JPS62135636A - Idling speed control device for internal combustion engine - Google Patents

Abstract

PURPOSE:To stabilize the drivability, by setting a fuel injection quantity to a predetermined value according to an engine speed in case of abnormality of an air flow meter, and setting an opening angle of an air flow control valve to a predetermined value greater than a value corresponding to a normal idling speed. CONSTITUTION:An abnormality determining means (d) is provided to compare an output from a suction air quantity detecting means (a) with a predetermined determination value and determine the abnormality of the means (a). A supply quantity computing means (e) is provided to compute a fuel supply quantity according to outputs from the suction air quantity detecting means (a) and an engine speed detecting means (b) and set the fuel supply quantity to a predetermined value according to an engine speed in the case that the detecting means (a) is abnormal. A fuel supplying means (f) is controlled by an output from the means (e). A control means (g) is provided to compute a control value for feedback controlling an idling speed when an idling condition is detected by a detecting means (c) and set the control value to a predetermined value greater than a value corresponding to a normal idling speed in the case that the detecting means (a) is abnormal. An air flow operating means (h) is controlled by an output from the means (g).

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an idle rotation speed control device for an engine in an automobile or the like.

(Conventional technology).

During idling operation of an internal combustion engine, it is necessary to precisely control the idling speed due to exhaust gas countermeasures and diversification of vehicle loads. On the other hand, such load fluctuations are usually detected by a sensor using intake air amount and rotational speed as parameters, and when a sensor abnormality occurs, it is necessary to take appropriate measures to avoid deterioration of drivability.

As a conventional idle speed control device for an internal combustion engine, there is one described, for example, in Japanese Patent Publication No. 5B-57623. In this device, the idle speed is controlled by changing the amount of intake air at idle using a flow control valve provided in a bypass passage that communicates the upstream and downstream sides of the throttle valve. Control B involves manipulating the air flow rate by analogically varying the area (opening degree) of the bypass passage using a duty-controlled flow rate control valve, and controlling the idle speed to match a predetermined target value. The duty value of is controlled by feedback. As a result, the idle speed can be controlled accurately and with good responsiveness by precisely manipulating the air flow rate during idle.

On the other hand, as described above, when the air flow sensor (air flow meter) is abnormal, the quality of sensor information deteriorates, resulting in poor engine drivability. In order to prevent such malfunctions due to sensor abnormalities, the present applicant has previously proposed a "fuel injection control device for internal combustion engines" (Japanese Patent Laid-Open No. 59-1555).
See Publication No. 37.

There is a In this device, when the air flow meter is abnormal, the fuel injection amount is set to a predetermined value according to the rotational speed to prevent the air-fuel ratio from becoming inappropriate and to prevent deterioration of drivability.

(Problem to be Solved by the Invention) However, in an idle speed control device that incorporates processing for responding to such a sensor abnormality, it is difficult to adjust the fuel injection amount to a predetermined value according to the engine speed when the air flow meter is abnormal. Since the fuel injection amount is set to a certain value, the fuel injection amount is fixed to the same value at the same rotation speed regardless of the load.

For this reason, the air-fuel ratio of the mixture becomes rich in the low load range,
Also, it tends to be thinner in high load ranges.

Therefore, there are cases where the air-fuel ratio is not necessarily appropriate for the engine load at that time, and it is desirable to improve this point. For example, malfunctions associated with an inappropriate air-fuel ratio include unstable engine rotation, which leads to deterioration of drivability during acceleration and deceleration, or unstable idle speed control, which can lead to extreme cases. Examples include engine stalling.

(Object of the Invention) Therefore, the present invention sets the fuel injection amount to a predetermined value according to the rotation speed when the air flow meter is abnormal, and also sets the opening degree of the flow control valve to a value larger than the value corresponding to the normal idle rotation speed. By setting it to a predetermined value, it stabilizes drivability during idling and acceleration/deceleration regardless of air flow meter abnormalities, thereby avoiding problems associated with inappropriate air-fuel ratios and improving engine drivability. The purpose is to

(Means for Solving the Problems) In order to achieve the above object, the idle speed control device for an internal combustion engine according to the present invention, as shown in FIG. The output of the intake air amount detecting means a is determined based on the operating conditions. an abnormality determining means d for determining whether the detecting means a is abnormal by comparing the values with the values; and an abnormality determining means d for calculating the fuel supply amount based on the intake air amount and the rotational speed, and for calculating the fuel supply amount when the intake air amount detecting means a is abnormal. supply amount calculating means e for setting fuel to a predetermined value according to the rotation speed; supply means f for supplying fuel to the engine based on the output of the supply amount calculating means e; and a predetermined target value when the engine is in an idle state. A control means that calculates a control value for feedback controlling the idle rotation speed so that the number of idle rotations is satisfied, and sets the control value to a predetermined value larger than the value corresponding to the normal idle rotation speed when the intake air amount detection means a becomes abnormal. g, and a flow rate operating means disposed in a passage bypassing the throttle valve of the intake passage and controlling the air flow rate by changing the degree of opening of the passage based on the control value.

