JP2001012293A - Misfire deciding method for multicylinder engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a misfire deciding method for a multicylinder engine obtaining a desired optimum operating characteristic corresponding to an operating region, by performing misfire decision in accordance with a load while high accurate lean combustion control can be performed in each cylinder by deciding a misfire in each cylinder of the multicylinder engine. SOLUTION: An exhaust pressure waveform of an engine formed by a plurality of cylinders is detected to be discriminated in each cylinder, an area of the exhaust pressure waveform in a prescribed crank angle range of each cylinder is calculated, this area is compared with a reference area value, a difference or ratio thereof is calculated, a value of this difference or ratio is compared with a prescribed reference-value, and a misfire is decided in each cylinder.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a misfire determination method for a multi-cylinder lean-burn engine or the like.

[0002]

2. Description of the Related Art Japanese Patent Laid-Open No. 10-13179 discloses a lean-burn control method for an internal combustion engine for the purpose of purifying exhaust gas and improving fuel efficiency by reliably detecting a misfire state in a multi-cylinder engine.
No. 7 proposes this.

[0003] In the control method described in this publication, in a lean combustion control method for a gas engine provided with a crank angle sensor, an exhaust pressure sensor and a fuel control valve, an integral value of an exhaust pressure waveform obtained for a predetermined crank angle range is used. Comparing the average value of the integral value of the exhaust pressure waveform obtained for a predetermined crank angle range for the preceding combustion cycle, and determines that a misfire has occurred if the difference or ratio between the two exceeds a predetermined value;
The misfire prevention control for enriching the air-fuel mixture is performed by opening the fuel control valve by a predetermined unit until it is determined that a misfire has occurred or until the opening immediately before the misfire has occurred.

[0004]

However, according to the misfire determination method in the lean burn control method for an engine described in the above-mentioned publication, if any one of the cylinders of a multi-cylinder engine has a misfire, the occurrence of the misfire is accurately determined. However, it does not determine which cylinder is misfiring, and it is not possible to perform high-precision fuel control for all cylinders for each cylinder.

Further, since the reference value for judging misfire does not take into account the throttle valve opening degree, it is desired to prioritize a desired operating characteristic according to the load range and change the degree of leaning according to the operating characteristic. For example, the misfire determination cannot be made to sufficiently correspond to the operating range. For this reason, the fuel is always used when it is desired to obtain the best operating state suitable for each area in preference to lean combustion, such as a high load operation area where it is desired to secure output and a low load area where combustion is stabilized. Since the fuel is diluted near the maximum misfire limit, the desired operating characteristics cannot be obtained, and the combustion state of the optimum operating characteristics required according to the operating region cannot be sufficiently achieved.

The present invention has been made in consideration of the above-mentioned prior art, and determines misfire for each cylinder of a multi-cylinder engine, enables highly accurate lean burn control for each cylinder, and reduces load and engine speed. It is an object of the present invention to provide a misfire determination method for a multi-cylinder engine that performs a misfire determination in accordance with an operation range and obtains a desired optimum operation characteristic corresponding to an operation region.

[0007]

In order to achieve the above object, according to the present invention, an exhaust pressure waveform of an engine comprising a plurality of cylinders is determined and detected for each cylinder, and the exhaust pressure waveform is determined within a predetermined crank angle range of each cylinder. The area of the exhaust pressure waveform is calculated, this area is compared with a reference area value to calculate the difference or ratio, and the difference or ratio value is compared with a predetermined reference value to determine misfire for each cylinder. A misfire determination method for a multi-cylinder engine is provided.

According to this configuration, the exhaust pressure (pressure of exhaust gas in the exhaust pipe) waveform is detected for each cylinder of the multi-cylinder engine, and the exhaust pressure waveform is analyzed for each cylinder to calculate a waveform area. Since misfire is determined for each cylinder by comparing with a reference value based on the misfire, it is possible to reliably determine misfire for each cylinder for all cylinders, and based on this, highly accurate lean burn control can be performed for each cylinder.

In a preferred embodiment, the determination of each cylinder is performed based on a pulsar signal for detecting camshaft rotation and a crank angle signal for detecting crankshaft rotation.

