JPH08312425A - Exhaust emission control method and device of internal combustion engine - Google Patents

Abstract

PURPOSE: To realize an ultralean combustion and to reduce NOx gas, by detecting a misfire depending on the exhaust gas pressure, and providing an exhaust gas catalyst at the downstream side of an exhaust gas pressure detecting position, in the system to make the fuel lean while detecting the misfire, and to make the fuel rich so as to restore the misfire, when a misfire is detected. CONSTITUTION: In a lean combustion control in a gas engine, a lean combustion is carried out in a normal condition where the engine load and speed are constant. That is, only a prescribed one unit of feeding gas fuel is made lean, and under such a condition, the existence of a misfire is discriminated by a deciding circuit, by using a signal after deforming the detected signal of an exhaust gas pressure sensor 65 provided at the upstream side of an exhaust gas catalyst 66. When there is no misfire, only one more unit is made lean, and the existence of the misfire is discriminated. Such an operation by making one unit lean at each time is repeated until a misfire is detected, and when a misfire is detected after reaching to the misfire limit, the step of discriminating the misfire is stopped, and only one unit of fuel is made rich, so as to restore the misfire.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and a device for purifying exhaust gas of an internal combustion engine, and more particularly to a method and a device for purifying exhaust gas by combining a lean burn system and a catalytic system.

[0002]

2. Description of the Related Art As a method of purifying exhaust gas of an internal combustion engine, C
Oxidation catalyst and CO, NOx for removing O and HC
A method using a catalyst such as a reduction catalyst or a three-way catalyst for removing the above is known. These are mainly used in the automobile engine field.

On the other hand, it is known that lean combustion is effective for purifying exhaust gas, especially for reducing NOx. As one of such lean burn methods, a gas engine is driven with an air-fuel ratio at a lean limit, and a vibration fluctuation rate is obtained from acceleration data of the engine to maintain an allowable fluctuation rate immediately before combustion becomes unstable. Controlled lean burn method is disclosed in Japanese Patent Laid-Open No. 6-28
8265. In the conventional technique described in this publication, a vibration sensor is installed in a gas engine, a vibration fluctuation rate is calculated from its output, and the flow rate of the fuel gas is adjusted so as to maintain this vibration fluctuation rate at a preset allowable vibration fluctuation rate. The adjusting means is feedback-controlled.

On the other hand, in the heat pump type air conditioner,
An air conditioning system equipped with a heat exchanger for waste heat recovery is used to effectively use the waste heat of a gas engine. Exhaust gas countermeasures and fuel consumption issues are also important for engines in such air conditioners.

[0005]

However, in the prior art described in the above publication, the fuel flow rate is controlled so that the variation rate calculated based on the output of the vibration sensor falls within the allowable range to perform lean combustion. Therefore, when trying to lean to the lean limit, the effect of the engine weight is large due to the characteristics of the vibration sensor. Therefore, even if the fire is actually misfired, the misfire cannot be detected unless the lean limit is significantly exceeded. Therefore, the response of misfire detection in the vicinity of the lean limit is poor, and the engine is driven in the misfire state, so that unburned gas flows out to the exhaust system. This causes deterioration of fuel efficiency.

Further, as a countermeasure against engine exhaust gas in a conventional heat pump type air conditioner or the like, only a system in which a catalyst is provided in the middle of the exhaust pipe is sufficiently effective in consideration of heat recovery of exhaust gas and lean combustion. A technology that aims to drive the engine and purify exhaust gas has not been realized.

The present invention has been made in view of the above-mentioned drawbacks of the prior art, and controls the air-fuel ratio so as to surely detect the misfire at the lean limit and recover the misfire, thereby performing the ultra-lean combustion at the misfire limit. In addition to reducing NOx by reducing the amount of unburned gas flowing into the exhaust system during lean combustion, it also improves fuel efficiency. Effective use of a catalyst for purifying exhaust gas also provides effective exhaust gas countermeasures. It is an object of the present invention to provide an exhaust gas purification method and device for an internal combustion engine that can realize the above.

[0008]

In order to achieve the above object, the present invention provides a lean combustion method for gradually leaning fuel while detecting misfire and enriching the fuel when misfire is detected to recover the misfire. In the exhaust gas purifying method for an internal combustion engine using an exhaust gas purifying catalyst in the exhaust system, the misfire detection is performed based on the exhaust gas pressure in the exhaust passage, and the exhaust gas pressure detection position is provided on the downstream side. Provided is an exhaust gas purification method for an internal combustion engine, which is provided with a catalyst.

