JPH01219329A - Control device for internal combustion engine - Google Patents

Abstract

PURPOSE:To carry out a high accuracy control, by controlling an engine based on an output of an oxygen senser after it is judged that the output of an oxygen senser is larger than reference values to be generated under a full pressure of intake air at a prescribed value corresponding to an oxygen partial pressure with the oxygen senser activated, by controlling an engine by the output after that. CONSTITUTION:An oxygen senser 70 is provided in the intake air system of an internal combustion engine. And a signal which is correspond to an oxygen partial pressure in intake air, and affected by full pressure of the intake air, is outputted from the oxygen senser 70 for detecting. A new air amount introduced to an engine, a fuel injection amount in a control means B and a ignition timing are calculated. Provided that it is judged by a judging means A that, during the engine is in idle operation, the value of the output signal of the oxygen senser 70 is larger than reference values to be generated under the full pressure of a prescribed value corresponding to an oxygen partial pressure with the oxygen senser activated, the control means B controls the internal combustion engine by using the output signal of the oxygen senser 70 after that. Therefore, the engine control is carried out based on an accurate oxygen weight in intake air.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a device for controlling fuel injection control, ignition timing control, etc. in an internal combustion engine.

[Conventional technology]

Fuel injection control JR is performed, for example, to set the air-fuel ratio of the air-fuel mixture to a predetermined value, and for this control, the weight of oxygen introduced into the cylinder bore must be accurately determined. In Japanese Patent Application No. 62-24824, the present applicant installed an oxygen sensor in the surge tank of the intake system to detect the oxygen partial pressure in the intake system, and determined the oxygen weight in fresh air from the oxygen partial pressure to control the engine. We proposed a configuration to do this. As shown in FIG. 2, for example, the output value of this oxygen sensor is affected by the pressure in the surge tank, and increases as the pressure increases.

In other words, even if the oxygen concentration is the same, the oxygen partial pressure increases as the internal pressure of the surge tank increases.
The sensor output changes if the pressure inside the surge tank changes. In addition, when the oxygen sensor element temperature is low, this sensor output value does not become very large (even if the pressure becomes high), but when the oxygen sensor is activated and the element temperature rises, it becomes large (the sensor output value becomes large). If the oxygen sensor is not activated, accurate oxygen weight cannot be obtained, and therefore a means for determining activation of the oxygen sensor is required.

[Problem to be solved by the invention]

However, in the past, the activity of the oxygen sensor in the intake system has not been accurately determined, and since the total pressure of the intake system is not taken into account, errors tend to occur when determining the activity. Therefore, precise engine control using oxygen weight is not sufficient. There was a fear that it would not be possible to maintain good drivability and exhaust gas emissions.

An object of the present invention is to determine activation of an oxygen sensor regardless of the magnitude of the total pressure of the intake system, obtain accurate oxygen weight, and perform highly accurate engine control.

[Means to solve the problem]

As shown in the configuration diagram of the invention in FIG. 1, the control device for an internal combustion engine according to the present invention is provided in the intake system of the internal combustion engine, outputs a signal according to the partial pressure of oxygen in intake air, and outputs a signal according to the partial pressure of oxygen in intake air. The oxygen sensor 70 is affected by the total pressure of intake air, and the oxygen sensor 70 is affected by the total pressure of the intake air.
means A for determining whether the value of the output signal is greater than a reference value that should be generated under the predetermined total pressure if the oxygen sensor is activated; The present invention is characterized by comprising means B for controlling the engine using the output signal of the oxygen sensor after the determination.

〔Example〕

The present invention will be explained below based on illustrated embodiments.

In FIG. 3, 10 is a cylinder block, 12 is a piston, 14 is a connecting rod, 16 is a cylinder head, 18 is a combustion chamber, 20 is a spark plug, 22 is an intake valve, 2
4 is an intake boat, 26 is an exhaust valve, 28 is an exhaust boat, 2
9 is a distributor, and 30 is an ignition device (consisting of an igniter 30a and an ignition coil 30b). The intake port 24 is connected to the air cleaner 40 via an intake pipe 31, a surge tank 32, a throttle valve 34, and an intake pipe 36. The surge tank 32 is provided with a pressure sensor 76 that detects the intake pressure (total pressure of intake air) downstream of the throttle valve 34 . Note that this pressure sensor 76 is not necessarily necessary, and can be omitted if the activity of the oxygen sensor 70 is determined without using the pressure sensor output. A fuel injector 42 is arranged in the intake pipe 31 close to the intake port 24. Exhaust boat 28 is connected to exhaust manifold 44 .

