JPS6093149A - Fuel injection device in internal-combustion engine - Google Patents

Abstract

PURPOSE:To burn unburnt gas within a catalyst to aim at enhancing the purification factor of exhaust gas, in a fuel injection device in which the air-fuel ratio of the engine is made leaner than a stoichiometric air-fuel ratio upon steady state running condition, by increasing the amount of fuel injection at every predetermined fuel injection cycle number. CONSTITUTION:In a fuel injection device in an internal-combustion engine, there are provided a throttle switch 6 which is associated with a throttle valve 4 positioned downstream of an intake-air temperature sensor 2 and which is turned on when the throttle valve 4 is fully closed but is turned off when the throttle valve is opened, and a pressure sensor 10 in a surge tank 8. Further, fuel injection valves 16 are provided in an engine intake manifold, for each engine cylinders, and combustion chambers 14 in the engine 14 are communicated with a catalyst converter 15 in which a ternary catalyst is charged through an exhaust manifold 18. In a distributor 24, there are provided an engine cylinder discriminating sensor 26 and an engine rotational speed sensor 28 whose signals are delivered to a control circuit 30 so that the amount of fuel is increased at every predetermined cycle number.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a fuel injection device for an internal combustion engine. The present invention relates to a fuel injection device for an internal combustion engine that injects fuel so that the air-fuel ratio becomes the stoichiometric air-fuel ratio when the engine is not in operation.

[Background of the invention]

Conventionally, a three-way catalyst has been used to simultaneously purify carbon monoxide, hydrocarbons, and nitrogen oxides in exhaust gas, and in order to improve the purification rate of this three-way catalyst, an O2 sensor is used to Feedback control is performed to detect the residual oxygen concentration, estimate the air-fuel ratio, and control the air-fuel ratio to near the stoichiometric air-fuel ratio. In performing this feedback control, the basic fuel injection time TP determined by the engine load (intake pipe pressure PM or intake air amount Q per engine revolution, /N Fli ) and engine speed is set to 0! Based on the air-fuel ratio signal output from the sensor and subjected to signal processing, the fuel injection time T is multiplied by the air-fuel ratio feedback correction coefficient FAF for performing proportional integral operation on the fuel injection time.
The air-fuel ratio is controlled to be close to the stoichiometric air-fuel ratio by opening the fuel injection valve for a time corresponding to the fuel injection time TAU after AU.

In addition, from the perspective of lowering the fuel ratio, it has recently been proposed to perform lean control in which the air-fuel ratio is feedforward controlled to the lean side from the stoichiometric air-fuel ratio under predetermined conditions during feedback control, that is, during steady engine operation. has been done.

The above air-fuel ratio control calculates the fuel injection time TAU based on the following equation (1) and injects a predetermined amount of fuel.

T A U = T P , F A F , F (
t) ・・・・・・・・・・River...(1) However, F(
t) is a correction coefficient such as a warm-up increase coefficient and a start-up increase coefficient.

Therefore, according to the air-fuel ratio control method, 0! Since the air-fuel ratio feedback correction coefficient FAF changes around 1 according to the sensor output, the air-fuel ratio is controlled to become the stoichiometric air-fuel ratio, and the air-fuel ratio feedback correction coefficient FAF is set to a predetermined value less than 1 (for example, 0.8 ), feedforward control is performed.

However, in the air-fuel ratio lean control described above, there is a problem in that since there are few reactive components in the three-way catalyst, the catalyst temperature becomes low and the exhaust gas purification rate deteriorates.

In order to solve the above problem, an engine is known in which the air-fuel ratio is made rich in half of the cylinders during lean control, as shown in Japanese Utility Model Application Publication No. 49-84522. However, in this engine, half of the cylinders are made rich, so
There is a problem in that lean control cannot be expected to improve fuel efficiency.

[Purpose of the invention]

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a fuel injection device for an internal combustion engine that improves the exhaust gas purification rate during lean control without deteriorating fuel efficiency.

[Structure of the invention]

In order to achieve the above object, the present invention provides a fuel injection device for an internal combustion engine that injects fuel so that the air-fuel ratio becomes leaner than the stoichiometric air-fuel ratio during steady engine operation. It is characterized by being configured to increase the amount. As a result of increasing the fuel injection amount, unburned exhaust gas is combusted in the catalyst and the catalyst temperature increases, so that the purification rate of exhaust gas can be improved.

