JPS61255238A - Fuel controller for engine - Google Patents

Abstract

PURPOSE:To obtain the always superior combustion state by controlling the valve opening time of an injection valve according to the output of an air flow sensor when the output of an air-fuel ratio sensor is in lean side and carrying out the air-fuel ratio feedback control by using the output of the air flow sensor when the output is in rich side. CONSTITUTION:A heating wire type air flow sensor 7 is installed onto the upstream side of a throttle valve 6 in an intake pipe 5 whose downstream edge is connected to a surge tank 4. An air-fuel ratio sensor 10 for detecting the air-fuel ratio on the rich side on the basis of the exhaust gas component is installed onto an exhaust system, and the output signal is input into a controller 8. When the output signal of the air-fuel ratio sensor 10 is in the rich side with respect to a prescribed value previously determined, the because of the controller 8 valve opening time of a fuel injection valve 3 is controlled on the basis of the output signal of the air flow sensor 7. When the output signal of the air-fuel ratio sensor 10 shows rich, feedback control is performed so that the air-fuel ratio becomes equal to said prescribed value on the basis of the output signal of the air-fuel ratio sensor 10.

Description

Detailed Description of the Invention [Industrial Field of Application] This invention is applicable to fuel injection into a gasoline engine using an air flow sensor based on the heat dissipation principle (for example, a hot wire type air flow sensor), especially when the air flow sensor is used under high load. The present invention relates to an engine fuel control device with improved fuel ratio accuracy.

[Conventional technology]

FIG. 6 is a diagram showing the configuration of a conventional engine fuel control device. In this FIG. 6, 1 is an engine and 2 is an intake manifold. An electromagnetic fuel injection valve 3 is provided in this intake manifold r2, and the fuel injection valve 3 is controlled by a control device 8.

Further, the intake manifold P2 is connected to the surge tank 4, and the surge tank 41'i is connected to the intake pipe 5. A throttle valve 6 is disposed within the intake pipe 5. This intake pipe 5 is provided with a hot wire type air flow sensor 7. The output of the air flow sensor 7 is sent to a control device 8. ' Also, the rotation speed of the engine 1 is detected by a rotation detector 9, and the detection output is sent to the control device B. The control device 8 controls the fuel injection valve 3 based on the output of the rotation detector 9 and the output of the air flow sensor 7.

The control device 8 is configured as shown in FIG. 7, and the output of the air flow sensor 7 is converted into a digital signal by an A/D converter 81 and sent to a microprocessor 83.

Further, the output of the rotation detector 9 is sent to a microprocessor 83 through an interface circuit 82. In this way, the microprocessor 83 calculates the required amount of fuel based on the output of the air flow sensor 7 and the information from the rotation detector 9, amplifies it with the amplifier 86, and then controls the fuel injection valve 3. .

The microprocessor 83 includes RAM 84 and ROM 85.
is connected. RAM84 is used during calculation, and R
The OM85 stores calculation procedures and control data.

Next, the operation will be explained. Engine 1 is fully throttled (W
In operating conditions other than near OT), the output obtained from the air flow sensor 7 has a normal waveform that includes some pulls, as shown in (al) in Figure 8, and if the area of this waveform is calculated, it can be determined that the true intake air Since the amount is obtained, if the microprocessor 83 controls the pulse width of the fuel injection valve 3 based on the value obtained by dividing the intake air amount by the engine speed,
H [The desired air-fuel ratio can be controlled.

However, a specific rotation speed region near WOT (generally 1
000-3000 ppm), engine 1
Due to the air blowback, the output waveform of the air flow sensor 7 becomes as shown in FIG. 8(b), and the shaded portion is added to the true air needle.

This is because the hot wire type air flow sensor 7 detects and outputs the intake air amount regardless of the force in the air flow direction.

As shown in Figure 9, the detection error due to this blowback varies depending on the rotation speed, and normally the intake pipe negative pressure is -50 mnHg.
It originates from the vicinity and reaches a maximum of 5° in the WOT region.

If the fuel amount is calculated and injected using a value that includes such a large error, the air-fuel ratio will become significantly richer and cannot be used for practical purposes. Conventionally, as shown in Figure 10, an error is caused by blowback. For region a, the maximum air amount determined according to the engine is the upper limit (value shown by the broken line)
It is stored in the ROM 85 in the control device 8, and the (
Air flow sensor 7 shown in b) exceeds this value.
By ignoring the detected value and clipping it at the upper limit value, the air-fuel ratio is suppressed from becoming excessively rich.

