JP5907748B2 - Multi-cylinder mixed combustion engine - Google Patents

Description

The present invention includes an engine body having a plurality of cylinders;
Fuel supply means for supplying a mixed fuel obtained by mixing a high calorific value fuel and a low calorific value fuel having a calorific value lower than that of the high calorific value fuel to the engine body;
Misfire detection means for detecting the occurrence of misfire in each cylinder in the engine body;
The present invention relates to a multi-cylinder mixed combustion engine having control means for controlling operation.

As a reciprocating engine that compresses and burns an air-fuel mixture of fuel and combustion air in each cylinder of the engine body, a mixed combustion engine using a mixed fuel obtained by mixing two or more kinds of fuels is known (for example, , See Patent Document 1). In such a mixed combustion engine, a calorific value per unit volume (in the present application, simply referred to as “biogas including biomethane containing methane generated by decomposition of organic waste by bacteria such as landfill gas, digester gas, swage gas, etc.”). A low-calorific value fuel having a relatively low calorific value) is used as a fuel, such as natural gas, mixed with a high calorific value fuel having a higher calorific value than the low-calorific value fuel. There is a case.
In this type of mixed combustion engine, the calorific value of biogas tends to fluctuate, so the calorific value of the mixed fuel also fluctuates with the fluctuation, resulting in unstable combustion conditions and misfires. Is concerned.
Therefore, in the mixed combustion engine disclosed in Patent Document 1, the variation in the calorific value of the low calorific value fuel is monitored based on the variation in the engine speed, and the mixing ratio of the low calorific value fuel and the high calorific value fuel is controlled based on this. By doing so, the calorific value of the mixed fuel is always kept constant, and the misfire caused by the fluctuation of the calorific value is prevented in advance.

In a multi-cylinder engine in which a plurality of cylinders are arranged in an engine body, when misfire occurs in some cylinders, the engine output is temporarily reduced because no output is obtained in those cylinders. In such a case, normally, the opening degree of the throttle valve is increased by the output control of the control device, and the intake amount of the air-fuel mixture to the engine body is increased, thereby preventing the engine output from being lowered.
Further, as a technique for eliminating misfire, there is known a technique for performing misfire elimination processing such as delay of ignition timing or increase in fuel supply amount for a cylinder in which misfire is detected (for example, a patent) See reference 2.)

JP 2004-060604 A JP 2002-039007 A

In the conventional multi-cylinder engine, as described above, when the misfire occurs, the throttle valve opening is increased to prevent the engine output from decreasing, but the throttle valve opening is increased. There is a limit to it. For example, when a misfire occurs during rated operation in which the throttle valve is operated at a fully open position, the opening of the throttle valve cannot be increased, resulting in a decrease in engine output.
Furthermore, such a multi-cylinder engine is a mixture of two or more fuels having different calorific values, that is, a high calorific value fuel and a low calorific value fuel having a calorific value lower than that of the high calorific value fuel. In some cases, the engine is configured as a mixed combustion engine using the mixed fuel. In such a multi-cylinder mixed combustion engine, as in Patent Document 1, the mixing ratio of two or more kinds of fuels is controlled so that the calorific value of the mixed fuel is always kept constant to prevent the occurrence of misfire. Even if configured as described above, if misfire occurs in some cylinders due to factors other than the calorific value of the mixed fuel, the engine output is reduced in the same manner as described above. In addition, when misfire occurs, the misfire may not be resolved even if the ignition timing is delayed or the fuel injection amount is increased as in Patent Document 2 above. Will be invited.

  The present invention has been made paying attention to such a point, and an object of the present invention is to use a mixed fuel obtained by arranging a plurality of cylinders in an engine body and mixing two or more kinds of fuels having different calorific values. In a cylinder type mixed combustion engine, it is in the point which provides the technique which can avoid the fall of the engine output accompanying a misfire.

