JPH04116249A - Control device for internal combustion engine - Google Patents

Abstract

PURPOSE:To invariably maintain correct fuel control by indicating the detection delay of a hot-wire type air flow sensor with a transfer function, correcting it by reverse compensation, and determining the control parameter used for correction from the operation state of an internal combustion engine. CONSTITUTION:High-frequency noises are removed from the flow measured value Qa of a hot-wire type air flow sensor 11 by a hard filter 71, the response delay indicated by a transfer function is reverse-compensated by a processing block 72, and the value converted into technological value Qs is outputted. The difference between the previous cylinder intake air quantity Qc and the present cylinder intake air quantity Qs in the periodically performed processing is multiplied by the gas constant to estimate the intake pipe inner negative pressure P by a processing block 73. The cylinder intake air quantity Qc is calculated from the estimated intake pipe inner negative pressure P and the engine rotating speed N via map retrieval by a processing block 74. Time constants T1, T2, T3 of the response delay indicated by the transfer function are calculated from the cylinder intake air quantity Qc by a processing block 75, and they are used for the processing by the processing block 72.

Description

[Detailed Description of the Invention] 1. Field of Industrial Application] The present invention relates to an internal combustion engine control device that measures the intake flow rate using a hot-wire air flow meter and controls the fuel supply amount, and is particularly applicable to automobiles. The present invention relates to an internal combustion engine control device suitable for gasoline engines.

[Prior art] In recent years, control devices that measure the intake air flow rate and control the fuel supply amount have been widely adopted in automobile gasoline engines.One type of air flow meter used at this time is the hot wire type. There is an air flow sensor.

By the way, this hot wire type air flow sensor is known to exhibit a unique detection delay characteristic, and for this reason,
9-176450 discloses the following method. In other words, the detection delay is treated separately into the heat capacity system of the hot wire that forms the sensor body, and the heat transfer delay system due to the heat capacity of the support for this hot wire, and the reduction amount Gs is used to correct the delay.
is introduced as a state variable, and the following equation is derived and corrected.

Gout=a-Gin 1b-Gs-Gsz (1-a) Gin-b-Gst Actually, these equations are subtracted and the control device calculates them as follows.

Gin(i)-1/a[Gout(i)-b-Gs(
i −1)]Gs(i) = (1-a)Gi(i)+(
1-b) Gs(i-1) The coefficients a and b are determined using Gin(i-1).

[Problems to be Solved by the Invention] The above-mentioned conventional technology does not give sufficient consideration to the determination of control parameters, and because the control parameters are determined from the detection results of the air flow sensor, the engine operating state may be transient. When the system is in this state, there is a risk of malfunction, and there are problems with accuracy.

An object of the present invention is to provide an internal combustion engine control device that allows easy setting of control parameters, always calculates the intake flow rate with high accuracy, and allows accurate control of fuel supply amount at all times, including in transient conditions. There is.

[Means for Solving the Problems] In order to achieve the above object, the detection delay of the hot wire air flow sensor is expressed by a transfer function, and correction is performed by inverse compensation of the detection delay, and the control parameters used for this correction are is determined from the operating state of the internal combustion engine.

[Operation] The inverse compensation method by canceling the poles and zero points of the transfer function requires less load on the microcomputer used for control than the internal state variable introduction method. Further, correction using the inverse compensation method is not affected by intake pulsation and the like when the internal combustion engine is under high load, so high accuracy can be easily maintained. Furthermore, control parameters can be easily measured by testing a single hot-wire air flow meter, so if the measurement results are selected and changed according to the operating condition of the internal combustion engine, they can be fed back to the correction process. , the operation is stabilized and the accuracy is further improved.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS An internal combustion engine control device according to the present invention will be explained in detail below using illustrated embodiments.

FIG. 7 shows an example of a fuel control system for an internal combustion engine to which an embodiment of the present invention is applied.
1 is a control circuit including a microcomputer, 11 is a hot wire intake flow rate sensor, and 12 is a fuel injection valve (injector).
It is.

The control circuit 1o receives the flow rate detection value Q-a from the hot wire type air flow sensor 11 and the detection value N from the rotation speed sensor.
Detected values from various sensors (not shown), such as It functions to supply fuel to the fuel injection valve 12. However, at this time, since the hot wire air flow sensor 11 has a response delay as described above, the flow rate detection value Qa is used as it is and the control signal I
Calculating NJ does not provide sufficient accuracy as described above.

Therefore, in this embodiment, the procedure is as follows.

