JPH0615842B2 - Fuel injection timing control device for internal combustion engine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a fuel injection timing control device for an internal combustion engine, and more particularly, to a fuel injection control timing for a multi-cylinder internal combustion engine based on an operating state of the internal combustion engine. The present invention relates to a fuel injection timing control device for an internal combustion engine, which performs correction based on a variation amount and performs fuel injection timing control for each cylinder independently.

[Prior Art] In recent years, electronic control and refinement of control of an internal combustion engine are rapidly progressing. One of them is to provide an electromagnetic fuel injection valve for each cylinder of a multi-cylinder internal combustion engine to There is an electronic fuel injection control device (EFI) that precisely controls the fuel injection amount and the fuel injection timing for each cylinder based on the operating state. When such multi-cylinder independent fuel injection is performed, the upper limit of the lean side of the air-fuel ratio of the air-fuel mixture can be significantly increased as shown in FIG. 9, so-called lean burn combustion can be suppressed with fluctuations in the output of the internal combustion engine. It is known to be feasible. That is,
It is expected that the fuel consumption rate of the internal combustion engine will be greatly improved.

This is because when focusing on a cylinder that is currently in the intake stroke, if the end of fuel injection into that cylinder ends at a predetermined time before the end of the intake stroke, both the tor fluctuation and the amount of oxynitride (NOx) generated are combined. This is because it is possible to make it below the allowable limit. This is because the fuel injected just before the end of the intake stroke makes the air-fuel ratio of the air-fuel mixture in the upper part of the cylinder relatively small, so that the ignitability and the combustion propagating property are improved and the fluctuation of the internal combustion engine output is made small. However, if the end of fuel injection is delayed too much, the generation of NOx will increase and exceed the allowable limit.

Therefore, the operating state of the internal combustion engine, for example, the fuel injection start timing of the internal combustion engine is determined by a map or a calculation formula that is set in advance using the rotational speed and the intake air amount as parameters, that is, the fuel injection end timing of the internal combustion engine. There has also been proposed a fuel injection timing control device for an internal combustion engine that controls the fuel injection timing to each cylinder of a multi-cylinder internal combustion engine so that a predetermined time is reached before the end of the intake stroke (for example, JP-A-56-56). 57929).

[Problems to be Solved by the Invention] Against the background of such conventional techniques, the problems to be solved by the present invention are as follows.

(1) FIG. 10 is a diagram showing the relationship between the end timing of fuel injection, the fluctuation of the output torque of the internal combustion engine, and the generation of NOx. It can be seen that the torque fluctuation and the generation of NOx have a contradictory relationship with the fuel injection end timing (here, shown as the ATDC crank angle from the top dead center before intake start). Therefore, when the respective allowable limits are set as shown in the figure, the practical range is about ATDC 60 ° CA to 75 ° CA.

The control that puts the end of the fuel injection timing within this range is
For example, it is performed with reference to a signal from a crank angle sensor or the like which is provided in a distributor and generates a pulse by the rotation of a crank shaft. However, there is a machine difference in the assembly of such a crank angle sensor, and if the adjustment is not performed sufficiently, the crank angle detection will deviate from the actual stroke of the cylinder, and the end of the actual fuel injection timing will be the true intake. There was a problem that it may not be able to enter 60 ° to 75 ° CA before the top dead center (ATDC) before the stroke. This is considered to be a problem in an internal combustion engine having a large number of cylinders even when the strokes of the cylinders are deviated from the uniform allocation.

(2) The torque fluctuation and NOx generation characteristics of the internal combustion engine as shown in FIG. 10 may change as the internal combustion engine is used. Therefore, even if the fuel injection is always terminated at the same predetermined angle of ATDC, due to changes over time,
There has been a problem that either the fluctuation amount of the output of the internal combustion engine or the generation amount of NOx may exceed the allowable limit.

The present invention has been made to solve the problems (1) and (2) described above, and it is preferable that the output of an internal combustion engine that performs independent fuel injection in each cylinder and the generation of NOx are independent of machine differences and changes over time. An object of the present invention is to provide an excellent fuel injection timing control device for an internal combustion engine that is controlled.

