JPS61207857A - Correcting method of detection value of intake pipe pressure in internal-combustion engine - Google Patents

Abstract

PURPOSE:To prevent sir-fuel ratio from becoming rich in an engine in its highland operation and reduce exhaust emission of CO, HC, by correcting a detection value of intake pipe pressure on the basis of a level of the intake pipe pressure in the downstream of a throttle valve in a specific operational condition. CONSTITUTION:The method decides whether or not absolute pressure PBA obtained as the pressure of an intake pipe 3 is higher than PB1 (high load), that is, whether or not an engine is in high load operation. And in an operational condition of the engine with a high load further with a throttle valve 5 full open, the absolute pressure PBA is corrected in accordance with a change of the atmospheric pressure on the basis of output voltage PBX of an absolute pressure sensor 11. In this way, the method prevents air-fuel ratio from becoming rich in the engine in its highland operation and reduces exhaust emission of CO, HC.

Description

TECHNICAL FIELD The present invention relates to a method for correcting a detected intake pipe pressure value in an internal combustion engine.

1. For example, in a vehicle internal combustion engine, engine control is performed based on various engine parameters in order to reduce harmful components in exhaust gas, reduce fuel consumption, and provide comfortable driving.

Engine parameters related to pressure include atmospheric pressure and negative pressure downstream of a throttle valve in an intake passage (so-called intake pipe pressure), and these pressures are detected by respective pressure sensors.

By the way, intake pipe pressure is an engine parameter that changes depending on the opening degree of the throttle valve, etc., so it must be constantly detected in order to control the engine, whereas atmospheric pressure is an engine parameter that changes depending on the altitude of the driving area. Therefore, it is not necessarily necessary to detect it all the time. Moreover, since pressure sensors are expensive, various methods have been considered for measuring atmospheric pressure without providing a special sensor for measuring atmospheric pressure.

Conventionally, the following methods have been proposed as methods for correcting the detected intake pipe pressure value.

(1) The negative pressure passage provided between the downstream side of the throttle valve and the pressure sensor for measuring intake pipe pressure is opened to the atmosphere when the throttle valve is fully open, or only when the throttle valve is fully open, and the negative pressure passage downstream of the throttle valve is opened to the atmosphere. Method of measuring atmospheric pressure by blocking
(See Publication No. 9).

(2) A method of measuring atmospheric pressure with a pressure sensor for measuring intake pipe pressure immediately after turning on the ignition switch and before cranking (see Japanese Patent Laid-Open No. 146030/1983).

(3) A method of measuring by stopping the supply of intake pipe pressure to the pressure sensor and supplying atmospheric pressure using a three-way switching valve only when the difference between the intake pipe pressure and atmospheric pressure is below a predetermined value (
(See Japanese Patent Application Laid-open No. 57-104835).

(4) A method in which the magnitude of the pressure from the negative pressure detection hole on the inner wall of the intake pipe near the throttle valve is measured with a pressure sensor, and the output signal of the pressure sensor before engine rotation and during idling is used as atmospheric pressure information (special method) (Refer to Japanese Patent Publication No. 154341/1983).

However, method (1) above has the problem that a three-way switching valve is required to switch the negative pressure passage to the pressure sensor between the atmosphere side and the downstream side of the throttle valve, which complicates the structure of the intake system. . In addition, even if the negative pressure passage to the pressure sensor is connected to the downstream side of the throttle valve, the pressure in the negative pressure passage does not immediately become equal to the intake pipe pressure, and it takes time to detect accurate intake pipe pressure, so switching is necessary. There was also the problem that the resumption of control later was delayed.With method (2) above, atmospheric pressure cannot be measured after the engine starts cranking, so unlike in-vehicle internal combustion engines, changes in running altitude can cause This is inconvenient when the magnitude of the atmospheric pressure changes.In the method (3) above, the region corresponding to the throttle valve being fully opened is determined according to the magnitude of the difference between the intake pipe pressure and the atmospheric pressure. , according to this discrimination result (1) above.
Similar to the method described above, a three-way switching valve is used to connect the negative pressure passage to the pressure sensor with the atmosphere, which poses the problem of complicating the structure of the intake system. Further, each of the methods (1) to 4) in -h has a problem in that the engine cannot be controlled in accordance with the intake pipe pressure while the atmospheric pressure is being measured.

