JPH05222998A - Air intake state detection device for internal combustion engine - Google Patents

Abstract

PURPOSE:To estimate cylinder pressure and air intake pipe pressure at each crank angle of an internal combustion engine changing momentarily without using a pressure sensor and others. CONSTITUTION:This device has a flow passage opening area co computing means 2, an air intake valve opening area computing means 3 and an exhaust valve opening area computing means 4 respectively searching for a flow passage opening area between the upstream and the downstream of a throttle valve at a crank angle, an opening area of an air intake valve and an opening area of an exhaust valve. Flow rates for these opening areas are searched for by an air intake pipe inflow rate computing means 5, an air intake valve flow rate computing means 6 and an exhaust valve flow rate computing means 7 respectively. It is devised so as to estimate cylinder pressure and air intake pipe pressure successively in accordance with inflow and outflow rates of gas to and from the inside of a cylinder and inflow and outflow rates of gas to and from the air intake valve.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an intake state detecting device for sequentially detecting cylinder pressure at each crank angle of an internal combustion engine and intake pipe pressure on the downstream side of a throttle valve.

[0002]

2. Description of the Related Art Needless to say, it is necessary to accurately measure the amount of air actually flowing into a cylinder in order to accurately control the air-fuel ratio of an internal combustion engine, but it is necessary to use a cylinder without a pressure sensor or an air flow meter. As a method for detecting the amount of intake air into the interior, Japanese Patent Laid-Open No. 2-70957 discloses a method of estimating the vertical pressure difference of the throttle valve and estimating the intake air amount using the throttle valve opening. Is proposed.

Further, in JP-A-58-23245 and JP-A-62-101868, in order to reduce pumping loss of the engine, an auxiliary intake passage having an intake cutoff valve in an intake system of each cylinder is provided. And a closing valve that closes the intake passage when the load is low.

[0004]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
The method disclosed in Japanese Patent No. 957 only estimates the amount of air that may have flowed into the cylinder during one cycle from the flow rate of the throttle valve, the temperature of the gas, and the like. It is not possible to capture the changing cylinder pressure or intake pipe pressure. Therefore, when the intake valve starts to open, the gas amount of the so-called blowback phenomenon that returns from the inside of the cylinder to the intake pipe side is ignored, and the error in the estimated intake pipe pressure increases, and eventually the intake air in the cylinder during one cycle. There is the drawback that the error in the quantity estimate appears very large. Especially, when the volume of the intake pipe on the downstream side of the throttle valve is small, the pressure fluctuation due to the blowback phenomenon becomes large, so that the influence is large, and the accuracy of the estimated value becomes low accordingly.

On the other hand, various techniques for reducing pumping loss have been proposed as described in Japanese Patent Laid-Open No. 58-23245, but in many of them, the pressure on the intake valve upstream side of each cylinder is reduced. The shape changes with the stroke of the cylinder. Therefore, when it is combined with a known fuel injection device in which an electromagnetic fuel injection valve is provided for each cylinder toward the intake port as in JP-A-62-101868, the valve opening time and the actual injection amount are Since the proportional relationship of is broken by the fluctuation of the intake pipe pressure, the intake pipe pressure at the fuel injection timing of each cylinder is detected, and the opening time of each fuel injection valve, that is, the drive pulse width applied to each, is detected according to the pressure. Need to be corrected. In order to realize such a correction, in the above publication, the pressure sensor directly detects the intake pipe pressure for each cylinder. However, this method uses a plurality of pressure sensors and therefore has a configuration. It becomes complicated and the response delay of the correction tends to be a problem.

Therefore, the present invention provides an intake state detecting device capable of accurately estimating the cylinder pressure and the intake pipe pressure, which change momentarily with the piston stroke, without directly detecting the pressure sensor. Is what you are trying to do.

[0007]

As shown in FIG. 1, an intake state detecting apparatus for an internal combustion engine according to the present invention includes a crank angle detecting means 1 for detecting a crank angle of an engine and a throttle valve at this crank angle. The flow passage opening area calculating means 2 for obtaining the total flow passage opening area between the upstream side and the downstream side, the intake valve opening area calculating means 3 for obtaining the opening area of the intake valve at this crank angle, and the opening area of the exhaust valve are shown. Using the exhaust valve opening area calculation means 4 to be obtained and the intake pipe pressure obtained last time, the intake pipe inflow amount calculation means 5 to obtain the flow rate flowing into the downstream side of the throttle valve from this, the throttle valve upstream side pressure and the flow passage opening area. In addition, using the cylinder pressure and the intake pipe pressure obtained last time, the intake valve flow rate calculation means 6 for obtaining the intake valve flow rate from this and the above-mentioned intake valve opening area, and the cylinder pressure obtained last time the combustion pressure. Exhaust valve flow rate calculation means 7 that corrects based on the rate of increase and calculates the exhaust valve flow rate from this, the exhaust system pressure, and the exhaust valve opening area, the actual cylinder volume corresponding to the crank angle, and the intake valve flow rate. Cylinder pressure calculating means 8 for calculating the cylinder pressure at the crank angle from the exhaust valve flow rate, and intake pipe pressure calculating means 9 for calculating the intake pipe pressure at the crank angle from the intake pipe inflow amount and the intake valve flow rate. And is configured.

