JPH01318733A - Control device for fuel cut of internal combustion engine - Google Patents

Abstract

PURPOSE:To improve the durability of an exhaust catalyst and to improve an engine stall resistance by detecting the exhaust temp. of an engine and correcting the specified engine revolution speed which should perform a fuel cut according to the detected temp. thereof. CONSTITUTION:The output signals of an exhaust temp. sensor, crank angle sensor and other sensors 23, 24 are input to a processing circuit 18 via an A/D converting circuit 20 or waveform shaping circuit 22. At the time when the rotating speed of an internal combustion engine reaches more than a preset value in an operating state preset by the internal combustion engine the fuel feeding to the internal combustion engine is cut off (fuel cut). In this case, the set value of the engine rotating speed which should perform a fuel cut by studying and correcting it by performing the specified arithmetic processing as well as comparing it with the temp. set value TO stored in advance in the ROM 26 of the processing circuit 18 inside based on the output equivalent to the temp. T1 detected by an exhaust temp. sensor 19 in the preset vehicle operation mode.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention provides a method for controlling an internal combustion engine in a predetermined operating situation, such as when a throttle valve is suddenly closed from an open state. Regarding a fuel cut control device for an internal combustion engine that cuts off the fuel by cutting off the fuel supply when the rotational speed exceeds a predetermined value, here is a novel internal combustion engine that learns such fuel cut control. This invention relates to a fuel cut control device for an engine.

Conventional technology There are manufacturing variations in each part of an automobile, and when the vehicle is completed, the design is such that the quality of the automobile as a product can be guaranteed even when the worst parts within the specifications overlap. has been done. However, there are slight differences in performance between individual completed vehicles. Furthermore, even if the vehicle is the same, performance changes due to changes in each part over time. Furthermore, due to changes in the driving environment of the vehicle, for example, when driving at high altitudes such as mountains or in cold places, performance tends to deteriorate.

A typical prior art is shown in FIG.

One of the ignition coils of the igniter in a spark-ignition internal combustion engine
The signal from the next coil is input from line 1 to a frequency/voltage conversion circuit 3 in a processing circuit 2 implemented by a microcomputer, and its output is input to a comparison circuit 4. A voltage value corresponding to a predetermined rotational speed at which the funi-nir cut is performed is applied to the comparison circuit 4 from the setting circuit 5. When the actual rotational speed input from the line 1 exceeds the rotational speed set in the setting circuit 5, the comparison circuit 11 demagnetizes the electromagnetic valve 7 for fuel cut using the switching transistor 6, and stops the fuel supply. cut off. This improves the durability of the catalyst that purifies exhaust gas, and also improves fuel efficiency during deceleration. However, in an attempt to maximize this benefit,
If the set rotational speed is set too low, the fuel cut area will expand and engine stall resistance will deteriorate.

In the prior art shown in FIG. 3, the setting circuit 5
The rotational speed set in is fixed and does not necessarily perform the optimal fuel cut operation for each internal combustion engine.

Another prior art is shown in FIG. Water-cooled internal combustion! fl
The temperature of the cooling water of the leapfrog is detected by a water temperature sensor 8 and is provided to a central processing circuit 11 via an analog-to-digital conversion circuit 10 of a processing circuit 9. The rotational speed of the internal combustion engine is detected by a crank angle sensor 2, and a waveform shaping circuit 1
3, and the signal is waveform-shaped and provided to the central processing circuit 11. In the central processing circuit 11, the rotational speed of the internal combustion engine at which the fuel should be cut is stored in advance depending on the temperature of the cooling water. Therefore, the central processing circuit 11 selects the rotation speed at which the fuel should be cut in response to the temperature of the cooling water detected by the water temperature sensor 8, and the actual rotation speed detected by the crank angle sensor 12 is determined by the predetermined rotation speed. When the rotational speed is higher than that, the transistor 14 demagnetizes the fuel injection valve 15 to cut off the fuel supply.

A processing circuit 9 that receives the output of the water temperature sensor 8 detects the warm-up state of the internal combustion engine.

Also in the prior art shown in FIG. 4,
The rotational speed at which the fuel cut is performed is fixed depending on the temperature of the cooling water during the warm-up period, and therefore it is not possible to set the rotational speed at which the fuel cut is most suitable for each vehicle.

Problems to be Solved by the Invention The purpose of the present invention is to provide a fuel cut for an internal combustion engine that improves the durability of an exhaust purification catalyst, improves fuel efficiency during deceleration, and satisfies engine stall resistance. The purpose of the present invention is to provide a control device.

