JP4306594B2 - Sub-chamber internal combustion engine - Google Patents

Description

  The present invention relates to a sub-chamber internal combustion engine, and more particularly to a sub-chamber internal combustion engine in which hot surface ignition is performed in a sub-combustion chamber.

Conventionally, a sub-chamber internal combustion engine having a main combustion chamber and a sub-combustion chamber provided adjacent to the main combustion chamber has been proposed. (For example, refer to Patent Document 1).
JP-A-6-74137 (page 1-3, Fig. 1-4)

  However, in the internal combustion engine of Patent Document 1, a fuel injection valve is provided in a small auxiliary combustion chamber in addition to a glow plug for hot surface ignition. For this reason, the structure is complicated.

  Further, in the case of adopting a configuration in which liquid fuel is injected into the sub-combustion chamber in the sub-chamber internal combustion engine, the size and shape of the sub-combustion chamber are restricted in order to ensure the stability of fuel vaporization.

  For this reason, it is conceivable that the new air-fuel mixture introduced from the main combustion chamber to the sub-combustion chamber is directly ignited on the hot surface without providing a fuel injection valve in the sub-combustion chamber. The timing (timing) of ignition becomes a matter of course, and it becomes difficult to perform ignition at a desired timing, which may reduce the thermal efficiency of the internal combustion engine.

  An object of the present invention is to provide a sub-chamber internal combustion engine that can improve the thermal efficiency even when adopting a configuration in which fuel is not directly injected into the sub-combustion chamber.

  The sub-chamber internal combustion engine according to the present invention includes a main combustion chamber, a sub-combustion chamber, and ignition means. The auxiliary combustion chamber is adjacent to the main combustion chamber. The ignition means is provided inside the auxiliary combustion chamber, and ignites the fresh air mixture introduced from the main combustion chamber into the auxiliary combustion chamber. In this sub-chamber internal combustion engine, the sub-chamber ignition time is changed. The sub-chamber ignition time is the time from when the fresh air mixture is introduced into the sub-combustion chamber until the new air-fuel mixture is ignited in the sub-combustion chamber.

  Here, the fresh air mixture introduced into the auxiliary combustion chamber is ignited by touching the hot surface of the ignition means (hot surface ignition).

  In the sub-chamber internal combustion engine according to the present invention, the sub-chamber ignition time, which is the time from when the fresh air mixture is introduced from the main combustion chamber to the sub-combustion chamber until the fresh air mixture is ignited, is not particularly devised. In this case, it is determined by the course of events depending on the distance from the main combustion chamber to the ignition means.

  However, according to the present invention, a configuration is adopted in which the sub chamber ignition time is positively changed rather than depending on the outcome. For this reason, ignition can be performed at a desired time, and in the sub-chamber internal combustion engine having a structure in which hot surface ignition is performed in the sub-combustion chamber, thermal efficiency can be improved.

<First Embodiment>
1 and 2 show a sub-chamber internal combustion engine according to a first embodiment of the present invention.

<Configuration of internal combustion engine>
The sub-chamber internal combustion engine 1 includes a main combustion chamber 63, an intake / exhaust mechanism, a fuel injection valve 27, a sub-combustion chamber 61, a glow plug 70, a variable compression ratio mechanism 30, an ECU (control unit) 40, and the like. .

  The main combustion chamber 63 is a chamber surrounded by the cylinder head 20, the cylinder block 10 and the piston 3. As the piston 3 reciprocates along the side wall of the cylinder block 10, the volume of the main combustion chamber 63 changes. The cylinder head 20 is formed with an intake port 23 for supplying fresh air to the main combustion chamber 63 and an exhaust port 24 for discharging burned gas from the main combustion chamber 63 as exhaust gas.

  As an intake / exhaust mechanism, an intake valve 21 is provided in the intake port 23, and an exhaust valve 22 is provided in the exhaust port 24. The intake cam shaft 21b / exhaust cam shaft 22b fixed to the intake cam shaft 21b / exhaust cam shaft 22b rotating in conjunction with the rotation of the crankshaft are arranged above the intake valve 21 / exhaust valve 22. Then, the intake valve 21 / exhaust valve 22 are opened and closed.

  The fuel injection valve 27 is a valve that directly injects gasoline fuel into the main combustion chamber 63. A fuel pump 25 that sends fuel to the fuel injection valve 27 via the fuel pipe 26 is provided near the end of the intake camshaft 21b and pressurizes gasoline fuel.

  The auxiliary combustion chamber 61 is a chamber provided adjacent to the main combustion chamber 63 and is surrounded by the auxiliary combustion chamber wall 61a. Specifically, in the space formed between the intake port 23 and the exhaust port 24 in the cylinder head 20, a substantially cylindrical auxiliary combustion chamber wall 61 a is disposed, and the auxiliary combustion chamber 61 is formed. In addition, a plurality of communication passages 61 b that connect the main combustion chamber 63 and the sub-combustion chamber 61 are formed on the expanded hemispherical bottom surface of the sub-combustion chamber wall 61 a.

  In the glow plug 70, the heat coil pipe 71 (ignition means) extends from a position far from the main combustion chamber 63 to a position close to the main combustion chamber 63 inside the auxiliary combustion chamber 61. In other words, the glow plug 70 is attached to the outside of the auxiliary combustion chamber 61 so that the heat coil pipe 71 protrudes into the auxiliary combustion chamber 61 as shown in FIG. The heat coil pipe 71 of the glow plug 70 has a coil heater 73 and insulating powder therein. By energizing the coil heater 73, the surface of the tip 72 of the heat coil pipe 71 becomes red hot. Here, the tip 72 of the heat coil pipe 71 is positioned near the center of the auxiliary combustion chamber 61.