According to this configuration, the pulsar coil for detecting the rotation of the camshaft that rotates in synchronization with the crankshaft is set in advance in a predetermined cylinder so that the pulsar signal and the crank for the pulsar signal are set. Based on the crank angle signal whose angle can be determined, it becomes possible to determine the cylinder of the exhaust pressure waveform according to the crank angle of the exhaust pressure waveform.

In a further preferred embodiment, the reference area value is an average value of the areas of a plurality of discharge pressure waveforms immediately before the discharge pressure waveform to be determined for each cylinder.

According to this configuration, the area of the exhaust pressure waveform detected for each cylinder is compared with the average value of the exhaust pressure waveform areas of a plurality of cycles immediately before the preceding cylinder for that cylinder. Misfire can be determined.

In a further preferred embodiment, the reference value is set in a map corresponding to the engine speed and the throttle opening, and a different reference value is set for each area of the map.

According to this configuration, an optimal reference value can be set for each operating region corresponding to the coordinate position of the map in the map in which the coordinate position is determined based on the engine speed and the throttle opening. Thus, it is possible to perform an accurate misfire determination in accordance with the above, and to execute optimal fuel control for each operation region.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram of a gas engine heat pump air conditioning system to which the present invention is applied.

This air conditioning system comprises an outdoor unit 60 and a plurality of indoor units 61 (only one is shown in the figure), in which the gas engine 1 is provided.
The heat pump refrigerant cycle 2 driven by the gas engine 1 includes an outdoor unit 60 and an outdoor unit 61.
Composed across

The gas engine 1 has an intake passage 4 connected to an air cleaner 3, and a mixer 5 is provided on the intake passage 4. A throttle valve 6 is provided downstream of the gas mixing section of the mixer 5, and adjusts the amount of a mixture of outside air and gas fuel that is taken in from the intake port 18 and supplied through the air cleaner 3. A fuel supply pipe 7 is connected to a gas mixing section of the mixer 5 to form a gas mixture. A gas fuel control valve 8 for adjusting the flow rate of gas fuel supplied to the mixer 5 and a zero governor 9 for adjusting gas pressure to atmospheric pressure are provided on the fuel supply pipe 7. (Not shown). The gas fuel control valve 8 is feedback-controlled by the CPU as described later.

An exhaust pipe 12 is provided on the exhaust side of the gas engine 1. An exhaust gas catalyst 13 and an exhaust gas heat exchanger 14 are provided on the exhaust pipe 12, and a silencer 15 and a drain separator 16 are further provided downstream thereof. Exhaust gas is discharged from an exhaust outlet 17. The drain separator 16, the silencer 15, and the exhaust gas heat exchanger 14 are connected to a neutralizer 19, which neutralizes the acidic drain water to form a drain outlet 2.
Discharge from 0 to the outside.

An oil tank 22 is connected to an oil pan 21 at the bottom of the gas engine 1, and oil is supplied by an oil supply pump 23. The oil circulates through the engine by an oil pump (not shown). Reference numeral 11 denotes an oil separator for separating oil in the blow-by gas.

Two compressors 25 are connected to a crankshaft (not shown) of the gas engine 11 via a clutch 24. Each compressor 25 is connected to a refrigerant inlet pipe 27 and a refrigerant outlet pipe 28 through which a refrigerant made of de-fluorocarbon gas or the like circulates. A flexible pipe 26 is interposed in the refrigerant inlet pipe 27 and the refrigerant outlet pipe 28 around the compressor in order to arrange the pipes compactly and to absorb stress and vibration. An oil separator 29 is mounted on the refrigerant outlet pipe 28 side, and is connected to the four-way valve 30 on the downstream side. The oil separator 29 separates oil and liquid refrigerant from the compressed refrigerant gas, and returns them to the accumulator 35 through the return pipe 33. The four-way valve 30 has four ports a, b, c, and d, and the connection between the ports is switched during cooling and heating.

During heating, as shown, port a and port b are connected, and port c and port d are connected. As a result, the compressed refrigerant gas discharged from the compressor 25 is condensed through the indoor heat exchanger 31, and the condensed heat is released into the room to heat the room. The condensed refrigerant is decompressed through the expansion valve 52 and evaporates through the outdoor heat exchanger 32 via the HIC 51. The evaporated refrigerant passes through the ports c and d of the four-way valve 30 and enters the accumulator 35 via the plate heat exchanger 34 or the bypass pipe 45. A sub-accumulator 46 is provided in parallel with the accumulator 35. The refrigerant of the accumulator 35 is the capillary tube 4
8, 49, 50 and the refrigerant inlet pipe 2 through the throttle 47 and the like.
7 sucks into the compressor 25.

