JPS6098329A - Pressure detector of internal-combustion engine - Google Patents

Abstract

PURPOSE:To reduce the cost without damaging the detection precision by operating an air pressure in accordance with the output of a pressure detecting means, which detects the pressure in an intake pipe, and the output of a full opening detecting means which detects that an intake throttle valve is opened to its full width approximately. CONSTITUTION:The full opening detecting means detects it on a basis of a degree of opening of the intake throttle valve or the like that the operation state of an engine is full opening approximately. When it is detected by the full opening detecting means that the engine is operated in the full opening state approximately, an air pressure operating means operates the air pressure on a basis of the output of the pressure detecting means which detects the pressure in the intake pipe. The output of this operating means and the output of the pressure detecting means are supplied to an engine control means.

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to a method for measuring atmospheric pressure and suction negative pressure, which is used to obtain an air flow signal that is an index for controlling the air-fuel ratio, ignition timing, etc. of an electronically controlled internal combustion engine. It relates to a device for detecting.

<Prior art> As a conventional pressure detection device for an internal combustion engine, for example, a first
There is something like the one shown in the figure. This supplies the outputs of an intake negative pressure sensor l that detects the pressure inside the intake pipe, an atmospheric pressure sensor 2 that detects atmospheric pressure, and a rotation sensor (not shown) that detects the rotational speed of the engine to the calculation device 3. The intake air flow rate of the engine was calculated and corrected, and the output of this calculation device 3 was output to the engine control circuit 4 to control the control target, such as controlling the fuel injection amount of the injection valve (for example, in the Showa era). 4
(Refer to Electronically Controlled Gasoline Injection System Maintenance Guidelines 3, published by Nissan Motor Co., Ltd., September 1988).

However, when two pressure sensors are used in this way, the errors of the individual sensors accumulate, resulting in a large error in the obtained air flow j-1 and a disadvantage that the cost is high.

There is also a system in which the absolute pressure in the intake pipe is measured and the intake air flow rate is calculated from this measured value and the rotational speed of the engine. However, in a system in which the intake air flow rate is calculated based on the intake pipe internal pressure and rotational speed, when the atmospheric pressure is, for example, 760 mmHg, A and 6
As shown in Fig. 2, even if the pressure inside the intake pipe is the same, there will be a large error in the air temperature, and this error can reach more than ten percent, so changes in atmospheric pressure will affect fuel efficiency and drivability. , which could have an adverse effect on exhaust characteristics.

<Object of the Invention> The present invention has been made in view of the above-mentioned circumstances, and its purpose is to effectively utilize the pressure detection means for detecting the pressure inside the intake pipe to detect atmospheric pressure. The objective is to simplify the device and reduce its cost while improving accuracy.

<Structure of the Invention> In order to achieve the objects as described in 1-1, the present invention provides a full-open control system that detects that the operating state of the engine is near full-open from the opening degree of the intake throttle valve, etc., as shown in FIG. a detection means, and means for calculating atmospheric pressure PA based on the output of the pressure detection means that detects the pressure PM in the intake pipe when it is detected through the full open detection means that the engine is being operated near full open. and supplying the output PA of the calculation means and the output PM of the pressure detection means to the engine control means,
The number of expensive pressure sensors is reduced while maintaining high detection accuracy, making it possible to control the controlled object with high precision.

<Example> The present invention will be explained in detail below.

FIG. 4 is a block diagram showing an embodiment of the present invention, in which the output of an absolute pressure sensor 12 provided as pressure detection means for detecting the pressure in the intake manifold 11 of the internal combustion engine 10 (pressure downstream of the intake throttle valve) is shown in FIG. PM is supplied to the atmospheric pressure calculation device 13 and the engine control device 14. or,
A full-open switch 17 is provided in the throttle chamber 15 connected to the intake manifold 11 as a full-open detection means for detecting whether or not the intake throttle valve 16 is close to fully open. It is supplied to the atmospheric pressure calculation device 13. Incidentally, the engine control device 1 described above
4 is supplied with various signals such as engine rotational speed N, engine cooling water temperature Tw, and intake air temperature TA from a sensor (not shown), and these signals are used as control signals to be supplied to the fuel injection valve 18 and to an ignition device (not shown). It is configured to optimally control each ignition signal.

In the pressure detection device configured in this way, first, it is determined whether or not to calculate the atmospheric pressure based on the state of the fully open switch 17, as shown in the flowchart shown in FIG. 5, for example. At this time, when the full open switch 17 is off, it is determined that the intake throttle valve 16 is not near full open, and the atmospheric pressure is not calculated, and the atmospheric pressure PA and the intake pipe internal pressure PM are
Calculate the pressure ratio PR between Similarly, the engine rotation speed N
For example, if it is more than 3000 rpm, the intake flow rate becomes large and the intake pipe internal pressure PM causes a large pressure loss in the intake pipe, and the error in calculating atmospheric pressure from the intake pipe internal pressure PM becomes large. Let's move on to calculating the pressure ratio PR.

On the other hand, when the full open switch 17 is on, the intake throttle valve 16 is close to fully open, so in this case, the engine rotation speed N
Atmospheric pressure PA on the condition that it is 300 Orpm or less
Perform the calculation. When calculating this atmospheric pressure PA,
First, the pressure loss correction constant I is determined by table lookup based on the rotational speed N.

FIG. 6 is an example of table values of the pressure loss correction constant I.

