JP4470724B2 - Sub-chamber internal combustion engine - Google Patents

Description

  The present invention relates to a sub-chamber internal combustion engine.

Conventionally, a sub-combustion type internal combustion engine including a main combustion chamber and a sub-combustion chamber provided adjacent to the main combustion chamber has been proposed (see, for example, Patent Document 1).
JP-A-6-272560 (page 1-4, FIG. 1-5)

  In the prior art, the check valve is opened and closed by changing the difference between the fuel pressure and the pressure in the auxiliary combustion chamber, and the fuel is supplied to the auxiliary combustion chamber via the check valve.

  However, in the conventional technology, the check valve is opened and closed uniformly regardless of the operating state, and therefore the fuel supplied to the auxiliary combustion chamber may not be an appropriate amount depending on the operating state.

  Therefore, an object of the present invention is to provide a sub-chamber internal combustion engine that can supply an appropriate amount of fuel to the sub-combustion chamber according to the operating state.

The sub-chamber internal combustion engine according to the present invention includes a combustion chamber, a fuel supply unit, and a control unit.
The combustion chamber has a main combustion chamber and a sub-combustion chamber.
The auxiliary combustion chamber communicates adjacent to the main combustion chamber.
The fuel supply unit supplies fuel to the auxiliary combustion chamber via the check valve.
The check valve is opened when the difference between the fuel pressure and the combustion chamber pressure is greater than or equal to the boundary value, and the check valve is closed when the difference between the fuel pressure and the combustion chamber pressure is less than the boundary value. .
The control unit controls the length of time during which the pressure in the combustion chamber is lower than the fuel pressure by a boundary value or more according to the operating state.

  In this sub-chamber internal combustion engine, the control unit controls the pressure of the combustion chamber to be smaller than the fuel pressure by a boundary value or more according to the operating state. Thereby, the difference between the pressure of the fuel and the pressure of the combustion chamber can be made equal to or greater than the boundary value according to the operating state.

  In the sub-chamber internal combustion engine according to the present invention, the check valve can be changed from the closed state to the open state by setting the difference between the fuel pressure and the combustion chamber pressure to a boundary value or more according to the operating state. it can. For this reason, it is possible to supply an appropriate amount of fuel to the auxiliary combustion chamber according to the operating state.

<First Embodiment>
FIG. 1 shows a cross-sectional view of the sub-chamber internal combustion engine according to the first embodiment of the present invention.

(Schematic configuration of sub-chamber internal combustion engine)
The sub-chamber internal combustion engine 1 mainly includes a main combustion chamber 63, an intake / exhaust mechanism, a fuel injection valve 27, a reformed fuel supply mechanism (fuel supply unit) 30, a sub-combustion chamber 61, a spark plug 70, and a variable valve timing mechanism 81. , 82 and an ECU (control unit) 40.

  The main combustion chamber 63 is a chamber surrounded by the cylinder head 20, the cylinder block 10 and the piston 3. The cylinder head 20 is formed with an intake port 23 for supplying fresh air mixture 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, the intake collector 92 and the intake manifold 91 are located upstream of the intake port 23. The intake collector 92 is provided with a throttle valve 93a and a throttle drive device 93b on the upstream side. An intake valve 21 is disposed downstream of the intake port 23, and an exhaust valve 22 is disposed upstream of 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 injects main chamber fuel into the intake port 23. Here, the main chamber fuel is a fuel to be supplied to the main combustion chamber 63 without passing through the auxiliary combustion chamber 61, and is a gasoline fuel (liquid fuel). A fuel pump 25 that sends fuel to the fuel injection valve 27 via the fuel pipe 29 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 cylinder head 20, a sub-combustion chamber wall 61 a having a substantially cylindrical shape is disposed in a space formed between the intake port 23 and the exhaust port 24. 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. Thereby, the pressure of the main combustion chamber 63 and the pressure of the sub-combustion chamber 61 become substantially the same value (hereinafter referred to as P). The spark plug 70 is provided such that its tip projects into the auxiliary combustion chamber 61.

  The fuel reformer 31 of the reformed fuel supply mechanism 30 is a device that generates sub-chamber fuel. Here, the sub-chamber fuel is a fuel to be supplied to the sub-combustion chamber 61 without passing through the main combustion chamber 63, and is a gaseous fuel in which the combustibility of gasoline fuel (liquid fuel) is reformed. The fuel reformer 31 is connected to a check valve 33 via a reformed fuel first pipe 32. The check valve 33 is connected to the reformed fuel injection port 35 via the reformed fuel second pipe 34. The reformed fuel injection port 35 is formed in the auxiliary combustion chamber wall 61a.

  The variable valve timing mechanisms 81 and 82 are hydraulically driven, and the opening and closing timings of the intake valve 21 and the exhaust valve 22 are advanced or delayed by changing the phase and lift amount of the camshafts 21b and 22b with respect to the crankshaft. Keratinize. Here, the variable valve timing mechanisms 81 and 82 independently change the timing at which the intake valve 21 opens and the timing at which the intake valve 21 closes. Since the specific configuration of the variable valve timing mechanisms 81 and 82 is well known, the description thereof is omitted here.

  The ECU 40 is electrically connected to the fuel injection valve 27, the fuel pump 25, the fuel reforming device 31, the spark plug 70, the variable valve timing mechanisms 81 and 82, the throttle driving device 93b, and the like.

