JP6938141B2 - Marine diesel engine - Google Patents

Description

The present invention relates to a marine diesel engine.

The marine diesel engine increases the number of revolutions when the operation is started. Since the engine is a rotating machine, there is a critical speed range (Barred Range, Critical Speed) in which resonance occurs and long-term operation in the speed range is prohibited. Patent Document 1 describes that when the engine speed is in the dangerous speed range, the angle at which fuel is injected and the angle at which the exhaust valve for exhausting the air burned in the combustion region is opened are adjusted. .. Specifically, it is described that the exhaust angle in the dangerous rotation speed range is made smaller than the exhaust angle in the region lower than the dangerous rotation speed range.

Utility Model Registration No. 3174346

Further, in a marine diesel engine, in order to shorten the operation time in the dangerous rotation speed range, control for increasing the engine speed in a short time may be executed in the dangerous rotation speed range. When the control to increase the engine speed is executed in this way, the balance between the fuel and air in the engine is lost, the combustion of the fuel becomes insufficient, the speed of increase in the engine speed decreases, and black smoke is generated. There is a risk of doing so.

The present invention solves the above-mentioned problems, and an object of the present invention is to provide a marine diesel engine capable of stabilizing combustion in a dangerous rotation speed range and operating an engine body under better conditions.

The present invention for achieving the above object is a marine diesel engine, which is an engine body that opens and closes an exhaust valve to control exhaust from a combustion chamber, and a load of the engine body that controls the engine body or The engine body includes a control device that controls the operation of the exhaust valve based on an exhaust valve closing timing pattern in which the timing of closing the exhaust valve in the combustion cycle is delayed as the number of revolutions increases. for the rotational speed, the critical rotation range is between passing dangerous speed range, the second range is higher rotational speed than the first range and the critical rotation range is low rotational speed than the critical rotation range The dangerous rotation range is a range in which resonance occurs and long-term operation in the rotation speed range is prohibited, and the exhaust valve closing timing pattern is a range of the dangerous rotation range and the first range. has a point at which the rate of change of the change in the exhaust valve closing timing for the previous SL rotational speed of the rise point of the boundary is changed, the exhaust valve closing timing pattern, the critical rotation than the point where the change rate changes rate of change in range side becomes smaller than the rate of change in the first range side from the point where the change rate changes, and in the second range, as the number of rotation the engine body increases, the first characterized in that after the change rate than the rate of change in the first range is increased the same preparative ing and the rate of change in the first range.

For marine diesel engines, an exhaust valve closing timing pattern is set in which the timing of closing the exhaust valve in the combustion cycle is delayed as the engine speed increases, and the rate of change of the exhaust valve closing timing pattern changes. The rate of change on the dangerous rotation range side is made smaller than the rate of change on the first range side than the point at which the rate of change changes. As a result, the marine diesel engine can perform combustion in a state where a large amount of air is retained in the combustion chamber when the engine body is rotating at a dangerous rotation speed. As a result, combustion in the dangerous rotation speed range can be stabilized. As a result, the speed at which the engine speed increases in the dangerous speed range can be increased, and the generation of black smoke during combustion can be suppressed.

Further, in the exhaust valve closing timing pattern, the load of the engine body calculated by a parameter including the rotation speed and the timing of closing the exhaust valve are associated with each other, and as the load of the engine increases, combustion occurs. It is preferable that the timing of closing the exhaust valve in the cycle is delayed.

Further, in the exhaust valve closing timing pattern, it is preferable that the closing timing of the exhaust valve is constant in the dangerous rotation range.

Further, the exhaust valve closing timing pattern includes the case where the rotation speed of the engine body increases and the case where the rotation speed of the engine body decreases, and the rotation speed of the engine body and the exhaust valve in the dangerous operating range. It is preferable that the timing of closing is different.

According to the present invention, the amount of air in the combustion chamber can be increased even during operation in the dangerous rotation speed range, and combustion in the dangerous rotation speed range can be stabilized. As a result, the speed at which the engine speed increases in the dangerous speed range can be increased, and the generation of black smoke during combustion can be suppressed.

FIG. 1 is a schematic view showing a marine diesel engine equipped with the EGR system of the present embodiment. FIG. 2 is a schematic configuration diagram showing the EGR system of the present embodiment. FIG. 3 is a schematic view showing a schematic configuration of the engine main body of the present embodiment. FIG. 4 is a graph showing the relationship between the engine load and the exhaust valve closing timing. FIG. 5 is a graph showing another example of the relationship between the engine load and the exhaust valve closing timing. FIG. 6 is a graph showing the relationship between the engine speed and the exhaust valve closing timing.

Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. The present invention is not limited to this embodiment, and when there are a plurality of embodiments, the present invention also includes a combination of the respective embodiments.

FIG. 1 is a schematic diagram showing a marine diesel engine equipped with an EGR system, and FIG. 2 is a schematic configuration diagram showing an EGR system.

As shown in FIG. 1, the marine diesel engine 10 of the present embodiment includes an engine body (engine) 11, a supercharger 12, and an EGR system 13.

