JPH0658087B2 - Fuel supply control device for internal combustion engine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a fuel supply amount control device for an internal combustion engine, and more particularly to a fuel supply amount control when the intake air amount cannot be detected.

[Prior Art] There has been proposed a control device that precisely controls an internal combustion engine to improve output and fuel efficiency and contribute to cleaning exhaust gas. A typical example thereof is a device that detects the intake air amount of an internal combustion engine and precisely adjusts the fuel supply amount according to the detected amount.

By the way, the above device determines the required fuel supply amount based on the output value of the intake air amount sensor. Therefore, if the intake air amount sensor fails, the sensor outputs an abnormal output that differs from the actual intake air amount, and the fuel supply amount also becomes abnormal, which may result in engine stoppage or abnormal operation due to a decrease in drivability. .

To solve this problem, there is provided a device that fixes the fuel supply amount to a constant value when the output of the intake air amount sensor becomes abnormal (Japanese Patent Laid-Open No. 55-164738).

[Problems to be Solved by the Present Invention] However, when the fuel supply amount immediately changes to a constant value when a sensor abnormality occurs or vice versa, the fuel supply amount calculated according to the sensor output value and There is a large difference from the fixed amount, which may cause a shock to the internal combustion engine, which causes problems such as deterioration of drivability and deterioration of riding comfort in the case of an automobile.

[Means for Solving Problems] As means for solving the problems of the device for holding the fuel supply amount at a constant value, the following means of the present invention are adopted.

That is, according to the present invention, as shown in FIG. 1, the operating state detecting means for detecting the operating state of the internal combustion engine, including the intake air amount data, and the operating state data of the internal combustion engine detected by the operating state detecting means are included. At least when the fuel supply amount setting means for setting the fuel supply amount of the internal combustion engine using the intake air amount data and the intake air amount data detected by the operating condition detecting means are abnormal data, the fuel supply amount A fuel supply amount control device for an internal combustion engine, comprising: a failsafe means for fixing the fuel supply amount set by the setting means to a predetermined amount; and further, the fuel supply amount is set to a predetermined amount by the failsafe means. When the fixing process is performed or when the fixing process is released, it is possible to determine whether the throttle valve is almost fully closed and the moderating means for gradually changing the fuel supply amount. When the throttle valve determines that the throttle valve is in a substantially fully closed state, the predetermined amount of fuel supply amount set by the fail-safe means is set as compared to when the throttle valve is not fully closed. A fuel supply amount control device for an internal combustion engine is characterized in that the changing speed of the fuel supply amount changed by the smoothing means is set to a large value and set to a small value.

Here, the operating state detecting means detects, for example, the rotational speed of the internal combustion engine, the cooling water temperature, the intake air temperature, etc., in addition to the intake air amount. The intake air amount does not simply indicate the inflow volume of the intake air, but also includes data indirectly representing the inflow amount, for example, the pressure of the intake air. There are an air flow meter and an intake pressure sensor for detecting the intake air amount, and examples of the air flow meter include a wind vane type, a heat wire type, and a Karman vortex type.

The fuel amount setting means calculates and sets the fuel supply amount required for the internal combustion engine from the operating state data, and therefore sets it based on at least the intake air amount data. It is usually composed of electronic circuits.

The fail-safe means is, for example, means for determining that the intake air amount data has an impossible value and that the fuel amount supply amount set by the fuel amount setting device is fixed to a predetermined amount. Is. Specifically, if the voltage value that represents the intake air amount data exceeds the upper and lower limits, or if the edge of the pulse signal of the Karman vortex sensor is not detected at all, it is determined that the intake air amount data is abnormal. Etc. It is usually composed of electronic circuits.

The smoothing means is a means for gradually changing from the immediately preceding set value to the predetermined value when the intake air amount data is determined to be abnormal, instead of immediately setting the fuel amount supply amount to the predetermined amount. . It is usually composed of electronic circuits. The discriminating means is a device for discriminating the substantially fully closed state of the throttle valve by using, for example, an idle switch, and in the present invention, when it is determined that the throttle valve is in the fully closed state, it fails compared to when it is not. The predetermined amount of the fuel supply amount set by the safe means is made small, and the changing speed of the fuel supply amount changed by the smoothing means is made large.

