JPH08312426A - Output measuring method and control method of spark ignition type engine - Google Patents

Abstract

PURPOSE: To provide a torque measuring method with which can be suppressed the output variation at a small value even when a lean combustion with a high air-fuel ratio is carried out in case of carrying out an EGR liable to generate an output variation, by carrying out a feedback control using an engine torque or a PMI adequately, as well as carrying out the operation simply and accurately, when the engine torque or the PMI is calculated by measuring the combustion pressure in a combination chamber. CONSTITUTION: The combination chamber pressures at the crank angle (a0), in the space from the finishing of the exhaust stroke to the initial stage of the compression stroke; at the crank angle (a1) near the top dead point and before the top dead point; and at the crank angles (a2 to a5) at the top dead point, and near the top dead point and after the top dead point, are detected, and the engine torques are calculated depending on those combustion chamber pressure data.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for calculating the indicated mean effective pressure or shaft torque which is the basis of calculation for controlling the operating state of an internal combustion engine. INDUSTRIAL APPLICABILITY The present invention is applicable to internal combustion engines such as engines for automobiles and motorcycles, marine engines such as outboard motors, and other two-cycle and four-cycle gasoline engines. It is also applicable to an engine and an engine using a carburetor.

[0002]

2. Description of the Related Art When the fuel is diluted or EGR (exhaust gas recirculation) is performed in order to reduce fuel consumption of the engine and exhaust gas,
The deterioration of combustion is accompanied. At this time, the combustion becomes unstable and varies, and the output fluctuation becomes large and the drivability decreases. In order to deal with this, there is known a technique of calculating the axial torque of the engine or PMI (indicated average effective pressure) corresponding thereto and controlling the air-fuel ratio, the EGR amount and the like based on the calculated. A torque fluctuation control device according to such a conventional technique is disclosed in Japanese Patent Laid-Open No. 214947/1992. In the control device described in this publication,
The combustion pressure of each cylinder is detected at a predetermined detection timing, and the shaft torque is calculated based on this detected value. In this case, based on the crank angle detection signal, when the crank angle is the following timing for each cylinder, that is, (1) BTDC15
5CA (155 degree crank angle before top dead center), (2) ATD
C5 degree CA (5 degree crank angle after top dead center), (3) ATD
C20 degree CA, (4) ATDC 35 degree CA, (5) AT
The shaft torque is calculated based on the detected values of the combustion pressure sensor at five crank angles of DC 50 degrees CA.
In this case, since the combustion pressure signal of BTDC 155 degrees CA in (1) is used as a reference value for absorbing variations, the axial torque for each cylinder is substantially based on the four crank angles in (2) to (5). Is calculated.

[0003]

However, the combustion in each cycle is started from BTDC (before top dead center), and this combustion pressure exerts a negative work on the piston. Therefore, as described in the above publication, the ATDC is substantially
If the shaft torque is calculated from the combustion pressure only (after top dead center), there is a problem that the calculated value is larger than the torque value that is actually generated. Further, the combustion state before top dead center changes depending on the ignition timing, the fuel amount, the air-fuel ratio, etc. in the ignition type engine even if the pressure change in the combustion chamber after the top dead center is constant, and the compression ignition type diesel engine. In the engine, it changes depending on the fuel injection timing, the fuel injection amount, the injection pressure, the air-fuel ratio, and the like. Therefore, if the axial torque is calculated only from the combustion pressure after top dead center, it is not possible to catch the change in the negative work amount before the top dead center due to various combustion states, so it is possible to accurately calculate the axial torque. Can not. For example, when performing EGR, when performing lean combustion with a high air-fuel ratio, combustion tends to vary from cycle to cycle, and the negative work amount before the top dead center also tends to vary. Therefore, if the engine drive control is performed based on such an axial torque, it becomes difficult to control the ignition timing to be appropriate and the air-fuel ratio to be appropriate in accordance with various combustion states. In particular, EG
When R is performed, lean-burn combustion varies from cycle to cycle, resulting in large output fluctuation.

