JPH0530984B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electronically controlled fuel injection device that prevents overheating of an exhaust system.

Electronically controlled fuel injection systems in which fuel is supplied from a fuel injection valve to an intake passage have conventionally included ignition timing control means for retarding ignition timing during high temperature periods in order to avoid knocking when the engine is in a high temperature state.

However, if the ignition timing is delayed, the air-fuel mixture will continue to burn even after it is discharged to the exhaust system, so in the conventional electronically controlled fuel injection system described above, the exhaust temperature will rise, causing damage to exhaust system parts and contact overheating. It may bring.

SUMMARY OF THE INVENTION In view of the above, an object of the present invention is to provide an electronically controlled fuel injection system that can retard ignition timing to avoid knocking without overheating the exhaust system.

In order to achieve this object, the present invention provides a first fuel increase means for increasing the amount of fuel to prevent a rise in exhaust temperature when the engine is under high load, and a means for retarding the ignition timing to avoid knocking when the engine is in a high temperature state. In an electronically controlled fuel injection device having an ignition timing control means for performing angle control, when the engine is in a high temperature state where the ignition timing retard control is performed and the engine is under high load, the first fuel increasing means A second fuel increase means for increasing the amount of fuel to a greater extent than the amount of fuel is provided.

With the above configuration, in the present invention, when the engine is detected to be under high load when the engine is in a high temperature state and the ignition timing retard control is executed to avoid knocking, the second fuel increase means is activated. As a result, a larger amount of fuel is increased, which improves the combustion of the air-fuel mixture in the combustion chamber, and avoids a situation where combustion continues in the exhaust system, making it possible to avoid an increase in exhaust temperature. The reason why the increase in the fuel injection amount is limited to the high load period of the engine is to prevent engine stall from occurring due to execution of combustion injection during the idling period.

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is an overall schematic diagram of an internal combustion engine equipped with an electronically controlled fuel injection device to which the present invention is applied.
An air flow meter 2, an intake temperature sensor 3, a throttle valve 4, a surge tank 5, and an intake pipe 6 are provided in the intake passage 1 in this order from upstream. The fuel injection valve 7 is attached to the intake pipe 6 and injects fuel into the intake passage 1. The bypass passage 8 is provided in parallel with the intake passage portion where the throttle valve 4 is provided, and is provided with an ISC (idle speed control).
A valve 9 controls the flow area of the bypass passage 8.

The control chamber 11 is provided with a spark plug 12, is defined by a cylinder head 13, a cylinder block 14 and a piston 15, and is supplied with an air-fuel mixture via an intake valve 16. The air-fuel mixture combusted in the combustion chamber 11 is discharged to the exhaust pipe 20 via the exhaust valve 19. An oxygen sensor 21 detects the oxygen concentration in exhaust gas, and a water temperature sensor 22 is attached to the cylinder block 14 to detect the temperature of cooling water. The cylinder discrimination sensor 25 and the rotation angle sensor 26 detect the crank angle from the rotation of the shaft 28 of the power distributor 27. Cylinder discrimination sensor 2
5 and rotation angle sensor 26 generate pulses every time the crank angle changes by 720° and 30°, respectively.

The power switch 29 detects whether the throttle valve 4 is opened at an angle of 60 degrees or more in terms of the throttle shaft angle. The power switch 29 is turned on when the throttle valve 4 is opened at an angle of 60° or more in terms of the angle of the throttle axis (in other words, when the engine is in a high load state), and the power switch 29 is turned on when the throttle valve 4 is opened at an angle of 60° or more in terms of the angle of the throttle axis.
is off when the opening is less than (i.e., when the engine is under low load). Electronic control device 31
receives input signals from various sensors and sends output signals to the fuel injection valve 7, ISC valve 9, and ignition device 32. The secondary ignition current of the ignition device 32 is sent to the spark plug 12 via the power distributor 27.

FIG. 2 is an internal block diagram of the electronic control unit 31. The RAM 35, ROM 36, CPU 37, input/output ports 38, 39, and output ports 40, 41 are connected to each other via a bus 42. CLOCK
43 sends a clock pulse to the CPU 37. The analog outputs of the air flow meter 2, intake temperature sensor 3, and water temperature sensor 22 are buffers 45, 46,
The signal is sent to multiplexer 48 via 47. The multiplexer 48 selects an input signal, and the selected input signal is A/D converted by an A/D (analog/digital) converter 49 and then sent to the input/output port 38.

The output of the oxygen sensor 21 is sent to the input/output port 39 via the buffer 50 and the comparator 51, and is sent to the input/output port 39, and is sent to the cylinder discrimination sensor 25 and the rotation angle sensor 26.
The output of the power switch 29 is sent to the input/output port 39 via the shaping circuit 53, and the output of the power switch 29 is sent directly to the input/output port 39. ISC valve 9 is input/output port 3
The fuel injection valve 7 receives an input signal from the output port 40 via the drive circuit 55, and the ignition device 32 receives an input signal from the output port 40 via the drive circuit 55.
1 through a drive circuit 56 .

