JPH01123141A - Air-fuel-ratio control apparatus for internal combustion engine - Google Patents

Abstract

PURPOSE:To make it possible to perform accurate control, by detecting the output voltage of the oxygen battery cell of a broad range air fuel ratio sensor with a detecting circuit of the electromotive force of the oxygen battery, judging the active state of the broad range air fuel ratio sensor based on the output signal from the detecting circuit, and controlling the current for an oxygen pump. CONSTITUTION:A detecting circuit 82a for the electromotive force of an oxygen battery cell, which detects the output voltage of the oxygen battery cell 82, is added to the constitution of a conventional broad range air fuel ratio sensor 8. The output signal Vs is inputted into a control device 9. The current for an oxygen pump is controlled with a pump-current driving output circuit 97 by using a microprocessor 93. When the output voltage Vs of the cell 82 is less than a specified value not only when an engine is started but also when the engine is operating, it is judged that the sensor 8 is abnormal. The current for the oxygen pump is stopped. This state is maintained until the specified value is exceeded. Therefore, the measuring accuracy of the air fuel ratio with the sensor 8 is improved, and stable feedback fuel control based on the air fuel ratio can be performed.

Description

Detailed Description of the Invention [Industrial Applications] This invention is particularly useful when performing air-fuel ratio feedback control of an internal combustion engine using a wide-range air-fuel ratio sensor capable of detecting air-fuel ratios from lean to rich. The present invention relates to an air-fuel ratio control device for an internal combustion engine, which improves the detection accuracy of an air-fuel ratio sensor during sudden acceleration and deceleration, and at low temperatures, and improves the air-fuel ratio control performance of the engine.

[Conventional technology]

FIG. 7 is a configuration diagram of a conventional air-fuel ratio control device for an internal combustion engine disclosed in, for example, Japanese Unexamined Patent Publication No. Sho J31-204559. Intake pipe 3 is a throttle valve provided in this intake v2.

The pressure within this intake pipe 2 is detected by a pressure sensor 4, and its detection output is sent to an AD converter 91.

Further, the rotation of the internal combustion engine 1 is detected as a pulse by the rotation sensor 5, and the output of the rotation sensor 5 is sent to the input/output circuit 92.

Further, fuel is injected by a 1fifi pipe 2 hinge injector 6, and this injector 6 is driven by the output of an output circuit 96.

Further, an exhaust pipe 7 is connected to the internal combustion engine 1, and this exhaust pipe II! ! An output corresponding to the air-fuel ratio of the exhaust gas components in the near area is sent from the wide-range air-fuel ratio sensor 8 to the AD converter 91.

On the other hand, 9 is a control device that calculates the required amount of fuel from information such as the pressure sensor 4, rotation sensor 5, wide range air-fuel ratio sensor 8, and cooling water temperature sensor 1o, and generates a drive pulse width for the injector 6.

The AD converter 91 in the control device 9 converts analog signals from the wide range air-fuel ratio sensor 8, pressure sensor 4, etc. into digital values and sends them to the microprocessor 93.

Further, the input circuit 92 is an input circuit for converting the level of the pulse input signal of the rotation sensor 5, and its output is also sent to the microprocessor 93.

This microprocessor 93 calculates the amount of fuel to be supplied to the internal combustion engine 1 based on the digital and pulse signals obtained from the AD converter 91 and the input circuit 92, and changes the drive pulse width of the injector 6 according to the result. This outputs the following.

Control procedures and data for the microphone processor 293 are stored in advance in a ROM 94, and data in the calculation process is temporarily stored in a RAM 95.

The injector 6 is driven by an injector drive output port 96 in accordance with an output signal from the microprocessor 93.