Further, according to the present invention, exhaust gas pressure detecting means provided in the exhaust passage, misfire judging means for judging misfire from pressure data detected by the exhaust gas pressure detecting means, and waste heat recovery means provided in the exhaust passage. An exhaust gas purifying apparatus for an internal combustion engine, comprising: a heat exchanger; and an exhaust gas purifying catalyst provided in an exhaust passage downstream of the exhaust gas pressure detecting means.

A preferred embodiment is characterized in that the heat exchanger for waste heat recovery is arranged downstream of the catalyst.

In another preferred embodiment, the waste heat recovery heat exchanger is arranged upstream of the catalyst.

[0012]

The exhaust gas can be purified by providing a catalyst on the exhaust passage.

In this case, if a waste heat recovery heat exchanger is arranged on the downstream side of the catalyst, the heat of oxidation of the unburned gas is recovered and the effective use of energy is achieved.

Further, by disposing the waste heat recovery heat exchanger upstream of the catalyst, it becomes possible to prevent the catalyst from overheating, and the exhaust gas temperature can be lowered to stably maintain the catalyst function.

If there is a misfire, the gas whose pressure remains low in the exhaust stroke is discharged from the combustion chamber to the exhaust system, and the exhaust gas pressure in the exhaust system upstream of the catalyst is not affected by the pressure change due to oxidation or reduction of the catalyst. , Immediately drops. In the present invention, the exhaust gas pressure in the exhaust system, which decreases immediately after the misfire is detected, and the misfire is detected based on this, so that reliable misfire detection is possible and the responsiveness is enhanced. This enables super lean combustion control at the misfire limit, greatly reducing NOx and improving fuel efficiency. Further, since the exhaust gas pressure is configured to detect the pressure on the exhaust passage, not on the combustion chamber, the pressure sensor may have a small pressure resistance, and accurate misfire detection can be performed using a sensor having a small and simple structure.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A gas engine in an engine driven heat pump (air conditioner) as an example to which the present invention is applied will be described below with reference to the drawings.

FIG. 1 is a configuration diagram of an engine according to an embodiment of the present invention, FIG. 2 is a block diagram showing a configuration of a drive control mechanism thereof, and FIG. 3 is a configuration diagram of essential parts of the embodiment of the present invention, FIG. FIG. 2 is a configuration diagram of a heat pump type air conditioner to which the engine of FIG. 1 is applied. Further, FIG. 5 is a Mollier diagram (P-i diagram) showing a state change of the refrigerant in the heat pump of FIG.

In the water-cooled gas engine 1 shown in FIG. 1, 6 is a piston, 7 is a piston 6 and the crankshaft 3
Connecting rods, 8 is a cooling water jacket formed around the cylinder 1a, and 9 and 10 are attached to the lower outer periphery of the crankcase 1b which is the outer periphery of the driven ring gear driven by the cell motor attached to the end of the crankshaft. And an engine speed sensor and a crank angle sensor.

The cylinder head 1c of the gas engine 1
An intake pipe 11 and an exhaust pipe 12 are connected to the intake passage 1d and the exhaust passage 1e, respectively. The intake passage 1d and the exhaust passage 1e are provided with an intake valve 15 and an exhaust valve driven by rocker arms 13 and 14, respectively. 16 opens and closes at an appropriate timing.

An air cleaner 17 and a mixer 18 for mixing air and fuel gas are connected to the intake pipe 11, and a throttle valve 19 is provided in the intake pipe 11 downstream of the mixer 18. A fuel supply pipe 20 connected to a fuel cylinder or a piped gas pipe (not shown) is connected to the mixer 18, and two fuel on-off valves 21 are provided in the middle of the fuel supply pipe 20. A zero governor 22 for adjusting the gas pressure to a low pressure and a fuel gas flow control valve 23 are connected.

The cylinder head 1c of the gas engine 1
An ignition plug 24 is attached to the ignition plug 2
An ignition coil 25 and an ignition control circuit 26 are connected to 4.