〔Effect of the invention〕

According to the above configuration of the present invention, since the fuel injection amount is increased every predetermined number of injections, the fuel consumption is not deteriorated compared to the case where half the cylinders are made rich at the negative rate. The effect is that the exhaust gas purification rate can be improved.

[Embodiments of the invention]

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a schematic diagram showing an embodiment of the present invention. An intake temperature sensor 2 is installed downstream of an air cleaner (not shown) to detect the temperature of intake air and output an intake temperature signal. A throttle valve 4 is located downstream of the intake temperature sensor 2.
A throttle switch 6 is attached which is interlocked with the throttle valve 4 and turns off when the throttle valve is on when the throttle valve is fully closed. A surge tank 8 is provided downstream of the throttle valve 4, and a pressure sensor 10 is attached to the surge tank 8 to detect the intake pipe pressure downstream of the throttle valve and output an intake pipe pressure signal. The surge tank 8 is communicated with a combustion chamber 14 of the engine via an intake manifold 12. This intake manifold 12 is connected to a catalytic converter 15 filled with a fuel injection valve 16 catalyst. Further, a water temperature sensor 20 that detects the engine cooling water temperature and outputs a water temperature signal is attached to the engine block. A spark plug 22 is provided in the combustion chamber 14 of the engine.
The tip of the spark plug 22 is protruded, and the spark plug 22 is connected to a distributor 24. The distributor 24 is provided with a cylinder discrimination sensor 26 and an engine rotation speed sensor 28, which each include a pickup fixed to the distributor housing and a signal rotor fixed to the distributor shaft. The cylinder discrimination sensor 26 outputs a cylinder discrimination signal to the control circuit 30 made up of a microcomputer or the like every 720 degrees CA, for example, and the engine rotation speed sensor 28 outputs an engine rotation speed signal to the control circuit 30 every 30 degrees CA, for example. Output. Further, the distributor 24 is connected to the igniter 32.

In addition, the exhaust manifold is equipped with a sensor 3 that detects the residual oxygen concentration in the exhaust gas and outputs an air-fuel ratio signal.
4 and an exhaust gas temperature sensor 35 that detects the temperature of exhaust gas and outputs an exhaust temperature signal.

As shown in FIG. 2, the control circuit 30 includes a central processing unit (C
PU) 36, read-only memory (ROM) 38, random access memory (RAM) 40, backup RAM (BU-RAM) 42, input/output board (Ilo) 44
, an analog/digital converter (ADC) 46b, and buses such as a data bus and a control bus that connect these. A cylinder discrimination signal, an engine rotational speed signal, an air-fuel ratio signal, and a throttle signal output from the throttle switch 6 are input to the engine 1044, and a fuel injection controller 1044 controls the opening/closing time of the fuel injection valve 16 via a drive circuit. A signal and an ignition signal that controls the on/off time of the igniter 32 are output.

The ADC 46 also includes an intake pipe pressure signal, an intake temperature signal,
An exhaust temperature signal and a water temperature signal are input and converted into digital signals according to instructions from the CPU. ROM38 above
The processing routine program described below, a map of the basic fuel injection amount determined by the intake pipe pressure and engine speed, and the number of fuel injections for lean control shown in Fig. 3 (11 to (6)) are included. One of the maps for which N is determined is stored in advance.

The number of fuel injections N in the map m, (21, +41 in Fig. 3) increases as the fuel injection amount (fuel injection time), exhaust temperature (or catalyst temperature), and intake pipe pressure increase. It is determined.

The number of fuel injections N in FIG. 3(3) is determined to decrease as the engine speed increases. In addition, in an engine where the basic fuel injection time is determined based on the intake air amount per engine rotation and the engine rotation speed, instead of the pressure sensor 10, a suction sensor is installed between the air cleaner and the throttle valve 4 as shown in FIG. An air flow meter 11 is attached to detect the amount of air and output an intake air amount signal.

Note that the other configurations are the same as those in FIG. 1, so their description is omitted.

In such an engine, as long as the intake air amount is detected, it is possible to use the map shown in FIG. 3 (5) or (6) instead of the map shown in FIG. 3 (4).

It is also possible to attach an air flow meter to the engine shown in FIG. 1 and use the map shown in FIG. 3 (5) or (6).