The present invention has been made in view of the above-mentioned problems of the prior art. When measuring the combustion pressure in the combustion chamber to calculate the shaft torque or PMI, it is possible to perform the calculation easily and accurately. The purpose is to further,
By performing feedback control using this shaft torque or PMI measuring method, for example, when performing EGR in which output variation is likely to occur, output variation can be suppressed to a small level even when performing lean combustion with a high air-fuel ratio. It is intended to provide an engine control method.

[0005]

In order to achieve the above object, in the invention according to claim 1, the crank angle from the end of the exhaust stroke to the beginning of the compression stroke, and the crank angle and the spark angle and the spark ignition and thereafter. And the combustion chamber pressure at the crank angle before top dead center and at the crank angle at or near top dead center from the compression process to the expansion process and after top dead center are detected. An engine output measuring method for calculating the indicated mean effective pressure or shaft torque based on the above is provided.

Furthermore, the present invention provides a method for controlling a spark ignition engine, characterized in that the operating state of the engine is controlled based on the indicated mean effective pressure or shaft torque calculated by the method of claim 1.

In the preferred embodiment, the indicated mean effective pressure or shaft torque is calculated for each combustion cycle, the difference from the calculation result in the previous cycle is determined, and the operating state is controlled based on this difference. It is characterized by that.

[0008]

To calculate the PMI, the crank angle from the end of the exhaust stroke to the beginning of the compression stroke, the crank angle near the top dead center during the compression stroke and before the top dead center, and the expansion from the compression stroke During the process, the combustion chamber pressure is detected near the top dead center and at the crank angle after the top dead center. In this case, the crank angle from the end of the exhaust stroke to the beginning of the compression stroke is the crank angle within the range where the pressure in the combustion chamber is the lowest and approaches the atmospheric pressure. A point or its vicinity. That is, in a 4-cycle engine,
The exhaust gas from the bottom dead center after the explosion discharges the combustion gas in the combustion chamber, and the pressure in the combustion chamber decreases toward the top dead center and approaches the atmospheric pressure. In the suction stroke after top dead center, a state close to the atmospheric pressure is maintained due to the introduction of fresh air, and the pressure is gradually increased from the compression stroke after bottom dead center. The pressure in the combustion chamber at one point in the range in which the pressure in the combustion chamber is the lowest and approaches the atmospheric pressure is detected. On the other hand, in a 2-cycle engine, after the explosion, the piston drops and the pressure drops, and when the exhaust port opens, the pressure in the combustion chamber further drops accordingly, and when the scavenging port opens, fresh air is introduced from the crank chamber and atmospheric pressure is reached. Approach. When the piston rises from the bottom dead center with the exhaust port open, the scavenging port closes and the exhaust port closes, compression starts and the pressure gradually increases. That is, from the end of the exhaust stroke to the beginning of the compression stroke in the claims,
It is a period from when the scavenging port is opened and intake is started in a state where the exhaust port is opened and the exhaust port is opened after the exhaust is started until the exhaust port is closed and compression is started.

Spark ignition is performed after compression and before top dead center. The pressure in the combustion chamber is detected before this top dead center. Furthermore, the pressure in the combustion chamber is detected at top dead center or thereafter preferably at several points.

