JPS6088841A - Air-fuel ratio controller for internal-combustion engine - Google Patents

Abstract

PURPOSE:To accurately control the injected quantity of fuel when the operation of an engine is unstable, by compensating the basic injected quantity of fuel by a compensation value corresponding to the ratio of the fluctuation in the rotation of the engine. CONSTITUTION:Under a starting command, the calculation and processing by a main routine are started and initialization is performed. After the initialization, an MPU100 receives intake temperature data from an intake temperature sensor 20, cooling water temperature data from a cooling water temperature sensor 21, and throttle opening degree data from a throttle sensor 23. A first compensation value for controlling the quantity of increase and decrease of fuel at the time of the coldness of an engine and at the time of its transient state is calculated on the basis of said data and stored in an RAM107. A second compensation value for controlling the quantity of increase and decrease of fuel depending on the quantity of the fluctuation in the rotational frequency of the engine is calculated and stored in the RAM107.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an air-fuel ratio control device for an internal combustion engine that detects an unstable operating state of an engine and controls the amount of fuel injected in response to the unstable state.

Detection of an unstable operating condition of an internal combustion engine, that is, an engine, is usually performed by detecting the rotational condition of the engine, particularly by detecting a rotational fluctuation condition. For example, as shown in Japanese Patent Application Laid-Open No. 51-104106, the difference Δ(6
In other words, the rate of change in acceleration during the rotation period is used as the evaluation value for the unstable state of the engine.

However, if we assume a misfire due to lean combustion during steady engine operation, we cannot predict that this misfire will cause a situation in which three consecutive rotation periods change under constant acceleration. It's about getting. Therefore, under such circumstances, it is not possible to detect the misfire of the engine as an unstable state by using the evaluation value as described above. In addition, it is affected by cylinder differences between multiple cylinders, and cannot reliably detect unstable engine operating conditions and cannot effectively reflect this in air-fuel ratio control. It is.

This invention was made in view of the above points, and it is possible to avoid a situation where the rotation period changes at a constant acceleration even though the engine is in an unstable state due to a misfire or other condition. An object of the present invention is to provide an air-fuel ratio control device for an internal combustion engine that reliably detects an unstable state of the engine and executes fuel injection amount control even in such cases.

That is, the air-fuel ratio control device according to the present invention detects the rotational speed of the engine at each constant rotational angle, and calculates the rotational fluctuation rate from the latest data based on stored data that is an integral multiple of the number of cylinders. Then, the basic injection amount of fuel is corrected by a correction amount corresponding to this rotational fluctuation rate.

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows the schematic configuration of the engine 11.
is a well-known spark ignition type engine installed in automobiles and the like, and combustion air used in this engine 11 is taken in through an air cleaner 12, an intake pipe 13, and a throttle valve 14. This engine 11 is controlled by a control circuit 15 configured by a computer.
A control signal corresponding to the fuel injection amount is supplied to electromagnetic fuel injection valves 16a, 16b1, . . . provided corresponding to each cylinder of the engine 11. Exhaust gas after combustion in the engine 11 is discharged into the atmosphere via the exhaust manifold 17, exhaust pipe 18, and the like.

The intake pipe 13 is equipped with a potentiometer-type intake air amount sensor 19 that detects the intake air m to the engine 11 and generates an analog voltage signal corresponding to this intake air amount, and further includes a temperature A thermistor-type temperature sensor 20 is provided that detects the detected temperature and generates an analog voltage signal corresponding to the detected temperature. Also, engine 1
1 is equipped with a thermistor-type water temperature sensor 21 that detects the cooling water temperature and generates an analog detection signal, and further detects the rotational speed of the crankshaft of the engine 11 and adjusts the rotational speed. A rotation speed (number) sensor 22 is installed which generates a corresponding pulse signal. This rotational speed sensor 22 generates a pulse signal when each cylinder of the engine 11 is at a specified crank angle.

Further, a throttle sensor 23 is installed for the throttle valve 14 to detect the opening degree of the throttle valve 14.

The detection signals from these sensors 19 to 23 are supplied to a control circuit 15, and the control circuit 15 outputs the detection signals from the engine 11.
The fuel injection amount is calculated according to the operating state of the fuel injection valves 16a, ?, and the fuel injection amount is calculated based on the fuel injection amount data calculated based on these detection signals. 6b, . . . are controlled.

FIG. 2 explains the specific configuration of the control circuit 15, and shows a microprocessor (MPU) that calculates the fuel injection amount.
)100. Further, a pulse-like signal corresponding to the rotational speed from the rotational speed sensor 22 is supplied to the rotational speed counter 101, and the number of detected pulses is counted to create rotational speed data. An interrupt command signal is sent to the interrupt control unit 102 in synchronization with the rotation.

