JPS6161012A - Output control device of heat wire sensor - Google Patents

Abstract

PURPOSE:To suppress a sacrifice of a response speed, to prevent an influence exerted on an engine, of a pulsation of air, and to prevent the hunting by constituting a titled device so that an output of a heat wire sensor is smoothed, only when a pulsation is generated in air in a suction path. CONSTITUTION:A suction air quantity in a suction path 7 is influenced by a variation quantity and a variation direction per unit time of an opening of a throttle valve 3. Accordingly, if the variation rate of the throttle opening and the variation rate of the suction air quantity are the same, and also the variation direction of the throttle opening and the variation direction of the suction air quantity are the same, it can be discriminated that the variation of the suction air quantity is not due to a pulsation of air, and if at least one of the variation rate and the variation rate and the variation direction is different, it can be discriminated that the variation of the suction air quantity is due to a pulsation of air. Therefore, a prescribed processing is executed by inputting an output of the heat wire sensor 2 and an output of a throttle position sensor 18 to a controlling circuit 22, so that an output of the heat wire sensor 2 is smoothed only when the pulsation of air is generated.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is an internal combustion engine equipped with a heat wire sensor used to measure the intake air amount of the engine, in which the pulsation state of the intake air is accurately determined by a microcomputer or the like. The present invention relates to an output control device for a heat wire sensor that smoothes the output of a heat wire sensor by making a determination as follows.

[Conventional technology]

A heat wire sensor installed in the intake passage of an internal combustion engine is generally known as a hot wire flowmeter, and is disclosed in Japanese Patent Application Laid-open No. 57-1989.
It is known from the publication No. 2433. This heat wire sensor is known to have a fast response speed to air flow rate. On the other hand, in the intake passage of an internal combustion engine, air pulsates at every predetermined crank angle in accordance with the intake, compression, explosion, and exhaust processes of the engine body. Therefore, when the amount of intake air in the intake passage is measured using the heat wire sensor having a fast response speed, the output of the heat wire sensor fluctuates due to the direct influence of air pulsation. As a result, an error occurs between the amount of air actually introduced into the engine's combustion chamber and the amount of air measured by the heat wire sensor, which can lead to overrich or overlean fuel, sometimes causing engine hunting. .

Conventionally, as a measure to prevent engine hunting due to the detection of air pulsation, when the engine rotation speed reaches a predetermined number of times -F, it is determined that the air is in a pulsating state, and the output of the heat wire sensor is smoothed. is proposed.

Furthermore, as another method, a method has been proposed in the past in which the output of the heat wire sensor is taken in at a crank angle that is not affected by air pulsation.

[Problems to be solved by the invention]

According to the former conventional method, the air pulsation state is determined based on the engine rotational speed. However, since there is no direct relationship between air pulsation and engine speed, the output of the heat wire sensor is smoothed even when air pulsation is not actually occurring. As a result, the high response speed, which is an advantage of the heat wire sensor, is unnecessarily sacrificed.

In addition, according to the latter method, the timing at which the output data of the heat wire sensor is captured increases as the engine speed increases, and as a result, the load due to crank angle interrupts increases and the execution of the main routine is delayed. , there is a problem that updating of data other than the output of the heat wire sensor is delayed, resulting in a region where the engine operation is unstable.

[Means for solving problems]

In view of the above-mentioned problems in the prior art, an object of the present invention is to compare the amount and direction of change in the throttle opening with the amount and direction of change in the amount of intake air obtained from the output of the heat wire sensor. Accurately captures air pulsations in the passageway, thereby smoothing the output of the heat wire sensor only when air pulsations occur, and without smoothing the output of the heat wire sensor when air pulsations can be ignored. Based on the concept of direct import,
Prevents the influence of air pulsation on the engine while minimizing the sacrifice of response speed of the heat wire sensor output, thereby preventing engine hunting! 1- It is about doing.