In order to achieve this object, a multi-cylinder mixed combustion engine according to the present invention includes:
An engine body having a plurality of cylinders;
Fuel supply means for supplying a mixed fuel obtained by mixing a high calorific value fuel and a low calorific value fuel having a calorific value lower than that of the high calorific value fuel to the engine body;
Misfire detection means for detecting the occurrence of misfire in each cylinder in the engine body;
A multi-cylinder mixed combustion engine having a control means for controlling operation,
The first characteristic configuration is
A mixing ratio adjusting means capable of adjusting a low heating value fuel mixing ratio, which is a mixing ratio of the low heating value fuel to the high heating value fuel in the mixed fuel;
When the control means detects the occurrence of misfire in some cylinders by the misfire detection means, the control means controls the mixing ratio adjustment means, and the low calorific value of the mixed fuel supplied to the engine body It lies in performing the mixing ratio changing process Ru increase the calorific value of the mixed fuel misfire by reducing the fuel mixing ratio is supplied to the cylinder does not occur.

According to the first characteristic configuration, by providing the mixing ratio adjusting means, the low heating value fuel mixing ratio is adjusted in the mixed fuel supplied to the engine body, and the heating value of the mixed fuel is changed. Can do. Further, by executing the mixing ratio changing process by the control means, when misfire occurs in some cylinders, the low heating value fuel mixing ratio is reduced, and the mixed fuel supplied to the engine body generates heat. The amount will increase. Therefore, since the calorific value of the mixed fuel supplied to at least the cylinder in which misfire does not occur increases, the output obtained from that cylinder increases in a form that compensates for the output in the cylinder in which misfire has occurred. As a result, a decrease in the overall engine output due to misfire can be favorably avoided.
Therefore, according to the present invention, in a multi-cylinder mixed combustion engine using a mixed fuel in which a plurality of cylinders are arranged in an engine body and two or more kinds of fuels having different calorific values are mixed, the engine output is reduced due to misfire. Techniques that can be avoided can be provided.

The second characteristic configuration of the multi-cylinder mixed combustion engine according to the present invention is in addition to the first characteristic configuration,
The control means executes the mixing ratio changing process when the misfire detection means continuously detects the occurrence of misfire in some cylinders.

According to the second characteristic configuration, it is possible to prevent an unnecessary increase in the mixed fuel and to avoid an overpower state in which the engine output exceeds the target engine output.
That is, when misfiring occurs in some cylinders and the above-described mixing ratio changing process is executed to avoid a decrease in engine output due to the misfiring, for example, when the misfiring is temporary Since an excess output can be obtained from the cylinder in which the misfire has been eliminated, the above-mentioned over-output state is obtained.
Therefore, when it is determined that the misfire occurring in some cylinders is temporary and not continuous, such an excessive ratio is prevented by not executing the above mixing ratio changing process. The output state can be avoided.
On the other hand, when it is determined that misfires occurring in some cylinders are continuous, it is possible to quickly execute the above-described mixing ratio changing process and avoid a subsequent decrease in engine output. .

The third feature configuration of the multi-cylinder mixed combustion engine according to the present invention is in addition to any of the first to second feature configurations,
The control means executes a misfire cylinder deactivation process for deactivating a specific cylinder in which the occurrence of misfire has been detected when the mixture ratio changing process is performed.

  According to the third characteristic configuration, when misfire occurs in some cylinders and no output is obtained from the cylinders, the engine output is reduced by executing the mixing ratio changing process. Accordingly, the operation of the cylinder in which the misfire has occurred is abandoned and the engine is brought into the rest state. Therefore, since the power for operating the cylinder in which the misfire has occurred can be reduced, even when the thermal efficiency is reduced due to the misfire, the reduction width can be made as small as possible.

The fourth feature configuration of the multi-cylinder mixed combustion engine according to the present invention is in addition to any of the first to third feature configurations,
The control means executes an output control for setting an engine output by controlling an opening degree of a throttle valve provided in an intake passage, and the engine output is controlled in the output control when the mixing ratio changing process is executed. The point is to keep it constant.

When the mixing ratio changing process is executed to reduce the low heating value fuel mixing ratio, the heating value of the mixed fuel may not be increased uniformly and may become unstable.
Therefore, according to the fourth feature configuration, when the mixing ratio changing process is executed, the opening degree of the throttle valve is controlled so that the engine output is maintained constant in the output control. Therefore, it is possible to prevent the engine output from becoming unstable due to the increase in the heat generation amount of the mixed fuel that is increased. In addition, in the output control after execution of the mixing ratio changing process, the opening of the throttle valve is increased in a form that compensates for the engine output that has been reduced due to the occurrence of misfire. The target engine output will be set.