As shown in FIG. 2, although not shown, the engine body 11 is a propulsion engine (main engine) that drives and rotates the propulsion propeller via the propeller shaft. The engine body 11 is a uniflow sweep-exhaust type cross-head diesel engine, which is a two-stroke diesel engine. It is the one that was made. The engine body 11 includes a plurality of cylinders 21 whose pistons move up and down, a scavenging trunk 22 communicating with each cylinder 21, and an exhaust manifold 23 communicating with each cylinder 21. A scavenging port 24 is provided between each cylinder 21 and the scavenging trunk 22, and an exhaust flow path 25 is provided between each cylinder 21 and the exhaust manifold 23. Then, in the engine body 11, the air supply line G1 is connected to the scavenging trunk 22, and the exhaust line G2 is connected to the exhaust manifold 23.

FIG. 3 is a schematic view showing the engine main body. FIG. 3 shows a portion of the engine body 11 corresponding to one piston and a cylinder 21. The engine main body 11 has a base plate 111 located below, a frame 112 provided on the base plate 111, and a cylinder jacket 113 provided on the frame 112. The base plate 111, the frame 112, and the cylinder jacket 113 are integrally fastened and fixed by a plurality of tension bolts (tie bolts / connecting members) 114 and nuts 115 extending in the vertical direction.

The cylinder jacket 113 is provided with a cylinder liner 116, and a cylinder cover 117 is provided at the upper end of the cylinder liner 116. The cylinder liner 116 and the cylinder cover 117 partition the space 118, and the piston 119 is provided in the space 118 so as to be reciprocating up and down, thereby forming the combustion chamber 120. Further, the cylinder cover 117 is provided with an exhaust valve (exhaust gas valve) 121. The exhaust valve 121 opens and closes the combustion chamber 120 and the exhaust gas pipe 122. The exhaust valve 121 may have a function of opening and closing the combustion chamber 120 and the exhaust gas pipe 122, and does not necessarily have to be provided at the center of the cylinder cover 117.

Therefore, the combustion chamber 120 is burned by supplying the fuel supplied from the fuel injection pump and the combustion gas compressed by the supercharger 12. Then, the piston 119 moves up and down by the energy generated by this combustion. At this time, when the combustion chamber 120 is opened by the exhaust valve 121, the exhaust gas generated by the combustion is pushed out to the exhaust gas pipe 122, while the combustion gas is introduced into the combustion chamber 120 from the scavenging port 24. The exhaust gas pipe 122 is connected to the exhaust manifold 23.

The piston 119 is connected to the upper end of the piston rod 123 and is movably connected together with the piston rod 123 in the piston axial direction. The base plate 111 is a crankcase, and is provided with a bearing 125 that rotatably supports the crankshaft 124. Further, in the crankshaft 124, the lower end portion of the connecting rod 127 is rotatably connected via the crank 126. In the frame 112, a pair of guide plates 128 extending in the vertical direction are fixed at predetermined intervals, and a crosshead 129 is movably supported between the pair of guide plates 128. The crosshead 129 is connected so that the crosshead bearing that connects the lower half of the crosshead pin provided at the lower end of the piston rod 123 to the upper end of the connecting rod 127 is rotatable.

Therefore, the piston 119 to which the energy generated in the combustion chamber 120 of the cylinder jacket 113 is transmitted, together with the piston rod 123, faces the installation surface of the engine body 11 (direction toward the base plate 111, that is, downward in the piston axial direction). ). Then, the piston rod 123 pushes down the crosshead 129 in the piston axial direction, and rotates the crankshaft 124 via the connecting rod 127 and the crank 126.

The engine body 11 is provided with a rotation speed detection unit 62 and a fuel input amount detection unit 64. The rotation speed detection unit 62 detects the rotation speed of the engine body 11 (the rotation speed of the rotation shaft connected to the propeller shaft). The rotation speed detection unit 62 may detect the rotation speed of the rotation shaft inserted into the engine body 11, or may detect the rotation speed of the propeller shaft. The fuel input amount detection unit 64 detects the fuel input amount of the engine body 11.

The engine control device 26 controls the operation of the engine body 11. The engine control device 26 controls the operation of the engine body 11 based on various input conditions such as a required load and the results detected by various sensors such as the rotation speed detection unit 62 and the fuel input amount detection unit 64. The engine control device 26 controls the fuel injection timing to the cylinder 21, the injection amount, and the opening / closing timing of the exhaust valve 121 to control the fuel input amount and the rotation speed of the engine body 11, and the combustion in the combustion chamber 120. .. The engine control device 26 controls the output of the engine body 11 by controlling the fuel input amount and the rotation speed.

The supercharger 12 is configured by connecting a compressor (compressor) 31 and a turbine 32 so as to rotate integrally by a rotating shaft 33. In the supercharger 12, the turbine 32 is rotated by the exhaust gas discharged from the exhaust line G2 of the engine main body 11, the rotation of the turbine 32 is transmitted by the rotating shaft 33, the compressor 31 is rotated, and the compressor 31 is air and At least one of the recirculated gas is compressed and supplied as the compressed compressed gas from the air supply line G1 to the engine body 11. The compressor 31 is connected to a suction line G6 that sucks air from the outside (atmosphere).