Means for Solving the Problems The present invention provides a fuel supply system for an internal combustion engine that cuts off the fuel supply by cutting off the fuel supply when the rotational speed of the internal combustion engine is equal to or higher than a predetermined value under a predetermined operating condition. A fuel cut control device for an internal combustion engine, characterized in that the cut control device includes means for detecting the exhaust gas temperature of the internal combustion engine, and means for correcting the predetermined value in response to an output from the exhaust temperature detection means. It is a device.

According to the present invention, the exhaust gas temperature of the internal combustion engine is detected, and the rotation speed at which fuel cut is to be performed is corrected and set based on the exhaust gas temperature. For example, when the exhaust gas temperature rises to a temperature at which catalyst performance deteriorates, the set value of the rotational speed at which fuel should be cut is corrected to be lower.

By doing so, overheating of the exhaust purification catalyst can be prevented, durability can be improved, and fuel efficiency during deceleration can be improved to the maximum extent possible. Moreover, such corrections can be set optimally for each individual internal combustion engine, and even in the same vehicle, corrections can be made depending on changes in parts over time. Furthermore, correction can be made in response to changes in the driving environment.

Embodiment FIG. 1 is an overall block diagram of an embodiment of the present invention. The control circuit 17 includes a processing circuit 18 implemented by a microcomputer or the like.

The temperature of the exhaust gas of the liquid-cooled spark ignition internal combustion engine is detected by an exhaust temperature sensor 19 provided in the exhaust path, and its output is converted into a digital value by an analog-to-digital conversion circuit 20 and input to the processing circuit 18 . The rotational speed of the internal combustion engine is detected by a crank angle sensor 21 , and its output is waveform-shaped by a waveform shaping circuit 22 and input to the processing circuit 18 .

The operating condition of the vehicle equipped with this internal combustion engine, that is, the vehicle operating mode, is detected by the sensors 23 and 24, and the output of the sensor 23 is converted to a digital value via the analog-to-digital conversion circuit 20 and is applied to the processing circuit 18. The output from the other sensor 24 is sent to the waveform shaping circuit 2.
2, the signal is waveform-shaped and provided to the processing circuit 18.

Such sensors 23 and 24 include, for example, a coolant temperature sensor that detects the temperature of the coolant, an intake pressure sensor that detects the intake pipe pressure of the internal combustion engine, a throttle sensor that detects the opening degree of the throttle valve, and an intake air temperature sensor. an intake air temperature sensor that detects vehicle speed, a vehicle speed sensor that detects vehicle speed, an oxygen concentration sensor that detects oxygen concentration in exhaust gas, and internal combustion engine 7.
It may be a knock sensor or the like that detects whether or not knocking is occurring, and in this way the state of the vehicle is detected.

In the processing circuit 18, a central processing circuit 25 is provided, and this central processing circuit 25 includes a read-only memory 26.
and random access memory 27 are connected. The read-only memory 26 stores a program for performing the present fuel cut control, data on a reference temperature To, which will be described later, and a set value for the rotational speed of the internal combustion engine at which the initial fuel cut should be performed. The corrected rotational speed at which the fuel cut should be performed is stored in the random access memory 27. A signal from a setting circuit 28 is given to the processing circuit 18 . This setting circuit 28 has t
The operation switch 29 has the function of inputting the rotational speed of the internal combustion engine at which the fuel should be cut during the initial learning control operation as described in &, for example, as an analog value such as a voltage.
For example, when it is operated to conduct, the set value of the rotational speed at which the fuel should be cut is corrected, and when it is operated to be cut off, the fuel cut is controlled at the initial fuel cut rotational speed set in the read-only memory 26. The processing circuit 18 that performs the operation controls the switching transistor 30 to control the actuator 31 . This actuator 31 may be, for example, a solenoid valve that supplies fuel to the internal combustion engine, or may also be a fuel injection valve that injects fuel to the internal combustion engine.