The fifth feature configuration of the multi-cylinder mixed combustion engine according to the present invention includes, in addition to any of the first to fourth feature configurations,
The high calorific value fuel is natural gas, and the low calorific value fuel is biogas.
According to the fifth characteristic configuration, even when using a mixed fuel obtained by mixing a natural gas with a high calorific value with a biogas with a lower calorific value, the engine output is reduced due to misfire. While avoiding suitably, the operating state of the engine after the mixing ratio changing process can be stabilized.
That is, when misfire occurs in some of the cylinders, the mixing ratio changing process is executed, so that the mixing ratio of biogas to natural gas is reduced and the heating value of the mixed fuel is increased. Then, in the mixed fuel supplied to the engine body, the proportion of biogas whose calorific value tends to fluctuate decreases, so the calorific value of the mixed fuel is also maintained stable, Since the influence of the flow rate variation of the biogas can be reduced, the engine operating state is stabilized as a result.

The sixth feature configuration of the multi-cylinder mixed combustion engine according to the present invention is in addition to any of the first to fifth feature configurations,
When the control means executes the mixing ratio changing process, the low heating value fuel mixing ratio of the mixed fuel supplied to the engine body is reduced based on the number of cylinders in which the occurrence of misfire has been detected. It is in point to let you.
According to the sixth characteristic configuration, when the engine output is set to the target engine output in the output control after the heat generation amount increasing process is executed, the opening of the throttle valve is substantially the same as before the misfire occurs. Therefore, the opening adjustment width of the throttle valve can be maintained at a suitable value.

Schematic configuration diagram of an engine according to an embodiment Control flow chart of engine according to the embodiment The figure which shows the state change at the time of the misfire detection of the engine which concerns on embodiment

Embodiments of the present invention will be described with reference to the drawings.
As shown in FIG. 1, an engine 100 according to the present embodiment uses an engine body 1 having a plurality of cylinders 2 and a mixed fuel Gm obtained by mixing two or more kinds of fuels Gh and Gl having different calorific values. An engine control unit (hereinafter referred to as ECU) comprising a fuel supply means X for supplying to the main body 1, a misfire detection means Y for detecting the occurrence of misfire in each cylinder 2 in the engine main body 1, and a computer for controlling the operation. 30 (an example of a control means) and a multi-cylinder mixed combustion engine.

The engine body 1 is a so-called four-cylinder engine in which four cylinders 2 defined by the upper surface of the piston 6 and the inner surface of the cylinder 5 are connected in parallel with one crankshaft 9 by a connecting rod 7. It is structured into a mold.
In each cylinder 2, as in a normal reciprocating engine, a cycle consisting of various strokes of an intake stroke, a compression stroke, a combustion / expansion stroke, and an exhaust stroke is repeatedly performed, and the piston 6 reciprocates at that time. The connecting rod 7 outputs the rotational movement of the crankshaft 9.
That is, in the intake stroke, the air-fuel mixture M is drawn from the intake passage 10 through the intake port 10 a and the intake valve 3. In the subsequent compression stroke, the sucked air-fuel mixture M is compressed as the piston 6 rises. In the subsequent combustion / expansion stroke, the compressed air-fuel mixture M is spark-ignited by the spark plug 8 and burned. Push down the piston 6. Further, in the subsequent exhaust stroke, the exhaust gas E is discharged to the exhaust passage 20 through the exhaust valve 4 and the exhaust port 20a as the piston 6 moves up.
The intake valve 3 and the exhaust valve 4 are configured to open and close for each cycle by a cam mechanism (not shown). Further, the ECU 30 maintains the intake valve 3 and the exhaust valve 4 in a normally closed state with respect to a specific cylinder 2, thereby stopping the misfire cylinder in which the intake and combustion of the air-fuel mixture M in the cylinder 2 is stopped. The pause process is configured to be executable. In the cylinder 2 in such a paused state, the piston 6 reciprocates in a state where both the intake valve 3 and the exhaust valve 4 are closed and sealed, and the mixture 2 is sucked into the cylinder 2. Power and power when exhaust gas E is discharged from the cylinder 2 are hardly consumed.

