JPH10306741A - Start time fuel injection control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve startability of an internal combustion engine by providing technique of determining the fuel injection quantity of high accuracy corresponding to the combustion state of each cylinder at the time of starting the internal combustion engine. SOLUTION: This start time fuel injection control device for an internal combustion engine is a device for controlling fuel injection at the time of starting the internal combustion engine provided with a plurality of cylinders, and is provided with a combustion state discriminating means for discriminating the combustion state of each cylinder at the time of starting the internal combustion engine, and a fuel injection quantity determining means for determining the fuel injection quantity of each cylinder according to the combustion state discriminated by the combustion state discriminating means. Ignitability of each cylinder and startability of the internal combustion engine can be improved by injecting the fuel injection quantity corresponding to the combustion state of each cylinder.

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 apparatus for an internal combustion engine, and more particularly to a technique for controlling fuel injection at the time of starting the internal combustion engine.

[0002]

2. Description of the Related Art In an internal combustion engine such as a gasoline engine, a fuel injection control device that determines a fuel injection amount in accordance with an operation state of the engine is used. In such a fuel injection control device, it is required to determine an optimal fuel injection amount at the time of starting the internal combustion engine and to improve the startability of the engine.

In response to such a demand, Japanese Patent Application Laid-Open No. 63-23 / 1988
A start-time fuel injection control device described in Japanese Patent No. 5633 is known. The start-time fuel injection control device includes a start-time detection unit that detects the start of the engine, a start-time basic injection time calculation unit that calculates a start-time basic injection time that is determined according to the coolant temperature, and detects an engine speed. Rotation speed detection means, correction coefficient calculation means for calculating a correction coefficient based on the engine rotation speed detected by the rotation speed detection means at the time of engine start, and correction for correcting the basic injection time at start using the correction coefficient Means for always maintaining the air-fuel ratio at the time of starting optimally, preventing fogging of the spark plug and the like, and improving the startability.

[0004]

However, in the above-described apparatus, the fuel injection amount is determined according to the engine speed. However, the combustion state of each cylinder, that is, whether the air-fuel mixture of each cylinder has ignited. Regardless of whether or not the fuel is corrected, the fuel injection amount of another cylinder is corrected based on the engine speed detected during the expansion stroke of a certain cylinder, which may deteriorate the startability.

For example, when the engine speed is detected during the expansion stroke of one cylinder, the engine speed is reflected in the fuel injection amount of the cylinder in which the next fuel injection is performed, and the air-fuel mixture in the one cylinder is reduced. When the engine speed increases due to ignition, the fuel injection amount of the cylinder in which fuel injection is performed next is reduced and corrected. For this reason, if the cylinder whose weight has been corrected has misfired in the previous cycle, since the inside of the cylinder is in a cold state, the fuel injected from the fuel injection valve is unlikely to evaporate, so that it is hard to vaporize on the wall of the intake passage or the cylinder. If the amount is corrected in this state, the air-fuel mixture in the cylinder will be in a lean state, and the ignitability of the air-fuel mixture and the startability of the internal combustion engine will be reduced.

Accordingly, the present invention has been made in view of the above problems, and provides a technique capable of determining a highly accurate fuel injection amount according to the combustion state of each cylinder when starting an internal combustion engine. Accordingly, it is an object to improve the ignitability of each cylinder and improve the startability of the internal combustion engine.

[0007]

The present invention employs the following means in order to solve the above-mentioned problems. That is,
The starting fuel injection control device for an internal combustion engine according to the present invention,
An apparatus for controlling fuel injection at the time of starting an internal combustion engine having a plurality of cylinders, comprising: a combustion state determining unit configured to determine a combustion state of each cylinder when the internal combustion engine is started; And a fuel injection amount determining means for determining a fuel injection amount of each cylinder in accordance with the performed combustion state.

The start-time fuel injection control device configured as described above sequentially injects fuel into each cylinder when the start of the internal combustion engine is started. Subsequently, the start-time fuel injection control device:
The combustion state in each cylinder is detected, and the next fuel injection amount of each cylinder is determined according to the detected combustion state. Here, for example, when fuel is ignited in a certain cylinder and a good combustion state occurs, the start-time fuel injection control device reduces the next fuel injection amount of the cylinder.

On the other hand, when the fuel does not ignite or misfire in a certain cylinder and the combustion state does not become good, the fuel injection control device at the time of starting increases the next fuel injection amount of the cylinder. As a result, an air-fuel mixture with a high air-fuel ratio (rich atmosphere) is formed in the cylinder, so that the ignitability is improved.