The supercharger 12 is connected to an exhaust line G3 that discharges exhaust gas that has rotated the turbine 32, and the exhaust line G3 is connected to a chimney (funnel) (not shown). Further, an EGR system 13 is provided between the exhaust line G3 and the air supply line G1.

The EGR system 13 includes exhaust gas recirculation lines G4, G5, G7, a scrubber 42, a demista unit 14, an EGR blower (blower) 47, and an EGR control device 60. In this EGR system 13, a part of the exhaust gas discharged from the engine body 11 is mixed with air as a recirculation gas, then compressed by a supercharger 12 and recirculated to the marine diesel engine 10 as a combustion gas. , It suppresses the generation of NOx due to combustion. Here, a part of the exhaust gas is extracted from the downstream side of the turbine 32, but a part of the exhaust gas may be extracted from the upstream side of the turbine 32.

In the following description, the exhaust gas is a gas that is discharged from the engine body 11 to the exhaust line G2 and then discharged to the outside from the exhaust line G3. The recirculated gas refers to a part of the exhaust gas separated from the exhaust line G3. The recirculated gas is returned to the engine body 11 by the exhaust gas recirculation lines G4, G5, and G7.

One end of the exhaust gas recirculation line G4 is connected to the middle part of the exhaust line G3. The exhaust gas recirculation line G4 is provided with an EGR inlet valve (open / close valve) 41A, and the other end is connected to the scrubber 42. The EGR inlet valve 41A turns on / off the exhaust gas diverted from the exhaust line G3 to the exhaust gas recirculation line G4 by opening and closing the exhaust gas recirculation line G4. The EGR inlet valve 41A may be used as a flow rate adjusting valve to adjust the flow rate of the exhaust gas passing through the exhaust gas recirculation line G4.

The scrubber 42 is a Venturi type scrubber, and includes a hollow throat portion 43, a venturi portion 44 into which exhaust gas is introduced, and an expansion portion 45 that gradually returns to the original flow velocity. The scrubber 42 includes a water injection unit 46 that injects water into the recirculated gas introduced into the venturi unit 44. The scrubber 42 is connected to an exhaust gas recirculation line G5 that discharges a recirculation gas from which harmful substances such as fine particles (PM) such as SOx and soot and dust have been removed and wastewater containing the harmful substances. In this embodiment, the Venturi type is adopted as the scrubber, but the scrubber is not limited to this configuration. Further, the marine diesel engine 10 may be provided with an exhaust gas cleaning device other than the scrubber 42.

The exhaust gas recirculation line G5 is provided with a demista unit 14 and an EGR blower 47.

The demista unit 14 separates the recirculated gas from which harmful substances have been removed by water injection and wastewater. The demista unit 14 is provided with a drainage circulation line W1 that circulates drainage to the water injection portion 46 of the scrubber 42. The drainage circulation line W1 is provided with a hold tank 49 and a pump 50 for temporarily storing mist (drainage).

The EGR blower 47 sends the recirculated gas in the scrubber 42 from the exhaust gas recirculation line G5 to the compressor 31 via the demister unit 14.

One end of the exhaust gas recirculation line G7 is connected to the EGR blower 47, and the other end is connected to the compressor 31 via a mixer (not shown). The EGR blower 47 sends the recirculated gas to the compressor 31. Be done. The exhaust gas recirculation line G7 is provided with an EGR outlet valve (off-off valve or flow rate adjusting valve) 41B. The air from the intake line G6 and the recirculated gas from the exhaust gas recirculation line G7 are mixed by a mixer to generate a combustion gas. The mixer may be provided separately from the silencer, or the silencer may be configured so as to add a function of mixing the recirculated gas and air without separately providing the mixer. Then, the supercharger 12 can supply the combustion gas compressed by the compressor 31 from the air supply line G1 to the engine main body 11, and the air cooler (cooler) 48 is provided in the air supply line G1. The air cooler 48 cools the combustion gas by exchanging heat between the combustion gas compressed by the compressor 31 and having a high temperature and the cooling water. Further, in the EGR system 13, an oxygen concentration detecting unit 66 is arranged on the air supply line G1 or the scavenging trunk 22. The oxygen concentration detection unit 66 of the present embodiment is arranged closer to the engine body 11 than the air cooler 48. The oxygen concentration detection unit 66 detects the oxygen concentration of the air supplied to the engine body 11, that is, the oxygen concentration of the combustion gas when the EGR system 13 is operating.