A mixed fuel Gm obtained by mixing two or more kinds of fuels Gh and Gl having different calorific values is a mixture of a high calorific value fuel Gh and a low calorific value fuel Gl having a calorific value lower than that of the high calorific value fuel Gh. Natural gas city gas 13A is used as the high calorific value fuel Gh, while the low calorific value fuel Gl has a calorific value per unit volume as compared with the natural gas city gas 13A. Small biogas is used.
Each of the high calorific value fuel Gh and the low calorific value fuel Gl is supplied to the mixer 17 with the flow rate adjustment by the flow rate adjusting valves 15 and 16 and mixed to become the mixed fuel Gm. The flow rate adjusting valves 15 and 16 adjust the supply amount of at least one of the high calorific value fuel Gh and the low calorific value fuel Gl to the mixer 17 so that the high amount of the mixed fuel Gm generated by the mixer 17 is high. It functions as a mixing ratio adjusting means Z that can adjust the mixing ratio of the low heating value fuel Gl to the heating value fuel Gh (hereinafter referred to as “low heating value fuel mixing ratio”). That is, the mixing ratio adjusting means Z is an operation for increasing the supply amount of the high calorific value fuel Gh to the mixer 17 by increasing the opening degree of the flow rate adjusting valve 15 when the low calorific value fuel mixing ratio is decreased. In addition, one or both of the operations of decreasing the amount of the low calorific value fuel Gl to the mixer 17 by decreasing the opening degree of the flow rate adjusting valve 16 is performed. The ECU 30 can control the mixing ratio adjusting means Z to set the low heating value fuel mixing ratio to a desired ratio.

  The mixed fuel Gm generated by the mixer 17 is supplied to the mixer 11 provided in the intake passage 10 with the flow rate adjustment of the flow rate adjustment valve 18. In the mixer 11, the mixed fuel Gm is mixed with the combustion air A that flows through the intake passage 10, and an air-fuel mixture M of the combustion air A and the mixed fuel Gm is formed. The air-fuel mixture M formed by the mixer 11 is sucked into each cylinder 2 of the engine body 1 through the intake passage 10. On the other hand, the ECU 30 adjusts the opening degree of the flow rate adjusting valve 18 based on the detection result of an oxygen sensor (not shown) provided in the exhaust passage 20, and mixes the mixed fuel Gm with the combustion air A in the mixer 11. By adjusting the amount, the air-fuel ratio of the air-fuel mixture M sucked into each cylinder 2 is set to a desired air-fuel ratio. In the present embodiment, the air-fuel ratio of the air-fuel mixture M is set in a range in which spark ignition by the spark plug 8 is possible, specifically in the vicinity of the theoretical air-fuel ratio.

  The intake passage 10 is provided with a throttle valve 12 that can adjust the intake amount of the mixture M in each cylinder 2 of the engine body 1. The ECU 30 executes output control for setting the engine output by controlling the opening of the throttle valve 12. Specifically, the ECU 30 refers to the power generation output of the generator 25 that is driven by the rotational power of the crankshaft 9 to generate power, and detects the actual engine output output from the crankshaft 9. Further, the target engine output is determined corresponding to the required power output, etc., and when the actual engine output is smaller than the target engine output, the opening of the throttle valve 12 is increased, and the actual engine output is compared with the target engine output. When the engine output is large, the opening degree of the throttle valve 12 is reduced and the opening degree of the throttle valve 12 is controlled to set the actual engine output to a desired target engine output.