Reference numeral 80 denotes a refrigerant pipe extending from the four-way valve 30 to the expansion valve 52 via the indoor heat exchanger 31.
Reference numeral 1 denotes a refrigerant pipe extending from the expansion valve 52 to the subcool outdoor heat exchanger 32a via the HIC 51, and reference numeral 82 denotes a refrigerant pipe which diverges from the subcool outdoor heat exchanger 32a, joins via the outdoor heat exchanger 32, and reaches the four-way valve 30. Refrigerant pipe until
Reference numeral 3 denotes a refrigerant pipe 81 from an intermediate portion of the refrigerant pipe 81 via an open / close valve 83a functioning as an electronic expansion valve when opened and the HIC 51.
It is a bypass pipe to the middle part of.

During cooling, the ports a and c of the four-way valve 30 are connected, and the ports b and d are connected. As a result, the compressed refrigerant gas is condensed in the outdoor heat exchanger 32 before passing through the ports a and c in reverse to the time of heating, passes through the expansion valve 52, evaporates in the indoor heat exchanger 31, and cools the room. Thereafter, the accumulator 3 passes through the ports b and d of the four-way valve 30.
Return to 5.

The subcool outdoor heat exchanger 32a
Functions as a condenser for further supercooling the refrigerant condensed and liquefied in the three outdoor heat exchangers 32 arranged in parallel. The HIC 51 on the refrigerant pipe is a heat exchanger for reducing pressure loss for improving COP (refrigerant coefficient of performance). That is, during the cooling operation, when the required load on the outside of the room is small and the high-pressure refrigerant is bypassed to the low-pressure side refrigerant pipe 80 through the bypass pipe 83, the on-off valve 83a is opened and a desired throttle opening degree is obtained. The HIC 51 heat-exchanges the low-pressure low-pressure refrigerant with the high-pressure high-temperature liquid refrigerant to further supercool (subcool) the high-pressure side, while functioning to assist the evaporation of the refrigerant on the low-pressure side.

The plate heat exchanger 34 is for heating the refrigerant introduced into the accumulator 35 with high-temperature engine cooling water along the piping. The plate heat exchanger 34 is provided with a bypass pipe 45 to reduce pressure loss during cooling and improve COP.

The gas engine 1 is provided with a cooling water system 39, and cooling water is circulated by a cooling water pump 40. The cooling water sent by the cooling water pump 40 is supplied to the exhaust heat exchanger 14.
And is sent to the cooling jacket (not shown) of the engine by the second pump 41. A thermostat 42 is provided on the cooling water pipe on the outlet side from the engine to bypass the cooling water during a warm-up operation or the like. The cooling water system 39 is provided with a linear three-way valve 43 on the pipe on the engine outlet side, and a radiator 36 is provided in parallel with the outdoor heat exchanger 32 on the downstream side thereof. The radiator 36 is connected to a recovery tank 38. The linear three-way valve 43 allows the cooling water to flow to the radiator 36 side during cooling and dissipates heat by the fan 37 during cooling, flows to the plate heat exchanger 34 side through the branch pipe 44 during heating, and cools the high-temperature cooling water by heating the refrigerant. I do.
The amount of branching to the radiator 36 side and the plate heat exchanger 34 side can be adjusted and controlled.

FIG. 2 is a configuration diagram of a control system of the air conditioning system having the above configuration. System CP that controls the entire system
U70 includes a memory 72 storing a control map of the opening degree of the fuel valve, which will be described later, and is connected to an engine CPU 71 for driving and controlling the gas engine.

