JPH06100134B2 - Air-fuel ratio controller for engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention relates to an air-fuel ratio control device for an engine (hereinafter referred to as an A / F control device), and relates to an inside of an engine room accompanying A / F control during idle operation. It is designed to prevent the abnormal temperature rise of the above.

<Prior Art> Conventionally, an electromagnetic fuel injection valve is arranged in the intake passage of the engine, and the fuel supply amount is adjusted by supplying a pulse electric signal to this fuel injection valve to adjust the air-fuel ratio (A / F). An A / F control device for controlling an A / F has been proposed.

An example of this type of A / F control device is shown in FIG. As shown in the figure, this example is applied to a vehicle equipped with a 4-cylinder engine. In the intake passage 1 of the 4-cylinder engine E, an air cleaner, an air flow sensor 3, a throttle valve, and a surge tank are arranged in this order from the upstream side. 5 and an electromagnetic fuel injection valve 6 are provided.

Here, the Karman vortex type is used as the air flow sensor 3, and this air flow sensor 3 outputs an electric signal having a frequency proportional to the amount of intake air. The amount can be detected.

In addition, the surge tank 5 is provided in the collecting portion of the intake manifold 1a, and the intake manifold 1a on the downstream side of the surge tank 5 is provided.
A fuel injection valve 6 is provided in each branch portion of the cylinders leading to each cylinder. That is, the engine E is configured as a multipoint fuel injection system (MPI system) engine.

Further, a control signal (pulse train signal) is output from the controller 7 to each fuel injection valve 6,
In addition to the signal from the air flow sensor 3 described above, the controller 7 also receives a throttle opening sensor 8, an intake passage pressure sensor 9, a rotation speed sensor 10, an intake temperature sensor 11, an atmospheric pressure sensor.
12, water temperature sensor 13, vehicle speed sensor 14, idle switch 15, O ₂
Signals from the sensor 17 etc. are also input.

Here, the throttle opening sensor 8 detects the opening of the throttle valve 4, and as the throttle opening sensor 8, for example, a potentiometer is used.

The intake passage pressure sensor 9 detects the pressure in the intake passage 1 (for example, the pressure in the intake manifold 1a), the rotation speed sensor 10 detects the engine rotation speed, and the intake air temperature sensor 11 detects the pressure in the intake passage 1 inside. It detects intake air temperature, atmospheric pressure sensor 12 detects atmospheric pressure, water temperature sensor 13 detects engine cooling water temperature, vehicle speed sensor 14 detects vehicle speed, idle switch 15 is The O ₂ sensor 17 detects the oxygen concentration in the exhaust passage 16 by detecting whether or not there is a state.

By the way, this device adjusts the fuel supply amount by supplying the pulsed electric signal obtained by feeding back the oxygen concentration in the exhaust passage 16 detected by the O ₂ sensor 17 to the electromagnetic fuel injection valve 6. The A / F is controlled by the controller 7, but the above-mentioned control is mainly performed by the controller 7 (which is composed of a CPU, RAAM, ROM, input / output interface, etc.).

That is, the control of this controller 7, basically input to RAM address read various input information from various sensors, then T B from the _{map, K, K WT, K FB} , T
_D (where T _B is the basis for determining the injection amount,
K _WT , K _FB , and T _D are T _B depending on the cooling water temperature, O ₂ sensor output, etc.
After finding the in which) to correct, for example _{Tinj = T B × K × K} WT × K FB × T D becomes operation is performed, then drives the electromagnetic fuel injection valve 6 by a pulse width of Tinj Things are done. As a result, the fuel supply amount is adjusted and the air-fuel ratio is controlled.

Further, the controller 7 is a feedback coefficient K _FB for determining the pulse width of the electric signal to the electromagnetic fuel injection valve 6.
A feedback coefficient setting means M1 for setting the value of is provided.

