JP6379998B2 - Thermal control device for internal combustion engine - Google Patents

Description

  The present invention relates to a thermal control device for an internal combustion engine for insulating a combustion chamber in a spark ignition type internal combustion engine.

  Generally, it is said that the cooling loss of an internal combustion engine is about 20 to 30% of the energy of the input fuel, and it is important to reduce the cooling loss in order to improve fuel consumption. Thus, conventionally, a technique for forming a heat insulating means in the combustion chamber has been proposed in order to reduce the cooling loss. For example, in Patent Document 1, water is jetted onto the piston crown surface in the combustion chamber to form a water film, and the heat insulation effect of the water film suppresses the heat of burned gas from escaping from the combustion chamber to the outside. .

JP 2008-175078 A

  In a spark ignition type internal combustion engine, flame propagation occurs due to a continuous combustion reaction of the air-fuel mixture, and the temperature of the combustion chamber wall surface becomes the highest when the flame due to flame propagation reaches the combustion chamber wall surface. Therefore, it is important that a heat insulating means is formed to protect the wall surface at this time.

  Further, in Patent Document 1, the heat insulating means is limited to a water film, but in order to effectively insulate the entire combustion chamber wall surface, a gas that does not burn between the burned gas of the air-fuel mixture and the combustion chamber wall surface. It is conceivable to provide a (wall protective gas) layer. Since the wall surface protective gas layer is mixed with the air-fuel mixture by the air flow in the combustion chamber, the period during which the wall surface protective gas layer is formed is limited.

  However, in Patent Document 1, even if the water vapor layer in which the water film is vaporized is considered to correspond to the wall surface protective gas layer, the relationship between the state of flame propagation and the formation period of the water vapor layer is not considered at all. It does not draw out the heat insulation effect. For this reason, depending on the technique of Patent Document 1, the cooling loss is insufficiently reduced.

  The present invention has been made in view of the above points, and an object thereof is to provide a thermal control device for an internal combustion engine that can sufficiently reduce a cooling loss.

  The present invention is a thermal control device for an internal combustion engine for insulating a combustion chamber in a spark ignition internal combustion engine, and includes a fluid injection valve that injects a non-combustion fluid along a wall surface of the combustion chamber, and a non-combustion fluid. While the wall surface protective gas layer is formed along the wall surface of the combustion chamber, the fluid injection valve is based on the operating state of the internal combustion engine so that the flame caused by the combustion of the air-fuel mixture in the combustion chamber reaches the wall surface protective gas layer. An injection control unit for controlling the injection timing of

  In the above configuration, when the non-combustion fluid injected to the fluid injection valve is a liquid, the non-combustion fluid is vaporized by receiving heat from the wall surface of the combustion chamber, and forms a wall surface protective gas layer along the wall surface of the combustion chamber To do. When the non-combustion fluid injected into the fluid injection valve is a gas, the non-combustion fluid is injected along the wall surface of the combustion chamber to form a wall surface protective gas layer.

In the above configuration, the state of flame propagation in the combustion chamber, the time required for the non-combustion fluid to form the wall surface protective gas layer, the period during which the wall surface protective gas layer is formed, etc. It depends on. Therefore, the injection control unit controls the injection timing of the fluid injection valve based on the operating state of the internal combustion engine, so that the flame is protected against the wall surface protective gas while the wall surface protective gas layer is formed along the combustion chamber wall surface. Trying to reach the layer. That is, the wall surface protective gas layer can protect the wall surface of the combustion chamber from the flame by setting a limited period from the formation of the wall surface protective gas layer to the collapse thereof according to the state of flame propagation.
Therefore, according to the present invention, the wall surface protective gas layer insulates between the wall surface of the combustion chamber and the flame, thereby suppressing an increase in the temperature of the wall surface of the combustion chamber and sufficiently reducing the cooling loss. is there.