[0008]

This intake state detecting device successively obtains the cylinder pressure and the intake pipe pressure which change momentarily along with the piston stroke.
The opening area of the flow passage between the upstream side and the downstream side of the throttle valve can be obtained from the throttle valve opening and the like. If there is a bypass passage, etc., it is necessary to include the flow passage area. Further, the intake valve opening area calculating means 3 and the exhaust valve opening area calculating means 4 respectively obtain the opening areas at that time from the valve lift amount, the valve diameter and the like.

Gas (air or air-fuel mixture) flows into the downstream side of the throttle valve from the upstream side of the throttle valve through the above-mentioned flow passage opening area. The inflow amount is the intake pipe pressure on the downstream side and the upstream side. It is determined by the pressure (which is approximately atmospheric pressure in a naturally aspirated engine) and the flow passage opening area. Therefore, in the intake pipe inflow amount calculating means 5, the intake pipe inflow amount is approximately calculated by using the intake pipe pressure obtained last time.

The flow rate of gas flowing into the cylinder through the intake valve, that is, the intake valve flow rate, is determined by the intake pipe pressure on the upstream side of the intake valve, the cylinder pressure on the downstream side of the intake valve, and the intake valve opening area. Therefore, in the intake valve flow rate calculation means 6,
By using the cylinder pressure and the intake pipe pressure obtained last time, this intake valve flow rate is approximately obtained.

Similarly, the flow rate of gas flowing out of the cylinder via the exhaust valve, that is, the exhaust valve flow rate, can be regarded as the cylinder pressure on the upstream side of the exhaust valve and the exhaust system pressure on the downstream side of the exhaust valve (usually about atmospheric pressure). Can be done) and the exhaust valve opening area. Therefore, in the exhaust valve flow rate calculation means 7, the exhaust valve flow rate is approximately calculated by using the cylinder pressure calculated last time. The cylinder pressure used at this time is corrected by the correction means 10 based on the combustion pressure increase rate.

If the flow rate of the intake valve flowing into the cylinder and the flow rate of the exhaust valve flowing out of the cylinder are known as described above, the integrated amount of them becomes the gas amount in the cylinder. Therefore, at the piston position at that time, The cylinder pressure can be obtained from the relationship with the actual cylinder volume. still,
The value of the cylinder pressure obtained by the cylinder pressure calculating means 8 serves as a basis for the next calculation of the intake valve flow rate and the like, as described above.

Similarly, if the intake pipe inflow amount flowing into the intake pipe and the intake valve flow amount flowing out from the intake pipe are known, the intake pipe pressure can be obtained. The value of the intake pipe pressure calculated by the intake pipe pressure calculating means 9 becomes the basis for the next calculation of the intake pipe flow rate and the like.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings.

FIG. 2 is a structural explanatory view of an internal combustion engine equipped with the intake state detecting device according to the present invention and designed to reduce pumping loss. An intake passage 13 is centered around a cylinder 12 of the internal combustion engine 11. And the exhaust passage 14 are formed in a cross flow type, and an intake valve 15 and an exhaust valve 16 are opened and closed between the passages 13 and 14 and the cylinder 12. The intake valve 15 and the exhaust valve 16 are driven by cam shafts 17 and 18, respectively. A piston 19 is fitted in the cylinder 12.

The intake passage 13 is provided with a throttle valve 20 for each cylinder, and a throttle opening sensor 21 such as a potentiometer is provided to detect the opening of the throttle valve 20. And this throttle valve 2
The bypass passage 22 is formed for each cylinder so as to bypass 0 and connect the upstream side and the downstream side of the intake passage 13 to each other. The bypass passage 22 is used for reducing pumping loss, and a flow rate control valve 23 including a duty control type electromagnetic valve or the like is provided in the bypass passage 22. A fuel injection valve 24 for supplying fuel to each cylinder is arranged downstream of the throttle valve 20 in the intake passage 13, more specifically, near the intake port of each cylinder. The fuel whose pressure is adjusted to a predetermined pressure is constantly supplied to the fuel injection valve 24, and the injection amount is measured by the valve opening time, that is, the pulse width of the drive pulse signal.

