JP7831346B2 - Internal combustion engine - Google Patents

Description

This invention relates to an internal combustion engine.

In a sub-chamber type internal combustion engine, where a sub-chamber is provided within the main combustion chamber, a fuel-intake mixture is supplied to the sub-chamber and ignited by a spark plug. Once a flame is formed in the sub-chamber, this flame is injected into the main combustion chamber through multiple nozzles formed in the sub-chamber. The injected flame then ignites the fuel-intake mixture in the main combustion chamber. This achieves a good combustion state in the main combustion chamber (see, for example, Patent Document 1 below).

Japanese Patent Publication No. 2020-197203

In internal combustion engines with multiple nozzles in the sub-chamber, the flames propagating from each nozzle can collide, resulting in combustion accompanied by a shock similar to knocking (hereinafter referred to as jet shock). This jet shock is particularly pronounced when the air-fuel ratio of the mixture is stoichiometric compared to lean, because a larger amount of fuel spreads during combustion. Furthermore, jet shock and knocking are easily confused, which may pose a problem in terms of knock sensing capabilities. Additionally, in passive sub-chamber internal combustion engines where the mixture, mixed in the intake passage or main combustion chamber, is introduced into the sub-chamber, cycle fluctuations are likely to occur, where the size of the flames injected from each nozzle varies with each combustion cycle. This may pose a problem in terms of uniform ignition of the mixture in the main combustion chamber.

Therefore, this invention aims to achieve a stable combustion state in the main combustion chamber of a sub-chamber type internal combustion engine.

In order to solve the above problems, this invention provides:
A main combustion chamber comprising a cylinder head and piston,
A sub-chamber provided within the main combustion chamber,
The internal combustion engine is configured such that the sub-chamber is rotatably supported by the cylinder head around the axis of a shaft extending in the direction of movement of the piston.

In the above configuration,
Preferably, the sub-chamber has a main body having an outer surface facing the main combustion chamber and an inner surface facing the opposite side of the outer surface, and a nozzle is formed at a position radially outward from the center of the axis of the main body, penetrating the inner and outer surfaces of the main body and inclined at least in the circumferential direction with respect to the radial direction, and the sub-chamber is configured to rotate due to the outward injection pressure from the nozzle.

In all of the above configurations,
Preferably, the sub-chamber has a flange portion extending radially outward, and the cylinder head has a clamping portion that rotatably supports the flange portion and an oil reservoir portion in which oil is stored and a part of the flange portion is immersed.

In the configuration having the flange portion,
Preferably, a projection is formed around the periphery of the flange portion, extending axially and acting as a barrier to the radially outward flow of oil.

In the configuration having the flange portion,
Preferably, the flange portion is provided with a supply unit for supplying oil to the oil reservoir and a discharge unit for discharging oil from the oil reservoir, and with a plurality of fins that stand upright in the axial direction spaced apart in the circumferential direction.

In all of the above configurations,
It is preferable to provide a permanent magnet in the sub-chamber and an electromagnet in the cylinder head, and to configure the system so that rotational force is applied to the sub-chamber by energizing the electromagnet.

In this invention, in a pre-chamber type internal combustion engine, the pre-chamber is made rotatable around an axis extending in the direction of piston movement, and flames are ejected while rotating. This suppresses abnormal combustion accompanied by shocks caused by collisions between flame propagations, and also equalizes the cycle variation in the size of the flames ejected from each nozzle, thereby achieving a stable combustion state in the main combustion chamber.

This is a cross-sectional view showing the main part of the first embodiment of the internal combustion engine according to this invention. Figure 1 is a cross-sectional view of a sub-chamber used in an internal combustion engine. Figure 1 is a perspective view of a sub-chamber used in an internal combustion engine. This is a cross-sectional view showing the main part of a second embodiment of an internal combustion engine according to the present invention. Figure 4 is a cross-sectional view of a sub-chamber used in an internal combustion engine. Figure 4 is a perspective view of a sub-chamber used in an internal combustion engine. This is a schematic cross-sectional view showing the main part of the third embodiment of the internal combustion engine according to this invention. Figure 7 is a cross-sectional view of a sub-chamber used in an internal combustion engine. Figure 7 is a perspective view of a sub-chamber used in an internal combustion engine.