1 is a schematic diagram showing an engine system to which a heat control device according to a first embodiment of the present invention is applied. It is a schematic diagram of the combustion chamber for demonstrating cooling loss. It is a schematic diagram of the combustion chamber for demonstrating the principle of heat insulation of the wall surface protective gas layer of this invention. (A)-(c) is a typical cross-sectional view of a combustion chamber which shows a mode that the wall surface protective gas layer by 1st Embodiment of this invention is formed. It is a schematic diagram which shows the flow of the non-combustion fluid in a combustion chamber. (A)-(c) is a typical cross-sectional view of a combustion chamber which shows the mode of collapse of a wall surface protective gas layer. (A)-(e) is a typical cross-sectional view of the combustion chamber which shows the formation timing of the wall surface protective gas layer by 1st Embodiment of this invention, and the mode of flame propagation. It is a graph which shows the time change of cylinder pressure, and the injection timing of the non-combustion fluid by 1st Embodiment. It is a flowchart for demonstrating the method of determining the injection timing of a noncombustible fluid. It is a typical cross-sectional view of a combustion chamber showing a case where the injection timing of the non-combustible fluid is early. It is a typical cross section of a combustion chamber which shows the case where the injection timing of a non-combustible fluid is late. It is a schematic diagram which shows the engine to which the thermal control apparatus by 2nd Embodiment of this invention is applied. (A) (b) is a typical longitudinal cross-sectional view of a combustion chamber which shows a mode that the wall surface protective gas layer by 2nd Embodiment of this invention is formed. It is a graph which shows the time change of cylinder pressure, and the injection timing of the non-combustion fluid by other embodiment. It is a graph which shows the time change of cylinder pressure, and the injection timing of the non-combustion fluid by other embodiment. It is a typical cross-sectional view of a combustion chamber for showing a fluid injection valve by other embodiments of the present invention. It is a typical cross-sectional view of a combustion chamber for showing a fluid injection valve by other embodiments of the present invention. It is a schematic diagram of the combustion chamber for showing the fluid injection valve by other embodiment of this invention. It is a typical cross-sectional view of a combustion chamber for showing a fluid injection valve by other embodiments of the present invention. It is a typical longitudinal cross-sectional view of the combustion chamber for showing the fluid injection valve by other embodiment of this invention. (A)-(b) is a typical longitudinal cross-sectional view of the combustion chamber for demonstrating the case where the nonflammable fluid by other embodiment of this invention is gas.

  Hereinafter, a thermal control device for an internal combustion engine according to the present invention will be described with reference to the drawings. Hereinafter, in a plurality of embodiments, the same numerals are given to the substantially same composition, and explanation is omitted.

(First embodiment)
[Engine system configuration]
First, a schematic configuration of the engine system will be described with reference to FIG. As shown in FIG. 1, the engine system 10 includes an engine 13 as a spark ignition type internal combustion engine and a heat control device 40. The engine 13 is, for example, a multi-cylinder engine such as four cylinders, and FIG. 1 shows a cross section of one cylinder. The configuration described below is similarly provided to other cylinders (not shown).

  The engine 13 combusts an air-fuel mixture of air supplied from the intake manifold 15 via the throttle valve 14 and fuel injected from the fuel injection valve 16 in the combustion chamber 17, and causes the piston 18 to explode due to the explosive force at the time of combustion. Reciprocate. The reciprocating motion of the piston 18 is converted into a rotational motion by the crankshaft 19 and output. Combustion gas generated by the combustion is released into the atmosphere via the exhaust manifold 20.

  The combustion chamber 17 is partitioned by a cylindrical cylinder 21, and a crown surface 181 of the piston 18 and a lower surface 221 of the cylinder head 22 disposed in the opening thereof. An intake valve 23 is provided at the intake port of the cylinder head 22 that is the inlet of the combustion chamber 17, and an exhaust valve 24 is provided at the exhaust port of the cylinder head 22 that is the outlet of the combustion chamber 17. The intake valve 23 and the exhaust valve 24 are opened and closed by a valve drive mechanism 25.