On the other hand, an exhaust gas heat exchanger 27 is provided in the middle of the exhaust pipe 12. An exhaust gas pressure sensor 65 is provided in the exhaust gas heat exchanger 27. Two
Reference numerals (2A, 2B) denote two compressors that are rotationally driven by the gas engine 1. A crankshaft 3 of the gas engine 1 is connected to a speed increasing device 4. One compressor 2A is connected to the output shaft of the speed increasing device 4 via an electromagnetic clutch 5A. Further, the gear G1 connected to the output shaft of the speed increasing device 4 is connected to the gear G1 via a small diameter gear G2.
Another gear G3 having the same diameter as the above meshes with each other, and the gear G3 is connected to the other compressor 2B via the electromagnetic clutch 5B.

As shown in FIG. 2, the actuator 2
8, 30 to 32, the engine speed sensor 9, the crank angle sensor 10, the electromagnetic clutches 5A and 5B, and the ignition control circuit 26 are connected to the control device 33. An exhaust gas pressure sensor 65 provided on the exhaust passage is connected to the control device 33. The opening of the throttle valve 19 is controlled by a throttle valve opening control actuator 30 based on a control signal from the control device 33. or,
The fuel opening / closing valve 21 and the fuel gas flow rate control valve 23 are similarly controlled by the opening control actuators 31, 32.

The engine of the present invention is, for example, a four-cylinder engine as shown in FIG. 3, and an air-fuel mixture is supplied to each cylinder from the intake manifold 63 via the intake passage 1d. The intake manifold 63 is sucked through the air cleaner 17 and the throttle valve 19, and fuel gas is supplied to the throttle valve portion from the fuel gas cylinder 62 through the control valve 21 and the pressure regulator 61. The exhaust passage 1e of each cylinder is connected to the exhaust manifold 64. An exhaust gas heat exchanger 27 is provided in the exhaust manifold 64. A catalyst 66 for purifying exhaust gas is provided on the exhaust pipe 12 connected to the exhaust manifold 64. It should be noted that the exhaust gas heat exchanger 27 is provided on the exhaust pipe 12 on the downstream side of the exhaust manifold 64.
It may be provided on the top. An exhaust gas pressure sensor 65 is provided in the exhaust manifold 64. The exhaust gas pressure sensor 65 is connected to the control device 33, as shown in FIG.

Further, the heat exchanger 27 may be provided on the exhaust pipe 12, and the catalyst 66 may be provided on the exhaust pipe 12 on the upstream side thereof. As a result, the reaction heat of the catalyst can be recovered, and more effective waste heat utilization becomes possible.

On the contrary, if a catalyst is provided on the downstream side of the heat exchanger 27, the exhaust gas temperature is lowered and the catalyst is prevented from being overheated, so that a stable catalyst function can be maintained. Which of the above arrangements is to be made is determined in consideration of the scale of the air conditioner, the type of catalyst, the conditions of the installation site and the space.

In any case, it is desirable that the position of the catalyst 66 is located downstream of the pressure sensor 65. This is to avoid the volume change accompanying the chemical change due to the catalytic action of oxidation or reduction and the influence of the pressure change due to the change on the detected pressure as much as possible.

Further, the catalyst 66 may be incorporated inside the heat exchanger 27. As a result, a compact structure of the entire apparatus is achieved, space is saved, and the degree of freedom of arrangement is increased.

In this case, if an oxidation catalyst is provided, unburned gas at the time of misfire can be purified and CO and HC can be reduced. If a three-way catalyst is provided, CO and NOX can be reduced more effectively.

By the way, as shown in FIG. 4, the present heat pump device includes a refrigerant circuit 34 that includes the compressor 2 (2A, 2B) to form a closed loop and a cooling circuit that includes a water pump 35 to form a closed loop. A water circuit 36 is provided. In addition,
In the figure, the arrow of the refrigerant circuit 34 indicates the flow direction of the refrigerant during the heating operation with the four-way valve 38 in the heating position.

The refrigerant circuit 34 is a circuit for circulating a refrigerant such as CFC by the compressor 2, which is a refrigerant line 34a extending from each discharge side of the compressors 2A and 2B to the oil separator 37 and a four-way valve 38. From the indoor heat exchanger 39 to the three indoor heat exchangers 39, and the refrigerant line 34d from the indoor heat exchanger 39 to the two outdoor heat exchangers 42 through the expansion valve 40 and halfway through the accumulator 41.
A refrigerant line 34e from the outdoor heat exchanger 42 to the four-way valve 38, and the four-way valve 38 to the accumulator 4
Refrigerant line 34f leading to 1 and refrigerant line 34g leading from the accumulator 41 to the sub accumulator 43
And a refrigerant line 34i from the sub accumulator 43 to each suction side of the compressors 2A and 2B.