When the interrupt control unit 102 receives the interrupt command signal, the interrupt control unit 102 transmits the MPU 10 via the common bus 115.
Outputs and supplies an interrupt signal for 0. Also, a starter switch 24 for performing a starting operation of the engine 11
A digital signal from the throttle sensor 23 and a digital throttle opening signal from the throttle sensor 23 are supplied to the digital input board 103, and this input signal is supplied to the MPU 100 via the common bus 115. Further, analog detection signals from the intake air amount sensor 19, intake air temperature sensor 20, and cooling water temperature sensor 21 are supplied to the analog input board 104, and these input signals are A/D converted and converted into digital data. , are sequentially imported into the MPU 100 using an analog multiplexer function.

In this control circuit 15, RAM 10 serves as a temporary storage unit temporarily used during program operation.
ROM 108'l, which is a read-only storage unit that stores programs and various constants, etc.
rbiel.

Here, a power supply section for this control circuit 15 is composed of two power supply circuits 105 and 106.

For the power supply circuit 105, a battery power supply 25
The battery power supply 25 is connected to the power supply circuit 106 via the key switch 26, and the power supply voltage is always present.
The power supply voltage is generated only when the power is turned on. In this case, the power supply circuit 105 is the RAM 1
This RAM 10
7 is always supplied with power regardless of the operation of the key switch 26, and this RAM 107 is set to function as a non-volatile memory. The other power supply circuit 106 is used to supply power to circuits and devices other than the RAM 107.

The fuel injection amount data calculated by the MPU 100 is supplied to the counter 109 via the common bus 115. This counter 109 includes a register and constitutes a counter for fuel injection time control, and is composed of a down counter, and includes electromagnetic fuel injection valves 16a, 16b, which are calculated by the MPU 100. Digital data representing the valve opening time for the river, that is, the fuel injection amount, is set and converted into a pulse signal with a pulse time width (duty ratio) that provides the actual valve opening time of the injector.

The pulse signal with the duty ratio set obtained by this counter 1°9 is supplied to the power amplifier 110, amplified, and distributed to the fuel injection valves 16a, 116b, . . . as a valve opening drive signal. . The timer 111 measures the elapsed time and supplies it to the MPU 100.

That is, in the control circuit 15 configured as described above, the rotation speed counter 101 measures the rotation speed of the engine 11 at each compression top dead center of each cylinder of the engine 11, for example, based on the detection signal of the rotation speed sensor 22. , an interrupt command signal is supplied to the interrupt control unit 102 every time the measurement ends or every revolution of the engine 11. The interrupt control unit 102 generates an interrupt signal in response to the cutting command, and executes an interrupt processing routine that causes the MPU 100 to calculate the fuel injection amount.

FIG. 3 shows Mpuio that performs air-fuel ratio control.

2 is a flowchart showing an outline of the control state. First, when the key switch 26 and the start switch 24 are turned on and the engine 11 is started, a start command is issued from a first step 120. Then, the arithmetic processing of the main routine is started, and initialization is executed in step 121 at the start of this arithmetic processing. After this initialization, in step 122, the intake air temperature data detected by the intake air temperature sensor 20, the cooling water temperature data from the cooling water temperature sensor 21, and the throttle opening data detected by the throttle sensor 23 are set to M p
ui.

It is taken into O. Then, in step 123, based on the data of the intake air temperature, cooling water temperature, and throttle opening degree of the engine 11 taken in in step 122, a first correction IK1 is made for controlling the increase and decrease of fuel during cold and transient times. is calculated and stored in RAM 107.

In such a main routine, steps 122 to 123 are repeatedly executed, and if an interrupt signal is supplied from the interrupt control unit 102 to the MPU 100 during this time, an interrupt processing routine indicated by 130 is executed. be done. That is, first, in step 131, a signal representing the rotation speed N of the engine 11 is taken in from the rotation number counter 101, and then in step 132, a signal representing the intake air amount Q from the intake air amount sensor 19 is taken in. Then, in the next step 133, these rotational speed N and intake air amount Q are
The data is stored in a predetermined area in the RAM 107.

Here, the RAM 107 has an area for storing n pieces of rotation speed data N. The data of the n number of revolutions N stored in this RAM 107 is used to calculate the revolution speed variation described later.
Inside is always the latest n continuous rotation speed N data, that is, Nn, Nn-1, ..., N3 from newest to newest.
, N2, and Nl are stored and set.

Next, in step 134, the rotation speed fluctuation is calculated based on the n number of rotation speed data, and a second correction JiK2 for controlling the increase/decrease of fuel according to the rotation speed fluctuation state of the engine 11 is calculated. Execute calculation processing.

Then, this second correction amount of 2 is stored in the RAM 107.

FIG. 4 shows a detailed arithmetic processing routine for calculating 2 as the second correction amount in step 134. In this arithmetic processing routine, first, in step 200, in order to calculate the rotation speed fluctuation rate, the n rotation speed data Nn
The average value NO of ~N1 is calculated, and in the following step 201, the standard deviation σn is calculated. Then, in step 202, the rotational fluctuation rate "σn/NOJ" is calculated.

Here, the number n of rotational speed data used in the calculations in steps 200 and 201 is determined by the number of cylinders in the engine 11 in order to absorb rotational fluctuations due to differences between the cylinders of the engine 11 or errors in the rotational signal detection section. It shall be an integer multiple of .