(Schematic operation of sub-chamber internal combustion engine)
In the sub-chamber internal combustion engine 1, the fuel pressurized by the fuel pump 25 is supplied to the fuel injection valve 27 through the fuel pipe 29 in the intake stroke. The fuel injection valve 27 injects fuel into fresh air introduced into the intake port 23 via the intake collector 92 and the intake manifold 91. Thereby, a fresh air mixture is generated. In the intake stroke, the intake valve 21 is opened by the intake cam 21 a, and the fresh air mixture is introduced into the main combustion chamber 63 from the intake port 23. Here, when the pressure P of the main combustion chamber 63 becomes equal to or lower than the boundary pressure Pc (see FIG. 4), the reformed fuel supply mechanism 30 supplies the sub-chamber fuel to the sub-combustion chamber 61. The boundary pressure Pc is a pressure at which a difference from the sub-chamber fuel pressure Pe becomes a boundary value B.

  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.

  By the spark plug 70, the fuel in the auxiliary combustion chamber 61 is ignited and burned at a predetermined timing. Here, the fuel in the sub-combustion chamber 61 is the fuel and the sub-chamber fuel contained in the fresh air mixture when the sub-chamber fuel is supplied, and is contained in the fresh air mixture when the sub-chamber fuel is not supplied. Fuel. 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 exhaust valve 22 is opened by the exhaust cam 22a, and the burned gas combusted in the main combustion chamber 63 is discharged to the exhaust port 24 as exhaust gas.

  The ECU 40 performs various controls by supplying control signals to the fuel injection valve 27, the fuel pump 25, the fuel reformer 31, the spark plug 70, the variable valve timing mechanisms 81 and 82, the throttle drive device 93b, and the like. . The ECU 40 executes logic for performing various controls. For example, the ECU 40 executes predetermined logic in an electric circuit, software, or both.

(Detailed configuration of reformed fuel supply mechanism)
The reformed fuel supply mechanism 30 mainly includes a fuel reformer 31, a reformed fuel first pipe 32, a check valve 33, a reformed fuel second pipe 34, and a reformed fuel injection port 35.

  The fuel reformer 31 generates sub chamber fuel. Specifically, the fuel reformer 31 oxidizes gasoline fuel by a catalytic reaction to produce reformed gas (sub-chamber fuel) centered on hydrogen and carbon monoxide. Among the sub-chamber fuels, carbon monoxide does not particularly affect flammability, but hydrogen is more flammable than gasoline fuel. That is, the fuel reformer 31 reforms the combustibility of gasoline fuel to generate subchamber fuel.

  The fuel reformer 31 is connected to a check valve 33 via a reformed fuel first pipe 32. The reformed fuel first pipe 32 is filled with the subchamber fuel generated by the fuel reformer 31. The check valve 33 is configured by holding a ball with a predetermined force by a spring. The check valve 33 is opened when the differential pressure is equal to or higher than the boundary value B (see “Main Combustion Chamber Pressure” shown in FIG. 4), and when the differential pressure is less than the boundary value B (the main pressure shown in FIG. 3). (See Combustion chamber pressure). Here, the differential pressure is the difference between the sub-chamber fuel pressure Pe in the reformed fuel first pipe 32 and the gas pressure in the reformed fuel second pipe 34, that is, the sub-chamber fuel pressure Pe and the sub-combustion chamber. This is the difference from the pressure P of 61.

  The check valve 33 is connected to the reformed fuel injection port 35 via the reformed fuel second pipe 34. The reformed fuel injection port 35 is formed in the auxiliary combustion chamber wall 61 a and communicates the reformed fuel second pipe 34 and the auxiliary combustion chamber 61. Thereby, when the check valve 33 is in the closed state, the pressure P in the sub-combustion chamber 61 and the gas pressure in the reformed fuel second pipe 34 become substantially the same pressure.

(Detailed operation of reformed fuel supply mechanism)
The fuel reformer 31 receives a control signal from the ECU 40, reforms the combustibility of gasoline fuel, and generates sub-chamber fuel. The sub chamber fuel is supplied to the check valve 33 via the reformed fuel first pipe 32.

  When the pressure P of the main combustion chamber 63 exceeds the boundary pressure Pc (see FIG. 3), the pressure P of the sub-combustion chamber 61 also exceeds the boundary pressure Pc, and the sub-chamber fuel pressure Pe and the sub-combustion chamber 61 The difference from the pressure P is less than the boundary value B. That is, since the differential pressure is less than the boundary value B, the check valve 33 is closed. When the check valve 33 is closed, the sub chamber fuel is not supplied before the check valve 33 and is not supplied to the sub combustion chamber 61.

  When the pressure P of the main combustion chamber 63 is equal to or lower than the boundary pressure Pc (see FIG. 4), the pressure P of the sub-combustion chamber 61 is also equal to or lower than the boundary pressure Pc, and the pressure Pe of the sub-chamber fuel and the pressure P of the sub-combustion chamber 61 The difference between and is the boundary value B or more. That is, since the differential pressure is greater than or equal to the boundary value B, the check valve 33 is open. When the check valve 33 is in the open state, the sub chamber fuel is supplied to the sub combustion chamber 61 via the check valve 33, the reformed fuel second pipe 34 and the reformed fuel injection port 35.

(Detailed configuration and detailed operation of the check valve 33)
The detailed configuration and detailed operation of the check valve 33 are shown in FIG. The check valve 33 mainly includes a valve body 33c, a ball 33a, and a spring 33b. A pressure Pe of the sub chamber fuel is applied to the valve body 33c from the upstream side through the reformed fuel first pipe 32. A pressure P (= F / A) obtained by dividing the pressure P of the auxiliary combustion chamber 61 and the force F received from the spring 33b by the contact area A is applied to the ball. Here, the condition that the check valve 33 is opened is as follows.
P + B ≦ Pe (1)
It is. When the condition of Formula (1) is expressed by differential pressure (Pe-P),
B ≦ Pe−P (2)
It becomes. That is, the pressure B (= F / A) obtained by dividing the force F received from the spring 33b by the contact area A corresponds to the boundary value described above. The boundary pressure Pc is a pressure at which the difference from the sub-chamber fuel pressure Pe becomes the boundary value B.
Pc = Pe-B (3)
It is expressed. From the equations (2) and (3), the condition for the check valve 33 to be open is
P ≦ Pc
It can be rewritten as That is, when the pressure P of the main combustion chamber 63 is equal to or lower than the boundary pressure Pc, it is guided that the check valve 33 is opened.