Reference numeral 25 is a crank angle sensor for detecting the rotation of the camshafts 17, 18 or the crankshaft. The crank angle sensor 25 is a reference position of the crank angle of each cylinder, for example, before the top dead center of the explosion stroke. 60 ° C
Reference signal (REF signal) consisting of pulses output at A
And a angle signal (POS signal) consisting of a pulse train output for each unit crank angle, for example, every 1 ° CA. The reference signal has a different pulse width for each cylinder number in order to determine the cylinder.

The control unit 26 to which the detection signal of the crank angle sensor 25 and the detection signal of the throttle opening sensor 21 are input uses a so-called microcomputer system. Based on various detection signals, ignition timing control and The fuel injection amount control and the like are performed, and the opening degree of the flow rate control valve 23 in the bypass passage 22 is controlled.

In the above structure, the flow control valve 23 is
It operates before and after the intake stroke of the corresponding cylinder. Specifically, the intake stroke of the corresponding cylinder is determined based on the reference signal and the angle signal from the crank angle sensor 25, and the flow control valve 23 is opened during the period other than the intake stroke. As a result, the intake pipe pressure at the start of the intake stroke (throttle valve 20 and intake valve 1
(Pressure between 5) approaches the atmospheric pressure, and pumping loss is reduced. Then, during the intake stroke, the flow control valve 23
The degree of opening of is controlled appropriately to suppress the amount of air flowing toward the cylinder 12.

On the other hand, the fuel injection amount is calculated on the basis of the estimated amount of air taken into the cylinder 12 in the intake stroke, as will be described later. Then, the pulse width of the drive pulse signal is determined according to the injection amount. However, with the control of the flow control valve 23 as described above, the throttle valve 2
Even if the opening degree of 0 is constant, the intake pipe pressure constantly fluctuates in each cylinder. Therefore, since the actual injection amount for the same pulse width is affected by the intake pipe pressure,
The intake pipe pressure is sequentially detected by the process described later, and the pulse width is corrected so as to cancel the influence. The correction amount of the pulse width with respect to the intake pipe pressure is obtained based on, for example, a predetermined map.

Next, the process of successively estimating the intake pipe pressure will be described with reference to the flowchart of FIG. Incidentally, this processing is interrupted in synchronization with the angle signal for each 1 ° CA. That is, the intake pipe pressure that changes moment by moment is obtained for each 1 ° CA.

First, in step 1 (abbreviated as S1 etc. in the figure), the ignition advance value at the latest combustion stroke and the intake pipe pressure at the end of the latest intake stroke, that is, when the intake valve 15 is closed, Using the engine speed (obtained from the angle signal), the combustion pressure increase rate at the current crank angle is obtained from a predetermined data map. That is, the change in pressure in the cylinder 12 due to combustion can be approximately represented as shown in FIG. 4, and after the ignition delay period shown as (a),
As shown in (b), the pressure rises and reaches its maximum near ATDC 15 °, for example. Since the ignition advance value is set so that the torque becomes maximum, the ignition advance value is substantially constant even at this pressure peak. The above-mentioned times (a) and (b) change depending on the number of revolutions, but in terms of crank angle, they are considered to occupy substantially constant ratios from the ignition timing to the peak time. And the maximum value of the pressure rise rate shown as (C) is
It becomes substantially proportional to the amount of air-fuel mixture sucked into the cylinder 12, and the amount of air-fuel mixture can be approximately calculated from the intake pipe pressure and the engine speed. Further, the period shown in (d) corresponds to the beginning of the exhaust stroke, and the pressure begins to decay at the same time as the start of the exhaust stroke, but since the decay speed is proportional to the engine speed, the crank angle is approximately It will be constant. Therefore, based on the characteristics of FIG. 4, the combustion pressure increase rate at the current crank angle is obtained by searching from the predetermined data map. It should be noted that the intake pipe pressure is not directly detected by the sensor, but will be described in Step 1 below.
The stored data of the value sequentially calculated in 2 is used.

In step 2, the actual volume in the cylinder 12 corresponding to the position of the piston 19 at the current crank angle is obtained from, for example, a predetermined data map.

Further, in step 3, the opening area of the exhaust valve 16 at the current crank angle is obtained from, for example, a predetermined data map. Similarly, in step 4, the opening area of the intake valve 15 is obtained.

