JPH04231651A - Intake-pipe interior pressure detector for internal combustion engine - Google Patents

Abstract

PURPOSE:To correct the error in the detected value of an intake-pipe interior pressure sensor, on the basis of the detected value of an atmospheric pressure sensor. CONSTITUTION:Determination is made of a deviation-P between the detected value PA of an atmospheric pressure sensor 8 and the detected value PB of an intake-pipe interior pressure sensor 7 obtained during a time period from the turning-on of an ignition switch to the commencement of revolution of an engine 1. Calculation is made of a correction value P1 with respect to the detected value PB in accordance with the deviation P. Only when the difference between the presently determined deviation P and the previously detected deviation P0 is equal to or lower than a prescribed value the correction value P1 is renewed.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an intake pipe internal pressure detection device for detecting the internal pressure of an intake pipe downstream of a throttle valve of an internal combustion engine.

0002

2. Description of the Related Art Conventionally, it is known that an EFI type internal combustion engine is provided with a pressure sensor that detects the internal pressure of an intake pipe downstream of a throttle valve, and controls the amount of fuel injection to increase or decrease according to the detected value of the sensor. Furthermore, there is also a system in which the intake pipe internal pressure detected by the sensor from the time the ignition switch is turned on until the engine starts rotating is taken as atmospheric pressure, and the fuel injection amount is corrected according to the atmospheric pressure. 58-6595
This method is known from Japanese Patent Publication No. 0 and Japanese Unexamined Patent Publication No. 133433/1983.

0003

[Problems to be Solved by the Invention] Since the pressure sensor for detecting the internal pressure of the intake pipe is installed in the engine room, the detection characteristics change due to the influence of heat, and furthermore, the pulsation of the internal pressure of the intake pipe causes damage to the diaphragm, etc. The detecting section of the sensor is constantly vibrated and tends to mechanically deteriorate, which tends to cause errors in the detected values of the sensor.

By the way, atmospheric pressure may fluctuate due to changes in weather or altitude while the vehicle is running, and in order to detect this fluctuation, it is desirable to provide a separate pressure sensor for detecting atmospheric pressure.

SUMMARY OF THE INVENTION An object of the present invention is to provide a device that can correct deviations in the detection value of an intake pipe internal pressure sensor based on the detection value of a separately provided atmospheric pressure sensor.

[0006]

[Means for solving the problem] In order to achieve the above purpose,
The present invention includes an intake pipe internal pressure sensor that detects the internal pressure of an intake pipe downstream of a throttle valve of an internal combustion engine, and an atmospheric pressure sensor that detects atmospheric pressure, and detects when the engine is in a predetermined state. The present invention is characterized in that it includes means for comparing the detected value with the detected value of the atmospheric pressure sensor, and means that calculates a correction value for the detected value of the intake pipe internal pressure sensor based on the comparison result.

[0007]

[Operation] Atmospheric pressure does not undergo sudden changes like the intake pipe internal pressure, so mechanical deterioration of the detection part of the atmospheric pressure sensor is less likely to occur, and the atmospheric pressure sensor is also susceptible to the effects of heat away from the engine room. Therefore, the detected value of the atmospheric pressure sensor is highly reliable, and even when the engine is stopped or the throttle is fully open, the detected value of the atmospheric pressure sensor and the intake pipe internal pressure sensor are highly reliable. When the detected value is different from the detected value, it can be determined that the detected value of the intake pipe internal pressure sensor is incorrect. Therefore, for example, by comparing the detection values of the atmospheric pressure sensor and the intake pipe internal pressure sensor, which are detected when the engine is stopped from when the ignition switch is turned on until the engine starts rotating, it is possible to determine whether the two detection values are different. In this case, by calculating a correction value according to the deviation, the deviation in the detected value of the intake pipe internal pressure sensor can be corrected.