First, the operation of the initial learning control will be explained with reference to the second (2I). This initial learning control operation sets a predetermined vehicle operation mode, and the exhaust temperature sensor 19 at that time
Based on the output corresponding to the temperature T1, the processing circuit 18
compares the temperature set value TO in the vehicle operation mode previously stored in the read-only memory 26 of the engine, and performs the following arithmetic processing operation to learn the set value N1 of the rotational speed of the internal combustion engine at which fuel cut should be performed. Correct and set. Here, the vehicle operating mode refers to the cooling water temperature, intake pressure, throttle opening, intake air temperature, vehicle speed, oxygen concentration in exhaust gas, and knocking occurrence status detected by the sensors 23 and 24 as described above. The driving situation depends on the following. The process moves from Stella 7nl to step r12, where it is determined whether the two switches are operated to conduct. If they are operated to conduct, it is determined that learning correction should be performed, and the process proceeds to the next step rI3. In this step n3, it is determined whether or not the area is within a range where learning correction should be performed. For example, learning correction is not performed in a warm-up driving situation, but - when the vehicle is in a so-called normal driving situation, the learning correction is not performed. , it is determined that the area is within the range where learning correction should be performed, and the process moves to the next step rs4.

In step n4, it is determined whether the temperature T1 detected by the exhaust gas temperature sensor 19 is equal to or equal to the value TO set by the read-only memory 26 in a predetermined vehicle operation mode.

That is, TI=TO... (1) When this first equation holds true, the rotational speed N1 at which the fuel should be cut is determined by the value No set in the read-only memory 26, as shown by the second equation. .

N 1 = NO...(2) In step r15, Tl>To
. . . It is determined whether or not (3) is satisfied, and when the third equation is established, the process moves to step rI6 and the fourth equation is calculated.

N1=a(To-Tl)+NO=14) Here, a is a positive constant. In this way, in a situation where the actual exhaust gas temperature T1 is higher than the target [TO], the rotational speed setting value N1 at which fuel cut should be performed is set to a predetermined value NO.
By lowering the amount of fuel, the amount of headroom required for fuel cut can be increased. This lowers the temperature of the exhaust purification catalyst and improves fuel efficiency during deceleration.

In addition, at the step port 5, the above-mentioned third equation does not hold,
Therefore, Tl<To
... When (5) holds true, the process moves to step n7 and the following equation 6 is calculated.

N1=b (To-Tl> +NO...(6) Here, b is a predetermined positive constant.Thus, when the actual exhaust temperature is lower than the target value TO, the exhaust gas purification catalyst Although it is good that the temperature is within the desired temperature range, if the engine stall resistance is judged based only on the exhaust temperature, it is considered to be worse than the central value of the design. In this way, engine stall resistance can be improved by calculating the formula.

As yet another embodiment of the present invention, the set value of the rotational speed at which the fuel should be cut may be constantly learned and corrected while the vehicle is running. , at a predetermined time point, for example, periodically, detect the exhaust gas temperature and the vehicle operating mode at that time, and detect the measured exhaust gas temperature TI and the exhaust gas temperature in the vehicle operating mode stored in the read-only memory 26 in a predetermined manner. The temperature setting value TO is compared with the temperature setting value TO, and calculations similar to those described in connection with FIG.

Effects of the Invention As described above, according to the present invention, initial learning control can be performed at a vehicle manufacturing factory and maintenance factory.
This makes it possible to achieve an effect equivalent to absorbing and correcting variations in the characteristics of each component. Furthermore, by performing the above-described constant learning control, it is possible to achieve an effect equivalent to constantly correcting changes in characteristics due to deterioration of vehicle parts.

In this way, according to the present invention, it is possible to improve the durability of the exhaust catalyst of an internal combustion engine, improve fuel efficiency during deceleration, and further improve engine stall resistance.

[Brief explanation of the drawing]

Fig. 1 is an overall block diagram of an embodiment of the present invention, Fig. 2 is a flowchart for explaining the operation of initial learning control, Fig. 3 is a block diagram of a prior art, and Fig. 4 is another prior art. FIG. 17... Control circuit, 18... Processing circuit, 19...
Exhaust temperature sensor, 20...Analog-digital conversion circuit, 21...Crank angle sensor, 22...Waveform shaping circuit, 23.24...Sensor, 26...Read-only memory, 27...Random access Memory, 28...
Setting circuit. 2...switch, 30...transistor, 31...
・Actuator

Claims (1)

[Scope of Claims] A fuel cut control device for an internal combustion engine that cuts the fuel by cutting off the fuel supply when the rotational speed of the internal combustion engine is equal to or higher than a predetermined value under a predetermined operating condition of the internal combustion engine. A fuel cut control device for an internal combustion engine, comprising: means for detecting an exhaust gas temperature; and means for correcting the predetermined value in response to an output from the exhaust temperature detecting means.