Then, in step 5, the flow rate of the gas passing through the intake valve 15, that is, the intake valve flow rate is calculated based on the intake valve opening area, the intake pipe pressure, and the cylinder pressure. Here, as the intake pipe pressure and the cylinder pressure, the values previously obtained in step 12 and step 10 described later are used. As a specific method of this processing, a map of the pressure difference and the flow rate in the unit opening area as shown in FIG. 5 is given in advance, and the flow rate with respect to the pressure difference (that is, the difference between the intake pipe pressure and the cylinder pressure) is calculated from this map. Is obtained by interpolation calculation, and this is multiplied by the intake valve opening area to obtain the intake valve flow rate.

In step 6, the total flow passage opening area between the upstream side and the downstream side of the throttle valve 20 is obtained. This is basically given as the sum of the opening area of the throttle valve 20 detected by the throttle opening sensor 21 and the opening area of the flow control valve 23, and further, an air passage coefficient of about 0.8 is given. It should be multiplied to approximate the actual value. The open / closed state of the flow control valve 23 is given by an internal signal of the control unit 26. Further, the value of the flow passage opening area is further multiplied by a correction value described later, if necessary, in order to improve accuracy.

Further, in step 7, the intake pipe inflow amount flowing from the upstream side of the throttle valve 20 to the downstream side in the intake passage 13 is obtained. This is obtained from the upstream side pressure, the downstream side intake pipe pressure, and the flow passage opening area in step 6, but the upstream side pressure is regarded as atmospheric pressure, and the intake pipe pressure is also the previously obtained value. And step 5
Similarly, a map of pressure difference and flow rate in unit opening area is given in advance, and the flow rate for pressure difference (difference between atmospheric pressure and intake pipe pressure) is obtained from this by interpolation calculation. Multiply by to obtain the intake pipe inflow.

Further, in step 8, the flow rate of gas passing through the exhaust valve 16, that is, the exhaust valve flow rate is calculated based on the exhaust valve opening area, the upstream cylinder pressure, and the downstream exhaust system pressure in step 3 described above. .. Here, as the cylinder pressure, a value previously obtained in step 13 described later, that is, a value obtained by correcting the cylinder pressure obtained in step 10 with the combustion pressure increase rate in step 1 is used. The exhaust system pressure is regarded as atmospheric pressure. Note that the specific processing of step 8 is similar to step 5 in that a map of the pressure difference and the flow rate in the unit opening area is given in advance, and the flow rate for the pressure difference is obtained by interpolation calculation from this map, and Multiply the exhaust valve opening area to obtain the exhaust valve flow rate.

Next, at step 9, the exhaust valve flow rate at step 8 is subtracted from the intake valve flow rate at step 5, and the cylinder 12 per unit time (or unit crank angle) is subtracted.
Calculate the amount of gas flowing in and out.

In step 10, the cylinder pressure is obtained based on the amount of gas flowing into and out of the cylinder 12. Specifically, the gas amount in the cylinder 12 obtained by integrating the inflow and outflow gas amounts is n, the sum of the cylinder volume at that time and the intake pipe volume after the throttle valve 20 is V, the gas constant is R,
When the gas temperature is T, the cylinder pressure P can be obtained from the relationship of PV = nRT. Since the gas temperature T changes due to compression and expansion, it is obtained from the following equation.

T _K = T _K-1 (V _K-1 / V _K ) ^r-1 where T _K is the temperature of the gas in the cylinder, T _K-1 is the temperature calculated last time, and V _K-1 is the temperature calculated last time. Is the cylinder volume at the time of calculation, V _K is the cylinder volume at the time of calculation, and r is the ratio of the constant pressure specific heat and the constant volume specific heat.

In step 11, the intake valve flow rate in step 5 is subtracted from the intake pipe inflow amount in step 7, and the inside of the intake pipe (between the throttle valve 20 and the intake valve 15) per unit time (or unit crank angle) is subtracted. Calculate the amount of gas flowing in and out.

In step 12, the gas flowing into and out of the intake pipe is integrated to obtain the amount of gas in the intake pipe, and the intake pipe pressure is calculated in the same manner as in step 10.

In step 13, the above step 1
The cylinder pressure obtained in 0 is multiplied by the combustion pressure increase rate in step 1 to obtain the cylinder pressure in consideration of combustion. This value is used when calculating the exhaust valve flow rate as described above.

As described above, the cylinder pressure and the intake pipe pressure at each crank angle are sequentially estimated, and based on these, the amount of air actually sucked into the cylinder 12 in the intake stroke and the injection accompanying the fluctuation of the intake pipe pressure are performed. A pulse width correction amount and the like are obtained. Incidentally, since the blowback phenomenon at the beginning of the intake stroke is also correctly reflected in the intake valve flow rate and the like, the amount of air in the cylinder 12 and the like can be accurately obtained.