[Operation] Based on the intake air amount data detected by the operating state detecting unit as the fuel supply amount of the normal internal combustion engine, the fuel amount setting unit sets the fuel supply amount, and that amount of fuel is supplied to the internal combustion engine. . However, when the intake air amount data is abnormal by the fail-safe means, the fuel supply amount shifts to a predetermined amount and is fixed.However, the anneal means does not cause the fuel supply amount to change suddenly and gradually changes from the set value. Change to quantitative.

Further, when the determination means determines that the throttle valve is almost fully closed, the predetermined amount is set to a smaller value and the degree of change in the fuel supply amount becomes sharper than in other cases.

[Embodiment] First, FIG. 2 is an explanatory view showing an internal combustion engine and a fuel supply amount control apparatus therefor according to an embodiment of the present invention.

1 is an internal combustion engine body, 2 is a piston, 3 is a spark plug, 4
Is an exhaust manifold, 5 is an exhaust manifold 4, and is an oxygen sensor for detecting the residual oxygen concentration in the exhaust gas, 6
Is a fuel injection valve for injecting fuel into intake air of the internal combustion engine body 1, 7 is an intake manifold, 8 is an intake air temperature sensor for detecting the temperature of intake air sent to the internal combustion engine body 1, and 9 is internal combustion engine cooling water. A water temperature sensor for detecting the temperature, 10 is a throttle valve, 11 is linked to the throttle valve 10,
A throttle opening sensor that detects the opening of the throttle valve 10 and outputs a signal, and outputs an ON signal as the idle switch IDL when the throttle valve 10 is in a fully closed state, and 14 is a Karman vortex type that measures the intake air amount. The flow rate sensor 15 represents a surge tank that absorbs the pulsation of the intake air.

16 is an igniter that outputs a high voltage necessary for ignition, 17 is a distributor that supplies a high voltage generated by the igniter 16 to the ignition plug 3 of each cylinder in conjunction with a crankshaft (not shown), and 18 is a distributor 17 Distributor 17 installed inside
Rotation angle sensor that detects a rotation angle and a rotation speed that output 24 pulse signals for one rotation of the crankshaft, that is, two rotations of the crankshaft, and 19 is a cylinder discrimination sensor that outputs a pulse signal for one rotation of the distributor 17. , 20 is an electronic control circuit, 21 is a key switch, and 22 is a starter motor. Reference numeral 26 denotes a vehicle speed sensor which is interlocked with the axle and transmits a pulse signal corresponding to the vehicle speed.

Next, FIG. 3 shows a block diagram of an example of the electronic control circuit 20 and its related parts.

Reference numeral 30 denotes a central processing unit (hereinafter simply referred to as CPU) that inputs and calculates data output from each sensor according to a control program and performs processing for controlling operation of various devices. Reference numeral 31 denotes a control program and initial data. A read-only memory (hereinafter simply referred to as ROM) to be stored, 32 is a random access memory (hereinafter simply referred to as RAM) in which data input to the electronic control circuit 20 and data necessary for arithmetic control are temporarily read and written, Reference numeral 33 denotes a backup random access memory (hereinafter simply referred to as a backup RAM), which is a non-volatile memory backed up by a battery, so as to retain data necessary for subsequent internal combustion engine operation even if the key switch 21 is turned off. Is a buffer for the output signal of each sensor, and 38 is Multiplexer for selectively outputting the output signal of the sensor to the CPU 30, 39 denotes an A / D converter for converting an analog signal into a digital signal, 40 or buffer via the buffer, the multiplexer 38 and the A
Each sensor signal is sent to the CPU 30 via the A / D converter 39, and the multiplexer 38 from the CPU 30, A / D
It represents an input / output port for outputting a control signal of the converter 39.

And 41 is the output signal of the oxygen sensor 5 to the comparator 4
Buffer for sending to 2, and 43 for Karman vortex flow sensor 1
4, represents a shaping circuit for shaping the waveforms of the output signals of the rotation angle sensor 18 and the cylinder discrimination sensor 19, and each sensor signal of the throttle opening sensor 11 or the like is output by the input / output port 46 directly or via the buffer 41 or the like. It is sent to the CPU 30.