A first embodiment of the internal combustion engine 1 according to this invention will be described based on the drawings. As shown in Figure 1, this internal combustion engine 1 is a sub-chamber type internal combustion engine (gasoline engine) whose main components are a main combustion chamber 5 equipped with a piston 4 that reciprocates within a cylinder head 2 and a cylinder block 3, and a sub-chamber 6 provided within the main combustion chamber 5. Note that this figure shows the main part of one of the multiple cylinders of the internal combustion engine 1. Furthermore, this figure shows only the components directly related to this invention, and general configurations such as the intake passage that supplies air to the main combustion chamber 5, the exhaust passage that exhausts combustion gases from the main combustion chamber 5, and the injection device that supplies fuel to the main combustion chamber 5 are omitted. In this embodiment, the internal combustion engine 1 has an injection device in the intake passage and mixes intake air and fuel in the intake passage and the main combustion chamber 5, but the invention is not limited to this configuration.

The cylinder head 2 consists of a lower head 7 and an upper head 8 positioned corresponding to the location of each cylinder. On the upper surface of the lower head 7, cylindrical recesses 9 with internal threads are formed, corresponding to the location of each cylinder. A through-hole 10 communicating with the main combustion chamber 5 is formed at the bottom of these recesses 9. The outer circumference of the upper head 8 has internal threads, and by screwing the upper head 8 into the lower head 7, the two are integrated. Between the lower head 7 and the upper head 8, a sealing member 11, such as a copper washer, is provided.

A cavity is formed in the axial center of the upper head 8, extending upward from its bottom surface, and the spark plug 12 is positioned to face this cavity. On the bottom surface of the recess 9 formed in the lower head 7, and on the lower surface of the upper head 8, one annular groove 13, 14 and two seal grooves 15, 16 are concentrically formed, sequentially from the outer diameter side to the inner diameter side. Note that the upper head 8 and the spark plug 12 may be formed as a single unit.

As shown in Figures 1 to 3, the sub-chamber 6 has a main body portion 17 having an outer surface facing the main combustion chamber 5 and an inner surface facing the opposite side of the outer surface, and a flange portion 18 extending radially outward from the upper outer edge of the main body portion 17. The main body portion 17 is a bottomed cylindrical shape with an upward opening, and at positions radially outward from the axis of the main body portion 17 (a line passing through the center of the main body portion 17 and extending toward the cylinder head 2 and piston 4 (vertically)), a plurality of injection holes 19 are formed that penetrate the inner and outer surfaces of the main body portion 17 and are inclined downward in the axial direction on one side of the circumferential direction (direction of rotation around the axis) with respect to the radial direction (direction perpendicular to the direction in which the axis extends (hereinafter referred to as "axial direction")). Because the injection holes 19 are inclined on one side of the circumferential direction with respect to the radial direction, the sub-chamber 6 is configured to rotate due to the outward flame injection pressure from the injection holes 19. The lower end of the main body 17 and the injection holes 19 protrude towards the main combustion chamber 5 through the through-holes 10 formed in the lower head 7. The outer surface of the main body 17 is polished to a mirror finish.

In this embodiment, the nozzle 19 is configured to be inclined radially, on one side in the circumferential direction, and axially downward. However, as long as it is inclined at least on one side in the circumferential direction, the rotational action of the sub-chamber 6 due to the flame injection pressure from the nozzle 19 will be exerted.

Seal grooves 20 are formed on the upper and lower surfaces of the flange portion 18, facing the seal grooves 15 and 16 formed in the lower head 7 and upper head 8, respectively. Multiple fins 21 are provided at regular intervals in the circumferential direction on the peripheral edge of the flange portion 18, formed by increasing the axial width (vertical width in this embodiment) of the flange portion 18. Furthermore, multiple oil holes 22 are provided at regular intervals in the circumferential direction, penetrating the upper and lower surfaces of the flange portion 18.

The flange portion 18 is rotatably supported from above and below by a clamping portion 23 formed in the cylinder head 2. The clamping portion 23 is formed between the bottom surface of the recess 9 formed in the lower head 7 and the bottom surface of the upper head 8. At this time, the sub-chamber combustion chamber 24 is formed by the internal space of the main body portion 17 of the sub-chamber 6 and the cavity formed in the upper head 8.

An annular oil reservoir 25 is formed by annular grooves 13 and 14, respectively, formed in the integrated lower head 7 and upper head 8, and lubricating oil is introduced into this oil reservoir 25. The fins 21 formed on the periphery of the flange portion 18 are located within the oil reservoir 25 and immersed in the oil.

The oil reservoir 25 is connected to a supply unit 26 that supplies oil from an oil gallery (not shown) to the reservoir 25, and a discharge unit 27 that returns oil from the reservoir 25 to the oil gallery. The oil in the reservoir 25 is pumped under pressure by an oil pump (not shown).