Here, the feedback coefficient K _FB has sum information of proportional gain P (this is referred to as P gain), integral gain I (this is referred to as I gain), etc., such as 1 + P + I. The gain has the characteristic shown in FIG. 3 (b), and the I gain has the characteristic shown in FIG. 3 (c). The P gain and I gain are obtained from the output characteristics of the O ₂ sensor 17 as shown in FIG. 3 (a).

The output level of the O ₂ sensor 17 switches between a low level (for example, lean L) and a high level (for example, rich R) with the stoichiometric air-fuel ratio state as a boundary, and accordingly, the P gain has a value of ± α. At the same time, the I gain takes a value of β% / sec. And the average value I mean of I gain is usually A / F = 14.
It has almost the same information as 7 (theoretical air-fuel ratio).

<Problems to be Solved by the Invention> By the way, in the vehicle with the A / F control device as described above,
When idling, for example, when one cylinder continuously misfires, the intake air amount is increased to compensate for the decrease in the engine speed Ne due to misfire. As a result, since the O ₂ concentration detected by the O ₂ sensor 17 is high, the AF value is larger than the theoretical A / F value, that is, the lean L signal indicating that the fuel is insufficient is output to increase the I gain. Increase fuel supply. As a result, there is a problem that the temperature inside the engine room becomes abnormally high and the durability of the non-metal member inside the engine room is significantly impaired.

In addition, while the vehicle is running, even if the above-mentioned one-cylinder misfire occurs, the inside of the engine room is cooled by the running wind.
The temperature does not rise as much as it becomes more severe for non-metallic members.

In view of the above problems, it is an object of the present invention to provide an engine air-fuel ratio control device capable of preventing an abnormally high temperature inside the engine room.

<Means for Solving the Problems> The configuration of the present invention that achieves the above object is to supply a signal obtained by feeding back the oxygen concentration in the engine exhaust passage to the electromagnetic fuel injection valve to supply the fuel. In the device for adjusting the air-fuel ratio by adjusting the, the oxygen concentration detection sensor installed in the exhaust passage of the vehicle to detect the oxygen concentration in the exhaust gas, and the temperature of the catalyst installed in the exhaust passage to process the exhaust gas A high temperature sensor for detection, a comparison means for sending a signal when the temperature of the catalyst detected by the high temperature sensor exceeds a set value set based on the dangerous temperature of the engine room during idling, and a catalyst means by this comparison means during idling. When it is detected that the temperature of the catalyst exceeds the set value, the temperature of the catalyst is set to the set value until the ignition switch is turned off or by the comparison means. Until it detects that the amount becomes less than 0, it has a control means for controlling the electromagnetic fuel injection valve so that the fuel increase amount becomes zero or the air-fuel ratio is fixed to a predetermined value on the lean side which is larger than the theoretical air-fuel ratio. Is characterized by.

<Examples> Examples of the present invention will be described below in detail with reference to the drawings. It should be noted that the same parts as those of the conventional technique are denoted by the same reference numerals, and overlapping description will be omitted. Further, this embodiment also has a warning function for preventing the catalyst from being melted.

As shown in FIG. 1, the high temperature sensor 18 is composed of a thermocouple or the like and is arranged at the outlet of a catalyst (not shown) and sends a signal indicating the detected temperature of the catalyst to the comparators 19 and 20. .
The comparator 19 has a critical temperature (950
° C.) and the set value V _ref1 representing the comparing the signal of the high-temperature sensor 18, when the signal reaches a set value V _ref1 or more, sends a signal representing this fact. Also, the comparator 20
Is a set value V _ref2 representing the dangerous temperature of the catalyst (700 ° C.) set based on the dangerous temperature of the engine room when the engine (not shown) is idling, and the high temperature sensor 18
When the signal exceeds the set value V _ref2 , a signal indicating this is transmitted. The controller 7 determines from the signal of the idle switch 15 whether the vehicle is running or idling. If the vehicle is running, the controller 7 selects the signal of the comparator 19, and if it is idling, the comparison is made. Select the signal of container 20.