The crank angle from the end of the exhaust stroke to the beginning of the compression stroke, the crank angle near the top dead center and before the top dead center, and the crank angle near the top dead center and after the top dead center. A plurality of n points (eg 6
The combustion chamber pressure at the crank angle (point) is detected, and PMI is calculated from the first-order approximation formula. This approximate expression is represented by PMI = C + C1 * (P1-P0) + C2 * (P2-P0) + ... + Cn * (Pn-P0). As can be seen from the above equation, PMI is represented by multiplying the pressure data P1 to Pn by a preset constant of C1 to Cn and adding a preset constant C. Here, P0 is the point of the atmospheric pressure level (for example, the crank angle near BDC as described above).
Combustion chamber pressure, which is subtracted from each pressure value of P1 to Pn in order to correct the offset output due to sensor drift and the like. Further, P1 is the combustion chamber pressure near the top dead center and at the crank angle before top dead center, and P2 to Pn are the combustion chamber pressure near the top dead center and at the crank angle after top dead center. With such a simple first-order approximation operation, a value that is almost the same as the actual value can be calculated accurately in a short time. Therefore, by controlling the ignition timing and the air-fuel ratio of the engine by using such PMI, the responsiveness is enhanced, and the output fluctuation is suppressed by accurately following the operating state when the EGR control of the lean burn is performed. be able to.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram of a multi-cylinder spark ignition type 4-cycle engine to which the present invention is applied. This engine is composed of a crankcase 2, a cylinder body 3 and a cylinder head 4 above the crankcase 2. A piston 7 is slidably mounted in the cylinder body 3 via a connecting rod 8.
The connecting rod 8 is connected to the crankshaft 9. A ring gear 10 having a predetermined number of teeth is mounted on the crankshaft 9, and a crank angle sensor 11 that also functions as an engine speed sensor for detecting a rotation position of the ring gear and measuring a crank angle and an engine speed is provided. . Cylinder head 4
A combustion chamber 13 is formed between and the piston 7. A combustion chamber pressure sensor 5 for detecting the combustion pressure in the combustion chamber 13 is provided on the cylinder head side. Cooling water jackets 6 are formed at appropriate positions on the cylinder head 4 and the cylinder body 3. An exhaust passage 15 and an intake passage 16 are communicated with the combustion chamber 13, and an exhaust valve 17 and an intake valve 18 are provided at the openings thereof. A catalyst 23 such as an exhaust gas purifying three-way catalyst is provided in the middle of the exhaust passage 15, and a muffler 24 is provided at an end thereof. An oxygen concentration sensor (O2 sensor) 25 and an exhaust pipe temperature sensor 120 are provided in the exhaust passage 15 and are connected to the control device 12, respectively.

A temperature sensor 26 is attached to the cylinder head 4, and temperature information of the combustion chamber 13 is sent to the control device 12. Further, the catalyst 23 is provided with a catalyst temperature sensor 150 connected to the control device 12. The key switch 43 of the engine is further connected to the controller 12 to obtain start information of engine drive control.

On the other hand, the intake pipe 16 is connected to each cylinder via an intake distribution pipe 28. An intake pipe pressure sensor 32 is attached to the intake distribution pipe 28, and intake pipe pressure information is sent to the control device 12
Sent to An EGR pipe 152 is provided by connecting the intake distribution pipe 28 and the exhaust passage 15. This EGR pipe 15
An EGR adjustment valve 151 connected to the control device 12 is provided on the upper side of the second side. An air cleaner 35 is connected to the intake distribution pipe 28 via an intake passage 33. The air cleaner 35 is provided with an intake air temperature sensor 36, and the intake air temperature information is sent to the control device 12. An intake air amount adjuster 30 having a throttle valve 29 mounted in the middle of the intake pipe 33.
Is arranged. The throttle valve 29 is provided with a throttle opening sensor 31.
1 is connected to the control device 12. This intake air amount regulator 30
A throttle valve bypass passage 37 is provided in a portion of the intake passage 33, and a bypass passage opening adjustment valve 38 is provided on the bypass passage 37.
Is provided. The bypass passage opening adjustment valve 38 is used for the control device 12
Linked to A heat ray type intake air amount sensor 34 is provided in the intake passage 33, and the intake air amount information is obtained by the control device 1.
Sent to 2.

An injector 105 is provided upstream of the intake valve 18 in the intake passage 16 for each intake port of each cylinder. The injector 105 is connected to the control device 12,
A control signal of the optimum injection amount calculated according to the operating state is sent. Fuel is sent to each injector 105 through a fuel pipe 101a connected to each cylinder. Fuel pipe 101
a is branched from the fuel distribution pipe 104, and the fuel distribution pipe 10
4, fuel is sent from a fuel tank 100 through a fuel supply pipe 101, a filter 102, and a fuel pump 103. The fuel not injected from the injector 105 is recovered in the fuel tank 100 through the fuel return pipe 107. A regulator 106 is provided on the fuel return pipe 107 to keep the fuel injection pressure constant.