  Each exhaust port 20a corresponding to each cylinder 2 is provided with a temperature sensor 21 for detecting the temperature of the exhaust gas E flowing through the exhaust port 20a, and each temperature sensor 21 is provided with the misfire detection means Y. Function as. That is, in the exhaust stroke, normally, the high-temperature exhaust gas E generated by the combustion of the air-fuel mixture M in the cylinder 2 is exhausted to the exhaust port 20a. Therefore, if no misfire has occurred in the cylinder 2, the exhaust port 20a The detected temperature of the temperature sensor 21 provided in is relatively high (for example, 500 ° C.). On the other hand, if a misfire occurs in a certain cylinder 2, the air-fuel mixture M does not burn properly in that cylinder 2, and the high temperature exhaust gas E is not discharged to the exhaust port 20a. Therefore, the temperature sensor 21 provided in the exhaust port 20a. The detected temperature decreases. Therefore, the ECU 30 monitors the detected temperature of each temperature sensor 21 that detects the temperature of the exhaust gas E flowing through each exhaust port 20a, and the detected temperature becomes a predetermined misfire detection temperature (for example, 400 ° C.) or less. In this case, it is determined that misfire has occurred in the cylinder 2 corresponding to the temperature sensor 21.

  In controlling the operation of the engine 100 configured as described above, the ECU 30 executes a predetermined program so as to execute a mixing ratio changing process to be described later in order to avoid a decrease in engine output due to misfire. Details of the control flow including the processing will be described below with reference to FIGS. FIG. 2 shows a control flow of the engine 100. FIG. 3 shows the engine output, the flow rates of the fuels Gh and Gl, and the opening of the throttle valve 12 over time when the misfire of the engine 100 is detected. State changes are shown.

  First, the misfire detection means Y detects the occurrence of misfire in some cylinders 2 (step # 01 in FIG. 2, time t1 in FIG. 3). Specifically, the detected temperature of each temperature sensor 21 is referred to, and the temperature sensor 21 whose detected temperature is equal to or lower than a predetermined misfire detection temperature (for example, 400 ° C.) is specified, and corresponds to the specified temperature sensor 21. The cylinder 2 is determined as the cylinder 2 in which misfire has occurred.

Next, for the cylinder 2 in which the misfire has occurred, it is determined whether or not the misfire continues (step # 2 in FIG. 2, time t2 in FIG. 3). Specifically, when the occurrence of misfire is detected continuously for 50 cycles in the same cylinder 2, it is determined that the misfire occurring in that cylinder 2 is difficult to resolve.
Next, a misfire cylinder deactivation process (step # 03 in FIG. 2) is performed for the specific cylinder 2 in which the occurrence of misfire is continuously detected, in which the state of the specific cylinder 2 is deactivated. Above, the mixing ratio changing process (step # 04 in FIG. 2, from time t2 to time t3 in FIG. 3) for controlling the mixing ratio adjusting means Z to decrease the low heating value fuel mixing ratio is executed, The calorific value of the mixed fuel Gm is increased.
In addition, although the misfire has temporarily occurred, but the misfire has been eliminated for some reason, and for the cylinder 2 in which the occurrence of misfire has not been detected for 50 cycles as described above, the misfire cylinder deactivation process ( Normal operation is continued without executing step # 03) of FIG. 2 and the above-described mixing ratio changing process (step # 04 of FIG. 2).

Specifically, in the misfire cylinder deactivation process (step # 03), the intake valve 3 and the exhaust valve 4 are normally kept closed and sealed for a specific cylinder 2 in which misfire cannot be eliminated. Thus, the power for inhaling the air-fuel mixture M into the cylinder 2 and the power for exhausting the exhaust gas E from the cylinder 2 are hardly consumed.
On the other hand, in the mixing ratio changing process (step # 04), the amount of the low heat value fuel Gl supplied to the mixer 17 is reduced by reducing the opening of the flow rate adjustment valve 16, and the flow rate adjustment valve 15 The supply amount of the high calorific value fuel Gh to the mixer 17 is increased by increasing the opening degree. Then, in the mixed fuel Gm generated by the mixer 17, the mixing ratio of the low calorific value fuel Gl to the high calorific value fuel Gh (low calorific value fuel mixing ratio) decreases, and as a result, the exothermic heat of the mixed fuel Gm The amount will increase.
Therefore, at least in the cylinder 2 in which no misfire has occurred, the mixed fuel Gm whose calorific value has been increased is sucked, so that the engine output obtained from the cylinder 2 in which no misfire has occurred is This increases the output in the cylinder 2 in which misfire has occurred, and as a result, a decrease in the overall engine output due to misfire is favorably avoided.