Thus, when the output signal of the comparator 7 indicates that the temperature of the catalyst has become equal to or higher than the melting damage risk temperature while the vehicle is traveling (for example, when the output is in the "H" state), the controller 7
21 is turned on and the alarm lamp 22 is turned on.

On the other hand, when the signal of the comparator 20 indicates that the temperature of the catalyst has become equal to or higher than the dangerous temperature of the catalyst corresponding to the dangerous temperature of the engine room during idling (for example, the signal is “H”).
(When the state is reached), regardless of the signal from the O ₂ sensor 17, the electromagnetic fuel injection valve 6 is controlled to make the fuel increase amount zero, that is, I
The gain is set to zero or fixed to a predetermined value on the lean side where the air-fuel ratio is larger than the stoichiometric air-fuel ratio. Such control is performed until, for example, the signal of the comparator 20 indicates that the catalyst temperature is lower than the set value (for example, until the signal becomes the "L" state), or until the ignition switch is turned off.

The set value of the comparator 20 is set in consideration of the heat resistant temperatures of important safety parts (fuel system, brake system, etc.) in the engine room. That is, there is a correlation between the catalyst temperature and the engine room temperature, and when the catalyst temperature rises due to heat transfer or radiation, the engine room temperature also rises. In this embodiment, the catalyst temperature corresponding to the dangerous temperature of the engine room is set to 700 ° C.

In this embodiment, the comparator 20 is operated during idling.
When it is detected that the temperature of the catalyst exceeds the set dangerous temperature during idling, the A / F control is interrupted and the electromagnetic fuel injection valve is throttled to prevent the temperature rise in the engine room.

<Effects of the Invention> As described in detail with reference to the embodiments above, according to the present invention, since the temperature in the engine room during idling is also monitored via the catalyst temperature, the O ₂ sensor is used.
Even in a vehicle equipped with an A / F control device, it is possible to prevent the occurrence of inconveniences such as deterioration of non-metallic members associated with an abnormal rise in engine room temperature without occurring. Further according to the invention,
It also has the effect of contributing to catalyst protection.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a block diagram showing a conventional technique, and FIGS. 3 (a) to 3 (c).
Is a graph showing the operation of the prior art. In the drawings, 1 is an intake passage, 4 is a throttle valve, 6 is an electromagnetic fuel injection valve, 7 is a controller, 10 is a rotation speed sensor, 15 is an idle switch, 16 is an exhaust passage, and 17 is an O ₂ sensor.

Continuation of the front page (56) References JP-A-54-8221 (JP, A) JP-A-56-20727 (JP, A) JP-A-61-98933 (JP, A) JP-A-60-3453 (JP , A) Japanese Patent Publication Sho 59-17255 (JP, B2)

Claims (1)

[Claims] 1. An apparatus for controlling an air-fuel ratio by adjusting a fuel supply amount by supplying a signal obtained by feeding back an oxygen concentration in an engine exhaust passage to an electromagnetic fuel injection valve. The oxygen concentration detection sensor installed in the exhaust gas to detect the oxygen concentration in the exhaust gas, the high temperature sensor installed in the exhaust passage to detect the temperature of the catalyst that processes the exhaust gas, and the temperature of the catalyst detected by the high temperature sensor, A comparison unit that sends a signal when the temperature exceeds a set value set based on the dangerous temperature of the engine room during idling, and an ignition switch when the comparison unit detects that the temperature of the catalyst exceeds the set value during idling. Until the fuel is turned off or until the comparison means detects that the temperature of the catalyst has dropped below the set value, does the fuel increase amount become zero? Properly air-fuel ratio control system for an engine, characterized in that a control means for controlling an electromagnetic fuel injection valve as the air-fuel ratio is fixed to a predetermined value larger leaner than the stoichiometric air-fuel ratio.