  The air-fuel mixture in the combustion chamber 17 is ignited by a spark generated between the electrodes of the spark plug 7. In the present embodiment, the electrode of the spark plug 7 is disposed at the center of the combustion chamber 17 in the radial direction, and the air-fuel mixture is ignited therefrom to start combustion. That is, flame propagation occurs starting from the radial center of the combustion chamber 17. The radial center of the combustion chamber 17 is the radial center of the cylindrical cylinder 21.

  The electronic control unit (hereinafter referred to as “ECU”) 32 is constituted by a microcomputer comprising a CPU, a ROM, a RAM, an input / output port and the like, and includes a crank angle sensor 35, a cam angle sensor 36, a water temperature sensor 37, a throttle opening degree. Signals from various sensors such as the sensor 38 and the intake pressure sensor 39 are input. The ECU 32 controls the operating state of the engine 13 by controlling the throttle valve 14, the fuel injection valve 16, the ignition circuit unit 31, and the like based on detection signals from these various sensors.

  The heat control device 40 applied to the engine 13 of the present embodiment is a device for insulating the combustion chamber 17 so that heat generated by the combustion of the air-fuel mixture in the combustion chamber 17 does not escape to the outside of the combustion chamber 17. The fluid injection valve 41 capable of injecting the non-combustion fluid into the combustion chamber 17 and the injection control unit 45 for controlling the operation of the fluid injection valve 41 are provided. The injection control unit 45 is configured in the ECU 32, for example. The non-combustion fluid injected by the fluid injection valve 41 forms a wall surface protective gas layer to be described later in the combustion chamber 17.

[Wall protection gas layer]
The detail of the wall surface protective gas layer of this embodiment is demonstrated below. In the drawings used in the following description, the combustion chamber 17 is schematically shown as a cylindrical shape.

First, the principle of heat insulation by the wall surface protective gas layer 51 will be described with reference to FIGS.
FIG. 2 is a view showing the combustion chamber 17 in a state where the air-fuel mixture M is sucked. If the air-fuel mixture M burns without the wall surface protective gas layer 51 being formed, the heat generated by the air-fuel mixture M burning (heat of burned gas) is transferred to the outside via the wall surface 26 of the combustion chamber 17. Escape (see arrow in Fig. 2).

  Therefore, in the present embodiment, the wall surface protective gas layer 51 is formed along the wall surface 26 by injecting the non-combustion fluid along the wall surface 26 of the combustion chamber 17. Thereby, the air-fuel mixture layer 52 in which the air-fuel mixture M is stratified is arranged near the center of the combustion chamber 17 (see FIG. 3). The wall surface protective gas layer 51 is an inert gas layer that does not burn, and serves to keep the heat of the burned gas inside the combustion chamber 17 in order to maintain a lower temperature than the burned gas.

Next, the state from the formation of the wall surface protective gas layer 51 to the collapse will be described with reference to FIGS.
The wall surface 26 of the combustion chamber 17 corresponds to the inner wall of the cylinder 21, the crown surface 181 of the piston 18, and the lower surface of the cylinder head 22 (including the lower surfaces of the intake valve 23 and the exhaust valve 24). Below, the case where the wall surface protective gas layer 51 is formed along the part (referred to as the side wall surface 261) corresponding to the inner wall of the cylinder 21 in the wall surface 26 of the combustion chamber 17 will be described as an example.

In addition, the non-combustion fluid of the present embodiment is an inert fluid that is liquid before injection and becomes gas after injection into the combustion chamber 17. The non-combustion fluid is preferably one that is vaporized immediately after being injected into the combustion chamber 17, and is, for example, a liquid having a boiling point lower than the wall temperature of the combustion chamber 17 (for example, water) or liquefied CO ₂ . Hereinafter, the non-combustion fluid in a liquid state is referred to as non-combustion liquid L.