  Note that the glow plug 70 in which the distal end portion 72 continues to glow red has better ignitability than the spark plug that emits sparks at a predetermined timing, and the fresh air mixture introduced into the auxiliary combustion chamber 61 is very lean. Even in such a state, ignition stability can be ensured.

  The variable compression ratio mechanism 30 is a multi-link piston-crank mechanism that can change the engine compression ratio. As shown in FIG. 2, the variable compression ratio mechanism 30 mainly includes a lower link 31, an upper link 32, a control link 33, an eccentric cam 34, and a compression ratio variable actuator 35. The lower link 31 is externally fitted and supported rotatably on the crankpin 5a of the crankshaft 5. The crankshaft 5 is rotatably supported by the cylinder block 10 via a main bearing. One end of the upper link 32 is rotatably connected to the piston 3 via the piston pin 4. The other end of the upper link 32 is rotatably connected to the lower link 31 via the first connecting pin 32a. When a combustion load acts on the piston 3, this combustion load is transmitted as rotational power from the piston 3 to the crankshaft 5 via the upper link 32 and the lower link 31. One end of the control link 33 is rotatably connected to the lower link 31 via the second connection pin 33a. The other end of the control link 33 is rotatably fitted and supported on the eccentric cam 34. The eccentric cam 34 is eccentrically fixed to the control shaft 36. The control shaft 36 is a shaft that is rotatably supported by the cylinder block 10. A control plate 37 having a slide groove 37 a is fixed to one end of the control shaft 36. The variable compression ratio actuator 35 plays a role of rotating the control shaft 36 relative to the cylinder block 10 or holding the control shaft 36 so as not to rotate relative to the cylinder block 10. The variable compression ratio actuator 35 is an electric type, and mainly includes a substantially cylindrical thread drive 35a, a rod-shaped thread driven 35b, and an electric motor (not shown) as a driving device. The thread drive 35a is a cylindrical member that is driven to rotate about an axis by an electric motor, and a gear is formed on an inner peripheral surface thereof. The thread driven 35b meshes with the gear on the inner peripheral surface of the thread drive 35a, and advances and retreats in the axial direction (direction D1 in FIG. 2) according to the rotation of the thread drive 35a. A control shaft pin 35c is provided at the tip of the thread driven 35b. The control shaft pin 35 c is slidably fitted in the slide groove 37 a of the control plate 37. By rotating the control shaft 36 by the compression ratio variable actuator 35, the piston stroke with respect to the crank angle θ changes, and the engine compression ratio changes. The variable compression ratio actuator 35 may be hydraulically driven.

  The ECU 40 receives signal inputs from sensors such as a crank angle sensor 51, a water temperature sensor 52, and an accelerator opening sensor 53, and outputs an engine torque corresponding to the accelerator opening required by the driver so as to output the engine torque and ignition. This is a control device for appropriately controlling the combustion state in the main combustion chamber 63 by adjusting timing, throttle opening, and the like. The ECU 40 is electrically connected to the fuel injection valve 27, the fuel pump 25, the glow plug 70, the electric motor of the variable compression ratio mechanism 30, and the like, for example, according to the engine load calculated by the load calculation unit 41. At 42, a necessary fuel injection amount is determined and a command is sent to the fuel injection valve 27.

<General operation of internal combustion engine>
In the internal combustion engine 1, the fuel pressurized by the fuel pump 25 is supplied to the fuel injection valve 27 via the fuel pipe 26 in the intake stroke. The fuel injection valve 27 injects fuel into fresh air supplied from the intake port 23 to the main combustion chamber 63. As a result, a substantially homogeneous fresh air mixture is generated in the main combustion chamber 63.

  In the compression stroke, the fresh air mixture is compressed in the main combustion chamber 63, and a part of the fresh air mixture in the main combustion chamber 63 is transferred from the main combustion chamber 63 to the auxiliary combustion chamber 61 via the communication passage 61b. be introduced.

  In the sub-combustion chamber 61, when the fresh air mixture comes into contact with the heat coil pipe 71 of the glow plug 70, the fresh air mixture is ignited by the hot surface and burned. The combustion gas (flame) in the auxiliary combustion chamber 61 is radiated in a torch shape to the main combustion chamber 63 through the communication passage 61b, and the homogeneous fresh air mixture in the main combustion chamber 63 is combusted.

  In the expansion stroke, the piston 3 is pushed down by the combustion pressure generated by burning the fresh air mixture.

  In the exhaust stroke, the burned gas burned in the main combustion chamber 63 is discharged to the exhaust port 24 as exhaust gas.

<Details of ignition operation in auxiliary combustion chamber of internal combustion engine>
A substantially homogeneous fresh air mixture (see the fresh air mixture MG in FIG. 3) is introduced into the auxiliary combustion chamber 61 from the main combustion chamber 63 through the communication passage 61b in the compression stroke. At this time, as shown in FIG. 3, the residual gas RG and the fresh air mixture MG in the auxiliary combustion chamber 61 are distributed in a layered manner in the auxiliary combustion chamber 61. That is, the fresh air mixture MG introduced into the auxiliary combustion chamber 61 in the compression stroke pushes the residual gas RG upward of the auxiliary combustion chamber 61. As a result, the residual gas RG is distributed in the upper space of the auxiliary combustion chamber 61, and the fresh air mixture MG is distributed in the remaining region (lower space) of the auxiliary combustion chamber 61. In FIG. 3, the boundary between the residual gas RG and the fresh air mixture MG is indicated by a broken line.