FIG. 2 is a graph of the combustion chamber pressure for one cycle of combustion in the above four-cycle engine. The horizontal axis represents the crank angle and the vertical axis represents the combustion pressure. In this embodiment, the combustion pressures P0 to P0 at the six crank angle angles a0 to a5 are shown.
P5 is detected and PMI (mean indicated effective pressure) and combustion ratio are calculated based on these pressure values. a0 is the bottom dead center position (BDC) where the suction shifts to the compression shift, which is a state close to the atmospheric pressure. a1 is the crank angle after the spark ignition at S and before reaching the top dead center (TDC). a2-
The four points a5 are crank angles in the explosion stroke after top dead center. The PMI and the combustion ratio are calculated as described below based on the pressure data at these points.

FIG. 3 is a flow chart of a main routine for controlling various operating states of the engine including the calculation processing of the shaft torque and the combustion ratio according to the present invention. Each step will be described below.

Step S1: It is judged whether or not the main switch for stopping the engine is turned off while the engine is operating. If YES, the ignition device is immediately misfired and the fuel injection is stopped at the same time. If NO, the process proceeds to the next step S2.

Step S2: The information shown in the drawing is read from each sensor and the data is stored in each memory. The so-called engine load desired by the driver can be grasped as the accelerator position or the throttle opening. If the throttle opening and the engine speed are determined, the intake air amount is determined during steady operation, so the intake air amount can be directly detected and regarded as the engine load. Further, since the intake pipe negative pressure has a constant relationship with the throttle opening if the engine speed is determined, the intake pipe negative pressure can be detected and regarded as the engine load.

Step S3: Ignition timing data corresponding to two variables of accelerator position or throttle opening which is engine load (so-called engine load information intake air amount, intake pipe negative pressure may be used) and engine speed, empty The fuel ratio or fuel injection amount data, the fuel injection start timing data, and the EGR adjustment valve opening degree data are stored in the memory as a three-dimensional map, and the ignition timing and the fuel injection amount are directly mapped by the engine load information and the throttle opening degree information. From the above, each is calculated as a control amount basic value. When the air-fuel ratio data is stored as a three-dimensional map, the fuel injection amount is calculated from the detected intake air amount and the air-fuel ratio data.

The target combustion ratio is also stored as a three-dimensional map having so-called engine load and engine speed as variables, and the target combustion ratio is also calculated from the map.

Two-cycle engine described later (FIGS. 5 and 6)
In the above, the exhaust passage valve is also stored in the memory as a three-dimensional map with two variables of the engine load and the engine speed as variables, and is calculated from the map based on the engine load information and the engine speed information. The exhaust timing (compression ratio) variable valve opening is stored as a two-dimensional map in the memory with the engine speed as a variable, and is calculated from the map based on the engine speed information.

Step S4: When the intake air temperature is high, the air density is low, so the air flow rate is substantially reduced. Therefore, the air-fuel ratio in the combustion chamber becomes low. Therefore, a correction amount for reducing the fuel injection amount is calculated. Alternatively, since the combustion is likely to be delayed, a correction value for slightly advancing the ignition timing is calculated.

Further, the fluctuation correction of the indicated mean effective pressure is performed as follows. ΔPmi in the fluctuation value subroutine (FIG. 4)
When the variation amount is larger than the predetermined amount, the correction value for increasing the fuel injection amount or decreasing the EGR amount is calculated from the value of. This is because the fuel injection amount is increased or EG
This is because the output fluctuation decreases as the R amount decreases. However, if the fuel injection amount is increased or the EGR amount is decreased, the fuel efficiency deteriorates, so feedback control may be performed based on the absolute value of the indicated mean effective pressure. The indicated mean effective pressure absolute value correction is performed as follows.

The indicated mean effective pressure is calculated from the combustion chamber pressure information, stored in the memory, and compared with the indicated mean effective pressure stored in the immediately preceding main routine. Each correction value of the ignition timing, the fuel injection amount, or the EGR adjustment valve opening in the average effective pressure correction is slightly increased by a predetermined value based on the previous increase or decrease information in the memory with respect to the previous correction value in the memory. Alternatively, it is obtained as a value slightly reduced by a predetermined value. Replace this result with the value in memory.

