JPH04295155A - engine control device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine control device, and more particularly to a device that determines an optimum fuel amount based on a measured air flow rate and controls the air-fuel ratio (A/F) of an engine.

0002

[Prior Art] Conventionally, the amount of fuel injected from an injector is determined by measuring the flow rate of air flowing into the intake pipe of an engine.
Engine electronic control systems that calculate the fuel injection pulse width (fuel injection pulse width) have been widely put into practical use.

[0003] In the engine control device, various types of compensation are performed to calculate the amount of fuel in order to improve the accuracy of A/F control. For example, the technology disclosed in Japanese Patent Application Laid-Open No. 55-114609 takes into consideration that changes in the state of adhesion and evaporation of fuel injected from an injector on the intake pipe wall affect the air-fuel ratio, and compensates for this fuel adhesion. The amount of fuel required is calculated.

Compensation for the above fuel adhesion is particularly important during transient operation. FIG. 4 shows, as an example of transient operation, the relationship among throttle opening, basic fuel amount, compensation for fuel adhesion to the intake pipe wall, and A/F during acceleration operation. As shown in Figure 4, increased fuel injection is required during acceleration operation, but since the initial amount of fuel adhering increases during the acceleration stage, the basic fuel amount (fuel injection pulse width) alone is insufficient for A/F, as shown by the solid line. When the vehicle becomes lean and reaches the target speed, a portion of the attached fuel evaporates and the A/F becomes rich. Therefore, during and immediately after transient operation, the fuel injection control is
By compensating for the next advance and compensating for the first order lag, the A/F is maintained at the target value as shown by the broken line.

In the above conventional example, as a method of calculating the required fuel amount to maintain the target A/F, changes in the state of fuel adhesion in the intake pipe of the engine are calculated using an equilibrium adhesion method determined in relation to the engine load (intake pipe pressure). (the amount that is always attached to the intake pipe wall when the engine load is in equilibrium), the amount of adhesion at the current time, and the current fuel adhesion rate.
The fuel amount is determined by adding and subtracting this calculated value from the basic fuel amount. When viewed as a compensation filter, the equilibrium adhesion amount calculation is a first-order lag system of the basic fuel calculation, and the current adhesion amount calculation is a first-order advance system, and the required fuel amount is calculated by combining these two compensation filters. do.

In addition, recently, a technology has been proposed in which, when determining the amount of fuel, a compensation filter for the response delay of the air flow sensor and a compensation filter for the fuel transport delay in the engine intake system are connected in multiple stages to the intake pipe wall fuel adhesion compensation filter. has been done.

[0007]

[Problems to be Solved by the Invention] By the way, when such a multistage filter connection system is analyzed in the frequency domain, it is found that the intake pipe pulsation occurs in a certain region of the intake pipe pulsation frequency (for example, when the engine throttle is fully opened and the engine is operated at a high load close to that). There were areas where the gain was high in response to electrical noise (regions with high pulsation frequency) and electrical noise, and there were also operating regions where the control system lacked stability.

Furthermore, when it takes a relatively long time to transport fuel in the intake pipe, such as during idling, the calculation of transportation delay compensation exceeds the limit, and if this compensation filter is used as is, it will warp and interfere with control. Sometimes it caused

The present invention has been made in view of the above points, and its purpose is to improve the various problems that occur in the multistage filter connection system as described above, and to achieve high precision control and smooth control of the air-fuel ratio control system. An object of the present invention is to provide an engine control device that guarantees reliable operation.

0010

[Means for Solving the Problems] In order to achieve the above object, the present invention basically proposes the following means for solving the problems.

That is, in an engine control device equipped with means for measuring the intake air flow rate of the engine using an air flow sensor and calculating the optimum fuel amount for the engine based on this measured value, Various compensation filters are connected in multiple stages, and a means is provided for automatically changing the filter path by selecting filters to be used and filters to be omitted from among the various compensation filter groups according to the operating state of the engine.

0012

[Operation] With the above configuration, the route of the multistage filter can be changed by selecting whether to use or omit various compensation filter groups in relation to the engine operating state.