Structure of the Invention [Means for Solving the Problem] In order to achieve the above object, the present invention has the following structure as a means for solving the above problem. That is, as shown in FIG. 1, the fuel injection timing is determined by using the operating state of the internal combustion engine M1 detected by the operating state detecting means M2 of the internal combustion engine M1 as a parameter, and each cylinder of the internal combustion engine is based on the fuel injection timing. A fuel injection timing control device for a spark ignition type internal combustion engine, comprising a fuel injection control means M3 for independently injecting fuel, wherein at least one of a rotational speed of the internal combustion engine, an output torque, and an oxygen concentration in exhaust gas is within a predetermined time. Variation detecting means M4 for detecting the variation representing the engine roughness, and when the detected variation is greater than or equal to the target value, the predetermined fuel injection timing is corrected to the retard side, and when the variation is less than or equal to the target value, the progress is advanced. This is the configuration of a fuel injection timing control device for an internal combustion engine, which is provided with a correcting means M5 for correcting the angle side.

Here, the operating state of the internal combustion engine M1 is information necessary for determining the basic fuel injection amount and the fuel injection start timing of the internal combustion engine so that the fuel injection is ended at a predetermined timing, and for example, the internal combustion engine M1. Of the intake pipe pressure and the number of revolutions, or the amount of intake air and the number of revolutions. The operating state detecting means M2 for detecting such an operating state includes an internal combustion engine M1.
Coil angle sensor for detecting the number of revolutions of the internal combustion engine M1, a vane type, a hot wire type, a Kalman type intake air for detecting the number of revolutions of the internal combustion engine M1 provided with a coil facing a rotor that rotates in conjunction with the crankshaft of Various well-known sensor groups such as a quantity sensor, a pressure sensor of a semiconductor type or a diaphragm / strange gauge type for detecting an intake pipe negative pressure, and the like can be considered.

The fuel injection control means M3 determines the fuel injection timing from the operating state of the internal combustion engine M1, and is the above-mentioned internal combustion engine M1.
The fuel injection timing is obtained from the map and the calculation formula using the rotation speed and load of the engine as parameters. Conventionally, this is configured by a logical operation circuit centering on a microcomputer mounted in the EFI of the internal combustion engine 1, a discrete operation circuit using charge / discharge time of a capacitor, and the like.
When a microcomputer is used, it may be configured with a part or all of a correction unit M5 and a variation amount detection unit M4, which will be described later, and in this case, by a process of a predetermined procedure performed according to a predetermined program. , Each means is realized.

The fluctuation amount detecting means detects the fluctuation amount of the operating state of the internal combustion engine M1, and detects the fluctuation amount from, for example, fluctuations in the rotational speed of the internal combustion engine M1, fluctuations in output torque, fluctuations in the air-fuel ratio, and the like. . As described above, such variation amount detecting means M4 can also be realized by a method of sequentially reading the rotation speed NE by a microcomputer and calculating the variation amount.

The correction means M5 is based on the fluctuation amount of the operating state of the internal combustion engine M1 detected by the fluctuation amount detection means M4.
It is a means for correcting the fuel injection timing determined by the fuel injection control means M3. For example, the fuel injection end timing is corrected so as to suppress the output torque fluctuation to a predetermined magnitude according to the fluctuation amount of the output torque. Although various correction methods are conceivable, an optimum method may be selected according to the mode of the applied internal combustion engine M1 and its operating state detection means M2 and variation amount detection means M4. For example, a limit is set for each of the advance side and the retard side of the fuel injection timing, and if any fluctuation in the rotational speed, output torque, or oxygen concentration in the exhaust gas increases during this period, the limit decreases. In that case, a method of correcting each angle toward the advance side can be considered.

[Operation] In the fuel injection timing control device for an internal combustion engine of the present invention having the above-described configuration, the basic fuel injection timing is set by using the operating state of the internal combustion engine M1 as a parameter, and the variation amount of the operating state of the internal combustion engine M1 is set. It works to correct this according to. Therefore, for example, in the case where the variation amount of the operating state of the internal combustion engine M1 exceeds a permissible limit at a predetermined fuel injection timing due to a machine difference of the internal combustion engine M1 or the operating state detecting means M2 thereof, a change over time, or the like. However, the fuel injection timing is corrected according to the amount of fluctuation to reduce the fuel injection timing.

