JP2716596B2 - Engine control device - Google Patents

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 for determining an optimum fuel amount based on a measured air flow to control an air-fuel ratio (A / F) of an engine.

[0002]

2. Description of the Related Art Conventionally, electronic engine control systems for measuring the flow rate of air flowing through an intake pipe of an engine and calculating the amount of fuel injected from an injector (fuel injection pulse width) have been widely used.

[0003] In the engine control device, the fuel amount is calculated by performing various compensations in order to enhance the A / F control accuracy.
For example, the technique disclosed in Japanese Patent Application Laid-Open No. 55-114609 compensates for this fuel adhesion in consideration of the fact that the change in the state of adhesion and evaporation of fuel injected from the injector on the intake pipe wall affects the air-fuel ratio. While calculating the required fuel amount.

[0004] Compensation for the above-mentioned fuel adhesion is particularly important during transient operation. FIG. 4 shows, as an example of the transient operation, the relationship between the throttle opening, the basic fuel amount, the compensation of the fuel adhered to the intake pipe wall, and the A / F during the acceleration operation. As shown in FIG. 4, increased fuel injection is required at the time of acceleration operation. At the stage of acceleration, however, the amount of deposited fuel initially increases, so that the A / F is increased only by the basic fuel amount (fuel injection pulse width) as shown by the solid line. When the vehicle reaches a lean speed and reaches the target speed, a part of the attached fuel evaporates and the A / F becomes rich. Therefore, during and immediately after the transient operation, the fuel injection control is performed as shown by the broken line.
The A / F is maintained at the target value as shown by the broken line by compensating for the next advance and the first-order lag.

In the above-mentioned conventional example, as a method of calculating a required fuel amount for maintaining a target A / F, a change in a state of fuel adhesion in an intake pipe of an engine is determined by an equilibrium adhesion obtained in relation to an engine load (intake pipe pressure). Calculate by taking into account the amount (the amount that constantly adheres to the intake pipe wall when the engine load is in an equilibrium state), the amount that adheres at the present time, and the current fuel adhesion rate,
The fuel amount is determined by adding and subtracting the calculated value to the basic fuel amount. In terms of the 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. I do.

Recently, a technique has been proposed in which a compensation filter for a response delay of an air flow sensor and a compensation filter for a fuel transport delay of an engine intake system are connected to the intake pipe wall fuel adhesion compensation filter in multiple stages when obtaining a fuel amount. Have been.

[0007]

By the way, when such a multi-stage filter connection system is analyzed in the frequency domain, it is found that a certain region in the intake pipe pulsation frequency (for example, in the case of full throttle opening of the engine and a high load operation close to it when the engine is in a high load operation). There is a portion where the pulsation frequency is high) and a portion where the gain is high with respect to electric noise, and there is also an operation region where the control system lacks stability.

Further, when a relatively long time is required for fuel transport in the intake pipe as in the idling operation, the calculation of transport delay compensation exceeds the limit, and if this compensation filter is used as it is, control will be hindered. Sometimes.

The present invention has been made in view of the above points, and an object of the present invention is to improve various problems that occur in the above-described multi-stage filter connection system, and to achieve high precision control of the air-fuel ratio control system and smooth operation. It is an object of the present invention to provide an engine control device which guarantees a proper operation.

[0010]

In order to achieve the above object, the present invention basically proposes the following means for solving the problems.

[0011] Namely, the present invention provides an engine control apparatus having means for measuring the intake air flow rate of the engine, calculates the optimum amount of fuel the engine on the basis of the measured value using an air flow sensor, said air flow sensor From the output of
The system for calculating the optimal fuel amount has at least the air flow rate
Sensor output to compensate for sensor output delay (response delay)
Force compensation filter and compensation for fuel transfer delay of intake system
Filter for compensating fuel transfer delay and engine intake pipe wall
With fuel to compensate for changes in the state of the fuel liquid film attached to the
Are connected in multiple stages and the engine
During the transfer operation, the sensor output compensation filter
Using a compensation filter and a fuel adhesion compensation filter.
Except during operation, of these filters, the fuel transport delay
Omission of the use of the filter for fuel compensation
Filter path automatic changing means for changing
You .

