JPS603534A - Method for measuring atmospheric pressure in internal- combustion engine - Google Patents

Abstract

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

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for measuring atmospheric pressure in an internal combustion engine.

For example, in a vehicle-mounted 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 achieve 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 a pressure sensor.

Incidentally, since the intake pipe pressure changes depending on the opening degree of the throttle valve, etc., it is necessary to constantly detect it for engine control purposes, but since the atmospheric pressure changes depending on the altitude of the place where the vehicle is traveling, it is not necessarily necessary to constantly detect it. However, pressure sensors are expensive. Therefore, methods of measuring atmospheric pressure without providing a special atmospheric pressure measurement sensor have been considered.

As such atmospheric pressure measurement methods, the following methods are conventionally known.

(1) The negative pressure passage provided between the pressure sensor downstream of the throttle valve for measuring the intake pipe pressure horn 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 closed. How to measure atmospheric pressure.

(Japanese Unexamined Patent Publication No. 57-32059) (2) Method a of measuring atmospheric pressure with a pressure sensor for measuring intake pipe pressure immediately after turning on the ignition switch and before cranking (Unexamined Japanese Patent Application No. 57-146030) (3) A method of supplying atmospheric pressure by stopping the supply of intake pipe pressure to the pressure sensor using a three-way switching valve only when the difference between the intake pipe pressure and atmospheric pressure is below a predetermined value. (Japanese Unexamined Patent Publication No. 57-104835) (4) A pressure sensor measures the magnitude of the pressure from the negative pressure detection hole on the inner wall of the intake pipe near the throttle valve, and outputs a signal from the pressure sensor before engine rotation and during idling. How to use atmospheric pressure information. (1) Munsho No. 55-154341) However, in the method of Section 2 (1), 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. There was a problem that the structure was complicated. Furthermore, even if the negative pressure passage to the pressure range υ 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 accurate detection of the intake pipe pressure is delayed, making it difficult to restart control after switching. There was also the problem of being guilty. In method (2) above, atmospheric pressure cannot be measured after the engine starts cranking, which is inconvenient when the magnitude of atmospheric pressure changes with changes in travel altitude, such as in a vehicle internal combustion engine. Above (3
) method, the area corresponding to fully opening the throttle valve is determined according to the difference between the intake pipe pressure and the atmospheric pressure, and based on this determination result, the three-way valve is opened in the same way as the method (1) above. Since the negative pressure passage to the pressure sensor is communicated with the atmosphere, the configuration of the intake system becomes complicated.

Furthermore, each of the above methods (1) to 4) has a problem in that the engine cannot be controlled in accordance with the intake pipe pressure while atmospheric pressure is being measured.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an atmospheric pressure measuring method which has an intermediate configuration and enables engine control according to intake pipe pressure even while atmospheric pressure is being measured.

The atmospheric pressure measurement method of the present invention is based on the pressure downstream of the throttle valve when the engine rotation speed is below a predetermined rotation speed and the throttle valve opening of the engine intake passage is above a predetermined opening. It is characterized by calculating the size of .

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

In an electronically controlled fuel supply system for an on-vehicle internal combustion engine to which an atmospheric pressure measuring method is applied as an embodiment of the present invention shown in FIG.
, is supplied to the engine 4 via the intake passage 3. A throttle valve 5 is provided in the intake passage 3, and the amount of air taken into the engine 4 changes according to the opening degree of the throttle valve 5. Further, a secondary air passage 6 is provided downstream of the air cleaner 2 and the throttle valve 5, bypassing the throttle valve 5, and a solenoid valve 7 for idle up is provided in the secondary air passage 6.