First, as shown in FIG. 4A, the fluid injection valve 41 injects a liquid non-combustion liquid L into the combustion chamber 17 in a state where the air-fuel mixture M is sucked. For example, the ejection port 410 of the fluid injection valve 41 is disposed on one end side of the combustion chamber 17, and the non-combustion liquid L spirals on the side wall surface 261 by injecting the non-combustion liquid L toward the side wall surface 261. (See the arrow in FIG. 5), and travels through the side wall surface 261 more than once (see FIG. 4B).
The injected non-combustion liquid L is vaporized by receiving heat from the side wall surface 261, a wall surface protective gas layer 51 is formed along the side wall surface 261, and an air-fuel mixture layer 52 is stratified inside (FIG. 4). (See (c)).

The formed wall surface protective gas layer 51 is mixed with the air-fuel mixture layer 52 by an air flow in the combustion chamber 17 or the like, and collapses with the passage of time.
As shown in FIG. 6A, when the formation of the wall surface protective gas layer 51 is completed by completing the vaporization of the non-combustion liquid L, the wall surface protective gas layer 51 has the largest thickness, and the heat insulating effect is The biggest. As time passes, mixing of the wall surface protective gas layer 51 and the gas mixture layer 52 proceeds, and the thickness of the wall surface protective gas layer 51 decreases (see FIG. 6B). Thereby, the heat insulation effect of the wall surface protective gas layer 51 becomes small. In the figure, the mixed portion of the wall surface protective gas layer 51 and the air-fuel mixture layer 52 is denoted by the symbol D. Finally, the wall surface protective gas layer 51 and the gas mixture layer 52 are completely mixed, and the wall surface protective gas layer 51 is completely collapsed (see FIG. 6C).

  A period during which the wall surface protective gas layer 51 is formed, that is, a period from when the formation of the wall surface protective gas layer 51 is completed until it completely collapses is referred to as a gas layer formation period Tg. The gas layer formation period Tg is a limited period, and corresponds to a crank angle range of 20 degrees in this embodiment. When the flame reaches the wall surface protective gas layer 51 during the gas layer formation period Tg, the wall surface protective gas layer 51 exhibits a heat insulating effect.

[Non-combustion liquid injection timing]
In the present embodiment, when the heat insulating effect of the wall surface protective gas layer 51 is the largest, that is, when the formation of the wall surface protective gas layer 51 is completed, the injection timing of the non-combustion liquid L so that the flame reaches the wall surface protective gas layer 51. To control. The injection timing of the non-combustion liquid L will be described with reference to FIGS. 7 (a) to 7 (e) and FIG. FIGS. 7A to 7E sequentially show how the flame propagates in the combustion chamber 17, and FIG. 8 shows the time variation of the in-cylinder pressure of the engine 13.

  First, at the ignition timing t1 immediately after the piston 18 reaches top dead center, the air-fuel mixture M is ignited at the radial center of the combustion chamber 17 (see FIG. 7A). After ignition, the flame F due to the combustion of the air-fuel mixture M propagates toward the side wall surface 261 (see FIG. 7B).

  Thereafter, the fluid injection valve 41 starts to inject the non-combustion liquid L into the combustion chamber 17 at the injection start timing t2 (see FIG. 7C), and a necessary amount of the non-combustion liquid L is injected at the injection completion timing t3. The injection is completed (see FIG. 7 (d)). The non-combustion liquid L injected into the combustion chamber 17 starts to vaporize.

Thereafter, the vaporization of the non-combustion liquid L is completed at the vaporization completion time t4, whereby the wall surface protective gas layer 51 is formed and the arrangement of the gas mixture layer 52 is completed. Further, the flame F reaches the formation region of the wall surface protective gas layer 51 at the flame arrival time t5. In this embodiment, since the vaporization completion time t4 and the flame arrival time t5 coincide with each other, the flame F reaches the wall surface protective gas layer 51 at the same time as the wall surface protective gas layer 51 is formed (see FIG. 7E). ).
Note that the gas constituting the air-fuel mixture layer 52 is replaced by the burned gas from the air-fuel mixture by combustion, but in the present specification, it is referred to as the air-fuel mixture layer 52 as it is for explanation.

