JP5956784B2 - Internal combustion engine - Google Patents

Description

  The present invention relates to an internal combustion engine. In particular, the present invention relates to the structure of a combustion chamber of an internal combustion engine that directly injects fuel into the combustion chamber.

  Up to now, for example, in a direct injection type diesel engine (a diesel engine in which fuel is directly injected into a combustion chamber and burned), not only the penetration of fuel spray (penetration) is increased, but also swirl (swirl flow) and squish Air flow such as (longitudinal flow) has been used to control the spatial distribution of the mixture of fuel and air in the combustion chamber to improve the air utilization rate and to improve combustion.

  More specifically, in the conventional re-entrant combustion chamber (see FIG. 7) in a diesel combustion engine, the fuel injection pressure is increased to increase atomization and penetration of the fuel spray, and the swirl applies the fuel spray to the fuel spray. Air introduction was promoted, and the air-fuel ratio was improved by squishing the air-fuel mixture outside the combustion chamber. However, since the strength of the airflow changes depending on the operating conditions such as the engine speed and load, the spray colliding with the combustion chamber wall surface stays, soot generation and heat loss increase.

  Here, for example, in Patent Document 1, as shown in FIG. 8, the top surface of the piston 9 includes a cavity 10 that is recessed so as to form most of the combustion chamber, and a cylinder ceiling portion is formed on the inner peripheral surface of the cavity 10. In relation to the combustion chamber structure of a direct injection type diesel engine in which fuel is injected radially from the center of the cylinder and self-ignited, a peripheral portion of the opening of the cavity 10 is recessed by a required depth with respect to the top surface of the piston 9 to form a step ( The outer peripheral portion of the bottom surface of the turned portion 24 rises so as to draw a gently curved surface as it goes outward in the radial direction, reaches the top surface of the piston 9 and is within the bottom surface of the turned portion 24. There is a combustion chamber (two-stage lip structure) configured such that the inlet lip portion 11 is formed at a position one step down from the top surface of the piston 9 by the peripheral portion and the combustion chamber wall surface portion 12 rising from the bottom surface of the cavity 10. Piston is described.

JP 2007-21644 A

  According to the piston provided with the combustion chamber described in Patent Document 1, mixing of fuel spray and air is improved in the combustion chamber, and better combustion can be performed. Can be improved.

  In this way, when considering the improvement of combustion in a diesel engine, the formation of a mixture of fuel spray and air in the cylinder (cylinder air) is important, but when considering the efficient introduction of air into the fuel spray In particular, it is one of the future issues to promote the mixing of fuel sprays that have almost no momentum (kinetic energy) after the fuel injection from the fuel injection valve is completed.

  However, even with a piston provided with a combustion chamber described in Patent Document 1, mixing acceleration in fuel spray having a relatively large momentum (kinetic energy) during injection from the fuel injection valve can be expected, but fuel injection It is not possible to promote the mixing of fuel sprays that have little momentum after the end of.

  As an example of the prior art for promoting the mixing of fuel spray at the end of such fuel injection, there is multistage fuel injection called after injection (multistage fuel injection in which fuel injection is performed after main injection). The method is to inject fuel multiple times from the same fuel injection valve. For the fuel spray after the second half of the after injection and after the after injection, the fuel spray with little momentum is promoted as described above. The problem that it cannot be achieved and mixing deteriorates remains. For this reason, it is difficult to shorten the combustion period, and the effect of improving the thermal efficiency cannot be expected.

  There are few techniques that focus on improving the fuel / air mixture formation in the latter half of the fuel injection period (late injection) and after the end of the fuel injection. Of the total black smoke generated in the combustion process, the fuel The fact is that no effective solution has been found so far, although it has been found that the proportion of fuel produced from late injected fuel is high after the end of injection.