Further, as shown in FIG. 3, when executing the mixing ratio changing process (step # 04), the engine output is maintained constant in the output control.
Specifically, in the output control at the normal time (before time t1 in FIG. 3) when no misfire has occurred, the target engine output is determined according to the required generated power, and the opening degree of the throttle valve 12 is controlled. Is done. In the output control during the period from the occurrence of misfire to the execution of the mixing ratio changing process (the period from time t1 to t2 in FIG. 3), the opening of the throttle valve 12 is excessive even if the actual engine output decreases. Is fixed to prevent expansion.
In the output control during the period during which the mixture ratio changing process is executed (period t2 to t3 in FIG. 3), the calorific value of the mixed fuel Gm increases due to a decrease in the low calorific value fuel mixing ratio. Since the increase in the engine output due to the increase is limited and the engine output is kept constant, the opening of the throttle valve 12 is reduced.
In the output control in the period after the mixing ratio changing process is completed (period after time t3 in FIG. 3), the target engine output is determined again according to the required generated power. As a result, the opening of the throttle valve 12 is increased until the actual engine output reaches the target engine output in a form that compensates for the engine output that has decreased due to the occurrence of misfire. At the same time, the opening of the throttle valve 12 is increased. In accordance with the increase in the intake air amount due to the above, the supply amount of the high calorific value fuel Gh and the low calorific value fuel Gl, that is, the supply amount of the mixed fuel Gm increases.

[Another embodiment]
Finally, other embodiments of the present invention will be described. Note that the configuration of each embodiment described below is not limited to being applied independently, and can be applied in combination with the configuration of other embodiments as long as no contradiction occurs.
(1) In the above embodiment, the misfire detection means Y detects the temperature of the exhaust gas E discharged from each cylinder 2 to the exhaust port 20a by the temperature sensor 21, and the detected temperature becomes equal to or lower than the predetermined misfire detection temperature. In such a case, the misfire detection unit Y may be configured in another form, although it is determined that misfire has occurred in the cylinder 2 corresponding to the temperature sensor 21. For example, the misfire detection means Y detects a state that changes before and after the occurrence of misfire, such as the pressure of each exhaust port 20a, the pressure of each cylinder 2, or the temperature of each cylinder 2, and the detected pressure or detected temperature is a predetermined value. When it is below the misfire detection value, it can be configured such that it is determined that misfire has occurred in the corresponding cylinder 2.

(2) In the above embodiment, when it is detected that misfires are continuously occurring, the mixture ratio changing process (step # 04 in FIG. 2) is subsequently executed. You may comprise so that a mixing ratio change process may be performed immediately after misfire is detected in some cylinders 2. Moreover, after detecting the occurrence of misfire, a misfire elimination process for eliminating the misfire may be executed once, and the mixture ratio changing process may be executed only when the misfire cannot be eliminated. Note that the misfire elimination processing in this case can include, for example, gradually delaying the ignition timing, which is the timing of spark ignition by the spark plug, or changing the air-fuel ratio to the fuel supply amount increasing side.

(3) In the above embodiment, both the intake valve 3 and the exhaust valve 4 in the cylinder 2 in which misfire has occurred are maintained in a normally closed state when executing the mixture ratio changing process (step # 04 in FIG. 2). Although the misfire cylinder deactivation process (step # 03 in FIG. 2) is executed, another form of misfire cylinder deactivation process may be performed, or the misfire cylinder deactivation process may be omitted.
As another type of misfire cylinder deactivation process, for example, in the cylinder 2 in which misfire has occurred, both the intake valve 3 and the exhaust valve 4 are always open, and the mixture M that is directed from the intake port 10a to the exhaust port 20a is opened. A state in which there is almost no gas flow in one direction can be achieved. Further, when the mixed fuel Gm is directly injected into each intake port 10a or each cylinder 2, the injection of the mixed fuel Gm may be stopped in the misfire cylinder deactivation process.