Two seal rings 28 are concentrically positioned between the seal grooves 15 and 20 formed on the bottom surface of the recess in the lower head 7 and the lower surface of the flange portion 18, and between the seal grooves 16 and 20 formed on the lower surface of the upper head 8 and the upper surface of the flange portion 18. By providing these seal rings 28, oil from the oil reservoir 25 is prevented from leaking to the main body 17 through the gap between the cylinder head 2 (lower head 7, upper head 8) and the flange portion 18, and pressure from the combustion of the fuel-air mixture in the main combustion chamber 5 and sub-chamber 6 acts on the oil reservoir 25. The number of seal rings 28 can be increased or decreased as appropriate, as long as their function is fully realized.

The vertical pressing force applied to the flange portion 18 by the clamping portion 23 of the cylinder head 2 is appropriately set to ensure the sealing performance of the seal ring 28 while not hindering the smooth rotation of the sub-chamber 6.

The angular velocity ω of the rotation of the sub-chamber 6 due to the reaction of the flame ejection from the nozzle 19 can be calculated by the following equation (1). Here, Q is the combustion pressure injection amount at the time of ignition in the sub-chamber combustion chamber 24, R is the radial distance from the central axis to the tip of the nozzle 19, A is the cross-sectional area of each nozzle 19, θ is the angle that the injection direction makes with the radial direction, and a is a coefficient determined by the frictional force acting on the sub-chamber 6 during rotation. The combustion pressure injection amount Q is appropriately considered based on the volume of each cylinder, etc. Note that this equation (1) is applicable when two nozzles 19 are formed at circumferentially opposing positions on the sub-chamber 6. By using this equation, it is possible to determine the specifications of the sub-chamber 6, such as the radial distance R from the central axis to the tip of the nozzle 19, the cross-sectional area A of each nozzle 19, and the angle θ that the injection direction makes with the radial direction, in order to obtain the desired angular velocity ω.
ω=(aQ/2RA)×sinθ (1)

In the internal combustion engine 1 described above, the sub-chamber 6 is rotatably supported by the cylinder head 2 around an axis extending in the direction of movement of the piston 4. The sub-chamber 6 is configured to rotate due to the outward flame injection pressure from the nozzles 19. Therefore, during the combustion stroke, the flame injected from one nozzle 19 spreads throughout the entire circumferential direction of the main combustion chamber 5. Even if there are differences in the size of the flames injected from each nozzle 19, uneven combustion of the fuel in the main combustion chamber 5 can be suppressed. Furthermore, this rotation can suppress jet shock caused by collisions between flame propagations injected from each nozzle 19.

Furthermore, during the intake compression process, the inertial rotation accompanying the flame injection pushes the mixture of intake air and fuel, which has been mixed in the intake passage and main combustion chamber 5, into the sub-chamber 6. This creates turbulence within the sub-chamber 6, improving premixing and scavenging within the sub-chamber 6.

The sub-chamber 6 used in the internal combustion engine 1 described above has fins 21 formed on the peripheral edge of the flange portion 18. Therefore, the rotation of the fins 21 can assist in the discharge of oil from the discharge portion 27. Furthermore, when the rotation of the sub-chamber 6 becomes excessive due to flame injection, increasing the oil pumping force provides rotational resistance to the fins 21, thereby weakening the rotation of the sub-chamber 6.

Furthermore, while the sub-chamber 6 experiences downward pressure due to combustion in the sub-chamber combustion chamber 24, and upward pressure due to combustion in the main combustion chamber 5, there is a risk that the sub-chamber 6 may move vertically or tilt axially when these pressures are applied. However, because the peripheral edge (fins 21) of the flange portion 18 is immersed in oil, it functions as a damper, suppressing the movement and tilting of the sub-chamber 6. Also, because the fins 21 are immersed in oil, heat from the sub-chamber 6 can be quickly dissipated into the oil. Additionally, since multiple oil holes 22 are formed in the flange portion 18 of the sub-chamber 6, penetrating its upper and lower surfaces, the flow of oil between these surfaces can be promoted. Furthermore, foreign matter such as shavings generated due to the rotation of the sub-chamber 6 can be smoothly removed by the flow of oil.

Figure 4 shows a second embodiment of the internal combustion engine 1 according to this invention. The internal combustion engine 1 according to the second embodiment shares its basic configuration with the internal combustion engine 1 according to the first embodiment, but differs in the configuration of the sub-chamber 6. Specifically, as shown in Figures 4 to 6, instead of forming fins 21 on the peripheral edge of the upper surface of the flange portion 18 of the sub-chamber 6, an annular projection 29 is formed along the entire circumference, standing axially and acting as a barrier to the radially outward flow of oil.

