 k _{i (i} = 2,3,4) Do. Details of the method of calculating the correction coefficient k will be described later. After calculating the correction coefficient k for each cylinder, the preset basic injection amount S _B is divided by the correction coefficient k in step 312, and this is set as the injection amount S _i. An auxiliary fuel injection is performed into the pipe 202.

[0010] Thereafter, in step 314, main injection is performed. The main injection may be performed directly into the cylinder, or may be performed into the intake pipe. Then, returning to step 302, it is determined whether or not the starter switch ST is continuously ON. If the starter switch ST is ON, the above-described routine is repeated and executed again. In step 302, the starter switch S
If T is OFF, the process proceeds to step 303. In step 303, it is determined whether or not the start has been completed. If it is determined that the start has been completed, the process proceeds to step 316 to start another engine control. Step 303
If it is determined that the start is not completed (start has failed), the routine proceeds to step 317, where the engine 100
To stop.

FIG. 5 shows a timing chart of the auxiliary fuel injection in the first embodiment of the present invention. When the ignition switch is turned on together with the starter switch at 409, the injection timing of the # 1 cylinder is firstly reached in the example shown in FIG. Reference numerals 401 to 404 denote auxiliary fuel injection pulses of # 1 to # 4, respectively, and reference numerals 405 to 408 denote intake strokes of the respective cylinders. Also, 411,413,
Reference numerals 414 and 412 denote injection devices 107 installed for each cylinder.
Represents a pulse for main fuel injection according to (1). Since the auxiliary fuel is injected into the surge tank which is a part of the intake pipe 202, the auxiliary fuel is distributed from the surge tank to all the cylinders # 1 to # 4, but in synchronization with the intake stroke 405 of the # 1 cylinder. By performing the auxiliary fuel injection, most of the auxiliary fuel can be taken into the # 1 cylinder. Similarly, the auxiliary fuel injection 403 is performed during the intake stroke 407 of the # 3 cylinder.
04 is the auxiliary fuel injection 40 during the intake stroke 408 of the # 4 cylinder.
No. 2 causes the intake stroke 406 of the # 2 cylinder to take in most of the injected fuel. At this time, the correction of the auxiliary fuel injection amount mentioned above is performed to equalize the amount of fuel taken into each cylinder.

Here, how to obtain the correction coefficient k for the auxiliary fuel injection amount will be described in detail. Factors that determine the injection correction coefficient k can be classified into mechanical factors and control factors mainly determined by the design of the engine structure.

First, a method of obtaining a correction coefficient related to a mechanical factor will be described. FIG. 6 shows a conceptual diagram of the calculation method. Here, as mechanical influence factors, the installation position of the auxiliary fuel injection device 201, the auxiliary fuel injection direction and the penetration force of the spray,
And the order of intake of the engine 100. The intake coefficient k _hi (i = 1,..., 4) of each cylinder (# 1 to # 4) determined by these factors can be obtained by experiment, but as a rough guide, it can also be obtained by the following calculation. be able to.

Since the coefficient A _i due to the influence of the installation position of the auxiliary fuel injection device 201 changes as shown by a curve 501 shown in FIG. 6A, it is roughly calculated that A _i = 1 / (# i of the cylinder #i). (Distance to the intake valve 104). Further, since the coefficient B _i due to the influence of the auxiliary fuel injection direction and the spray penetration force changes as shown by a curve 502 shown in FIG. 6B, it is roughly calculated that B _i = 1 / (the arrival position of the spray tip) From each cylinder to each cylinder). Further, the coefficient C _i due to the influence of the intake order of each cylinder is represented by a curve 503 shown in FIG.
Therefore, it can be roughly expressed as C _i = 1 / (distance to the previous intake stroke cylinder). Then, by multiplying these values, the intake coefficient (predicted intake rate) k _hi (i = 1,..., 4) of each cylinder as shown in FIG. That is, k _hi = A _i × B _i × C _i

Next, the correction coefficient related to the control factor will be described. Here, the start timing of the auxiliary fuel injection, the engine speed, and the throttle opening are taken as control factors having an influence. First, the injection start timing of the divided auxiliary fuel is determined, and the distribution ratio (intake ratio) to each cylinder at this time is determined. The relationship between the injection start timing and the distribution ratio is shown in FIG.
As shown in the figure, the maximum value is shown at the beginning of the intake stroke of each cylinder. In FIG. 7, a curve 601 indicates the distribution ratio to the # 1 cylinder,
The curve 603 indicates the distribution ratio to the # 3 cylinder, and the curve 604 indicates # 4.
Curve 602 indicates the distribution ratio to cylinder # 2, and the distribution ratio to cylinder # 2. Of the auxiliary injection fuel injected in synchronization with the intake stroke of the #j cylinder, the other #i cylinders (i =
Predicted inhalation rate k _ui (C _Aj ) for inhalation into 1, ..., 4)
Is defined as follows.

