JP2013194712A - Method for controlling internal combustion engine, and internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an internal combustion engine in which a cooling loss is reduced and thermal efficiency is improved, and a method for controlling the same.SOLUTION: A method for controlling an internal combustion engine (engine 1) includes a step of spraying fuel in a combustion chamber 17 of the internal combustion engine in a direction from a central part of the combustion chamber to an outer peripheral part, a step of adding ozone to air in the combustion chamber, and a step of accelerating combustion in the combustion chamber by the addition of the ozone and thereby ending the combustion before flames spreading in a direction from the central part of the combustion chamber to an external peripheral part together with the sprayed fuel reach a surface of a wall partitioning the combustion chamber.

Description

  The technology disclosed herein relates to an internal combustion engine control method and an internal combustion engine.

  For example, Patent Document 1 describes an engine configured to inject an air-fuel mixture including both gasoline and light oil by compression self-ignition by injecting gasoline into an intake port and injecting light oil into a combustion chamber. Has been. This engine is provided with ozone supply means for supplying ozone upstream of the gasoline injection position at the intake port, so that the ignitability of gasoline, which is less ignitable than light oil, is enhanced by the addition of ozone. I have to. Further, in the engine disclosed in Patent Document 1, the addition of ozone is performed when the operating state is in the low load region.

JP 2011-157940 A

  Incidentally, it is conceivable to reduce the cooling loss as one of the measures for increasing the thermal efficiency of the internal combustion engine. The cooling loss increases when the combustion flame in the combustion chamber comes into contact with the wall surface that defines the combustion chamber. Therefore, if the contact between the flame and the wall surface is suppressed, the cooling loss can be reduced.

  The technology disclosed herein has been made in view of the above points, and an object of the technology is to realize an internal combustion engine that has reduced cooling loss and thereby improved thermal efficiency, and a control method thereof. is there.

  The technology disclosed herein relates to a control method for an internal combustion engine. The control method includes a step of injecting fuel spray from the center of the combustion chamber toward the outer periphery in the combustion chamber of the internal combustion engine, The step of adding ozone to the intake air to be introduced, and the flame that spreads in the direction from the center of the combustion chamber to the outer periphery along with the flight of the fuel spray by accelerating combustion in the combustion chamber by adding ozone to the intake air Includes a step of terminating the combustion before reaching the wall surface defining the combustion chamber.

  According to this configuration, by adding ozone to the intake air, combustion in the combustion chamber is accelerated by its strong oxidizing action. That is, after the fuel is injected, the ignition delay time until the air-fuel mixture ignites is shortened, and the combustion period from the start of combustion to the end of combustion is also shortened. The timing of adding ozone to the intake air is not particularly limited, and ozone may be added before introducing the intake air into the combustion chamber (that is, the cylinder), or ozone may be added when introducing the intake air into the combustion chamber. Ozone may be added after introducing intake air into the combustion chamber.

  In this internal combustion engine, fuel spray is injected from the center of the combustion chamber toward the outer periphery, and after the start of injection, the fuel is ignited by compression ignition or spark ignition, and the flame flies in the direction from the center to the outer periphery. As the fuel is sprayed, it spreads in the direction from the center to the outer periphery, but as described above, combustion is accelerated by the addition of ozone, so that the combustion ends before the flame reaches the wall surface defining the combustion chamber. . In this way, contact between the flame and the wall surface is avoided. In other words, a gas layer that does not contribute to combustion is formed between the combustion gas at the center of the combustion chamber and the wall surface that defines the combustion chamber. It will be. In other words, this gas layer serves as a heat insulation layer, and suppresses the release of heat from the wall surface, so that the cooling loss can be greatly reduced and the thermal efficiency of the internal combustion engine is increased. In addition, since ozone added to the intake air disappears due to combustion, it is hardly discharged.

  Here, the higher the ozone concentration in the intake air, the shorter the ignition delay time and the shorter the combustion period. Therefore, the control method may further include a step of changing the ozone concentration in the intake air in accordance with the operating state of the internal combustion engine.

  Specifically, the control method may further include a step of increasing the ozone concentration in the intake air when the rotational speed of the internal combustion engine is greater than or equal to a predetermined value than when the rotational speed is less than a predetermined value. .

  When the rotational speed of the internal combustion engine is relatively high, the actual time for the change in the crank angle is shortened. Therefore, by increasing the ozone concentration in the intake air, the combustion is further accelerated, so that the contact between the flame and the wall surface is ensured. It is avoided and it becomes advantageous for reduction of cooling loss.

  Conversely, when the rotational speed of the internal combustion engine is relatively low, if the ozone concentration is increased and the ignition delay time or combustion period is shortened more than necessary, for example, the pressure increase rate becomes too high and combustion noise (that is, , NVH (Noise Vibration Harshness) may deteriorate.

  Therefore, it is preferable to change the ozone concentration in the intake air according to the rotational speed of the internal combustion engine so that the ozone concentration is increased when the rotational speed is high while the ozone concentration is decreased when the rotational speed is low.

  Further, the control method may further include a step of lowering the ozone concentration in the intake air when the load of the internal combustion engine is equal to or greater than a predetermined value than when the load is less than a predetermined value.

  When the load on the internal combustion engine is relatively high, the temperature and pressure in the cylinder are relatively high, and the ignition time and the combustion period tend to be short. Therefore, when the load of the internal combustion engine is high, increasing the ozone concentration in the intake air shortens the ignition delay time and the combustion period more than necessary, so it is preferable to reduce the ozone concentration.