  The present invention has been made in view of such circumstances, and has a relatively simple and low-cost configuration, and causes a disturbance by strong air flow in the combustion chamber according to the operating state of the internal combustion engine, thereby mixing fuel and air. It is an object of the present invention to provide an internal combustion engine that can promote the reduction of the combustion period and thus the improvement of fuel consumption and the reduction of the amount of black smoke (soot) emission.

Therefore, the internal combustion engine according to the present invention is
An internal combustion engine comprising a combustion chamber surrounded by a piston top surface of the internal combustion engine, a cylinder head lower surface, and an inner wall of a cylinder in which the piston is slidably accommodated,
A fuel injection nozzle that is attached to the cylinder head and injects fuel from the lower surface of the cylinder head to the combustion chamber,
An air chamber provided on the outer periphery of the fuel injection nozzle;
A communication portion that communicates the air chamber and the combustion chamber;
And comprising
The other air chamber is connected to the air chamber, and the volume of the other air chamber is configured to be variable.

In the present invention, the volume of the other air chamber may be variably configured according to the operating state of the internal combustion engine.

In the present invention, when the load of the internal combustion engine is high, the volume of the other air chamber is controlled to be large. When the load of the internal combustion engine is low, the volume of the other air chamber is small. It is characterized by being controlled to become.

  According to the present invention, although it is a relatively simple and low-cost configuration, it is possible to promote the mixing of fuel and air by causing disturbance in the combustion chamber with a strong air flow according to the operating state of the internal combustion engine. Thus, it is possible to provide an internal combustion engine that can shorten the combustion period, promote fuel consumption improvement, and reduce the emission of black smoke (soot).

1 is a cross-sectional view (a cross-sectional view cut along a plane substantially orthogonal to a crankshaft) in the vicinity of a combustion chamber of an internal combustion engine according to an embodiment of the present invention. It is sectional drawing (enlarged cross section of the A section vicinity of FIG. 1) which expanded and showed the air chamber vicinity of the internal combustion engine which concerns on embodiment same as the above. It is the figure which looked at the air chamber vicinity of the internal combustion engine which concerns on embodiment same as the above from the B direction of FIG. It is the perspective view which extracted an example of the air chamber of the internal combustion engine which concerns on embodiment same as the above, and a communication part vicinity, and was seen from diagonally upward. It is sectional drawing which expanded and showed the air chamber of the internal combustion engine which concerns on embodiment same as the above, a communication part, and the variable capacity | capacitance type air chamber vicinity (state where the volume of a variable capacity type air chamber is large). It is sectional drawing which expanded and showed the air chamber of the internal combustion engine which concerns on embodiment same as the above, a communication part, and the variable capacity | capacitance type air chamber vicinity (state where the volume of a variable capacity type air chamber is small). It is sectional drawing which shows an example of the combustion chamber (reentrant type) of the conventional internal combustion engine. It is sectional drawing which shows an example of the combustion chamber (two-stage lip structure) of the conventional internal combustion engine.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment of the invention will be described with reference to the accompanying drawings. The present invention is not limited to the embodiments described below.

  As shown in FIG. 1, an internal combustion engine 100 according to an embodiment of the present invention includes a lower surface of a cylinder head 110, a top surface (upper surface) of a piston 120, and a cylinder liner 140 fitted into a cylinder block 130. A fuel injector 160 is attached to the cylinder head 110 so that the fuel injection nozzle 161 at the tip thereof faces the combustion chamber 150 defined by the peripheral wall surface.

  The fuel injector 160 is provided in the cylinder head 110 for each cylinder, and the fuel injection nozzle 161 at the tip of the fuel injector 160 is disposed so as to be substantially at the center of the combustion chamber 150 when viewed from the reciprocating direction of the piston 120. .

  At the tip of the fuel injection nozzle 161 facing the combustion chamber 150, for example, a plurality of 6 to 10 injection holes are provided at predetermined intervals in the circumferential direction, and the top surface of the piston 120 is recessed from the plurality of injection holes. To the provided piston combustion chamber (cavity) 121, fuel is injected and supplied at a predetermined timing with a fuel injection amount set according to the operating state (rotational speed, load, etc.) of the internal combustion engine 100. (See FIG. 2).