  The boundary between the residual gas RG and the fresh air mixture MG in the auxiliary combustion chamber 61 is relatively far from the main combustion chamber 63 when the compression ratio is high, for example, when the piston 3 is at the top dead center. The position is relatively close to the main combustion chamber 63 when the compression ratio is low.

  Therefore, when the engine compression ratio is high, it is the time from when the fresh air mixture MG is introduced into the auxiliary combustion chamber 61 until the fresh air mixture MG touches the tip 72 of the heat coil pipe 71 and ignites. The secondary chamber ignition time is shortened. On the other hand, when the engine compression ratio is low, the sub chamber ignition time becomes long.

  From another viewpoint, since the residual gas RG and the fresh air mixture MG in the auxiliary combustion chamber 61 are distributed in layers, when the piston 3 is at the top dead center and the engine compression ratio is high, It can be said that the residual gas ratio increases when the residual gas ratio, which is the ratio of the volume occupied by the residual gas RG in the sub-combustion chamber 61, decreases, and the engine compression ratio is low. The sub chamber ignition time is shortened when the residual gas ratio is small, and the sub chamber ignition time is long when the residual gas ratio is large.

<Control of internal combustion engine>
First, in the internal combustion engine 1, the ECU 40 controls the average equivalence ratio of the entire combustion chamber as indicated by a two-dot chain line in FIG. That is, the control is performed so that the average equivalence ratio of the entire combustion chamber is leaner than the theoretical equivalence ratio under operating conditions with a relatively low engine load, and the average of the entire combustion chamber is controlled under operating conditions with a relatively high engine load. The equivalence ratio is controlled so as to be approximately the theoretical equivalence ratio, and under the operating conditions where the engine load is near the maximum load, the average equivalence ratio of the entire combustion chamber is controlled to be richer than the theoretical equivalence ratio.

  In view of the characteristics of the ignition operation in the sub-combustion chamber 61 as described above, the ECU 40 of the internal combustion engine 1 controls the ignition timing in the sub-combustion chamber 61 as follows, and the ignition timing is suitable for the engine load. The timing (hereinafter referred to as the auxiliary combustion chamber required ignition timing).

  Specifically, the ignition timing in the auxiliary combustion chamber 61 is controlled according to the engine load so that the relationship between the engine load and the auxiliary combustion chamber required ignition timing shown in FIG. 4 is established.

  As shown in FIG. 4, the lower the engine load, the lower the combustion temperature and the lower the combustion speed, so the cooling loss becomes smaller. For this reason, when the engine load becomes low, the required combustion timing for generating the maximum torque is relatively shifted to the advance side. Along with this, the auxiliary combustion chamber required ignition timing is also relatively shifted to the advance side. On the contrary, when the engine load increases, the required combustion timing for generating the maximum torque shifts relatively to the retard side, and the auxiliary combustion chamber required ignition timing also shifts to the relatively retard side.

  The ECU 40 controls the variable compression ratio mechanism 30 by the compression ratio control unit 43 in accordance with the engine load calculated by the load calculation unit 41 so that the ignition in the sub combustion chamber 61 occurs at the required ignition timing shown in FIG. I have control.

  As described above, when the engine compression ratio is high, the residual gas ratio becomes small and the sub chamber ignition time becomes short. When the engine compression ratio is low, the residual gas ratio becomes large and the sub chamber ignition time becomes long. Therefore, the ignition timing in the auxiliary combustion chamber 61 can be controlled by controlling the variable compression ratio mechanism 30 to change the engine compression ratio. In view of this, the ECU 40 controls the variable compression ratio mechanism 30 so that the engine compression ratio indicated by the one-dot chain line in FIG. 6 is obtained, so that the residual gas ratio in the auxiliary combustion chamber 61 becomes the shape indicated by the solid line in FIG. ing. As a result, a state in which the residual gas ratio is reduced as the engine load is reduced is realized, and a state in which the ignition timing in the auxiliary combustion chamber 61 is accelerated is shortened as the engine load is reduced. Then, the relationship between the engine load and the auxiliary combustion chamber required ignition timing shown in FIG. 4 is established, and high thermal efficiency of the internal combustion engine 1 is ensured.

  The residual gas ratio in FIGS. 5 and 6 indicates the ratio of the volume of the residual gas RG in the auxiliary combustion chamber 61 at the top dead center.

<Characteristics of internal combustion engine>
In the internal combustion engine 1, the sub chamber ignition time, which is the time from when the fresh air mixture MG is introduced into the sub combustion chamber 61 to when the fresh air mixture MG touches the tip 72 of the heat coil pipe 71 and ignites, is changed. The sub-chamber ignition time is made shorter during low load operation than during high load operation.

  Specifically, the ECU 40 controls the variable compression ratio mechanism 30 to change the engine compression ratio in accordance with the engine load as shown by a one-dot chain line in FIG. The sub-chamber ignition time during low-load operation is made shorter than the sub-chamber ignition time during high-load operation.

  As a result, the relationship between the engine load and the auxiliary combustion chamber required ignition timing shown in FIG. 4 is realized, and the thermal efficiency of the internal combustion engine 1 can be increased.