By the way, the output characteristics of the atmospheric pressure sensor and the intake pipe internal pressure sensor with respect to changes in atmospheric pressure may differ from each other, and the atmospheric pressure may change due to changes in the weather, etc. between the previous deviation detection and the current deviation detection. Then, even though the sensors are not abnormal, the deviation of the detected values of both sensors may be different between the previous time and this time. On the other hand, when the detected value of the intake pipe internal pressure sensor does not deviate significantly at once, and the difference between the previous detected value of both sensors and the current detected value of both sensors is greater than a predetermined value. It is desirable to prevent calculation of an erroneous correction value by determining that the change is due to a change in atmospheric pressure and prohibiting calculation of the correction value described above.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, reference numeral 1 designates an engine, in which an intake pipe 3 connected to an air cleaner 2 is provided with a throttle valve 4 and a fuel injection nozzle 5 downstream thereof. The amount of fuel injected from the nozzle 5 is controlled. The control circuit 6 receives an output signal from an intake pipe internal pressure sensor 7 that detects the internal pressure of the intake pipe 3 downstream of the throttle valve 4, an output signal from an atmospheric pressure sensor 8 that detects atmospheric pressure, and an engine crank. An output signal from a crank sensor 9 that detects rotation of the shaft and output signals from other sensors (not shown) such as an engine rotation speed sensor and a water temperature sensor necessary for calculating the fuel injection amount are input. The atmospheric pressure sensor 8 is provided, for example, in a control box housing the control circuit 6 so as not to be affected by heat.

If the detected value of the intake pipe internal pressure sensor 7 goes out of order, it becomes impossible to properly control the fuel injection amount, and therefore the control circuit 6
The error in the detection value of the sensor 7 is corrected based on the detection value of the atmospheric pressure sensor 8, and the value obtained by adding a correction value ΔP1, which will be described later, to the detection value of the sensor 7 is used as the intake pipe internal pressure to control the fuel injection amount. I decided to do it. The program for this correction is shown in FIG. 2, and will be described in detail below.

[0011] In this program, a first flag F1 (processed 1, unprocessed 0) indicating whether the correction process has been completed or not, and whether the detection values of the intake pipe internal pressure sensor 7 and the atmospheric pressure sensor 8 have been read or not is set. A second flag F2 (read 1, before read 0) represents the second flag F2 (read 1, before read 0), and a third flag F3 (after input 1, 0 before input) are used. When the ignition switch is turned on, first the first flag F1 is checked in step S1, but since F1 is initially set to 0, the process proceeds to step S2 and checks whether the remaining time t of the subtractive timer is 0 or not. Determine. Initially, t is set to a predetermined set time t1 determined according to the time required for the sensor output to stabilize after the ignition switch is turned on and each sensor 7, 8 is energized, and when the set time t1 has elapsed, S3
Proceed to step 2 and look at the second flag F2. Before reading the sensor detection value, F2 = 0, and the process proceeds to step S4, where the detection value PB of the intake pipe internal pressure sensor 7 and the detection value PA of the atmospheric pressure sensor 8 are read, and then in the step S5, PA and P are read.
Find the deviation ΔP of B. Note that both PB and PA are detected as absolute pressures, and ΔP can be either positive or negative. After that, S6
In the step, ΔP is the predetermined limit value ΔPM on the positive side and negative side, which is the criterion for determining sensor abnormality or computer abnormality.
It is determined whether or not it is within the range of H, ΔPML, and if it is within the range, the second flag F is rewritten to 1 in step S7, and the remaining time t of the timer is set to the second set time t2 in step S8. set, and one determination process is completed.

Next time, the process proceeds from step S1 through steps S2 and S3 to step S9, and the third flag F3 is
I see. When F3=0, that is, from when the ignition switch is turned on until the engine starts rotating, proceed to step S10, and calculate the ΔP obtained in step S5 and the point stored in the backup RAM. The difference ΔPX from the calculated correction value ΔP1 is determined, and then in step S11, it is determined whether ΔPX is within the range of the positive and negative limit values ΔPXH and ΔPXL of the predetermined correction update width, and it is determined whether ΔPX is within the range. If so, proceed directly to step S13, and if outside the range, go to step S12 and change ΔPX to ΔPXH(ΔPX
>ΔPXH) or ΔPXL (in the case of ΔPX<ΔPXH) and proceeds to step S13. In step S13, ΔPX determines positive and negative limit values ΔPSH, which serve as criteria for determining whether or not to perform a predetermined correction update.
It is determined whether or not it is within the range of ΔPSL. ΔPSH, ΔPS
L is set so that ΔPXL<ΔPSL<ΔPSH<ΔPXH, and ΔPSL≦ΔPX≦ΔPSH occurs when ΔP≒ΔP1, that is, when an appropriate correction value has already been calculated. The process proceeds to S17 without updating the correction value ΔP1, the first flag F1 is rewritten to 1, and the determination process is ended. ΔPX>ΔPSH or ΔPX<ΔP
If it is SL, the process proceeds to step S14, where the deviation ΔPO of the detection values of both sensors 7 and 8 detected when the ignition switch was turned on last time is compared with the current deviation ΔP, and the A/P of the signals of both sensors 7 and 8 is calculated. Considering the variation of D conversion, ΔP
When ≒ΔPO, proceed to step S15 and set the correction value Δ
Update P1 to the value obtained by adding ΔPX to the previous correction value ΔP1,
On the other hand, if ΔP is significantly different from ΔPO, it is determined that the change in ΔP is due to the change in atmospheric pressure between the previous and current times due to the difference in the output characteristics of both sensors 7 and 8, and the process proceeds to step S16 to change ΔPO to ΔP. , and the process proceeds to step S17 to end the determination process without updating the correction value ΔP1. Therefore, the correction value ΔP1 will not be updated unless ΔP becomes the same value twice in a row when the ignition is turned on last time and when the ignition is turned on this time, and an incorrect correction value may be calculated due to fluctuations in ΔP due to changes in atmospheric pressure. There isn't.