An oil return line 44 and a bypass line 34j are led out from the oil separator 37, the oil return line 44 is connected to the refrigerant line 34g, and the bypass line 34j is connected to the refrigerant line 34f.
A bypass valve 45 is connected to the bypass line 34j. Liquid level sensors 46 and 47 for detecting the liquid level of the liquid-phase refrigerant stored in the accumulator 41 and the sub accumulator 43 are also provided.
Are provided respectively, and the bottom of the accumulator 41 is connected to the refrigerant line 34g mainly by a bypass line 34k for returning oil, and a bypass valve 48 is provided in the bypass line 34k.

A high pressure side pressure sensor 49 for detecting the high pressure side pressure of the refrigerant is provided in the refrigerant line 34b of the refrigerant circuit 34 described above, and a low pressure side pressure sensor for detecting the low pressure side pressure of the refrigerant is provided in the refrigerant line 34i. 50 are provided. An indoor temperature sensor 51 is provided near the indoor heat exchanger 39, and an outdoor temperature sensor 52 is provided near the outdoor heat exchanger 42. The high pressure side pressure sensor 49, the low pressure side pressure sensor 50, the indoor temperature sensor 51 and the outdoor temperature sensor 52 are connected to the control device 33 as shown in FIG. As shown in FIG. 2, a refrigerant circulation amount sensor 53, a main switch 54, and a desired indoor temperature setting switch 55 are connected to the control device 33.

On the other hand, the cooling water circuit 36 is a circuit in which the cooling water for cooling the gas engine 1 is circulated by the water pump 35, which passes from the discharge side of the water pump 35 to the exhaust gas heat exchanger 27. The temperature-sensing switching by deriving from the cooling water line 36a reaching the cooling water inlet of the gas engine 1 (the inlet of the cooling water jacket 8 shown in FIG. 1) and the cooling water outlet of the gas engine 1 (the outlet of the cooling water jacket 8). Valve 56
Is connected to the suction side of the water pump 35 through the accumulator 41, which is led out from the linear three-way valve 57 and the cooling water line 36c extending from the temperature-sensing switching valve 56 to the linear three-way valve 57. Cooling water line 36
d, and cooling water lines 36e and 36f that are respectively drawn from the temperature-sensitive switching valve 56 and the linear three-way valve 57 and connected to the cooling water line 36d. A heat exchanger 58 is provided.

When the gas engine 1 is driven, the rotation of the crankshaft 3 is accelerated by the speed increasing device 4 and transmitted to one compressor 2A via the electromagnetic clutch 5A in the ON state, and at the same time, It is transmitted to the other compressor 2B via the gears G1, G2, G3 and the electromagnetic clutch 5B in the ON state, and both compressors 2A, 2B are simultaneously driven to rotate at the same speed.

When the compressors 2A and 2B are rotationally driven as described above, the gas-phase refrigerant in the state (pressure P1, enthalpy i1) shown in FIG. 5 flows from the refrigerant line 34i to the compressor 2.
A and 2B are sucked and compressed, and become high-temperature high-pressure refrigerant in the state (pressure P2, enthalpy i2) shown in FIG.
The required power (compression heat quantity) AL of the compressors 2A and 2B at this time is represented by (i2-i1). In addition, the compressor 2A,
The pressure P1 of the vapor-phase refrigerant sucked into 2B is detected by the low pressure side pressure sensor 50 and input to the control device 33.

The high temperature and high pressure vapor phase refrigerant is the refrigerant line 34.
It is guided to the oil separator 37 through a, and the oil component is removed by the oil separator 37. Then, the gas-phase refrigerant from which the oil component has been removed reaches the four-way valve 38 through the refrigerant line 34b. The oil separated from the refrigerant in the oil separator 37 is returned to the refrigerant line 34g through the oil return line 44. or,
Pressure P2 of the high-temperature high-pressure refrigerant flowing through the refrigerant line 34b
(Ignore pressure loss) is the high pressure side pressure sensor 49
Is detected and input to the control device 33.

During the heating operation, the ports 38a and 38c and the ports 38b and 38d of the four-way valve 38 are in communication with each other, and the high-temperature and high-pressure gas-phase refrigerant passes through the four-way valve 38 and is on the refrigerant line 34c side. To the indoor heat exchanger 39 that functions as a condenser. Then, the high-temperature and high-pressure gas-phase refrigerant guided to the indoor heat exchanger 39 releases the condensation heat Q2 to the indoor air to be liquefied and becomes the liquid-phase refrigerant in the state (pressure P2, enthalpy i3) shown in FIG. The heating of the room is performed by the heat radiation amount Q2 (= i2-i3) at this time.