By forming the protrusion 29 in this manner, when the sub-chamber 6 rotates, oil is retained inside the protrusion 29, preventing the oil from accumulating on the side wall (end wall) of the oil reservoir 25 due to centrifugal force, thus preventing loss of lubrication and fluidity. Therefore, smooth rotation of the sub-chamber 6 can be ensured. In this embodiment, fins 21 are formed on the lower surface of the flange portion 18. Since the supply portion 26 and discharge portion 27 are connected to the oil reservoir 25 below the flange portion 18, it is preferable to provide fins 21 on the lower surface of the flange portion 18 to promote oil circulation.

In this embodiment, the projection 29 is positioned to extend from the peripheral edge of the upper surface of the flange portion 18 toward the upper head 8. However, this direction is not limited; it may be positioned toward the opposite side of the upper head 8, or both toward the upper head 8 and the opposite side.

Figure 7 shows a third embodiment of the internal combustion engine 1 according to this invention. The internal combustion engine 1 according to the third embodiment is configured to provide rotational force to the sub-chamber 6 not by the reaction force from the flame ejection from the nozzle 19, as in the internal combustion engine 1 according to the first and second embodiments, but by the action of an electromagnet in addition to the rotational force from the reaction force. Although the oil reservoir 25 is not shown in Figure 7, an oil reservoir 25 may be provided in this embodiment as well.

As shown in Figures 7 to 9, the flange portion 18 has multiple rotors 30 (e.g., permanent magnets) arranged at regular intervals in the circumferential direction, and the cylinder head 2 has a stator 31 (e.g., an electromagnet) positioned radially opposite to the rotors 30. A rotational force is applied to the sub-chamber 6 by energizing the stator 31. Furthermore, the cylinder head 2 is equipped with a Hall sensor 32 facing the flange portion 18, and by detecting the rotation of the rotors 30 with this Hall sensor 32, the angular velocity ω' of the sub-chamber 6 can be measured.

In this way, by enabling the application of rotational force to the sub-chamber 6 through the action of an electromagnet, the rotation of the sub-chamber 6 can be controlled more precisely compared to the first and second embodiments.

In this embodiment, similar to the first and second embodiments, the nozzle 19 is configured to be inclined circumferentially with respect to the radial direction. However, since the electromagnet alone can impart rotational force to the sub-chamber 6, the nozzle 19 can also be configured not to be inclined circumferentially.

The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. Therefore, the scope of the invention is indicated by the claims rather than the foregoing description, and all modifications within the meaning and scope of the claims are intended to be included.

1 Internal combustion engine 2 Cylinder head 3 Cylinder block 4 Piston 5 Main combustion chamber 6 Sub-chamber 7 Lower head 8 Upper head 9 Recess 10 Through hole 11 Seal member 12 Spark plug 13, 14 Annular groove 15, 16 Seal groove 17 Main body 18 Flange 19 Injection hole 20 Seal groove 21 Fin 22 Oil hole 23 Clamping part 24 Sub-chamber combustion chamber 25 Oil reservoir 26 Supply part 27 Discharge part 28 Seal ring 29 Protrusion 30 Rotor 31 Stator 32 Hall sensor ω (Calculated) angular velocity ω' Measured angular velocity

Claims (5)

A main combustion chamber comprising a cylinder head and piston,
A sub-chamber provided within the main combustion chamber,
The sub-chamber is rotatably supported by the cylinder head around the axis of a shaft extending in the direction of movement of the piston,
An internal combustion engine wherein the sub-chamber has a main body having an outer surface facing the main combustion chamber and an inner surface facing the opposite side of the outer surface, and an injection hole is formed at a position radially outward from the center of the axis of the main body, penetrating the inner and outer surfaces of the main body and inclined at least in the circumferential direction with respect to the radial direction, and the sub-chamber is configured to rotate due to the outward injection pressure from the injection hole . The internal combustion engine according to claim 1, wherein the sub-chamber has a flange portion extending radially outward, and the cylinder head has a clamping portion that rotatably supports the flange portion and an oil reservoir portion in which oil is stored and a part of the flange portion is immersed. The internal combustion engine according to claim 2 , wherein a projection is formed circumferentially on the peripheral edge of the flange portion, which stands upright in the axial direction and acts as a barrier to the radially outward flow of oil. The internal combustion engine according to claim 2, further comprising a supply unit for supplying oil to the oil reservoir and a discharge unit for discharging oil from the oil reservoir, wherein a plurality of fins that stand upright in the axial direction are provided on the flange at intervals in the circumferential direction. The internal combustion engine according to claim 1, comprising a permanent magnet provided in the sub-chamber and an electromagnet provided in the cylinder head, wherein rotational force is applied to the sub-chamber by energizing the electromagnet.