[0012]

According to the above configuration, by selecting use or omission of various compensation filter groups in relation to the engine operating state, the path of the multi-stage filter can be changed.

In particular, in the present invention, the air flow rate sensor
Output compensation filter, fuel transport delay compensation filter, with fuel
Selectively use the arrival compensation filter in multiple stages according to the situation,
The connection required for calculation of the optimal fuel amount
When calculating the amount of air flowing into a cylinder, the air flow sensor
Compensation for fuel output delay, lead for fuel transport delay
Engine compensation and advance compensation for fuel adhesion
It is selectively added as follows according to the state.

For example, at the time of transient operation such as engine acceleration, all of the above various compensation filters are selected and the air flow is selected.
Compensation for advance of output delay of fuel sensor, delay of fuel transport
With advance compensation for fuel adhesion
The amount of air flowing into the cylinder and, consequently, the target fuel amount are calculated.
You. On the other hand, steady operation such as idle operation and high load operation
At times, the air flow from the various compensating filters
Select only the output compensation filter of the
Use of transmission delay compensation filter and fuel adhesion compensation filter is omitted.
Abbreviated.

If the filter selection and omission are automatically set as described above, all the compensations are satisfied during the transient operation, and the fuel adhesion on the intake pipe wall, which is a problem particularly during the transient operation, is also compensated. On the other hand, at the time of high load operation or idling operation, the connected filter group is selectively used or omitted, which is inconsistent with the control theory of the dynamic model. However, if the filter is designed so that the DC gain is 0 db, it has no effect when the engine is stationary.

The gain of the filter path can be adjusted by selectively using or omitting the filter. As a result, when a region of a certain intake pipe pulsation frequency has a high gain due to the multistage filter connection (for example, the intake pipe pulsation frequency at the time of high load operation), the minimum required compensation filter at this time, that is, the compensation presented above In the filter,
In particular, a filter (cell) that compensates for the output delay of the air flow sensor
If only the use of a filter for compensating the sensor output is selected and the rest is omitted, the gain can be lowered and the control system can be stabilized.

Also, during idling operation,
By omitting the fuel transport delay compensation is that there is no, rather to allow for a smooth idle control. Moreover,
Especially during steady operation such as idle operation, especially during transient operation
A / F control accuracy even if necessary fuel deposition filter is omitted
Can be kept good.

The transient determination will not be erroneously made if an idle switch and a throttle sensor that directly reflect the driver's intention are used.

[0019]

BRIEF DESCRIPTION OF THE DRAWINGS FIG.

FIG. 1 is a block diagram of various compensation filters in an engine control apparatus according to one embodiment of the present invention, FIG. 2 is a hardware configuration diagram showing a part of the engine control system, and FIG. FIG.

In FIG. 2, reference numeral 21 denotes an air flow meter (for example, a hot wire air flow meter) for measuring the amount of air passing through the engine intake pipe, 22 an idle switch for determining whether the engine is idle or not, and 23 various sensors. Engine control device (microcomputer) that takes in the signal of
Reference numeral 24 denotes an injector driven by a fuel injection pulse width signal from the engine control device 23.

As shown in FIG. 3, the engine control unit 23 includes a driver 31 for driving an external actuator, an input / output port 32 for inputting the output values of various sensors into digital signals, and outputting a pulse to the outside. CPU 33 for performing digital arithmetic processing based on the sensor output value to calculate the fuel injection pulse width (fuel amount); nonvolatile memory 34 for storing programs of CPU 33 and constants; and volatile memory for temporarily storing calculated variables 35. Among them, the contents of the CPU 33 are block diagrams shown in FIG.