For example, when using various digital filters as various compensation filters, such as compensation for an air flow rate sensor, compensation for fuel transport delay in the intake system, compensation for fuel adhering to the wall of the intake pipe of the engine, etc., a throttle sensor, It is set to detect whether the engine is in transient or steady operation using an idle switch, etc., and to select whether to use or omit a filter in the compensation filter group based on the filter connection mode appropriate for each state.

To give a specific example, during transient operation of the engine, the target fuel amount is calculated by selecting all of the above-mentioned compensation filters, and during steady operation such as idling or high-load operation, the air flow rate sensor is selected. Various methods can be considered, such as selecting a compensation filter for the fuel transport delay and calculating the target fuel amount by omitting the filters for compensating for fuel transport delay and for compensating for fuel adhesion on the intake pipe wall.

By automatically setting filter selection and omission as described above, all compensations are satisfied during transient operation, and compensation for fuel adhesion on the intake pipe wall, which is a problem during transient operation, is also performed. On the other hand, during high load operation or idling operation, connected filter groups are selectively used or omitted, which does not match the control theory of the dynamic model. However, if the filter is designed to have a DC gain of 0 db, it will have no effect when the engine is in steady state.

[0016] By selectively using or omitting filters, it becomes possible to adjust the gain of the filter path. As a result, if a certain intake pipe pulsation frequency region has a high gain due to multi-stage filter connection (for example, intake pipe pulsation frequency during high-load operation), only the minimum necessary compensation filter is selected at this time. However, by omitting the rest, the gain can be lowered and the control system can be stabilized.

Furthermore, during idling operation, by omitting fuel transport delay compensation, which is considered to be ineffective at this time, smoother idling control can be achieved.

[0018] For transient determination, if an idle switch or throttle sensor that directly reflects the driver's intention is used, erroneous determination will not occur.

[0019]

[Embodiment] An embodiment of the present invention will be explained with reference to the drawings.

FIG. 1 is a block configuration diagram of various compensation filters in an engine control device according to an embodiment of the present invention, FIG. 2 is a hardware configuration diagram showing a part of the engine control system, and FIG. 3 is a block diagram of the above-mentioned engine control device. It is an internal configuration diagram.

In FIG. 2, 21 is an air flow meter (for example, a hot wire air flow meter) that measures the amount of air passing through the engine intake pipe, 22 is an idle switch that determines whether the engine is idle or not, and 23 is various sensors. An engine control device (microcomputer) that calculates the optimal fuel amount for the engine by taking in the signal and using digital calculation processing.
24 is an injector driven by a fuel injection pulse width signal from the engine control device 23.

As shown in FIG. 3, the engine control device 23 includes a driver 31 that drives an external actuator, an input/output port 32 that inputs the output values of various sensors as digital signals, and outputs pulses to the outside. Digital calculation processing is performed based on the sensor output value to calculate the fuel injection pulse width (
It is composed of a CPU 33 that calculates the fuel amount), a program for the CPU 33, a non-volatile memory 34 that stores constants, a volatile memory 35 that temporarily stores calculated variables, and the like. Among these, the contents of the CPU 33 are shown in the block configuration diagram shown in FIG.

In FIG. 1, the multistage connection mode when all compensation filter groups are selected will be explained first.

Electrical noise is removed from the air flow signal (voltage value) Qa measured by the air flow meter 21 at the hard filter 11. The digital filter 12 advances and compensates for the response delay of the hot wire air flowmeter 21. That is, since the output of the hot wire air flowmeter has a delay in rising with respect to a step change in the flow rate, this is approximated by a first-order delay and reverse compensation is performed.

Thereafter, the lead-compensated voltage value is converted into an air flow rate value Qsf in the flow rate engineering value conversion circuit 13, and the block 14 detects the difference between the lead-compensated air flow rate signal Qsf and the cylinder inflow air amount Qc. The pressure P is estimated, and in block 15, the intake pipe internal pressure P is multiplied by a function f (N, η, T) of the engine speed N, the volumetric efficiency η, and the intake air temperature T to calculate the amount of air Qc flowing into the cylinder. This cylinder inflow air amount is determined by block 1 in the digital calculation of discrete values.
4 is used to estimate the next intake pipe internal pressure P. In addition,
The volumetric efficiency η, which is an uncertain element, is determined by approximate calculation or table search using known parameters.