(Function) In the present invention, when the air flow meter is abnormal, the fuel injection amount is set to a predetermined value according to the rotation speed, and the opening degree of the flow control valve is set to a predetermined value that is larger than the value corresponding to the normal idle rotation speed. set to the value.

Therefore, there is plenty of leeway in idle speed relative to the size of the load, and load fluctuations can be effectively dealt with despite inappropriate air-fuel ratios, and rotational fluctuations are avoided to prevent deterioration of drivability. .

(Example) Hereinafter, the present invention will be explained based on the drawings.

2 to 6 are diagrams showing an embodiment of the present invention.

First, to explain the configuration, in Fig. 2, 1 is an engine, intake air is supplied from an air cleaner 2 to each cylinder via an air flow meter 3, a throttle chamber 4, and each branch part of an intake manifold 5, and fuel is injected. The injector (supply means) 6 injects based on the signal St.

Here, the flow of intake air is controlled by a throttle valve 7 that is linked to the accelerator, and the flow of air during idling passes through a bypass port 8 and is adjusted by an idle adjustment screw 9. The air passes through a bypass passage 10 that communicates with the passage IO, and a necessary amount of air is ensured by a flow rate control valve (flow rate operation means) 11 installed in the passage IO.

The flow control valve 11 controls the passage area of the bypass passage 10 according to the duty value of the opening signal Sc. The electromagnetic coil is heated to a predetermined temperature by cooling water flowing through a cooling water circulation passage 12 provided integrally with the body.

The intake air flow rate Qa is detected by an air flow meter (intake air amount detection means) 3, and the opening CV of the throttle valve 7 is detected by a throttle valve opening sensor 13. Further, the rotation speed N of the engine 1 is detected by an electromagnetic pickup type rotation speed sensor (rotation speed detection means) 14, and the temperature Tw of the cooling water flowing through the water jacket is detected by a water temperature sensor 15.

Furthermore, the vehicle speed SS is detected by the vehicle speed switch 16,
The neutral position of the gear is detected by a neutral switch 17.

The vehicle speed switch 16 outputs an ON signal when the vehicle speed Ss is less than 1Q km/h, and the neutral switch 17 outputs a neutral signal Sn which becomes ○N when the gear of the manual transmission is in the neutral position.

The throttle valve opening sensor 13, vehicle speed switch 16, and neutral switch 17 constitute an idle state detection means 18. Signals from the rotation speed sensor 14, vehicle speed switch 16, and neutral switch 17 are input as they are to the control unit 20, and signals from the air flow meter 3, throttle valve opening sensor 13, and water temperature sensor 15 are input to the A/D.
The signals are A/D converted by converters 21, 22, and 23, respectively, and input to the control unit 20 as digital signals.

The control unit 20 has functions as an abnormality determination means, a supply amount calculation means, and a control means, and includes a CPU 24,
It is composed of a memory 25 and an I10 port 26.

The CPU 24 takes in necessary external data from the I10 port 26 according to the program written in the memory 25, performs arithmetic processing while exchanging data with the memory 25, and processes the processed data as necessary. is output to the I10 boat 26. I10 port 26
includes an idle state detection means 18 and an A/D converter 21.
〜23 is input, and the I10 ball
-26 outputs an injection signal Si and an opening signal Sc.

The memory 25 stores arithmetic programs in the CPU 24 and data used in the arithmetic operations in the form of a map or the like, and also temporarily stores external data.

Next, the effect will be explained.

FIG. 3 is a flowchart showing the fuel injection control and idle speed control programs written in the memory 25, and this program 1 is executed in synchronization with the engine rotation.

First, read the data necessary for Pl, that is, the intake air amount Qa, rotation speed X, calibration opening degree V, cooling water temperature Tw, vehicle speed Ss, and neutral position from each sensor mentioned above,
2, the rotation speed N is determined by the starting judgment value No. (for example, No = 4
5Orpm). When N≦NO, it is determined that cranking is in progress, and starting injection iTs is calculated in step 23. This is determined by looking up the optimum value for S from a table map that uses the cooling water temperature Tw at startup as a parameter. Next, in P4, Ti-Ts is set as the final injection amount Ti, and an injection signal Si having an injection pulse width corresponding to this Ti is output. Thereby, at the time of starting, an amount of fuel Ts is injected, and the engine l is started appropriately.