(Detailed configuration of ECU)
The ECU 40 mainly includes a load calculation unit 41, a fuel injection control unit 42, a throttle control unit 43, a valve timing control unit 44, an ignition timing control unit 45, a storage unit (not shown), and an input / output interface (not shown). Prepare. The load calculation unit 41, the fuel injection control unit 42, the throttle control unit 43, and the valve timing control unit 44 are a CPU or the like. The storage unit is a ROM, a RAM, or the like, and stores programs, intake valve opening timing information (see FIG. 2), and the like. The input / output interface is a portion that becomes an interface when receiving a signal from the outside or supplying a signal to the outside.

  The ECU 40 not only executes logic for performing various controls, but also executes logic for controlling the opening / closing timing of the intake valve 21.

(Detailed operation of ECU)
A crank angle signal detected by the crank angle sensor 51, a coolant temperature signal detected by the water temperature sensor 52, an accelerator opening signal detected by the accelerator opening sensor 53, and the like are input to the ECU 40 via an input / output interface. Is done. The load calculation unit 41 receives these signals from the input / output interface. The load calculation unit 41 calculates the engine load based on these signals.

  The fuel injection control unit 42 receives engine load information from the load calculation unit 41 and generates an injection amount control signal based on the engine load information and the like. Thus, the fuel injection valve 27 injects fuel at a predetermined injection amount based on the injection amount control signal.

  The throttle control unit 43 receives engine load information from the load calculation unit 41 and generates a throttle control signal based on the engine load information and the like. Thereby, the throttle drive device 93b opens and closes the throttle valve 93a at a predetermined opening based on the throttle control signal.

  The valve timing control unit 44 receives engine load information from the load calculation unit 41. Further, the valve timing control unit 44 refers to the storage unit and receives intake valve opening timing information (see FIG. 2) from the storage unit. The valve timing control unit 44 generates a valve timing control signal based on engine load information, intake valve opening timing information (see FIG. 2), and the like. Thereby, the variable valve timing mechanisms 81 and 82 open and close the intake valve 21 and the exhaust valve 22 at a predetermined timing based on the valve timing control signal. That is, the ECU 40 controls the pressure P in the main combustion chamber 63 by controlling the timing at which the intake valve 21 opens.

  The ignition timing control unit 45 receives engine load information from the load calculation unit 41, and generates an ignition timing control signal based on the engine load information and the like. Thereby, the spark plug 70 generates a spark at a predetermined timing based on the ignition timing control signal.

(Control of sub-chamber internal combustion engine)
Control of the sub-chamber internal combustion engine 1 will be described with reference to FIGS. 3 and 4, “the pressure P of the main combustion chamber” and “the flow rate of the sub chamber fuel” are shown only in the intake stroke.

  Intake valve opening timing information referred to by the valve timing control unit 44 of the ECU 40 is shown in FIG. The intake valve opening timing information indicates the relationship between the opening timing of the intake valve 21 and the engine load. That is, the valve timing control unit 44 generates the valve timing control signal so that the timing at which the intake valve 21 opens is delayed as the engine load is reduced. The variable valve timing mechanism 81 receives a valve timing control signal from the valve timing control unit 44. Based on the valve timing control signal, the variable valve timing mechanism 81 retards the timing at which the intake valve 21 opens as the engine load decreases.

  FIG. 3 shows the relationship between the valve lift, the pressure in the main combustion chamber, the flow rate of the sub chamber fuel, and the crank angle (CA) during high load operation. Here, “valve lift” is the amount by which the intake valve 21 or the exhaust valve 22 is lifted, and is indicated by a one-dot chain line for the intake valve 21 and by a solid line for the exhaust valve 22. The “pressure in the main combustion chamber” is the pressure of the fresh air mixture in the main combustion chamber 63. The “sub-chamber fuel flow rate” is a flow rate at which the sub-chamber fuel supplied to the sub-combustion chamber 61 passes through the reformed fuel injection port 35 per unit time. During high-load operation, the opening timing of the intake valve 21 is not retarded and is close to normal. That is, the intake valve 21 starts to open at a timing slightly before the top dead center (TDC) and closes at a timing after the bottom dead center (BDC). Thereby, the pressure P of the main combustion chamber 63 in the intake stroke is temporarily lower than the pressure Po in the standard state (negative pressure is generated), but exceeds the boundary pressure Pc. When the pressure P of the main combustion chamber 63 exceeds the boundary pressure Pc, the check valve 33 is closed as described above, and the sub chamber fuel is not supplied before the check valve 33, and the sub combustion is performed. It is not supplied to the chamber 61 (see the sub-chamber fuel flow rate).