Reference numeral 16 denotes a fuel transport delay compensation filter, which compensates for the difference in the amount of air flowing in when calculating the fuel and when the intake valve is opened. In this embodiment, compensation is performed using a time delay element for one engine stroke. That is, the compensation filter 17 has the true value Q
Find c' using the formula below.

[0027]

[Math 1]

It can be found as follows. In the above equation, T is the transport time of the intake system.

When the true value Qc' of the inflow air flow rate is calculated, the intake pipe wall fuel adhesion compensating filter 17 calculates the air flow rate that compensates for changes in the state of the fuel liquid film adhering to the intake pipe wall. In this example, a filter is set based on the time constant of fuel evaporation and adhesion when a minute state change occurs from an arbitrary equilibrium point.
As shown in FIG. 4 described above, first-order advance compensation and first-order lag compensation are performed during transient operation. This compensation conveniently does not take into account wall flow. Also, compensation is performed using a transfer function.

Block 18 performs final fuel calculation based on the calculated cylinder inflow air flow rate QAf and the engine rotation N detected by the sensor.

A series of filters (
The block) elements are connected in multiple stages, and the CPU 33 (shown in FIG. 3) of the engine control device 23 has a filter path automatic change function, and the above series of filter groups is detected by the idle switch 22, throttle sensor, etc. They are selected or omitted as follows depending on the engine operating status.

That is, during transient operation, the series of filters 11, 12, 13, 14, 15, 16, and 17 are all connected and controlled to reach calculation block 18.

[0033] During idling, the filters 11 and 12
, 13, 14, and 15 are selected, and the transportation delay compensation filter 16 and the intake pipe wall fuel adhesion compensation filter 17 are selected.
is omitted to reach the fuel amount calculation block 18.

During high load operation, the filters 11, 12,
13 is selected, and blocks 14 and 15, transportation delay compensation filter 16, and fuel adhesion compensation filter 17 are omitted to reach fuel calculation block 18.

FIG. 5 shows a block diagram in which the various compensation filters shown in FIG. 1 are combined into two systems: a cylinder inflow air amount compensation system and a fuel compensation system. The fuel compensation system including the fuel lag compensation filter 16 and the fuel adhesion compensation filter 17 is summarized as a transfer function of one system, and becomes a first-order advance filter with second-order numerator/first-order denominator.

FIG. 6 shows the fuel compensation system of FIG. 5 and a gain diagram when this system is omitted. In this embodiment, when the fuel compensation system is included, the system becomes a leading filter in all frequency ranges with respect to air flow rate changes in the transient state of the engine, and when it is omitted, it becomes a lag filter.

FIG. 7 shows the program task schedule of the engine control device of this embodiment, and FIG. 8 shows the angle interrupt routine of the engine control device. This routine starts fuel injection to the engine when an angle interrupt occurs.

The contents of the engine control timer schedule will now be explained with reference to FIGS. 7 and 9 to 11.

As shown in FIG. 7, when a timer interrupt occurs, it is scheduled in step 701, a 4 msec job is executed in step 702, and a 10 msec job is executed in step 703.
secjob(1) and 10msecjob(2) are respectively selected.

In the 4 msec job, as shown in the flowchart of FIG. 9, in step 901, the output of the hot wire air flow meter is read using an A/D converter or the like. Step 9
At step 02, the digital filter 12 advances and compensates the output of the air flow meter.

In the 10 msec job (1), as shown in the flowchart of FIG. 10, the intake pipe internal pressure P is calculated in step 1001, and the cylinder inflow air amount Qc is calculated in step 1002. In step 1003, stroke delay compensation (fuel delay compensation) is performed, and in step 1004, intake pipe wall fuel adhesion compensation (liquid film compensation) QAf is performed.

In 10 msec job (2), a fuel injection amount calculation routine as shown in the flowchart of FIG. 11 is executed. In step 1101, it is determined whether the idle switch is on or off, and if it is on, the cylinder inflow air amount Qc is selected, and if it is off, the cylinder inflow air amount QAf including stroke delay compensation and fuel adhesion compensation is selected, and step 1104 Perform fuel calculations.