[Problem that the invention seeks to solve]

By the way, this upper limit is lowland (sea 1 level)
Since it has to be set according to the intake air flow characteristics of the target engine at room temperature, it inevitably becomes the upper limit of the mass flow rate at room temperature at low altitudes.

However, if the air flow sensor 7 is operated under high load while driving at high altitudes where the air density is low, the average value of the output level of the air flow sensor 7 will not reach the predetermined upper limit as shown in (e) of FIG. The average value of the included output levels is used as is for fuel calculation, and as shown in Figure 11,
The drawback is that the air-fuel ratio becomes significantly richer as the altitude increases.

In this way, conventionally, a hot wire air flow sensor has been used to
When detecting the amount of intake air in a cylinder engine, when the throttle valve is fully opened, the intake air blows back against the airflow sensor, causing a backflow phenomenon, so the airflow sensor cannot detect the true amount of intake air, and the output is It becomes larger than the true value and causes an error.

This error value reaches approximately 50% when it is large, so
If the fuel amount is calculated using the same value, the air-fuel ratio will become significantly rich, making it impossible to operate the engine.

For this reason, conventionally, the upper limit value of the airflow sensor output is stored in advance in the memory of the control device according to the intake air amount characteristics of the engine, and the output value of the airflow sensor is abnormally large due to blowback. This was done to prevent large errors in the air-fuel ratio.

However, this method has the disadvantage that the upper limit value is determined in accordance with the engine at low altitudes near room temperature, and the error in the air-fuel ratio increases when driving at high altitudes or in high-temperature atmospheres.

This invention was made to solve these problems, and is an engine fuel that can eliminate air-fuel ratio errors caused by atmospheric pressure (at high altitudes) and intake air temperature, and can ensure stable combustion under all engine operating conditions. The purpose is to obtain a control device.

[Failure to solve the problem]

A fuel control device for an engine according to the present invention is provided with an air-fuel ratio sensor capable of detecting an air-fuel ratio in a rich region from exhaust gas components.

[For production]

In this invention, feedback control is performed using the air-fuel ratio sensor to prevent the air-fuel ratio from becoming richer than a predetermined value, and even if there is an abnormal increase in the air flow sensor output signal caused by blowback of intake air, the air-fuel ratio sensor Clip the enrichment to a predetermined value.

〔Example〕

Embodiments of the engine fuel control device of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing the entire configuration of one embodiment. In FIG. 1, the same parts as in FIG. I will mainly discuss the parts.

As is clear from comparing Figure 1 with Figure 6,
In the figure, an air-fuel ratio sensor 10i is newly added to the configuration shown in FIG. 6, and the air-fuel ratio sensor 10 is capable of detecting an air-fuel ratio i1J from the exhaust gas components of the engine. The other configurations are the same as in FIG. 6.

As shown in FIG. 2, this air-fuel ratio sensor 10 is configured to send an output to an A/D controller 81 within the control device 8. This FIG. 2 corresponds to the conventional control device shown in FIG. 7, and the configuration of this FIG. 2 also has a new configuration in FIG.
The difference from FIG. 7 is that the configuration is configured so that the data is sent to 1, and the other configurations are the same as FIG. 7.

As a sensor capable of linearly detecting the air-fuel ratio, a zirconia-type oxygen battery that exhibits switching characteristics at the stoichiometric air-fuel ratio point has traditionally been used (one side is the atmosphere and the other side is supplied with exhaust gas that is affected by the oxygen pump). A combination of an oxygen pump and an oxygen pump is well known.
It was confirmed that the air-fuel ratio on the rich side could also be detected by applying a voltage to the oxygen pump and operating it so as to completely reduce the oxygen in Co2 and supply oxygen to the anti-atmospheric pressure side of the oxygen cell. ing. The output voltage of the air-fuel ratio sensor 10 with respect to the air-fuel ratio is as shown in FIG.

In the above configuration, the operation when the engine 1 is operated to full load will be explained in detail with reference to the time chart of FIG. 4 and the flow chart of FIG. 5. Figure 4(a)
As shown in Figure 4(b), as the throttle opening increases, the output of the airflow sensor 7 becomes excessive than the true value due to the blowback of intake air, so the air-fuel ratio shifts to the rich side as shown in (a) of Figure 4(b). However, when the air-fuel ratio sensor 10 detects the actual air-fuel ratio and reaches a value α (for example, air-fuel ratio 12), the air-fuel ratio changes to a curve (b) centered around α. ), the noggle width of the fuel injector 3 (
FIG. 4(C)) is also feedback-controlled like (bl), so a stable combustion state can be ensured.