On the other hand, reference numeral 10 is a throttle opening sensor, which is, for example, a potentiometer, and generates an output voltage at a level corresponding to the opening degree of the throttle valve 5. Reference numeral 11 is a throttle opening sensor that is provided downstream of the throttle valve 5 and outputs an output voltage at a level corresponding to 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 engine 4; 13 is a sensor that generates a pulse signal when the crankshaft (not shown) of engine 4 is at a predetermined rotation angle; The generating crank angle sensor 14 is an oxygen concentration sensor provided in the exhaust passage 8 and generating an output voltage at a level corresponding to the oxygen concentration in the exhaust gas of the engine 4. Reference numeral 15 denotes an injector installed in the intake passage 3 near the intake valve (not shown) of the engine 4. The output terminals of the throttle opening sensor 10, absolute pressure sensor 1J-11, cooling water temperature sensor 12, crank angle sensor 16-3, and MN Fuchi sensor V14, and the input terminals of the solenoid valve 7 and injector 15 are connected to the control circuit. 16. Further, an ignition switch 17 and a starter switch 18 are connected to the control circuit 16, and when the ignition switch 17 is turned on, the power supply voltage is connected to the control circuit 1.
6, and the starter switch 18 is adapted to supply voltage to the control circuit 16 together with a starting motor (not shown) when turned on. Note that a three-way catalyst 9 is located downstream of the oxygen concentration sensor 14 in the exhaust path 8 of the engine 1.
is provided.

The control circuit 16 is configured 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 2o connected to the output of the smoothing circuit 19, a water temperature sensor 12, a throttle opening sensor 10. Absolute pressure sensor 11 and amplifier 2o
a level correction circuit 21 for correcting one novel of each output;
An input signal switching circuit 22 that selectively outputs one of the sensor outputs that have passed through the level correction circuit 21, and an A/D conversion that converts the analog signal output from the input signal switching circuit 22 into a digital signal. 23, a waveform shaping circuit 24 that shapes the waveform of the output of the crank angle sensor 13, a counter 25 that measures the time between pulses output from the waveform shaping circuit 2/l, and the ignition switch 17 and starter switch 18. A level correction circuit 26 that corrects the level of each output, a digital input module 27 that receives the output of this level correction circuit 26, and a drive circuit 28, 29 that drives the injector 15 and the solenoid valve 7, respectively.
It consists of a CPU 30, r<0M31 in which various processing programs are stored, and a RAM 32, an input signal switching circuit 22, an A/D converter 23, a counter 25, a digital input module 27, and drive circuits 28, 29. , C.P.
U 30, ROM 31 and RAM 32 are pass line 33
connected by.

In such a configuration, information on the throttle valve opening, intake pressure, cooling water temperature, and oxygen concentration is alternatively transmitted from the A/D converter 23, information on the engine rotation speed is alternatively transmitted from the counter 25, and information on the engine speed is alternatively transmitted from the digital input module 27. The on/off information of the ignition switch 17 and starter switch 18 is from C.
Each is supplied to the PU 30 via a pass line 33. C
The PU 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 . And the calculated fuel injection time (pu drive circuit 28
drives the injector 15 to supply fuel to the engine 4.

In addition, in the electronically controlled fuel supply system having the above configuration, since a pressure sensor dedicated to atmospheric pressure measurement is not installed, the atmospheric pressure is measured by the atmospheric pressure measuring method according to the present invention, and the idling time is determined according to the measurement result. Efforts are being made to maintain the engine rotational speed at a predetermined rotational speed even at high altitudes.

Next, the procedure of the atmospheric pressure measuring method according to the present invention, which is executed by the control circuit 16, will be explained according to the flowchart of FIG.

In this procedure, first, it is determined whether the starter switch 18 is on or not (step 1). If the starter switch 18 is off, it is determined whether the engine 4 is rotating (step 1). 52). The rotation of the engine 4 is stopped during JV, that is, the ignition switch 17
If it is immediately before or before the starter switch 18 is turned on, or immediately before restarting after the engine stalls, read the absolute pressure PRA obtained as the intake pipe pressure from the output voltage of the absolute pressure sensor 11. (Step 5
3). Then, the absolute pressure PBA is stored at a predetermined address as the atmospheric pressure PA (step 54).