The EGR control device 60 controls the operation of each part of the EGR system 13. The EGR control device 60 acquires load information from the engine control device 26. The EGR control device 60 sends ON / OFF information of the EGR system 13 to the engine control device 26. The EGR control device 60 acquires the rotation speed information of the engine body 11 from the rotation speed detection unit 62. The EGR control device 60 acquires information on the fuel input amount of the engine main body 11 from the fuel input amount detection unit 64. The EGR control device 60 acquires information on the oxygen concentration of the combustion gas supplied from the oxygen concentration detection unit 66 to the engine body 11. The EGR control device 60 supplies the EGR blower 47 to the engine body 11 from the EGR system 13 based on the acquired load information of the engine body 11 and the oxygen concentration of the air supplied to the engine body 11. Control the amount of circulating gas. The EGR control device 60 stores the relationship between the load of the engine body 11 and the target value of the oxygen concentration, and calculates the target value of the oxygen concentration according to the load. The EGR control device 60 calculates a target value of oxygen concentration based on the relationship between the load of the engine body 11 and the target value of oxygen concentration, and the relationship between the calculated target value of oxygen concentration and the acquired oxygen concentration and the present The frequency (operating frequency) of the EGR blower 47 is calculated based on the frequency of the EGR blower 47 of the above. The EGR control device 60 rotates the EGR blower 47 at the calculated frequency of the EGR blower 47. The EGR control device 60 also controls each part other than the EGR blower 47, for example, the opening and closing of the EGR inlet valve 41A and the EGR outlet valve 41B, and the operation of the scrubber 42.

Hereinafter, the operation of the EGR system 13 of the present embodiment will be described. As shown in FIG. 2, when the combustion gas is supplied from the scavenging trunk 22 into the cylinder 21, the combustion gas is compressed by the piston, and fuel is supplied to the high temperature combustion gas. By injecting, it spontaneously ignites and burns. Then, the generated combustion gas is discharged from the exhaust manifold 23 to the exhaust line G2 as exhaust gas. The exhaust gas discharged from the engine body 11 is discharged to the exhaust line G3 after rotating the turbine 32 in the supercharger 12, and when the EGR inlet valve 41A and the EGR outlet valve 41B are closed, the entire amount is exhausted to the exhaust line. It is discharged to the outside from G3.

On the other hand, when the EGR inlet valve 41A and the EGR outlet valve 41B are open, a part of the exhaust gas flows from the exhaust line G3 to the exhaust gas recirculation line G4 as a recirculation gas. Hazardous substances are removed from the recirculated gas flowing through the exhaust gas recirculation line G4 by the scrubber 42. That is, when the recirculation gas passes through the Venturi section 44 at high speed, the scrubber 42 injects water from the water injection section 46 to cool the recirculation gas with the water and drop harmful substances together with the water. To remove. Then, the mist (drainage) containing the harmful substance flows into the demista unit 14 together with the recirculated gas.

The recirculated gas from which harmful substances have been removed by the scrubber 42 is discharged to the exhaust gas recirculation line G5, and after the mist (drainage) is separated by the demista unit 14, it is sent to the supercharger 12 by the exhaust gas recirculation line G7. .. Then, this recirculated gas is mixed with the air sucked from the suction line G6 to become a combustion gas, compressed by the compressor 31 of the supercharger 12, cooled by the air cooler 48, and cooled from the air supply line G1 to the engine. It is supplied to the main body 11.

Next, the control of the engine body 11 executed by the engine control device 26 of the marine diesel engine 10 will be described with reference to FIG. FIG. 4 is a graph showing the relationship between the engine load and the exhaust valve closing timing. The engine control device 26 changes the exhaust valve closing timing according to the engine load based on the exhaust valve closing timing pattern which is the relationship between the engine load and the exhaust valve closing timing shown in FIG. The exhaust valve closing timing is the timing at which the exhaust valve is closed in the combustion cycle, and can be indicated by the angle of the combustion cycle. The exhaust valve closing timing pattern 210 shown by the solid line in FIG. 4 shows the relationship between the engine load and the exhaust valve closing timing of the present embodiment. The exhaust valve closing timing pattern 212 shown by the dotted line in FIG. 4 shows the relationship between the engine load of the comparative example and the exhaust valve closing timing. The exhaust valve closing timing patterns 210 and 212 both have a relationship in which the exhaust valve closing timing is delayed as the engine load increases. The engine control device 26 detects the engine load and controls the exhaust valve closing timing, which is the timing for closing the exhaust valve 121, based on the relationship between the detected engine load and the exhaust valve closing timing pattern 210 shown by the solid line in FIG.

As described above, the timing of closing the exhaust valve 121 is controlled based on the angle at which one stroke of the piston of the engine body 11 is 360 degrees, that is, the crank angle. That is, the engine control device 26 opens the exhaust valve 121 when the crank angle reaches the set angle. When the timing of closing the exhaust valve 121 is delayed, the exhaust valve 121 is closed at a larger crank angle.

In the exhaust valve closing timing pattern 212 of the comparative example, the rate of change, which is the amount of change in the exhaust valve closing timing with respect to the amount of change in the engine load, is constant. In the comparative example of FIG. 4, the rate of change is constant, but the amount of change may change. Here, the exhaust valve closing timing pattern 212 is an ideal line set based on the result of calculating the exhaust valve closing timing at which the engine performance such as fuel consumption is improved at each engine load without considering the dangerous rotation speed. This is the relationship between the engine load and the exhaust valve closing timing. Here, the ideal line first determines the maximum combustion pressure from the design output of the engine. From there, the combustion pressure of each load is determined, the compression pressure is designed from the combustion pressure, and the planned exhaust valve closing timing is determined so as to reach the compression pressure. After that, it is changed and adjusted near the planned exhaust valve closing timing by a trial run, and the exhaust valve closing timing is determined so that parameters such as fuel consumption and exhaust gas outlet temperature are optimized. The exhaust valve closing timing described above is performed for each load, and the optimum exhaust valve closing timing angle is determined for each load. The exhaust valve closing timing pattern 212 is finely adjusted and determined so that the timing of each load is smoothly connected at this time.