[0010] The above-described fuel injection control device for starting the internal combustion engine may further include, for each cylinder, a rotational speed detecting means for detecting an engine rotational speed after fuel injection. In this case, the combustion state determining means determines that the air-fuel mixture in the cylinder has ignited when the engine speed detected by the speed detecting means is higher than a predetermined number of times, and when the engine speed is equal to or lower than the predetermined number of times. Determines that the air-fuel mixture in the cylinder has misfired.

The fuel injection amount determining means reduces the fuel injection amount of the cylinder determined to be ignited by the combustion state determining means from the previous fuel injection amount, and the cylinder determined to be misfired by the combustion state determining means. Is increased from the previous fuel injection amount. In this case, since the amount of fuel injected into the misfired cylinder is increased, a rich air-fuel mixture is formed in the cylinder, and ignition becomes easy.

When determining the combustion state based on the engine speed as described above, it is preferable that the engine speed detecting means detects the engine speed during the expansion stroke of each cylinder. In other words, in the expansion stroke of each cylinder, when ignited in that cylinder, a large force is obtained by the combustion of the air-fuel mixture, and the engine speed is increased. However, when a misfire occurs in each cylinder, the explosive power due to the combustion of the air-fuel mixture is obtained. Since the engine speed is hardly increased, the combustion state in the cylinder, that is, ignition or misfire of the air-fuel mixture can be determined by referring to the engine speed in the expansion stroke.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a fuel injection control device for starting an internal combustion engine according to the present invention will be described with reference to the drawings.

FIG. 2 is a diagram showing a schematic configuration of an internal combustion engine to which the present invention is applied. The internal combustion engine shown in FIG. 1 is a four-cycle, four-cylinder internal combustion engine 1, to which a surge tank 3 is connected via an intake branch 2 and exhaust is provided via an exhaust branch 9. Tube 10 is connected.

The surge tank 3 is connected to an air cleaner box 5 via an intake pipe 4, takes in fresh air passing through the air cleaner box 5, and distributes and supplies the fresh air to each cylinder of the internal combustion engine 1 via an intake branch pipe 2. It is supposed to. An air flow meter 16 that outputs an electric signal corresponding to the mass of intake air flowing through the intake pipe 4 is attached to the intake pipe 4. A vacuum sensor 28 that outputs a signal is attached.

Subsequently, fuel injection valves 7a, 7b, 7c, 7d (hereinafter referred to as fuel injection valves 7) are provided in the respective branch pipes of the intake branch pipe 2.
The fuel distribution valve 6 is connected to these fuel injection valves 7. The fuel distribution pipe 6 distributes and supplies the fuel pressure-fed from a fuel pump (not shown) to the fuel injection valves 7 of the respective cylinders.

Each of the fuel injection valves 7 has a drive circuit 8a, 8
b, 8c, 8d (hereinafter collectively referred to as a drive circuit 8), and when a drive current from the drive circuit 8 is applied, the valve is opened and the fuel supplied from the fuel distribution pipe 6 is supplied to the intake branch pipe. Inject into 2.

Next, an exhaust purification catalyst 11 for purifying components such as NOx and HC contained in the exhaust gas discharged from the internal combustion engine 1 is provided in the exhaust pipe 10. An air-fuel ratio sensor 12 that outputs a current corresponding to the air-fuel ratio of exhaust gas flowing in the exhaust pipe is attached to the upstream exhaust pipe 10.

Subsequently, in the internal combustion engine 1, each time the crankshaft (not shown) rotates by a predetermined angle (for example, 10 degrees), the crank position sensor 17 for outputting an electric signal and the rotational position of the camshaft (not shown) are set to a predetermined value. Cam position sensor 1 that outputs an electrical signal when in position
8 and a water temperature sensor 19 that outputs an electric signal corresponding to the temperature of the cooling water.

The cam position sensor 18 is an electromagnetic pickup type sensor and outputs an electric signal before the compression top dead center of the reference cylinder. At this time, the cam position sensor 18 is, for example,
The signal output from the crank position sensor 17 immediately after the output of No. 8 is set to be 10 ° before the compression top dead center of the reference cylinder.

The air-fuel ratio sensor 12, the air flow meter 16, and the crank position sensor 17
And the cam position sensor 18 and the water temperature sensor 19
And the vacuum sensor 28 are connected to an electronic control unit (ECU) 15 for engine control, and output signals of the sensors are input to the ECU 15. Further, the starter switch 13, the ignition switch 14, and the battery 27 are connected to the ECU 15, and an ON / OFF signal of the starter switch 13, an ON / OFF signal of the ignition switch 14, and a voltage value of the battery 27 are input. It has become so.