  FIG. 4 shows the relationship between the valve lift, the pressure in the main combustion chamber, the flow rate of the sub chamber fuel, and the crank angle (CA) during low load operation. During low-load operation, the timing (IVO) at which the intake valve 21 opens is delayed to a timing later than the top dead center (TDC), and is later than the timing (EVC) at which the exhaust valve 22 is closed. That is, the intake valve 21 starts to open at a timing slightly later than the timing (EVC) when the exhaust valve 22 is closed, and closes at a timing after the bottom dead center (BDC). Thereby, the pressure P of the main combustion chamber 63 in the intake stroke is temporarily lower than the pressure Po in the standard state (negative pressure is generated), and becomes equal to or lower than the boundary pressure Pc. When the pressure P of the main combustion chamber 63 is equal to or lower than the boundary pressure Pc, as described above, the check valve 33 is in an open state, and the sub-chamber fuel is improved with the check valve 33 and the reformed fuel second pipe 34. It is supplied to the auxiliary combustion chamber 61 via the quality fuel injection port 35 (see the flow rate of the auxiliary chamber fuel). For comparison, the valve lift of the intake valve 21 during high load operation is indicated by a two-dot chain line.

  FIG. 5 is a flowchart showing a control flow in the sub-chamber internal combustion engine 1. Such control is performed together with other controls in the sub-chamber internal combustion engine 1.

  In step S1, detection by a sensor is performed. That is, detection is performed by the crank angle sensor 51, the water temperature sensor 52, the accelerator opening sensor 53, and the like. A crank angle signal detected by the crank angle sensor 51, a coolant temperature signal detected by the water temperature sensor 52, an accelerator opening signal detected by the accelerator opening sensor 53, and the like are input to the ECU 40 via an input / output interface. Is done.

  In step S2, the operating state is calculated. That is, the load calculation unit 41 receives the signal input in step S1 from the input / output interface. The load calculation unit 41 calculates the engine load based on these signals.

  In step S3, the intake valve opening timing information is referred to. That is, the valve timing control unit 44 receives engine load information from the load calculation unit 41. Further, the valve timing control unit 44 refers to the storage unit and receives intake valve opening timing information (see FIG. 2) from the storage unit.

  In step S4, the timing for opening the intake valve 21 is controlled. That is, the valve timing control unit 44 generates a valve timing control signal based on engine load information, intake valve opening timing information, and the like. Thereby, the variable valve timing mechanisms 81 and 82 open and close the intake valve 21 and the exhaust valve 22 at a predetermined timing based on the valve timing control signal. For example, during high load operation, the variable valve timing mechanism 81 is controlled so that the intake valve 21 opens at a timing close to normal. During low load operation, the variable valve timing mechanism 81 is controlled so that the intake valve 21 opens at a retarded timing such that the pressure P of the main combustion chamber 63 becomes equal to or lower than the boundary pressure Pc. That is, the ECU 40 delays the opening timing of the intake valve 21 so that the pressure P of the main combustion chamber 63 becomes smaller than the boundary chamber fuel pressure Pe by the boundary value B or more according to the operating state. Thereby, the sub chamber fuel is not supplied to the sub combustion chamber 61 during the high load operation, but the sub chamber fuel is supplied to the sub combustion chamber 61 during the low load operation. Here, as shown in FIG. 2, the timing at which the intake valve 21 opens is delayed as the operating state becomes lower, so the ECU 40 determines that the pressure P in the main combustion chamber 63 is the boundary pressure Pc during low-load operation. Control is performed so that the following time becomes longer than that during high-load operation.

  In step S5, the ECU 40 determines whether or not a predetermined period has elapsed. If it is determined that the predetermined period has elapsed, the process proceeds to step S1, and if it is determined that the predetermined period has not elapsed, the process proceeds to step S5. Thereby, the process of step S1-S4 is repeated for every predetermined period.

(Characteristics of sub-chamber internal combustion engine)
(1)
Here, the ECU 40 performs control so that the pressure P in the main combustion chamber 63 is smaller than the boundary value B by the pressure Pe of the sub-chamber fuel according to the operating state. Specifically, the ECU 40 retards the opening timing of the intake valve 21 during low load operation compared to during high load operation. When the pressure P of the main combustion chamber 63 is made lower than the boundary pressure Pc, the pressure P of the main combustion chamber 63 becomes lower than the boundary value B by the pressure Pe of the sub chamber fuel, and the pressure P of the sub combustion chamber 61 is also the sub chamber fuel. The boundary value B is smaller than the pressure Pe. Thereby, the differential pressure of the check valve 33 becomes equal to or higher than the boundary value B.

  Thus, since the differential pressure of the check valve 33 becomes equal to or higher than the boundary value B according to the operating state, the check valve 33 changes from the closed state to the open state according to the operating state. For this reason, an appropriate amount of sub-chamber fuel is supplied to the sub-combustion chamber 61 according to the operating state.

(2)
Here, the ECU 40 retards the timing at which the intake valve 21 opens until a timing later than the timing at which the exhaust valve 22 in the main combustion chamber 63 is closed (EVC shown in FIG. 4). Since both the exhaust valve 22 and the intake valve 21 are closed from the timing when the exhaust valve 22 is closed to the timing when the intake valve 21 is opened, the pressure P in the main combustion chamber 63 is significantly lower than the pressure Po in the standard state. (A large negative pressure is generated.)

  Thus, since the pressure P in the main combustion chamber 63 is significantly lower than the pressure Po in the standard state, it is ensured that the pressure P in the main combustion chamber 63 is lower than the boundary value B by the sub-chamber fuel pressure Pe. Controlled.

(3)
Here, the variable valve timing mechanisms 81 and 82 independently change the timing when the intake valve 21 opens and the timing when the intake valve 22 closes. That is, as shown in FIG. 4, the variable valve timing mechanism 81 retards the opening timing of the intake valve 21 during low load operation compared to during high load operation, but the timing when the intake valve 21 closes during high load operation. It is unchanged compared to the time.

  As described above, the timing at which the intake valve 21 opens during the low load operation is retarded as compared with that during the high load operation, but the timing at which the intake valve 21 closes is unchanged compared to during the high load operation. The pressure P is easily controlled so as to be smaller than the boundary value B by the sub-chamber fuel pressure Pe. Further, the reduction in the effective compression ratio of the engine is suppressed by the fact that the timing at which the intake valve 21 is closed is unchanged. Furthermore, when the operating state changes, the opening / closing timing of the intake valve 21 is quickly switched.