FIG. 2 shows the internal circuit blocks of the control circuit 10, including a CPU 20 that performs arithmetic processing, and a ROM that is a nonvolatile memory that stores programs and various constant data.
21, RAM 22 which is a volatile memory for storing data during calculations, 11023 which is an interface for inputting and outputting signals with the outside, and a driver 24 necessary for driving fuel injection valves etc. It is composed of the following, and thereby performs arithmetic processing as described below.

First, FIG. 3 shows the transient response characteristics of the hot wire type air flow sensor 11, with the elapsed time t on the horizontal axis and the air flow rate Q on the vertical axis, as shown by the thick solid line 31. A thin solid line 32 indicates a change in the flow rate measurement value (flow rate detection value) Qa obtained from the sensor when the air flow rate Q is changed in a stepwise manner.

Based on this characteristic, the response delay of the sensor can be expressed using the symbols in the figure as shown in the following equation.

Qs=(1-Ae Ding・-Be T・
) Q If this is expressed as a transfer function, it becomes as follows.

1+ST.

Qs(S)= (1+ST,)(1+ST,) Q(
””” ■Here, T, = BT, +AT.

Note that in FIG. 3, portions (A) and (B) show the portions determined from the characteristic 32 by the tangential method.

Next, Fig. 4, Fig. 5, and Fig. 6 show the characteristics of these constants with respect to step-like changes in the intake flow rate. Fig. 4 shows the time constant T1, and Fig. 5 shows the time constant T1. The constant T,
Moreover, FIG. 6 represents the ratio of constants A and B, respectively.

FIG. 1 is a control block diagram showing the arithmetic processing performed by the control circuit 10. Hereinafter, the operation of this embodiment will be controlled using this control block diagram.

The flow rate measurement value supplied from the hot wire air flow sensor 11 (
The flow rate detection value) Qa is input to a hard filter 71, where high frequency noise is removed, and then input to a block 72, where it is processed by the above-mentioned equation 0, and the pole and zero point of this equation 0 are canceled out. , is inversely compensated, and is thereby output as a value Qs that has been subjected to engineering value conversion based on the flow rate-voltage characteristic (Q-V characteristic) of the hot-wire type air flow sensor 11, and is input to the processing block 73.

In processing block 73, the difference between the cylinder-wise inflow air JIQc at the previous time of the periodically executed process and the current cylinder-wise inflow air amount Qs is multiplied by a gas constant to estimate the intake pipe negative pressure P. Do this.

The difference formula in this case is as follows.

p -p 10- to 52 eup 2 nee (Qt-Qc) --
■11V during i Here, Δt: calculation period T: intake air temperature R: gas constant
(2): The intake pipe volume processing block 74 calculates the cylinder-wise inflow air flow rate Qc from the intake pipe internal negative pressure P estimated as described above in the processing block 73 and the engine rotational speed N by map search.

The processing block 75 calculates the above-mentioned time constants T1, T1, T from the inflow air flow rate Qc for each cylinder, and uses them in the processing at the processing block 72. Here, the time constants T3, T1, and T from the cylinder-like inflow air flow rate Qc in the processing block 75 can be calculated by searching a table using the data Qc, or simply by using a three-stage switching method (previously calculated) as shown in the figure. A method may be used in which a plurality of types, for example, three types of time constants are prepared according to the value of Qc, and then a selection is made according to Qc.

The cylinder inflow air flow rate Qc calculated in this way has sufficiently compensated for the response delay of the flow rate measurement value (flow rate detection value) Qa supplied from the hot-wire air flow sensor 11, so it is used. By calculating the optimum amount of fuel for the internal combustion engine and supplying the control signal INJ necessary for giving this amount of fuel to the fuel injection valve 12, accurate fuel control can be easily obtained.

Next, the operation of the microcomputer in the control circuit lo necessary to obtain the operation according to the control block of FIG. 1 will be explained with reference to the flowchart of FIG.

The process shown in FIG. 8 is started by a time interrupt of 4 m5 ec and is executed periodically. First, in step 801, time constants T1, T1, T, Perform the process to find .

In step 802, the inverse compensation based on the above equation 0 is performed using a digital calculation difference equation.

The difference formula at this time is as follows.

Qs(n)=a,・Q(n) −a −Q(n−1
) 10a, ・Q(n-2)+b,-Qs(n-1)2 where Δt=calculation cycle In step 803, the flow rate-voltage characteristic of the hot wire air flow sensor 11 is used to calculate from the output voltage. Convert to flow rate.

In step 804, the negative pressure in the intake pipe is estimated from the difference between the current flow rate (air flow rate passing through the throttle valve) and the previous cylinder-wise inflow air amount. The difference formula used at this time is the above-described 0 formula.