The exhaust valve closing timing pattern 210 of the present embodiment has a dangerous rotation range 220 in which the engine load overlaps with the dangerous rotation speed range (a range of engine load A ₁ or more and engine load A ₂ or less), and is larger than the dangerous rotation range 220. The first range 222, which is a range where the engine load is small ( _{the range less than the engine load A 1} ), and the second range 224, which is the range where the engine load is larger than the dangerous rotation range 220 ( _{the range larger than the engine load A 2).} The rate of change in the amount of change in the exhaust valve closing timing with respect to the engine load is different. Here, the engine load A ₂ is a load higher than the engine load A _1. In addition, the engine load changes depending on the engine speed, the amount of fuel input, and the like. The dangerous rotation speed range is a load range in which the rotation speed becomes the dangerous rotation speed range in consideration of the change width of the fuel input amount that changes under various conditions. The engine load A ₁ is calculated based on the minimum value of the fuel input amount assumed in the dangerous rotation speed range and the minimum value of the dangerous rotation speed. The engine load A ₂ is calculated based on the maximum value of the fuel input amount assumed in the dangerous rotation speed range and the maximum value of the dangerous rotation speed. The engine load is calculated based on parameters other than the fuel input amount and the number of revolutions of the engine body 11.

Exhaust valve closing timing pattern 210, there are 2 30 that a change in the rate of change in the engine load A _1, there is 232 points you change the rate of change in the engine load A _2, it is higher than the engine load A ₂ the rate of change in the engine load _{A 3} there is to that point 234 change. The exhaust valve closing timing pattern 210 has a line segment 240 at a portion where the engine load is lower than the point 230 (engine load A ₁ ) where the rate of change changes, and the point 230 (engine load A ₁ ) where the rate of change changes and the rate of change. between There is next segment 242 between points changes 232 (engine load _{a 2),} and 232 that the rate of change varies point (engine load _{a 2)} and the change rate changes 234 (engine load _{a 3)} There next line segment 244, a portion the engine load is higher than the point change rate changes 234 (engine load _{a 3)} the segment 246. The line segment 240 and the line segment 246 have the same inclination as the exhaust valve closing timing pattern 212. The line segment 242 connects the line segment 240 and the line segment 244, and the rate of change does not change, that is, the exhaust valve closing timing does not change. The line segment 244 connects the line segment 242 and the line segment 246, and the rate of change is larger than that of the line segment 242 and the line segment 246. Therefore, in the exhaust valve closing timing pattern 210, the dangerous rotation range 220 including the time when the engine load (the rotation speed of the engine body 11) passes through the dangerous rotation speed range, and the first rotation speed lower than the dangerous rotation speed range 220. In the range 222, there is a point 230 where the rate of change of the change in the timing of closing the exhaust valve with respect to the increase in the number of revolutions changes, and the line segment on the dangerous rotation range 220 side of the point 230 where the rate of change changes. the rate of change of frequency 242 is smaller than the change rate of the first range 222 side of the line segment 240 than 230 points the rate of change changes.

By controlling the exhaust valve closing timing based on the exhaust valve closing timing pattern 210, the engine control device 26 controls the exhaust valve closing timing in the dangerous rotation range 220 earlier than when operating in the exhaust valve closing timing pattern 212. Become. As a result, when operating at a dangerous rotation speed, the excess oxygen rate during fuel combustion in the combustion chamber 120 is proportional to the increase in the load (rotation speed) of the engine body 11 as compared with the case other than the dangerous rotation speed range 220. Can be suppressed. It is possible to suppress a decrease in the excess oxygen rate of the combustion chamber 120 under the same load as in the case of operating with the exhaust valve closing timing pattern 212.

The engine control device 26 can increase the amount of oxygen in response to an increase in the amount of fuel supplied to the combustion chamber 120 even if the load increases in the dangerous rotation range 220, and can suppress a decrease in the excess air rate. Combustion of fuel can be preferably performed. Specifically, the engine control device 26 increases the fuel input amount, increases the output generated by combustion, and accelerates the rotation speed in a short time in order to pass the load in the dangerous rotation range 220 in a short time. Execute the process. By executing this process, the engine control device 26 increases the fuel input amount. Here, in the diesel engine system 10, since the rotation speed of the turbocharger 12 increases as the engine load increases, the amount of air supplied per unit time increases, but in the dangerous rotation range 220, the fuel increases. The increase in the rotation speed of the supercharger 12 tends to decrease with respect to the increase, and when the exhaust valve closing timing changes in the same manner as in other regions, the amount of oxygen for the fuel decreases. The engine control device 26 controls the exhaust valve closing timing based on the exhaust valve closing timing pattern 210, so that even if the fuel input amount increases, the amount of air is increased in response to the increase in the fuel supplied to the combustion chamber 120. Since a large amount can be retained, it is possible to suppress a decrease in oxygen with respect to the fuel supplied to the combustion chamber 120. As a result, oxygen is reduced with respect to the fuel, and it is possible to suppress instability of combustion, and it is possible to suppress the generation of black smoke due to incomplete combustion. Further, since the combustion can be stably executed, a desired output can be obtained and the rotation speed can be suitably increased. In particular, in the marine diesel engine 10 of the present embodiment, by operating the EGR system 13, the oxygen concentration of the air supplied to the combustion chamber 120 becomes low, and the risk of combustion instability and black smoke generation increases. By controlling the exhaust valve closing timing based on the exhaust valve closing timing pattern 210, it is possible to suppress the instability of combustion and the generation of black smoke due to incomplete combustion. Further, since the combustion can be stably executed, a desired output can be obtained and the rotation speed can be suitably increased.