Next, the absolute pressure PM in the intake pipe output from the absolute pressure sensor 12 and the pressure loss correction constant I determined as above
By calculating the atmospheric pressure PA from the following formula, %, the new data and old data are averaged with a weight of 1/64. Note that when calculating the atmospheric pressure PA, it is desirable to perform smoothing processing because the intake pipe internal pressure PM fluctuates greatly with each intake cycle.

] - After determining the atmospheric pressure PA as described above, store this value in the random access memory and calculate the pressure ratio PR.
Calculate = PM/PA. Note that this pressure ratio PR is the ratio of intake pressure to atmospheric pressure, and is used when calculating intake air mQ per revolution of the engine.

Further, the intake air amount Q per rotation is calculated by table lookup from the pressure ratio PR and the engine rotational speed N determined as described in section 2 above. FIG. 7 shows an example of the table map.

The inventors of the present invention have confirmed through experiments that there is a correlation between the pressure ratio PR and the intake air amount Q per revolution as shown in FIG. In other words, qualitatively speaking, intake air is introduced into the cylinder at the differential pressure between the intake pipe internal pressure PM and the cylinder internal pressure, so the higher the intake pipe internal pressure PM, the higher the intake air filling efficiency. In addition, as the ratio PR between the intake pipe internal pressure PM and the atmospheric pressure PA becomes larger, the intake throttling effect becomes smaller and the intake air amount Q increases. This is because it shows a value equivalent to the amount of intake air Q per rotation, and therefore changes depending on the engine rotation speed.

Next, the intake air temperature T output from a temperature sensor (not shown)
Based on A, the intake air temperature correction coefficient KTA is determined by table lookup. An example of the table map is shown in Figure fftJ8.

Then, the basic injection amount TP of fuel is calculated based on the intake air temperature correction coefficient KTA, the intake air amount Q, and the atmospheric pressure PA using the following formula %. Here, since Q is the volume, the mass of air is QX air density (temperature dependent), and if the air temperature is, for example, 4
Assuming that the temperature is 0°C, the air density is expressed by the following formula (%) and 1.128/760 X I/target air-fuel ratio (A/
By setting F) to K, the basic injection amount TP can be determined by the following equation 1. Thereafter, various supplementary IFs such as a correction based on the engine cooling water temperature Tw and a full-open increase correction based on the engine rotational speed N and pressure ratio PR are performed to form a control signal, which is supplied to the injection valve 18.

In the embodiment, the full open switch 17 is used with the full open detection - L stage, but a negative pressure switch that operates based on the pressure difference between the first and downstream of the intake throttle rib rlG, or a negative pressure switch that operates between the atmospheric pressure and the negative intake pressure. A negative pressure switch that operates with

In addition, in this case of j↓1, it is better to use a switch that operates at a suction negative pressure of, for example, about 5 mmHg, and as shown in factor 9, a negative pressure switch 21 incorporating a check valve 18 and an orifice 20 should be used. It is also possible to narrow the intermittent zone of the switch signal due to intake pulsation. 22 is a diaphragm, 23 is a spring, and 24 is a switch.

Furthermore, it is needless to mention in detail that by supplying the rotational speed N to the atmospheric pressure calculating device 13, the calculated viscosity of the atmospheric pressure PA can be made higher.

<Effects of the Invention> As explained above, according to the present invention, the atmospheric pressure is determined by the output of the pressure detection means for detecting the pressure inside the intake pipe and the output of the full open detection means for detecting whether the intake air is throttled or close to fully open. This eliminates the need to use two conventionally expensive sensors, the intake pipe internal pressure sensor and the atmospheric pressure sensor, reducing costs without compromising pressure detection accuracy. can. In addition, there is no risk that the measurement accuracy will fluctuate due to the influence of atmospheric pressure, unlike in conventional systems in which the control target of an internal combustion engine is controlled using the pressure inside the intake pipe. If applied to the system, it is possible to control objects to be controlled such as the air-fuel ratio and ignition timing with high precision, and maintain good air-fuel ratio, drivability, exhaust characteristics, etc.

[Brief explanation of drawings]

FIG. 1 is a schematic block diagram of a conventional example, 9f, 2
The figure is a characteristic diagram showing the relationship between pressure detection value and air Effi of another conventional example, Figure 3 is a block diagram showing the configuration of the present invention, and Figure 4 is a block diagram of an embodiment of the present invention. Similarly, FIG. 5 is a flowchart, and FIGS. 6 to 8 are sectional views showing the steps in FIG. 5. 10... Internal combustion engine II... Intake manifold 1
2...Absolute pressure sensor (pressure detection means) 13...Atmospheric pressure calculation device (atmospheric pressure Qi (calculation P stage) 14...Engine control device 16...Intake throttle valve 17...Full open switch ( Fully open detection means) 18...Fuel injection valve patent applicant 1-1 San Jidoichi Co., Ltd. agent Go1'ri 1: Sasashima Fujido Idl Fig. 3 Fig. 4 Fig. 6 Fig. 7 N ( rpm) Fig. 8 TA('C) Fig. 9 4

Claims (1)

[Claims] A pressure detection means for detecting the pressure in the intake pipe of an internal combustion engine, a fully open detection means for detecting that the intake throttle valve is near full open, and a pressure detection means for detecting the pressure in the intake pipe near the full open intake throttle valve according to the output of the full open detection means. A pressure detection device for an internal combustion engine, comprising: atmospheric pressure calculation means for reading and calculating atmospheric pressure. .