JP7831349B2 - 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 pre-chamber internal combustion engines, particularly passive pre-chamber engines that introduce a mixture of fuel and air-fuel mixture from the intake passage and main combustion chamber into the pre-chamber, the amount of fuel filled into the pre-chamber varies from cycle to cycle depending on the operating conditions. Furthermore, the energy of the flames injected from each nozzle, i.e., the force of the flames ejected into the main combustion chamber (hereinafter referred to as "JET force"), changes according to the amount of fuel filled into the pre-chamber, resulting in a change in JET force from cycle to cycle. This fluctuation in JET force directly affects the cycle combustion fluctuations in the main combustion chamber and may pose a problem in terms of stable combustion 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.

To solve the above problems, this invention provides an internal combustion engine comprising a main combustion chamber equipped with a cylinder head and a piston, a sub-chamber within the main combustion chamber that is rotatably supported by the cylinder head around an axis extending in the direction of piston movement, and a control unit that controls the rotation of the sub-chamber. The control unit controls the rotational speed of the sub-chamber according to the rotational speed of the internal combustion engine.

In the above configuration, the control unit can be configured to control the rotation speed of the sub-chamber so that it decreases as the rotation speed of the internal combustion engine increases.

Furthermore, in the above configuration, the control unit can be configured to control the rotational speed of the sub-chamber according to the rotational speed and load of the internal combustion engine.

Here, the control unit can adopt a configuration in which, when the rotational speed of the internal combustion engine is below the first rotational speed, the rotational speed of the sub-chamber increases as the load on the internal combustion engine increases, and when the rotational speed of the internal combustion engine exceeds the first rotational speed, the rotational speed of the sub-chamber decreases as the load on the internal combustion engine increases.

Furthermore, the system has a first region where the rotational speed of the internal combustion engine exceeds the first rotational speed and the load of the internal combustion engine exceeds the first load, and a second region where the rotational speed of the internal combustion engine exceeds the first rotational speed and the load of the internal combustion engine exceeds the second load, which is greater than the first load. The control unit can employ a configuration in which, in the second region, enriches the target air-fuel ratio more than in the first region excluding the second region, and increases the rotational speed of the sub-chamber in the second region compared to the first region excluding the second region.

When the control unit controls the rotation speed of the sub-chamber to decrease as the rotation speed of the internal combustion engine increases, if the actual output of the internal combustion engine falls below the target output by a predetermined amount, it can employ a configuration that suppresses the decrease in the rotation speed of the sub-chamber when the rotation speed of the internal combustion engine increases.

In this invention, the rotation speed of the sub-chamber is controlled according to the rotation speed of the internal combustion engine, thereby achieving a stable combustion state in the main combustion chamber.

This graph illustrates an example of the control mechanism of this invention. This graph illustrates an example of the control mechanism of this invention. This is a schematic cross-sectional view showing the main parts of an embodiment of an internal combustion engine according to this invention. Figure 3 is a plan view of the components that make up the sub-chamber used in the internal combustion engine shown. Figure 3 is a cross-sectional view of a component constituting a sub-chamber used in an internal combustion engine. Figure 3 is a perspective view of the components that make up the sub-chamber used in the internal combustion engine shown. This is a schematic diagram of a vehicle equipped with an internal combustion engine according to this invention.

An embodiment of the internal combustion engine 1 according to this invention will be described based on the drawings. Figures 1 and 2 are graphs illustrating an example of control according to this invention, and Figures 3 to 6 show the main parts and components of the internal combustion engine 1 according to this embodiment. Figure 7 shows a vehicle V equipped with this internal combustion engine 1.

In this embodiment, the internal combustion engine 1, as shown in Figure 3, is a sub-chamber type internal combustion engine (gasoline engine) whose main components are a main combustion chamber 5 formed by a cylinder head 2 and a cylinder block 3, a piston 4 that reciprocates within the main combustion chamber 5, and a sub-chamber 6 provided within the main combustion chamber 5. Note that this figure shows the main parts of one of the multiple cylinders of the internal combustion engine 1. Furthermore, this figure only shows components directly related to this invention, and general configurations such as the intake passage that supplies air into 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 configuration is not limited to this. Hereinafter, the axis along the direction of movement of the piston 4 in the main combustion chamber 5 (the axis of the cylinder) will be simply referred to as the "axis," and the circumferential direction around that axis will be simply referred to as the "axis direction."