[0016]

(Equation 1)

Here, C _Aj is the crank angle from the TDC of the # 1 cylinder to the injection start timing, a _i is the phase shift angle of the #i cylinder with respect to the # 1 cylinder, and b is the intake phase shift determined by the shape of the intake manifold. Angle, c is intake valve 10
4, a correction coefficient determined by the valve opening period, etc., d represents a predicted minimum intake rate (distribution rate of the intake valve closing cylinder), and c and d can be obtained by experiments.

FIG. 8 shows a method for obtaining the fuel intake rate at the start of the injection of the auxiliary fuel at the start based on the above-mentioned relationship.
In FIG. 8, (1) corresponds to FIG. 5, and each left half of (2) to (5) corresponds to FIG. The distribution rate of fuel to each cylinder in the auxiliary fuel injection synchronized with the intake stroke of the # 1 cylinder is as indicated by a polygonal line 701 shown in the right half of FIG. 8 (2), and similarly in the same manner as the intake stroke of the # 3 cylinder. The distribution of fuel to the respective cylinders by the supplementary fuel injection is indicated by the broken line 702 in FIG. 8C, the broken line 703 in FIG. 8D for the # 4 cylinder, and FIG. 8F for the # 2 cylinder. A broken line 704 of FIG.

Here, assuming that the value of d is very small, the intake rate of the auxiliary fuel into each cylinder is given by the following relationship: # 1: k _t1 = k _u1 (C _A1 ) + k _u1 (C _A3 ) _{# 3: k t3 = k u3} (C A3) + k u3 (C A4) # 4: k t4 = k u4 (C A4) + k u4 (C A2) # 2: k t2 = k u2 (C A2) + k u2 (C _A1 ).

Next, the control device 109 performs correction in consideration of the influence of the engine speed and the influence of the throttle opening. It has been found that the distribution rate is made uniform with respect to the engine speed because the airflow becomes faster as the rotation increases, and the distribution rate is made more uniform with respect to the throttle opening when the throttle valve 203 is closed. The suction coefficient k _si after correction by these phenomena can be expressed as follows.

[0021]

(Equation 2)

Here, r (rev / s) is the cranking speed at engine start, q is a coefficient obtained experimentally, θ is the angle of the throttle valve 203 from the fully closed position,
Is established to satisfy the condition of q> r _max the maximum value r _max cranking rotation speed at the start of the engine to be assumed. By this calculation, the polygonal line 801 of the distribution ratio shown in FIG. 9A is corrected as shown by the polygonal line 802.

Finally, a correction is made in consideration of the fuel vaporization rate. Using fuel evaporation rate per cycle which is determined in accordance with the temperature t v (t) (0 < v (t) ≦ 1), suction correction coefficient of each cylinder k _i a (0 <k _i ≦ 1) It can be calculated by the following equation.

[0024]

(Equation 3)

[0025] By using the thus sucked correction coefficient calculated by performing only auxiliary fuel injection T / k _i with respect to the basic injection quantity T in synchronism with the intake stroke of each cylinder, good auxiliary fuel A cylinder distribution can be obtained. As a result, as indicated by the polygonal line 803 in FIG.
The divided injection amount in the intake stroke of each cylinder can be calculated.

FIG. 10 shows the structure of an intake pipe according to a second embodiment of the present invention. In this example, in the intake pipe 904 of the in-cylinder direct-injection gasoline engine having six in-cylinders, the intake pipe branches into a Y shape downstream of the throttle valve 902 and is connected to the surge tank 904a at two points. 901
Indicates an auxiliary fuel injection device, and fuel is injected in the direction of arrow D. The basic control flow chart in the second embodiment is the same as that shown in FIG. 4, but is different from the first embodiment in that the engine has six cylinders.
A branch condition for the 5-cylinder and the # 6 cylinder is added. As a result,
Injection is performed as shown in the timing chart of FIG.

FIG. 12 shows the structure of an intake pipe 1103 according to a third embodiment of the present invention. The structure is basically the same as that of the first embodiment shown in FIG.
The volume of the branch portion 1104 after a is equal to or larger than the volume of one cylinder. In this case, as shown in FIG. 13, the main injection of each cylinder is stopped until the auxiliary injection fuel is predicted to reach each cylinder, for example, until the end of the first cycle, and the main injection is started from the second cycle. Injection 122
1, 1223, 1224 and 1222 are executed. As a result, due to the lack of fuel in the first cycle, HC
The flow chart of the control in the third embodiment, in which the discharge can be suppressed, can be executed by stopping the step 314 in the first cycle shown in FIG.