  Conversely, when the load on the internal combustion engine is relatively low, by increasing the ozone concentration, the ignition time and the combustion period are shortened, so that contact between the flame and the wall surface is avoided, thereby reducing the cooling loss and thus thermal efficiency. It becomes advantageous for improvement.

  The control method may further include a step of changing the ozone concentration in the intake air in accordance with the ease of flying of the fuel spray in the combustion chamber (the ease of spreading of the fuel spray).

  Specifically, the control method may further include a step of lowering the ozone concentration in the intake air when the in-cylinder pressure of the internal combustion engine is equal to or greater than a predetermined value than when the in-cylinder pressure is less than a predetermined value. Good.

  When the in-cylinder pressure is high, the fuel spray is difficult to fly and spread, so that contact between the flame and the wall surface is avoided without increasing the ozone concentration in the intake air. On the contrary, when the in-cylinder pressure is low, the fuel spray easily flies and spreads easily. Therefore, by increasing the ozone concentration in the intake air, the combustion is further accelerated and the contact between the flame and the wall surface is surely avoided. It is preferable.

  Further, the control method includes a step of setting a pressure of fuel supplied to a fuel injection valve disposed facing the combustion chamber, and a pressure of the fuel is predetermined when the fuel pressure is equal to or higher than a predetermined value. The method may further include a step of increasing the ozone concentration in the intake air than when it is less than the value.

  The fuel pressure is set in accordance with, for example, the operating state of the internal combustion engine. When the set fuel pressure is high, the fuel spray penetration increases, so that the flame and the wall surface can easily come into contact with each other. When the is low, the penetration of the fuel spray is small, and it is difficult for the flame and the wall surface to come into contact with each other. Therefore, when the fuel pressure is higher than a predetermined value, the ozone concentration in the intake air is relatively increased, so that the contact between the flame and the wall surface can be avoided more reliably. On the other hand, when the fuel pressure is lower than the predetermined value, By relatively lowering the ozone concentration, it is avoided that the ignition delay time and the combustion period are shortened more than necessary.

  An internal combustion engine disclosed herein includes a cylinder block in which a cylinder is formed, a piston fitted into the cylinder, and an engine main body having a combustion chamber defined by a cylinder head placed on the cylinder block. A fuel injection valve for injecting fuel spray in the direction from the center to the outer periphery in the combustion chamber, and ozone addition means for adding ozone to the intake air introduced into the combustion chamber, and by adding ozone to the intake air Combustion is accelerated, and thereby the combustion is terminated before the flame that spreads from the center of the combustion chamber toward the outer periphery along with the flight of the fuel spray reaches the wall surface that defines the combustion chamber. ing.

  According to this configuration, as described above, the addition of ozone to the intake air avoids contact between the flame and the wall surface in the combustion chamber and reduces the cooling loss, so that the thermal efficiency of the internal combustion engine can be increased.

  The ozone adding means may change the ozone concentration in the intake air according to the operating state of the engine body.

  For example, the ozone adding means may be configured to increase the ozone concentration in the intake air when the rotational speed of the engine body is greater than or equal to a predetermined value than when the rotational speed is less than a predetermined value.

  Further, the ozone adding means may be configured to lower the ozone concentration in the intake air when the load of the engine body is equal to or greater than a predetermined value than when the load is less than the predetermined value.

  The ozone addition means may change the ozone concentration in the intake air according to the ease of fuel spray flight (ease of fuel spray spread) in the combustion chamber of the engine body. The means may be configured to lower the ozone concentration in the intake air when the in-cylinder pressure of the internal combustion engine is greater than or equal to a predetermined value, compared to when the in-cylinder pressure is less than a predetermined value.

  Further, when the pressure of the fuel set by the pressure adjusting means for adjusting the pressure of the fuel supplied to the fuel injection valve disposed facing the combustion chamber is equal to or higher than the predetermined level, the pressure of the fuel is lower than the predetermined level. The ozone adding means may be configured to increase the ozone concentration in the intake air.

  The ozone adding means may be configured to ozonize intake air flowing through an intake pipe connected to the cylinder. In other words, the ozone addition means may be configured to ozonize a gas containing oxygen by silent discharge, and such silent discharge type ozone addition means uses ozone (fresh air) flowing through the intake pipe as raw material gas. And ozone can be added to the intake air introduced into the combustion chamber.

  When the ozone adding means is configured by arranging a large number of ozonizers in the intake pipe, the ozone concentration of the intake air can be easily adjusted by changing the number of ozonizers to which the voltage is applied. There is an advantage. In addition, the provision of ozone adding means in the intake pipe is advantageous in increasing the ozone concentration because it is possible to set the voltage application time to the ozonizer long and sufficiently increase the ozone generation time.

  The ozone adding means may be configured to ozonize the intake air introduced into the cylinder.

  In the same manner as described above, for example, the silent discharge type ozone adding means adds ozone to the intake air introduced into the combustion chamber by generating ozone using the intake air (fresh air) introduced into the cylinder as a raw material gas. Is possible. The ozone addition means for converting the intake air introduced into the cylinder into ozone may be provided in a cylinder head that defines the combustion chamber, or may be provided in a fuel injection valve that injects fuel into the combustion chamber.