On the other hand, if the pressure is lower than the indicated mean effective pressure stored in the immediately preceding main routine, based on the decrease or increase information obtained by reversing the previous increase or decrease information in the memory. , A predetermined value slightly decreased or a predetermined value slightly increased. Replace this result with the value in memory.

If it has not changed, the ignition timing,
Each correction amount of the fuel injection amount or the EGR adjustment valve opening is left as the previous correction value in the memory.

As the previous increase or decrease information in the memory, either increase or decrease is input at the time of engine start. Similarly, the indicated mean effective pressure in the memory is set to 0 when the engine is started.

Next, the combustion ratio will be described. The combustion rate until the crank angle becomes TDC is, for example, 25% to 3
Combustion stabilizes at 0%. That is, the combustion ratio calculated from the pressure data in the combustion chamber is compared with the target combustion ratio calculated in step S3, and based on this difference, the ignition timing, the fuel injection amount, the fuel injection timing, the EGR adjustment valve opening degree, 2 In a cycle engine, a control amount correction value for an exhaust timing variable valve, a compression ratio variable valve, an exhaust passage valve, etc. is set.

As the combustion ratio is smaller than the target combustion ratio, the ignition timing is advanced, the fuel injection timing is advanced, the fuel injection amount is increased, the exhaust timing is advanced, and the exhaust passage valve opening is decreased. The control amount is corrected as follows.

On the other hand, as the combustion ratio is higher than the target combustion ratio, the control amounts are corrected in the opposite directions.

When the temperature of the inner wall of the exhaust pipe is low, the temperature of the exhaust gas is also low. When the wall temperature becomes low, the propagation speed of the pressure wave becomes slow, and it becomes impossible to improve the engine output by utilizing the exhaust pipe pulsation.Therefore, the ignition timing is retarded or the air-fuel ratio becomes the predetermined value as the temperature becomes lower than the predetermined temperature. Below (17-1
8 or less), the correction value is set to increase the air-fuel ratio. With these, the exhaust gas temperature can be raised. When the temperature is higher than the predetermined temperature, the higher the temperature, the more the ignition is advanced and the correction value is set so as to lower the air-fuel ratio. The correction value of the fuel injection amount is calculated from the correction value of the air-fuel ratio, or the set value of the auxiliary air passage opening is calculated.

In a two-cycle engine, a correction value is set so that the exhaust timing valve advances as the temperature becomes lower than a predetermined temperature. The correction value is set so that the exhaust timing is retarded as the temperature is higher than the predetermined temperature. As a result, not only can the timing at which the exhaust pulsation reflected waves be matched be shifted, but the exhaust gas temperature can also be changed to match the predetermined temperature.

Next, the air-fuel ratio in the combustion chamber is obtained from the oxygen concentration information, and if it is higher than the air-fuel ratio in the memory (target air-fuel ratio), a correction value for increasing the fuel injection amount is calculated.

On the other hand, when it is lower than the air-fuel ratio (target air-fuel ratio) in the memory, the fuel injection amount is reduced or the auxiliary air passage opening is increased.

When the catalyst temperature is lower than a predetermined temperature (catalyst maximum activation temperature), the exhaust gas temperature is increased. As in the case of the exhaust wall temperature, the ignition timing and the correction value of the fuel injection amount are calculated, or the auxiliary air passage opening is set in some cases. Or E to increase EGR circulation amount
A correction value for increasing the GR adjustment valve opening is calculated.

Step S5: Steps S3 and S above
The control values for the ignition timing, the air-fuel ratio, and the injection start timing are calculated from the basic value and the correction value obtained in 4.

Step S6: The fuel injection end timing is determined from the control amount of the fuel injection start timing determined in step S3 and the control amount of the fuel injection timing determined in step S5.

Step S7: It is judged whether or not the engine is in the above operating state. That is, (a) Is there overspeed from the engine speed information detected in step S2? (B) Is there overheat from the engine temperature information detected in step S2? (C) Is there knocking from the knock information detected in step S2? (D) Is there oil empty from the remaining oil amount information detected in step S2? To determine. If there is an abnormality, the process proceeds to step S8, and if there is no abnormality, the process proceeds to step S9.