The wide range air-fuel ratio sensor 8 in FIG. 7 above is constructed as shown in FIG. 8, and 81 is a solid electrolyte oxygen pump cell (
82 is a solid electrolyte oxygen battery cell (hereinafter referred to as an oxygen battery cell), 83m, 83b and 83e are porous electrodes, 84 is a diffusion chamber, 85
is a reference voltage source, 86 is a comparison amplifier that compares the reference voltage of the reference voltage source 85 and the voltage of the oxygen battery cell 82, 87 is a pump drive circuit, and 88 is for detecting the oxygen pump current (hereinafter referred to as pump current). A resistor, 89 is a heater for keeping the sensor at the activation temperature, and 90 is a control circuit.

The configuration of this wide range air-fuel ratio sensor 8 is already known (for example, Japanese Patent Laid-Open No. 60-128349, Japanese Patent Laid-Open No. 59-67455).
When the signal Sh output from the heater control drive output circuit 98 of the control device 9 in FIG. 7 is turned on after the engine is started, the heater is energized and the wide range air-fuel ratio sensor 8 is maintained at a predetermined temperature. When the output signal Sc of the pump current drive output circuit 97 is further turned on, the pump IB! The output circuit 87 starts operating, and the comparator amplifier 86 compares the voltage of the reference voltage source 85 (approximately 0.4 V) and the voltage of the oxygen battery cell 82 .

Based on this result, a current is applied to the oxygen pump cell 81 via the pump drive circuit 87 so that the deviation becomes zero, so that the exhaust gas in the diffusion chamber 84 becomes equivalent to the stoichiometric air-fuel ratio. be.

Using this principle, it is possible to detect both leaner and richer sides than the stoichiometric air-fuel ratio, and the measurement results can be extracted as the voltage across the resistor 88. An output voltage that is linear over the range can be obtained. Based on this output voltage η, the fuel injection amount is feedback-controlled by the control device 9 so as to achieve a desired air-fuel ratio.

Next, the operation will be explained according to FIGS. 9 and 10. 9 and 10 are execution flowcharts of the program for wide range air-fuel ratio sensor control written in the ROM 94, and represent the control procedure of the 1ltlJtl device 9 in the form of a flowchart.

FIG. 9 shows a detection start timing calculation procedure, which is repeatedly executed at irregular intervals between interrupt processing.

First, in step 201, it is determined whether or not the rotational speed N exceeds the internal combustion engine starting determination rotational speed (for example, 400 rpm), and in the case of N440 orpm, it is determined that starting has not yet been completed, and the heater is turned off in steps 2o2 and 203, respectively. The output of the control circuit drive signal Sh and pump drive start signal Sc is stopped (if already stopped, the stops are maintained), and the process returns.

On the other hand, if N>40 Orpm, it is determined that the start is complete and the process proceeds to step 204.

In step 204, the heater control circuit drive signal Sh
Determine whether there is an output. Heater control circuit drive signal Sh
If not, output of the heater control circuit drive signal Sh is first started in step 205, and then in step 206.
Read the cooling water temperature at that time, and then proceed to step 2.
At step 07, a pump drive start signal S is generated based on the cooling water temperature.
The output start timings Tf and T of , , are looked up in a table.

This output start timing TIT is the timing at which the wide range air-fuel ratio sensor 8 starts detecting the exhaust air-fuel ratio, and is set in the form of an elapsed time from the time when the output of the heater control circuit drive signal Sh starts.

Next, in step 208, the rotational speed N and fuel injection amount T2 are read. Fuel injection l- is calculated by another routine (not shown) according to the following equation.

T, = -Pb-+7, where K is a constant, 1. is a predetermined filling efficiency corresponding to the intake pressure Pb and the rotational speed N.

In step 209, the subtraction value T1. is used to subtract from the output start timing T at regular intervals based on the rotation speed N and the fuel injection amount T2. ,. table lookup. The output start timings T and T and the subtraction value Tiub are used in a program described later.

Further, in step 204 above, the heater control circuit drive signal S
If it is determined that h has already been output, step 2
Proceed to 08 to check the operating state, that is, the rotation speed N and the fuel injection amount T1
Subtract value T, depending on. Table lookup for ゎ.