The exhaust valve closing timing pattern 210 sets the closing timing of the exhaust valve in the dangerous rotation range 220 to be constant, so that the amount of oxygen retained in the combustion chamber 120 even if the engine load increases in the dangerous rotation range 220 is determined. The amount can be equal to or greater than the condition where the engine load is small. Further, by keeping the closing timing of the exhaust valve in the dangerous rotation range 220 constant, the parameter can be easily set and the control can be simplified. The operation of the engine body 11 can be stabilized by being able to easily control the engine.

Further, the exhaust valve closing timing pattern 210 is calculated so as to be an ideal line except for the line segment 242 of the dangerous rotation range 220 and the line segment 244 that brings the exhaust valve closing timing pattern 210 closer to the exhaust valve closing timing pattern 212. It is preferable to use a pattern that matches the valve closing timing pattern 212. As a result, the engine body 11 can be operated more efficiently in a load range other than the dangerous rotation speed range 220.

Here, in the exhaust valve closing timing pattern 210, the rate of change of the line segment 242 is preferably close to zero. As a result, when the load of the engine body 11 increases or decreases within the range of the line segment 242, the fluctuation of the exhaust valve closing timing becomes too large, and it is possible to prevent the operation of the engine body 11 from becoming unstable.

Further, the exhaust valve closing timing pattern 210 associates the load of the engine body 11 calculated by the parameter including the rotation speed with the timing of closing the exhaust valve, and as the load of the engine body 11 increases, the exhaust gas in the combustion cycle is exhausted. The operating efficiency of the engine body 11 can be improved by delaying the timing of closing the valve.

Here, the exhaust valve closing timing pattern 210 keeps the exhaust valve closing timing constant in the dangerous rotation range 220, but the present invention is not limited to this. Further, the engine control device 26 may switch the exhaust valve closing timing pattern 210 to be applied depending on whether the load increases (increases) or decreases.

FIG. 5 is a graph showing another example of the relationship between the engine load and the exhaust valve closing timing. Hereinafter, another example of the exhaust valve closing timing pattern will be described with reference to FIG. The engine control device 26 that uses the relationship between the engine load and the exhaust valve closing timing of FIG. 5 has an exhaust valve closing timing pattern 250 and an exhaust valve closing timing pattern 252. The exhaust valve closing timing pattern 250 is a relationship between the engine load and the exhaust valve closing timing, which is applied when the engine load increases. The exhaust valve closing timing pattern 252 is a relationship between the engine load and the exhaust valve closing timing, which is applied when the engine load is reduced.

Exhaust valve closing timing pattern 250, there is 230a point you change the rate of change in the engine load _{A 1,} there is 232a point change rate you change in engine load _{A 2,} it is higher than the engine load _{A 2} the rate of change in the engine load _{A 3} there is to that point 234a changes. In the exhaust valve closing timing pattern 250, the line segment 240a is a portion where the engine load is lower than the point 230a (engine load A ₁ ) where the rate of change changes, and the point 230a (engine load A ₁ ) where the rate of change changes and the rate of change. Is a line segment 242a between the changing rate of 232a (engine load A ₂ ), and between the point where the rate of change changes 232a (engine load A ₂ ) and the point where the rate of change changes 234a (engine load A ₃ ). line 244a, and the engine load is high portion becomes a segment 246a than 234a that change rate changes (engine load _{a 3).} The line segment 240a and the line segment 246a have the same inclination as the exhaust valve closing timing pattern 210 and the same inclination as the exhaust valve closing timing pattern calculated based on the ideal line. The line segment 242a connects the line segment 240a and the line segment 244a, and the exhaust valve closing timing is delayed as the load increases. The rate of change of the line segment 242a is smaller than that of the line segment 240a. That is, the slope of the line segment 242a is smaller than that of the line segment 240a in the graph in which the vertical axis shown in FIG. 5 is the angle of the exhaust valve closing timing and the horizontal axis is the load of the engine body 11. The line segment 244a connects the line segment 242a and the line segment 246a, and the rate of change is larger than that of the line segment 242a and the line segment 246a.