An exhaust gas recirculation passage (HGR passage) 45 is provided to connect the exhaust manifold 44 and the surge tank 32. An exhaust gas recirculation control valve (fiGR valve) 46 is provided on the EGR passage 45 to control the exhaust gas recirculation rate (frGR rate). In this embodiment, the EGR valve 46 includes a negative pressure actuated diaphragm mechanism 47. Diaphragm mechanism 47
A pressure regulating valve 49 connected to an EGR port 48 bored slightly upstream of the idle position of the throttle valve 34 is connected to a constant pressure throttle 51 in the EGR passage 45 via a pressure conduit 50.
It is connected to a constant pressure chamber 52 formed downstream of. Therefore, the pressure regulating valve 49 is operated from the EGR boat 48 to the negative pressure operating mechanism 4 of the EGR valve 46 so that the pressure in the constant pressure chamber 52 is approximately constant.
Control the negative pressure introduced into 7. The diaphragm 49a of the pressure regulating valve 49 is connected to the negative pressure boat 53 slightly upstream of the EGR boat 48, and the negative pressure corresponding to the load acts on the diaphragm 49a to oppose the exhaust pressure, and the HGR rate is adjusted according to the load. control. Since the configuration and operation of this EGR device are well known, no further explanation will be provided.

The control circuit 54 is configured as a microcomputer system and performs fuel injection control, ignition timing control, and other engine operation controls.

The control circuit 54 is a micro processing unit) (
MPU) 54a, memory 54b, and input port 54c
, an output coupler 54d, and a bus 54e connecting these elements. The input port 54c is connected to each sensor and receives engine operating condition signals.

Crank angle sensors 56 and 5B are installed on the distributor 29. The first crank angle sensor 56 is
It is installed opposite the magnetite piece 60 on the distributor shaft 29a, and generates a pulse signal every 720° rotation of the crankshaft, that is, every cycle of the engine, and this serves as a reference signal. The second crank angle sensor 58 is installed opposite the magnet piece 62 on the distributor shaft 29a, and generates a signal every 30 degrees of the crankshaft, which is used as a trigger signal for fuel injection control and ignition timing control. Become. The water temperature sensor 64 is the cooling water jacket 1 of the cylinder block IO.
Detects the cooling water temperature within 0a. Exhaust side oxygen sensor 68
is provided in the exhaust manifold 44. This exhaust side oxygen sensor 68 is for air-fuel ratio feedback control, and is a 0□ sensor in a system that controls the air-fuel ratio to the stoichiometric air-fuel ratio, and is a so-called lean sensor in a system that controls the air-fuel ratio to be leaner than the stoichiometric air-fuel ratio. Can be configured.

The surge tank 32 is provided with an intake side oxygen sensor 70. The intake side oxygen sensor 70 is used to output a signal according to the oxygen partial pressure in the intake air, detect the amount of fresh air introduced into the engine, and calculate the fuel injection amount and ignition timing. The output signal of this oxygen sensor 70 is transmitted to the surge tank 32.
As shown in FIG. 2, the higher the pressure, the higher the value becomes, and when the element temperature is low and the oxygen sensor 70 is not activated, it takes a smaller value than when it is activated. A throttle sensor 7 is attached to the shaft of the throttle valve 34.
2 is provided, and this throttle sensor 72 outputs a signal corresponding to the opening degree of the throttle valve 34. E.G.
The R valve 46 is provided with an EGR sensor 74, and the EGR sensor 74 outputs a signal corresponding to the opening and closing of the EGR valve 46. Further, a lever position sensor 76 provided in a transmission (not shown) outputs a signal indicating the position of the shift lever.

The MPU 54a executes calculations according to the program and data stored in the memory 54b, and sets a control signal to the output port 54d. The output port 54d is connected to the fuel injector 42, igniter 30a, and other control devices, and outputs control signals to these.