Next, the high-pressure liquid-phase refrigerant liquefied in the indoor heat exchanger 39 is decompressed by the expansion valve 40 and becomes a state (pressure P1, enthalpy i3) shown in FIG. The refrigerant line 34d flows toward the indoor unit 42.

On the other hand, the cooling water circulated in the cooling circuit 36 by the driving of the water pump 35 is discharged from the water pump 35 and flows through the cooling water line 36a, and in the middle thereof, in the exhaust gas heat exchanger 27, the gas engine. 1 to exhaust pipe 12
After the heat of the exhaust gas discharged to the engine is recovered and heated, the gas engine 1 is cooled through the cooling water jacket 8 of the gas engine 1. The cooling water heated by the exhaust gas heat exchanger 27 and the gas engine 1 is supplied to the cooling water line 3
6b to reach the temperature sensitive switching valve 56.

After starting the gas engine 1, the cooling water temperature is low,
The temperature sensitive switching valve 56 circulates the cooling water to the cooling water line 36e, and stops the flow to the cooling water line 36c. (I
1 = 0) When the gas engine 1 is in a steady operation state, the amount of heat exchange between the exhaust gas heat exchanger 27 and the gas engine 1 increases, the cooling water temperature rises, and the temperature sensitive switching valve 56 moves the cooling water line 36e to the cooling water line 36e. While stopping the flow (I2 = 0), the flow to the cooling water line 36c is allowed. The linear three-way valve 57 divides the cooling water amount I1 into the flow rate I3 to the cooling water line 36d and the flow rate I4 to the cooling water line 36f by the control device 33.

In the accumulator 41, the cooling water flowing in the cooling water line 36d heats the refrigerant flowing in the refrigerant line 34d and the liquid-phase refrigerant stored in the accumulator 41, and the waste heat of the gas engine 1 (exhaust gas is exhausted). The heat given and the heat taken from the gas engine 1 by the cooling are given to the refrigerant. For example, the lower the outdoor temperature, the smaller the amount of heat absorbed in the outdoor heat exchanger 42. Therefore, the flow rate I4 is increased (flow rate I3 is decreased), the amount of waste heat to the refrigerant is increased, and the required Q1 amount is secured.

The refrigerant flowing through the refrigerant line 34d, after cooling the liquid phase refrigerant in the accumulator 41 as described above, reaches the outdoor heat exchanger 42 functioning as an evaporator, and when the outside air temperature is a predetermined value or more, the outdoor The fan 42a of the heat exchanger 42 is driven, and the refrigerant takes heat from the outside air and evaporates in the outdoor heat exchanger 42 as described above.

Then, the refrigerant flows from the outdoor heat exchanger 42 through the refrigerant line 34e to the four-way valve 38 and through the four-way valve 38 to the refrigerant line 34f side, and the accumulator 41.
Introduced within.

In the accumulator 41, the gas and liquid of the refrigerant are separated, and a part of the heat generation of the gas engine 1 is given to the liquid phase refrigerant by the cooling water flowing through the cooling water line 36d. The part evaporates and vaporizes.

The gas-phase refrigerant in the accumulator 41 is sent to the sub accumulator 43 through the refrigerant line 34g and further sucked into the compressors 2A and 2B through the refrigerant line 34i, but is sucked into the compressors 2A and 2B. The state of the vapor phase refrigerant is as shown in FIG. 5 (pressure P1, enthalpy i
Returning to 1), this gas-phase refrigerant is used in compressors 2A and 2B.
Is compressed again and the same operation as described above is repeated.

Therefore, until the refrigerant is depressurized by the expansion valve 40 and the refrigerant is sucked into the compressors 2A, 2B, the heat of the gas engine 1 is given to the refrigerant by the accumulator 41 and the heat from the outside air is given by the outdoor unit 42. Finally, the refrigerant receives the heat quantity Q1 (= i1−i3), evaporates, and is further heated.

The above is a description of the configuration and function of a heat pump type air conditioner as an example to which the present invention is applied.