Next, a processing routine of an embodiment in which the present invention is applied to the engine shown in FIG. 1 will be described with reference to FIG. First, in step 99, various operating conditions such as intake pipe pressure PM and engine speed are taken in, and then in steps 100 to 1.
In step 04, it is determined whether the lean control conditions are satisfied. In step 100, it is determined whether or not the engine is in the engine starting state. If the engine is in the engine starting state, the count value C0UNT of the counter that counts the number of injections is entered in step 98.
is set to O, and then in step 112 0. An air-fuel ratio feedback correction coefficient FAF for feedback control is calculated based on the output signal of the sensor. Whether or not the engine is in the starting state can be determined based on the on/off state of the throttle switch 6 and the engine rotational speed, and the engine is determined to be in the starting state when the throttle switch is on and the engine rotational speed is below a predetermined value (for example, 500 rpm). When the engine is not in the starting state, it is determined in step 101 whether or not the engine is being warmed up based on the engine cooling water temperature.

When it is determined that the engine cooling water temperature is below a predetermined value (for example, 80° C.) and the engine is being warmed up, it is determined whether the stencil valve is open. When the throttle switch is on, that is, during idling, the process proceeds to step 98, and when the throttle switch is off, it is determined in steps 103 and 104 whether or not the engine is in a steady state.

In this embodiment, the intake pipe pressure PM is within a predetermined range (A<PM(
B ) and the absolute value of the rate of change of intake pipe pressure PM is 1
When ΔPMI is less than or equal to a positive predetermined value C, it is determined that the engine is in a steady state. When the intake pipe is closed, that is, in a transient state such as during acceleration or deceleration, the process proceeds to step 98. After calculating the air-fuel ratio feedback correction coefficient FAF in step 112, the flag F is reset in step 113, fuel injection is performed in step 110, and the count value C0UNT is incremented by 1 in step 111 to count the number of fuel injections. .

If it is determined in steps 100 to 104 that the lean control conditions are satisfied, step 105
It is determined whether flag F is set. If the flag F has been reset, in step 106, the number N of fuel injections is determined by interpolation from the map of the number of fuel injections stored in the ROM. In the next step 107, the count value C0UNT is compared with the number of fuel injections N determined from the map, and if the count value C0UNT is greater than or equal to the number N of fuel injections, a flag F is set in step 108. If it is less than N, the process directly advances to step 109.

In step 109, the air-fuel ratio feedback correction coefficient F
Set AF to a constant value less than 1 (for example, 0.8),
In step 110, fuel injection is performed to perform air-fuel ratio lean control.

On the other hand, when it is determined in step 105 that the flag F is set, that is, when the fuel injection for lean air-fuel ratio control has been executed N times, the count value C0UNT is set to 0 in step 114, and the count value C0UNT is set to 0 in step 115. After setting the value of the fuel ratio feedback correction coefficient FAF' to a constant value larger than the value during lean control (for example, 1.1, this value is about 13 in terms of air-fuel ratio), the flag F is reset in step 116, and the flag F is reset in step 116. At step 110, fuel injection is performed to increase the fuel injection amount.

As a result of the above, during lean control, the fuel injection amount is increased once every N fuel injections.

In the engine shown in Fig. 4, the amount of intake air Q/N per engine revolution is within a predetermined range (A < Q/N
By determining whether the value is within <B) and whether the absolute value 1ΔQ,/N1 of the rate of change of the intake air amount Q/H per engine rotation is less than a positive predetermined value C, It is determined whether the engine is in a steady state.

As explained above, in this embodiment, since the timing to increase the fuel injection amount is determined according to the engine operating state, the effect of further improving fuel efficiency can be obtained.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram showing an example of an engine to which the present invention is applied, Fig. 2 is a block diagram showing details of the control circuit shown in Fig. 1, and Figs. 3 (1) to (6) show the number of fuel injections. FIG. 4 is a diagram showing a map, FIG. 4 is a partial schematic diagram showing another engine to which the present invention is applied, and FIG. 5 is a flowchart showing a processing routine of an embodiment of the present invention. 4... Throttle valve, 10... Pressure sensor, 16... Fuel injection valve, 30... Control circuit. Agent Tatsuyuki Unuma (and 1 other person) Figure 3 (1) (2) (11:00 p.m. pH) (5 degrees) (5) (6) JP-A-Sho GO-93149 (6) Figure 4

Claims (1)

[Claims] (1) A fuel injection device for an internal combustion engine that injects fuel so that the air-fuel ratio becomes leaner than the stoichiometric air-fuel ratio during engine steady operation, characterized by being configured to increase the fuel injection amount every predetermined number of fuel injections. Fuel injection system for internal combustion engines.