Hereinafter, fuel injection control in the operation of the control circuit 54 and determination of activation of the oxygen sensor 70 will be explained using a flowchart.

FIG. 4 shows a flowchart of the fuel injection routine, which is executed by detecting the crank angle before the fuel injection of the cylinder to which fuel is to be injected. For example, if fuel injection is to be performed during the intake stroke, it is performed by detecting 60 degrees before the intake top dead center. This detection is cleared by the arrival of the 720° CA signal from the first crank angle sensor 56 and the 30° CA signal from the second crank angle sensor 58.
``This can be determined by the value of a counter that is incremented each time a CA signal arrives.

In step 100, the throttle opening TA1, the engine speed N2, and the output value ■ of the oxygen sensor 70 are read.
In step 102, it is determined whether the activation flag f is 1 or not. For example, in the activity determination routine shown in FIG. 5, the activation flag f is set to 1 when the oxygen sensor 70 is activated, and set to 0 when the oxygen sensor 70 is not activated.

If the activation flag f is 1, the process proceeds to step 104, and the basic fuel injection time T is determined by referring to a map that uses the output value of the oxygen sensor 70 (weight of oxygen in the intake air) ■ and the engine speed N□ as parameters. demand. On the other hand, if the activation flag f is 0, the process proceeds to step 106, and the basic fuel injection time TP is determined by referring to a map using the throttle opening TA and the engine speed N as parameters. Step 10
4 or 106, the basic fuel injection time T is determined in step 108.
The actual fuel injection time TAU is calculated by multiplying P by a coefficient α and adding a coefficient β. Then, in step 11O, fuel injection is performed, and this routine ends.

FIG. 5 shows a flowchart of the activity determination routine, and this routine is executed at predetermined intervals (for example, every 5 m5ec). In step 200, for example, it is determined whether the engine has started from the output signal of the second crank angle sensor 58, and if the engine has not started, this routine is immediately terminated, but if the engine has started, step 200 is performed. Proceed to 202 and check whether exhaust gas recirculation is being performed or not.
In other words, it is determined whether the EGR valve 46 is open or not.

Opening/closing of the EGR valve 46 is obtained from the EGR sensor 74.

When the EGR valve 46 is open, the output value of the oxygen sensor 70 is affected by exhaust gas, so this routine is ended without executing steps 204 and below, and when the EGR valve 46 is closed, Proceeding to step 204, it is determined whether the oxygen sensor 70 is activated.

In step 204, the AD of the output signal of the oxygen sensor 70 is
The converted value is replaced with the output value I, and in step 206, the counter C is incremented by one. Counter C is 0 in advance
The counter C is cleared by 1 every time this step 206 is executed, that is, every predetermined opening time during which activation of the oxygen sensor 70 is determined (see FIG. 6).In step 208, the counter C is cleared. It is determined whether the maximum value Cvgax has been exceeded. This maximum value C5eax is determined in consideration of the frequency of idling operation, and corresponds to a time period in which the idling state occurs only once during engine operation.

In step 208, the counter C is still at the maximum value Cwa.
When it is determined that x has not been reached, the process proceeds to step 210, and it is determined whether the output value I of the oxygen sensor 70 is smaller than the minimum value I5hin. As shown in FIG. 6, the minimum value 1 sin is initially set to 0, so when step 210 is executed for the first time, the output value I is the minimum value 1
Since the value is larger than win, step 212 is skipped and this routine ends. Then if the minimum value 1 mtn
is set to a value larger than O, and if the output value I is smaller than this minimum value 15hin, step 21
2, the output value I at this time is replaced with the minimum value 1 sin.

In step 208, the counter C is set to the maximum value Craax.
When it is determined that the minimum value 1+*in is greater than or equal to the reference value Is, the counter C is cleared to 0 in step 214, and the process proceeds to step 216, where it is determined whether the minimum value 1+*in is greater than or equal to the reference value Is. The reference value Ig indicates that the oxygen sensor 70 has been activated. When this routine is executed and the process proceeds to step 216 for the first time, the minimum value I orin is 0 as described above, so it is smaller than the reference value Is, so the process proceeds to step 218 and the set value I is set to the minimum value 1eain.
Replace with As a result, the minimum value 1 sin suddenly increases as shown in FIG. Note that the set value IL is the output value I
The value is set to be larger than the possible range of values.