(4)
Here, the ECU 40 retards the timing at which the intake valve 21 opens as the operating state becomes lower in load. That is, the ECU 40 performs control so that the time during which the pressure P of the main combustion chamber 63 is equal to or lower than the boundary pressure Pc is longer during low load operation than during high load operation. As a result, the time during which the differential pressure of the check valve 33 is greater than or equal to the boundary value B during low load operation is longer than during high load operation.

  As described above, since the time during which the differential pressure of the check valve 33 exceeds the boundary value B during low load operation is longer than during high load operation, the sub-chamber fuel during low load operation is greater than during high load operation. A large amount is supplied to the auxiliary combustion chamber 61. For this reason, during the low load operation, the amount of sub-chamber fuel supplied to the sub-combustion chamber 61 increases, so the ignitability of the sub-combustion chamber 61 is improved. In addition, since the amount of sub-chamber fuel supplied to the sub-combustion chamber 61 is suppressed during high load operation, the intensity of the flame radiated from the sub-combustion chamber 61 to the main combustion chamber 63 is suppressed, The decrease in thermal efficiency is suppressed.

(5)
Here, the sub-chamber fuel is a gaseous fuel in which the combustibility of gasoline fuel (liquid fuel) is reformed. Thereby, the combustion speed (laminar flame propagation speed) of the fuel after ignition in the auxiliary combustion chamber 61 is improved.

  Thus, since the combustion speed in the auxiliary combustion chamber 61 is improved, the combustion gas (flame) radiated from the auxiliary combustion chamber 61 to the main combustion chamber 63 via the communication passage 61b becomes strong. For this reason, the combustion speed in the main combustion chamber 63 is also improved. Thus, even when a large amount of EGR (Exhaust Gas Recirculation) is performed or when the air-fuel ratio of the fresh air mixture in the main combustion chamber 63 is lean, the combustion in the main combustion chamber 63 is maintained well.

(Modification of the first embodiment)
(A) The ECU 40 may advance the timing at which the intake valve 21 is closed instead of delaying the timing at which the intake valve 21 is opened. That is, the ECU 40 controls the variable valve timing mechanisms 81 and 82, and the intake valve 21 is controlled so that the pressure P of the main combustion chamber 63 becomes smaller than the boundary value B by the sub-chamber fuel pressure Pe according to the operating state. Advance the closing timing. For example, during high load operation, the ECU 40 controls the variable valve timing mechanism 81 so that the intake valve 21 is closed at a timing close to normal as shown in FIG. As shown in FIG. 6, during low load operation, the ECU 40 adjusts the variable valve timing mechanism 81 so that the intake valve 21 is closed at a timing at which the pressure P of the main combustion chamber 63 is advanced so as to be equal to or lower than the boundary pressure Pc. To control. That is, the ECU 40 sets the timing at which the intake valve 21 is closed from the bottom dead center (BDC) so that the pressure P of the main combustion chamber 63 becomes smaller than the boundary value B by the pressure P of the sub-chamber fuel according to the operating state. Advance to early timing. Specifically, the ECU 40 advances the timing at which the intake valve 21 closes during low load operation compared to during high load operation. Thereby, the pressure P of the main combustion chamber 63 is set to be equal to or lower than the boundary pressure Pc according to the operating state, and the differential pressure of the check valve 33 becomes equal to or higher than the boundary value B.

  Thus, since the differential pressure of the check valve 33 becomes equal to or higher than the boundary value B according to the operating state, the check valve 33 changes from the closed state to the open state according to the operating state.

  Here, as shown in FIG. 6, the ECU 40 does not change the timing at which the intake valve 21 opens regardless of the operating state. For this reason, the valve overlap is almost unchanged regardless of the operating state, the increase in the residual gas ratio is prevented, and the deterioration of the combustibility of the main combustion chamber 63 is avoided.

  In FIG. 6, “the pressure P of the main combustion chamber” and “the flow rate of the sub chamber fuel” are shown only in the intake stroke.

  (B) In the variable valve timing mechanism 81, when the operating angle of the intake valve 21 is reduced, the lift of the intake valve 21 may be reduced. At this time, when the operating angle of the intake valve 21 is reduced, the drive loss of the intake valve 21 is reduced. Further, when the operating angle of the intake valve 21 is reduced, the intake air flow velocity of the fresh air mixture from the intake port 23 to the main combustion chamber 63 is increased, so that mixing of air and fuel in the fresh air mixture is promoted. The combustion in the main combustion chamber 63 is good.

  The sub-chamber internal combustion engine 1 may employ a variable valve timing mechanism that changes the angular velocity of the camshaft relative to the crankshaft instead of the hydraulically driven variable valve timing mechanisms 81 and 82. For example, a variable valve timing device disclosed in Japanese Patent Laid-Open No. 2001-073819 can be employed. In this case, the ECU 40 controls the variable valve timing device so that the opening timing of the intake valve 21 during low load operation (one-dot chain line in FIG. 7) is the same as during high load operation (two-dot chain line in FIG. 7). Although the timing is retarded, the timing at which the intake valve 21 is closed is made unchanged compared to during high-load operation. For this reason, the pressure P of the main combustion chamber 63 is made not more than the boundary pressure Pc according to the operating state, and the differential pressure of the check valve 33 becomes not less than the boundary value B, so that the check valve 33 is closed according to the operating state. Change from state to open state. In FIG. 7, “the pressure P of the main combustion chamber” and “the flow rate of the sub chamber fuel” are shown only in the intake stroke.