In addition, pressure sensors measure pressure based on the pressure difference between the vacuum chamber and the measurement part, but when moving a vehicle, there is a difference in altitude depending on the position, and that difference in altitude causes a change in atmospheric pressure. Therefore, measuring the intake pipe internal pressure as an absolute pressure and directly controlling it with a device may cause problems at high altitudes, such as determining that the throttle valve is in a partial region, even though the throttle valve is originally fully open.

SUMMARY OF THE INVENTION The present invention has been made to eliminate the drawbacks of the above-mentioned conventional devices.It has a simple configuration and enables engine control according to intake pipe pressure even while atmospheric pressure is being measured. It is an object of the present invention to provide a method for correcting a detected intake pipe pressure value, which makes it possible to correct the detected intake pipe pressure value in accordance with changes.

The intake pipe pressure detection value correction method according to the present invention is based on the magnitude of the throttle valve downstream pressure in a predetermined operating state set by the gear shift position of the transmission and the engine speed. Setting a pipe pressure value and correcting the intake pipe pressure detection value based on the magnitude of the downstream pressure of the throttle valve when the system is in an operating state in which the pressure change amount continues to be above this pressure value and below a certain value for a predetermined period of time. It is characterized by

The method for correcting the intake pipe pressure detection value according to the present invention further includes the method of correcting the intake pipe pressure when the throttle valve is in a predetermined operating range set by the gear shift position of the transmission and the engine rotational speed and in an operating state in which the rate of change of the operating parameter is equal to or higher than the predetermined value. The intake pipe pressure value for high load judgment is set based on the magnitude of the valve downstream pressure, and the throttle valve downstream pressure when the operating state is such that the pressure is above this pressure value and the amount of pressure change is below a certain value for a predetermined period of time. The intake pipe pressure detection value is corrected based on the magnitude of the intake pipe pressure.

Example Embodiments of the present invention will be described below with reference to the drawings.

In the electronically controlled fuel supply system for an on-vehicle internal combustion engine to which the intake pipe pressure detection value correction method according to the present invention is applied, as shown in FIG. It is designed to be supplied to engine 4. A throttle valve 5 is provided in the intake passage 3 so that the intake air to the engine 4 changes depending on the opening degree of the throttle valve 5. Further, a secondary air passage 6 is provided that bypasses the throttle valve 5 and communicates with the intake passage 3 from the air cleaner 2 downstream of the throttle valve 5. is provided.

Reference numeral 10 is, for example, a potentiometer, which is a throttle opening sensor that operates in conjunction with the throttle valve 5 to generate an output voltage at a level corresponding to the opening of the throttle valve 5. Reference numeral 11 is provided downstream of the throttle valve 5 to detect the magnitude of the pressure. 12 is a cooling water temperature sensor that generates an output voltage at a level corresponding to the cooling water temperature of the engine 4;
3 is a crank angle sensor that generates a pulse signal when the crankshaft (not shown) of the engine 4 is at a predetermined rotation angle;
Reference numeral 14 denotes an oxygen concentration sensor that is provided in the exhaust passage 8 and generates an output voltage at a level corresponding to the oxygen concentration in the exhaust gas of the engine 4. 15 is an intake valve of engine 4 (not shown)
This is an injector installed in the nearby intake path 3. Throttle opening sensor 10, absolute pressure sensor 11, cooling water temperature sensor 12, crank angle sensor 13, and oxygen concentration sensor 1
4 are supplied to a control circuit 16, and the solenoid valve 7 and the injector 15 are driven and controlled by the control circuit 16. Further, the control circuit 16 is supplied with a vehicle speed pulse having a pulse width proportional to the vehicle speed from the vehicle speed sensor 17 .

Note that a three-way catalyst 9 is provided downstream of the oxygen concentration sensor 14 in the exhaust gas passage 8 of the engine 4 .

The control circuit 16 includes a capacitor C+ as shown in FIG.
, C2 and a resistor R, a smoothing circuit 19 smoothing the output voltage of the oxygen concentration sensor 14, a buffer amplifier 20 connected to the output of the smoothing circuit 19, a water temperature sensor 12, a throttle opening sensor 10, and an absolute pressure sensor 11. , a level correction circuit 21 that corrects the level of each output of the vehicle speed sensor 17 and the amplifier 20, and an input signal switching circuit 2 that selectively outputs one of the outputs of each sensor that has passed through the level correction circuit 21.
2, an A/D converter 23 that converts the analog signal output from the input signal switching circuit 22 into a digital signal, a waveform shaping circuit 24 that shapes the waveform of the output of the crank angle sensor 13, and this waveform shaping circuit. A counter 25 that measures the time between pulses output from 24, drive circuits 28 and 29 that drive the injector 15 and solenoid valve 7, respectively, a CPU 30, and an R in which various processing programs are stored.
It consists of an OM 31 and a RAM 32, and the input signal switching circuit 22, A/D converter 23, counter 25, drive circuits 28, 29, CPU 30, ROM 31, and RAM 32 are connected by a pass line 33.