  As described above, according to the control method for an internal combustion engine and the internal combustion engine described above, by adding ozone to the intake air, fuel spray that flies in the direction from the center to the outer periphery of the combustion chamber, and from the center to the outer periphery. When the flame spreads in the direction of, the combustion is completed before the flame reaches the wall surface of the combustion chamber, so that contact between the flame and the wall surface is avoided and cooling loss is reduced, resulting in an improvement in the thermal efficiency of the internal combustion engine. .

It is a figure which shows the structure of an engine schematically. It is sectional drawing which shows the structure of a fuel injection valve. It is a figure which shows roughly the structure of the intake / exhaust system of an engine. It is sectional drawing which shows schematically the structure of the ozone addition apparatus provided in the intake manifold. It is a figure which shows the structure of the ozonizer which comprises an ozone addition apparatus. It is a figure which illustrates the change of the combustion state by ozone addition. It is explanatory drawing explaining the combustion state in a combustion chamber at the time of adding ozone. It is a figure which shows the relationship between ozone concentration and ignition delay. It is an example of the map which shows the relationship of the ozone concentration with respect to the driving | running state of an engine. It is a figure which shows a fuel consumption when ozone concentration is changed according to the engine load. FIG. 5 is a cross-sectional view schematically showing a configuration of an ozone addition device provided in an intake manifold, which is different from FIG. 4.

  Hereinafter, embodiments of an engine control device will be described with reference to the drawings. The following description of the preferred embodiment is merely exemplary in nature. As shown in FIG. 1, the engine system includes an engine 1, various actuators associated with the engine 1, various sensors, and an engine controller 100 that controls the actuators based on signals from the sensors.

  The engine 1 is a spark ignition type internal combustion engine and has a plurality of cylinders 11. In this example, an in-line four-cylinder engine 1 in which four cylinders 11 are provided in a line as shown in FIG. The engine 1 is mounted on a vehicle such as an automobile, and its output shaft is connected to drive wheels via a transmission, although not shown. The vehicle is propelled by the output of the engine 1 being transmitted to the drive wheels. The engine 1 includes a cylinder block 12 and a cylinder head 13 mounted thereon, and a cylinder 11 is formed inside the cylinder block 12.

  The piston 15 is slidably inserted into each cylinder 11, and defines a combustion chamber 17 together with the cylinder 11 and the cylinder head 13. In this embodiment, the combustion chamber 17 is constituted by a surface in which the lower surface of the cylinder head 13 (the ceiling surface defining the upper surface of the combustion chamber 17) and the crown surface of the piston 15 are perpendicular to the axis of the cylinder 11. ing. A cavity 15a having a relatively small volume is formed in the crown surface of the piston 15 so as to be recessed. As partly shown in FIG. 7, the cavity 15a has a shape like a reentrant type in a diesel engine. In this way, in this engine 1, a high geometric compression ratio is realized by the small cavity 15a and the squish area that is enlarged accordingly, as will be described later.

  Although only one is shown in FIG. 1, two intake ports 18 are formed in the cylinder head 13 for each cylinder 11, and each communicates with the combustion chamber 17 by opening on the lower surface of the cylinder head 13. Similarly, two exhaust ports 19 are formed in the cylinder head 13 for each cylinder 11, and each communicates with the combustion chamber 17 by opening on the lower surface of the cylinder head 13. The intake port 18 is connected to an intake passage through which fresh air introduced into the cylinder 11 flows. As shown in FIG. 3, the intake passage includes an intake manifold 182 having a branch portion and a collecting portion connected to each cylinder 11. Although not shown in FIG. 3, a throttle valve 20 that adjusts the intake air flow rate is provided upstream of the intake passage, and the throttle valve 20 is opened by receiving a control signal from the engine controller 100. The degree is adjusted. On the other hand, the exhaust port 19 is connected to an exhaust passage 191 through which burned gas (exhaust gas) from each cylinder 11 flows (see FIG. 3). Although not shown, an exhaust gas purification system having one or more catalytic converters is disposed in the exhaust passage 191. The catalytic converter includes, for example, a three-way catalyst.

  The intake valve 21 and the exhaust valve 22 are arranged so that the intake port 18 and the exhaust port 19 can be shut off (closed) from the combustion chamber 17, respectively. The intake valve 21 is driven by an intake valve drive mechanism, and the exhaust valve 22 is driven by an exhaust valve drive mechanism. The intake valve 21 and the exhaust valve 22 reciprocate at a predetermined timing to open and close the intake port 18 and the exhaust port 19 to exchange gas in the cylinder 11. Although not shown, the intake valve drive mechanism and the exhaust valve drive mechanism each have an intake camshaft and an exhaust camshaft that are drivingly connected to the crankshaft. These camshafts are synchronized with the rotation of the crankshaft. Rotate. Further, at least the intake valve drive mechanism includes a hydraulic or mechanical phase variable mechanism (Variable Valve Timing: VVT) 23 that can continuously change the phase of the intake camshaft within a predetermined angle range. ing. You may make it provide the lift variable mechanism (CVVL (Continuous Variable Valve Lift)) which can change a valve lift amount continuously with VVT23.

  The spark plug 31 is attached to the cylinder head 13 by a known structure such as a screw. In this embodiment, the spark plug 31 is attached in an inclined state to the exhaust side with respect to the axis of the cylinder 11, and the tip (electrode) faces the ceiling of the combustion chamber 17. The arrangement of the spark plug 31 is not limited to this. The ignition system 32 receives a control signal from the engine controller 100 and energizes the spark plug 31 to generate a spark at a desired ignition timing. As an example, the ignition system 32 may include a plasma generation circuit, and the ignition plug may be a plasma ignition type plug.