As shown in FIG. 3, the ECU 15 includes a CPU 20, a ROM 21, a RAM 22, an input port 23, and an output port 24, which are interconnected by a bidirectional bus 25, and is connected to the input port 23. A / D converter (A / D) 26 is provided.

The input port 23 includes a cam position sensor 18, a crank position sensor 17, a starter switch 13, an ignition switch 14, and a battery 2.
7, and transmits these signals to the CPU 20 or the RAM 22. Further, the input port 23
Receives signals from the air flow meter 16, the air-fuel ratio sensor 12, and the water temperature sensor 19 via the A / D converter 26, and transmits these signals to the CPU 20 or the RAM 22.

The ROM 21 stores applications such as a start-up fuel injection control routine for determining a start-up fuel injection amount, a fuel injection control routine for determining a post-startup fuel injection amount, and an ignition timing control routine for determining an ignition timing. Stores programs and various control maps. The control map is, for example, a start-time fuel injection control map for determining a fuel injection amount when the internal combustion engine 1 is started, a fuel injection control map for determining a fuel injection amount after the start, and the like.

The RAM 22 stores an output signal from each sensor, a calculation result of the CPU 20, and the like. The calculation result is, for example, an engine speed calculated from an output signal of the crank position sensor 17. These data are
It is updated each time the crank position sensor 17 outputs a signal. Further, the RAM 22 stores the engine speed during the expansion stroke of each cylinder at the start of the internal combustion engine 1 (calculated from the time required for the crankshaft to rotate from compression top dead center to expansion bottom dead center of a certain cylinder). Engine speed).

The CPU 20 operates according to the application program stored in the ROM 21 and
The fuel injection amount and the fuel injection timing of each cylinder are calculated based on the output signal of each sensor and the control map stored in the AM 22, and the drive circuit 8 is controlled according to the calculated fuel injection amount and fuel injection timing.

At this time, if the internal combustion engine 1 is in a normal operation state, the CPU 20 executes a fuel injection control routine stored in the ROM 21 and
A basic fuel injection amount is calculated in accordance with the engine speed calculated from the output signal of (1) and the output signal (electric signal corresponding to the intake air mass) from the air flow meter 16. Then, the CPU 20 corrects the basic fuel injection amount according to the operating state, and calculates the fuel injection amount (valve opening time of the fuel injection valve 7) TAU of each cylinder.

The fuel injection amount TAU is calculated using, for example, the following equation: TAU = TP × FAF × K + TV (1)

In the above equation (1), TP represents a basic fuel injection amount determined according to a value Q / N obtained by dividing an intake air amount Q by an engine speed N, and FAF represents an air-fuel ratio. K represents an air-fuel ratio feedback correction coefficient determined by the output signal of the sensor 12, K represents a correction coefficient such as a warm-up increase or an acceleration / deceleration increase, and TV represents an invalid injection time determined by an operation delay of the fuel injection valve 7. Represent. The basic fuel injection amount and each correction coefficient are previously stored in a RO injection map as a RO injection map.
It is stored in M21.

Next, when the internal combustion engine 1 is in the starting state, the CPU 20 executes a starting fuel injection control routine stored in the ROM 21, and for each cylinder according to the combustion state of the immediately preceding cycle. Determine the fuel injection amount. At that time, when the ON signal of the starter switch 13 is input, the CPU 20 determines the compression top dead center of each cylinder of the internal combustion engine 1 based on the output signals of the crank position sensor 17 and the cam position sensor 18, and determines the compression top dead center during the expansion stroke of each cylinder. And the calculated engine speed is stored in the RAM 22 for each cylinder.
In a predetermined area. Next, when determining the fuel injection amount of each cylinder in the next cycle, the CPU 20 sets R
The engine speed stored in the AM 22 is read, and a basic fuel injection amount at start (basic fuel injection time at start): KNEINJ corresponding to the engine speed is calculated. The correction is made according to (cooling water temperature, battery voltage, intake pressure, etc.), and the starting fuel injection amount: TAU in the next cycle of each cylinder is calculated.