Referring to FIG. 1, the multi-stage connection mode when all the compensation filter groups are selected will be described.

From the air flow rate signal (voltage value) Qa measured by the air flow meter 21, electric noise is removed by the hard filter 11. Digital filter (sensor output compensation
Filter) 12 exits hot wire type air flow meter 21 the response delay of (
To compensate the advance against the force lag). That is, since the output of the hot wire type air flow meter has a delay in rising with respect to the step change of the flow rate, this is approximated by a first-order delay and inverse compensation is performed. In addition, a later-described filter 12 is connected to the subsequent stage of the filter 12.
Various compensation filters 13 to 17 are also digital filters.
Is done.

Thereafter, the advance compensated voltage value is converted into an air flow value Qsf by the flow engineering value conversion circuit 13, and the block 14 is moved into the intake pipe by the difference between the advance compensated air flow signal Qsf and the cylinder inflow air amount Qc. The pressure P is estimated, and in block 15, the air quantity Qc flowing into the cylinder is calculated by multiplying the intake pipe pressure P by the function f (N, η, T) of the engine speed N, the volumetric efficiency η, and the intake temperature T. In the digital calculation of the discrete value, the amount of air flowing into the cylinder is represented by block 1
4 is used to estimate the next intake pipe pressure P. In addition,
The volume efficiency η, which is an uncertain factor, is determined by approximation calculation or table search of known parameters.

Numeral 16 denotes a fuel transport delay compensation filter which compensates for a difference between the amount of inflow air at the time of fuel calculation and at the time of intake valve opening.
In the present embodiment, compensation is performed by a time delay element for one stroke of the engine. That is, the compensation filter 17 calculates the true value Q
c ′ is obtained by the following equation.

[0027]

[Number 1] Qc' = e ^-ST · Qc

[0028] 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 compensation filter 17 calculates an air flow rate that compensates for a change in the state of the fuel liquid film adhering inside the intake pipe wall. In this embodiment, a filter is set based on the time constant of evaporation and adhesion of the fuel when the state changes minutely from an arbitrary equilibrium point, and as shown in FIG. Perform delay compensation. This compensation does not take wall flow into account for convenience. In addition, compensation is performed using a transfer function.

A block 18 performs a final fuel calculation based on the calculated cylinder inflow air flow rate QAf and the engine speed N detected by the sensor.

A series of filter (block) elements used for the fuel calculation described above are connected in multiple stages, and the CPU 33 (shown in FIG. 3) of the engine control unit 23 has an automatic change function of the filter path. The groups are selected and omitted as follows according to the engine operating state detected by the idle switch 22, the throttle sensor, and the like.

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

At the time of idling, the filters 11, 1
2, 13, 14, 15 are selected, and the transport delay compensation filter 16 and the intake pipe wall fuel adhesion compensation filter 1 are selected.
7 is omitted, and the process proceeds to the fuel amount calculation block 18.

At the time of high load operation, the filters 11, 12,
The use of up to 13 is selected, and the process proceeds to the fuel calculation block 18 by omitting the blocks 14, 15 and the transport delay compensation filter 16 and the fuel adhesion compensation filter 17.

FIG. 5 is a block diagram in which the various compensation filters of FIG. 1 are combined into two, a cylinder inflow air amount compensation system and a fuel compensation system. The fuel compensating system including the fuel delay compensating filter 16 and the fuel adhesion compensating filter 17 is a first-order filter having a second-order numerator and a first-order denominator when summarized by a transfer function of one system.

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 filter is advancing in all frequency ranges with respect to the change in the air flow rate in the transient state of the engine, and when this is omitted, the filter is a lag filter.

FIG. 7 shows a program task schedule of the engine control device according to the present embodiment, and FIG. 8 shows an angle interruption routine of the engine control device. When an angle interruption occurs, fuel injection to the engine is started.