According to this embodiment, the following effects can be achieved by determining whether the engine is transient or steady using an idle switch or the like and changing the connection mode of various compensation filters used for fuel amount calculation.

That is, during transient operation, in addition to compensating for the response delay of the air flow meter, estimation calculation of the cylinder air inflow amount and compensation for fuel adhesion on the intake pipe wall, which is particularly required during transient operation, are performed, which solves the conventional problems. A during transient operation, which was supposed to be
/F enables precise control. Furthermore, in the case of idling operation, smooth idling operation is compensated by omitting delay compensation of the filter 16. In other words, the transportation time T used in the formula for calculating the true value Qc' in the filter 16 becomes too large during idling and exceeds the limit of compensation calculation, so by omitting the use of this filter 16 during idling, the control In addition, during steady operation such as idling operation, A/F control accuracy can be maintained well even if the intake pipe wall fuel adhesion filter 17, which is particularly necessary during transient operation, is omitted.

[0045] Also, during high load operation, the compensation filter 1
4, 15, 16, 17, etc., the control system can be stabilized by lowering the gain for the specific intake pipe pulsation frequency that has been a problem during this operation. Note that even if a filter is provided to block the intake pipe pulsation frequency from the cylinder inflow air amount measurement value, A/F control that is not affected by the intake pipe pulsation can be executed.

[0046]

[Effects of the Invention] As described above, according to the present invention, various filters used for calculating the amount of fuel in the engine are connected in multiple stages, and the connection mode of these filters is appropriately changed according to the operating state of the engine. , it is possible to achieve both improved accuracy of air-fuel ratio control and smooth A/F control operation in steady-state operation and transient operation.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing block groups of various compensation filters in a fuel amount calculation system in an embodiment of the present invention.

FIG. 2 is a hardware configuration diagram of an engine control system used in the above embodiment.

FIG. 3 is an explanatory diagram showing the internal configuration of the engine control device used in the above embodiment.

FIG. 4 is an explanatory diagram showing the principle of compensation for fuel adhesion on the intake pipe wall used in the above embodiment.

FIG. 5 is an explanatory diagram showing the calculation operation of the fuel compensation system of the above embodiment.

FIG. 6 is a diagram comparing the gains when a part of the fuel compensation filter system of the above embodiment is omitted and when it is not.

FIG. 7 is a flowchart showing an operation program of the engine control device of the above embodiment.

FIG. 8 is a flowchart showing a fuel injection operation routine of the above embodiment.

FIG. 9 is a flowchart showing the compensation operation of the air flow system of the above embodiment.

FIG. 10 is a flowchart showing operations of various compensation filters used in the above embodiment.

FIG. 11 is a flowchart showing the mode selection operation of the multistage connection compensation filter used in the above embodiment.

[Explanation of symbols]

11...Hard filter, 12...Air flow meter compensation filter, 14...Intake pipe pressure calculation block, 15...Cylinder inflow air amount calculation block, 16...Fuel transport delay compensation filter,
17... Intake pipe wall fuel adhesion compensation filter, 18... Fuel calculation block, 21... Hot wire air flow system, 22... Idle switch, 23... Engine control device (fuel calculation means with compensation filter, filter route automatic change means), 24...Injector.

Claims (2)

[Claims] Claim 1: An engine control device comprising means for measuring the intake air flow rate of an engine using an air flow sensor and calculating an optimum fuel amount for the engine based on the measured value, comprising: Various types of compensation filters are connected in multiple stages, and a means is provided for automatically changing the filter path by selecting filters to be used and filters to be omitted from among these various types of compensation filters according to the operating state of the engine. Characteristic engine control device. 2. The various types of compensation filters include various types of digital filters connected in multiple stages for use in compensating for the air flow rate sensor, compensating for fuel transport delays in the intake system, compensating for fuel adhering to the intake pipe wall of the engine, etc. The filter path automatic change means detects transient operation and steady operation of the engine from a throttle sensor, an idle switch, etc., and changes the filter in the compensation filter group based on the filter connection mode suitable for each state. An engine control device characterized by being set to allow selection of use or omission of.