In this case, the starting fuel injection amount: TAU
Is calculated, for example, using the following expression: TAU = KNEINJ × KA × KB (2)

In the above equation (2), the correction coefficients KA, K
B is a correction coefficient determined according to the battery voltage, the intake pressure, and the like. Then, the starting basic fuel injection amount: KNEI
NJ is a ROM for fuel injection control at start-up
21 is stored. This starting fuel injection control map is
As shown in FIG. 4, the engine speed during the expansion stroke: NE
And a basic fuel injection amount at start-up: KNEINJ. The basic fuel injection amount at start-up: KNEINJ is set to decrease as the engine speed NE in the expansion stroke increases.

According to the above equation (2) and the map shown in FIG. 4, if the engine speed in the expansion stroke of the Nth (N: natural number) cycle of a certain cylinder is NEn, the fuel in the (N + 1) th cycle The injection amount: KNEINJn + 1 is determined by the engine speed NEn in the Nth cycle, and the fuel injection amount in the N + 2th cycle: KNEINJn + 2 is obtained by the engine speed NEn + 1 in the expansion stroke in the N + 1th cycle. When the mixture in the cylinder ignites normally in the (N + 1) th cycle, the engine speed NEn + 1 in the (N + 1) th cycle becomes higher than the engine speed NEn in the (N) th cycle.
Basic fuel injection amount at start of the second cycle: KNEINJn +
2 is the basic fuel injection amount at the start of the (N + 1) th cycle: KN
It is reduced from EINJn + 1.

On the other hand, if the air-fuel mixture in the cylinder fails to ignite normally in the (N + 1) th cycle and fails, the engine speed NEn + 1 in the (N + 1) th cycle becomes lower than the engine speed NEn in the (N) th cycle, and the (N + 2) th cycle. Basic fuel injection amount at start of engine: K
NEINJn + 2 is increased from the starting basic fuel injection amount: KNEINJn + 1 in the (N + 1) th cycle.

For example, in the case of a four-stroke, four-cylinder internal combustion engine, as shown in FIG. 1, when the engine speed NE # 1 in the expansion stroke of the first cycle of the first cylinder # 1 increases, the first cylinder ## 1 is considered to be fired, and the fuel injection amount in the second cycle is reduced from that in the first cycle. On the other hand, the third cylinder #
If the engine speeds NE # 3, NE # 4, and NE # 2 in the first cycle of the third and fourth cylinders # 4 and # 2 are low, the second cylinder # 2
And # 3 cylinder # 3 and # 4 cylinder # 4 are considered misfired,
The fuel injection amount in the second cycle is increased from that in the first cycle.

As described above, the application programs of the CPU 20 and the ROM 21 realize the fuel injection amount determining means and the combustion state determining means according to the present invention, and the CPU 20 and the crank position sensor 17 realize the rotational speed detecting means according to the present invention. .

<Operation and Effect of Embodiment> The operation and effect of the fuel injection control device for starting the internal combustion engine according to this embodiment will be described below.

When the internal combustion engine 1 is started, the CPU 20
Receives the ON signal of the ignition switch 13 and the ON signal of the starter switch 14, determines that the internal combustion engine 1 is in the starting state, and performs the cylinder determination process.

In the cylinder discriminating process, the CPU 20 first detects the compression top dead center of the reference cylinder from the output signal of the cam position sensor 18 and the output signal of the crank position sensor 17, The compression top dead center of other cylinders is detected according to the output signal.

After determining the compression top dead center of each cylinder, the CPU 20 executes a cylinder-by-cylinder rotational speed calculation routine shown in FIG. First, the CPU 20 measures the time required from when the crank position sensor 17 outputs the signal indicating the compression top dead center of each cylinder to when it outputs the signal indicating the expansion bottom dead center (S501). A corresponding engine speed is calculated (S502).

Subsequently, the CPU 20 compares the engine speed calculated in S502 with the engine speed during the expansion stroke of each cylinder:
NE is stored in a predetermined area of the RAM 22 (S5).
03).

Next, the CPU 20 determines the fuel injection amount of each cylinder, that is,
Outputs a signal indicating a predetermined position, a start-time fuel injection amount control routine shown in FIG. 6 is executed.

In the starting fuel injection amount control routine, the CPU 20 first determines a cylinder for which the fuel injection amount is to be determined (S601). At this time, the CPU 20 determines the cylinder for which the fuel injection amount is to be determined with reference to a counter that stores the identification number (for example, the cylinder number) of the cylinder for which the fuel injection amount is to be determined. The counter is updated every time the crankshaft rotates a predetermined angle. For example, in the case of a four-cylinder internal combustion engine, every time the crankshaft rotates 180 degrees, the first cylinder # 1 → the third cylinder # 3 → the fourth Cylinder # 4 →
.. Are updated in the order of the second cylinder # 2 → the first cylinder # 1.