On the other hand, if N>No in step P2, it is determined that the startup has been completed and the operation is in progress, and the air flow meter 3 is
The intake air amount Qa detected by (hereinafter referred to as the detected intake air amount) Qa is compared with the minimum discrimination value Qo. The minimum determination value QO is set to a value smaller than the minimum air amount during idling, and is used to determine whether the output of the air flow meter 3 is abnormally small.

When Qa≦Qo, it is determined that the air flow meter 3 is abnormal and the process proceeds to P6; when Qa > Qo, it is determined that the minimum value of the air flow meter 3 output is cleared and the process proceeds to P7.
Then, at P, the detected intake air iQa is further set to the maximum discrimination value Q2.
Compare with. The maximum determination value Q2 is set to a value larger than the maximum air amount during engine operation, and is a value used to determine whether the output of the air flow meter 3 is abnormally large. When Qa≧Q2, it is determined that the air flow make 3 is abnormal and the process proceeds to P6, and when Qa<Q2, it is determined that it is normal and the process proceeds to P8.

Here, as shown in FIG. 4, the abnormality determination of the air flow meter 3 is made based on the position of the actually detected intake air iQa with respect to the operating range whose parameters are the intake air amount and the rotational speed. Abnormal region (1) is N>No and Qa<
This is a region that satisfies Qo, and examples of abnormalities in this region include, for example, disconnection of the signal line of the air flow meter 3. Further, the abnormal region (II) is a region where Qa≧Qo is satisfied, and is, for example, a case where the signal line of the air flow meter 3 is short-circuited with the power supply line. In addition, the solid line in the figure shows an example of detected air 1QaO for the rotational speed N under a constant load (that is, an example under normal conditions).

In the program again, during normal operation, the basic injection amount Tp is calculated in accordance with the following equation (2) in P8.

Qa However, K: Constant Next, reset the abnormality judgment flag IF in P9 and then set the PI
Proceed to O. The abnormality determination flag IF indicates that the air flow meter 3 is normal when IF=0, and indicates that the air flow meter 3 is abnormal when IF=0. Pl. Then, make various increase corrections (for example, water temperature correction, voltage correction, etc.) to the basic injection amount 'rp according to the following formula (■) to match the operating conditions at that time, and in P4, inject the injection amount after the increase correction as the final injection amount Ti. Outputs a signal Si.

T i = k-T p ......■ However, k:
Various increase correction coefficients On the other hand, when it is determined that the air flow meter 3 is abnormal at P5 and P7, the basic injection ff1T+) is set to the abnormal injection amount TpB at P6, and the abnormality determination flag IF is set using the pH. Proceed to PIG.

As shown in FIG. 5, the abnormal injection 1TpB is set by looking up the appropriate optimum value from a table map using the rotation speed N as a parameter. Figure 5 shows an example of a 4-cylinder engine, where at idle T p
B = 2.5m5ec, N<NC when running (however,
Tp B = within the range of N c =200Orpm)
4m5ec (Incidentally, the maximum value under normal conditions is 3m5ec
), and when N≧Nc, TpB=O is set to prevent the exhaust catalyst from burning out during high-speed operation.

In this way, even when the air flow meter 3 is abnormal, the fuel injection amount is fixed at an appropriate amount corresponding to the operating conditions, so that the air-fuel ratio is prevented from becoming inappropriate and deterioration of the operating quality is prevented. Note that the curve R in FIG. 5 shows the running resistance during top gear running.

After the above-described fuel injection control, the routine then shifts to idle rotation speed control.

First, P1□ determines the abnormality determination flag IF, and IF=O
In this case, it is determined that the air flow meter 3 is normal, and the rotation speed N is set to a predetermined value Ns (Ns = 10Orpm) in P13.
). When N<Ns, a duty value Ds at the time of starting is calculated at P14, and an opening signal Sc having this starting duty value Ds is output at P1.

The starting duty value Ds is determined by looking up the optimum value corresponding to the table manotube force and the like using the cooling water temperature TW at the time of starting as a parameter. The duty value of the opening signal Sc (slightly equivalent to control) is the flow rate control valve 11.
This is the ratio of valve opening time during one cycle of .

Also, when N≧Ns, it is determined that the vehicle is in operation, and PI6
It is determined whether the throttle valve 7 is fully closed or not. When fully closed, the PI7 determines whether the vehicle speed switch 16 is ON (that is, whether the vehicle speed is below 1Q km/h),
When it is OFF, the PIS further determines whether the gear is in the neutral position. When the vehicle is in the neutral position, it is determined that the vehicle is in an idle state, and the target idle rotation speed N is searched by PI3. This search includes cooling water temperature TW,
This is done by looking up the corresponding target idle rotation speed N, 4 from a table map using the air conditioner load, etc. as a parameter.