  In this embodiment, the fuel injection valve 33 is disposed along the axis of the cylinder 11 and is attached to the cylinder head 13 with a known structure such as using a bracket. The tip of the fuel injection valve 33 faces the center of the ceiling of the combustion chamber 17.

  As shown in FIG. 2, in this embodiment, the fuel injection valve 33 is an outer valve-opening injector having an outer valve 42 that opens and closes a nozzle port 41 that injects fuel into the cylinder 11. However, the fuel injection valve is not limited to an outer valve opening type. The nozzle port 41 is formed in a tapered shape whose diameter increases toward the distal end side at the distal end portion of the fuel pipe 43 extending along the axis of the cylinder 11. The proximal end of the fuel pipe 43 is connected to a case 45 in which a piezo element 44 is disposed. The outer opening valve 42 includes a valve main body 42 a and a connecting portion 42 b that is connected from the valve main body 42 a through the fuel pipe 43 to the piezo element 44. A portion of the valve body 42a on the side of the connecting portion 42b has substantially the same shape as the nozzle port 41, and when the portion is in contact (sitting) with the nozzle port 41, the nozzle port 41 is closed. . At this time, the tip side portion of the valve main body 42 a is in a state of protruding to the outside of the fuel pipe 43.

  The piezo element 44 lifts the outer open valve 42 from a state in which the nozzle port 41 is closed by pressing the outer open valve 42 toward the combustion chamber 17 in the axial direction of the cylinder 11 by deformation due to application of voltage. Then, the nozzle port 41 is opened. At this time, fuel is injected from the nozzle port 41 into the cylinder 11 in a cone shape (specifically, a hollow cone shape) centered on the axis of the cylinder 11. That is, the fuel injection valve 33 injects fuel spray from the center of the combustion chamber 17 toward the outer periphery. In this embodiment, the taper angle of the cone is 90 ° to 100 ° (the taper angle of the inner hollow portion is about 70 °). When the application of voltage to the piezo element 44 is stopped, the piezo element 44 returns to the original state, and the outer opening valve 42 closes the nozzle port 41 again. At this time, the compression coil spring 46 disposed around the connecting portion 42 b in the case 45 facilitates the return of the piezo element 44.

  As the voltage applied to the piezo element 44 increases, the lift amount (hereinafter simply referred to as lift amount) of the outer open valve 42 from the state in which the nozzle port 41 is closed increases. The larger the lift amount, the larger the opening of the nozzle port 41, the greater the penetration of fuel spray injected from the nozzle port 41 into the cylinder 11, and the longer the fuel amount injected per unit time. And the particle size of the fuel spray becomes large.

  The fuel supply system 34 includes an electric circuit for driving the outer opening valve 42 (piezo element 44) and a fuel supply system for supplying fuel to the fuel injection valve 33. The engine controller 100 outputs an injection signal having a voltage corresponding to the lift amount to the electric circuit at a predetermined timing, thereby operating the piezo element 44 and the outer valve 42 via the electric circuit, A desired amount of fuel is injected into the cylinder 11. When the injection signal is not output (when the voltage of the injection signal is 0), the nozzle opening 41 is closed by the outer valve 42. Thus, the operation of the piezo element 44 is controlled by the injection signal from the engine controller 100. Thus, the engine controller 100 controls the operation of the piezo element 44 to control the fuel injection from the nozzle port 41 of the fuel injection valve 33 and the lift amount during the fuel injection.

  Although not shown, the fuel supply system includes a high-pressure fuel pump and a pressure regulating valve. The high-pressure fuel pump pumps the fuel supplied from the fuel tank to the common rail, and the common rail supplies the fuel to a predetermined fuel pressure. Store in. Thus, the fuel stored in the common rail is injected from the nozzle port 41 by the operation of the injector 33 (the outer opening valve 42 is lifted). The high-pressure fuel pump is a plunger type pump and is driven by a rotating member (for example, a camshaft) of an engine.

  The pressure regulating valve is a valve that adjusts a predetermined fuel pressure stored in the common rail. The pressure regulating valve is constituted by, for example, an electromagnetic valve, and the operation is controlled by the engine controller 100. That is, when the engine controller 100 outputs a valve control signal, the pressure regulating valve operates to have an opening degree corresponding to the voltage of the valve control signal. The fuel pressure is determined according to the opening of the pressure regulating valve.

  Here, the fuel of the engine 1 is gasoline in this embodiment, but is not limited thereto, and may be various liquefied fuels containing gasoline, for example.

  The engine controller 100 is a controller based on a well-known microcomputer, and includes a central processing unit (CPU) that executes a program, a memory that is configured by, for example, RAM and ROM, and stores a program and data, And an input / output (I / O) bus for inputting and outputting signals.

As shown in FIGS. 1 and 3, the engine controller 100 includes at least a signal related to the intake air flow rate from the air flow sensor 71 mounted on the downstream side of the air cleaner 183, a crank angle pulse signal from the crank angle sensor 72, and an accelerator pedal. An accelerator opening signal from the accelerator opening sensor 73 for detecting the depression amount of the vehicle, a vehicle speed signal from the vehicle speed sensor 74, and a signal related to the oxygen concentration of the exhaust gas from the O ₂ sensor 75 installed on the exhaust passage 191. Receive each. The engine controller 100 calculates the following control parameters of the engine 1 based on these input signals. For example, a desired throttle opening signal, fuel injection pulse, pressure control valve control signal, ignition signal, valve phase angle signal, and the like. The engine controller 100 outputs these signals to the throttle valve 20 (throttle actuator that moves the throttle valve 20), the fuel supply system 34, the ignition system 32, the VVT 23, and the like.