The structure of the present invention for achieving the above object is shown in FIG. In FIG. 1, what is provided by the present invention is a heat wire sensor for detecting the amount of intake air provided in the intake passage of an internal combustion engine, and a heat wire sensor for detecting the amount of air in the intake passage. A heat wire sensor that measures the rate of change in the output of a heat wire sensor that measures the amount of change in air permeability, and a heat wire sensor that determines whether the amount of air in the intake passage is decreasing or increasing based on the output of the heat wire sensor for each unit of time. a throttle position sensor installed in the intake passage for detecting the opening of the throttle valve; and a throttle position sensor for measuring the amount of change in the opening of the throttle valve per unit time based on the output of the throttle position W sensor. A position sensor output change rate measuring means, a throttle position sensor output change direction determining means for determining whether the opening degree of the throttle valve is decreasing or increasing based on the output of the throttle position sensor for each unit time, and a heat The change direction of the air amount obtained from the output of the output change direction determination means of the wire sensor is different from the change direction of the throttle valve opening obtained from the output of the output change direction determination means of the throttle position sensor, and , the rate of change in the air amount obtained from the output of the output change rate measuring means of the heat wire sensor is outside the predetermined tolerance range for the change rate of the throttle valve opening obtained from the output of the output change rate measuring means of the throttle position sensor. This is an output control device for a heat wire sensor, characterized in that it is equipped with an output smoothing means for the heat wire sensor, which smoothes the output of the heat wire sensor only when the sensor is in the position of the heat wire sensor.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to FIG. 2 and subsequent drawings.

FIG. 2 is a system diagram of an electronically controlled fuel injection engine to which the present invention is applied. The air sucked from the air cleaner 1 is connected to an air flow meter consisting of a heat wire sensor 2,
The air is sent to the combustion chamber 9 of the engine body 8 through an intake passage 7 that includes a throttle valve 3, a surge tank 4, an intake boat 5, and an intake valve 6. The throttle valve 3 is linked to an accelerator pedal 10 in the driver's cab. The combustion chamber 9 is defined by a cylinder head 11, a cylinder block 12, and a piston 13, and the exhaust gas generated by combustion of the air-fuel mixture is passed through an exhaust valve 14, an exhaust boat 15, an exhaust manifold 16, and an exhaust pipe 17. Released into the atmosphere.

A throttle position sensor 18 detects the opening degree of the throttle valve 3, a water temperature sensor 19 detects the engine temperature,
20 is an exhaust manifold; 2 is an air-fuel ratio sensor that detects the oxygen temperature at the collecting portion of 5; and 2 is a fuel injection valve.

The output of the heat wire sensor 2 and the output of the throttle position sensor 18 are input to a control circuit 22.

As mentioned above, the amount of air in the intake passage 7 pulsates at every predetermined crank angle according to the suction, compression, explosion, and exhaust processes in the engine body 8.The heat wire sensor 2 has a fast response speed, so , this air pulsation is detected.

By the way, in addition to the influence of the air pulsation mentioned above, the amount of intake air in the intake passage 7 is influenced by the amount of change per level time of the opening of the throttle valve 3 (rate of change of the throttle opening) and the direction of change. . That is, when the rate of change in the throttle opening is sufficiently small, such as when the engine is idling or driving at a constant speed, the air pulsation within the intake passage 7 is negligibly small, and the throttle opening increases. When the throttle opening is changing in the direction, the intake air amount tends to increase accordingly, and when the throttle opening is changing in the decreasing direction, the intake air amount also tends to decrease accordingly.

Therefore, if the rate of change in the throttle opening and the rate of change in the intake air amount are almost the same, and the direction of change in the throttle opening and the direction of change in the intake air amount are the same, then the fluctuation in the intake air amount is due to air pulsation. If at least either the rate of change or the direction of change is different, it can be determined that the change in intake air amount is due to air pulsation. Fluctuations in the amount of intake air that are not caused by air pulsation occur simply in response to changes in the throttle opening, and in this case, the output of the heat wire sensor 2 may be used as the actual amount of intake air sent into the combustion chamber 9. , it is not necessary to smooth the output of the heat wire sensor 2. The present invention has been made with attention to this point, and by performing the above discrimination, the state of air pulsation in the intake passage 7 is accurately identified, and the heat wire sensor 2 is activated only when air pulsation is occurring. Performs output smoothing. For this purpose, the output of the heat wire sensor 2 and the output of the throttle position sensor 18 are taken into the control circuit 22, and processing to be described later is performed.

FIG. 3 is a block diagram showing an example of the configuration of the control circuit 22 shown in FIG. 2. In FIG. In FIG. 3, the same parts as those in FIG. 2 are given the same reference numerals.

The voltage signal from the heat wire sensor 2 and the voltage signal from the throttle position sensor 18 are transferred to an analog-to-digital (A/D) converter 4 having an analog multiplexer function.
Microprocessor (MPI+)
In response to instructions from 42, the signals are sequentially converted into binary signals.