In such a configuration, information on the throttle valve opening, intake pressure, cooling water temperature, vehicle speed, and oxygen concentration is alternatively sent from the A/D converter 23, and information on the engine rotation speed, etc. is sent to the CPU 30 as a pass line from the counter 25. 33, respectively.

The CPU 30 reads each of the above information according to the calculation program stored in advance in the ROM 31, and based on the information, calculates the fuel supply from a predetermined calculation formula at each predetermined revolution of the engine 4 or at each sampling timing determined by a predetermined clock pulse. Calculate the fuel injection time corresponding to the feed amount. Then, the drive circuit 28
drives the injector 15 to supply fuel to the engine 4.

Further, in the electronically controlled fuel supply device having the above-mentioned configuration, since a pressure sensor dedicated to atmospheric pressure measurement is not provided, atmospheric pressure is measured by the atmospheric pressure measuring method of this embodiment, and the atmospheric pressure is measured by the atmospheric pressure measuring method of this embodiment. The intake pipe pressure detection value correction method corrects the intake pipe pressure detection value in accordance with changes in atmospheric pressure.

That is, in the atmospheric pressure measuring method in this embodiment, the operating state in which the throttle valve 5 is near the fully open region is detected based on the gear shift position of the transmission (not shown) and the engine speed, and this operating state is detected. Since the intake pipe pressure is approximately equal to atmospheric pressure, the atmospheric pressure is measured by calculating the atmospheric pressure using the intake pipe pressure at this time.

Note that the engine rotation speed can be determined based on the pulse width of the output pulse of the counter 25, and the vehicle speed sensor 1
The gear shift position can be determined based on a certain width by determining the ratio of the engine rotation speed to the vehicle speed determined based on the pulse width of the vehicle speed pulse from 7.

In the electronically controlled fuel supply system, the air-fuel ratio is corrected by correcting, for example, the fuel injection amount and the secondary air amount based on the atmospheric pressure value measured as described above. .

Next, the procedures of the atmospheric pressure measurement method and the intake pipe pressure detection value correction method executed by the control circuit 16 will be explained according to the flowcharts of FIGS. 3 to 5.

In this procedure, first, it is determined whether the gear shift position is 1st gear (step 1), and if it is 1st gear, it is determined whether the engine rotation speed Ne is 4000 rpm or more (step 2). ). Here, since 1st gear is a starting shift, even if the throttle valve 5 is opened, the intake pipe pressure does not reach the absolute negative pressure near the fully open position. I am doing it.

If it is 4000 rpm or more, it is determined that the throttle valve 5 is in an operating state near the full range, and the absolute pressure PBA obtained as the intake pipe pressure from the output voltage of the absolute pressure sensor 11 is +500111-1<1. or more (intake pipe negative pressure is 2
60+++ mHg or less) (step 3). This determination step 3 is provided in order to prevent a malfunction in which the highest road altitude in Japan is set at 3000 m and a correction higher than that is made. In step 4), it is determined whether or not the above condition continues for more than 2 seconds, and if it continues, it is determined that the correction mode is definitely in effect, and the absolute The flow advances to a subroutine (step 20) for correcting pressure.

If it is determined in step 1 that the gear shift position is not 1st gear, then it is determined whether the gear shift position is 2nd or 3rd gear (step 5), and if it is 2nd or 3rd gear, the engine rotational speed Ne It is determined whether or not the speed is 2500 rpm or more (step 6). Here, in 2nd or 3rd gear, the negative pressure in the intake pipe is generally low (high in absolute pressure) due to an acceleration shift, so the engine speed Ne is determined at a low 250.
This is done at 0 rpm or higher. If it is 250 Orpm or more, it is determined that the throttle valve 5 is in an operating state near the fully open region, and the process moves to step 3.