Step S8: If there is any abnormality, the control amount of the ignition timing is set to 0 for a predetermined time. As a result, the engine speed decreases because a certain rate of misfire occurs.

Step S9: When there is no abnormality, FIG.
The calculation result of the control amount is stored in the memory for the ignition control and the fuel injection control for each rotation cycle controlled by the subroutine.

Step S10: The EGR adjustment valve opening is set based on the control amount.

FIG. 4 is a flowchart of a subroutine that is interrupted or independently performed in the main routine for each combustion cycle in each cylinder of the engine. In step S11, the reference crank angle signal is fetched, and thereafter, the teeth of the ring gear are detected with reference to this signal and the crank angle is continuously fetched. On the other hand, the positive and negative pulses when passing through the teeth of the ring gear mounted on the crankshaft are detected, the engine speed is calculated based on this pulse, and this is stored in the memory.
The data of this memory is used in the main routine. Next, each time the crank angle read from the crank angle sensor 11 coincides with the above-mentioned 6 crank angles (a0 to a5 in FIG. 2), combustion pressure data is fetched and this data is stored in the memory (step S12). Then, step S
In 13, the ignition plug and the injector are driven based on the control amount in the memory (step S9 of the main routine) to ignite at a predetermined timing based on the crank angle read from the crank angle sensor 11, and the fuel is also discharged at a predetermined timing. The injection is started, and the fuel injection is ended at a predetermined timing similarly. Next, in step S14,
The indicated mean effective pressure PMIN is calculated from the combustion pressure data in the memory, and the combustion ratio qX and the heat generation amount QX are calculated,
Each calculation result is stored in the memory.

Further, the data of the indicated mean effective pressure PMIN-1 calculated in the previous cycle is read out and the difference from the current PMIN is obtained. This difference ΔPMI = PMIN-PMIN-1 is stored in the memory and the previous data PMIN-1 is erased.

As described above, the PMI is calculated by detecting the combustion chamber pressures (P0 to P5) at the crank angles of 6 points (a0 to A5) in one combustion cycle, and calculating the PMI from the linear approximation formula.
Is calculated. This approximate expression is represented by PMI = C + C1 * (P1-P0) + C2 * (P2-P0) + ... + C5 * (P5-P0). As can be seen from the above equation, PMI is represented by the pressure data P1 to P5 multiplied by a preset constant C1 to C5 and the preset constant C added. As described above, P0 (pressure data at BDC) is for offset output correction of the sensor such as drift, and the sampling angle of the crank angle differs depending on the engine model and the number of samples depends on the required accuracy.
The pressure (P1) before TDC and in the vicinity of the ignition timing is sampled and used for calculation, so that the calculation accuracy of PMI can be improved. In this calculation, the sign of the coefficient to the sample (P1) at BTDC is negative, and ATDC
The sign of the coefficient to the samples (P2 to P5) at is positive. Minus indicates negative work, plus indicates positive work.

In this embodiment, a0 = BDC, a1 = BT
DC15 °, a2 = TDC, a3 = ATDC15 °, a3
= ATDC 45 °, a4 = ATDC 75 °, a5 = ATD
C 105 °. Fix to low load at full load and low to high speed operation range.

The ignition timing depends on the change of the load and the low load 10
°, medium load 25 °, full load 5 °. As a result, the PMI is calculated by deleting the term of c1 * (p1-p0) in the first-order approximation formula in the low load region where a1 precedes ignition and the full load region.

In this case, the combustion ratio up to a3 = ATDC15 ° is calculated.

Alternatively, set a1 '= BTDC3 °,
The PMI may be calculated using the constants c ′ to c5 ′ instead of c to c5. In this case, the combustion ratio up to TDC is calculated over the entire load range.

Excluding the pressure detection point a0 for offset output correction due to drift or the like, an accurate PMI can be obtained by only one pressure detection point a1 in the BTDL.

The number of detection points in BTDC may be two or three. Thereby, the negative work can be calculated more accurately, and as a result, the PMI can be calculated more accurately. Moreover, since there are not many detection points, it is not necessary to make the tooth pitch of the ring gear for crank angle detection smaller than necessary, and it is possible to detect the crank angle at low cost and with high accuracy.