Embodiments Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 2 is a schematic configuration diagram of a fuel injection control device for an internal combustion engine as an embodiment of the present invention, and FIG. 3 is a system diagram of an electric system centering on a block diagram of an electronic control circuit. In the figure,
Reference numeral 20 denotes a 4-cylinder 4-cycle spark ignition type engine, the intake air of which is sucked into each cylinder from upstream through an air cleaner 21, an air flow meter 22, an intake pipe 23, a surge tank 24, and an intake branch pipe 25. On the other hand, the fuel is pumped from a fuel tank (not shown) and injected / supplied from the fuel injection valves 26a, 26b, 26c, 26d provided in the intake branch pipe 25. The fuel injection is controlled by an electronic control circuit 28 which operates by receiving electric power from a battery 27 via a key switch 27a, and the electronic control circuit 28 is detected by a rotation speed sensor 30 provided in a distributor 29. The basic fuel injection amount and the fuel injection timing are obtained from the rotational speed of the engine 20 and the intake air amount obtained by the method described below from the output signals of the air flow meter 22, the throttle sensor 32, and the rotational speed sensor 30, and fuel injection control is performed. Is configured. The actual fuel injection amount is calculated by correcting the basic fuel injection amount with various correction factors, such as the water temperature THW of the engine 20 cooling water detected by the water temperature sensor 33. The control of the fuel injection timing will be described later with reference to FIGS. 5 and 6.

The rotation speed sensor 30 is provided so as to face a ring gear that rotates in synchronization with the crankshaft of the engine 20, and outputs a pulse signal having a frequency proportional to the engine rotation speed. Further, the water temperature sensor 33 is composed of a temperature sensitive element such as a thermistor and detects the cooling water temperature representing the temperature of the engine. Although not shown in the figure, the distributor 29 has four ignition plugs for each cylinder and an ignition circuit 3
It supplies the high voltage ignition signal generated at 5. The ignition circuit 35 is controlled by the electronic control circuit 28, and the ignition timing, the energization time, etc. are instructed by the electronic control circuit 28. The ignition circuit 35 is composed of an igniter and an ignition coil.

Next, the configuration of the electronic control circuit 28 will be described with reference to FIG. In the figure, 100 is a central processing unit (CPU) that calculates ignition timing, fuel injection amount, etc. according to a predetermined program, 101 is a pulse input circuit for inputting a pulse signal from the rotation speed sensor 30, and 102 is a pulse input circuit. An interrupt control circuit for generating an interrupt signal at a predetermined crank angle by a pulse signal inputted by
Is a timer for measuring time, 105 is a read-only memory (RO for storing programs and data in advance)
M), 106 are readable and writable memories (RAM) for temporarily storing data and the like, and 108 is the key switch 27.
backup RAMs 110a, 110b, 110c, which maintain the contents of stored data even after a is turned off,
110d is an output circuit for driving the fuel injection valves 26a to 26d, 112 is an output circuit for driving the ignition circuit 35, and 1 is an output circuit.
Reference numeral 14 is an A / D conversion input circuit for converting the analog signals from the air flow meter 22, water temperature sensor 33, and throttle sensor 32 into a digital value and inputting the signal, and 116 is supplied with electric power from the battery 27 via the key switch 27a A power supply circuit that supplies a constant voltage to the entire control circuit 28, 1
18 is the battery 2 without the key switch 27a
7 is another power supply circuit which is connected to 7 and supplies electric power to the backup RAM 108, and 120 is a data bus which connects the above circuits to each other. Output circuits 110a to 1
00d is equipped with a counter (not shown), and CUP
The fuel injection timing τ is set by 100, and C is also set.
When the fuel injection start signal from the PU 100 is input, the corresponding fuel injection valve (26a to 26d) is opened,
At the same time, the countdown is started, and the fuel injection valve is opened to control the fuel injection amount until the countdown becomes zero. Also, A / D
The conversion input circuit 114 is equipped with a successive approximation type (high-speed A / D conversion time of several + μsec) not shown, and the intake air amount signal AFM from the air flow meter 22 and the cooling water temperature signal THW from the water temperature sensor 33 are provided. The opening degree signal TA of the throttle valve 27 from the throttle sensor 32 can be A / D converted and read.