(4) In the mixing ratio changing process (step # 4 in FIG. 2) described in the above embodiment, the amount of decrease in the low heating value fuel mixing ratio is determined according to the number of cylinders 2 in which the occurrence of misfire has been detected. You may comprise. Specifically, when misfire has occurred in m cylinders 2 out of all n cylinders 2, the calorific value of the mixed fuel Gm is increased by n / (nm) times in the calorific value increase process. The amount of decrease in the low heating value fuel mixture ratio is determined so as to be changed. Then, when the engine output is set to the target engine output in the output control after the heat generation amount increasing process is executed, the output in the nm cylinders 2 in which no misfire has occurred is compared with that before the change. Since the opening is approximately n / (nm) times, the opening of the throttle valve 12 is substantially the same as before the misfire occurs, so that the opening adjustment width of the throttle valve 12 can be maintained at a suitable value. it can.

(5) In the above embodiment, the calorific value of the high calorific value fuel Gh and the low calorific value fuel Gl or the mixed fuel Gm is measured so that the calorific value of the mixed fuel Gm is maintained at a desired target calorific value. The opening degree of the flow rate adjusting valves 15 and 16 may be controlled based on the measurement result.
Further, in the mixing ratio changing process in such a configuration, the opening degree of the flow rate adjusting valve 15 for the high heat value fuel Gh and the flow rate adjusting valve 16 for the low heat value fuel Gl is increased by increasing the target heat value. Controlled, the low heating value fuel mixing ratio is reduced.

(6) In the above embodiment, as two or more kinds of fuels having different calorific values, the high calorific value fuel Gh that is the natural gas city gas 13A and the calorific value per unit volume of the natural gas city gas 13A are higher. Although the low calorific value fuel Gl, which is a small biogas, is used, another two types of fuel or three or more types of fuels having different calorific values may be used.

The present invention includes an engine body having a plurality of cylinders;
Fuel supply means for supplying a mixed fuel obtained by mixing a high calorific value fuel and a low calorific value fuel having a calorific value lower than that of the high calorific value fuel to the engine body;
Misfire detection means for detecting the occurrence of misfire in each cylinder in the engine body;
The present invention can be suitably used as a multi-cylinder mixed combustion engine having a control means for controlling operation.

1: Engine body 2: Cylinder 12: Throttle valve 100: Multi-cylinder mixed combustion engine Gh: High calorific value fuel Gl: Low calorific value fuel Gm: Mixed fuel X: Fuel supply means Y: Misfire detection means Z: Mixing ratio adjusting means

Claims (6)

An engine body having a plurality of cylinders;
Fuel supply means for supplying a mixed fuel obtained by mixing a high calorific value fuel and a low calorific value fuel having a calorific value lower than that of the high calorific value fuel to the engine body;
Misfire detection means for detecting the occurrence of misfire in each cylinder in the engine body;
A multi-cylinder mixed combustion engine having a control means for controlling operation,
A mixing ratio adjusting means capable of adjusting a low heating value fuel mixing ratio, which is a mixing ratio of the low heating value fuel to the high heating value fuel in the mixed fuel;
When the control means detects the occurrence of misfire in some cylinders by the misfire detection means, the control means controls the mixing ratio adjustment means, and the low calorific value of the mixed fuel supplied to the engine body multi-cylinder multi-fuel engine that performs the mixing ratio changing process Ru increase the calorific value of the mixed fuel misfire by reducing the fuel mixing ratio is supplied to the cylinder does not occur.   The multi-cylinder mixed combustion engine according to claim 1, wherein the control unit executes the mixing ratio changing process when the misfire detection unit continuously detects the occurrence of misfire in some cylinders.   3. The multi-cylinder mixed combustion according to claim 1, wherein the control unit executes misfire cylinder deactivation processing for deactivating a specific cylinder in which the occurrence of misfire is detected when performing the mixing ratio changing process. engine.   The control means executes an output control for setting an engine output by controlling an opening degree of a throttle valve provided in an intake passage, and the engine output is controlled in the output control when the mixing ratio changing process is executed. The multi-cylinder mixed combustion engine according to any one of claims 1 to 3, which is kept constant.   The multi-cylinder mixed combustion engine according to any one of claims 1 to 4, wherein the high calorific value fuel is natural gas and the low calorific value fuel is biogas. When the control means executes the mixing ratio changing process, the low heating value fuel mixing ratio of the mixed fuel supplied to the engine body is reduced based on the number of cylinders in which the occurrence of misfire has been detected. The multi-cylinder mixed combustion engine according to any one of claims 1 to 5.

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