  Reference numeral 170 denotes an intake valve, reference numeral 171 denotes an intake port, reference numeral 180 denotes an exhaust valve, and reference numeral 181 denotes an exhaust port.

  Here, in general, in a diesel engine, as the piston approaches compression top dead center, the air sucked into the combustion chamber becomes high temperature and high pressure, and combustion is performed by self-ignition by injecting high pressure fuel into the atmosphere. Then, diffusion combustion is performed while forming a mixture of fuel and air with kinetic energy or the like of the fuel spray.

  Recent research has gradually elucidated the structure of the fuel spray, and the fuel spray takes air into the fuel spray by exchanging momentum with the surrounding air, and when combustion starts, the air intake is mainly the uppermost flame of the fuel spray. Occurs in the part that is not covered by the fuel (relatively immediately after the injection from the fuel injection nozzle), the momentum of the fuel spray decreases rapidly with the end of the fuel injection, and the mixture of fuel and air remains slow and the It has been understood that a lot of soot is generated by interfering with the fuel gas.

  If mixing with the air of the fuel spray used for combustion after the end of fuel injection can be promoted in a state where the amount of momentum is injected in the latter part of such a fuel injection period, combustion in the latter part of the combustion period (late stage) (Combustion) can be activated, which can be expected to contribute to improving fuel efficiency and greatly reducing black smoke (soot).

  For this reason, in the present embodiment, as shown in FIGS. 1 to 4, an air chamber 200 capable of accommodating a predetermined amount of air is provided around the fuel injection nozzle 161 of the fuel injector 160.

  The air chamber 200 is provided in a cylindrical shape around the fuel injection nozzle 161 of the fuel injector 160. The air chamber 200 is hermetically sealed from the main body side of the fuel injector 160, while the fuel injection nozzle 161 is sealed. A communication portion (throttle portion) 210 having a predetermined gap with the periphery of the combustion chamber 150 is configured to communicate with the combustion chamber 150.

  As shown in FIGS. 3 and 4, the communication portion (throttle portion) 210 is provided in an annular shape between the outer periphery of the fuel injector 160 near the tip of the fuel injection nozzle 161 and the cylinder head 110. .

  According to the internal combustion engine 100 according to the present embodiment including the air chamber 200 and the communication portion (throttle portion) 210 as described above, the piston 120 that reciprocates linearly moves into the combustion chamber 150 as it approaches the compression top dead center. The sucked air is compressed, and a part of the sucked air is guided to the air chamber 200 through the communication part (throttle part) 210.

  On the other hand, as the piston 120 approaches the compression top dead center, the air sucked into the combustion chamber 150 becomes high temperature and high pressure, and high pressure fuel is injected into the atmosphere from the fuel injection nozzle 161 of the fuel injector 160, thereby Combustion is started by ignition.

  Then, after the combustion is started, the piston 120 starts to descend (shifts to the expansion stroke), and when the pressure in the combustion chamber 150 rapidly decreases, until now, via the communication portion (throttle portion) 210. The air that has been introduced and stored in the air chamber 200 passes through a relatively narrow communication portion (throttle portion) 210 with the periphery of the fuel injection nozzle 161 for a moment, but becomes an air jet 300 in the combustion chamber 150. It flows in like a blow back.

  The blow-back timing (supply timing) of the air stored in the air chamber 200 (fresh air that has not been used for combustion) to the combustion chamber 150 is almost fuel at the time of high load with a lot of black smoke (soot) generation. Since it corresponds to immediately after the end of injection, high disturbance and fresh air (air) can be effectively supplied to the fuel spray at the time when the air-fuel mixture formation is most difficult (late combustion).

  That is, according to the present embodiment, combustion in the later stage of the combustion period (late stage combustion) can be activated, which can contribute to improvement in fuel consumption and significant reduction in black smoke (soot).