A pulse signal every 30 degrees of crank angle from the crank angle sensor 44 (not shown in FIG. 2) is sent to the input/output circuit (110
The signal is fed into a known speed signal forming circuit in circuit 46, which forms a binary symbol representing the rotational speed of the engine. Pulse signals for every 360 degrees of crank angle from the other crank angle sensor 48 (also not shown in FIG. 2) are similarly sent to the ■10 circuit 74, and cooperate with the above-mentioned pulse signals for every 30 degrees of crank angle. The signal is used to form an interrupt request signal, a fuel injection start signal, a cylinder discrimination signal, etc. for fuel injection pulse width calculation.

In the input/output circuit (110 circuit) 50, a well-known fuel injection control circuit including a presettable down counter, register, etc. is provided, and the pulse width is determined from binary data regarding the injection pulse width sent from the MPU 42. form an ejection pulse signal having a The binary data regarding the injection pulse width includes data corresponding to the intake air amount detected by the heat wire sensor 2, which is appropriately smoothed using a method described in detail later. This injection pulse signal is sent to the fuel injection valves 21a and 21b sequentially or simultaneously via a drive circuit (not shown) to energize them. As a result, fuel 1 is injected in an amount corresponding to the pulse width of the injection pulse signal.

The A/D converter 40 and I10 circuits 46 and 50 are connected to an MPU 42, a random access memory (RAM) 52, and a read-on memory (ROM) 54, which are the main components of the microcomputer, through an I1 bus 56. Data and instructions are transferred via this bus 56.

The ROM 54 contains a main processing routine program, an interrupt processing routine program for calculating fuel injection pulse width, an interrupt processing routine program for calculating coefficients such as a partial lean correction coefficient, and other programs, as well as a slot according to the present invention. - An AlIC (Analog-to-Digital Conversion) interrupt routine program for the output of the 7 Torr position sensor 18 and a ^r1C interrupt routine program for the output of the heat wire sensor 2 are preliminarily stored. 120M54 further stores in advance various data necessary for arithmetic processing in the various programs listed in "-" and a table that associates the intake air amount Ga with the output value of the heat wire sensor 2.

As the control circuit 22, various configurations different from those described above can be applied. For example, without providing a speed signal forming circuit in the 10 circuit 46, it is also possible to configure the MPU 42 to directly receive pulse signals for each predetermined crank angle and form the speed signal using software. Further, without providing a fuel injection control device in the I10 circuit 50, the configuration may be such that a signal having a logical value of "1" is generated only for a time corresponding to the injection pulse width using software.

Next, the operation of the ADC interrupt routine for the output of the throttle position sensor 18 by the control circuit 22 described above will be explained with reference to FIG. In FIG. 4, in step 401, an ADC interrupt routine for the output of the throttle position sensor 18 is started, which interrupts the main routine (FIG. 7) at predetermined time intervals (for example, every 8 milliseconds). At 402, the throttle opening signal which is the output of the throttle position sensor 18 is taken into the 1 yen 142.

Next, in step 403, the MPII 42 calculates the throttle opening TA from the throttle opening signal. Then,
In step 404, the difference between the throttle opening degree TA taken in and calculated in the current interrupt routine and the throttle opening degree Ta taken in and calculated in the previous interrupt routine is calculated, and the result ΔTA is calculated. RIM 5
The data is stored in a predetermined area of No.2.

Next, in step 405, it is determined whether ΔTA is positive. If ΔTA is positive, in step 406 MPI
Set the first flag F I- in I 42 to 1″;
If not, the first flag FL is set to “ in step 407.
After step 406 or 407, in step 408, the previous throttle opening is retrieved by the current interrupt routine and stored in a predetermined area in the calculated throttle opening TAt-RAM 52. Degree T
, is updated with the current throttle opening TA. Step 4
After 08, this interrupt routine ends and the control circuit 22
The processing returns to the main routine at step 511.

If the first flag FL is set in step 406, this indicates that the throttle opening is increasing, and if the first flag FL is reset in step 407, the throttle opening This indicates that the opening degree is not changing or is changing in a decreasing direction. This first flag FL is used in the AlIC interrupt routine for the output of the heat wire sensor (HW) 2 by the control circuit 22, which will be explained next with reference to FIG.