  Alternatively, a variable valve timing mechanism that changes the phase of the cam shaft with respect 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. In this case, the ECU 40 controls the variable valve timing device so that the opening timing of the intake valve 21 during low load operation (one-dot chain line in FIG. 8) is the same as during high load operation (two-dot chain line in FIG. 8). The timing at which the intake valve 21 is closed is also retarded as compared to during high-load operation. For this reason, the pressure P of the main combustion chamber 63 is made not more than the boundary pressure Pc according to the operating state, and the differential pressure of the check valve 33 becomes not less than the boundary value B, so that the check valve 33 is closed according to the operating state. Change from state to open state. In FIG. 8, “the pressure P of the main combustion chamber” and “the flow rate of the sub chamber fuel” are shown only in the intake stroke.

  Alternatively, other types of variable valve timing mechanisms may be employed.

  (C) The sub-chamber fuel supplied to the check valve 33 may be vaporized gasoline fuel (liquid fuel) instead of reformed gasoline fuel (liquid fuel). In this case, gasoline fuel (liquid fuel) is supplied from the fuel pump 25 to a mechanism that vaporizes using waste heat or the like of the sub-chamber internal combustion engine 1, and the gasoline fuel vaporized in the mechanism is checked as sub-chamber fuel. It may be supplied to the valve 33.

  Alternatively, the sub chamber fuel supplied to the check valve 33 may be gas fuel. In this case, the sub chamber fuel may be supplied to the check valve 33 from a gas fuel tank or the like.

  Alternatively, the sub chamber fuel supplied to the check valve 33 may be a fresh air mixture. In this case, compared with the case where only the fuel is supplied to the auxiliary combustion chamber 61, the air-fuel ratio of the auxiliary combustion chamber 61 can be avoided from becoming excessively rich.

  (D) The fuel injection valve 27 may inject fuel directly into the main combustion chamber 63 instead of injecting fuel into the intake port 23.

  In step S2 shown in FIG. 5, it is preferable that the engine load is calculated. However, other operating states (for example, the engine speed) may be calculated instead of or in addition to the engine load.

  (E) In order to control the differential pressure of the check valve 33, the pressure Pe of the sub chamber fuel in the reformed fuel first pipe 32 is controlled instead of controlling the pressure P of the main combustion chamber 63 as in the present invention. It is also possible to do. However, the sub chamber fuel in the reformed fuel first pipe 32 is not pressurized. Then, controlling the pressure Pe of the sub chamber fuel in the reformed fuel first pipe 32 tends to make it difficult to control the differential pressure of the check valve 33. In addition, it is conceivable to arrange a device for changing the pressure Pe of the sub-chamber fuel in the fuel reformer 31 or the reformed fuel first pipe 32, but the structure may be more complicated than necessary.

  In contrast to these configurations, the sub-chamber internal combustion engine 1 according to the present invention does not need to control the pressure Pe of the sub-chamber fuel in the reformed fuel first pipe 32, so that the sub-chamber fuel does not need to be pressurized. The differential pressure of the check valve 33 can be controlled, and the structure is not complicated more than necessary.

Second Embodiment
FIG. 9 shows a cross-sectional view of the sub-chamber internal combustion engine according to the second embodiment of the present invention.

  The sub-chamber internal combustion engine 100 has the same basic configuration as that of the first embodiment, but further includes an intake control valve 128a and an intake control drive device (intake control valve opening / closing mechanism) 128b, and the ECU 140 performs intake control. The second embodiment is different from the first embodiment in that the valve controller 146 is further provided. The intake control valve 128 a and the intake control drive device 128 b are disposed in the intake manifold 91 between the intake collector 92 and the intake port 23. The storage unit of the ECU 140 stores intake control valve opening timing information (see FIG. 10) instead of intake valve opening timing information (see FIG. 2).

  The intake control valve control unit 146 of the ECU 140 receives engine load information from the load calculation unit 41. The intake control valve control unit 146 refers to the storage unit, and acquires intake control valve opening timing information (see FIG. 10) from the storage unit. The intake control valve control unit 146 generates an intake control valve control signal based on engine load information, intake control valve opening timing information, and the like. The intake control drive device 128b receives the intake control valve control signal from the intake control valve control unit 146, and controls the open / close state of the intake control valve 128a based on the intake control valve control signal.

(Control of sub-chamber internal combustion engine)
Control of the sub-chamber internal combustion engine 100 will be described with reference to FIGS.

  FIG. 10 shows intake control valve opening timing information referred to by the intake control valve control unit 146 of the ECU 140. The intake control valve opening timing information indicates the relationship between the opening timing of the intake control valve 128a and the engine load. That is, the intake control valve control unit 146 generates the intake control valve control signal so that the timing at which the intake control valve 128a opens is delayed as the engine load is reduced. The intake control driving device 128b receives the intake control valve control signal from the intake control valve control unit 146. The intake control drive device 128b retards the opening timing of the intake control valve 128a as the engine load decreases based on the intake control valve control signal.