FIG. 10 shows a detection start timing execution program, and this program is executed once every predetermined time based on the result of the detection start timing calculation shown in FIG. 9.

In step \115, it is determined whether or not the pump drive start signal S0 is being output. If not, in step 116, the pump drive start signal Sc% output start timing Ts□ is calculated according to the following equation.

T=T −T However, TS7: Output start timing value of the pump drive start signal S00 of the current processing routine, T, T1: Output start timing value of the pump drive start signal S of the previous processing routine, Next, in step 117 It is determined whether or not T6a≦0, and if T,1≦0, it is determined that the detection timing has come, and a pump drive start signal S is output in step 118.

As a result, the oxygen pump current IP of the wide range air-fuel ratio sensor 8
supply is started and the exhaust air fuel ratio is detected.

air-fuel ratio feedback control is started.

Further, when it is determined in step 117 that T, □>0, step 11B is bypassed and the process returns.

On the other hand, if the pump drive start signal Sc has already been output in step 115, this process ends without going through steps 116 to 118.

In this way, at the time of starting, the output start timing T and T are first set based on the cooling water temperature, and then the time when the wide range air-fuel ratio sensor 8 will be activated to a state where the air-fuel ratio can be detected is predicted based on the engine operating condition after starting. Supply of the oxygen pump current I2 is started, air-fuel ratio feedback IIIJ control is started, and the air-fuel ratio is controlled to a desired value.

[Problem that the invention seeks to solve]

Conventional air-fuel ratio control devices for internal combustion engines are configured as described above, and are based only on the engine start completion time, so the oxygen pump current is adjusted to suit various starting conditions when the outside temperature is low or high. ! It has been difficult to properly control when the water begins to flow.

In addition, even when the output V of the oxygen battery cell, which is the standard when detecting the exhaust gas air-fuel ratio from the oxygen pump current IP, does not show a normal value under the conditions shown below, the oxygen pump current is applied in a fixed procedure. In order to determine when to start, the air-fuel ratio cannot be accurately detected and the air-fuel ratio feedback control may cause the engine to stall due to over-rich conditions, or the wide-range air-fuel ratio sensor 8 may be damaged due to excessive flow of oxygen pump current IP. Ta.

Such a six-value abnormality occurs in the diffusion chamber of the wide-range air-fuel ratio sensor 8 when starting at a low temperature of -10 to -30°C, when the amount of fuel discharged from the injector 6 becomes excessively large, or when the engine suddenly accelerates or decelerates. A high concentration of unburned gas enters the oxygen pump cell 81 near the atmosphere-side electrode 83c.
This occurs when the exhaust side and the atmosphere side electrode are covered with the same unburned gas, the oxygen concentration decreases and the V6 output decreases.

Furthermore, it was not possible to stop the oxygen pump current 1p unless the engine stopped, and it was not possible to control the oxygen pump current in response to abnormalities during engine operation.

Therefore, with conventional air-fuel ratio control devices for internal combustion engines that start flowing oxygen pump current without detecting the oxygen pump cell output in the program, it is difficult to accurately control the oxygen pump current, and the accuracy of air-fuel ratio detection decreases. There was a problem in that the fuel ratio could not be precisely controlled through feedback, resulting in poor driving performance.

This invention has been made to solve these problems, and is designed to provide an oxygen pump that is optimal not only for starting at extremely low temperatures, but also even when a sensor abnormality occurs after the oxygen pump current has started flowing once the starting has been completed. An object of the present invention is to provide an air-fuel ratio control device for an internal combustion engine that can perform current drive prohibition and start control, constantly detect accurate air-fuel ratios, and realize inexpensive air-fuel ratio feedback control.

[Means for solving problems]

The air-fuel ratio f! of the internal combustion engine according to this invention! 1l Jil! The device includes an oxygen battery cell electromotive force detection circuit that detects the electromotive force of the oxygen battery cell of the wide range air-fuel ratio sensor, and an oxygen battery cell electromotive force detection circuit that detects the electromotive force of the oxygen pump cell based on the value of the electromotive force detected by the oxygen battery cell electromotive force detection circuit. A control device for controlling the pump current is provided.