  The geometric compression ratio ε of the engine 1 is 15 or more and 40 or less. The geometric compression ratio ε is particularly preferably 25 or more and 35 or less. In the present embodiment, the engine 1 is also an engine 1 having a relatively high expansion ratio as well as a high compression ratio because of the configuration where the compression ratio = expansion ratio. In addition, you may employ | adopt the structure (for example, Atkinson cycle and a mirror cycle) used as compression ratio <= expansion ratio.

  As shown in FIG. 1, the combustion chamber 17 includes a wall surface of the cylinder 11, a crown surface of the piston 15, a lower surface (ceiling surface) of the cylinder head 13, and a valve head surface of each of the intake valve 21 and the exhaust valve 22. , Are partitioned. And in order to reduce a cooling loss, the combustion chamber 17 is thermally insulated by providing the heat insulation layers 61, 62, 63, 64, and 65 on each of these surfaces. In addition, below, when these heat insulation layers 61-65 are named generically, a code | symbol "6" may be attached | subjected to a heat insulation layer. The heat insulation layer 6 may be provided on all of these section screens, or may be provided on a part of these section screens. Further, in the illustrated example, the heat insulating layer 61 on the cylinder wall surface is provided at a position above the piston ring 14 in a state where the piston 15 is located at the top dead center. 14 is configured not to slide. However, the heat insulating layer 61 on the cylinder wall surface is not limited to this configuration, and the heat insulating layer 61 may be provided over the entire stroke or a part of the stroke of the piston 15 by extending the heat insulating layer 61 downward. Further, a heat insulating layer may be provided on the port wall surface near the opening on the ceiling surface side of the combustion chamber 17 in the intake port 18 and the exhaust port 19, although it is not the wall surface that directly partitions the combustion chamber 17. In addition, the thickness of each heat insulation layer 61-65 illustrated in FIG. 1 does not show actual thickness, but is only an illustration, and does not show the magnitude relationship of the thickness of the heat insulation layer in each surface.

  The heat insulation structure of the combustion chamber 17 will be described in more detail. As described above, the heat insulating structure of the combustion chamber 17 is constituted by the heat insulating layers 61 to 65 provided on the respective screens that define the combustion chamber 17, and these heat insulating layers 61 to 65 are the combustion gas in the combustion chamber 17. Therefore, the heat conductivity is set to be lower than that of the metal base material constituting the combustion chamber 17. Here, for the heat insulating layer 61 provided on the wall surface of the cylinder 11, the cylinder block 12 is the base material, and for the heat insulating layer 62 provided on the crown surface of the piston 15, the piston 15 is the base material. For the heat insulating layer 63 provided on the ceiling surface, the cylinder head 13 is a base material, and for the heat insulating layers 64 and 65 provided on the valve head surfaces of the intake valve 21 and the exhaust valve 22, respectively, the intake valve 21 and the exhaust valve 22 are provided. Are the base materials. Accordingly, the base material is aluminum alloy or cast iron for the cylinder block 12, cylinder head 13 and piston 15, and heat-resistant steel or cast iron for the intake valve 21 and exhaust valve 22.

  In addition, the heat insulating layer 6 preferably has a volumetric specific heat smaller than that of the base material in order to reduce cooling loss. That is, the gas temperature in the combustion chamber 17 varies with the progress of the combustion cycle, but in a conventional engine that does not have the heat insulation structure of the combustion chamber 17, the cooling water flows in a water jacket formed in the cylinder head or cylinder block. Thus, the temperature of the surface defining the combustion chamber 17 is maintained substantially constant regardless of the progress of the combustion cycle.

  On the other hand, since the cooling loss is determined by cooling loss = heat transfer coefficient × heat transfer area × (gas temperature−temperature of the section screen), the cooling temperature increases as the temperature difference between the gas temperature and the wall surface temperature increases. The loss will increase. In order to suppress the cooling loss, it is desirable to reduce the difference between the gas temperature and the temperature of the section screen. However, when the temperature of the section screen of the combustion chamber 17 is maintained substantially constant by cooling water, It is unavoidable that the temperature difference increases with fluctuation. Therefore, it is preferable to reduce the heat capacity of the heat insulating layer 6 so that the temperature of the section screen of the combustion chamber 17 changes following the fluctuation of the gas temperature in the combustion chamber 17.

The heat insulation layer 6 may be formed, for example, by coating a ceramic material such as ZrO ₂ on the base material by plasma spraying. The ceramic material may contain a number of pores. If it does in this way, the thermal conductivity and volume specific heat of the heat insulation layer 6 can be made lower.

  Further, in the present embodiment, as shown in FIG. 1, a port liner 181 made of aluminum titanate having an extremely low thermal conductivity, excellent heat insulation, and excellent heat resistance is integrated with the cylinder head 13. A heat insulating layer is provided in the intake port 18 by casting. With this configuration, when fresh air passes through the intake port 18, it is possible to suppress or avoid an increase in temperature due to heat received from the cylinder head 13. As a result, the temperature of the fresh air introduced into the cylinder 11 (initial gas temperature) is lowered, so that the gas temperature at the time of combustion is lowered and the temperature difference between the gas temperature and the section screen of the combustion chamber 17 is reduced. Become advantageous. Lowering the gas temperature at the time of combustion can lower the heat transfer rate, which is advantageous for reducing the cooling loss. In addition, the structure of the heat insulation layer provided in the intake port 18 is not limited to the casting of the port liner 181.