Next, the CPU 20 accesses a predetermined area of the RAM 22 and reads out the engine speed NE in the expansion stroke of the previous cycle of the cylinder determined in S601 (S602). Next, the CPU 20 accesses the start-time fuel injection control map in the ROM 21, and determines the basic start-time fuel injection amount: KNEIN corresponding to the engine speed: NE.
J is calculated (S603).

Subsequently, the CPU 20 calculates various correction coefficients (KA, KB) based on the battery voltage, the intake pressure and the like stored in the RAM 22 (S604). And C
The PU 20 calculates the basic fuel injection amount at start: KNEINJ and the correction coefficient: K calculated in S603 and S604.
A and KB are expressed by equation (2): TAU = KNEINJ × KA × K
B, and the fuel injection amount: TAU of the cylinder is calculated (S605).

The fuel injection amount thus calculated: T
The AU outputs the drive circuit 8 corresponding to the cylinder via the output port 24 at a predetermined time (when the fuel injection is performed in synchronization with the intake stroke of each cylinder, the start timing of the intake stroke of each cylinder).
Sent to. Then, the drive circuit 8 applies a drive current to the fuel injection valve 7 of the cylinder according to the fuel injection amount: TAU to perform fuel injection.

As described above, according to the present embodiment, when the internal combustion engine 1 is started, the fuel injection amount is determined according to the combustion state of each cylinder, so that the fuel injection amount of the normally ignited cylinder is reduced. As a result, over-injection can be prevented, and the ignitability can be improved by increasing the fuel injection amount of the misfired cylinder.

Therefore, the starting fuel injection control device according to the present embodiment accurately injects the fuel amount required by each cylinder when the internal combustion engine is started, without being affected by the combustion state of the other cylinders. And startability can be improved.

[0049]

According to the present invention, when starting the internal combustion engine,
Since the combustion state in each cylinder is detected, and the amount of fuel required by each cylinder is accurately determined according to the detected combustion state, the fuel injection amount of a cylinder with a good combustion state is reduced, and the combustion state is not good. The ignitability can be improved by increasing the fuel injection amount of the cylinder, and the startability of the internal combustion engine can be improved.

[Brief description of the drawings]

FIG. 1 is a timing chart showing a relationship between an engine speed and a fuel injection amount during an expansion stroke of each cylinder.

FIG. 2 is a diagram showing a schematic configuration of an internal combustion engine to which the fuel injection control device for starting the internal combustion engine according to the present invention is applied;

FIG. 3 is a block diagram showing an internal configuration of an ECU.

FIG. 4 is a diagram showing a specific example of a map showing a relationship between a basic fuel injection amount at start and an engine speed;

FIG. 5 is a diagram showing a control flow for calculating the rotational speed for each cylinder.

FIG. 6 is a diagram showing a fuel injection control flow for each cylinder.

[Explanation of symbols]

 1. Internal combustion engine 15. ECU 20. CPU 21. ROM 17. Crank position sensor 18. Cam position sensor

Claims (3)

[Claims] 1. A start-time fuel injection control device for controlling fuel injection at the time of starting an internal combustion engine having a plurality of cylinders, wherein a combustion state determining means for determining a combustion state of each cylinder at the time of starting the internal combustion engine. And a fuel injection amount determining means for determining a fuel injection amount for each cylinder according to the combustion state determined by the combustion state determining means. 2. The engine according to claim 1, further comprising: a rotation speed detection unit configured to detect an engine rotation speed after fuel injection for each cylinder of the internal combustion engine, wherein the combustion state determination unit detects the engine rotation speed detected by the rotation speed detection unit. If the number is higher than a predetermined number of revolutions, it is determined that the air-fuel mixture in the cylinder has ignited, and if the number is less than the predetermined number of rotations, it is determined that the air-fuel mixture in the cylinder has misfired, and the fuel injection amount determining means Reduces the fuel injection amount of the cylinder determined to be ignited by the combustion state determining means from the previous fuel injection amount, and reduces the fuel injection amount of the cylinder determined to be misfired by the combustion state determining means to the previous fuel injection amount. 2. The fuel injection control device for starting an internal combustion engine according to claim 1, wherein the fuel injection control device increases the fuel injection amount. 3. The start-up fuel injection control device for an internal combustion engine according to claim 2, wherein said engine speed detecting means detects an engine speed during an expansion stroke of each cylinder.