The system CPU 70 includes an indoor unit 61
It is connected to an operation unit provided on the side, and operation conditions such as operation mode switching and set temperature are input. Also, the system CPU
70 is a high-pressure saturation temperature sensor provided in the indoor unit, a high-pressure side refrigerant pressure sensor 77, a low-pressure side refrigerant pressure sensor 78 provided in the indoor unit and the outdoor unit 60, an outside air temperature sensor, a low-pressure saturation temperature sensor, and an accumulator liquid. Various detection data from the surface level sensor, the compressor temperature sensor 75, and other sensor groups are input, and based on these input data, the indoor unit fan and expansion valve of the indoor unit 61 and the four-way valve 30 and the linear three-way valve of the outdoor unit 60 43, drive control of the outdoor unit fan 37 and other valve groups.

The engine CPU 71 includes an exhaust pressure sensor 73,
Various operation state data is input from a group of sensors such as a camshaft pulser, a crankshaft sensor, a throttle opening sensor, a clutch signal, an exhaust temperature sensor, and a cooling water temperature sensor 76, and predetermined based on these operation state data. In accordance with the program, the ignition control circuit is driven to operate the ignition coil and spark the spark plug by arithmetic processing using a map or the like. Further, the throttle valve rotation actuator is driven to control the amount of intake air, and the fuel intake opening / closing valve operation actuator is driven to drive the fuel opening / closing valve 1.
0, and controls the fuel supply amount by driving the fuel control valve actuator.

FIG. 3 is a flowchart of a main program of the fuel control valve feedback control method according to the embodiment of the present invention. When the driving operation is started, first, each valve and the actuator are initialized (Step S).
1). It is determined whether or not the engine has started (step S2), and upon completion of the start, a target engine speed is calculated (step S3). This is performed using a map determined in advance based on the difference between the set temperature input from the operation unit (FIG. 2) of the indoor unit 61 and the temperature detected by the indoor temperature sensor.

Subsequently, a misfire determination program is executed (step S4). This is a program for monitoring misfire that is always performed during engine operation, separately from misfire control by fuel control valve feedback control described later.

Next, the throttle opening for calculating the target engine speed calculated in step S3 is calculated, and the throttle valve 6 (FIG. 1) is feedback-controlled (step S5). Next, it is determined whether or not the feedback control of the fuel control valve 8 (FIG. 1) described later according to the present invention is being performed based on the presence or absence of the feedback control flag (step S6).
7) If not executed, the opening of the fuel control valve is calculated based on a map (a base map described later) and used as a target value for feedback control (step S7).

Next, a misfire control program for rewriting the base map by learning is performed as described later (step S).
8). When the misfire determination is completed, it is determined whether there is an engine stop command (step S9). If the engine is not stopped, the routine from step S2 is repeated.
If the engine is stopped, an engine stop program for stopping each device in a predetermined order is executed (step S1).
0).

FIG. 4 is a flow chart of the fuel control valve feedback control for reducing the fuel for NOx countermeasures by the learning program. When a subroutine called every unit time is started from the main routine, first, a current position and a plane complemented value in a map are calculated from detection data of the throttle valve opening and the engine speed (step S11). At this time, the calculation is performed based on both the base map of the fuel control valve and the rewrite map by learning. This value is compared with the value of the immediately preceding cycle (step S12). If the difference is larger than the predetermined value, the FB execution flag is turned off without performing the lean control for each step by the feedback (FB) control described later.
Then, both the timer A and the timer B described later are turned off (step S22).

If the difference is equal to or less than the predetermined value, it is determined whether or not the FB control is to be executed based on the detected coolant temperature and operating state data (step S13). For example, FB during warm-up
No control is performed. Next, it is checked whether the FB control has actually been started (step S14). If it has not started, immediately perform a one-step lean operation,
Set the execution flag. If the FB is being executed, it is determined whether or not a lean operation is currently being performed (step S15).

If it is not during the lean operation, it is determined that a later-described stabilization waiting time is in progress, and the flow advances to step S23 to determine whether or not the stabilization time has expired based on whether or not a set time of a later-described timer B has been reached. If the timer set time has not been reached, the routine is repeated until the timer set time is reached. When the set time has reached the timer set time, the map rewriting process is performed (step S24).

If a lean operation is being performed in step S15, a misfire determination program is executed (step S16). In this misfire determination program, misfire is detected (step S17). This misfire determination is performed by analyzing a detection waveform from an exhaust pressure sensor of the engine, as described later.