  Here, a period from the ignition timing t1 to the flame arrival time t5 is referred to as a flame propagation period Tfp, and a period from the injection start timing t2 to the vaporization completion timing t4 is referred to as a stratification formation period Ts. The stratification period Ts corresponds to a period obtained by combining the injection period Tinj from the injection start timing t2 to the injection completion timing t3 and the vaporization period Tev from the injection completion timing t3 to the vaporization completion timing t4.

  Next, the method by which the injection control unit 45 of this embodiment determines the injection timing of the fluid injection valve 41 is controlled with reference to the flowchart shown in FIG. FIG. 9 is a flowchart showing a processing procedure of injection control by the injection control unit 45, and the processing is repeatedly executed at a predetermined cycle (for example, every predetermined crank or every predetermined time).

First, in S1, the engine 13 operating state information including the load (fuel amount used) of the engine 13, the rotational speed, the intake air amount, the intake air temperature, the intake air pressure, and the like is acquired. As the driving state information, for example, detection values input from various sensors provided in the engine 13 and estimation values estimated based on the detection values are used.
Next, in S2, the ignition timing t1 and the required fluid amount G of the non-combustion liquid L are set based on the values acquired in S1. The ignition timing t1 is set to, for example, MBT (Minimum spark advance for Best Torque), which is a timing at which the engine 13 generates maximum torque.

  In S3, the flame propagation period Tfp is calculated based on the operation state information and the fluid amount G, and the flame arrival time t5 when the flame propagation period Tfp has elapsed from the ignition timing t1 is calculated. The vaporization completion time t4 is set at the same time as the calculated flame arrival time t5. The vaporization completion time t4 corresponds to “a time when the formation of the wall surface protective gas layer 51 is completed”.

  In S4, the vaporization period Tev is calculated based on various information such as the time history of the temperature and pressure of the combustion chamber 17 at the flame arrival time t5, the operation state information, and the fluid amount G of the non-combustion liquid L, and the vaporization completion time is calculated. An injection completion timing t3 obtained by subtracting the vaporization period Tev from t4 is calculated.

  In S5, the temperature and pressure time history of the combustion chamber 17 at the injection completion timing t3, the operating state information, the fluid amount G of the non-combustion liquid L, the injection pressure of the fluid injection valve 41, the total area of the injection holes, and the number of injection holes Based on such various information, the injection period Tinj is calculated, and the timing obtained by subtracting the injection period Tinj from the injection completion timing t3 is set as the injection start timing t2.

  In addition, a map etc. can be utilized for calculation of the vaporization period Tev in S4 and calculation of the injection period Tinj in S5. For example, a time history is recorded in advance for the temperature and pressure of the combustion chamber 17. Further, the vaporization period Tev and the injection period Tinj for various information including the time history of the temperature and pressure of the combustion chamber 17 and the operation state information are acquired in advance by a test, and the relationship is recorded in a map or the like. Then, the vaporization period Tev and the injection period Tinj can be respectively calculated with reference to a time history and a map regarding the temperature and pressure of the combustion chamber 17.

  The vaporization period Tev calculated in S4 can be adjusted to shorten the period by making the non-combustion liquid L finer by increasing the injection pressure or by increasing the mixture temperature by changing the ignition timing. The injection period Tinj calculated in S5 can be adjusted to shorten the period by increasing the injection pressure. The “injection timing” described in the claims includes an injection start timing t2 and an injection completion timing t3.

  As described above, the injection start timing t2 and the injection completion timing t3 corresponding to the operating conditions of the engine 13 are appropriately set. By controlling the fluid injection valve 41 according to this setting, the time when the formation of the wall surface protective gas layer 51 is completed coincides with the time when the flame F reaches the wall surface protective gas layer 51.