Here, the contents of the timer schedule for engine control will be described with reference to FIGS. 7 and 9 to 11.

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

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

In 10 msec job (1), as shown in the flowchart of FIG. 10, the intake pipe 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.

At 10 msecjob (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. If it is on, the cylinder inflow air amount Qc is selected. If it is off, the cylinder inflow air amount QAf including stroke delay compensation and fuel adhesion compensation is selected. Perform the fuel calculation with.

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

That is, in the transient operation, in addition to the response delay compensation of the air flow meter, the estimation calculation of the cylinder air inflow amount and the compensation of the fuel adhered to the intake pipe wall which is particularly required during the transient operation are performed. A during transient operation
/ F enables precise control. Further, in the case of the idling operation, smooth idle operation is compensated by omitting the delay compensation of the filter 16. That is, the transport time T used in the equation for calculating the true value Qc 'in the filter 16 becomes too large during the idling operation and exceeds the limit of the compensation calculation. And the A / F control accuracy can be kept good even in a steady operation such as an idling operation, even if the intake pipe wall fuel adhesion filter 17 which is particularly necessary in a transient operation is omitted.

During high-load operation, the compensation filter 1
The control system can be stabilized by lowering the gain for a specific intake pipe pulsation frequency which has been a problem during this operation by omitting 4, 15, 16, 17 and the like. Note that even if a filter that cuts off the intake pipe pulsation frequency is provided in the measured value of the amount of air flowing into the cylinder, A / F control that is not affected by intake pipe pulsation can be performed.

[0046]

As described above, according to the present invention, various filters used for calculating the fuel amount of 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. In addition, it is possible to achieve both improvement in the accuracy of the air-fuel ratio control in the steady operation and the transient operation and smooth A / F control operation.

[Brief description of the drawings]

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

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

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

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

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

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

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

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

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

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

FIG. 11 is a flowchart showing a mode selection operation of the multistage connection compensation filter used in the 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,
Reference numeral 17: filter for compensating for fuel adhesion to the intake pipe wall, 18: fuel calculation block, 21: hot-wire air flow system, 22: idle switch, 23: engine control device (fuel calculation means with compensation filter, automatic filter path changing means) 24 ... Injector.

Continued on the front page (72) Inventor Teruji Sekozawa 1099 Ozenji Temple, Aso-ku, Kawasaki City, Kanagawa Prefecture Inside Hitachi, Ltd.System Development Laboratory Co., Ltd. In-house (56) References JP-A-64-32050 (JP, A) JP-A-56-47638 (JP, A) JP-A-3-246345 (JP, A) JP-A-4-40322 (JP, A)

Claims (2)

(57) [Claims] 1. An engine control device comprising means for measuring an intake air flow rate of an engine using an air flow rate sensor and calculating an optimum fuel amount of the engine based on the measured value. System to calculate fuel amount
At least compensate for the output delay of the air flow sensor.
Output compensating filter for intake and fuel transfer of intake system
A fuel transport delay compensation filter to compensate for the delay;
Compensates for changes in the state of the fuel liquid film adhering to the engine intake pipe wall
The fuel output compensation filter is connected in multiple stages and the sensor output compensation filter is used during transient operation of the engine.
Filter, fuel transport delay compensation filter, fuel adhesion compensation filter
Filter and use these filters except during transient operation.
The fuel transport delay compensation filter and the fuel adhesion compensation filter
An engine control device comprising : a filter path automatic changing unit that eliminates use of a filter . 2. The sensor output compensating filter, fuel transport.
The delay compensating filter and fuel adhesion compensating filter
A digital filter having the function, the filter path automatic changing means, transient luck of the engine
It has a sensor that detects rolling and steady operation, and its operating state
The sensor output compensation filter and fuel transport delay compensation
Filter and fuel adhesion compensation filter should be used and omitted
2. The engine control device according to claim 1 , wherein the setting is performed to select a filter .