If no misfire is detected, it is checked whether the lean time has elapsed (step S18). This lean time check is performed in a subsequent lean process (step S1).
It is determined whether or not the set time of the timer A set in 9) has been reached. When the lean time has elapsed, the fuel control valve is set to lean one step (step S19).
At the same time, the timer A is set to a predetermined lean time. Subsequently, an FB execution flag is set to indicate that the FB is being executed (step S20).

Next, it is checked whether the number of steps after the lean operation is larger than the value of the second map (whether the operation is leaner than the second map) (step S21). If it is, the routine is repeated and the fuel control valve is gradually leaned one step at a time. When the value of the second map is reached without causing a misfire by leaning one step at a time, a stable time process is performed (step S27). In this stabilization time processing, the timer B is set to a predetermined stabilization time and the stabilization processing starts.

When this stabilization time is over, it is determined in step S15 that the stabilization time is awaited. After the set time by the timer B is over, the value of the base map is rewritten to the value of the second map which has been confirmed not to misfire. Can be

On the other hand, if a misfire is detected during leaning one step at a time, the process immediately shifts to the enrichment operation in step S17, and the fuel is enriched for a predetermined N steps. This is to recover the misfire. This enrichment amount is calculated based on the enrichment map (step S25). After calculating the enrichment amount, it is determined whether the value is equal to or less than the base map (lean side) (step S26). If it is larger than the base map, the current FB control is invalidated and the FB execution flag is lowered (step S28). This is to prevent rewriting to a richer side than the base map which is known not to misfire.

Subsequently, the gas flow control valve opening value corresponding to the map value is returned to the value of the base map, and a permanent flag is set to the map value (step S29). As a result, when the control is subsequently performed in the operating state of the map position, the fuel control is immediately performed based on the original base map in which the permanent flag is set, without performing rewriting by learning of leaning.

If it is determined in step S26 that the calculated value is equal to or smaller than the base map, a stabilization time is set, and the mode shifts to the stabilization control mode (step S27). This stable time is maintained for a predetermined time by starting the timer B. When the stabilization time ends, this is determined in the above-described step S23, and the value of the misfire (or N
The base map is rewritten with the value on the rich side only for the step).

In this rewriting process, not only the map position but also the entire map area is rewritten by the number of steps lower than the base map at the map position under control. In this case, if the number of rewrite steps is lowered to the lean side at another position and the second map is reached,
At that position, the value is rewritten to the value of the second map without being lowered below the second map.

Also, the original base map is stored as it is, a map for rewriting is prepared, and the learned values are sequentially written in the rewriting map and used as a new base map.

FIG. 5 is a flowchart of the map rewriting process. This is the flow of the map rewriting step S24 in FIG. 4 described above. First, step S in FIG.
Similar to 11, the current position of the map is calculated from the engine speed and the throttle opening (step S30). A permanent flag is set at this current position (step S31). Next, the current fuel control valve opening is subtracted from the base map calculation value, and that value is used as an offset value (step S3).
2).

In step S33, when rewriting the entire rewriting map, a rewriting counter is prepared and this counter is cleared. The map coordinates in this counter are (x, y), and are initialized to (0, 0) in this process.

In step S34, it is checked whether a permanent flag is set in the rewrite map of the (x, y) coordinates. If there is a permanent flag, the data at this coordinate position is not rewritten. In step S35, it is checked whether or not a non-target flag is set in the rewrite map of the (x, y) coordinates, which is an area where the feedback control is not performed. If there is a non-target flag, the data at this coordinate position is not rewritten. In step S36, the offset value is subtracted from the base map value at the (x, y) coordinates. This subtracted value is (x,
y) It is checked whether the coordinates are equal to or greater than the second map value (step S37).

If the offset subtraction value is equal to or larger than the second map value (richer than the second map value), the offset subtraction value is written to the (x, y) coordinates of the rewrite map (step S38).

On the other hand, if the offset subtraction value is less than the second map value (lean side from the second map value), (x, y)
The coordinate rewriting map value is rewritten to the second map value.
(Step S39). When the number of map counters reaches the number of all maps, the rewriting operation ends (step S4).
0).

FIG. 6 is a flowchart of the misfire determination. First, the current position of the map is calculated from the data of the engine speed and the throttle opening (step S4).
1).