Next, in step 203, the rotational fluctuation rate σn calculated above is
/No is compared with the set value, and if the fluctuation rate σn/NO is smaller than the set value, that is, when it is determined that the engine 11 is in a stable state, the process proceeds to step 204, where the second correction amount is 2 and Δ is decreased by 1. let Conversely, the rotational fluctuation rate σn /
When it is determined that No is larger than the set value, engine 1
1 is in an unstable state, and in this case, in step 205, the second correction amount is increased by 2 and Δ is increased by 2. Then, in step 206, 2 is added to this second correction amount as M, O.
It is determined whether or not K2 is greater than J. If K2 is less than or equal to 1.0, 2 is set as the second correction amount and the process proceeds to step 135 shown in FIG. If it is determined in step 206 that the correction amount is greater than 1.0, the second correction IK2 is set as rl and OJ in step 207, and the process proceeds to step 135.

In other words, 2 for the second correction amount is a value of 1.0 or less, and the correction amount for the air-fuel ratio when the second correction IK2 is 1.0 is rOJ, and the second correction IK2
is less than 1.0, and the smaller the value, the more lean the air-fuel ratio is corrected.

In this way, in step 134 shown in FIG. 4, 2 is calculated as the second correction amount and stored in the RAM 107, and then in step 135 it is determined whether or not it is the fuel injection timing. If the current time is not the fuel injection time, the process jumps to step 139 and returns to the main routine. If it is the injection timing, the basic fuel injection amount (electromagnetic fuel injection valves 16a, 1) determined from the rotational speed N of the engine 11 and the intake air amount Q,
6b, ... calculate the injection time width t). The calculation formula in this case is as follows.

t=Fx (Q/N) (F: constant) Next, in step 137, the first correction IKI for fuel injection obtained in the main routine and the second correction amount for fuel injection obtained in the interrupt processing routine are used. 2 from RAM 107,
A correction calculation of the injection amount (injection time width) that determines the air-fuel ratio is executed.

The calculation formula for this injection time width T is as follows.

T=txK1 xK2 Then, in the next step 138, the corrected and calculated fuel injection amount data is set in the counter 109, and the process proceeds to the next step 139 to return to the main routine. When returning to this main routine, the process returns to the processing step at which it was interrupted due to interrupt processing.

In the explanation of the above embodiment, it was explained that n pieces of data of the rotational speed N were simply stored and set, and the rotational fluctuation rate was calculated based on this data. However, in Figure 4, steps 200-2
The rotational speed data used to calculate the rotational fluctuation rate shown in 02 is
: number of engine cylinders). By doing this, the rotation speed data used for calculating the rotation speed fluctuation rate is the rotation speed data detected during the combustion stroke of the same cylinder, and the cylinders of the engine 11 that affect the rotation speed detection. The effects of mechanical errors in the rotational speed detection section or the rotational speed detection section can be reliably removed, making it possible to detect and calculate the rotational speed fluctuation rate with higher accuracy.

As described above, according to the present invention, when the operating state of the engine becomes unstable due to, for example, a misfire, the engine speed changes at a constant acceleration. It is now possible to reliably detect the unstable state of the engine, and it has become possible to perform fuel injection amount control with high precision in such an unstable engine state, making it possible to always maintain stable air-fuel ratio control of the internal combustion engine. It will be executed.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram illustrating an air-fuel ratio control device according to an embodiment of the present invention, FIG. 2 is a configuration diagram illustrating a control circuit in the above embodiment, and FIG. FIG. 4 is a flowchart illustrating the main routine for controlling the injection amount. FIG. 4 is a flowchart illustrating the state of calculating the second correction amount for the basic fuel injection amount in the main routine. DESCRIPTION OF SYMBOLS 11... Engine, 13... Intake pipe, 14... Throttle valve, 15... Control circuit, 16a, 16
b... fuel injection valve, 19... intake air amount sensor, 2
0... Intake air temperature sensor, 21... Cooling water temperature sensor,
22... Rotation speed sensor, 23... Throttle opening sensor. Applicant's agent Patent attorney Takehiko Suzue No. 3N Figure 4

Claims (2)

[Claims] (1) Means for calculating a first correction amount in response to operating data such as temperature data and throttle condition of the internal combustion engine; means for detecting the rotation speed at each constant rotation angle of the engine; and a cylinder of the engine. means for storing the latest detected rotational speed data of a number corresponding to an integral multiple of the number; and means for calculating a rotational speed fluctuation rate based on the rotational speed data of an integral multiple of the number of cylinders stored by this means; means for calculating a second correction amount based on the rotation speed fluctuation rate, and corrects the basic injection amount based on the first and second correction amounts to execute fuel injection amount control. An air-fuel ratio control device for an internal combustion engine, characterized in that: (2) The rotation speed data used to calculate the rotation speed fluctuation rate is obtained within the time required for one cylinder to complete a full stroke. Fuel ratio control device.