  Thus, in the present embodiment, only the combustion chamber 150 constituted by the piston combustion chamber 121 recessed in the top surface of the piston 120 and the gap between the top surface of the piston 120 and the lower surface of the cylinder head 110 is provided. In addition, the air chamber 200 is also provided on the cylinder head 110 side, and the air chamber 200 is communicated with the combustion 150 via the communication portion (throttle portion) 210 provided in the vicinity of the fuel injection nozzle 161. The relative collision position between the fuel spray immediately after being injected from the fuel injection nozzle 161 and the air jet 300 ejected from the air chamber 200 via the communication portion (throttle portion) 210 is determined as the operating state of the internal combustion engine 100. Regardless of (rotation speed, load, etc.), it can be made almost constant, so that a mixture of robust fuel and air that is not easily affected by external disturbances and combustion can be realized. Can.

  Further, in the internal combustion engine 100 according to the present embodiment, particularly in high load operation with a large amount of fuel injection, at the same time as the piston lowering acceleration that becomes a problem in the later combustion (late combustion or afterburning) of the combustion period increases. The air jet 300 ejected from the air chamber 200 through the communication part (constriction part) 210 introduces fresh air and disturbs the vicinity of the center of the combustion chamber 150 in FIG. 2 (fuel spray that hardly captures ambient air). Therefore, it is possible to effectively improve the combustion in the later stage of the combustion period (late combustion or afterburning), so that the combustion period can be shortened, and the fuel consumption can be improved and the black smoke (soot) can be reduced. This can contribute to significant reduction.

  As described above, according to the present embodiment, although it is a relatively simple and low-cost configuration, it disturbs with strong air flow in the combustion chamber to promote mixing of fuel and air, and shortens the combustion period. Can improve the fuel consumption and provide an internal combustion engine that can reduce the emission of black smoke.

  Here, in order to obtain an effective air jet 300, a certain amount of volume is required as an air chamber, but the compression ratio is reduced by the volume.

  When the load is high, the reduction in the compression ratio extends the ignition delay period and secures the premixing period. Therefore, the premixed gas formation is promoted to suppress the generation of soot and the maximum combustion pressure in the cylinder Although there is an advantage that the friction loss between the piston and the liner or at the bearing can be reduced, the decrease in the cylinder temperature accompanying the decrease in the compression ratio causes the combustion to slow down and the thermal efficiency to deteriorate. There is a risk of inviting.

  Therefore, it is effective if the volume of the air chamber is relatively large when the load is high, and the volume of the air chamber can be minimized when the load is low.

  Therefore, in the present embodiment, as shown in FIG. 5, the variable capacity air chamber 250 is connected to the air chamber 200 via the air passage 251. The air chamber 200 corresponds to an example of another air chamber according to the present invention.

  The variable capacity air chamber 250 has a space 252 connected to the air passage 251, and this space 252 has a cylinder (for example, a cylindrical space) inner wall 253 and a slidable and airtight property to the cylinder inner wall 253. The piston 254 is inserted and held.

  The piston 254 includes a piston rod 255 that extends into the hydraulic chamber 256 on the back side of the space 252. The piston rod 255 is slidably supported by a piston rod sleeve or the like, and an elastic member (for example, a coil spring) 257 is inserted through the outer periphery of the piston rod 255.

  The elastic member 257 is attached so as to apply a restoring force (elastic force) in a direction that draws the piston 254 from the space 252 side to the hydraulic chamber 256 side. The elastic member 257 can also be configured by a leaf spring or the like.

  The hydraulic chamber 256 is configured to be supplied with oil of a predetermined pressure through a hydraulic pressure supply passage 258, and the hydraulic pressure in the hydraulic chamber 256 is electromagnetically interposed in the hydraulic relief passage 259. By opening and closing a relief valve (not shown), the hydraulic pressure maintaining state and the hydraulic pressure releasing state can be switched. Here, as the oil supplied to the hydraulic chamber 256, for example, lubricating oil (engine oil) of the internal combustion engine 100 can be used.