In step 805, the engine rotational speed N is read,
The current inflow air amount for each cylinder is searched using a two-dimensional map of intake pipe negative pressure and rotational speed. In addition, for the search at this time,
Needless to say, surface interpolation or the like may be applied to improve accuracy.

FIG. 9 shows the inflow air flow rate Qc in the cylinder at step 801.
An example of a table used to obtain the time constants T1 and T from the following figure is shown below.

As mentioned above, this embodiment has a three-stage switching system, and when the value of the inflow air flow rate Qc into the cylinder is QCL and QCH, the time constants are switched to the respective time constants, and the three stages are eventually selected. become. At this time, as shown in the figure, hysteresis is provided depending on the direction of change in flow rate, thereby ensuring stable operation.

FIG. 10 shows the detailed logic of the routine that calculates the time constants T1, T8, and T. First, in step 1001, it is determined whether the current state was in the region of QC>QCH. , when the result is affirmative, QHYS is added to Qc in step 1002, and in step 1003 it is determined that Qc<QCH7.

Here, QHYS becomes hysteresis in the direction in which Qc decreases.

Hereinafter, steps 1004 to 1009 are also similar, and the time constant can be changed according to Qc, resulting in three stages.
The value of is determined depending on the internal combustion engine to which it is applied, the range in which it is frequently used, and the characteristics shown in FIGS. 4, 5, and 6.

Therefore, according to one or more embodiments, the inflow air flow rate into the cylinder can be calculated with the response delay of the hot-wire air flow sensor sufficiently corrected, so it can be applied to automobile gasoline engines, etc. to precisely control the air-fuel ratio. This makes it possible to maintain engine performance and meet exhaust gas regulations.

[Effects of the Invention] As described above, according to the present invention, the response delay of the hot-wire air flow sensor can be sufficiently compensated for, so that the internal combustion engine can always be accurately operated regardless of whether the operating state is steady or transient. fuel control can be easily maintained.

Furthermore, in the present invention, the parameters used for the control are:
Since it can be easily determined by testing a single hot-wire air flow sensor, a low-cost, high-precision fuel control system can be easily provided.

Further, according to the present invention, it is possible to avoid being affected by the intake pulsation of the engine, so that sufficiently stable operation is possible.

Further, since the control parameters are changed according to the operating state, sufficiently stable and highly accurate control can be obtained in this respect as well.

[Brief explanation of drawings]

FIG. 1 is a control block diagram of an embodiment of the internal combustion engine control device according to the present invention, FIG. 2 is a circuit block diagram showing an embodiment of the control circuit of the present invention, FIGS. 3, 4, and 5. , FIG. 6 is a characteristic diagram for explaining the operation, FIG. 7 is a configuration diagram showing an example of a fuel control system for an internal combustion engine to which the present invention is applied, and FIG. 8 is an overall diagram of an embodiment of the present invention. FIG. 9 is an explanatory diagram of a control parameter switching table, and FIG. 10 is a flowchart explaining the control parameter switching operation. 10...Control circuit, 11...Hot wire type air flow sensor, 12...Fuel injection valve, 71-7
5... Control block. Fig. 2 I 77-75: IVHJ PD tsuku Fig. 3 t (j・C) Fig. 4 t (s@c) 0 (K9//'l) Fig. 15 Fig. 6 Q (KQ/h) Figure 8 Figure 9 CL CH 0 (Kg/h) Figure 7 O Figure 10

Claims (1)

[Scope of Claims] 1. In an internal combustion engine control device of a type that controls the fuel supply amount based on the measurement result of the intake air flow rate using a hot-wire air flow meter, the delay in the measurement result of the intake air flow rate is corrected to adjust the actual intake air flow rate. A control logic that outputs an estimated value of the flow rate and a control parameter selection means that changes a control parameter used in the control logic according to the operating state of the internal combustion engine are provided, and the control logic outputs the estimated value of the actual intake flow rate. An internal combustion engine control device characterized by being configured so that the supply amount is controlled. 2. The invention according to claim 1, characterized in that the control logic is constituted by means for expressing the delay in the measurement result of the intake flow rate by a transfer function, and inversely compensating for this by a difference method using a digital filter. Internal combustion engine control device. 3. In the invention of claim 1, the control parameter is
An internal combustion engine control device characterized in that the internal combustion engine control device is configured to perform calculation by table search or multi-stage switching based on the set value of the transient response characteristic of the hot wire air flow meter and the estimated value of the actual intake air flow rate. 4. In the invention of claim 2, means is provided for determining whether the operating state of the internal combustion engine is in a steady state or in a transient state, and when the operating state is in a steady state, the gain of the control parameter and the sensitivity of the digital filter are determined. An internal combustion engine control device configured to reduce at least one side.