Next, in step S42, a cylinder discriminating process is performed. This cylinder determination process is performed to determine the misfire state for each cylinder. This cylinder discrimination is performed based on a pulsar signal from a camshaft sensor and a pulse signal corresponding to a crank angle from a crank angle sensor, as described later.

In step S43, the waveform data from the exhaust pressure sensor is taken in, and the area of the waveform between the predetermined crank angles t1 and t2 is calculated. In step S44, it is checked whether the waveform area is equal to or smaller than a predetermined value. This predetermined value is used to check for an abnormality in the sensor, and is set to a value that is small enough to exceed the amount of area reduction due to misfire, for example.

If the waveform area is equal to or smaller than the predetermined value, a timer or a counter for the number of cycles is set in step S45. In step S46, it is checked whether or not waveform data of the same small area equal to or less than a predetermined value is input during a predetermined period of time by the timer or a predetermined number of times by the counter. After the predetermined time has elapsed or the predetermined number of times has been detected, if the exhaust pressure waveform area is still equal to or smaller than the predetermined value, it is determined that the exhaust pressure sensor is abnormal and a warning display of the exhaust pressure sensor abnormality is displayed (step S47).

Subsequently, an emergency operation flag is set in step S48, and the engine is driven without fixing the fuel control valve to the original base map operation program without performing FB control (step S49).

If the area value is equal to or larger than the predetermined value and there is no abnormality in the sensor in step S44, an area moving average value of the waveform from the exhaust pressure sensor at the crank angles t1 to t2 is calculated for each cylinder (step S50). ).

In step S51, the ratio R of the waveform area of the exhaust pressure sensor to the cylinder moving average area is calculated.
In step S52, it is checked whether the ratio R of each waveform area data to the average value is equal to or less than a reference value. The reference value differs depending on the operation range, and misfire is determined for each cylinder based on the reference value. If no misfire has occurred, in step S53, the waveform moving average value of the cylinder-specific exhaust pressure sensor is rewritten with the current waveform data.

If the waveform area ratio R is equal to or less than the reference value, it is determined in step S54 that a misfire has occurred. This misfire determination is made for each cylinder.

A step S55 checks the number of misfired cylinders. For example, if two or more of the four cylinders have misfired, it is determined that the engine is abnormal and the engine is forcibly stopped (step S59). Thereafter, the display of the engine abnormality is performed (step S60).

If the number of misfiring cylinders is one, it is checked in step S56 whether the FB control operation is being performed. If the FB control is being performed, the process returns to the misfire detection step S17 after the misfire determination program (step S16) in FIG.

If the number of misfiring cylinders is one and the FB operation is not being performed, an emergency flag is set in step S57. continue,
In step S58, a control operation for misfire recovery is performed. This is performed, for example, by enriching the opening map of the fuel control valve or changing the ignition timing of the misfiring cylinder.

FIG. 7 is an explanatory diagram of an engine operation area according to the throttle opening and the engine speed. It is desirable to change the fuel control method according to the operating range in order to obtain an optimal operating state in the entire engine operating range.
For example, in region I on the low load side where the throttle opening is small, leaning is suppressed to ensure stable combustion.
In the intermediate region II, the fuel control valve feedback control for misfire determination is performed with priority given to exhaust gas measures or combustion efficiency. In the high load region III, the fuel control valve feedback control is not performed to secure the output.

In the present invention, the second map is provided together with the base map of the fuel control valve opening, and the base map is rewritten while making the fuel lean by learning.

Table 1 shows an example of a second map setting method in consideration of the driving characteristics required according to such a driving region.

[0065]

[Table 1]

In the second map, drivability is prioritized in a region where the throttle opening is low (A region), and reduction of exhaust gas (NOx) is prioritized (B region) or operation efficiency is prioritized (D in the intermediate opening). Area), and with a high opening, priority is given to ensuring output (area C).