If the minimum value I sin is greater than or equal to the reference value Is in step 216, the oxygen sensor 70 is activated, so the activation flag f is set to 1 in step 220, and this routine ends. Note that the activation flag f is set to 0 in advance.

Only after executing this routine does the process proceed to step 218.
When the set value 1 is replaced with the minimum value 15 hin, the minimum value 1 tasn is updated to become smaller by executing steps 210 and 212, as shown in FIG. When this minimum value 1 sin exceeds the reference value Is, the activation flag f is set to 1 by executing steps 216 and 218.

Therefore, in this embodiment, it is assumed that idling operation will be performed at least once before the counter C reaches the maximum value Cmax, and the minimum value (w l giin) of the output value ■ of the oxygen sensor 70 during that time is This is the output value of the oxygen sensor 70 during idling operation, and this minimum value is the reference value Is.
If it is above, it is determined that the oxygen sensor 70 is activated. That is, there is no need to detect the pressure of the intake system to determine whether the oxygen sensor 70 is activated. Therefore, activation of the oxygen sensor 70 can be determined without providing a pressure sensor, and accurate oxygen weight can be determined.

FIG. 7 shows a flowchart of a second embodiment of the oxygen sensor 70 activity determination routine. In this second embodiment, the output value I of the oxygen sensor 70 during idling is set to a reference value Is.
The activity is determined by comparing the That is, in step 300, it is determined whether the shift lever is in the neutral position in the transmission system, and in step 302, it is determined whether the shift lever is in the neutral position.
Then, it is determined whether the throttle valve 34 is fully open or not.
In step 304, the engine speed Nt is 65 Orpm.
It is determined whether the value is between 750 rpm and 750 rpm. In these steps 300, 302, 304,
If any one of them is negative, this routine ends immediately, but these steps 300 and 302
, 304, it means that the engine is currently running at idle, and step 3
20, it is determined whether the oxygen sensor 70 is activated.

That is, in step 320, the output value I of the oxygen sensor 70
It is determined whether or not is greater than or equal to the reference value Is.

If the output value I is greater than or equal to the reference value Is, the oxygen sensor 70 is activated, and the activation flag f is set to 1 in step 322, and if the output value I is smaller than the reference value Is, the oxygen sensor 70 is activated. step 324
In this step, the activation flag f is set to 0, and this routine ends.

FIG. 8 shows a flowchart of a third embodiment of the activity determination routine. When it is determined that the engine is idling in steps 300, 302, and 304, step 310
whether or not exhaust gas recirculation is currently being performed.
That is, it is determined whether the HGR valve 46 is open or not. If the EGR valve 46 is not open, step 320
The activity of the oxygen sensor 70 is determined by executing the following.
If the GR valve 46 is open, this routine ends without determining the activity of the oxygen sensor 70. The reason for determining whether the EGR valve 46 is open or closed in this manner is to prevent inaccurate determination of the activity of the oxygen sensor 70 due to exhaust gas recirculation. Note that the other steps are the same as those in the flowchart of FIG. 7, and their explanation will be omitted.

FIG. 9 shows a flowchart of a fourth embodiment of the activity determination routine. If it is determined in steps 300, 302, and 304 that the engine is idling, step 312
It is determined whether the activation flag f is 0 or not. The oxygen sensor 70 has already been activated and the activation flag f is 1.
If set to , step 316 is executed, and the EGR passage 45 is opened by an on-off valve (not shown) to permit exhaust gas recirculation. In this case, there is no need to determine the activity of the oxygen sensor 70, so this routine ends as is. On the other hand, if the oxygen sensor 70 has not yet been activated and the activation flag f is set to 0, the on-off valve of the EGR passage 45 is closed in step 314, and exhaust gas recirculation is prohibited. Then, steps 320 and subsequent steps are executed to determine whether the oxygen sensor 70 is activated, and this routine ends. Thus, when determining activation of the oxygen sensor 70, erroneous determination of activation due to exhaust gas recirculation is prevented. The on-off valve is provided in the EGR passage 45, and is driven to open and close by selectively introducing negative pressure or atmospheric pressure, for example.