[0013] When the first flag F1 is rewritten to 1 in step S17, from the next time onwards, "NO" will be written in step S1.
”, and the determination process ends without proceeding to the next step. Furthermore, until the first set time t1 has elapsed after the ignition switch is turned on, the determination process ends with a "NO" determination in step S2, and at the time t1 elapses, both sensors 7 and 8 are activated as described above. The detected values PB and PA are read. t1 is set to be shorter than the normal time lag required from when the ignition switch is turned on until the engine starts rotating, but if the engine starts rotating before t1 elapses, the reading of PB and PA and Δ
Even if P is calculated, the next time the process proceeds to step S9, it is determined to be "ON" and the process directly proceeds to step S17, and ΔP1 is not updated. Therefore, calculation of an erroneous correction value based on PB and PA in a state where the intake pipe internal pressure becomes a value different from atmospheric pressure after the engine starts rotating is prevented. Furthermore, if ΔP becomes an abnormal value due to sensor abnormality or computer abnormality, etc., step S1 can be executed directly from step S6.
Proceed to step 7. Also, if ΔPX temporarily increases for some reason, updating the correction value ΔP1 with this value may have an adverse effect on fuel injection control, but S
By providing 12 steps, the update width of the correction value is limited to a predetermined limit value or less, and the correction value is updated in stages, so that the above-mentioned problem does not occur.

[0014]

As is clear from the above explanation, according to the present invention, even if the detected value of the intake pipe internal pressure sensor deviates, this deviation can be corrected based on the detected value of the atmospheric pressure sensor. If the internal pressure of the pipe can be detected accurately, and the deviation between the detected values of both sensors this time has changed significantly due to changes in atmospheric pressure compared to the previous deviation of the detected values of both sensors, the correction value will be updated. Therefore, calculation of incorrect correction values can be prevented.

[Brief explanation of the drawing]

[Fig. 1] Block diagram of an example of the device of the present invention

[Figure 2] Flowchart showing a sensor detection value correction program

[Explanation of symbols]

1 engine 3 intake pipe
4 Throttle valve 6 Control circuit
7 Intake pipe internal pressure sensor 8 Atmospheric pressure sensor 9 Crank sensor

Claims (4)

[Claims] 1. An intake pipe internal pressure sensor that detects the internal pressure of an intake pipe downstream of a throttle valve of an internal combustion engine, and an atmospheric pressure sensor that detects atmospheric pressure. Inside an intake pipe of an internal combustion engine, comprising means for comparing a detected value with a detected value of an atmospheric pressure sensor, and means for calculating a correction value for the detected value of the intake pipe internal pressure sensor based on the comparison result. Pressure detection device. 2. An intake pipe internal pressure of an internal combustion engine according to claim 1, wherein the predetermined state of the engine is a state from when an ignition switch is turned on until the engine starts rotating. Detection device. 3. The intake pipe internal pressure detection device for an internal combustion engine according to claim 1, wherein the correction value is calculated according to a deviation between detected values between an atmospheric pressure sensor and an intake pipe internal pressure sensor. 4. Find the difference between the previously detected deviation of the detected values of the atmospheric pressure sensor and the intake pipe internal pressure sensor and the currently detected deviation of the detected values of both sensors, and determine whether the difference is greater than or equal to a predetermined value. 4. The intake pipe internal pressure detection device for an internal combustion engine according to claim 3, further comprising means for prohibiting calculation of the correction value in the case of .