[effect]
(1) The heat control device 40 of the present embodiment is for insulating the combustion chamber 17 in the engine 13, and includes a fluid injection valve 41 that injects the non-combustion liquid L along the wall surface 26 of the combustion chamber 17, While the wall surface protective gas layer 51 by vaporization of the non-combustion liquid L is formed along the wall surface 26 of the combustion chamber 17, the flame F generated by the combustion of the air-fuel mixture in the combustion chamber 17 reaches the wall surface protective gas layer 51. And an injection control unit 45 that controls the injection timing of the fluid injection valve 41 based on the operating state of the engine 13.

  In the above configuration, the state of flame propagation in the combustion chamber 17, the time required for the non-combustion liquid L to form the wall surface protective gas layer 51, and the period during which the wall surface protective gas layer 51 is formed are as follows. Varies depending on operating conditions. Therefore, the injection control unit 45 controls the injection timing of the fluid injection valve 41 based on the operation state of the engine 13, so that the wall surface protective gas layer 51 is formed along the wall surface 26 of the combustion chamber 17. The flame F reaches the wall surface protective gas layer 51. That is, the wall surface protective gas layer 51 can protect the wall surface 26 from the flame F by setting a limited period from the formation of the wall surface protective gas layer 51 to the collapse thereof according to the state of flame propagation. .

  If the injection timing is too early, as shown in FIG. 10, the formation of the wall surface protective gas layer 51 is completed when the flame F has not yet reached. For this reason, the flame F reaches the side wall surface 261 after the wall surface protective gas layer 51 collapses. On the other hand, when the injection timing is too late, the flame F reaches the side wall surface 261 when the non-combustion liquid L has just been injected and the wall surface protective gas layer 51 has not yet been formed, as shown in FIG. In these cases, the wall surface 26 cannot be sufficiently insulated from the flame F.

  In contrast, in the present embodiment, the wall surface protective gas layer 51 insulates between the side wall surface 261 of the combustion chamber 17 and the flame F, thereby suppressing the temperature of the side wall surface 261 of the combustion chamber 17 from rising. In addition, the cooling loss can be sufficiently reduced.

(2) In the present embodiment, the wall injection gas layer 51 is formed by the fluid injection valve 41 injecting the non-combustion liquid L and the injected non-combustion liquid L is vaporized. According to such a form, compared with the case where the fluid injection valve 41 injects a gas non-combustion fluid, the work for compressing the gas is not required, and the fuel efficiency is improved.

(3) The non-combustion liquid L is liquefied carbon dioxide or a liquid having a boiling point lower than the temperature of the wall surface 26 of the combustion chamber 17 during operation of the engine 13. For this reason, the non-combustion liquid L becomes a gas immediately after injection, and the time required until the wall surface protective gas layer 51 is formed can be shortened. Therefore, before the formation of the wall surface protective gas layer 51 is completed, the vaporized non-combustion liquid L can be prevented from being mixed with the air-fuel mixture M.

(4) In the present embodiment, the injection control unit 45 performs fluid injection so that the time when the formation of the wall surface protective gas layer 51 is completed coincides with the time when the flame F reaches the wall surface protective gas layer 51. The injection timing of the valve 41 is controlled.
According to the above configuration, since the flame F reaches the wall surface protective gas layer 51 when the wall surface protective gas layer 51 is the thickest, the wall surface protective gas layer 51 can more effectively protect the side wall surface 261 from the flame F. it can. Thereby, a cooling loss can be reduced more.

[Second Embodiment]
A heat control device according to a second embodiment of the present invention and an engine 33 to which the heat control device is applied will be described with reference to FIGS. 12 and 13. In the first embodiment, the case where the side wall surface 261 is protected among the wall surfaces 26 of the combustion chamber 17 is described. In the second embodiment, the case where all the wall surfaces 26 of the combustion chamber 17 are protected is described. .