<Modification of Internal Combustion Engine According to First Embodiment>
(1)
In the first embodiment, the glow plug 70 in which only the distal end portion 72 of the heat coil pipe 71 is a red hot ignition portion is employed. However, the glow plug having the heat coil pipe 71a shown in FIG. Can also be adopted.

  In the heat coil pipe 71a, in addition to the first heater part 72a at the tip, a second heater part 72b is formed at a position farther from the main combustion chamber 63 than the first heater part 72a. A current is passed through the coil heater 73b of the second heater portion 72b at a higher applied voltage than the coil heater 73a of the first heater portion 72a. Thereby, the surface temperature of the 2nd heater part 72b is higher than the surface temperature of the 1st heater part 72a.

  In this case, when the fresh air mixture introduced from the main combustion chamber 63 to the sub combustion chamber 61 is relatively lean, even if the fresh air mixture reaches the first heater portion 72a having a low surface temperature, it does not ignite. When the fresh air mixture reaches the second heater portion 72b having a high surface temperature, ignition is performed in the auxiliary combustion chamber 61 for the first time. On the contrary, when the fresh air mixture is relatively rich, ignition is performed in the auxiliary combustion chamber 61 when the fresh air mixture reaches the first heater portion 72a having a low surface temperature.

  As described above, by providing the first heater portion 72a and the second heater portion 72b having different surface temperatures, the ignition timing in the auxiliary combustion chamber 61 is changed in accordance with the equivalence ratio of the fresh air mixture that changes according to the engine load. Will be able to.

(2)
In the modified example (1), the surface temperature of the first heater portion 72a and the surface temperature of the second heater portion 72b are made different by changing the applied voltage, but as shown in FIG. 7B. A difference may be made by changing the number of turns of the coil heater.

  In the heat coil pipe 71b shown in FIG. 7B, a second heater part 72d is formed at a position farther from the main combustion chamber 63 than the first heater part 72c, in addition to the first heater part 72c at the tip. The coil heater 73d of the second heater part 72d is wound more densely than the coil heater 73c of the first heater part 72c, and has a large number of turns. Thereby, the surface temperature of the 2nd heater part 72d becomes higher than the surface temperature of the 1st heater part 72c.

(3)
In the above modifications (1) and (2), the plurality of heater portions each have a coil heater, but a common coil heater can be adopted for the plurality of heater portions.

  In the heat coil pipe 71c shown in FIG. 7C, a plurality of heater portions, specifically the first heater portion 72e and the second heater portion, are directed from the distal end toward the proximal end (in the direction away from the main combustion chamber 63). A heater part 72f and a third heater part 72g are provided. One coil heater 73e is arranged inside these heater portions 72e, 72f, 72g. The coil heater 73e is tightly wound as the distance from the main combustion chamber 63 increases, that is, as the distance from the tip increases, and the number of turns per unit length increases. Thereby, the surface temperature of the second heater part 72f is higher than the surface temperature of the first heater part 72e, and the surface temperature of the third heater part 72g is higher than the surface temperature of the second heater part 72f. . In other words, in the heat coil pipe 71c, the surface temperature gradually increases with increasing distance from the tip, and the ignitability varies in the longitudinal direction (the direction away from the main combustion chamber 63).

(4)
In the above modification (1), the difference in ignitability is produced by changing the applied voltage to make a difference between the surface temperature of the first heater portion 72a and the surface temperature of the second heater portion 72b. As shown in (D), a difference in ignitability may be generated by coating the surface with a different catalyst.

  In the heat coil pipe 71d shown in FIG. 7D, in addition to the first heater portion 72h at the tip, a second heater portion 72i is formed at a position farther from the main combustion chamber 63 than the first heater portion 72h. The coil heater 73g of the second heater part 72i has the same number of turns as the coil heater 73f of the first heater part 72h, and the applied voltage is also the same. However, the surface of the first heater portion 72h is coated with the first catalyst 74a, and the surface of the second heater portion 72i is coated with the second catalyst 74b. As the first catalyst 74a and the second catalyst 74b, any catalyst such as platinum, aluminum, platinum, copper may be used. Here, the first catalyst 74a and the first catalyst 74a and the second catalyst 74b are coated so that the ignitability of the second heater part 72i is higher than the ignitability of the first heater part 72h coated with the first catalyst 74a. The catalyst component of the two catalyst 74b is selected.

  As described above, by providing the first heater portion 72h and the second heater portion 72i having different ignitability, the ignition timing in the auxiliary combustion chamber 61 is changed in accordance with the equivalence ratio of the fresh air mixture that changes according to the engine load. Will be able to.

  It should be noted that the first heater unit and the second heater unit may be replaced with a method of making a difference in the ignitability of the first heater unit 72h and the second heater unit 72i depending on the difference in the catalyst components of the first catalyst 74a and the second catalyst 74b. A method for producing a difference in ignitability by changing the amount of catalyst to be coated, or a method for producing a difference in ignitability by changing the catalyst coating area for the first heater part and the catalyst coating area for the second heater part. It may be used.

  Further, the first heater part 72h and the second heater part 72i are not provided with the coil heaters 73f and 73g, respectively, but the first heater part 72h and the second heater part 72i are provided with a common coil heater. It is also possible to do.

(5)
In the first embodiment, the pressurized fuel is directly injected from the fuel injection valve 27 into the main combustion chamber 63. However, the present invention is a sub chamber configured to inject fuel into the intake port 23. The present invention can also be applied to an internal combustion engine.

Second Embodiment
8 and 9 show a sub-chamber internal combustion engine according to the second embodiment of the present invention.