As described above, in the exhaust valve closing timing pattern 250, the rate of change of the line segment 242a is not 0, but the dangerous rotation range 220 including the time when the engine load (rotational speed of the engine body) passes through the dangerous rotation speed range. The first range 222, which has a lower rotation speed than the dangerous rotation range 220, has a point 230a in which the change rate of the change in the timing of closing the exhaust valve with respect to the increase in the rotation speed changes, and the change rate changes. rate of change of the critical rotation range 220 side of the line segment 242a than changing point 230a satisfies the smaller relation than even the rate of change of the first range 222 side of the line segment 240a from 230a that change rate changes. The engine control unit 26, the rate of change of 230a segment of critical rotation range 220 side from 242a that the rate of change of the line segment 242a is also the rate of change varies if it is not zero, than 230a that change rate changes The same effect as described above can be obtained by satisfying a relationship smaller than the rate of change of the line segment 240a on the first range 222 side. Further, in the exhaust valve closing timing pattern 250, the operation of the engine body 11 in the dangerous rotation range 220 may be more unstable than in the case of the exhaust valve closing timing pattern 210, but the operation efficiency may be improved. can.

Exhaust valve closing timing pattern 252, there is a point change rate you change in load is small engine load A ₄ than the engine load A _1, there is a point you change the rate of change in the engine load A _1, the engine load A There is a point where the rate of change changes at _2. Exhaust valve closing timing pattern 252, the engine load _{A 4} engine load than lower portion line 240b, and the can next to the line segment 248 between the engine load _{A 4} and engine load _{A 1,} the engine load _{A 1} and engine load The line segment 244b is connected to _{A 2,} and the line segment 246b is a portion where the engine load is higher than _{the engine load A 2.} The line segment 240b and the line segment 246b have the same inclination as the exhaust valve closing timing pattern 250 and the same inclination as the exhaust valve closing timing pattern calculated based on the ideal line. The line segment 248 connects the line segment 240b and the line segment 244b, and the rate of change is larger than that of the line segment 240b and the line segment 244b. The line segment 244b connects the line segment 248 and the line segment 246b, and the exhaust valve closing timing does not change even if the load changes. The rate of change of the line segment 244b is 0.

When the load of the engine body 11 is reduced, for example, when the engine body 11 is stopped from a state of navigating at a predetermined ship speed, the engine control device 26 determines the exhaust valve closing timing based on the exhaust valve closing timing pattern 252. To control. When the load of the engine body 11 is reduced, the engine control device 26 uses less fuel in the dangerous rotation range 220, and therefore, as shown in the exhaust valve closing timing pattern 252, the change rate is higher than the point 230a where the rate of change changes. By satisfying the relationship that the change rate of the line segment 244b on the dangerous rotation range 220 side is smaller than the change rate of the line segment 248 on the first range 222 side than the point 230a where the change rate changes, the change rate in the dangerous rotation range 220 is satisfied. Fluctuations in the exhaust valve closing timing can be suppressed. As a result, it is possible to suppress a sudden change in the excess oxygen rate in the dangerous rotation range 220, and it is possible to stabilize combustion.

The engine control device 26 sets the exhaust valve closing timing pattern as the rotation speed of the engine body 11 in the dangerous operating range 220 and the exhaust valve when the rotation speed of the engine body increases and when the rotation speed of the engine body decreases. By using a relationship different from the closing timing, the engine body 11 can be operated more stably.

Further, in the above embodiment, the exhaust valve closing timing is controlled based on the engine load, but the present invention is not limited to this. The engine control device may control the exhaust valve closing timing based on the rotation speed of the engine body 11. FIG. 6 is a graph showing the relationship between the engine speed and the exhaust valve closing timing. FIG. 6 also shows an exhaust valve closing timing pattern 262, which is a relationship between the engine speed and the exhaust valve closing timing calculated on the ideal line as in FIG. The exhaust valve closing timing pattern 260 shown in FIG. 6 has a dangerous rotation range 220a, which is a range in which the rotation speed of the engine body overlaps with the dangerous rotation speed range (a range of engine rotation speed B ₁ or more and engine rotation speed B _{2 or less), and danger.} range is less the engine speed than the rotation range 220a first range 222a and the range the engine speed is greater than the critical rotation range 220a is (range of less than the engine rotational speed B ₁₎ (engine speed B ₂ larger range) The rate of change in the amount of change in the exhaust valve closing timing with respect to the engine speed is different between the second range 224a and the engine speed. Here, the engine speed B ₂ is a speed higher than the _{engine speed B 1.}