FIGS. 8A and 8B are graphs showing data examples of the cylinder discrimination waveform and the misfire discrimination waveform. FIG.
As shown in (A), a pulsar signal a from a pulsar coil that detects the rotation of the camshaft is used for two rotations of the crankshaft (7
20 degrees). The crank angle pulse signal b from the crank angle sensor is input in synchronization with the pulsar signal a. This crank angle signal is output every time each tooth of a ring gear having, for example, 120 teeth is detected.
There are no pulse signals, and one pulse is input every 3 degrees of crank angle. The detection position of this pulser signal is set to, for example, 90 degrees BTDC of the # 1 cylinder. Thus, for example, in a four-cylinder engine that is ignited in the order of # 1, # 3, # 4, and # 2, for example, the crank from the pulser signal detection position is detected for each of the four cylinders whose exhaust pressure is detected every 90 degrees. The cylinder number is determined based on the angle.

Since the combustion conditions of each cylinder are slightly different from each other, the discharge pressure waveform of each cylinder is also different. According to the present invention, an optimal feedback control can be performed in accordance with the exhaust pressure waveform of each cylinder by discriminating the cylinder and determining misfire for each cylinder.

FIG. 8B shows exhaust pressure detection data of four cylinders. A solid line graph c is a normal exhaust pressure waveform, and a dotted line graph d is a misfire exhaust pressure waveform. From such waveform detection data, the area of the waveform is calculated for each cylinder, and misfire is determined based on the waveform area. In this case, the integration start crank angle t1 and the integration end crank angle t2 after the compression top dead center are set in the waveform data of each cylinder.

At a predetermined crank angle, a predetermined cylinder is ignited,
Exhaust gas reaches an exhaust pressure sensor part in the exhaust pipe through an explosion and an exhaust stroke. T1 and t2 are set for each cylinder corresponding to the ignition timing of each cylinder so that the exhaust pressure data can be captured with the peak of the exhaust pressure waveform interposed in consideration of the crank angle (depending on the engine speed) until the exhaust gas reaches. I will decide.

The waveform area between the crank angles t1 and t2 is calculated for each cylinder, and is compared with the moving average value of the immediately preceding predetermined cycle. The ratio R of this waveform area to the average value
Is compared with a reference value stored in the map to determine misfire. This reference value differs for each coordinate of the map corresponding to the driving area.

FIG. 9 is a three-dimensional diagram showing a map of reference values for misfire determination. As shown, the misfire determination criterion (%) differs depending on the map coordinate position according to the throttle opening and the engine speed. In this example, the misfire determination criterion is low on the high throttle side and high throttle opening side, and high on the low rotation and low throttle opening side. Therefore, on the high rotation and high load side, the above-described exhaust pressure waveform area is greatly reduced as compared with the average value. In a high load region of, for example, 2,000 rpm or more, the misfire is not determined unless the ratio R becomes smaller than 20% or less. Conversion continues. On the other hand, on the low rotation and low load side, when the ratio R of the exhaust pressure waveform area becomes 30 to 40%, it is determined that a misfire has occurred, and the leaning is stopped.

As described above, by changing the misfire determination criterion according to the operating range, the above-described second map is formed for each operating area in accordance with the desired priority characteristic.
An optimal operating state is obtained over the entire operating range.

The ratio R to the average value of the discharge pressure waveform area
, And comparing this with a reference value, a difference between the discharge pressure waveform area and the average value is determined and this difference is determined in advance by a predetermined reference value (this reference value also varies depending on the operation region). The misfire may be determined by comparing with.

In this embodiment, the fuel gas that has passed through the flow control valve 8 is mixed with air in the mixer 5, and the flow rate of the mixer is adjusted by the throttle valve 6 in the mixer 5. Is sucked. Therefore, the air-fuel ratio of all cylinders is uniformly controlled by adjusting the fuel gas amount by the flow control valve 8. Therefore, the misfire recovery of the misfiring cylinder as a result of the misfiring determination for each cylinder can be effectively achieved by combining the ignition timing control for each individual cylinder in addition to the air-fuel ratio control.

Further, a mixer is arranged in a distribution pipe to each cylinder of the intake manifold, and fuel gas is led to each mixer through a separate flow control valve, so that an upstream portion of the internal distribution pipe of the intake manifold is provided. If a throttle valve for controlling the intake air amount is arranged in the cylinder, the misfire recovery of the misfiring cylinder as a result of the misfiring determination for each cylinder is slightly reduced in the direction of increasing the opening of the fuel control valve corresponding to the misfiring cylinder. This can be achieved by adjusting. In this case, ignition timing control for each individual cylinder may be combined.