In FIG. 5, in step 501, an interrupt is executed to the main routine at predetermined time intervals (for example, every 8 milliseconds), and the interrupt routine returns to the output of the heat wire sensor 2. Then, the output voltage of the heat wire sensor 2 is AD converted by the A/D converter 40 and stored in a predetermined area in the RAM 52. Next, in step 503, a table in the ROM 54 is looked up (searched) to read out the air amount Ga and stored in a predetermined area of the RAM 52. Next, in step 504, the difference △Ga between the intake air amount Ga read in the current interrupt routine and the intake air IGa read in the previous interrupt routine is calculated, and the result △Ga is set at a predetermined value on RA) 152. Store in area. Next, in step 505, it is determined whether 8Ga is positive or not. If 80a is positive, that is, if the intake air amount is changing in the direction of increasing, step 506
The second flag FR in the MPI+ 52 is set to 1'' in step 507, and if ΔGa is not positive, that is, if the intake air amount is not changing or is changing in a decreasing direction, the process proceeds to step 507. and resets the second flag FR to 0''. After step 506 or 507, step 508
At step 50, the value of the first flag FL stored in the MPU 52 is fetched according to the flow shown in FIG.
At step 9, the first flag FL and the second flag FR are compared. If the first flag Fl- and the second flag FR do not match, that is, if the direction of change in throttle opening and the direction of change in intake air amount are one increasing direction and the other decreasing direction, step Proceed to 510 and perform RA according to the flow shown in Figure 4.
MP the amount of change in throttle opening △TA stored in M52
The value obtained by multiplying △T by a predetermined constant α is set as GT.GTA is the value obtained by multiplying 8T by a constant in order to directly compare it with ∆G.Predetermined The constant α is selected such that the amount of change ΔGa in the intake air amount Ga is within the range expressed by GTA−β<ΔG<GTA+β, with air pulsation in the intake passage 7 being negligible. However, β is a constant.

Next, in step 512, it is determined whether or not the amount of change ΔGa in the intake air amount Ga is within the above range. The directly obtained intake air amount Ga is set as the air amount Ga that actually entered the combustion chamber. If it is not within the range, it is determined that air pulsation due to engine processes and noise cannot be ignored, and the process proceeds to step 514, where the intake air amount is determined. A value obtained by smoothing Ga is calculated.

An example of the smoothing calculation and the calculation of ΔGa in step 514 will be explained with reference to the flowchart of FIG.

First, in step 601, the intake air amount Ga successively produced in the current routine is compared with the intake air amount IGa successively produced in the previous routine.

If the current intake air amount Ga is larger than the previous intake air IGa, in step 602 a predetermined area in the RAM 52 is used as a counter and the value RC is incremented by one, and in step 603 the counter value RC is changed to the set value Determine whether or not it is greater than or equal to the above. If not, the process proceeds to step 606, where the current intake air amount Ga is stored in a predetermined area in the RAM 52 as the maximum intake air IMAX Ga. When RC becomes X or more, a third flag Fl indicating that the intake air amount is increasing is set in step 604, and the counter value R is set in step 605.
After setting C to zero, proceed to step 606, step 6
From step 02 to step 606, the maximum value of the amount of intake air when the period in which the amount of intake air is increasing continues while the interrupt routine is repeated X times is determined.

In step 601, if the current intake air amount Ga is not greater than the previous intake air amount Ga, the process advances to step 607; if the current intake air amount Ga is less than the previous intake air amount Ga, the process advances to step 608; If so, the process returns to the main routine in step 515 (FIG. 5).

In steps 608 to 612, the intake air amount G
The minimum value MTN Ga of the intake air amount when the period in which a decreases continues while the interrupt routine is repeated seven times is determined, and at this time the flag FR is set and the counter value LC is cleared.

Proceeding from step 606 or 612 to step 613,
It is determined whether the flag FT is set, and step 61
At step 4, it is determined whether the flag FD is set.

When both flags FiFD are set, it is time to smooth the intake air amount, and step 615
At 1^X the average value of Ga and old NGa, then step 6
The flags FT and FD are reset in steps 16 and 617, respectively, and the process returns to the main routine in step 515.

If flags FT and FD are not set in steps 613 and 614, the process advances to step 515 and returns to the main routine.

With the above operation, the intake air amount is smoothed only when it is determined that air pulsation is occurring, and the sacrifice in response speed of the heat wire sensor is minimized.

Next, the operation of the main routine processing program by the control circuit 22 described above will be explained with reference to FIG. In FIG. 7, at step 701, certain values are stored in the RAM 52 as various initial values when the engine is started, and control is performed using the values when the engine is started.

Next, in step 702, the engine speed N[! is calculated from the crank angle and time.

Next, in step 703, the intake air amount Ga is calculated based on the output value of the heat wire sensor 2, the throttle opening degree, and the rate of change thereof.

Next, in step 704, the intake air amount Ga and the engine rotation speed N[! From this, calculate the amount of intake air per rotation to determine the basic injection amount of fuel and advance of the crank angle.

Next, in step 705, an increase value for increasing the amount of fuel relative to the basic injection amount is calculated in cold weather or when preventing overheating of the exhaust system.