  In this engine 1, in addition to the heat insulation structure of the combustion chamber 17 and the intake port 18 in at least a part of the operation region, a heat insulation layer is formed by a gas layer in the combustion chamber 17 to greatly reduce the cooling loss. To reduce it.

  Specifically, the engine controller 100 expands from the latter stage of the compression stroke so that a gas layer containing fresh air is formed at the outer peripheral portion in the combustion chamber 17 of the engine 1 and an air-fuel mixture layer is formed at the center. A control signal is output to the fuel supply system 34 in order to inject fuel into the cylinder from the nozzle port 41 of the fuel injection valve 33 within the period from the beginning of the stroke. That is, fuel is injected into the cylinder by the fuel injection valve 33 during the period from the latter half of the compression stroke to the early stage of the expansion stroke, and the fuel spray does not reach the outer peripheral portion (gas layer) in the cylinder. By limiting to a large size (length), stratification is realized in which an air-fuel mixture layer is formed in the center of the cylinder and a gas layer containing fresh air is formed around the mixture layer. This gas layer may be only fresh air, and may contain burned gas (EGR gas) in addition to fresh air. It should be noted that there is no problem even if a small amount of fuel is mixed in the gas layer, and the fuel layer may be leaner than the gas mixture layer so that the gas layer can serve as a heat insulating layer.

  Thus, if the gas mixture and the gas mixture layer are formed in the combustion chamber 17 and the gas mixture in the gas mixture layer is combusted by, for example, compression self-ignition, as shown in FIG. Due to the gas layer G between the gas layer and the wall surface of the cylinder 11 or the like, the high-temperature combustion gas does not come into contact with the wall surface of the cylinder 11 or the like. The release of heat can be suppressed. As a result, the cooling loss can be greatly reduced.

  It should be noted that if the cooling loss is simply reduced, the reduced cooling loss is converted into exhaust loss and does not contribute much to the improvement in the illustrated thermal efficiency. The energy of the combustion gas corresponding to the reduced cooling loss is efficiently converted into mechanical work. That is, it can be said that the illustrated thermal efficiency is greatly improved in the engine 1 by adopting a configuration that reduces both the cooling loss and the exhaust loss.

  As described above, in the engine 1, the gas layer G is formed in the combustion chamber 17 to reduce the cooling loss. However, the gas layer G cannot be reliably formed depending on the operating state of the engine 1. In addition, the cooling loss reduction effect may not be obtained.

  That is, in the engine 1, as described above, fuel is injected from the central portion of the combustion chamber 17 toward the outer peripheral portion, and the combustion flame caused by self-ignition is accompanied by fuel spray flying in the direction from the central portion to the outer peripheral portion. It spreads from the center to the outer periphery. At this time, if the ignition delay time until the air-fuel mixture ignites after the fuel injection becomes longer, or if the combustion period from the start of combustion to the end of combustion becomes longer, the flame is applied to the wall surface defining the combustion chamber 17. Combustion does not end before it reaches, and the flame reaches the wall surface.

  For example, when the load on the engine 1 is low, the temperature and pressure in the combustion chamber 17 become low, so the combustion slows down, and the flame easily reaches the wall surface that defines the combustion chamber 17 as described above. In addition, when the engine 1 has a high rotational speed, the actual time with respect to the change in the crank angle is shortened, so that the combustion is relatively slow. In this case as well, the flame easily reaches the wall surface that defines the combustion chamber 17.

  Therefore, the engine 1 includes an ozone addition device 5 that adds ozone to the intake air in order to accelerate combustion as necessary. Specifically, as shown in FIG. 3, the ozone addition device 5 is disposed in a collecting portion in the intake manifold 182, and is controlled by the engine controller 100 to ozonize the intake air passing there. To do.

  As shown in FIGS. 4 and 5, the ozone adding device 5 is constituted by a plurality of ozonizers 50 arranged in parallel in the vertical and horizontal directions on the transverse cross section in the intake pipe (intake manifold). Each ozonizer 50 is configured to generate ozone by silent discharge using an intake air containing oxygen as a source gas. The ozonizer 50 is a coaxial cylindrical type including a ground electrode tube 51 and a high voltage electrode 52 coaxially disposed with a predetermined discharge gap with respect to the ground electrode tube 51. The dielectric 53 is coated. Then, by applying a high-frequency AC high voltage to the high-voltage electrode 52 from a power source (not shown) via the electric wire 54, silent discharge occurs in the discharge gap, and air passing therethrough (that is, intake air) Is ozonized. The intake air to which ozone is added in this way is introduced into each cylinder 11 via the branch portion of the intake manifold 182.

  The ozone concentration in the intake air after passing through the ozone adding device 5 can be adjusted by changing the application mode of the voltage to each ozonizer 50 and / or changing the number of ozonizers 50 to which the voltage is applied. The engine controller 100 is configured to adjust the ozone concentration in the intake air through the control of the ozone addition device 5 as will be described in detail later.