[0077]

As described above, according to the present invention, an exhaust pressure waveform is detected for each cylinder of a multi-cylinder engine, and the exhaust pressure waveform is analyzed for each cylinder to calculate a waveform area, and a reference area is calculated based on the waveform area. Since the misfire is determined for each cylinder by comparing with the value, the misfire is reliably determined for each cylinder for all cylinders,
Based on this, high-precision lean burn control can be performed for each cylinder, and accurate misfire determination can be performed for each cylinder by comparing the average value of the exhaust pressure waveform area of a plurality of cycles immediately before the preceding cylinder for each cylinder. Further, in a map in which the coordinate position is determined based on the engine speed and the throttle opening, an optimum reference value is set for each operating region corresponding to the coordinate position of the map, thereby performing a misfire determination according to the operating region. Thus, optimal fuel control can be performed for each operation region.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a gas engine driven heat pump air conditioning system to which the present invention is applied.

FIG. 2 is a configuration diagram of a control system of the air conditioning system of FIG.

FIG. 3 is a flowchart of a main program of a fuel control method according to the present invention.

FIG. 4 is a flowchart of a learning program in the flowchart of FIG. 3;

FIG. 5 is a flowchart of a rewriting program in the flowchart of FIG. 4;

FIG. 6 is a flowchart of a misfire determination program according to the present invention.

FIG. 7 is a graph of an operating region of the engine.

FIG. 8 is a graph of waveform data for cylinder determination and misfire determination.

FIG. 9 is a three-dimensional view showing a map of misfire determination criteria.

[Explanation of symbols]

1: gas engine, 2: refrigerant cycle, 3: air cleaner, 4: intake passage, 5: mixer, 6: throttle valve,
7: fuel supply pipe, 8: fuel control valve, 9: zero governor, 1
0: open / close valve, 11: oil separator, 12: exhaust pipe,
13: catalyst, 14: exhaust heat exchanger, 15: silencer,
16: drain separator, 17: exhaust outlet, 18: intake port, 19: neutralizer, 20: drain outlet, 21: oil pan, 22: oil tank, 23: oil supply pump, 2
4: clutch, 25: compressor, 26: flexible tube, 2
7: refrigerant inlet pipe, 28: refrigerant outlet pipe, 29: oil separator, 30: four-way valve, 31: indoor heat exchanger, 32: outdoor heat exchanger, 33: return pipe, 34: plate heat exchanger,
35: accumulator, 36: radiator, 37: fan, 38: recovery tank, 39: cooling water system, 40:
Cooling water pump, 41: second pump, 42: thermostat, 43: linear three-way valve, 44: branch pipe, 45: bypass pipe, 46: sub-accumulator, 47: throttle, 48,
49, 50: capillary tube, 51: HIC, 5
2: expansion valve, 60: outdoor unit, 61: indoor unit, 73: exhaust pressure sensor, 75: compressor temperature sensor, 76: cooling water temperature sensor, 77: high pressure side refrigerant pressure sensor, 78: low pressure side refrigerant pressure sensor.

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Shigeto Suzuki 2500 Shinkai, Iwata-shi, Shizuoka Yamaha Motor Co., Ltd. (Ref.)

Claims (4)

[Claims] 1. An exhaust pressure waveform of an engine comprising a plurality of cylinders is determined and detected for each cylinder, an area of the exhaust pressure waveform in a predetermined crank angle range of each cylinder is calculated, and this area is used as a reference area value. And calculating a difference or ratio of the misfire by comparing the difference or ratio with a predetermined reference value to determine a misfire for each cylinder. 2. The multi-cylinder engine according to claim 1, wherein the determination of each cylinder is made based on a pulsar signal for detecting camshaft rotation and a crank angle signal for detecting crankshaft rotation. Misfire determination method. 3. The apparatus according to claim 1, wherein the reference area value is an average value of areas of a plurality of exhaust pressure waveforms immediately before an exhaust pressure waveform to be determined for each cylinder. A misfire determination method for a multi-cylinder engine. 4. The system according to claim 1, wherein the reference value is set in a map corresponding to the engine speed and the throttle opening, and a different reference value is set for each area of the map. The misfire determination method for a multi-cylinder engine described in the above.