  First, as shown in FIG. 12, the engine 33 according to the second embodiment is provided with a sub chamber 47 for the combustion chamber 17, and the spark plug 7 and the fuel injection valve 16 are provided for the sub chamber 47. Yes. When the spark plug 7 ignites the fuel injected from the fuel injection valve 16, the burned gas jet J is injected from the sub chamber 47 into the combustion chamber 17. The burned gas jet J starts the combustion of the air-fuel mixture from the center of the combustion chamber 17.

  As shown in FIG. 13, two fluid injection valves 42 are arranged in addition to the fluid injection valve 41 with respect to the combustion chamber 17. The fluid injection valve 41 injects the non-combustion liquid L onto the side wall surface 261 of the combustion chamber 17, and the two fluid injection valves 42 inject the non-combustion liquid L onto the piston crown surface 181 and the cylinder head lower surface 221, respectively. Thereby, the wall surface protective gas layer 51 is formed so as to cover the air-fuel mixture layer 52 as a whole.

  Note that when the radial distance A from the center of the combustion chamber 17 to the wall surface protective gas layer 51 and the distance B in the direction perpendicular to the radial direction are different, the flame arrival time t5 in each direction is different, so the fluid injection For the valves 41 and 42, the optimal injection timing may be controlled.

  According to the second embodiment, the wall surface protective gas layer 51 can more effectively protect the wall surface 26 from the flame F. Thereby, the cooling loss can be further reduced.

[Other Embodiments]
(A) Injection timing In the above embodiment, the vaporization completion timing t4 and the flame arrival timing t5 are made to coincide with each other. However, the present invention is not limited to this, and as illustrated in FIG. The arrival time t5 should just overlap. If the time when the wall surface protective gas layer 51 completely collapses is t6, then t4 ≦ t5 <t6, (t6−t4) = Tg.
In this case, the vaporization completion timing t4 can be set between the flame arrival timing t5 and the flame arrival timing t5 after the timing obtained by subtracting the gas layer formation period Tg, and the injection is performed based on the set vaporization completion timing t4. What is necessary is just to obtain the completion time t3 and the injection start time t2.

  For example, when the gas layer formation period Tg corresponds to a crank angle range of 20 degrees, the flame F reaches the wall surface protective gas layer 51 from the vaporization completion time t4 until the crankshaft 19 rotates 20 degrees. The gas layer formation period Tg is not limited to a range of 20 degrees in crank angle, and is appropriately determined according to the settings of the engines 13 and 33.

(A) Multi-stage injection As illustrated in FIG. 15, the injection control unit 45 may cause the fluid injection valves 41 and 42 to inject non-combustible fluid in a multi-stage every predetermined period (for example, every predetermined crank angle). In FIG. 15, the injection is performed at t21 to t25, which are times indicated by white arrows. From the vaporization completion timings t41 to t45 following the injection start timings t21 to t25 to the wall surface protective gas layer collapse timings t61 to t66, respectively, the gas layer formation period Tg is reached. By setting the injection start times t21 to t25 so that the gas layer formation periods Tg are continuous, the wall surface protective gas layer 51 can be formed continuously. Therefore, even if the flame arrival time t5 slightly deviates, the flame F can reach the wall surface protective gas layer 51 while the wall surface protective gas layer 51 is formed, and the effect of further reducing the cooling loss can be achieved. can get.

(C) Fluid injection valve The configuration and arrangement of the fluid injection valves 41 and 42 are not limited to those shown in the above embodiment.
For example, as shown in FIG. 16, a plurality of fluid injection valves 41 that inject the non-combustion liquid L onto the side wall surface 261 of the combustion chamber 17 may be arranged. Here, the plurality of fluid injection valves 41 are preferably arranged so that their positions are symmetrical with respect to the combustion chamber 17.
As shown in FIGS. 17 and 18, the fluid injection valve 41 has a plurality of injection ports, and the non-combustion liquid L may spread on the side wall surface 261 of the combustion chamber 17 in multiple directions. .
Furthermore, as shown in FIG. 19, a plurality of fluid injection valves 41 arranged in the combustion chamber 17 may each have a plurality of injection ports. Here, the plurality of fluid injection valves 41 may be arranged rotationally symmetrically with respect to the center of the combustion chamber 17.
With the configuration shown in FIGS. 16 to 19, the injection period Tinj can be shortened, and the wall surface protective gas layer 51 can be formed more quickly. Moreover, the thickness of the wall surface protective gas layer 51 to be formed can be made uniform, whereby the progress of the collapse of the wall surface protective gas layer 51 can be suppressed.