  The sub-chamber internal combustion engine 1a includes a main combustion chamber 63, an intake / exhaust mechanism, a fuel injection valve 27, a sub-combustion chamber 61, a glow plug 70, variable valve timing mechanisms 81 and 82, a supercharger 90, and an ECU (control unit). 40a and the like.

  In the internal combustion engine 1a of the present embodiment, variable valve timing mechanisms 81 and 82 and a supercharger 90 are provided instead of the variable compression ratio mechanism 30 in the internal combustion engine 1 of the first embodiment. Since the configuration other than the ECU 40a is the same as that of the internal combustion engine 1 of the first embodiment, the same reference numerals are given to the same components in the internal combustion engine 1a of the second embodiment, and repeated explanation is in principle. It omits as. The glow plug 70 is the same as that of the first embodiment, and the one shown in FIG. 3 is adopted.

<Configuration of variable valve timing mechanism>
The variable valve timing mechanisms 81 and 82 are hydraulically driven, and the opening / closing timing of the intake valve 21 and the exhaust valve 22 is advanced or retarded by changing the phase of the camshafts 21b and 22b with respect to the crankshaft. . Since the specific configuration of the variable valve timing mechanisms 81 and 82 is well known, the description thereof is omitted here.

  Instead of the hydraulically driven variable valve timing mechanisms 81 and 82, a variable valve timing mechanism that changes the phase of the camshaft relative to the crankshaft using friction braking by an electromagnetic brake may be employed. For example, a variable valve timing device disclosed in Japanese Patent Laid-Open No. 2002-97908 can be employed.

<Structure of turbocharger>
The supercharger 90 is a turbocharger with a variable nozzle mechanism, and mainly includes a compressor 91 disposed in an intake passage connected to the intake port 23 and a turbine disposed in an exhaust passage downstream of the exhaust port 24. 92, a coupling shaft 93, and a variable nozzle mechanism 94. The coupling shaft 93 couples the rotating shaft of the compressor 91 and the rotating shaft of the turbine 92. The variable nozzle mechanism 94 can vary the supercharging pressure by controlling the nozzle.

  The variable nozzle mechanism 94 of the supercharger 90 is controlled by the supercharging pressure control unit 45 of the ECU 40a.

<Configuration of ECU>
The ECU 40a receives signal inputs from sensors such as the crank angle sensor 51, the water temperature sensor 52, and the accelerator opening sensor 53, and outputs the fuel injection amount, ignition so that the engine torque corresponding to the accelerator opening requested by the driver can be output. This is a control device for appropriately controlling the combustion state in the main combustion chamber 63 by adjusting timing, throttle opening, and the like. The ECU 40 is electrically connected to the fuel injection valve 27, the fuel pump 25, the glow plug 70, the hydraulic drive device of the variable valve timing mechanisms 81 and 82, the variable nozzle mechanism 94 of the supercharger 90, etc. The fuel injection control unit 42 determines a necessary fuel injection amount according to the engine load calculated by the unit 41 and sends a command to the fuel injection valve 27.

<General operation of internal combustion engine>
This is the same as in the first embodiment.

<Details of ignition operation in auxiliary combustion chamber of internal combustion engine>
This is the same as in the first embodiment.

<Control of internal combustion engine>
First, also in the internal combustion engine 1a, as in the first embodiment, the ECU 40a controls the average equivalence ratio of the entire combustion chamber as indicated by a two-dot chain line in FIG. That is, the control is performed so that the average equivalence ratio of the entire combustion chamber is leaner than the theoretical equivalence ratio under operating conditions with a relatively low engine load, and the average of the entire combustion chamber is controlled under operating conditions with a relatively high engine load. The equivalence ratio is controlled so as to be approximately the theoretical equivalence ratio, and under the operating conditions where the engine load is near the maximum load, the average equivalence ratio of the entire combustion chamber is controlled to be richer than the theoretical equivalence ratio.

  In view of the characteristics of the ignition operation in the sub-combustion chamber 61, the ECU 40a of the internal combustion engine 1a controls the ignition timing in the sub-combustion chamber 61 as follows, and sets the ignition timing to a time suitable for the engine load (sub-combustion). Room required ignition time).

  Specifically, the ignition timing in the auxiliary combustion chamber 61 is controlled according to the engine load so that the relationship between the engine load and the auxiliary combustion chamber required ignition timing shown in FIG. 4 is established.

  The ECU 40a controls the variable valve timing mechanism 81 by the valve timing control unit 44 in accordance with the engine load calculated by the load calculation unit 41 so that the ignition in the auxiliary combustion chamber 61 occurs at the required ignition timing of the auxiliary combustion chamber shown in FIG. Control is performed to adjust the timing at which the intake valve 21 is closed (hereinafter referred to as intake valve closing timing), and the supercharger 90 is controlled by the supercharging pressure control unit 45 to vary the supercharging pressure. These controls will be described with reference to FIG.

  FIG. 10 shows the relationship between the engine load and the intake valve closing timing, the relationship between the engine load and the supercharging pressure, and the relationship between the engine load and the residual gas ratio. The variable valve timing mechanism 81 and the supercharger 90 are controlled by the ECU 40a so that these relationships are as shown in FIG.