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 heads are integrated.

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. Note that the upper head 8 and the spark plug 12 may be formed as a single unit.

As shown in Figure 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 has a bottom portion and a circumferential portion and is concave in shape with an upward opening. At positions radially outward from the center of the axis of the main body portion 17, multiple injection holes 19 are formed, penetrating between the inner and outer surfaces of the circumferential portion and inclined axially downward as they approach the outer diameter. The lower end of the main body portion 17 and the injection holes 19 protrude towards the main combustion chamber 5 through a through hole 10 formed in the lower head 7. The outer surface of the main body portion 17 is mirror-polished.

The flange portion 18 is rotatably supported by a circumferential groove 30 formed between the lower head 7 and the upper head 8 that constitute the cylinder head 2. At this time, the internal space of the main body portion 17 of the sub-chamber 6 and the cavity formed in the upper head 8 constitute the sub-chamber combustion chamber 24. The gap between the flange portion 18 and the circumferential groove 30 of the cylinder head 2 is appropriately set to a size that does not hinder the smooth rotation of the sub-chamber 6.

Multiple rotors 31 (permanent magnets) are provided at regular intervals in the circumferential direction on the flange portion 18, and a stator 32 (electromagnet) is provided on the cylinder head 2 so as to be radially opposite to the rotors 31. The rotors 31 and stator 32 constitute a motor. When the stator 32 is energized, a rotational force (driving force) around the axis is applied to the sub-chamber 6. A Hall sensor 33 is also provided on the cylinder head 2 so as to face the flange portion 18, and by detecting the rotation of the rotors 31 with this Hall sensor 33, the angular velocity of the rotation of the sub-chamber 6 can be measured. The sub-chamber 6 is controlled to rotate at an arbitrary rotational speed while the internal combustion engine 1 is running. This control of the rotation of the sub-chamber 6 is controlled by the control unit 41 of the Electronic Control Unit 40 provided in the vehicle V equipped with the internal combustion engine 1 (see Figure 7). The Electronic Control Unit 40 controls all the devices of the internal combustion engine 1 and the vehicle V.

As described above, the internal combustion engine 1 is configured such that the sub-chamber 6 is rotatably supported around its axis by the cylinder head 2, and the sub-chamber 6 rotates when the stator 32 is energized. This configuration suppresses the variation in the flame spread within the main combustion chamber 5 caused by fluctuations in the size of the flames injected from each nozzle 19 during the combustion cycle. Furthermore, this rotation suppresses the shock caused by collisions between flame propagations injected from each nozzle 19.

On the other hand, by rotating the sub-chamber 6, each nozzle 19 moves away from the direction of travel of the flame ejected from each nozzle 19. Therefore, rotating the sub-chamber 6 reduces the straightness of the flame, and the time it takes for the flame from the sub-chamber 6 to reach the end of the main combustion chamber 5 increases. Furthermore, when introducing intake air and fuel (hereinafter collectively referred to as "air-mixture") into the sub-chamber 6 during the intake compression stroke, rotating the sub-chamber 6 causes the nozzles 19, which are the inlets for introducing the air-mixture, to move, making it more difficult to introduce the air-mixture into the sub-chamber 6. These effects become more pronounced as the rotation speed of the sub-chamber 6 increases. This invention utilizes these characteristics generated by rotating the sub-chamber 6 to appropriately control the combustion state of the internal combustion engine 1 by controlling the rotation speed of the sub-chamber 6 based on the rotation speed and load of the internal combustion engine 1.

The following describes the control of the sub-chamber 6 by the control unit 41.

The control unit 41 controls the rotational speed of the sub-chamber 6 (hereinafter referred to as the sub-chamber rotational speed) according to the rotational speed of the internal combustion engine 1 (hereinafter referred to as the engine rotational speed). Here, the engine rotational speed and the sub-chamber rotational speed are rotations per unit time (rpm), respectively. In a conventional internal combustion engine 1 equipped with a sub-chamber 6, the intensity of the flame injected from each nozzle 19 is basically set to correspond to high rotational speed and high load operating conditions. This is because if the flame intensity were set to correspond to low rotational speed or low load conditions, the flame intensity would be insufficient when transitioning to high rotational speed and high load operating conditions. Therefore, the flame could be too strong or too weak depending on the engine rotational speed.