  By adding ozone to the intake air, combustion in the combustion chamber 17 can be accelerated by the strong oxidizing action of ozone. For example, FIG. 6 shows the heat generation rate when ozone is not added to the intake air (see the dashed line in the figure), and the heat generation rate when ozone is added to the intake air (see the solid line in the figure). It is a figure to compare. The fuel injection timing is the same. According to this, it can be seen that when ozone is added to the intake air, the timing at which the heat generation rate rises is advanced, and the start of ignition is accelerated compared to the case where ozone is not added. . This corresponds to a reduction in the ignition delay, which is the time from the end of fuel injection to the ignition. In addition, when ozone is added to the intake air, the rise of the heat generation rate becomes steeper, and the peak of the heat generation rate moves toward the advance side. Thus, the end timing of combustion is also advanced when ozone is added to the intake air, compared to the case where ozone is not added, and the combustion period from the start of combustion to the end of combustion is also shortened. .

  Thus, the flame that spreads from the central portion toward the outer peripheral portion is combusted together with the fuel spray flying from the central portion in the combustion chamber 17 toward the outer peripheral portion by reducing the ignition delay and the combustion period. Before reaching the wall surface defining the chamber 17, the combustion ends. That is, as shown in FIG. 7, a gas layer G that does not contribute to combustion is reliably formed on the outer peripheral portion in the combustion chamber 17. In particular, ending the combustion before the flame reaches the squish area is effective in reducing the cooling loss in order to avoid the release of heat to the cylinder head 13.

  Here, the ozone concentration in the intake air is related to the speed of combustion, and as shown in FIG. 8, the ignition delay time becomes shorter as the ozone concentration in the intake air becomes higher, and the ignition delay time becomes shorter as the ozone concentration becomes lower. Becomes longer. Below the predetermined concentration indicated by the alternate long and short dash line, the ignition delay can be shortened to about 4 ms by setting the ozone concentration to at least 10 ppm under conditions that cause misfire. On the other hand, if the ozone concentration is 100 ppm or more, the ignition delay becomes too short, and the pressure increase rate (dP / dθ) in the cylinder becomes too high. The ignition delay is preferably set to 1 to 4 ms, and in order to achieve this, it is desirable to set the ozone concentration of the intake air in the range of 10 to 100 ppm.

  As described above, the state in the cylinder 11 changes according to the operating state of the engine 1 according to the load and the rotational speed of the engine 1, and the flame easily reaches the wall surface that defines the combustion chamber 17. It becomes difficult to reach. Therefore, the engine 1 is configured to change the ozone concentration in the intake air according to the operating state. FIG. 9 is a map showing the relationship of the ozone concentration with respect to the operating state of the engine 1.

  In this map, when the load of the engine 1 is low, the in-cylinder temperature and pressure are low at the same rotation speed, which is disadvantageous for the ignitability of the fuel and the combustion speed is slow. Is set high and combustion is accelerated as described above. On the other hand, if the load on the engine 1 is increased, the in-cylinder temperature and pressure are increased, which is advantageous for the ignitability of the fuel and the combustion speed is increased, so the ozone concentration in the intake air is set low. That is, as described above, if the ozone concentration is too high, the rate of increase in pressure in the cylinder 11 becomes too high and the NVH performance deteriorates.

  Also, at the same load, when the rotational speed of the engine 1 is low, the actual time for changing the crank angle becomes longer, so the necessity of accelerating combustion is not so high, while the ozone concentration in the intake air is set low, If the rotational speed of the engine 1 is increased, the actual time for changing the crank angle is shortened, so that the ozone concentration is set high in order to accelerate combustion.

  The engine controller 100 sets the ozone concentration according to the map of FIG. 9 based on the operating state of the engine 1 obtained from the detected values of various parameters, and controls the ozone adding device 5 accordingly, thereby the ozone in the intake air. The density is controlled to be a set value.

  Here, FIG. 10 shows the relationship between the engine load and the fuel consumption when the ozone concentration in the intake air is changed at a predetermined engine speed. According to this, when the ozone concentration in the intake air is constant, the low load side is limited by the misfire limit, and the high load side is limited by the NVH limit. However, as shown in the map of FIG. The high region reduces the ozone concentration in the intake air, the medium engine load region makes the ozone concentration in the intake air medium, and the low engine load region increases the ozone concentration in the intake air, It can be seen that the fuel consumption can be made substantially flat with respect to a wide load region of the engine 1 (see the one-dot chain line in FIG. 10).

Here, the control for setting the ozone concentration in the intake air based on the operating state including the rotation speed and load of the engine 1 is exemplified, but the control of the ozone adding device 5 is not limited to this. For example, as the fuel injection amount injected into the cylinder 11 increases, the fuel spray time becomes longer, and the flame easily reaches the wall surface of the combustion chamber 17. Therefore, the injection amount increases according to the fuel injection amount. If so, the ozone concentration in the intake air may be increased. Specifically, as shown in FIG. 3, the engine controller 100 sets the fuel injection amount based on the air flow rate detected by the airflow sensor 71 and the engine speed detected by the crank angle sensor 72, and O _The set fuel injection amount is corrected according to the oxygen concentration detected by the _two sensors 75. Then, based on the corrected fuel injection amount, for example, the ozone concentration is set according to a preset relational expression so that the ozone concentration in the intake air increases when the injection amount increases, You may control. The fact that combustion is accelerated by the addition of ozone, for example, can be grasped from the detected value of the crank angle sensor 72 on the basis of the fluctuation of the angular velocity. Control of the ozone addition device 5 (in other words, adjustment of the amount of ozone added to the intake air) may be performed.

