Internal combustion engine

Abstract

To obtain a stable combustion state in a main combustion chamber in an auxiliary chamber type internal combustion engine.SOLUTION: An internal combustion engine comprises a main combustion chamber 5 comprising a cylinder head 2 and a piston 4, an auxiliary chamber 6 supported rotatably around an axis extending in a movement direction of the piston 4 by the cylinder head 2 in the main combustion chamber 5, and a control unit 41 for controlling the rotation of the auxiliary chamber 6. The control unit 41 controls the rotation speed of the auxiliary chamber 6 in accordance with the rotation speed of the internal combustion engine 1.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] This invention relates to an internal combustion engine.

Background Art

[0002] In a prechamber-type internal combustion engine having a prechamber provided in a main combustion chamber, a mixture of fuel and intake air is supplied into the prechamber, and the mixture is ignited in the prechamber by a spark plug. When a flame is formed in the prechamber, the flame is injected into the main combustion chamber through a plurality of injection holes formed in the prechamber. Then, the mixture in the main combustion chamber is ignited by the plurality of injected flames. Thereby, a good combustion state in the main combustion chamber is realized (for example, refer to Patent Document 1 below).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In a prechamber-type internal combustion engine, particularly in a passive prechamber-type internal combustion engine that introduces a mixture mixed in an intake passage or a main combustion chamber into the prechamber, the amount of fuel filled in the prechamber varies from cycle to cycle according to the operating state. Further, the energy of the flame injected from each injection hole, that is, the power of the flame jumping out into the main combustion chamber (hereinafter referred to as JET power) changes according to the amount of fuel filled in the prechamber. Therefore, the JET power changes from cycle to cycle. This variation in JET power is directly related to the cycle combustion variation on the main combustion chamber side and may pose a problem in terms of stable combustion in the main combustion chamber.

[0005] Therefore, an object of this invention is to obtain a stable combustion state in the main combustion chamber in a prechamber-type internal combustion engine.

Means for Solving the Problems

[0006] To solve the above problems, this invention provides an internal combustion engine comprising a main combustion chamber having 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 movement of the piston, and a control unit that controls the rotation of the sub-chamber, wherein the control unit controls the rotational speed of the sub-chamber according to the rotational speed of the internal combustion engine.

[0007] In the above configuration, the control unit can be configured to control the rotation speed of the sub-chamber to decrease as the rotation speed of the internal combustion engine increases.

[0008] 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.

[0009] Here, the control unit can adopt a configuration in which, when the rotational speed of the internal combustion engine is at or 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.

[0010] 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 perform enrichment control in the second region to make the target air-fuel ratio richer than in the first region excluding the second region, and can also adopt a configuration in the second region to increase the rotational speed of the sub-chamber compared to the first region excluding the second region.

[0011] 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 adopt a configuration that suppresses the decrease in the rotation speed of the sub-chamber when the rotation speed of the internal combustion engine increases. [Effects of the Invention]

[0012] In this invention, the rotation speed of the sub-chamber is controlled according to the rotation speed of the internal combustion engine, thereby enabling a stable combustion state in the main combustion chamber. [Brief explanation of the drawing]

[0013] [Figure 1] This graph illustrates an example of the control mechanism of this invention. [Figure 2] This graph illustrates an example of the control mechanism of this invention. [Figure 3] This is a schematic cross-sectional view showing the main parts of an embodiment of an internal combustion engine according to this invention. [Figure 4] Figure 3 is a plan view of the components that make up the sub-chamber used in the internal combustion engine shown. [Figure 5] Figure 3 is a cross-sectional view of a component constituting a sub-chamber used in an internal combustion engine. [Figure 6] Figure 3 is a perspective view of the components that make up the sub-chamber used in the internal combustion engine shown. [Figure 7] This is a schematic diagram of a vehicle equipped with an internal combustion engine according to this invention. [Modes for carrying out the invention]

[0014] 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 showing 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 of the invention. Figure 7 shows a vehicle V equipped with this internal combustion engine 1.

[0015] 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 shows only the components directly related to this invention, and general configurations such as the intake passage that sends 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 it is not limited to this configuration. 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."

[0016] The cylinder head 2 consists of a lower head 7 and an upper head 8 positioned to correspond 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 lower head 7 and the upper head 8 are integrated.

[0017] A cavity is formed in the axis of the upper head 8, extending upward from its bottom surface, and the spark plug 12 is provided facing into this cavity. The upper head 8 and the spark plug 12 may be formed as a single unit.

[0018] As shown in FIG. 3, the auxiliary chamber 6 has a main body portion 17 having an outer surface facing the main combustion chamber 5 and an inner surface facing the side opposite to the outer surface, and a flange portion 18 extending radially outward from the outer edge of the upper end of the main body portion 17. The main body portion 17 has a bottom portion and a peripheral surface portion and forms an upwardly open concave shape. At a position radially outward from the center of the axis of the main body portion 17, a plurality of spray holes 19 penetrating between the inner and outer surfaces of the peripheral surface portion and inclined axially downward as going toward the outer diameter side are formed. The lower end of the main body portion 17 and the spray holes 19 project toward the main combustion chamber 5 side through a through hole 10 formed in the lower head 7. The outer surface of the main body portion 17 is subjected to mirror finishing.