If it is determined in step 5 that the gear shift position is not 2nd or 3rd, then it is determined whether the gear shift position is 4th or 5th (step 7); if it is 4th or 5th, It is determined whether the engine rotation speed NO is 2600 rpm or more (step 8). 4th or 5th speed is
Generally, since it is a cruise shift, the engine rotation speed is 2600 rpm or higher, which is slightly higher than highway cruise driving, as a criterion for determination. Here, when the gear shift position is in the neutral position, the engine rotation speed Ne such as snap
Since the absolute pressure PBΔ does not increase, atmospheric correction is not performed.

For 4th or 5th gear, engine speed Ne is 260
If it is determined that it is 0 rpn+ or more, an acceleration determination (ΔV>1.0), which is one of the operating parameters, is also performed (step 9). This is because the absolute pressure PBA during cruise driving is low, so unless it is determined that there is a certain degree of acceleration, the pressure in the intake pipe will be lower than the throttle valve 5.
This is because the absolute pressure PBA does not reach near the fully open position. When the number is in the acceleration state, it is determined that the throttle valve 5 is in the operating state in the vicinity of the fully open region, and the process moves to step 3.

Regarding 2nd or 3rd gear, Δ■ is not determined because there is little change in vehicle speed when driving uphill by downshifting and keeping the vehicle speed constant, but even if ΔV is determined, atmospheric correction There is no particular problem as long as the frequency of routine operation is reduced.

If a negative determination is made in steps 2 to 4 and 6 to 9, and the flow does not proceed to the Pa1 determination correction subroutine, the determination flag indicating whether or not to perform Pe+ correction is set to 1.
10 II (step 10).

In the above main routine, by setting the value of the judgment engine rotation speed Ne in 1st gear to be larger than the value of the judgment engine rotation speed Ne in 2nd and 3rd gears, it is possible to immediately Therefore, it is possible to accurately determine the region where the absolute pressure PEA is close to atmospheric pressure. Also, especially when cruising at a high shift position (for example, 5th gear), the absolute pressure P8
Since ^ becomes low, it is possible to detect the atmospheric pressure from the output voltage of the absolute pressure sensor 11 by utilizing the fact that the absolute pressure P8A becomes close to the atmospheric pressure during a transient state in which the rate of change of operating parameters is large, for example during acceleration. It can be done.

Next, a subroutine (step 20) for correcting the absolute pressure for determining Psi (high load) will be explained according to the flowchart of FIG.

First, it is determined whether the Pet correction flag is 1" or "O" (step 21). When the Pa+ correction flag starts from the flow of the previous flow and flows to the subroutine, the flag is 0'' due to the flow of the previous flow, so it flows to the right and +600m1H is stored in RAM32 called PsoHAX.
g (absolute pressure) and initialize it (Step 2
2). Then, the Pa+ correction flag is changed from "0" to "1" (step 23), and the process returns to the main routine, but returns to the Pe+ correction subroutine again in a short time (100 mm 5 ec or less).

When you return to the Pe+ correction subroutine again, P
Since the e+ correction flag is 1'', the flow flows downward from step 21, and the current absolute pressure PEA is Pao
It is determined whether it is higher than HAX (step 24). If it is higher than PeoHAX (the opening degree of throttle valve 5 is large and the load is large), Pa o HAX = +50011
The value of the current absolute pressure PEA is replaced with that of HO (step 25). For example, the current absolute pressure PBA
If is +600m1H (l, then Pa o HAX
−+ 500mmHg Pa o HAX = + 6
Change to 00118O. And ^ Psi for load determination
The value of is set to a value obtained by subtracting, for example, 501m)-1(] from PsoHAX (step 26).

This completes the change of the Ps+ set value, but the feature of the above flow is that the Pa + iiQ constant value is set to a value obtained by subtracting 50 mmHa from the highest pressure in the Pat determination correction mode. According to this, when high load is determined based on absolute pressure PBA, pressure equal to or higher than Pe+set value is determined to be high load, and □Pa+Psi or lower is determined to be low load, and at high altitudes, the throttle valve 5 Even if the engine is fully opened, the problem of not being able to determine a high load due to the low absolute pressure does not occur.

When the change in Ps+ set value is completed, the process moves to step 30, and the absolute pressure P8A (intake pipe pressure detection value) is corrected in accordance with the change in atmospheric pressure. The subroutine (step 30) for performing this atmospheric pressure correction will be described below in accordance with the flowchart of FIG.

First, in step 31, it is determined whether the absolute pressure Ps A 7/IPe + is higher, that is, whether the load is high or not.
), when the load is high, the change in absolute pressure P8^ RΔP
It is determined whether BA is less than a certain value, for example 10m1Ha (step 32), and if it is less than 10111111Ha, then it is determined whether the condition has continued for more than 3 seconds, for example (step 33).