According to the present invention, in the gas engine having the above-described structure, the control is performed so that the lean air-fuel ratio reaches the misfire limit. In this case, the engine control is as shown in FIG.
When the torque is larger than the torque position (dotted line) where the throttle is fully opened (WOT) and misfire occurs, control is performed so as to obtain the required torque only by fuel control, and for torques smaller than the dotted line where misfire occurs, the misfire limit air-fuel ratio Is controlled by the throttle opening.

FIG. 6 is a block diagram of lean burn control performed in the gas engine having the above configuration. Engine speed information and load information are input to an ECU (control device), and further, detection information from various sensors is input as shown in FIG. The control device first determines the operating state (step S1). Here, it is determined whether the transient state or the steady state is based on the change in the opening of the throttle valve. In the transient state, lean combustion is not performed, and the fuel control valve is drive-controlled so as to supply a slightly rich air-fuel mixture corresponding to the acceleration pump (step S2). When the engine load and engine speed are constant, the lean burn control is performed as follows. First, the supply gas fuel is made lean by a predetermined unit (step S3). Here, the presence or absence of misfire is determined (step S4). The presence or absence of this misfire is determined by a determination circuit as described later by shaping the detection signal from the exhaust gas pressure sensor 65. If there is no misfire, make one unit leaner and determine again whether there is a misfire. Such leaning for each unit is repeated until a misfire is detected. When the misfire limit is reached and misfire is detected, the misfire determination step is stopped and the fuel is enriched by one unit to recover the misfire (step S5). The leaning or enrichment of the predetermined one unit is performed by controlling the pulse number of the step motor that drives the fuel control valve. When a misfire occurs, the fuel is enriched and the target air-fuel ratio data for lean burn control, which is stored in the ROM as map data in advance, is rewritten.

FIG. 7 is a block diagram of misfire determination. A signal a of one pulse per revolution and a signal b of n pulses per revolution are obtained from the crank angle sensor, and the position of the crank angle α at which the exhaust pressure change due to misfire is large is calculated based on these signals. And a signal c that emits a pulse at a position that is 180 degrees out of phase with this (two positions in one rotation)
To form. A gate time for detecting the exhaust pressure is calculated at a position corresponding to this α, and a signal d having a predetermined interval is calculated.
To form. Here, the value of the detection signal f from the exhaust gas pressure sensor is detected by the gate time of the signal d to obtain the pressure data signal e. This pressure data is used as data for calculating the average value from the start of control. The control device is
The present value of the exhaust gas pressure at each α and α + 180 ° crank angle is compared with the above average value, and if the difference is larger than a predetermined set value g, it is determined that a misfire has occurred.

FIG. 8 shows the above signals extracted on the same time series. The signal a is, for example, a pulse signal at the position of the top dead center, and the signal c is out of phase with the top dead center pulse by the crank angle corresponding to α. The exhaust gas pressure data e at the gate time signal d at this position is compared with the average value. If the current value deviates significantly from the average value, it is determined that a misfire has occurred.

As can be seen from the embodiments described above, the present invention is summarized as follows.

(1) Exhaust system (for example, in the exhaust manifold)
The misfire is discriminated by detecting the exhaust gas pressure and analyzing this.

(2) As an example of the analysis method, the exhaust pressure at a predetermined crank angle of a specific cylinder is compared with the average value of the exhaust pressure at that angle, and if the difference is larger than a set value, it is determined that a misfire has occurred.

(3) Leaning is performed in predetermined units until misfire is detected, and when misfire occurs, the air is returned to rich, and the feedback target air-fuel ratio data is rewritten so that unburned gas is discharged due to misfire. While suppressing, ultra lean combustion at the misfire limit is achieved and NOX is reduced.

(4) The features of the exhaust gas pressure detection of the present invention are as follows.

The basic exhaust pressure waveform during normal operation is
In the case of four cylinders, one peak (positive pressure wave) is drawn after the exhaust valve is opened after combustion, and then a pattern in which a negative pressure wave is generated is repeated every 180 degrees crank angle.

Although the waveform may be disturbed by the interference wave under the influence of the load, the rotation speed, and the exhaust pipe after the manifold, the waveform change due to the misfire can be observed remarkably by an oscilloscope, for example.

The height of the positive pressure wave increases in proportion to the throttle opening and the rotation speed. The maximum-minimum pressure difference is large in high-speed and high-load operation, and is smallest when idling.