  FIG. 11 shows the relationship between the valve lift, intake control valve state, intake port pressure, main combustion chamber pressure, sub-chamber fuel flow rate, and crank angle (CA) during high load operation. Here, “valve lift” is the amount by which the intake valve 21 or the exhaust valve 22 is lifted, and is indicated by a one-dot chain line for the intake valve 21 and by a solid line for the exhaust valve 22. “The state of the intake control valve” is an open / close state of the intake control valve 128a. The “intake port pressure” is the pressure on the downstream side of the intake control valve 128 a in the intake port 23. The “pressure in the main combustion chamber” is the pressure of the fresh air mixture in the main combustion chamber 63. The “sub-chamber fuel flow rate” is a flow rate at which the sub-chamber fuel supplied to the sub-combustion chamber 61 passes through the reformed fuel injection port 35 per unit time. During high-load operation, the opening timing of the intake control valve 128a becomes almost normal with almost no delay. That is, the intake control valve 128a closes at the timing of CA1 and opens at the timing of CA2. Thereby, the pressure (intake port pressure) on the downstream side of the intake control valve 128a in the intake stroke temporarily becomes lower than the pressure Po in the standard state. The pressure P in the main combustion chamber 63 is temporarily lower than the pressure Po in the standard state (negative pressure is generated), but exceeds the boundary pressure Pc. When the pressure P of the main combustion chamber 63 exceeds the boundary pressure Pc, the check valve 33 is closed as described above, and the sub chamber fuel is not supplied before the check valve 33, and the sub combustion is performed. It is not supplied to the chamber 61 (see the sub-chamber fuel flow rate). In FIG. 11, “the pressure P of the main combustion chamber” and “the flow rate of the sub chamber fuel” are shown only in the intake stroke.

  FIG. 12 shows the relationship between the valve lift, the state of the intake control valve, the intake port pressure, the pressure in the main combustion chamber, the flow rate of the sub chamber fuel, and the crank angle (CA) during low load operation. During low-load operation, the timing for opening the intake control valve 128a is retarded. That is, the intake control valve 128a is closed at the timing of CA1, and is opened at the timing of CA3 delayed from CA2. Thereby, the pressure of the intake port 23 in the intake stroke is temporarily lower than the pressure Po in the standard state. Then, the pressure P of the main combustion chamber 63 in the intake stroke is temporarily lower than the pressure Po in the standard state (a negative pressure is generated), and becomes equal to or lower than the boundary pressure Pc. When the pressure P of the main combustion chamber 63 is equal to or lower than the boundary pressure Pc, as described above, the check valve 33 is in an open state, and the sub-chamber fuel is improved with the check valve 33 and the reformed fuel second pipe 34. It is supplied to the auxiliary combustion chamber 61 via the quality fuel injection port 35 (see the flow rate of the auxiliary chamber fuel). For comparison, the state of the intake control valve 128a during high load operation is indicated by a two-dot chain line. In FIG. 12, “the pressure P of the main combustion chamber” and “the flow rate of the sub chamber fuel” are shown only in the intake stroke.

  When the high load operation and the low load operation are compared, the ECU 140 retards the opening timing of the intake control valve 128a in the low load operation compared to the high load operation. Thus, the first period during which the intake control valve 128a is closed in the intake stroke is longer in the low load operation than in the high load operation. That is, the ECU 140 performs control so that the first period is longer in the low load operation than in the high load operation. As a result, the time during which the pressure P of the main combustion chamber 63 is equal to or lower than the boundary pressure Pc during low-load operation is longer than during high-load operation.

(Characteristics of sub-chamber internal combustion engine)
(1)
Here, the ECU 140 controls the intake control drive device 128b to take in the intake stroke so that the pressure P in the main combustion chamber 63 becomes smaller than the boundary value B by the sub-chamber fuel pressure Pe according to the operating state. The control valve 128a is closed for the first period. Specifically, the ECU 140 retards the opening timing of the intake valve 21 during low load operation compared to during high load operation. When the pressure P of the main combustion chamber 63 is made lower than the boundary pressure Pc, the pressure P of the auxiliary combustion chamber 61 is also made lower than the boundary pressure Pc. Thereby, the differential pressure of the check valve 33 becomes equal to or higher than the boundary value B according to the operating state.

  Thus, since the differential pressure of the check valve 33 becomes equal to or higher than the boundary value B according to the operating state, the check valve 33 changes from the closed state to the open state according to the operating state. For this reason, an appropriate amount of sub-chamber fuel is supplied to the sub-combustion chamber 61 according to the operating state.

(2)
Here, the ECU 140 delays the timing at which the intake control valve 128a opens as the operating state becomes lower. That is, the ECU 140 performs control so that the first period is longer in the low load operation than in the high load operation. As a result, the time during which the pressure P of the main combustion chamber 63 is equal to or lower than the boundary pressure Pc during low-load operation is longer than during high-load operation. For this reason, the time during which the differential pressure of the check valve 33 is greater than or equal to the boundary value B during low load operation is longer than during high load operation.

  As described above, since the time during which the differential pressure of the check valve 33 exceeds the boundary value B during low load operation is longer than during high load operation, the sub-chamber fuel during low load operation is greater than during high load operation. A large amount is supplied to the auxiliary combustion chamber 61. For this reason, during the low load operation, the amount of sub-chamber fuel supplied to the sub-combustion chamber 61 increases, so the ignitability of the sub-combustion chamber 61 is improved. In addition, since the amount of sub-chamber fuel supplied to the sub-combustion chamber 61 is suppressed during high load operation, the intensity of the flame radiated from the sub-combustion chamber 61 to the main combustion chamber 63 is suppressed, The decrease in thermal efficiency is suppressed.

(3)
Here, the sub-chamber fuel is a gaseous fuel in which the combustibility of gasoline fuel (liquid fuel) is reformed. Thereby, the combustion speed (laminar flame propagation speed) of the fuel after ignition in the auxiliary combustion chamber 61 is improved.

  Thus, since the combustion speed in the auxiliary combustion chamber 61 is improved, the combustion gas (flame) radiated from the auxiliary combustion chamber 61 to the main combustion chamber 63 via the communication passage 61b becomes strong. For this reason, the combustion speed in the main combustion chamber 63 is also improved. Thus, even when a large amount of EGR (Exhaust Gas Recirculation) is performed or when the air-fuel ratio of the fresh air mixture in the main combustion chamber 63 is lean, the combustion in the main combustion chamber 63 is maintained well.