However, according to this embodiment, the rotation speed of the sub-chamber can be increased or decreased according to the engine speed, and the amount of premixed gas supplied to the sub-chamber 6 can be changed, so the flame intensity can be adjusted according to the operating conditions.

Specifically, the control unit 41 controls the sub-chamber rotation speed so that it decreases as the engine speed increases. That is, when the engine speed is high, the sub-chamber rotation speed is reduced to ensure the flame's straightness and to ignite the air-fuel mixture in the main combustion chamber 5 earlier. On the other hand, when the engine speed is low, the sub-chamber rotation speed is increased to suppress combustion fluctuations in the main combustion chamber 5, and to reduce the flame's straightness and the introduction of the air-fuel mixture into the sub-chamber 6, thereby suppressing the flame's intensity and maintaining a combustion state in the main combustion chamber 5 that is appropriate for the engine speed.

Furthermore, the control unit 41 may also perform control that takes into account the load of the internal combustion engine 1 (hereinafter referred to as engine load). The purpose is to perform more precise control according to the operating conditions at that time by controlling the sub-chamber rotation speed according to the engine speed and engine load.

Specifically, the control unit 41 increases the sub-chamber rotation speed as the engine load increases when the engine speed is below the first rotation speed a0 shown in Figure 1, and decreases the sub-chamber rotation speed as the engine load increases when the engine speed exceeds the first rotation speed a0. That is, when the engine speed is on the low side, the sub-chamber rotation speed increases as the engine load increases, and when the engine speed is on the high side, the sub-chamber rotation speed decreases as the engine load increases. The first rotation speed a0 can be set to an appropriate value in advance, such as an intermediate value in the rotation range in which the internal combustion engine 1 is expected to be used. A low engine speed and high load condition is a state where the fuel supply is large despite the low engine speed. Therefore, to prevent excessive flame intensity, the sub-chamber rotation speed is increased to suppress the flame intensity. Conversely, a high engine speed and high load condition is a state where the engine speed is large and the fuel supply is also large. Therefore, to ensure the straightness of the flame, the sub-chamber rotation speed is decreased in order to burn the large amount of fuel quickly.

Figure 2 shows a simplified map of the pre-chamber rotation speed based on engine speed and load. In Figure 2, the operating range of the internal combustion engine 1 is divided into four regions based on engine speed and load. Region E is a low-speed, low-load region where the engine speed is 1st rotation speed a0 or less and the engine load is a predetermined 1st load b0 or less. Region F is a low-speed, high-load region where the engine speed is 1st rotation speed a0 or less and the engine load exceeds 1st load b0. Region G is a high-speed, low-load region where the engine speed exceeds 1st rotation speed a0 and the engine load is 1st load b0 or less. Region H is a high-speed, high-load region where the engine speed exceeds 1st rotation speed a0 and the engine load exceeds 1st load b0. The pre-chamber rotation speed is medium speed in region E, high speed in region F, low speed in region G, and very low speed in region H. That is, when the sub-chamber rotational speed is ωe in region E, ωf in region F, ωg in region G, and ωh in region H, then ωf > ωe > ωg > ωh. Note that the sub-chamber rotational speeds ωe, ωf, ωg, and ωh may be constant within each region E, F, G, and H, respectively, or they may be controlled to continuously change based on the engine speed and load within each region.

Returning to Figure 1, let's continue the explanation. In this embodiment, the internal combustion engine 1 performs enrichment control in the ultra-high rotation and high-load region near the limit operating region. Here, enrichment control is the process of increasing the fuel amount to lower the exhaust temperature in order to protect the exhaust system when the output is at full throttle. In other words, the exhaust temperature is lowered by the heat of vaporization of the fuel due to the increased fuel amount. In this embodiment, in the high rotation and high-load region C (corresponding to region H in Figure 2, hereinafter referred to as the first region), where the engine speed exceeds the first rotation speed a0 and the engine load exceeds the first load b0, the region where the second load b1 is greater than or equal to the first load b0 and less than or equal to the upper limit of the operating load bmax of the internal combustion engine 1 is defined as the ultra-high rotation and high-load region D (second region) where enrichment control is performed.

Furthermore, in the second region where enrichment control is performed, the sub-chamber rotation speed is increased compared to the first region. That is, in the region where the engine speed exceeds the first rotation speed a0, the sub-chamber rotation speed decreases as the engine load increases. However, when the engine load exceeds the second load b1, the sub-chamber rotation speed is increased compared to when the engine load is less than the second load b1. This suppresses the excessive increase in flame that occurs with enrichment.