The processing in and after step 14 is performed by giving a correction in comparison with the actual machine operating state in order to further improve the accuracy in the above estimation. First, in step 1
In step 4, the engine generated torque that may be generated at that time is estimated based on the cylinder pressure in step 13. This is calculated from the pressure applied to each piston of all cylinders, connecting rod diameter, and crankshaft rotation diameter.

In step 15, the engine friction is estimated according to a predetermined map based on the actual engine speed at that time. Then, in step 16, the friction is subtracted from the estimated engine-generated torque in step 14, and the output torque to be output to the outside is estimated.

Further, in step 17, based on the estimated output torque, the engine speed that will be generated by the output torque is estimated.

Then, in step 18, the difference between the estimated engine speed and the actual engine speed is obtained, and in step 19, a correction value corresponding to this difference is obtained by, for example, the PI control method. This correction value is used when calculating the total flow path opening area in step 6.

That is, if there is an error in the cylinder pressure or the like estimated as described above, this is reflected in the estimated engine speed, and a difference from the actual engine speed occurs, so a correction value necessary for correction is obtained. It is fed back to the calculation of the total flow passage opening area. Therefore, the accuracy of the estimated value of the cylinder pressure and the like is further improved.

FIG. 6 is a block diagram showing a series of controls as described above in order to facilitate understanding. S1 attached to each block in this block diagram
Symbols such as ... Correspond to the respective steps of the flowchart of FIG. 3 described above, and the description thereof will be omitted to avoid duplication.

[0042]

As is apparent from the above description, according to the intake state detecting device for an internal combustion engine of the present invention, the cylinder pressure and the intake pipe pressure of the internal combustion engine can be directly measured by a pressure sensor, an air flow meter or the like. The estimation can be performed with high accuracy without using the detection sensor. In particular, the cylinder pressure and intake pipe pressure that change momentarily with the crank angle can be detected sequentially,
In addition, since it is not affected by the intake air blowback phenomenon and the like, it can be widely used for air-fuel ratio control and the like. Further, it is possible to perform estimation in a state where the phase is shifted with respect to the current crank angle, and it is possible to give appropriate correction in advance when the intake pipe pressure is changed to reduce pumping loss.

[Brief description of drawings]

FIG. 1 is a claim correspondence diagram showing a configuration of the present invention.

FIG. 2 is a structural explanatory view showing a mechanical structure of an embodiment of the present invention.

FIG. 3 is a flowchart showing a control flow in this embodiment.

FIG. 4 is a characteristic diagram showing a characteristic of a pressure increase rate associated with combustion.

FIG. 5 is a characteristic diagram showing a relationship between a pressure difference in a unit opening area and an intake valve flow rate.

FIG. 6 is a block diagram showing the control contents of this embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Crank angle detecting means 2 ... Flow path opening area calculating means 3 ... Intake valve opening area calculating means 4 ... Exhaust valve opening area calculating means 5 ... Intake pipe inflow amount calculating means 6 ... Intake valve flow rate calculating means 7 ... Exhaust valve flow rate Calculation means 8 ... Cylinder pressure calculation means 9 ... Intake pipe pressure calculation means 10 ... Correction means calculation means

Claims (1)

[Claims] 1. A crank angle detecting means for detecting a crank angle of an engine, a flow passage opening area calculating means for obtaining a total flow passage opening area between an upstream side and a downstream side of a throttle valve at this crank angle, and The intake valve opening area calculating means for obtaining the opening area of the intake valve at the crank angle, the exhaust valve opening area calculating means for obtaining the opening area of the exhaust valve, and the intake pipe pressure obtained last time are used. Using the intake pipe inflow amount calculating means for obtaining the flow rate flowing into the downstream side of the throttle valve from the flow passage opening area and the cylinder pressure and the intake pipe pressure obtained last time, the intake valve flow rate is calculated from this and the above intake valve opening area. The intake valve flow rate calculation means to be calculated and the cylinder pressure previously obtained are corrected based on the combustion pressure increase rate, and the exhaust valve flow rate is calculated from this, the exhaust system pressure, and the above exhaust valve opening area. Air valve flow rate calculation means, cylinder pressure calculation means for calculating cylinder pressure at the crank angle from the cylinder actual volume corresponding to the crank angle, the intake valve flow rate, and the exhaust valve flow rate, the intake pipe inflow amount, and the An intake state detecting device for an internal combustion engine, comprising: an intake pipe pressure calculating means for calculating an intake pipe pressure at the crank angle from an intake valve flow rate.