[For production]

In this invention, the electromotive force of the oxygen battery cell is detected by the oxygen battery cell electromotive force detection circuit when the engine is started, and the timing at which the oxygen pump current starts to flow is controlled according to the detected value of the output voltage V of the oxygen battery cell. Determined by the device, even during engine operation, if the output voltage V value of the oxygen battery cell is below a predetermined value, the wide range air-fuel ratio sensor is determined to be abnormal, the oxygen pump current is stopped, and the output of the oxygen battery cell is restarted. The oxygen pump current is controlled to be stopped until the voltage V exceeds a predetermined value.

〔Example〕

Embodiments of the air-fuel ratio control device for an internal combustion engine according to the present invention will be described below with reference to the drawings. The configuration of the present invention is completely the same as the configuration of the conventional device shown in FIG. 7, except for the oxygen battery cell electromotive force detection circuit that detects the electromotive force of the oxygen battery cell of the wide range air-fuel ratio sensor 8. The arithmetic processing mainly performed by the four microphone processors 93 and the data setting method are different from the conventional method.

FIG. 1 shows the configuration of an embodiment of the present invention, and FIG. 2 shows the configuration of a wide range air-fuel ratio sensor 8 of the present invention. Second
In the figure, in addition to the configuration of the conventional wide-range air-fuel ratio sensor 8, an oxygen battery cell electromotive force detection circuit 82a for detecting the output voltage V of the oxygen battery cell is added, and this output signal v5 is controlled by the control shown in FIG. The signal is input to the AD converter 91 of the device 9, and the microprocessor 93 controls whether or not to start flowing the oxygen pump current in the pump current drive output circuit 97. Other configurations are the same as before.

Next, the operation will be explained. FIG. 4 is a flowchart showing the control procedure of an embodiment of the present invention. °this fourth
In the figure, steps 101 to 103 are step 20 of the flowchart of FIG. 9 showing the conventional control procedure.
Since it is the same as 1 to 203, the explanation will be omitted.

If it is determined in step 101 that the rotational speed N) is 400 rpm, the process proceeds to step 105, and the control circuit drive signal S
The presence or absence of the output of the heater body narrow circuit drive signal S is determined.
If h is output, the process proceeds to step 107, and if the heater control circuit drive signal Sh is not output, the process proceeds to step 1.
The process proceeds to step 06, where output of the heater control circuit drive signal Sh is started, and the process proceeds to step 107.

In step 107, the output signal v6 of the oxygen battery cell electromotive force detection circuit 82m that detects the output voltage V of the oxygen battery cell 82 of the wide range air-fuel ratio sensor 8 is read, and in step 10
8, the output voltage v3 of the oxygen battery cell electromotive force detection circuit 82a
is a predetermined value V. (for example, 0.3V) or higher, and determine whether the voltage is greater than or equal to 0.3V. In this case, it is determined that the oxygen battery cell 82 is activated and normal, and the process proceeds to step 109.

Also, in step 108, V,<V,. If it is determined that the wide range air-fuel ratio sensor 8 is inactive or abnormal, the process proceeds to step 103, and the output of the pump drive start signal S0 is stopped (if it has already been stopped, it is maintained stopped). Proceeding to step 104, the output start timing times T and T of the pump drive start signal S0, which will be explained in detail later, are reset to zero, and the process returns.

This operation completes engine starting, and the pump drive start signal S is generated by the procedure described below. Even after the output of Destruction of the wide-range air-fuel ratio sensor 8 due to excessive pump current flow and excessive fuel injection amount feedback control based on an abnormal output value of the wide-range air-fuel ratio sensor 8 can be prevented.