  First, regarding the relationship between the engine load and the intake valve closing timing, the ECU 40a is variable so that the intake valve closing timing approaches the bottom dead center as the engine load decreases, as indicated by a two-dot chain line in FIG. The valve timing mechanism 81 is controlled. As a result, the effect of increasing the pressure of the fresh air mixture at the top dead center as the engine load decreases (an effect of increasing the effective compression ratio) is obtained, and the residual gas ratio in the auxiliary combustion chamber 61 is reduced during low load operation. The ignition timing in the auxiliary combustion chamber 61 is advanced as the engine load decreases, and the relationship between the engine load and the auxiliary combustion chamber required ignition timing shown in FIG. 4 is established.

  Further, regarding the relationship between the engine load and the supercharging pressure, the ECU 40a controls the supercharger 90 so as to increase the supercharging pressure as the engine load increases, as indicated by the broken line in FIG. ing. As a result, it is possible to suppress a malfunction caused by keeping the intake valve closing timing away from the bottom dead center when the engine load is high, that is, a decrease in charging efficiency at the time of high load. In other words, since the supercharging pressure is controlled to be high at a high load, a predetermined charging efficiency can be ensured even when the intake valve closing timing is away from the bottom dead center.

  Thus, also in the internal combustion engine 1a of the second embodiment, the state shown by the solid line in FIG. 10 in which the residual gas ratio in the auxiliary combustion chamber 61 decreases as the engine load decreases, and the auxiliary chamber decreases as the engine load decreases. A state in which the ignition time is shortened and the ignition timing in the auxiliary combustion chamber 61 is advanced is realized. Then, the relationship between the engine load and the auxiliary combustion chamber required ignition timing shown in FIG. 4 is established, and high thermal efficiency of the internal combustion engine 1 is ensured.

  In addition, the residual gas ratio in FIG. 10 has shown the ratio of the volume of the residual gas in the subcombustion chamber 61 in a top dead center.

<Characteristics of internal combustion engine>
In the internal combustion engine 1a of the second embodiment, the sub chamber ignition is the time from when the fresh air mixture is introduced into the sub combustion chamber 61 until the fresh air mixture touches the tip 72 of the heat coil pipe 71 and ignites. The time is changed so that the ignition time of the sub-chamber is shorter in the low load operation than in the high load operation.

  Specifically, the ECU 40a controls the variable valve timing mechanism 81 to change the intake valve closing timing as shown by a two-dot chain line in FIG. 10 according to the engine load, whereby the residual gas ratio in the auxiliary combustion chamber 61 is changed. As shown by the solid line in FIG. 10, the sub chamber ignition time during the low load operation is made shorter than the sub chamber ignition time during the high load operation.

  Thereby, the relationship between the engine load and the required combustion chamber required ignition timing shown in FIG. 4 is realized, and the thermal efficiency of the internal combustion engine 1a can be increased.

<Third Embodiment>
FIG. 11 shows a sub-chamber internal combustion engine according to the third embodiment of the present invention.

  The sub-chamber internal combustion engine 1b includes a main combustion chamber 63, an intake / exhaust mechanism, a fuel injection valve 27, a sub-combustion chamber 61, a glow plug 70, an ECU (control unit) 40b, and the like.

  In the internal combustion engine 1b of the present embodiment, a bypass passage 97 and a bypass valve 98 for discharging residual gas from the auxiliary combustion chamber 61 to the exhaust port 24 instead of the variable compression ratio mechanism 30 in the internal combustion engine 1 of the first embodiment. And are deployed. Since the configuration other than the ECU 40b is the same as that of the internal combustion engine 1 of the first embodiment, the same reference numerals are given to the same components in the internal combustion engine 1b of the third embodiment, and the repeated description is in principle. It omits as. The glow plug 70 is the same as that of the first embodiment, and the one shown in FIG. 3 is adopted.

<Configuration of auxiliary combustion chamber>
The auxiliary combustion chamber 61 is a chamber provided adjacent to the main combustion chamber 63 and is surrounded by the auxiliary combustion chamber wall 61a. Specifically, in the space formed between the intake port 23 and the exhaust port 24 in the cylinder head 20, a substantially cylindrical auxiliary combustion chamber wall 61 a is disposed, and the auxiliary combustion chamber 61 is formed. In addition, a plurality of communication passages 61 b that connect the main combustion chamber 63 and the sub-combustion chamber 61 are formed on the expanded hemispherical bottom surface of the sub-combustion chamber wall 61 a.

  As shown in FIG. 3, the glow plug 70 is attached to the outside of the auxiliary combustion chamber 61 so that the heat coil pipe 71 protrudes into the auxiliary combustion chamber 61.

  The bypass passage 97 extends from the uppermost portion of the auxiliary combustion chamber 61 (the portion far from the main combustion chamber 63) to the exhaust port 24 and connects the auxiliary combustion chamber 61 and the exhaust port 24, and is formed in the cylinder head 20. ing. The residual gas in the auxiliary combustion chamber 61 passing through the bypass passage 97 is scavenged to the exhaust port 24 without passing through the main combustion chamber 63, that is, without passing through the main combustion chamber 63.

  The bypass valve 98 is an open / close control valve that opens and closes the bypass passage 97, and is provided in the bypass passage 97. The bypass valve 98 can be configured similarly to the intake valve 21 and the exhaust valve 22, for example, but any structure can be used as long as the bypass passage 97 can be opened and closed. The opening / closing timing of the bypass valve 98 is controlled by the ECU 40b. By this control, the scavenging amount of the residual gas in the auxiliary combustion chamber 61 to the exhaust port 24 is adjusted.