  In the present embodiment including the variable capacity air chamber 250 having such a configuration, when the internal combustion engine 100 is under a low load, an electromagnetic relief valve (not shown) interposed in the hydraulic pressure relief passage 259 is closed. As a result, the hydraulic pressure supplied through the hydraulic pressure supply passage 258 can be maintained in the hydraulic chamber 256, and the hydraulic pressure in the hydraulic chamber 256 is increased, so that the piston 254 is elasticized by the elastic member 257. The space 252 is made smaller by moving the space 252 against the force (restoring force) (see FIG. 6).

  Thus, in the present embodiment, when the internal combustion engine 100 is under a low load, the volume of the space 252 of the variable capacity air chamber 250 can be reduced, so that the sum of the space 252 and the air chamber 200 (the air chamber) 200 and the total volume of the space connected to it), the compression ratio can be kept high to suppress a decrease in combustion speed (slowing of combustion), and a reduction in thermal efficiency and fuel consumption can be achieved. Can be suppressed.

  On the other hand, in the present embodiment, when the internal combustion engine 100 is under a high load, the hydraulic pressure supply passage 258 is opened by opening an electromagnetic relief valve (not shown) interposed in the hydraulic pressure relief passage 259. The hydraulic pressure supplied via the hydraulic chamber 256 can be released from the hydraulic chamber 256 and the hydraulic pressure in the hydraulic chamber 256 is kept low, so that the piston 254 is moved toward the hydraulic chamber 256 by the restoring force (elastic force) of the elastic member 257. The space 252 is enlarged by moving (see FIG. 5).

  Thus, in the present embodiment, when the internal combustion engine 100 is under a high load, the volume of the space 252 of the variable capacity air chamber 250 can be increased, so that the sum of the space 252 and the air chamber 200 (air chamber) 200 and the sum of the spatial volumes connected thereto), the compression ratio can be kept low, the combustion maximum pressure can be kept low, and the compression end temperature (combustion chamber temperature at the compression top dead center) can be reduced. It is possible to promote the premixed combustion by the reduction.

  In the present embodiment, the case where the volume of the space 252 of the variable capacity air chamber 250 is changed in accordance with the load of the internal combustion engine 100 has been described. For example, the volume of the space 252 of the variable capacity air chamber 250 may be changed in accordance with the rotational speed of the internal combustion engine 100, the engine temperature (water temperature, oil temperature, etc.), the intake air temperature, the outside air temperature, and the like. .

  As described above, according to the present embodiment, although it is a relatively simple and low-cost configuration, it disturbs with strong air flow in the combustion chamber to promote mixing of fuel and air, and shortens the combustion period. Can provide an internal combustion engine that can improve fuel efficiency and reduce the emission of black smoke (soot), and has a variable capacity air chamber 250 and a volume of the air chamber (space 252). Is configured to be changeable in accordance with the operating state (for example, load, rotation speed, engine temperature, etc.) of the internal combustion engine, the volume of the air chamber (space 252) suitable for the operating state of the internal combustion engine (that is, the operating state) The compression ratio suitable for the engine can be realized, and thus the output performance, fuel consumption performance, exhaust performance, durability, etc. of the internal combustion engine can be further improved in accordance with the operating state.

  In the above embodiment, the volume of the space 252 (stroke position of the piston 254) of the variable capacity air chamber 250 is changed according to the magnitudes of the two loads at the time of low load and high load of the internal combustion engine. However, the present invention is not limited to this, and the load is divided more finely, and the volume of the space 252 of the variable capacity air chamber 250 (the piston 254) is divided according to each load. The stroke position) can be changed finely (the same applies to other operating conditions, not limited to the load).