On the oscilloscope screen, the fluctuations of the positive pressure wave and the negative pressure wave at the time of misfire are more than those at the time of normal combustion.
The positive pressure wave that should be in the original crank angle position is missing,
(B) The negative pressure wave that should be in the original crank angle position is missing, (c) The magnitude of the positive pressure wave and / or the negative pressure wave that should be in the original crank angle position is large or small, (d) The original crank The negative pressure wave that should be in the angular position becomes very large, so the next positive pressure wave also becomes high.
Occurs as one of two patterns. (5) The misfire determination is performed by comparing the exhaust pressure at a predetermined crank angle with the average value of the exhaust pressure up to that crank angle in a steady operation state in which there is no change in the opening of the throttle valve. Therefore, it is not necessary to have high accuracy in the absolute value of the pressure, and the pressure fluctuation can be accurately detected even if the zero drift that is the reference of the absolute value occurs. (6) During steady operation, misfire determination is performed while moving the fuel valve toward the lean side by a predetermined unit. In this case, as a control program for the entire gas heat pump device, it is conceivable that the throttle valve will gradually open to compensate for the torque decrease due to leaning, but the misfire determination control continues.

(7) When the air-fuel ratio at the misfire limit is obtained by the learning control, the fuel valve data stored in the ROM until then is rewritten to the data corresponding to the air-fuel ratio. This learning control is continued during the feedback control.

(8) In a multi-cylinder gas engine, by installing one pressure sensor in the exhaust manifold after the exhaust manifolds from the multiple cylinders have joined, or in the exhaust gas heat exchanger that also serves as the merging portion, Misfire judgment is possible.

(9) By disposing a catalyst on the downstream side of the exhaust gas pressure sensor so as not to be affected by the pressure change due to the catalytic action, it is possible to enhance the exhaust gas purifying action without lowering the accuracy of misfire detection.

(10) A waste heat recovery heat exchanger can be provided on the downstream side of the catalyst to recover the heat of oxidation of the unburned gas.

(11) A waste heat recovery heat exchanger can be provided on the upstream side of the catalyst to prevent the catalyst from overheating.

(12) A catalyst can be provided inside the heat exchanger to reduce the size of the structure and save space.

Further, in the engine driven heat pump (air conditioner or refrigeration system), exhaust pressure is detected to detect misfire due to excessive leaning, and if misfire is detected, the air-fuel ratio is made rich to prevent misfire. Therefore, even if a misfire occurs, the misfire is immediately prevented, the exhaust gas temperature is kept high, and the amount of heat applied to the cooling water in the exhaust gas heat exchanger 27 is secured. As a result, when the heat absorption amount (Q1) due to the low outside air temperature during heating is insufficient and it is essential to apply energy to the refrigerant other than the compressor 2, heat is stably applied from the cooling water to the refrigerant, A stable heating capacity is secured while improving the exhaust emission and heat consumption of the heat pump drive engine. When an oxidation catalyst is arranged as a catalyst, the amount of unburned gas due to misfire can be suppressed by misfire prevention control, so that unburned gas can be oxidatively burned and not discharged.

Further, when the four-way valve 38 is switched to the cooling mode and the ports 38a and 38b and the ports 38c and 38d are communicated with each other, or in the refrigerator, further cooling or freezing may be required even when the outside air temperature is low. .
In this case, the heat radiation amount (Q2) in the outdoor heat exchanger 42 (equivalent to the evaporator) becomes excessive, and the liquefied refrigerant becomes the outdoor heat exchanger 4
2 and 34d, which is the upstream side of the expansion valve 40, stays, and the refrigerant circulation amount is lost. However, since heat is applied to the refrigerant in the accumulator 41 to increase the amount of heat absorption (Q1), even if the amount of heat radiation (Q2) becomes excessive, all the refrigerant will not stay and the necessary refrigerant circulation amount will be secured. To be done. That is, even if a misfire due to excessive leaning occurs, the air-fuel ratio is immediately enriched to prevent the misfire, so that stable cooling capacity is ensured while improving the exhaust emission of the refrigeration system or the air conditioner drive engine and improving the fuel consumption. . Although heat is exchanged on the low-pressure side of the low-voltage circuit 34 in the above-described embodiment, the receiver tank is arranged on the high-pressure side, and the cooling water that has absorbed the engine waste heat is absorbed in the liquid refrigerant stored in the receiver tank. Even if it is circulated, the same effect as above can be obtained. Further, the linear three-way valve 57 may be controlled when a misfire due to excessive leaning is detected, and the cooling water amount I3 may be increased for a predetermined time from the amount before the misfire. As a result, the cooling capacity, the refrigerating capacity, or the heating capacity can be stably secured until the misfire is recovered by the enrichment. Further, if there is a misfire due to excessive leaning, the engine speed decreases, and the high pressure refrigerant gas pressure discharged from the compressor 2 decreases. However, since the pressure drop signal output from the high pressure side pressure sensor 49 is delayed, immediately after the misfire is detected, the opening degree of the expansion valve 40 is slightly reduced and kept for a predetermined time. As a result, the refrigerant pressure on the high-pressure side can be secured at a predetermined pressure until the misfire is recovered by the enrichment, so that a stable condensing action can be secured,
It is possible to stably secure the cooling capacity, the freezing capacity, or the heating capacity.