<Configuration of ECU>
The ECU 40b receives signal inputs from sensors such as the crank angle sensor 51, the water temperature sensor 52, and the accelerator opening sensor 53, and outputs an engine torque corresponding to the accelerator opening required by the driver so as to output the engine torque and ignition. This is a control device for appropriately controlling the combustion state in the main combustion chamber 63 by adjusting timing, throttle opening, and the like. The ECU 40 is electrically connected to the fuel injection valve 27, the fuel pump 25, the glow plug 70, the bypass valve 98, and the like, and is required in the fuel injection control unit 42 according to the engine load calculated by the load calculation unit 41, for example. The fuel injection amount is determined and a command is sent to the fuel injection valve 27.

<General operation of internal combustion engine>
This is the same as in the first embodiment.

<Details of ignition operation in auxiliary combustion chamber of internal combustion engine>
This is the same as in the first embodiment.

<Control of internal combustion engine>
First, also in the internal combustion engine 1b, as in the first embodiment, the ECU 40b controls the average equivalent ratio of the entire combustion chamber as indicated by a two-dot chain line in FIG. That is, the control is performed so that the average equivalence ratio of the entire combustion chamber is leaner than the theoretical equivalence ratio under operating conditions with a relatively low engine load, and the average of the entire combustion chamber is controlled under operating conditions with a relatively high engine load. The equivalence ratio is controlled so as to be approximately the theoretical equivalence ratio, and under the operating conditions where the engine load is near the maximum load, the average equivalence ratio of the entire combustion chamber is controlled to be richer than the theoretical equivalence ratio.

  In view of the characteristics of the ignition operation in the sub-combustion chamber 61, the ECU 40b of the internal combustion engine 1b controls the ignition timing in the sub-combustion chamber 61 as follows, and sets the ignition timing to a time suitable for the engine load (sub-combustion). Room required ignition time).

  Specifically, the ignition timing in the auxiliary combustion chamber 61 is controlled according to the engine load so that the relationship between the engine load and the auxiliary combustion chamber required ignition timing shown in FIG. 4 is established.

  As shown in FIG. 12, the bypass valve control unit 46 of the ECU 40b responds to the engine load calculated by the load calculation unit 41 so that the ignition in the auxiliary combustion chamber 61 occurs at the required ignition timing shown in FIG. Timing for closing the bypass valve 98 (hereinafter referred to as bypass valve closing timing) is adjusted.

  The control of the bypass valve 98 is basically opened during the exhaust stroke and closed during the compression stroke. In addition, the bypass valve closing timing in the compression stroke is retarded as the engine load decreases, and advanced as the engine load increases. As described above, since the bypass valve closing timing is retarded under operating conditions where the engine load is low, the residual gas ratio in the auxiliary combustion chamber 61 becomes low at low loads, and the ignition timing is advanced. On the other hand, since the bypass valve closing timing is advanced under operating conditions where the engine load is high, the residual gas ratio in the auxiliary combustion chamber 61 increases at high loads, and the ignition timing is retarded. That is, the relationship between the engine load and the auxiliary combustion chamber required ignition timing shown in FIG. 4 is established.

  Thus, also in the internal combustion engine 1b of the third embodiment, the state shown by the solid line in FIG. 5 that the residual gas ratio in the auxiliary combustion chamber 61 decreases as the engine load decreases, and the auxiliary chamber decreases as the engine load decreases. A state in which the ignition time is shortened and the ignition timing in the auxiliary combustion chamber 61 is advanced is realized. Then, the relationship between the engine load and the auxiliary combustion chamber required ignition timing shown in FIG. 4 is established, and high thermal efficiency of the internal combustion engine 1 is ensured.

<Characteristics of internal combustion engine>
In the internal combustion engine 1b of the third embodiment, the sub chamber ignition is the time from when the fresh air mixture is introduced into the sub combustion chamber 61 until the fresh air mixture touches the tip 72 of the heat coil pipe 71 and ignites. The time is changed so that the ignition time of the sub-chamber is shorter in the low load operation than in the high load operation.

  Specifically, the ECU 40b controls the bypass valve 98 to change the bypass valve closing timing in the compression stroke as shown in FIG. 12 according to the engine load, so that the residual gas ratio in the auxiliary combustion chamber 61 is changed as shown in FIG. As shown by the solid line, the sub-chamber ignition time during low-load operation is made shorter than the sub-chamber ignition time during high-load operation.

  As a result, the relationship between the engine load and the auxiliary combustion chamber required ignition timing shown in FIG. 4 is realized, and the thermal efficiency of the internal combustion engine 1b can be increased.

<Modification of Internal Combustion Engine According to Third Embodiment>
(1)
The internal combustion engine 1b according to the third embodiment does not have the variable compression ratio mechanism like the internal combustion engine 1 according to the first embodiment, but may further have a variable compression ratio mechanism.

(2)
The internal combustion engine 1b according to the third embodiment employs a configuration in which residual gas is discharged from the auxiliary combustion chamber 61 to the exhaust port 24 by the bypass passage 97, but is configured to discharge residual gas from the auxiliary combustion chamber 61 to the intake port 23. It is also possible to adopt

  The sub-chamber internal combustion engine according to the present invention can be ignited at a desired time to improve thermal efficiency, and is useful as a sub-chamber internal combustion engine in which hot surface ignition is performed in the sub-combustion chamber.