Exhaust valve closing timing pattern 260, there is 230c point change rate you change in engine speed _{B 1,} there is 232c point change rate you change in engine speed _{B 2,} higher than the engine rotational speed _{B 2} there is 234c point change rate you change in engine speed B ₃ is the value. In the exhaust valve closing timing pattern 260, the line segment 240c is located at a portion where the engine speed is lower than the point 230c (engine speed B ₁ ) at which the rate of change changes, and the point 230c (engine speed B ₁ ) at which the rate of change changes. is next segment 242c, 232c that the rate of change varies point (engine speed _{B 2)} and the change rate is changed 234c (engine speed between 232c point change rate changes (engine speed _{B 2)} and The _{line segment 244c is connected to B 3} ), and the line segment 246c is a portion where the engine speed is higher than the point 234c (engine speed B ₃ ) where the rate of change changes. The line segment 240c and the line segment 246c have the same inclination as the exhaust valve closing timing pattern 262. The line segment 242c connects the line segment 240c and the line segment 244c, and the rate of change does not change, that is, the exhaust valve closing timing does not change. The line segment 244c connects the line segment 242 and the line segment 246, and the rate of change is larger than that of the line segment 242c and the line segment 246c. Therefore, in the exhaust valve closing timing pattern 260, the engine rotation speed (the rotation speed of the engine body) is the first danger rotation speed range 220a including the time when the engine rotation speed passes through the danger rotation speed range, and the rotation speed is lower than the danger rotation speed range 220a. In the range 222a, there is a point 230c where the rate of change of the change in the timing of closing the exhaust valve with respect to the increase in the number of revolutions changes, and the line on the dangerous rotation range 220a side of the point 230c where the rate of change changes. min 242c rate of change is less than the rate of change of the first range 222a side of the line segment 240c than 230c that change rate changes.

By controlling the exhaust valve closing timing based on the exhaust valve closing timing pattern 260, the engine control device 26 has an earlier exhaust valve closing timing in the dangerous rotation range 220a than when operating in the exhaust valve closing timing pattern 262. Become. As a result, when the engine is operated at a dangerous rotation speed, the fuel is burned in the combustion chamber 120 in proportion to the increase (increase) in the load (rotation speed) of the engine body 11 as compared with the case other than the dangerous rotation speed range 220a. It is possible to suppress a decrease in the excess oxygen rate of the engine. That is, it is possible to reduce the decrease in the amount of oxygen with respect to the fuel to be input, and it is possible to increase the amount of oxygen in the combustion chamber 120 with the same load as in the case of operating with the exhaust valve closing timing pattern 262. As described above, even if the engine control device 26 controls based on the rotation speed of the engine body 11 instead of the engine load, the same effect as in the case of the engine load can be obtained.

Further, in addition to the exhaust valve closing timing, the engine control device 26 may change the rate of change of the exhaust valve opening timing, which is the timing of opening the exhaust valve, between the dangerous rotation speed range and other rotation speed ranges.

Further, in the above embodiment, the internal combustion engine provided with EGR is taken as an example, but the present invention is also applied to an internal combustion engine not provided with EGR.

10 Marine diesel engine 11 Engine body 12 Supercharger 13 EGR system 14 Demista unit 26 Engine controller 41A EGR inlet valve 41B EGR outlet valve 42 Scrubber 47 EGR blower 48 Air cooler (cooler)
60 EGR control device 62 Rotation speed detection unit 64 Fuel input amount detection unit 66 Oxygen concentration detection unit 111 Base plate 112 Frame 113 Cylinder jacket 114 Tension bolt (tie bolt / connecting member)
115 Nut 116 Cylinder Liner 117 Cylinder Cover 118 Space 119 Piston 120 Combustion Chamber 121 Exhaust Valve 122 Exhaust Pipe 123 Piston Rod 124 Crankshaft 125 Bearing 126 Crank 127 Connecting Rod 128 Guide Plate 129 Crosshead

Claims (4)

The engine body that opens and closes the exhaust valve to control the exhaust from the combustion chamber,
The engine body is controlled, and the operation of the exhaust valve is controlled based on the exhaust valve closing timing pattern in which the timing of closing the exhaust valve in the combustion cycle is delayed as the load or the rotation speed of the engine body increases. With a control device,
The engine body is for the rotational speed, the critical rotation range is between passing critical rotation range, the rotation speed than the first range and the critical rotation range is low rotational speed than the critical rotation range Has a high second range,
The dangerous rotation range is a range in which resonance occurs and long-term operation in the rotation speed range is prohibited.
The exhaust valve closing timing pattern has a point at which the critical rotation range and the exhaust valve closing rate of change of the change in the timing for rising of the previous SL rotational speed to a point of the boundary between the first range is changed,
In the exhaust valve closing timing pattern, the rate of change on the dangerous rotation range side is smaller than the point at which the rate of change changes, and the rate of change on the first range side is smaller than the point at which the rate of change changes.
In the second range, in accordance with the higher number of rotation the engine body, the same as that Do and the rate of change in the first range is larger rate of change than the change rate in the first range A marine diesel engine that features that. In the exhaust valve closing timing pattern, the load of the engine body calculated by a parameter including the rotation speed and the timing of closing the exhaust valve are associated with each other.
The marine diesel engine according to claim 1, wherein the timing of closing the exhaust valve in the combustion cycle is delayed as the load of the engine body increases. The marine diesel engine according to claim 1 or 2, wherein the exhaust valve closing timing pattern is characterized in that the closing timing of the exhaust valve is constant in the dangerous rotation range. The exhaust valve closing timing pattern, the in the case where the number of the rotating engine body increases, the the number of rotation the engine body of the critical rotation range and if the number of the rotary engine body decreases the exhaust valve The marine diesel engine according to any one of claims 1 to 3, wherein the timing of closing the engine is different from that of the engine.

Images