Furthermore, 47 and 48 are CPUs via output ports 49 and 50.
The signal from the fuel injection valve 6, the igniter 16
Drive circuits for driving the respective. Again 51
Is a bus line that serves as a passage for signals and data, and 52 is a CPU
A clock circuit for sending a clock signal as control timing to the ROM 31, the RAM 32, etc. at a predetermined interval is shown.

Next, a control program, which is a main part of this embodiment, will be described.

4 to 6 show flow charts of the control program. These control programs are executed every engine revolution.

FIG. 4 shows an abnormality check routine for checking whether or not the output value of the Karman vortex flow sensor 14 is abnormal.
First, when the process is started, the output value of the flow rate sensor is read in step 110. Next, at step 120, it is judged if the output value is within a predetermined range. This predetermined range indicates a range of values that the flow rate sensor 14 can take in a normal state. Therefore, if the output value of the flow rate sensor 14 is within the predetermined range, it is determined to be "YES" and the abnormality flag F is reset in step 130. On the other hand, if the output of the flow rate sensor 14 is outside the predetermined range in step 120, it is determined to be “NO”, and the flag F is set in step 140. In this way, this process is once terminated and the process of another routine is performed. The determination in step 120 above is
The determination may be “NO” when the edge of the pulse signal is not detected at all.

FIG. 5 shows a control routine for calculating the ignition timing and the fuel injection amount.

First, when the process is started, it is determined in step 210 whether or not the flag F is set. When the flow rate sensor 14 is normal, it is determined to be "NO", and then the ignition timing is calculated in step 220. The ignition timing is calculated from a value such as the intake air amount, the engine speed, the cooling water temperature and the like using a known map. Next, at step 230, it is judged from the value of the timer set at the time of F = 1 → F = 0 whether or not 3 seconds have elapsed after the recovery of the flow sensor 14 from the abnormality. If F = 0 from the beginning, "YES"
Then, in step 235, it is determined whether or not the engine is starting. If the engine is starting, the injection amount for starting is calculated in step 270 using the cooling water temperature and the like as parameters. If the engine is not started, the fuel injection amount is calculated in step 240. The fuel injection amount is calculated from a known map or the like according to the intake air amount, the engine rotation speed, other cooling water temperature, oxygen concentration, intake air temperature and the like. Step 230
If 3 seconds have not elapsed after returning, the routine proceeds to step 231, where it is judged whether or not it is at the time of starting and it is judged as "YES", and the injection amount for starting is calculated at step 233. When “NO” is determined in step 231, the process proceeds to step 232, the steady-state injection amount is calculated, and the process proceeds to step 234. In step 234, the calculated injection amount value is put in the variable τL of the target injection amount, and the process proceeds to the moderating process of step 310. This process will be described later. In this way, the process is temporarily terminated.

Next, when F = 1 in the abnormality check routine described above, in the control routine, first, in step 210, it is determined to be "YES". Next, at step 250, processing for fixing the ignition timing to a predetermined timing is performed. Next, at step 260, it is determined whether the key switch 2 is currently started or not.
It is determined from the signal of 1 and the engine rotation speed. If it is at the time of starting, it is determined as "YES", and the injection amount for starting is calculated at step 270. If it is not the starting time, it is determined to be "NO" in step 260, and then step 280.
Is processed.

At step 280, it is judged if the idle switch IDL is on, that is, if the throttle valve 10 is almost fully closed. If it is on, it is determined as "YES", and the injection amount fixed value (3 ms) is set to the variable τL that measures the target fuel injection amount. If it is not ON, it is determined to be "NO" and another fixed value (5 ms) is set to τL. After the processing of step 290 or step 300, the smoothing processing is performed in step 310. Step 2 mentioned above
Even when it is determined to be "NO" in 30, the smoothing process of step 310 is performed.

Details of this smoothing processing are shown in the flowchart of FIG. First, at step 410, it is judged if the flag F = 1. If F = 1, it is determined to be "NO", and the value of K3 is set to the coefficient K in step 420. The coefficient K is a coefficient for determining the degree of smoothing, and a value exceeding "1" is set. If F = 1, at step 410, “YE
S ”and step 430 is processed. In step 430, it is determined whether the idle switch is on.
If it is ON, the coefficient K is set to K1 in step 440. If it is not ON, the coefficient K is set to K in step 450.
2 is set. The values of K1, K2 and K3 are fixed values or values determined by the operating state of the internal combustion engine. For example, K1 and K2 are calculated using the water temperature as a parameter, and K3 is calculated using the engine speed as a parameter. For simplification of processing and memory, K1, K2 and K3 may be fixed values. In this case, the relative magnitude relationship is K1 <K2≈
K3 is preferable for smooth operation of the internal combustion engine.