In the actual control procedure, as shown in FIG. 5, in step 100, the main ξ parameters, ie, the intake air amount Qa and the engine speed Nef are read, and in the next step 101, the fuel injection valve 3 is read from these input information. Driving nose ξ width τ
Bk is calculated, and in the next step 102, it is determined whether the output of the air-fuel ratio sensor 10 is larger than a predetermined air-fuel ratio α (for example, 12), and if it is larger (lean side), the final drive noise ξ pulse width τ is determined. is determined to be τB (step 104).

If the air flow sensor 7 is affected by blowback, the driving pulse width τB of the fuel injection valve 3 becomes excessive and the air-fuel ratio becomes α.
If the deviation is small (rich side), a flag is set in step 105 as shown in FIG. 4(e), and an integral correction term (CFB) 'e4 is set in step 106 as shown in FIG. 4(d).
Shift to the X side, steps 1.08 to 11
0, the air-fuel ratio is shifted to the lean side by setting the injector driving noggle width τC=τB X CFB as shown in FIG. 4(c).

As a result, if the air-fuel ratio becomes thicker than α (lean side), the integral correction term (CpB) 'e
Fig. 4 (Increase as dl and shift to rich side.

This operation is repeated, and the actual air-fuel ratio is feedback-controlled around the air-fuel ratio α as described above. This operation continues while the drive pulse width τC of the fuel injection valve 3 due to the foot nosec control is smaller than the drive pulse width τB of the fuel injection valve 3 calculated from the intake air amount Qa and the rotational speed Ne, and τC When it becomes larger than τB, the flag is reset in step 111, and the fuel injection valve 3 is controlled with a pulse width of τB.

In the above explanation, the air-fuel ratio sensor 10 capable of linearly detecting the air-fuel ratio on the rich side was used to perform foot nosec control. It goes without saying that the same effect can be obtained by using a device whose output is reversed.

〔Effect of the invention〕

As explained above, this invention detects the air-fuel ratio on the rich side with an air-fuel ratio sensor and suppresses air-fuel ratio errors caused by the blowback phenomenon of intake air in the fully open region of the engine. A stable combustion state can be ensured under all operating conditions.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the overall configuration of an embodiment of the engine fuel control device of the present invention, FIG. 2 is a block diagram showing the internal configuration of the control device in the engine fuel control device of FIG. 1, and FIG. The figure is a characteristic diagram of the air-fuel ratio sensor in the fuel control device for an engine of this invention, FIG. 4 is a time chart for explaining the invention in detail, and FIG. 5 is a flowchart of the operation of the fuel control device for this engine. Flowchart, No. 6
The figure shows the overall configuration of a conventional engine fuel control device, FIG. 7 is a block diagram showing the internal configuration of the engine fuel control device shown in FIG. 6, and FIG. A characteristic diagram of the air flow sensor in the engine fuel control device, Fig. 9/fi A diagram showing the detection error of the air flow sensor in the engine fuel control device of Fig. 6, Fig. 10
The figure is a diagram showing the output characteristics of the above air flow sensor with respect to the engine rotation speed, and FIG. 11 is a diagram showing the error with respect to altitude due to the above air flow sensor in a conventional engine fuel control device. DESCRIPTION OF SYMBOLS 1... Engine, 3... Fuel injection valve, 6... Throttle valve, 7... Air flow sensor, 8... Control device, 9
... Rotation detector, 10... Air-fuel ratio sensor. Note that the same reference numerals in the figures indicate parts corresponding to the same straddle. Agent Masu Oiwa Pheasant Figure 1 2: Possible V Satsuma manifold 3 varnish'? 9 → Screw I Monument Valve 4: Zar 7 Tanok 5: Tsuki Fortress Pipe 6: Heavy Monument Valve 7: Air Flow Sensor 9: Regeneration T Moxibustion Type 102 Sky IP'几 13 N'i Bucerl Newsletter Sungetsu-Haikime Figure 11 (m)

Claims (1)

[Claims] an air flow sensor that detects the intake air amount of the engine based on the heat dissipation principle; an air-fuel ratio sensor that detects a rich air-fuel ratio based on the exhaust gas components of the engine; an electromagnetic fuel injection valve that injects fuel into the engine; When the signal of the air-fuel ratio sensor indicates leaner than the predetermined value, the valve opening time of the fuel injection valve is controlled using the signal of the air flow sensor as a main parameter, and the signal of the air-fuel ratio sensor is set to the predetermined value. 1. A fuel control device for an engine, comprising: a control device that performs feedback control so that the air-fuel ratio becomes the predetermined value based on a signal from the air-fuel ratio sensor when the air-fuel ratio is richer than the predetermined value.