In the internal combustion engine having the above configuration, the electronic control device having the configuration shown in FIG. 2 implements the first fuel increasing means and the second fuel increasing means by executing the fuel injection routine shown in FIG. .

When the fuel injection amount calculation routine shown in FIG. 3 is started, it is first determined whether the power switch 29 is on or not (step 62). As described above, the power switch 29 is a switch that is turned on when the throttle valve 4 is opened at an opening of 60 degrees or more, and turned off when the throttle valve 4 is opened at an opening of less than 60 degrees. When the power switch 29 is off, the process proceeds to step 72 without executing the fuel increase process, which will be described later.

When the power switch 29 is off, the engine is in a light load state including the idling period, but during the idling period the engine operating state is unstable and it is necessary to maintain an appropriate air-fuel ratio. There is a possibility that the engine will stop operating due to a misfire or a fogging of the spark plug. Therefore, the fuel injection amount is not increased during the idling period.

On the other hand, when it is determined that the power switch 29 is on, the intake air amount is large and the load is high, and the process proceeds to step 64 to calculate the power increase coefficient _Fv . _Fv is, for example, a proportional increase function of the intake air flow rate Q, and is a conventionally known coefficient that determines the amount of fuel increase that is performed when the engine is under high load to prevent the exhaust temperature from rising.

Next, proceed to step 66 to check the engine cooling water temperature.
Determine whether T _w is 95°C or higher. When the engine cooling water temperature T _w is 95° C. or higher, the engine is in a high temperature state and the ignition timing is retarded to avoid knocking by an ignition timing control routine (not shown).

If it is determined in step 66 that T _w <95°C, the high temperature condition is not present, and the process proceeds to step 72, where calculation of the fuel injection amount to increase the amount of fuel at high load is performed as in the conventional case. T _w ≧95℃ in step 66
When it is determined that this is the case, the engine is in a high temperature state where ignition timing retard control is being executed, and in this case, the process advances to step 68 to calculate the increase coefficient _Fw for preventing a rise in exhaust gas temperature.

For example, as shown in Fig. 4, F _w is expressed by a linear increasing function that linearly increases from "0.00" to "0.04" as the engine cooling water temperature T _w increases from 95 °C to 105 °C. It is calculated according to the engine cooling water temperature _Tw .

Next, the process proceeds to step 70, where the power increase coefficient _Fv calculated at step 64 and the exhaust temperature rise prevention increase coefficient _Fw calculated at step 68 are added, and the addition result is set as _Fv . Therefore,
When the engine is in a high temperature state (T _w ≧95°C) where ignition timing retard control is executed and when the engine is under high load (power switch 29 is on), the normal exhaust temperature rise prevention method calculated in step 64 is performed. This means that the amount of fuel will be increased by _Fw , which is greater than the increase in fuel amount for this purpose.

In step 72, the final fuel injection amount T _au is calculated from the following equation.

T _au = T _b・(1+F _v )・F _x where T _b : Basic fuel injection amount calculated from intake air flow rate Q/engine rotation speed N. _x : Other correction coefficients calculated from intake air temperature and feedback amount. Thus, according to this embodiment, step 72
Based on _the final fuel injection amount T _au calculated by
When the engine cooling water temperature T _w is at a high temperature of 95° C. or higher during execution of the ignition timing retard control, fuel injection is performed to increase the amount by the exhaust temperature rise prevention increase coefficient F _w .

As described above, according to the present invention, in an electronically controlled fuel injection system in which the ignition timing is delayed to avoid knocking when the engine is in a high temperature state, when the throttle opening is at a high load of more than a predetermined value, the conventional By increasing the amount of fuel injection rather than increasing the amount of fuel to prevent a rise in exhaust temperature, this improves the combustion of the air-fuel mixture in the combustion chamber and suppresses combustion in the exhaust system when the ignition timing is delayed. Overheating of the exhaust system can be prevented. Also, since fuel injection is not increased during idling,
It is possible to prevent the engine from stopping due to an increase in the amount of fuel injection during the idling period.

[Brief explanation of the drawing]

Fig. 1 is an overall schematic diagram of an internal combustion engine equipped with an electronically controlled fuel injection device to which the present invention is applied, Fig. 2 is a block diagram of the electronic control device shown in Fig. 1, and Fig. 3 is a calculation of the fuel injection amount. Routine flowchart, part 4
The figure is a graph showing a function between engine cooling water temperature and exhaust temperature rise prevention increase coefficient. 1...Intake passage, 7...Fuel injection valve, 22...
Water temperature sensor, 29... power switch, 31... electronic control device, 32... ignition device.

Claims (1)

[Scope of Claims] 1. A first fuel increase means for increasing the amount of fuel to prevent a rise in exhaust temperature when the engine is under high load, and a retard control of the ignition timing to avoid knocking when the engine is in a high temperature state. In an electronically controlled fuel injection device having an ignition timing control means for performing ignition timing retardation control, when the engine is in a high temperature state where the ignition timing retard control is performed and the engine is under high load, the fuel amount is increased by the first fuel amount increase means. An electronically controlled fuel injection device characterized by comprising a second fuel increasing means for increasing the amount of fuel by a large amount.