On the other hand, if the process proceeds to step 109, the oxygen battery cell 82
Considering that has been activated normally, the output signal V, of the oxygen battery cell electromotive force detection circuit 82a is a predetermined value v,. In order to start flowing the oxygen pump current lp after a predetermined output start timing time T8T from the above timing t0, this output start timing time T8. It is determined whether T, 7\O has already been set (that is, T, 7\O), and if T, □-〇, the cooling water temperature - is read in step 110, and then step 11
1, the output start timing time TST is looked up in a table based on the value of the cooling water temperature hole, and the process proceeds to step 112.

Also, in step 109, the output start timing time T, □
If it is determined that is not zero, steps 110 and 111 are skipped and the process proceeds to step 112 so that the output start timing times T and T, which have been set by − degrees, are not erroneously set again.

In step 112, the engine speed N and fuel injection amount are read, and the process proceeds to step 113, where subtraction processing is performed from the output start timing time TS□, and the time Tau which determines the output start timing of the pump drive start signal S0 is determined by this rotation. After looking up the table based on the number N and the fuel injection amount Tp,
This process ends.

However, since the method for setting the output start timing time T9□ is different from the conventional one, it goes without saying that the value previously recorded in the ROM for performing the table lookup of the above-mentioned time Taub is different from the conventional value.

Next, after the above-mentioned processing is completed, the pump drive start signal S is generated based on steps 115 to 118 of the flowchart of FIG. Controls the start of output. This process is completely the same as the conventional process, so the explanation will be omitted.

The above processing is significantly different from the conventional example, and although the effective heater capacity changes depending on the external conditions of the engine (for example, outside temperature) and the activation timing of the wide range air-fuel ratio sensor 8 varies, the conventional example drives the pump. Compared to the standard for the output start timing of the start signal S0, which is the time when the heater is turned on (that is, the time when the heater control circuit drive signal Sh is output), in this invention, the wide range air-fuel ratio sensor 8 itself reaches the activation temperature by the heater, and the oxygen battery The point in time when the output voltage V of the cell 82 starts to output a normal value is used as a reference for starting to output the heater control circuit drive signal Sc.

In addition, in the conventional example, the heater control circuit drive signal S is used only at the time of starting.
. In contrast, in the present invention, by constantly detecting the heater control circuit drive signal V, an abnormality in the output voltage of the oxygen battery cell can be detected to prevent damage to the wide range air-fuel ratio sensor 8 and excessive Erroneous fuel feedback control can be avoided.

FIG. 5 shows the timing t at which the pump current begins to flow during the horizontal start operation of the present invention, and the output signal v6 detected by the oxygen battery cell electromotive force detection circuit 82a, and the output voltage of the oxygen battery cell 82.
is above the predetermined value V, .
The relationship between the start of output and the timing time T is shown.

The output start timing time T, □ is sequentially subtracted by time 'r, , b by the procedure shown in Fig. 10, and when it becomes less than zero, that is, at the time t when the oxygen pump current is turned on, the oxygen pump current ■2 becomes It starts to flow.

In addition, Fig. 6(b) shows that when the oxygen pump current is already flowing and the exhaust air fuel ratio is being measured as shown in Fig. 6(a), a high concentration is detected as shown in Fig. 6(b). When unburned fuel gas enters the wide range air-fuel ratio sensor and the output signal V, which is the output voltage of the oxygen battery cell output 82 detected by the oxygen battery cell electromotive force detection circuit 82a, deviates from the normal value, this output Signal v8 is detected and the oxygen pump current is stopped according to the procedure shown in Fig. 4, and then the high concentration gas disappears and the output signal becomes equal to or higher than the predetermined value v8° again, and the oxygen pump current flows and measurement of the exhaust air fuel ratio is started. An example is shown below.

In the above embodiment, a speed density type fuel injection device is used as a specific example of the fuel injection system, but it goes without saying that the present invention can also be applied to a fuel injection device using an air flow sensor or an electronically controlled vaporizer.