[0019] The flange portion 18 is rotatably supported by a circumferential groove 30 formed between the lower head 7 and the upper head 8 constituting the cylinder head 2. At this time, an auxiliary combustion chamber 24 is constituted by the internal space of the main body portion 17 of the auxiliary chamber 6 and a cavity portion formed in the upper head 8. The clearance in the circumferential groove 30 of the cylinder head 2 with respect to the flange portion 18 is appropriately set to a size that does not prevent the smooth rotation of the auxiliary chamber 6.

[0020] A plurality of 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 face the rotor 31 in the radial direction. The rotor 31 and the stator 32 constitute a motor. Then, a rotational force (driving force) around the axis is applied to the auxiliary chamber 6 by energizing the stator 32. Further, a hall sensor 33 is provided on the cylinder head 2 so as to face the flange portion 18. By detecting the rotation of the rotor 31 with this hall sensor 33, the angular velocity of the rotation of the auxiliary chamber 6 can be actually measured. The auxiliary chamber 6 is controlled to rotate at an arbitrary rotational speed during the driving of the internal combustion engine 1. Such control of the rotation of the auxiliary chamber 6 is controlled by a control unit 41 of an electronic control unit (Electronic Control Unit) 40 provided in a vehicle V equipped with this internal combustion engine 1 (see FIG. 7). The electronic control unit 40 controls the entire internal combustion engine 1 and the devices provided in the vehicle V.

[0021] As described above, the internal combustion engine 1 is configured such that the sub-chamber 6 is rotatably supported around an axis by the cylinder head 2, and the sub-chamber 6 rotates when the stator 32 is energized. This makes it possible to suppress differences in the way the flame spreads within the main combustion chamber 5, which would otherwise occur due to variations in the size of the flames injected from each nozzle 19 during the combustion stroke. Furthermore, this rotation can suppress shocks caused by collisions between flame propagations injected from each nozzle 19.

[0022] 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. Also, 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 each nozzle 19, which is the inlet 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. The present invention utilizes these characteristics generated by rotating the sub-chamber 6 and appropriately controls 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.

[0023] The control of the rotation of the sub-chamber 6 by the control unit 41 will be described below.

[0024] 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. As a result, the flame could be too strong or too weak depending on the engine rotational speed.

[0025] 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.

[0026] Specifically, the control unit 41 controls the sub-chamber rotation speed to decrease as the engine speed increases. That is, when the engine speed is high, the sub-chamber rotation speed is reduced to ensure the straightness of the flame 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 also to suppress the straightness of the flame and the introduction of the air-fuel mixture into the sub-chamber 6, thereby suppressing the flame intensity and creating a combustion state in the main combustion chamber 5 that is appropriate for the engine speed.

[0027] 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.

[0028] 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. In other words, 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 in advance to an appropriate value, such as the midpoint of the rotation range in which the internal combustion engine 1 is expected to be used. The low engine speed and high load state is a state in which the fuel supply amount is large despite the low engine speed. For this reason, the sub-chamber rotation speed is increased to suppress the flame intensity so that it does not become excessively strong. Also, the high engine speed and high load state is a state in which the engine speed is large and the fuel supply amount is large. For this reason, the sub-chamber rotation speed is decreased to ensure the straightness of the flame in order to burn the large amount of fuel early.

[0029] 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 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 rotation 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 rotation speeds ωe, ωf, ωg, and ωh may be constant within each region E, F, G, and H, respectively, or they may be controlled to change continuously based on the engine speed and load within each region E, F, G, and H.

[0030] 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 amount of fuel 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 the operating upper limit load bmax of the internal combustion engine 1 is less than or equal to the ultra-high rotation and high load region D (second region) in which enrichment control is performed.

[0031] Then, 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 is decreased as the engine load increases, but when the engine load becomes the second load b1 or higher, the sub-chamber rotation speed is increased compared to when the engine load is less than the second load b1. This makes it possible to suppress the excessive increase in flame that occurs with enrichment.

[0032] Here, the second load b1 corresponds to the value at the boundary between operating region C (excluding operating region D) and operating region D. The second load b1 may be a constant value regardless of the engine speed, but 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.

[0033] Furthermore, in this embodiment, if 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.

[0034] 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 the ignition timing advance can be achieved immediately, there is a time lag in increasing the 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 compared to 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 the same effect as acceleration retard control. In other words, by strengthening the rotation of the sub-chamber 6, acceleration retard 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.

[0035] The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. Accordingly, the scope of the present invention is indicated by the claims rather than by the foregoing description, and all modifications within the meaning and scope of equivalence to the claims are intended to be included. 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, and the rotation of the sub-chamber 6 may 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 may be controlled using an electromagnet or hydraulics. [Explanation of Symbols]

[0036] 1. Internal combustion engine 2 Cylinder heads 3 Cylinder block 4 pistons 5. Main combustion chamber 6 Antechamber 7 Lower Head 8 Upper head 9 recesses 10 Through holes 11. Sealing member 12 Spark plugs 13, 14 Ring groove 15, 16 Seal groove 17 Main body 18 Flange section 19 nozzles 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

1. 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.

2. 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.

3. 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.

4. 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.

5. 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.

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