On the other hand, when the starter switch 18 is on or when the engine 4 is in rotation, the engine speed N
It is determined whether or not o is below a predetermined rotation speed NPA (for example, 1800 rpm) (step 55). Ne≧NP
In the case of A, the time t P formed within CPtJ30
A I U ii All timer master 10-- The operation is started from a value (for example, O) (step 56).
). If Ne<NpA, it is determined whether the opening degree of the throttle valve 5 is greater than or equal to θPA (for example, 60 deo) (step 57); if θth≦θPA, the process moves to step 56). If θth>θPA, the count value of the timer is equal to the time t
Determine whether PAIU has passed (step 58)
. This determination is whether the engine speed Ne is below the predetermined speed NPA and whether the throttle valve opening θth is above the predetermined opening θPA? 9] continues for a time tpArull# to prevent malfunctions due to sudden changes in the absolute pressure P[3A. When the time tp8I LJ has elapsed, the correction value P[U is added to the absolute pressure PBA to obtain the atmospheric pressure PA (step 59). The absolute pressure PBA in step 59 is constantly detected because an absolute pressure detection routine (not shown) separate from this routine is executed in synchronization with the rotational operation of the engine 4. Further, the correction value Pru is set larger as the engine speed NO or the throttle valve opening θth increases due to pressure loss due to the air cleaner 2 and the intake passage 3. Next, the atmospheric pressure P determined in step 59
It is determined whether A is smaller than a predetermined pressure PPAILJ (eg, 700 mm1l>) (step 60).

If PA<PP^I LJ, for example, assuming that the vehicle is at a high altitude, the drive circuit 29 drives the electromagnetic valve 7 to open it (step 61). By opening the solenoid valve 7, secondary air is supplied downstream of the throttle valve 5 via the secondary air passage 6. When the atmospheric pressure is low, the air density is low and the amount of air supplied to the engine 4 decreases, which reduces the engine speed and causes engine stall when idling. Therefore, secondary air is supplied in this way. air m
The engine speed is maintained at a predetermined speed by increasing the amount of the engine.

Note that after the processing in step 56, if the time tpA+u has not elapsed in step 58 and if PA≧PpAIu in step 60, the CPU 30 processes another routine. Also, compared to the time t P A T LJ, the processing (timing) of the personal pressure measurement routine is a very short interval.

As described above, in the atmospheric pressure measurement method of the present invention, when the engine speed is below the predetermined speed and the throttle valve opening is above the predetermined opening, the intake pipe pressure becomes approximately equal to atmospheric pressure. Therefore, atmospheric pressure can be measured with high accuracy based on the intake pipe pressure at this time. Therefore, unlike the conventional atmospheric pressure measurement method, there is no need to use a three-way switching valve, and there is no need to change the configuration of the intake system, so atmospheric pressure can be measured with a simple configuration. Furthermore, since the atmospheric pressure can be measured while measuring the intake pipe pressure, it is possible to maintain engine control according to the intake pipe pressure while measuring the atmospheric pressure.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an electronically controlled fuel supply device to which the atmospheric pressure measuring method according to the present invention is applied, FIG. 2 is a specific block diagram of a control circuit in the device in FIG. 1, and FIG. 3 is a block diagram according to the present invention. FIG. 2 is an operation flow diagram of a control circuit showing a method for measuring atmospheric pressure. Explanation of symbols of main parts 2... Air cleaner 13- 3... Intake path 5... Throttle valve 6...
... Secondary air passage 7 ... Solenoid valve 8 ... Exhaust passage 9 ...
... Three-way catalyst 10 ... Throttle opening sensor 11 ...
・Absolute pressure sensor 12...Cooling water temperature sensor V 13...Crank angle sensor 14...Oxygen concentration sensor 15...Injector applicant Honda Motor Co., Ltd. Nei Agent Patent Attorney Motohiko Fujimura 111-

Claims (3)

[Claims] (1) Measure the downstream pressure of the throttle valve in the intake passage of the internal combustion engine, detect the operating state in which the engine speed is below a predetermined rotation speed and the throttle valve opening is above the predetermined opening, and A method for measuring atmospheric pressure in an internal combustion engine, characterized in that the magnitude of atmospheric pressure is calculated based on the magnitude of the downstream pressure of the throttle valve. (2) A patent characterized in that the magnitude of the atmospheric pressure is calculated when the engine speed is below a predetermined speed and the operating state at the throttle valve opening continues for a predetermined period of time. The atmospheric pressure measuring method according to claim 1. (3) The atmospheric pressure measuring method according to claim 1 or 2, characterized in that the magnitude of the atmospheric pressure is obtained by adding a predetermined value to the magnitude of the downstream pressure of the throttle valve. (/I) The atmospheric pressure measuring method according to claim 3, wherein the predetermined value is set according to either the engine speed or the throttle valve opening.