  Further, for example, if the in-cylinder pressure becomes high, the fuel spray becomes difficult to fly and the flame hardly reaches the wall surface of the combustion chamber 17, while if the in-cylinder pressure becomes low, the fuel spray becomes easy to fly. Since the flame easily reaches the wall surface of the combustion chamber 17, when the in-cylinder pressure decreases according to the in-cylinder pressure, the ozone concentration in the intake air is increased. When it is high, the ozone concentration in the intake air may be low. This also suppresses the flame from reaching the wall surface that defines the combustion chamber 17 and makes it possible to reliably reduce the cooling loss.

  Further, if the fuel pressure is increased, the fuel spray is likely to fly and the flame is likely to reach the wall surface of the combustion chamber 17, while if the fuel pressure is reduced, the fuel spray is difficult to fly and the flame is reduced. Since it becomes difficult to reach the wall surface of the combustion chamber 17, the ozone concentration in the intake air is made low when the fuel pressure becomes low according to the fuel pressure, and conversely, when the fuel pressure becomes high, The ozone concentration may be increased. This also suppresses the flame from reaching the wall surface that defines the combustion chamber 17 and makes it possible to reliably reduce the cooling loss.

  Note that, as described above, the ozone concentration adjustment control using the control map shown in FIG. 9, the ozone concentration adjustment control based on the fuel injection amount, the ozone concentration adjustment control based on the in-cylinder pressure, and the fuel pressure. The adjustment control of the ozone concentration can be combined as appropriate.

  Further, in the above configuration, the ozone adding device 5 is configured by the coaxial cylindrical ozonizer 50, but may be configured by a parallel plate type ozonizer 500 as shown in FIG. In the parallel plate type ozonizer 500, a ground electrode 510 disposed so as to cross the inside of the intake pipe and a high voltage electrode 520 provided with a dielectric 530 on the surface are disposed with a predetermined discharge gap therebetween. In the illustrated example, a plurality of ozonizers 500 are arranged so as to overlap in the vertical direction. Even in the ozone adding device 5 having such a configuration, it is possible to add ozone to the intake air. Such a parallel plate type ozonizer 500 has an advantage that a large discharge area can be secured.

  Further, in the intake pipe (intake manifold 182), ozone may be added to the intake air introduced into the cylinder 11 instead of adding ozone to the intake air. 13, an ozone addition device may be attached in the vicinity of the fuel injection valve 33. In this case, it is desirable to apply a voltage to the ozonizer during the intake stroke and to add ozone to the intake air using the intake flow. The ozone concentration can be changed by adjusting the driving time of the ozonizer. An ozonizer may be provided in the fuel injection valve 33.

  Further, the technology disclosed herein is not limited to the application to the high compression ratio engine 1 having the heat insulation structure of the combustion chamber 17 as described above. For example, the heat insulation structure of the combustion chamber 17 is omitted. Also good.

1 engine (internal combustion engine)
11 Cylinder 12 Cylinder block 13 Cylinder head 15 Piston 17 Combustion chamber 100 Engine controller 182 Intake manifold (intake pipe)
33 Fuel injection valve 5 Ozone addition device (ozone addition means)
50 Ozonizer 500 Ozonizer

Claims (8)

Injecting fuel spray from the center of the combustion chamber toward the outer periphery in the combustion chamber of the internal combustion engine;
Adding ozone to the intake air introduced into the combustion chamber; and
Before the combustion in the combustion chamber is accelerated by the addition of ozone to the intake air, the flame spreading from the center of the combustion chamber toward the outer periphery along with the flight of the fuel spray reaches the wall surface that defines the combustion chamber. And a method for controlling the internal combustion engine, including the step of terminating the combustion. A control method for an internal combustion engine according to claim 1,
A control method for an internal combustion engine, further comprising a step of increasing an ozone concentration in the intake air when the rotational speed of the internal combustion engine is equal to or higher than a predetermined value than when the rotational speed is less than a predetermined value. An internal combustion engine control method according to claim 1 or 2,
A control method for an internal combustion engine, further comprising a step of lowering an ozone concentration in the intake air when the load of the internal combustion engine is equal to or greater than a predetermined value than when the load is less than a predetermined value. A control method for an internal combustion engine according to claim 1,
A control method for an internal combustion engine, further comprising a step of lowering an ozone concentration in the intake air when the in-cylinder pressure of the internal combustion engine is equal to or greater than a predetermined value, compared to when the in-cylinder pressure is less than a predetermined value. A control method for an internal combustion engine according to claim 1,
A control method for an internal combustion engine, further comprising a step of increasing an ozone concentration in the intake air when the pressure of the fuel is equal to or higher than a predetermined level than when the pressure of the fuel is lower than a predetermined level. An engine body having a cylinder block in which a cylinder is formed, a piston fitted into the cylinder, and a combustion chamber defined by a cylinder head placed on the cylinder block;
A fuel injection valve that injects fuel spray from the center to the outer periphery in the combustion chamber;
Ozone adding means for adding ozone to the intake air introduced into the combustion chamber,
Combustion is accelerated by the addition of ozone to the intake air, so that the flame that spreads in the direction from the center to the outer periphery of the combustion chamber along with the flight of the fuel spray reaches the wall before partitioning the combustion chamber. An internal combustion engine configured to terminate the engine. The internal combustion engine according to claim 6,
The internal combustion engine, wherein the ozone adding means is configured to ozonize intake air flowing through an intake pipe connected to the cylinder. The internal combustion engine according to claim 6,
The ozone adding means is an internal combustion engine configured to ozonize intake air introduced into the cylinder.

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