When ΔPBA remains below iQmml-IQ for 3 seconds or more, it generally means that the throttle valve 5 is fully open.

Under the above conditions, that is, in an operating state where the load is high and the throttle valve 5 is fully open, first read the output voltage Psx of the absolute pressure sensor 11 in that operating state, and change the atmospheric pressure based on the output voltage Psx. The absolute pressure PBA is corrected according to (step 34). Atmospheric pressure correction is Ps^-=P8 A + (760-(Pa x +A
)) is carried out based on the formula. In the above formula,
Pa^' is the absolute pressure corrected to the atmospheric pressure, A is the correction pressure value that changes slightly depending on the engine speed when the throttle valve 5 is fully open as shown in Fig. 6, and 760 is the atmospheric pressure (+mHg) on flat ground. . Note that when this subroutine is not executed, correction is performed using the Fax value when the subroutine was executed last time.

With this, the correction of the absolute pressure PBA according to the change in atmospheric pressure is completed.

Effects of the Invention As described above, in the intake pipe pressure detection value correction method according to the present invention, the absolute Since the pressure PBA is corrected, it is possible to prevent the air-fuel ratio from becoming rich at high altitudes, and it is possible to reduce CO1HC emissions. In addition, Pe+ for high load judgment
can be corrected with atmospheric pressure, and especially in a system that performs feedback control of the air-fuel ratio using the output voltage of the oxygen temperature sensor 14, the feedback flI
It is possible to accurately determine the conditions for stopping Il, and it is possible to purify exhaust gas at high altitudes and improve drivability under load.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an electronically controlled fuel supply system to which the method of correcting the detected intake pipe pressure value according to the present invention is applied;
Figure 1 is a block diagram showing the specific configuration of the control circuit in the device shown in Figure 1, Figures 3 to 5 are flowcharts showing the steps of the method for correcting the detected intake pipe pressure value according to the present invention, and Figure 6 is the aperture diaphragm. FIG. 3 is a characteristic diagram showing the relationship between engine speed and pressure when the valve is fully open. Explanation of symbols of main parts 2... Air cleaner 3... Intake passage 5... Throttle valve 6... Secondary air passage 7... Solenoid valve 8... Exhaust path 9... Three-way catalyst 10... Throttle opening sensor 11...
・Absolute pressure sensor 12... Cooling water temperature sensor 13... Crank angle sensor 14... Oxygen concentration sensor 15... Injector 17... Speed Senri Applicant Honda Motor Co., Ltd. Agent Patent Attorney Motohiko Fujimura Ice 4 Concave Figure 5 #-, Raguchi Sanshirin Reli Urada (in)

Claims (4)

[Claims] (1) Detect the intake pipe pressure downstream of the throttle valve in the intake path of the internal combustion engine, detect a predetermined operating state set by the gear shift position of the transmission and the engine speed, and detect the pressure downstream of the throttle valve at the time of detection. An intake pipe pressure value for high load determination is set based on the magnitude of the intake pipe pressure, and an operating state in which the internal combustion engine continues to have a pressure equal to or higher than the intake pipe pressure value and a pressure change amount equal to or less than a certain value for a predetermined period of time is detected. A method for correcting a detected intake pipe pressure value, characterized in that the detected value of the intake pipe pressure is corrected based on the magnitude of the intake pipe pressure downstream of the throttle valve at the time of the detection. (2) The engine rotation speed for detecting the predetermined operating state is set to be smaller as the gear shift position becomes higher. Correction method. (3) Detect the intake pipe pressure downstream of the throttle valve in the intake path of the internal combustion engine, and operate within a predetermined operating range set by the gear shift position of the transmission and engine speed, and where the rate of change of operating parameters is greater than a predetermined value. detecting the state, and setting an intake pipe pressure value for high load determination based on the magnitude of the intake pipe pressure downstream of the throttle valve at the time of detection; An intake pipe characterized in that an operating state in which the amount continues to be below a certain value for a predetermined period of time is detected, and the detected value of the intake pipe pressure is corrected based on the magnitude of the intake pipe pressure downstream of the throttle valve at the time of detection. How to correct pressure detection value. (4) Correction of the detected intake pipe pressure value according to claim 3, wherein the engine rotation speed for detecting the operating state is set to be smaller as the gear shift position becomes higher. Method.