〔Effect of the invention〕

As explained above, this invention detects the oxygen battery cell output voltage of the wide-range air-fuel ratio sensor using the oxygen battery electromotive force detection circuit, determines the activation state of the wide-range air-fuel ratio sensor based on this output signal, and determines the oxygen pump current. Since the flow is controlled to flow, highly accurate activation judgment and oxygen pump current control are possible, and oxygen pump current output can be stopped and started not only during side start operation but also during operation and while measuring the exhaust air-fuel ratio. This has the effect of improving the air-fuel ratio measurement accuracy of the wide-range air-fuel ratio sensor, increasing reliability, enabling stable air-fuel ratio feedback fuel control, and improving driving feeling.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of an air-fuel ratio control device for an internal combustion engine according to the present invention, FIG. 2 is a block diagram of a wide-range air-fuel ratio sensor in the same embodiment, and FIG. Characteristic diagram of wide range air-fuel ratio sensor in air-fuel ratio control device,
FIG. 4 is a flowchart showing the operation of the control device in the above embodiment, FIG. 5 is an operation explanatory diagram for explaining the control method in the above embodiment, and FIG. 6(a) is a flow chart for explaining the control method in the above embodiment. FIG. 6(b) is an explanatory diagram showing the relationship between time and oxygen pump current. FIG. 6(b) is an explanatory diagram showing the relationship between the oxygen pump current in FIG. Figure 8 is a configuration diagram of a conventional air-fuel ratio control device for an internal combustion engine, Figure 8 is a configuration diagram of a wide range air-fuel ratio sensor in a conventional air-fuel ratio control device for an internal combustion engine, and Figure 9 is a configuration diagram of a conventional air-fuel ratio control device for an internal combustion engine. Flowchart showing the operation of
FIG. 0 is a flowchart showing the operation of an embodiment of the present invention and a conventional air-fuel ratio control device for an internal combustion engine. 1... Internal combustion engine, 2... Intake pipe, 3... Throttle valve,
4... Pressure sensor, 5... Rotation sensor, 6... Injector, 7... Exhaust pipe, 8... Wide range air-fuel ratio sensor, 9... Control device, 10... Cooling water temperature sensor , 8
1... Oxygen pump sensor, 82... Oxygen battery cell,
82 a-oxygen battery cell electromotive force detection circuit, 84... diffusion chamber, 85... reference voltage source, 86... comparison amplifier,
96... Injector drive output circuit, 97... Pump current drive output circuit, 98... Heater control drive output circuit. In the drawings, the same reference numerals indicate the same or equivalent parts.

Claims (2)

[Claims] (1) A gap section into which the exhaust gas of the internal combustion engine is introduced, a solid electrolyte oxygen pump cell that controls the oxygen partial pressure in this gap section, and an electromotive force that generates an electromotive force corresponding to the oxygen partial pressure in the gap section and the oxygen partial pressure in the atmosphere. a wide range air-fuel ratio sensor including a solid electrolyte oxygen battery cell to heat the solid electrolyte oxygen battery cell and a heater to heat the solid electrolyte oxygen pump cell; a pump current supply means for supplying a pump current; a heater power supply means for supplying power to the heater so that the temperature of the solid electrolyte oxygen pump cell becomes a predetermined value; and detecting an electromotive force of the solid electrolyte oxygen battery cell. an oxygen battery cell electromotive force detection means; an oxygen pump current detection means for detecting the oxygen pump current; an operating state detection means for detecting the operating state of the internal combustion engine; Air-fuel ratio control for an internal combustion engine, comprising: a control device that supplies power and outputs the start signal after a predetermined time depending on the operating state at startup when the electromotive force of the solid electrolyte oxygen battery cell exceeds a predetermined value. Device. (2) After the starting of the engine is completed and the oxygen pump current flows, if the electromotive force of the solid electrolyte oxygen battery cell is less than a predetermined value, the control device stops the oxygen pump current and 2. The air-fuel ratio control device for an internal combustion engine according to claim 1, wherein control is performed to maintain the pump current stopped state until the electromotive force of the battery cell exceeds a predetermined value.