  The sub-chamber internal combustion engine according to the present invention has an effect that an appropriate amount of sub-chamber fuel can be supplied to the sub-combustion chamber according to the operating state, and is useful as a sub-chamber internal combustion engine or the like.

1 is a cross-sectional view of a sub-chamber internal combustion engine according to a first embodiment of the present invention. The figure which shows the intake valve opening timing information in 1st Embodiment. The figure which shows the relationship between the valve lift at the time of high load driving | operation in 1st Embodiment, the pressure of a main combustion chamber, the flow volume of a subchamber fuel, and a crank angle. The figure which shows the relationship between the valve lift at the time of low load driving | operation in 1st Embodiment, the pressure of a main combustion chamber, the flow volume of a subchamber fuel, and a crank angle. The flowchart which shows the flow of control in the subchamber internal combustion engine of 1st Embodiment. The figure which shows the relationship between the valve lift at the time of the low load driving | running in the modification of 1st Embodiment, the pressure of a main combustion chamber, the flow volume of a subchamber fuel, and a crank angle. The figure which shows the relationship between the valve lift at the time of the low load driving | running in the modification of 1st Embodiment, the pressure of a main combustion chamber, the flow volume of a subchamber fuel, and a crank angle. The figure which shows the relationship between the valve lift at the time of the low load driving | running in the modification of 1st Embodiment, the pressure of a main combustion chamber, the flow volume of a subchamber fuel, and a crank angle. Sectional drawing of the subchamber internal combustion engine which concerns on 2nd Embodiment of this invention. The figure which shows the intake control valve opening timing information in 2nd Embodiment. The figure which shows the relationship between the valve lift, the state of the intake control valve, the intake port pressure, the pressure of the main combustion chamber, the flow rate of the sub chamber fuel, and the crank angle during low load operation in the second embodiment. The figure which shows the relationship between the valve lift, the state of the intake control valve, the intake port pressure, the pressure of the main combustion chamber, the flow rate of the sub chamber fuel, and the crank angle during low load operation in the second embodiment. The figure which shows the structure and operation | movement of a check valve.

Explanation of symbols

1,100 Sub-chamber internal combustion engine 21 Intake valve 30 Reformed fuel supply mechanism (fuel supply unit)
31 Fuel reformer 32 First reformed fuel pipe 33 Check valve 34 Second reformed fuel pipe 35 Reformed fuel injection port 40, 140 ECU (control unit)
61 Sub Combustion Chamber 63 Main Combustion Chamber 70 Spark Plugs 81, 82 Variable Valve Timing Mechanism 128a Intake Control Valve 128b Intake Control Drive Device

Claims (13)

A combustion chamber having a main combustion chamber and a sub-combustion chamber communicating adjacent to the main combustion chamber;
A check that is open when the difference between the fuel pressure and the combustion chamber pressure is greater than or equal to a boundary value, and that is closed when the difference between the fuel pressure and the combustion chamber pressure is less than the boundary value. A fuel supply unit for supplying the fuel to the auxiliary combustion chamber via a valve;
A control unit for controlling a length of time during which the pressure in the combustion chamber is smaller than the fuel pressure by the boundary value or more according to an operating state;
With
Sub-chamber internal combustion engine. A variable valve timing mechanism for changing the opening and closing timing of the intake valve with respect to the main combustion chamber;
The control unit controls the variable valve timing mechanism so as to retard the opening timing of the intake valve so that the pressure in the combustion chamber is smaller than the fuel pressure by the boundary value according to the operating state. ,
The sub-chamber internal combustion engine according to claim 1. The control unit retards the opening timing of the intake valve during low load operation compared to during high load operation.
The sub-chamber internal combustion engine according to claim 2. The control unit retards the opening timing of the intake valve to a timing later than the closing timing of the exhaust valve for the main combustion chamber during low load operation.
The sub-chamber internal combustion engine according to claim 3. A variable valve timing mechanism for changing the opening and closing timing of the intake valve with respect to the main combustion chamber;
The control unit controls the variable valve timing mechanism to advance the timing at which the intake valve closes so that the pressure in the combustion chamber is smaller than the fuel pressure by the boundary value or more according to the operating state. ,
The sub-chamber internal combustion engine according to claim 1. The control unit advances the timing at which the intake valve closes during low load operation compared to during high load operation.
The sub-chamber internal combustion engine according to claim 5. The variable valve timing mechanism is capable of independently changing the timing at which the intake valve opens and the timing at which the intake valve closes.
The sub-chamber internal combustion engine according to any one of claims 2 to 6. An intake control valve opening / closing mechanism for opening / closing an intake control valve provided upstream of the intake valve;
The control unit controls the intake control valve opening / closing mechanism so that the pressure in the combustion chamber is smaller than the boundary value by the operating state, and the intake control valve is controlled in the intake stroke. Close for one period,
The sub-chamber internal combustion engine according to claim 1. The control unit retards the opening timing of the intake control valve so that the pressure in the combustion chamber is smaller than the fuel pressure by the boundary value or more according to the operating state.
The sub-chamber internal combustion engine according to claim 8. The control unit retards the opening timing of the intake control valve during low load operation compared to during high load operation.
The sub-chamber internal combustion engine according to claim 9. The control unit controls the first period according to an operating state.
The sub-chamber internal combustion engine according to any one of claims 8 to 10. The control unit controls the first period to be longer in the low load operation than in the high load operation.
The sub-chamber internal combustion engine according to claim 11. The fuel is a fuel with improved combustibility,
The sub-chamber internal combustion engine according to any one of claims 1 to 12.

Images