Next, the operation of the fuel injection amount control system for the internal combustion engine having the above-mentioned configuration will be described with reference to FIGS. 4, 5, and 6. FIG. 4 is a flow chart showing a basic control routine executed in the fuel injection control device for an internal combustion engine, and FIG. 5 is a flow chart showing an NE interrupt routine which is activated at every predetermined crank angle to control fuel injection. FIG. 6 is a flowchart of a fuel injection start timing calculation routine showing the details of the process of calculating the fuel injection start timing in the NE interrupt routine.

When the key switch 27a is turned on and the engine 20 is started, the CPU 100 of the electronic control circuit 28 starts the control routine shown in FIG.

First, at step 200, initialization processing such as clearing the internal register of the CPU 100 is performed. In the following step 210, the intake air amount Q to the engine 20, the rotational speed NE, the cooling water temperature THW indicating the warm-up state, the throttle opening Ta, etc. are read from the respective signals as the operating state of the engine. Among the variables indicating these operating states read in step 210, the rotational speed NE of the engine 20 is the rotational speed sensor 3 every 30 ° CA.
The interval of the pulse signal generated at 0 can be calculated by detecting the interval between the input circuit 101 and the interrupt control circuit 102 and taking the reciprocal thereof. Further, the intake air amount Q detected by the air flow meter 22 and the water temperature sensor 33
The cooling water temperature THW detected by and the throttle opening Ta detected by the throttle sensor 32 are both converted into digital values by the A / D converter of the A / D conversion input circuit 114.

Step 220 following Step 210 is an ignition timing calculation routine for obtaining an ignition timing using a map from the engine speed and the engine load amount (for example, Q / NE).
Further, step 230 is a fuel injection amount calculation routine for calculating the fuel injection amount using calculation or a map based on the engine speed, the intake air amount and other engine parameters. Although the electronic control circuit 28 repeatedly executes the above steps 210 to 230, each routine is well known and will not be described in detail.

Incidentally, a well-known ignition timing control routine for driving the ignition circuit 35 via the output circuit 112 at the timing actually obtained, or the fuel injection valves 26a to 26d to the output circuit 110a.
A well-known fuel injection amount control routine or the like for opening and controlling the valve via 110d is processed as an NE interrupt routine which is activated at every predetermined crank angle by a pulse signal from the rotation speed sensor 30.

Therefore, the NE interrupt routine will be described below with reference to FIG. The NE interrupt routine is started by the pulse signal from the rotation speed sensor 30, and the processing is started from step 300. First, at step 300, control other than fuel injection control is performed in cycles of engine rotation, such as ignition timing control,
Calculation of the engine speed NE and indexing of the current engine crank angle Nθ are executed. Continued Step 3
At 10, it is determined whether the engine crank angle Nθ obtained at step 300 is the timing at which the preset injection start timing should be calculated. The timing at which this injection start timing should be calculated must be earlier than the injection start time, but it is desirable to be later in order to calculate with the latest information as much as possible.

When it is determined in step 310 that it is the timing to calculate the injection start timing, the process proceeds to step 320, and the engine speed NE obtained in step 300 is determined.
Then, the injection start timing θ is calculated from the fuel injection time τ. The calculation of the fuel injection start timing θ performed in step 320 will be described later in detail with reference to the flowchart of FIG.

After the processing of step 320, or when it is determined in step 310 that it is not the timing for calculating the fuel injection start timing, the processing proceeds to step 330 and fuel injection control is executed. Specifically, each output circuit 110a-11
A process of setting the latest fuel injection time τ in the counter within 0d, or giving a fuel injection start signal to the fuel injection valve (any of 26a to 26d) which has reached the fuel injection start timing θ calculated in step 320. Do. After the above processing, the process goes to RTN, and this NE interrupt routine ends.

Next, details of the fuel injection start timing calculation performed at step 320 in the NE interrupt routine will be described with reference to the flowchart of FIG. Note that α used in the following description means the crank angle from the end of fuel injection to the bottom dead center (BDC) after the intake stroke of that cylinder when focusing on one cylinder, and δ is Engine 20
The rotational fluctuation rate obtained from the fluctuation of the rotational speed NE of is shown. Here, this rotation fluctuation rate is treated as a fluctuation amount of the operating state of the engine 20, but here it is treated as synonymous with the engine roughness degree that means the fluctuation rate of the output torque.