  In this case, a stroke sensor capable of detecting the stroke position of the piston 254 is provided, and the hydraulic pressure of the hydraulic chamber 256 is feedback-controlled so as to obtain the target stroke position of the piston 254, or a predetermined target stroke of the piston 254 is set. The hydraulic pressure in the hydraulic chamber 256 can be feedforward controlled so that the position can be obtained. For this purpose, for example, the supply hydraulic pressure can be appropriately controlled, or the hydraulic pressure is applied to the hydraulic relief passage 259. The opening degree of the electromagnetic relief valve can be controlled to be predetermined.

  In the present embodiment, the air chamber 200 is provided in a cylindrical shape around the fuel injection nozzle 161 of the fuel injector 160, and the communication portion (throttle portion) 210 is as shown in FIG. 3 and FIG. The case where the fuel injector 160 is provided in an annular shape between the outer periphery of the fuel injector 160 near the tip of the fuel injection nozzle 161 and the cylinder head 110 has been described. However, the present invention is not limited to this, and has a polygonal shape. Other shapes such as an elliptical shape and a petal shape are also possible.

  Further, as shown in FIGS. 3 and 4, the communication portion (throttle portion) 210 is continuous in the circumferential direction between the outer periphery near the tip of the fuel injection nozzle 161 of the fuel injector 160 and the cylinder head 110. It is not limited to the case where it is provided in an annular shape, and it can be formed into a gap shape that is scattered at a predetermined interval in the circumferential direction corresponding to the spraying position or the like.

  In the present embodiment, the variable capacity type air chamber 250 is connected to the air chamber 200 via the air passage 251. However, the present invention is not limited to this, and the variable capacity type air chamber 250 is connected. The air chamber 250 is a fixed air chamber (another air chamber), which is connected to the air chamber 200 via an open / close valve or the like, and the open / close valve is opened / closed according to the operating state, thereby reducing the volume of the air chamber. (The total volume of the air chamber 200 and the volume of the other air chamber) can be variably controlled.

  By the way, in the present embodiment, the piston combustion chamber 121 is illustrated and described as having a two-stage lip structure as described in Patent Document 1, but the present invention is not limited to this, Toroidal combustion chambers, reentrant combustion chambers (see FIG. 7 etc.) and other shapes can be used.

  In the present embodiment, the diesel engine has been described as an example. However, the present invention is not limited to this, and even a fuel other than light oil such as gasoline, natural gas, alcohol, biofuel, or the like is directly combusted. The present invention can be applied to any internal combustion engine that injects fuel into the chamber and is included in the technical scope of the present invention.

  The present invention is not limited to the embodiments of the invention described above, and various modifications can be made without departing from the gist of the present invention.

100 Internal combustion engine
110 Cylinder head 120 Piston 121 Piston combustion chamber (cavity)
150 Combustion Chamber 160 Fuel Injector 161 Fuel Injection Nozzle 200 Air Chamber 210 Communication Portion (Throttle Portion)
300 Air jet 250 Variable capacity air chamber (an example of another air chamber)
251 Air passage 252 Space (corresponding to an example of another air chamber)
254 Piston 255 Piston rod 256 Hydraulic chamber 257 Elastic member 258 Hydraulic supply passage 259 Hydraulic relief passage

Claims (3)

An internal combustion engine comprising a combustion chamber surrounded by a piston top surface of the internal combustion engine, a cylinder head lower surface, and an inner wall of a cylinder in which the piston is slidably accommodated,
A fuel injection nozzle that is attached to the cylinder head and injects fuel from the lower surface of the cylinder head to the combustion chamber,
An air chamber provided on the outer periphery of the fuel injection nozzle;
A communication portion that communicates the air chamber and the combustion chamber;
And comprising
An internal combustion engine characterized in that another air chamber is connected to the air chamber and the volume of the other air chamber is variable . 2. The internal combustion engine according to claim 1, wherein the volume of the other air chamber is variably configured according to an operation state of the internal combustion engine. When the load of the internal combustion engine is high, the volume of the other air chamber is controlled to be large, and when the load of the internal combustion engine is low, the volume of the other air chamber is controlled to be small. The internal combustion engine according to claim 1 or 2 , wherein