  As shown in FIG. 20, a plurality of injection ports are formed in the fluid injection valve 42, and one fluid injection valve 42 injects the non-combustion liquid L simultaneously onto the piston crown surface 181 and the cylinder head lower surface 221. May be. Further, the fluid injection valve 41 for injecting the non-combustion liquid L on the side wall surface 261 is not arranged, but only the fluid injection valve 42 for injecting the non-combustion liquid L on the piston crown surface 181 and the cylinder head lower surface 221 is arranged. Also good.

(D) Non-combustion fluid The non-combustion fluid injected by the fluid injection valve is not limited to a liquid, but may be a gas. For example, as shown in FIG. 21, the fluid injection valve 43 directly injects the non-combustion gas P into the adjacent region of the wall surface 26. According to this, it is easy to form the wall surface protective gas layer 51 in the target region. The non-combustion gas P may be any inert gas that does not burn in the air.

  The present invention is not limited to the embodiments described above, and can be implemented in various forms without departing from the spirit of the invention.

13, 33 ... Engine (internal combustion engine)
17 ... Combustion chamber 26, 261, 221, 181 ... Wall surface 41, 42, 43 ... Fluid injection valve 45 ... Injection control part 51 ... Wall surface protective gas layer

Claims (5)

An internal combustion engine thermal control device (40) for insulating a combustion chamber (17) in a spark ignition internal combustion engine (13),
Fluid injection valves (41, 42, 43) for injecting non-combustion fluid along the wall surfaces (26, 261, 221, 181) of the combustion chamber;
While the wall surface protective gas layer (51) by the non-combustion fluid is formed along the wall surface, the internal combustion engine is configured such that a flame caused by combustion of the air-fuel mixture in the combustion chamber reaches the wall surface protective gas layer. An injection control unit (45) for controlling the injection timing of the fluid injection valve based on the operating state of
The non-combustion fluid injected by the fluid injection valve is a liquid;
The non-combustion fluid forms the wall protective gas layer by being vaporized after being injected,
The injection control unit calculates a time (t5) when the flame reaches the wall surface protective gas layer based on the operating state information of the internal combustion engine and a necessary fluid amount (G) of the non-combustion fluid, A wall surface protective gas layer formation completion time (t4) is set so that the wall surface protective gas layer formation completion time (t4) coincides with the time when the flame reaches the wall surface protective gas layer (t5). An internal combustion engine thermal control device that controls the injection timing of the fluid injection valve.   The non-combustion fluid injected by the fluid injection valve is liquefied carbon dioxide or a liquid having a boiling point lower than the temperature of the wall surface of the combustion chamber during operation of the internal combustion engine. 2. A heat control apparatus for an internal combustion engine according to 1. The internal combustion engine is configured so that combustion of the air-fuel mixture starts from the center of the combustion chamber,
The said fluid injection valve injects the said non-combustion fluid along the cylinder wall surface (261) which divides the said combustion chamber, a piston crown surface (11), and a cylinder head lower surface (221). Or a heat control apparatus for an internal combustion engine according to 2 ; The internal combustion engine thermal control according to any one of claims 1 to 3 , wherein the injection control unit controls the fluid injection valve to inject the non-combustion fluid in multiple stages at predetermined intervals. apparatus. The thermal control device for an internal combustion engine according to any one of claims 1 to 4 , wherein a plurality of the fluid injection valves are arranged so that their positions are symmetrical with respect to the combustion chamber.

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