The load is further divided into low load, medium load and full load, and the engine speed is divided into low speed, medium speed and high speed, and N = 1 for a0N to a5N and c0N to c5N depending on the combinations.
Alternatively, the PMI may be measured and calculated based on nine types of data (9 to 9).

As described above, PM of the previous cycle
The difference ΔPMI from I is obtained, and the fuel injection amount and the ignition timing EGR amount are controlled so that the difference becomes close to the target value set by the operating parameter. By reducing the amount of fuel or increasing the amount of EGR, fuel consumption and exhaust gas are expected to improve, but on the other hand, combustion becomes unstable and output fluctuations increase, leading to deterioration of drivability. In the conventional control, the output fluctuation is suppressed by controlling the air-fuel ratio and the EGR amount to preset values. However, the influence of the air-fuel ratio and the EGR amount on combustion differs depending on the usage environment, and it is necessary to secure a considerable safety factor for setting. In the present invention, by monitoring the fluctuation of the PMI equivalent to the output, it becomes possible to operate the air-fuel ratio and EGR up to the allowable value limit of the output fluctuation. In this case, it is necessary to know the amount of operation required to reach the limit in order to control the limit value. Therefore, in the present invention, the operation target is operated so as to constantly vibrate the limit value of the ΔPMI fluctuation.

As described above, in this embodiment, the pressure value before top dead center is multiplied by a negative coefficient, and the work before top dead center is treated as a negative work. As a result, even when the intake air amount changes or the combustion is fast and the combustion is performed before the top dead center, it is possible to cope with the change and the PMI can be predicted in a wide operating range. The shaft torque is calculated from the PMI, the engine speed, the piston diameter, and other dimensions of engine parts and the number of cylinders.

FIG. 5 is a block diagram of a two-cycle engine to which the present invention is applied. Similar to the four-cycle engine in FIG. 1, a connecting rod 246 is connected to the crankshaft 241 and a combustion chamber 248 is formed between the piston at the tip of the connecting rod 246 and the cylinder head. An engine speed sensor 267 and a crank angle detection sensor 258 for detecting a mark of a ring gear mounted on the crankshaft to detect a reference signal and a crank angle are provided in the crankcase. A crank chamber pressure sensor 210 is provided on the crankcase. The air-fuel mixture is sent to the crank chamber from the intake manifold via the reed valve 228. Air-fuel mixture is sent from the air cleaner 231 to the intake manifold via the throttle valve 204 of the carburetor. An intake pipe pressure sensor 211 is attached to an intake passage downstream of the throttle valve that communicates with the intake manifold. The throttle valve 204 is operated by a grip 206 connected by a wire 205 via a throttle pulley 203. The grip 206 is the steering wheel 20.
The accelerator position sensor 202 is attached to the end portion of the No. 7 and has a root portion thereof. 212 is a throttle opening sensor.

A scavenging port 229 is opened in the cylinder to connect the combustion chamber and the crank chamber via a scavenging passage 252 at a predetermined position of the piston. Further, an exhaust port 254 is opened in the cylinder and an exhaust passage 253 communicates with it. An exhaust timing variable valve 264 is mounted on the exhaust passage wall near the exhaust port. The variable valve 264 is driven by an actuator 265 composed of a servo motor or the like to change the opening position of the exhaust port and adjust the exhaust timing. The exhaust pipe pressure sensor 21 is installed in the exhaust pipe forming the exhaust passage 253.
3 and an exhaust pipe temperature sensor 223 are provided. An exhaust passage valve 281 is provided in the exhaust passage and is driven by an actuator 282 including a servomotor or the like.
The exhaust passage valve 281 is throttled in the low speed range to prevent blow-through and to stabilize the rotation.

A knock sensor 201 is provided on the cylinder head.
Is attached, and the spark plug and the combustion chamber pressure sensor 200 are attached so as to face the combustion chamber. The spark plug is connected to the ignition control device 256. An injector 208 is attached to the side wall of the cylinder. Injector 2
Fuel is sent to 08 through a fuel delivery pipe 209.