1 is an overall schematic diagram of a sub-chamber internal combustion engine according to a first embodiment of the present invention. Schematic of the variable compression ratio mechanism of the first embodiment. The enlarged view of the glow plug inside the subcombustion chamber of 1st Embodiment. The figure which shows the relationship between the engine load in 1st Embodiment, and a subcombustion chamber required ignition timing. The figure which shows the relationship between the engine load in 1st Embodiment, the equivalence ratio, and the residual gas ratio of a subcombustion chamber. The figure which shows the relationship between the engine load and engine compression ratio in 1st Embodiment. The enlarged view of the heat coil pipe of the glow plug of each modification of 1st Embodiment. The whole schematic diagram of the subchamber internal combustion engine concerning a 2nd embodiment of the present invention. The schematic of the supercharger of 2nd Embodiment. The figure which shows the relationship between the engine load in 2nd Embodiment, an intake valve closing timing, the residual gas ratio of a subcombustion chamber, and a supercharging pressure. The whole schematic diagram of the subchamber internal combustion engine concerning a 3rd embodiment of the present invention. The figure which shows the relationship between the engine load and bypass valve closing timing in 3rd Embodiment.

Explanation of symbols

1 Sub-chamber internal combustion engine 21 Intake valve 30 Variable compression ratio mechanism 40, 40a, 40b ECU (control unit)
61 Subcombustion chamber 63 Main combustion chamber 70 Glow plug 71 Heat coil pipe (ignition means)
71, 71a, 71b, 71c, 71d Heat coil pipe 72a, 72c, 72e, 72h 1st heater part (ignition part)
72b, 72d, 72f, 72i Second heater part (ignition part)
72g 3rd heater part (ignition part)
73a to 73g Coil heater 74a First catalyst 74b Second catalyst 81, 82 Variable valve timing mechanism 90 Supercharger 97 Bypass passage (residual gas discharge passage)
98 Bypass valve (control valve)

Claims (17)

A main combustion chamber;
A secondary combustion chamber adjacent to the main combustion chamber;
Ignition means provided inside the auxiliary combustion chamber, for igniting hot air of a fresh air mixture introduced from the main combustion chamber to the auxiliary combustion chamber;
With
When the low-load operation is performed, the residual gas ratio in the sub-combustion chamber in the vicinity of the top dead center is reduced compared with that during the high-load operation, so that the fresh air-fuel mixture is introduced into the sub-combustion chamber and A sub-chamber internal combustion engine in which the sub-chamber ignition time, which is the time until the new air-fuel mixture is ignited, is shorter during low-load operation than during high-load operation . The ignition means has a plurality of ignition parts having different ignitability, and an ignition part having high ignitability is disposed at a position away from the main combustion chamber as compared with an ignition part having low ignitability.
The sub-chamber internal combustion engine according to claim 1 . A variable compression ratio mechanism that changes the engine compression ratio;
A control unit that controls the variable compression ratio mechanism and sets the engine compression ratio higher during the low load operation than during the high load operation;
Further comprising, pre-combustion chamber internal combustion engine according to claim 1. A variable valve timing mechanism for changing the opening and closing timing of the intake valve of the main combustion chamber;
A control unit that controls the variable valve timing mechanism, and sets the timing at which the intake valve closes near the bottom dead center at the time of the low load operation compared to the time of the high load operation;
Further comprising, pre-combustion chamber internal combustion engine according to claim 1. A residual gas discharge passage for discharging residual gas from the auxiliary combustion chamber without passing through the main combustion chamber;
A control valve provided in the residual gas discharge passage;
Further comprising, pre-combustion chamber internal combustion engine according to claim 1. The plurality of ignition parts differ in ignitability due to differences in surface temperature.
The sub-chamber internal combustion engine according to claim 2 . The ignition means has a plurality of heater parts having different surface temperatures as the plurality of ignition parts.
The sub-chamber internal combustion engine according to claim 6 . The ignition means has a heater part having a temperature gradient on the surface as the plurality of ignition parts.
The sub-chamber internal combustion engine according to claim 6 . Each of the plurality of ignition parts has a coil heater, and the surface temperature differs due to a difference in applied voltage to the coil heater.
The sub-chamber internal combustion engine according to any one of claims 6 to 8 . Each of the plurality of ignition parts has a coil heater, and the surface temperature varies depending on the number of turns of the coil heater.
The sub-chamber internal combustion engine according to any one of claims 6 to 8 . The plurality of ignition parts have different ignitability depending on the catalyst to be coated.
The sub-chamber internal combustion engine according to claim 2 . The ignition means has a plurality of heater portions with different catalysts to be coated as the plurality of ignition portions,
The sub-chamber internal combustion engine according to claim 11 . The ignition means has a heater portion coated with a plurality of catalysts having different ignitability as the plurality of ignition portions.
The sub-chamber internal combustion engine according to claim 11 . The plurality of ignition parts have different ignitability due to differences in catalyst components of the catalyst to be coated,
The sub-chamber internal combustion engine according to any one of claims 11 to 13 . The plurality of ignition parts differ in ignitability depending on the difference in the amount of catalyst to be coated,
The sub-chamber internal combustion engine according to any one of claims 11 to 13 . The plurality of ignition parts differ in ignitability depending on the difference in the coating area of the catalyst to be coated,
The sub-chamber internal combustion engine according to any one of claims 11 to 13 . Further comprising a supercharger for increasing the pressure of the gas supplied to the main combustion chamber;
The control unit sets the timing at which the intake valve closes away from the bottom dead center at the time of the high load operation compared to the low load operation, and controls the supercharger to enter the main combustion chamber. Increase the pressure of fresh air to supply,
The sub-chamber internal combustion engine according to claim 4 .

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