Next, in step 706, the basic injection amount is corrected based on the output value of the air-fuel ratio sensor 20 in order to perform feedback.

Next, the time is determined in step 707, and if the specified time has been reached, the idle speed control (ISC) is controlled in step 708, and then, in step 709, the integral control at the time of feedback in step 706 is performed. That is, control is performed to increase or decrease the injection amount at regular intervals.

After step 709 or if the specified time has not been reached in step 707, it is determined in step 710 whether the crank angle has reached a certain timing, and if so, the fuel injection amount is calculated in step 711. I do.

If the result in step 710 is negative, or after step 711, in step 712, the intake air amount G/N per intake obtained in step 704 and the engine rotation speed N[!] obtained in step 702 are determined. Tokara G/N and Nl! The lead angle value is determined using a map (not shown) in which the relationships between the two are associated in advance.

Next, in step 713, it is determined whether or not the injection timing is set, and if it is the injection timing, then in step 714, the attenuation of the increase in cold weather (warm-up increase, warm-up acceleration increase) calculated in step 705 is calculated.

When the result in step 713 is negative, or after step 714, the process returns to step 701. In the main routine described above, the part related to the present invention is the calculation step of the intake air amount Ga in step 703. As described above, the intake air amount is calculated based on the output value of the heat wire sensor 2, the throttle opening degree, and the rate of change thereof.

In the above embodiment, the intake air amount was smoothed by averaging the maximum and minimum values of the intake air amount in a predetermined number of interrupt routines, as explained with reference to FIG. The invention is not limited to this, but for example, the determination in step 512 in FIG.
If T, -β and GTA10β are outside the range, the amount of intake air taken in each of the predetermined number of interrupt routines is averaged instead of the maximum and minimum values of the amount of intake air. Good too.

〔Effect of the invention〕

As explained below, according to the present invention, by comparing the amount and direction of change in the throttle opening with the amount and direction of change in the intake air amount obtained from the output of the heat wire sensor, It is possible to accurately detect the pulsation of the air inside the engine, and the output of the heat wire sensor can be used to detect when air pulsation occurs, such as when the throttle opening is not changing, or when the amount of intake air changes due to noise. The output of the heat wire sensor is smoothed only when the air pulsation is negligible, and the output of the heat wire sensor is directly taken in without smoothing. This effectively prevents engine vibration and hunting from occurring.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing the configuration of the present invention, Fig. 2 is a system diagram of an electronically controlled fuel injection engine to which the present invention is applied, and Fig. 3 shows an example of the configuration of the control circuit shown in Fig. 2. Block diagram, Figure 4 is a flowchart showing the ADC interrupt routine for the output of the throttle position sensor, Figure 5 is a flowchart showing the AI'10 interrupt routine for the output of the heat wire sensor, and Figure 6 is a flowchart showing the ADC interrupt routine for the output of the heat wire sensor. 3 is a flowchart illustrating an example of steps of smoothing calculation. FIG. 7 is a flowchart showing the operation of the main processing routine program. 1-air cleaner, 2-heat wire sensor, 7--intake passage, 8--engine body, 9-combustion chamber, 13-piston, 18-throttle position sensor. Figure 7

Claims (1)

[Claims] 1. A heat wire sensor for detecting the amount of intake air installed in an intake passage of an internal combustion engine, and a rate of change in the output of the heat wire sensor that measures the amount of change in air in the intake passage per unit time based on the output of the heat wire sensor. a measuring means, a heat wire sensor output change direction determining means for determining whether the amount of air in the intake passage is decreasing or increasing based on the output of the heat wire sensor for each unit time, provided in the intake passage; a throttle position sensor that detects the opening degree of the throttle valve; output change rate measuring means for the throttle position sensor that measures the amount of change in the opening degree of the throttle valve per unit time based on the output of the throttle position sensor; Throttle position sensor output change direction determining means for determining whether the opening degree of the throttle valve is decreasing or increasing for each unit time based on the output of the throttle position sensor; and determining the output change direction of the heat wire sensor. The direction of change in the air amount obtained from the output of the means is different from the direction of change in the opening degree of the throttle valve obtained from the output of the output change direction determination means of the throttle position sensor, and the heat wire sensor The rate of change in the amount of air obtained from the output of the output change rate measuring means of the throttle position sensor is outside a predetermined tolerance range for the rate of change of the opening degree of the throttle valve obtained from the output of the output change rate measuring means of the throttle position sensor. 1. An output control device for a heat wire sensor, comprising: a heat wire sensor output smoothing unit that smoothes the output of the heat wire sensor only when the heat wire sensor output is smoothed.