In step 460, the value of τ which is the basic value of the actual fuel injection amount is calculated by the smoothing process. That is, K
And τL and the previously determined injection amount τ, the current injection amount τ is calculated by the following formula.

The larger the value of K, the larger the rounding, and the value of τ is less likely to change suddenly.

In this way, the annealing process of step 310 shown in FIG. 5 is completed, and thereafter, the value of τ is used in the injection routine not shown, and the fuel of τ is injected from the injection valve 6 into the intake air. . In this way, the smoothing process can be applied to the sudden change in the fuel injection amount due to the change in the flag F.

A typical example of the above processing operation is shown in FIG. When the flag F changes from “0” to “1” at the time point t1, the injection amount τ does not change abruptly due to the smoothing process, and it reaches the time point t2 and coincides with the target fixed value. On the other hand, in the conventional device shown by the dotted line, it becomes a fixed value instantly at time t1.

The same applies when the flag F changes from "1" to "0".
When F = 0 at the time point t3, τ takes the value of τ in the normal state until the time point t4. In the conventional device shown by the dotted line, the normal value τ is instantly set at time t3.

In order to prevent τ hunting due to the vibration of the flag F, a delay is provided at times t1 and t3, and after the flag F is changed, the smoothing process is not performed immediately after, but is performed after a predetermined time. Good.

[Advantages of the Invention] The present invention is a moderating means for gradually changing the fuel supply amount to a predetermined value or from a predetermined value to a normal calculated value when the intake air amount data becomes abnormal or returns from the abnormality. Therefore, even if the difference in the set value of the fuel supply amount is large, the internal combustion engine is not shocked, and the drivability,
The ride comfort can be excellently maintained. Furthermore, when the throttle valve is almost fully closed, the fuel supply amount at the time of failure is set to a small value and the convergence speed at the time of switching the fuel supply amount is increased. It is possible to increase the transition speed of, and quickly meet the low output demand of the driver.

[Brief description of drawings]

FIG. 1 is a basic configuration diagram as an example of the present invention, FIG. 2 is a configuration diagram of an embodiment of the present invention, FIG. 3 is a block diagram of its electronic control circuit, and FIG. 4 is an electronic control circuit. FIG. 5 is a flowchart of the abnormality check routine executed, FIG. 5 is a flowchart of the same control routine, FIG. 6 is a flowchart of the same anneal processing routine, and FIG. 7 is a timing chart of the processing. 1 ... Internal combustion engine, 6 ... Fuel injection valve 8 ... Intake air temperature sensor, 9 ... Water temperature sensor 10 ... Throttle valve 11 ... Throttle opening sensor 14 ... Karman vortex flow sensor 18 ... Rotation angle sensor , 20 ... Electronic control circuit 21 ... Key switch

Claims (2)

[Claims] 1. An operating condition detecting means for detecting an operating condition of an internal combustion engine including intake air amount data, and at least the intake air amount data among operating condition data of the internal combustion engine detected by the operating condition detecting means. Fuel supply amount setting means for setting the fuel supply amount of the internal combustion engine, and when the intake air amount data detected by the operating state detecting means is abnormal data, it is set by the fuel supply amount setting means. A fuel supply amount control device for an internal combustion engine, comprising: a fail-safe means for fixing a fuel supply amount to a predetermined amount; and a process for fixing the fuel supply amount to a predetermined amount by the fail-safe means. Or a means for gradually changing the fuel supply amount when the fixing process is released, and a means for determining whether the throttle valve is in a fully closed state. When the determination means determines that the throttle valve is in a fully closed state, the predetermined amount of fuel supply amount set by the fail-safe means is set to a small value and the throttle valve is set to a smaller value than when the throttle valve is not fully closed. A fuel supply amount control device for an internal combustion engine, characterized in that a changing speed of a fuel supply amount changed by an averaging means is increased. 2. The fuel supply amount control device for an internal combustion engine according to claim 1, wherein the intake air amount data is intake pressure.