Here, the second load b1 corresponds to the value at the boundary between operating region C (excluding operating region D) and operating region D. While the second load b1 may be a constant value regardless of engine speed, it is desirable to set it so that the value of the second load b1 decreases as the engine speed increases, as shown by boundary line c in Figure 1.

Furthermore, in this embodiment, when the actual output of the internal combustion engine 1 (hereinafter referred to as the actual engine output) falls below the target output by a predetermined amount, the decrease in the sub-chamber rotation speed when the engine rotation speed increases is suppressed.

Conventionally, under driving conditions such as sudden acceleration when the accelerator pedal is pressed abruptly, it is common practice to increase the intake air volume and advance the ignition timing. However, while ignition timing advance occurs immediately, there is a time lag in increasing intake air volume. This time lag causes knocking, so acceleration retard control (control that delays the ignition timing to account for the intake delay) is performed to suppress this. In contrast, in this embodiment, when the actual engine output is less than a predetermined amount below the target output, the decrease in the sub-chamber rotation speed when the engine speed increases is suppressed. That is, by maintaining a high sub-chamber rotation speed, the straightness of the flame is suppressed and the combustion in the main combustion chamber 5 is delayed, thereby expecting an effect similar to acceleration retard control. In other words, by strengthening the rotation of the sub-chamber 6, acceleration retardation is made unnecessary. Here, the control that suppresses the decrease in sub-chamber rotation speed is not limited to maintaining the rotation speed of the sub-chamber 6 or reducing the amount of decrease in the rotation speed of the sub-chamber 6, but also includes the concept of increasing the rotation speed of the sub-chamber 6.

The embodiments disclosed herein should be considered illustrative and not restrictive in all respects. Therefore, the scope of the invention is indicated by the claims rather than the above description, and all modifications within the meaning and scope of equivalence to the claims are intended. For example, in this embodiment, the rotation of the sub-chamber 6 is controlled using an electromagnet, but the configuration is not limited to this; the rotation of the sub-chamber 6 may also be controlled using hydraulics. Alternatively, the nozzle 19 may be tilted to either the radial or circumferential direction, and the sub-chamber 6 may be rotated by the force of the flame. In this case, the rotation of the sub-chamber 6 can be controlled using an electromagnet or hydraulics.

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 part 19 Injection hole 24 Sub-chamber combustion chamber 30 Circumferential groove 31 Rotor 32 Stator 33 Hall sensor 40 Electronic control unit 41 Control unit V Vehicle

Claims (5)

A main combustion chamber comprising a cylinder head and piston,
The main combustion chamber includes a sub-chamber supported in the cylinder head so as to be rotatable about an axis extending in the direction of movement of the piston,
The system includes a control unit that controls the rotation of the sub-chamber,
The control unit controls the rotational speed of the sub-chamber according to the rotational speed of the internal combustion engine .
The control unit controls the internal combustion engine such that the rotational speed of the sub-chamber decreases as the rotational speed of the internal combustion engine increases . The internal combustion engine according to claim 1, wherein the control unit controls the rotational speed of the sub-chamber according to the rotational speed and load of the internal combustion engine. The control unit increases the rotational speed of the sub-chamber as the load on the internal combustion engine increases when the rotational speed of the internal combustion engine is less than or equal to a first rotational speed, and decreases the rotational speed of the sub-chamber as the load on the internal combustion engine increases when the rotational speed of the internal combustion engine exceeds the first rotational speed. The system has a first region in which the rotational speed of the internal combustion engine exceeds the first rotational speed and the load on the internal combustion engine exceeds the first load, and a second region in which the rotational speed of the internal combustion engine exceeds the first rotational speed and the load on the internal combustion engine exceeds the second load which is greater than the first load.
The internal combustion engine according to claim 3, wherein the control unit performs enrichment control in the second region to make the target air-fuel ratio richer than in the first region excluding the second region, and increases the rotational speed of the sub-chamber in the second region compared to the first region excluding the second region. The internal combustion engine according to claim 1 , wherein if the actual output of the internal combustion engine falls below the target output by a predetermined amount, the decrease in the rotational speed of the sub-chamber when the rotational speed of the internal combustion engine increases is suppressed.