Further, a combustion gas chamber 279 is formed in the cylinder block so as to communicate with a portion closer to the cylinder head than the exhaust port opening of the cylinder bore and an intermediate portion of the exhaust port through a communication hole 278. This communication hole is set so that the combustion gas containing almost no blow-through gas is introduced into the combustion gas chamber in the explosion stroke.
An O2 sensor 277 for detecting the oxygen concentration in the combustion gas is installed in the combustion gas chamber. In addition, a check valve (not shown) is arranged at the introduction part to the combustion gas chamber and the discharge part to the exhaust port to prevent the flow in the opposite direction.

Driving of such an engine is controlled by a control device 257 having a CPU 271. On the input side of the control device 257, the above-mentioned combustion chamber pressure sensor 20
0, knock sensor 201, accelerator position sensor 20
2, crank chamber pressure sensor 210, intake pipe pressure sensor 2
11, the throttle opening sensor 212, the exhaust pipe pressure sensor 213, the crank angle detection sensor 258, the engine speed sensor 267, and the O2 sensor 277 are connected. Further, on the output side of the control device 257, an injector 208 and an actuator 26 for an exhaust timing adjusting valve are provided.
5, an exhaust valve actuator 282, an oil supply device (not shown), etc. are connected.

FIG. 6 is a graph of combustion chamber pressure similar to that of the above-mentioned four-cycle engine (FIG. 2) for showing the combustion pressure data detection points for measuring the axial torque of the above-mentioned two-cycle engine. As mentioned above, combustion chamber pressure data is sampled at 6 crank angles. A in the figure
The range of B is the crank angle region where the exhaust port is open, and the range of B is the crank angle region where the scavenging port is open. The method of calculating and calculating each crank angle (a0 to a5) is substantially the same as that of the above-described four-cycle engine. However, it is better to delay a0 from the case of 4 cycles, for example, BTDC135 °, and advance a5 to the case of 4 cycles, such as ATDC90 °. Each of the embodiments of the present invention can also be adopted in an engine that supplies fuel from a carburetor in the intake passage.

[0060]

As described above, in the present invention, the PMI is calculated from the pressure data including the combustion chamber pressure of the engine near the ignition timing before the top dead center, and the accurate PMI can be obtained. Furthermore, based on this, fuel injection, ignition timing, EG
Since R is controlled, an accurate control amount can be calculated easily and in a short time, responsiveness is improved, and lean combustion with a high air-fuel ratio is performed even when performing EGR in which output fluctuation easily occurs. In the above, the output fluctuation of the engine can be suppressed, and appropriate ignition timing control and air-fuel ratio control can be performed according to the combustion state and the operating state.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a 4-cycle engine to which the present invention is applied.

FIG. 2 is a graph of combustion chamber pressure for the engine of FIG.

FIG. 3 is a flow chart of a main routine of engine control according to the present invention.

FIG. 4 is a flowchart of an engine control subroutine according to the present invention.

FIG. 5 is a configuration diagram of a two-cycle engine to which the present invention is applied.

FIG. 6 is a graph of combustion chamber pressure for the engine of FIG.

[Explanation of symbols]

 2: Crank chamber 3: Cylinder body 4: Cylinder head 7: Piston 9: Crankshaft 25: O2 sensor 31: Throttle opening sensor 32: Intake pipe pressure sensor 34: Intake air amount sensor 150: Catalyst temperature sensor

Claims (3)

[Claims] 1. A crank angle from the end of the exhaust stroke to the beginning of the compression stroke, a crank angle after the crank angle and after spark ignition and before top dead center, and from the compression step to the expansion step. A method for measuring an output of an engine, which detects a combustion chamber pressure at a dead angle or near a top dead center and a crank angle after the top dead center, and calculates an indicated mean effective pressure or a shaft torque based on the combustion chamber pressure data. 2. A method for controlling a spark ignition engine, characterized in that the operating state of the engine is controlled based on the indicated mean effective pressure or shaft torque calculated by the method of claim 1. 3. The calculated mean effective pressure or shaft torque is calculated for each cycle of combustion, a difference from the calculation result in the previous cycle is calculated, and the operating state is controlled based on this difference. The method for controlling a spark ignition type engine according to claim 2.