FIG. 10 shows a flowchart of a fifth embodiment of the activity determination routine executed at predetermined time intervals.

In this embodiment, when the intake pressure is within a predetermined value range, EGR
If the valve 46 remains closed for a predetermined period of time or longer, and the output value of the oxygen sensor 70 is equal to or higher than the reference value,
It is assumed that the oxygen sensor 70 is activated.

That is, in step 400, the total pressure P is read from the intake pressure (total pressure of intake air) sensor 76 shown in FIG.
02, whether or not this total pressure P is within a predetermined range, that is, ×±
It is determined whether it is within the range of 2Q+u+Hg. If it is within the predetermined range, the counter C0U is set in step 406 only if exhaust gas recirculation is not performed (step 404).
Increment NT by 1. In step 408, it is determined whether the counter COυNT has exceeded a predetermined value (Z), that is, whether the intake pressure has been within a predetermined range and exhaust gas recirculation has not been performed for a predetermined time or longer. , if this condition is satisfied, step 410
Proceed to. In step 410, the output value of the oxygen sensor 70 is determined to be greater than or equal to a reference value, which is the output that would be generated if the oxygen sensor was activated when the total pressure is within a predetermined range and there is no exhaust gas recirculation. Determine whether oxygen sensor 70
If the output value is equal to or higher than the reference value, it is determined that the oxygen sensor 70 is activated, and the activation flag f is set in step 412.
Let be 1. If the output life of the oxygen sensor 70 is smaller than the reference value, the oxygen sensor 70 is not activated, and the activation flag f is set to 0 in step 414.

On the other hand, if it is determined in steps 402 and 404 that the intake pressure is outside the predetermined range or that exhaust gas is being recirculated, the counter COυNT is cleared in step 416, and this routine ends.

Further, if the counter C0IJNT is less than the predetermined value (Z) in step 408, this routine is ended without performing any processing. According to this embodiment, the activity of the oxygen sensor can be accurately determined under a predetermined total pressure. As a sixth embodiment of the activation determination routine, the output (
A reference value) is stored in advance, and the reference value corresponding to the read total pressure P is compared with the oxygen sensor output.
It is also possible to determine the activity of 0, which is shown in FIG.

The oxygen sensor applied to the present invention has an output when the total pressure (intake pressure) is P and the intake oxygen partial pressure is POz (P/P
It has a structure that is not proportional only to O1), but is proportional to PO, (7) or P'-PO, , P'-PO1.

[Effects of the Invention] As described above, according to the present invention, even if the oxygen sensor changes depending on the magnitude of the total pressure of the intake system, activation of the oxygen sensor can be determined, and the weight of oxygen in the intake air can be accurately determined. This makes it possible to perform engine control as desired.

[Brief explanation of the drawing]

Fig. 1 is a configuration diagram of the present invention; Fig. 2 is a graph showing the relationship between intake system pressure and oxygen sensor output value; Fig. 3 is a sectional view of an internal combustion engine to which an embodiment of the present invention is applied; 5 is a flowchart of the fuel injection routine, FIG. 5 is a flowchart of the first embodiment of the activity determination routine, FIG. 6 is a graph showing time changes in the counter, sensor output value, and minimum value of the sensor output value, and FIG. Figure 8 is a flowchart of the second embodiment of the activity determination routine, Figure 8 is a flowchart of the third embodiment of the activity determination routine, Figure 9 is a flowchart of the fourth embodiment of the activity determination routine, and Figure 10 is the activity determination routine. FIG. 11 is a flowchart of the sixth embodiment of the activity determination routine. 54... Control circuit 70... Oxygen sensor

Claims (1)

[Claims] 1. An oxygen sensor installed in the intake system of an internal combustion engine, which outputs a signal according to the partial pressure of oxygen in the intake air, and whose signal is affected by the total pressure of the intake air, and the total pressure of the engine's intake air. means for determining whether or not the value of the output signal of the oxygen sensor while the oxygen sensor is being operated at a predetermined value is larger than a reference value that the oxygen sensor should output when activated under the predetermined total pressure; means for controlling the operation of the internal combustion engine,
A control device for an internal combustion engine, wherein the control means uses the output signal of the oxygen sensor for engine control after determining that the value of the output signal is larger than a reference value.