Further, in the multi-cylinder engine 1, since the exhaust gas pressure sensor 65 is arranged in the exhaust gas heat exchanger 27 which also serves as the merging portion of the exhaust passage 1e for each cylinder, even if a misfire occurs in any of the cylinders, it is immediately possible. It becomes possible to control enrichment. Further, since the exhaust gas expands in the exhaust gas heat exchanger 27, the heat load and the pressure load of the exhaust gas pressure sensor 65 are reduced, and the durability can be increased.

Note that air-fuel ratio control is performed for each cylinder, that is, for each cylinder, an independent intake passage 1e and throttle valve 1 are provided.
In the multi-cylinder engine 1 in which the d, the mixer 18 and the fuel gas flow rate control valve 23 are arranged, the exhaust gas pressure sensor 65 ′ may be arranged in each exhaust passage 1e. By performing the misfire control in the lean air-fuel ratio range in which the fuel gas flow rate or the throttle opening is controlled for each cylinder based on the pressure of each exhaust passage 1e, more reliable misfire prevention can be achieved as compared with the misfire control based on the vibration. It will be possible.

[0072]

As described above, in the present invention, since the misfire is detected by detecting the exhaust gas pressure in the exhaust passage, the misfire is surely detected, the responsiveness in the lean burn control is improved, and the misfire is detected. Ultra lean combustion is possible at the limit, and NOX can be reduced. In addition, outflow of unburned gas is suppressed by reliable detection of misfire, and fuel consumption is improved.

Furthermore, by combining with a catalyst, it becomes possible to effectively recover waste heat and to effectively purify exhaust gas, and to stably maintain the catalytic function.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a gas engine according to an embodiment of the present invention.

FIG. 2 is a block diagram of a drive control mechanism of the engine of FIG.

FIG. 3 is a main part configuration diagram of a gas engine according to an embodiment of the present invention.

FIG. 4 is a configuration diagram of a heat pump type air conditioner to which the engine of FIG. 1 is applied.

FIG. 5 is a Mollier diagram showing the pressure with respect to the enthalpy of the refrigerant.

FIG. 6 is a block diagram of lean burn control according to the present invention.

7 is an explanatory diagram showing a flow of misfire detection in the lean burn control of FIG.

FIG. 8 is a related explanatory diagram of each signal in the flow of FIG. 7.

FIG. 9 is a conceptual diagram of engine control.

[Explanation of symbols]

1: Gas engine, 12: Exhaust pipe, 19: Throttle valve, 27: Exhaust gas heat exchanger, 63: Intake manifold,
64: exhaust manifold, 65: exhaust gas pressure sensor,
66: Catalyst.

Claims (4)

[Claims] 1. A lean combustion method in which a fuel is gradually made lean while detecting a misfire, and when the misfire is detected, the fuel is enriched to recover the misfire, and a catalyst for purifying exhaust gas is further provided in an exhaust system. In an exhaust gas purification method for an internal combustion engine, the misfire detection is performed based on the exhaust gas pressure in an exhaust passage, and the catalyst is provided on the downstream side of the exhaust gas pressure detection position. Method. 2. Exhaust gas pressure detection means provided in the exhaust passage, misfire determination means for determining misfire from pressure data detected by the exhaust gas pressure detection means, and waste heat recovery heat exchanger provided in the exhaust passage. And an exhaust gas purification catalyst provided in an exhaust passage downstream of the exhaust gas pressure detection means. 3. The exhaust gas purifying apparatus for an internal combustion engine according to claim 2, wherein the waste heat recovery heat exchanger is arranged downstream of the catalyst. 4. The exhaust gas purifying apparatus for an internal combustion engine according to claim 2, wherein the waste heat recovery heat exchanger is arranged upstream of the catalyst.