This routine starts the processing from step 400, and the processing in each step will be described first.

Step 400: Lower limit value αmi of the injection end crank angle α
Perform the process to find n. The lower limit value αmin is obtained from the map shown in FIG. 7, and this value is preset from the allowable limit of NOx in FIG.
Is set as a crank angle with respect to, and is stored in the ROM 105.

Step 410: Variation rate δ of the engine speed NE of the engine 20
Is used to determine whether or not a condition for starting the fuel injection timing control, that is, the feedback control based on the rotation variation rate δ of the fuel injection end timing (hereinafter also referred to as roughness control) is satisfied. This determination is made based on the cooling water temperature THW of the engine 20, etc. If it is determined that the engine 20 is cold, the roughness control is not performed and the process proceeds to step 420. When it is determined that step 430
Move to.

Step 420: Lower limit value αmin obtained in Step 410
Is added to a predetermined value, for example, 10 ° CA, to perform the processing for obtaining the injection end crank angle α.

Step 430: The roughness degree δ is calculated from the fluctuation of the engine speed NE of the engine 20. Here, the roughness degree δ is calculated as δ = (ΔNE / NE) × 100 (1) In addition, ΔNE is the number of revolutions N within a predetermined time.
The deviation between the upper limit and the lower limit of E, NE means the average value of the number of revolutions at that time.

Step 440: Roughness degree δ obtained in step 430
Determines whether or not exceeds the target roughness degree δref. In this case, the target roughness degree Δref is set in advance as an upper limit of a value which is considered to be preferable for the passengers in terms of experience.

Step 450: A process of increasing the injection end crank angle α by 1 ° CA is performed.

Step 460: A process of subtracting 1 ° CA from the injection end crank angle α is performed.

Step 470: It is judged whether or not the injection end crank angle α increased by 1 ° CA in step 450 is larger than the upper limit value αmax. This upper limit value αmax is the roughness degree δ
Is a value set in order to prevent an over-advanced angle in the injection end timing control due to erroneous calculation of.

Step 480: It is judged whether or not the injection end crank angle α, which is subtracted by 1 ° CA in step 460, exceeds the lower limit value αmin.

Step 490: The injection end crank angle α is set to the upper limit value αmax
Perform the process.

Step 500: Lower injection limit crank angle α to lower limit αmin
Perform the process.

Step 510: Fuel injection start timing θ from the engine speed NE of the engine 20, fuel injection time τ, injection end crank angle α
Is calculated by the following equation (2).

θ = τ × NE × 360/60000 + α (2) where θ is the crank angle before the bottom dead center after the intake stroke (° B
BDC), these various quantities α, τ, N
The relationship between E and θ is schematically shown in FIG. In the figure,
τ is the fuel injection time, but is shown corresponding to the crank angle for convenience.

In the present routine configured as shown in FIG. 6 from the steps described above, the following control is performed.

(1) When the roughness control cannot be performed because the engine 20 is cold or the like, the fuel injection end timing is set to the lower limit value α.
The fuel injection start timing θ is calculated as an angle with a 10 ° CA margin from min (step 400-step 410-
Step 420-Step 51-NEXT).

(2) If the roughness control can be performed, it is determined whether the current roughness degree δ of the engine 20 is larger than the target value δref (step 400-step 410-step 430-step 440), and (2- a) When the roughness degree δ is less than the target value δref, the injection end crank angle α is 1 within the upper limit value αmax.
.Degree. CA, and the crank angle .alpha. Is used to calculate the fuel injection start timing .theta. (Step 440-step 450).
-Step 470-Step 480 or Step 4
90-step 510-NEXT), (2-b) When the roughness degree δ is larger than the target value δref, the injection end crank angle α is set to 1 within the lower limit value αmin.
° CA is subtracted, and the fuel injection start timing θ is calculated using the injection end crank angle α (step 440-step 460-step 480- (step 500) -step 510-NEXT), and as a result, the engine 20 The fuel injection end timing is controlled to be within the allowable limit of NOx and within the allowable limit of roughness degree.