Next, compare the current rotation speed N with this NM at P2° and find that N=
Calculate the feed hack control duty (direct DF) so that it becomes NM, and proceed to PIS. As a result, the rotation speed N at idle matches the target value N corresponding to the operating conditions at that time. Precisely controlled.

If the throttle valve 7 is not fully closed at PI3, the tongue or PI
If the gear is not in the neutral position in S, it is determined that the engine is not in the idle state and the process proceeds to PZI. Note that when the vehicle speed switch 16 is ON at P1□, the process jumps from P1B and proceeds to PI3. When the vehicle is not in the idle state, the duty value D8 during running is calculated using PZI and the process proceeds to PIS. This can be done by, for example, stopping feedback control during idling and fixing the feedback control value to the value during idling.

On the other hand, when IF=1 in the step P1□, it is determined that the air flow meter 3 is abnormal, and the abnormal duty value DE is calculated in P2□. The abnormal duty value DE is calculated by looking up the maximum iFa (direction) which takes the cooling water temperature TW as a parameter. Therefore, if the normal idle speed is 650 rpm, the duty value will increase in the event of an abnormality, resulting in a higher value (for example, 900 rpm).
m) the idle speed is controlled. This means that there is sufficient rotation speed (in other words, engine output) relative to the magnitude of the load, and that load fluctuations can be easily coped with. Therefore, even when the engine shifts from idling to accelerated operation, it is not affected by the inappropriate air-fuel ratio of the air-fuel mixture, and there is no rotational fluctuation, thereby avoiding deterioration in drivability.

The same applies to the transition to deceleration operation, and when the normal operation is decelerated and transitioned to the idle state, fluctuations in rotation are suppressed and deterioration of drivability is avoided. Furthermore, during idle, idle rotation control can be made stable.

Note that the temperature of the solenoid coil of the flow rate control valve 11 to which the opening signal Sc is manually input is maintained equal to the cooling water temperature Tw by the cooling water in the cooling water circulation passage 12, so that when the cooling water temperature Tw is detected, the solenoid coil is By understanding the electromagnetic force, the air flow characteristics of the flow control valve 11 can be accurately known. Therefore, by storing the abnormal duty value in advance in the memory 25 in correspondence with the cooling water temperature TW, optimal duty control can be performed at all times.

(Effects) According to the present invention, it is possible to stabilize the idle rotation regardless of an abnormality in the intake air amount detection means, and it is also possible to avoid problems caused by inappropriate air-fuel ratios, and it is possible to avoid problems caused by inappropriate air-fuel ratios. It is possible to improve drivability by avoiding deterioration of drivability and instability of idle speed control.

[Brief explanation of drawings]

Fig. 1 is a basic conceptual diagram of the present invention, Figs. 2 to 6 are diagrams showing an embodiment of the present invention, - Fig. 2 is an overall configuration diagram thereof, and Fig. 3 is a fuel injection side '41'. and a flowchart showing the idle rotation speed control program, Fig. 4 is a characteristic diagram showing the abnormality determination area of the air flow make, Fig. 5 is a map showing the set amount of injection amount at the time of abnormality, and Fig. 6 is the opening degree. This is a map showing the duty value of a signal. ■・・・Engine, 3・・・Air flow meter (intake amount detection means),
6... Injector (supply means), 11...
...Flow rate control ff ■ valve (flow rate operation means), 14...
... Rotation speed sensor (rotation speed detection means), 18...
. . . Idle state detection means, 20 . . . Control unit (supply amount calculation means, control means).

Claims (1)

[Scope of Claims] a) intake air amount detection means for detecting the intake air amount of the engine; b) rotation speed detection means for detecting the engine rotation speed; and c) an idler for detecting that the engine is in an idle state. condition detection means; d) abnormality determination means that compares the output of the intake air amount detection means with a determination value determined from operating conditions to determine whether the detection means is abnormal; and e) fuel supply based on the intake air amount and rotational speed. supply amount calculation means that calculates the amount of fuel and sets the supply amount to a predetermined value according to the rotational speed when the intake amount detection means is abnormal; f) supplying fuel to the engine based on the output of the supply amount calculation means; g) Calculates a control value for feedback controlling the idle rotation speed so that it reaches a predetermined target value when the engine is in an idling state, and returns the control value to the normal value when the intake air amount detection means becomes abnormal; h) a control means disposed in a passage that bypasses a throttle valve in the intake passage, and changing the degree of opening of the passage based on the control value to control air flow; An idle speed control device for an internal combustion engine, comprising: a flow rate operation means for controlling the flow rate;