As described above, according to the present invention, a fuel injection device having good startability can be obtained.
Although the illustrated embodiment mainly describes an in-cylinder direct injection type internal combustion engine, the present invention is similarly applicable to an internal combustion engine in which main fuel is injected into an intake port.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing an example of an internal combustion engine.

FIG. 2 is a block diagram showing a system configuration of the present invention.

FIG. 3 is a diagram showing a partial configuration of a four-cylinder engine as an application target of the first embodiment of the present invention.

FIG. 4 is a flowchart of fuel injection control in the first embodiment.

FIG. 5 is a timing chart of fuel injection in the first embodiment.

FIG. 6 is a diagram illustrating factors for calculating an auxiliary fuel injection amount;

FIG. 7 is a diagram showing a distribution ratio of an auxiliary fuel injection amount to each cylinder.

FIG. 8 is a diagram illustrating another factor for calculating an auxiliary fuel injection amount.

FIG. 9 is a diagram showing a distribution ratio and an injection amount of auxiliary fuel to each cylinder.

FIG. 10 is a diagram showing a partial configuration of a six-cylinder engine to which a second embodiment of the present invention is applied.

FIG. 11 is a timing chart of fuel injection in the second embodiment.

FIG. 12 is a diagram showing a partial configuration of a four-cylinder engine to which a third embodiment of the present invention is applied.

FIG. 13 is a timing chart of fuel injection in the third embodiment.

[Explanation of symbols]

 100, 1305: In-cylinder direct fuel injection type internal combustion engine 101, 201, 901, 1101 ... Auxiliary fuel injection device 102, 202, 904, 1103 ... Intake pipe 103, 203, 902, 1102 ... Throttle valve 107: Main fuel injection device 109: fuel injection control device 110: crank angle detection device

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor: Kimitaka Saito, 14 Iwatani, Shimowasumi-cho, Nishio-shi, Aichi Prefecture Inside the Japan Automobile Parts Research Institute (72) Masaki Takeyama, 14 Iwatani, Shimowasumi-cho, Nishio-shi, Aichi Prefecture (72) Inventor Hironao Kishi 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Corporation F-term (reference) 3G301 HA01 HA04 JA03 JA05 KA01 LB04 LB05 LC01 MA01 MA11 MA19 MA23 NA09 NB14 ND02 ND37 NE03 NE08 NE11 NE12 NE23 PA11A PA11Z PB03A PB05A PE01Z PE04Z PF16Z

Claims (5)

[Claims] A main fuel injection means for injecting main fuel which is mixed with air branched from an intake pipe of an internal combustion engine and introduced into each cylinder and burned in a combustion chamber of each cylinder; A fuel injection control device for an internal combustion engine, comprising: an auxiliary fuel injection means for injecting fuel selectively; and a control means for controlling the main fuel injection means and the auxiliary fuel injection means. The auxiliary fuel injection timing is divided, the divided injection timing is synchronized with the intake timing of each cylinder, and the divided injection amount is corrected based on a preset auxiliary fuel intake rate for each cylinder, and the divided injection timing is adjusted. A fuel injection control device, wherein an injection amount for each injection timing is determined. 2. The intake rate of auxiliary fuel for each cylinder according to claim 1, wherein the auxiliary fuel injection means is installed in an intake pipe, the injection direction of the auxiliary fuel injection means, the injection strength, and the injection order of the cylinders. A fuel injection control device characterized in that prediction is made based on at least two or more products of an intake coefficient. 3. The intake rate of auxiliary fuel for each cylinder according to claim 1 or 2, wherein the intake rate of auxiliary fuel for each cylinder is determined by at least one of a rotation speed at the time of starting the internal combustion engine, an opening degree of an intake air amount adjustment valve, and air temperature. A fuel injection control device wherein the correction is made. 4. The fuel injection control device according to claim 3, wherein the intake rate of the auxiliary fuel in each cylinder is equalized by reducing the opening of the intake air amount adjusting valve. 5. A main fuel injection means for injecting main fuel which is mixed with air branched from an intake pipe of an internal combustion engine and introduced into each cylinder and burns in a combustion chamber of each cylinder, and an auxiliary fuel injection means into the intake pipe. A fuel injection control device for an internal combustion engine, comprising: an auxiliary fuel injection unit that injects fuel in a controlled manner; and a control unit that controls the main fuel injection unit and the auxiliary fuel injection unit. Immediately after the start of the start, the injection of the main fuel was stopped, the time required for the fuel to reach each cylinder after the injection of the auxiliary fuel was predicted, and the injection of the main fuel was started from the reached cylinder. Characteristic fuel injection control device.