In the present embodiment configured as described above, the fuel injection end timing is not fixed at a predetermined crank angle,
The operating state of the engine 20, here, the base injection end crank angle αmin determined from the rotational speed NE, is set to the roughness degree δ.
Based on the above, the control is performed so that the generation of NOx and the engine roughness, that is, the rotational fluctuation rate in this case, are set within the allowable limits. Therefore, the optimum fuel injection timing can be obtained according to the machine difference of the engine 20, the rotation speed sensor 30 and the like and the change over time due to the use of the engine 20, and the fuel injection can be executed by knowing the fuel injection start timing θ. it can. As a result, even when the engine 20 is operated with a lean air-fuel mixture, it is possible to maintain a low engine roughness while always suppressing the generation of NOx, and to maximize the performance of the engine 20 with independent cylinder fuel injection, The engine 20 can be driven while maintaining a good riding comfort, and fuel consumption is also improved.

Although one embodiment of the present invention has been described above, the present invention is not limited to this embodiment. For example, the target value δ of the roughness degree of the engine 20 is set to the target value δ of the roughness degree of the engine 20. According to the operating state (discrimination of idle, rotation speed, load, etc.), or control is performed by changing the output torque or the oxygen concentration in the exhaust gas instead of the rotational fluctuation rate. Needless to say, the present invention can be implemented in various modes without departing from the scope of the present invention.

Effects of the Invention As described above in detail, according to the fuel injection timing control system for an internal combustion engine of the present invention, the generation and output of NOx of the internal combustion engine can be performed irrespective of machine differences and changes with time of the internal combustion engine and various sensors. It is possible to suppress fluctuations within an allowable limit, and it is possible to bring out an excellent effect that characteristics of an internal combustion engine that performs multi-cylinder independent fuel injection with a lean mixture can be maximized.
Therefore, the ride comfort of the passenger can be kept good, the exhaust gas can be sufficiently purified, and the fuel consumption can be greatly improved.

[Brief description of drawings]

FIG. 1 is a basic configuration diagram of the present invention, and FIG. 2 is a schematic configuration diagram of a fuel injection control device for an internal combustion engine as an embodiment of the present invention.
FIG. 3 is a system diagram of an electric system centering on a block diagram of the electronic control circuit, and FIG. 4 is a flowchart showing a basic control routine executed in the fuel injection control device for the internal combustion engine of the embodiment. FIG. 6 is a flow chart showing the NE interrupt routine, FIG. 6 is a flow chart showing the process of calculating the fuel injection start timing θ, FIG. 7 is a graph for obtaining the lower limit value α min of the fuel injection end timing, and FIG. 8 is the fuel injection start. A schematic diagram showing the relationship between the timing θ and the injection end crank angle α, the fuel injection amount τ, etc., FIG. 9 is a graph showing the relationship between the air-fuel ratio and the fluctuation of the output torque, and FIG. 10 is a graph showing the output torque fluctuation and NOx. 3 is a graph showing the occurrence and the timing of the end of fuel injection. 20 ... Engine 22 ... Air flow meter 26a, 26b, 26c, 26d ... Fuel injection valve 28 ... Electronic control circuit 30 ... Rotation speed sensor 33 ... Water temperature sensor 35 ... Ignition circuit 100 ... CPU 110a, 110b , 110c, 110d ... Output circuit

Claims (1)

[Claims] 1. A fuel for which a fuel injection timing is determined by using an operating state of the internal combustion engine detected by an operating state detecting means of the internal combustion engine as a parameter, and fuel is independently injected into each cylinder of the internal combustion engine based on the fuel injection timing. In a fuel injection timing control device for a spark ignition type internal combustion engine having an injection control means, a rotational speed of the internal combustion engine, an output torque, a variation amount representing an engine roughness within a predetermined time of at least one of oxygen concentrations in exhaust gas, A fluctuation amount detecting means for detecting, and a correcting means for correcting the predetermined fuel injection timing to the retard side when the detected fluctuation amount is equal to or more than the target value, and to the advance angle side when the detected fluctuation amount is less than or equal to the target value. A fuel injection timing control device for an internal combustion engine, comprising: