JP7268512B2 - engine combustion chamber structure - Google Patents

Description

The technology disclosed herein relates to an engine combustion chamber structure.

Patent Literature 1 describes a compression ignition engine that burns part of the air-fuel mixture by compression ignition. In this engine, an ignition device ignites the air-fuel mixture. Flame propagation combustion starts, and the heat generated by the flame propagation combustion self-ignites the unburned air-fuel mixture.

The engine is equipped with a water injection device for injecting water into the combustion chamber. When the water injection device injects water into the combustion chamber, the inside of the combustion chamber is cooled. This engine can suppress the occurrence of abnormal combustion.

Japanese Patent No. 6477849

In addition to the purpose of suppressing abnormal combustion as described above, the inventors of the present application have increased the amount of working gas by injecting water (and steam) into the combustion chamber, thereby increasing the piston work of the engine and improving the torque. We focused on the point of In order to keep the thermal efficiency of the engine high, it is advantageous to inject high-temperature water into the combustion chamber so that the water is vaporized without using combustion heat.

Therefore, the inventors of the present application attached a temperature raising unit to the engine to raise the temperature of the water. The temperature raising unit has a main body portion having a number of passages through which water flows, and a mounting portion to which a heating device is attached. Raise

However, according to the study by the inventors of the present application, even if the temperature-raising portion injects the water whose temperature has been raised into the combustion chamber, the effect of improving the torque of the engine is lower than expected.

The technology disclosed herein improves the torque of the engine by injecting the water heated by the temperature raising unit into the combustion chamber.

As a result of investigations by the inventors of the present application on the above-described problem, it was found that the temperature raising unit could not sufficiently heat the water flowing through some of the passages. When cold water is injected into the combustion chamber, part of the combustion heat is consumed by the cold water. As a result, the torque improvement effect of the engine was lower than expected. The technology disclosed herein has been completed based on the new findings of the inventors of the present application.

Specifically, the technology disclosed herein relates to the combustion chamber structure of an engine. The combustion chamber structure of this engine is
a combustion chamber formed by a cylinder provided in the engine and a piston that reciprocates within the cylinder;
an ignition device disposed on the ceiling of the combustion chamber;
a water injection device for injecting water into the combustion chamber through an injection hole facing the combustion chamber;
The water injection device injects water when the combustion chamber is in a compression stroke,
The water injection device has a temperature raising unit that raises the temperature of the water by the heat of the heating device,
The temperature raising unit has a plurality of passages through which the water flows, and the plurality of passages are formed in the temperature raising unit on an attachment side to which the heating device is attached,
A non-forming portion in which the passage is not formed is provided on the non-mounting side of the temperature raising portion.

The mounting side in the temperature raising section has a short distance from the heating device. The temperature raising part can sufficiently heat water flowing through the passage formed on the attachment side. The water flowing through the passage becomes hot.

The distance from the heating device is long on the non-mounting side of the temperature raising section. Even if the passage is formed on the side opposite to the installation side, the temperature raising portion may not be able to sufficiently heat the water flowing through the passage. In the above configuration, the non-formation portion is provided on the side opposite to the mounting side. The non-formed portion has no passageway. The temperature raising part has a passage in a place where heat can be applied sufficiently. Injection of low-temperature water into the combustion chamber is suppressed.

In the combustion chamber construction described above, only sufficiently heated water is injected into the combustion chamber. In this specification, "water" includes water vapor, which is a gas. If water vapor is injected into the combustion chamber, the combustion heat is not consumed by water, or is suppressed, so injecting water vapor into the combustion chamber is advantageous for improving the thermal efficiency of the engine. . Injecting hot water into the combustion chamber increases the torque of the engine without reducing the thermal efficiency of the engine.

The heating device has a heat pipe that sends heat of the exhaust gas of the engine to the temperature raising unit,
The water injection device has a water injection valve,
The temperature raising unit is interposed between the water injection valve and the combustion chamber, each passage extends in a direction from the water injection valve toward the combustion chamber,
The heat pipe may be attached to a side portion of the temperature raising section in a direction orthogonal to the passage.

By doing so, the heat pipe recovers the exhaust heat of the engine, and the heat is used by the temperature raising section to heat the water injected by the water injection valve before it is supplied into the combustion chamber. Improves engine thermal efficiency.

The temperature raising unit has a main body portion in which the passage is formed, a mounting portion to which the heat pipe is mounted, and a heat transfer portion connecting the main body portion and the mounting portion,
The heat transfer section may have a width equal to or greater than half the length of the passage.

This reduces the thermal resistance of the heat transfer section, so that the temperature raising section can efficiently heat the water flowing through the passage with the heat of the heat pipe.

The combustion chamber structure of the previous engine includes a water supply device for supplying water to the water injection device,
The water supply device is
a condenser for condensing water in the exhaust gas of the engine;
a water tank for storing water condensed by the condenser;
and a water pump for pressurizing the water in the water tank and supplying it to the water injection device.

By doing so, the passenger does not have to fill the water tank with water to be injected into the combustion chamber. Also, since the water pump pressurizes the water, it can be injected into the high pressure combustion chamber during the compression stroke. At least part of the injected water is vaporized by boiling under reduced pressure. The amount of heat required for vaporizing water can be reduced.

The combustion chamber structure of the engine comprises an ignition device arranged in the ceiling of the combustion chamber,
said piston having a cavity recessed from its top surface,
The water injection device injects water toward the cavity at a timing when an extension line of an axis of at least a part of the nozzle holes intersects the cavity,
The ignition device may be located outside the cavity relative to the direction perpendicular to the axis of the cylinder.

The inventors of the present application have found that when water is injected into the combustion chamber of an engine for the purpose of improving torque, the combustion stability deteriorates. This is because a large amount of water must be injected into the combustion chamber in order to increase the torque of the engine. That is, when the amount of water injected into the combustion chamber increases, the concentration of water near the ignition device increases, making it difficult for the ignition device to ignite the air-fuel mixture.

On the other hand, with the above-described structure, even if water is injected into the combustion chamber, the ignition device can stably ignite the air-fuel mixture.

That is, the water injection device injects water toward the cavity so that the water is confined or nearly confined to the area within the cavity. Diffusion of water in the combustion chamber can be suppressed.

The igniter is located outside the cavity. Since diffusion of injected water into the combustion chamber is suppressed, the concentration of water in the vicinity of the ignition device is kept low. As a result, the ignition device can stably ignite the air-fuel mixture. The combustion stability of the engine is enhanced.

In this specification, the term "area within the cavity" refers to the area inside the cavity that is recessed from the upper surface of the piston, and the projected plane of the opening of the cavity projected onto the ceiling of the combustion chamber in the axial direction of the cylinder. It means the combined area of the area up to the opening of the cavity. As used herein, the term “outside cavity region” means a region other than the aforementioned “inside cavity region”.

The cavity may have a bottom against which the water injected by the water injection device hits, and a hoisting portion that rolls up the water spreading along the bottom toward the water injection device.

According to studies by the inventors of the present application, it has been found that spraying water toward a cavity having a roll-up portion suppresses the spread of water to a region outside the cavity. The vicinity of the igniter is kept low in concentration of water because the water will fit, or nearly fit, into the area within the cavity. Injecting water into the combustion chamber also allows the igniter to ignite the mixture.

The water injection device may inject water from the early stage to the middle stage of the compression stroke.

As described above, if the temperature of the water injected into the combustion chamber is increased, the water can be vaporized without using combustion heat, which is advantageous for improving the thermal efficiency of the engine. The pressure in the combustion chamber is relatively low during the period from the early period to the middle period of the compression stroke. When the pressure in the combustion chamber is low, the boiling point temperature of water is lowered, so even if the temperature of the water is low, the vaporized water can be injected into the combustion chamber. In other words, by injecting water during the period from the early stage to the middle stage of the compression stroke, the amount of heat required for heating water can be saved. This configuration is advantageous for improving the fuel efficiency of an automobile equipped with the engine.

The "early period" and "middle period" of the compression stroke may be the "early period" and the "middle period" when the period of the compression stroke is equally divided into the "early period", the "middle period" and the "late period".

The amount of water injected by the water injection device is less when the load of the engine is low than when the load is high,
The water injection device may delay the start timing of injection when the amount of water injected is small compared to when the amount of water injected is large.

Injecting water into the combustion chamber early in the compression stroke increases the compression resistance of the piston. A later water injection timing is advantageous for improving the thermal efficiency of the engine. When the water injection amount is small and the water injection period is short, the water injection device delays the injection start timing. Since the compression resistance of the piston is lowered, it is advantageous for improving the thermal efficiency of the engine.

In addition, when the injection amount of water increases, the period during which the water injection device injects water becomes longer. When the water injection amount is large, the water injection device advances the start timing of water injection. The water injection device can finish water injection by the middle of the compression stroke. As a result, as described above, the amount of heat required for heating water can be saved.

The combustion chamber structure of the engine includes a fuel injection valve that injects fuel,
The fuel injection valve may be arranged in an intake port that communicates with the combustion chamber.

By doing so, a homogeneous air-fuel mixture can be formed in the combustion chamber. Even if water is injected into the combustion chamber, the ignition device can stably ignite the air-fuel mixture.

The engine may be a compression ignition gasoline engine in which at least part of the air-fuel mixture is combusted by compression ignition.

Even if water exists in the combustion chamber, the air-fuel mixture can be stably burned by compression ignition.

As described above, the combustion chamber structure of the engine can improve the torque of the engine by injecting heated water into the combustion chamber using the temperature raising section.

FIG. 1 is a diagram illustrating an engine to which the combustion chamber structure disclosed herein is applied. FIG. 2 is a plan view of the combustion chamber. FIG. 3 is a cross-sectional view showing an enlarged combustion chamber. FIG. 4 is a diagram showing a configuration example of the water supply device and the water injection valve. 5 is a cross-sectional view taken along line VV of FIG. 3. FIG. 6 is a VI-VI end view of FIG. 3. FIG. The upper diagram of FIG. 7 is a diagram illustrating a jet of water when the density of nozzle holes is low, and the lower diagram is a diagram of a jet of water when the density of nozzle holes is high. FIG. 8 is a diagram illustrating changes in water concentration distribution in the combustion chamber. FIG. 9 is a diagram illustrating changes in in-cylinder pressure (upper diagram) and changes in in-cylinder temperature (lower diagram) when water is injected into the combustion chamber and when water is not injected into the combustion chamber. FIG. 10 is a block diagram illustrating the configuration of an engine control device. FIG. 11 is a diagram exemplifying a control map regarding the injection amount of water. FIG. 12 shows examples of fuel injection timing, water injection timing, and ignition timing when the engine is under high load (upper diagram), medium load (middle diagram), and low engine load (lower diagram). It is a figure to do.

Hereinafter, embodiments of the combustion chamber structure of the engine will be described with reference to the drawings. The combustion chamber structure described here is exemplary.

FIG. 1 illustrates an engine 1 to which the combustion chamber structure disclosed herein is applied. The engine 1 is a four-stroke reciprocating engine that operates by repeating an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke in a combustion chamber 11 . The engine 1 is installed in a four-wheeled vehicle. The automobile runs as the engine 1 operates. The fuel of the engine 1 is gasoline in this configuration example. The fuel may be liquid fuel containing at least gasoline. The fuel may be gasoline, including, for example, bioethanol.

The engine 1 has a cylinder block 12 and a cylinder head 13 mounted on the cylinder block 12 . A plurality of cylinders 14 are formed inside the cylinder block 12 . The engine 1 is a multi-cylinder engine. 1 and 3 only one cylinder 14 is shown.

A piston 3 is inserted in each cylinder 14 . The piston 3 reciprocates inside the cylinder 14 . Although not shown, the piston 3 is connected to the crankshaft via a connecting rod.

Piston 3 forms combustion chamber 11 with cylinder 14 and cylinder head 13 . The term "combustion chamber" is used in a broad sense. In other words, the "combustion chamber" means the space formed by the piston 3, the cylinder 14 and the cylinder head 13 regardless of the position of the piston 3.

An intake port 15 is formed in the cylinder head 13 for each cylinder 14 . The intake port 15 communicates with the combustion chamber 11 . An intake valve 21 is arranged in the intake port 15 . The intake valve 21 opens and closes the intake port 15 . The intake valve 21 is opened and closed by the rotation of the cam 23 . Incidentally, the valve gear for opening and closing the intake valve 21 is of a direct-acting type in the illustrated example. The configuration of the valve train of the intake valve 21 is not limited to a specific type.

The cylinder head 13 is also formed with an exhaust port 16 for each cylinder 14 . The exhaust port 16 also communicates with the combustion chamber 11 . An exhaust valve 22 is arranged in the exhaust port 16 . The exhaust valve 22 opens and closes the exhaust port 16 . The exhaust valve 22 is opened and closed by rotation of the cam 24 . The valve gear that opens and closes the exhaust valve 22 is a direct-acting type in the illustrated example. The configuration of the valve train of the exhaust valve 22 is not limited to a specific type.

An intake pipe 61 is connected to one side of the engine 1 (the left side in FIG. 1). The intake pipe 61 communicates with the intake port 15 . Gas introduced into the combustion chamber 11 flows through the intake pipe 61 . Although not shown, the intake pipe 61 is provided with a throttle valve 66 (see FIG. 10). In the following description, the side of the engine 1 to which the intake pipe 61 is connected may be referred to as the "intake side".

An exhaust pipe 62 is connected to the other side of the engine 1 (the right side in FIG. 1). The exhaust pipe 62 communicates with the exhaust port 16 . Exhaust gas discharged from the combustion chamber 11 flows through the exhaust pipe 62 . A catalytic converter 63 is arranged in the exhaust pipe 62 . The catalytic converter 63 has, for example, a three-way catalyst. Catalytic converter 63 cleans the exhaust gas. In the following description, the side of the engine 1 to which the exhaust pipe 62 is connected may be referred to as the "exhaust side."

An injector 64 is attached to the cylinder head 13 for each cylinder 14 . The injector 64 is arranged in the intake port 15 . Injector 64 injects fuel into intake port 15 . Although detailed illustration is omitted, the injector 64 is, for example, a multi-orifice fuel injection valve having a plurality of orifices. It should be noted that the mounting position of the injector 64 shown in FIG. 1 is an example. The injector 64 may be arranged in the combustion chamber 11 instead of being arranged in the intake port 15 . Injector 64 may directly inject fuel into combustion chamber 11 .

A spark plug 65 is attached to the cylinder head 13 as shown in FIG. A spark plug 65 is attached to each cylinder 14 . The ignition plug 65 is attached to the ceiling portion 111 of the combustion chamber 11 . Although not shown in detail, the spark plug 65 has an electrode facing the combustion chamber 11 . Spark discharge between the electrodes causes the spark plug 65 to forcibly ignite the air-fuel mixture in the combustion chamber 11 . The spark plug 65 may perform plasma discharge. The ignition plug 65 is an example of an ignition device. The spark plug 65 is arranged at an intermediate position between the intake side and the exhaust side of the engine 1, as indicated by the dashed line in FIG. The spark plug 65 is also arranged on the front side of the engine 1 with respect to the central axis X of the cylinder 14, as also shown in FIG. The spark plug 65 is positioned near the central axis X of the cylinder 14 . As an example, the spark plug 65 is arranged straight along the axis of the cylinder 14 .

When the ignition plug 65 forcibly ignites the air-fuel mixture, the air-fuel mixture starts SI (Spark Ignition) combustion due to flame propagation. The temperature in the combustion chamber 11 increases due to the heat generated by the SI combustion and/or the pressure in the combustion chamber 11 increases due to flame propagation. ) to burn. This engine 1 is a compression ignition gasoline engine in which at least part of the air-fuel mixture is combusted by compression ignition.

(Configuration for injecting water into the combustion chamber)
This engine 1 includes a water injection device 4 and a water supply device 5 . The water injection device 4 injects water into the combustion chamber 11 . The water supply device 5 supplies water to the water injection device 4 . This engine 1 increases the working gas by injecting water into the combustion chamber 11, thereby increasing the piston work of the engine 1. FIG. Further, the engine 1 cools the interior of the combustion chamber 11 by injecting water into the combustion chamber 11 to suppress the occurrence of abnormal combustion.

A large amount of water must be injected into the combustion chamber 11 in order to improve the torque of the engine 1 . However, according to the study by the inventors of the present application, it was found that injection of a large amount of water into the combustion chamber 11 deteriorates the combustion stability. This is because when the amount of water injected into the combustion chamber 11 increases, the concentration of water near the spark plug 65 increases, making it difficult for the spark plug 65 to ignite the air-fuel mixture.

Therefore, the water injection device 4 is configured so that the spark plug 65 can stably ignite the air-fuel mixture even if a large amount of water is injected into the combustion chamber 11 .

The water injection device 4 is attached to the cylinder head 13 as shown in FIG. A water injection device 4 is attached to each cylinder 14 . The water injection device 4 is attached to the ceiling portion 111 of the combustion chamber 11 . The water injection device 4 is arranged at an intermediate position between the intake side and the exhaust side of the engine 1, as indicated by the dashed line in FIG. The water injection device 4 is also arranged on the rear side of the engine 1 with respect to the central axis X of the cylinder 14 . The water injection device 4 is positioned away from the center of the combustion chamber 11 . The water injection device 4 is separated from the spark plug 65 . The water injection device 4 is tilted with respect to the axis of the cylinder 14 . More specifically, the water injection device 4 is tilted in a direction approaching the central axis X of the cylinder 14 from top to bottom. The water injection device 4 may be attached straight to the cylinder head 13 along the axis of the cylinder 14 . The details of the configuration of the water injection device 4 will be described later.

The water supply device 5 is connected to the water injection device 4 . The water supply device 5 condenses water in the exhaust gas and supplies the condensed water to the water injection device 4 . The water supply device 5 has a condenser 51, a water tank 52, a water pump 53, and a heat exchanger 54, as shown in FIGS. The water supply device 5 includes a heating device for heating water.

The condenser 51 condenses water in the exhaust gas extracted from the exhaust pipe 62 . Condenser 51 is connected to extraction pipe 55 . The extraction pipe 55 connects the exhaust pipe 62 and the condenser 51 . The water tank 52 stores water condensed by the condenser 51 . The water tank 52 is connected to the water injection device 4 through a first supply pipe 56 . The water pump 53 and heat exchanger 54 are interposed in the middle of the first supply pipe 56 . The water pump 53 sucks water in the water tank 52 and discharges it to the heat exchanger 54 .

The heat exchanger 54 is attached to the exhaust pipe 62 . The heat exchanger 54 exchanges heat between the exhaust gas and water. The water is heated by exhaust heat from the engine 1 . The high-temperature, high-pressure water pressurized by the water pump 53 and heated by the heat exchanger 54 is sent to the water injection device 4 .

The water injection device 4 has a water injection valve 41, a temperature raising section 42, a nozzle section 43, and a heat pipe 44, as illustrated in FIG. 3 shows only the tip portion of the water injection valve 41. As shown in FIG. The water injection device 4 also includes a heating device for heating the water.

The water injection valve 41 receives a signal from an ECU (Engine Control Unit) 10, which will be described later, and injects water into the combustion chamber 11, as shown in FIG. The water injection valve 41 has a high temperature chamber 411 and a low temperature chamber 412 . A partition is provided between the high temperature room 411 and the low temperature room 412 . The above-described first supply pipe 56 is connected to the high temperature room 411 . The high-temperature room 411 is supplied with high-temperature, high-pressure water pressurized by the water pump 53 and heated by the heat exchanger 54 . A second supply pipe 57 is connected to the low temperature room 412 . A second supply pipe 57 branches off from the first supply pipe 56 between the water pump 53 and the heat exchanger 54 . The second supply pipe 57 bypasses the heat exchanger 54 . The low-temperature room 412 is supplied with low-temperature, high-pressure water pressurized by the water pump 53 and bypassing the heat exchanger 54 . Low-temperature, high-pressure water is a control fluid for opening and closing the needle valve 413, as will be described later.

A needle valve 413 closes an injection port 414 provided in the high temperature chamber 411 . The tip of needle valve 413 opens and closes injection port 414 . The proximal end of needle valve 413 receives the pressure of the water in low temperature chamber 412 . The needle valve 413 closes the injection port 414 by receiving back pressure. A control valve 415 is provided in the low temperature room 412 . Control valve 415 is, for example, a solenoid valve. The control valve 415 opens and closes upon receiving a control signal from the ECU 10 . When the control valve 415 is opened, the water in the cold room 412 is released to the atmosphere. The pressure inside the low-temperature chamber 412 is lowered, and the needle valve 413 is lifted so as to open the injection port 414 (see the white arrow in FIG. 4). When needle valve 413 opens injection port 414 , high-temperature, high-pressure water in high-temperature chamber 411 is injected from injection port 414 . Part of the water injected from the injection port 414 is vaporized by boiling under reduced pressure.

Solenoid valves have relatively low heat resistance. As previously mentioned, not heating the control fluid supplied to the cold chamber 412 improves the reliability of the control valve 415 . Also, by not heating the control fluid that is released to the atmosphere, the heat energy loss of the engine 1 can be reduced.

The temperature raising part 42 of the water injection device 4 is interposed between the water injection valve 41 and the combustion chamber 11 as illustrated in FIG. The temperature raising unit 42 raises the temperature of the water injected by the water injection valve 41 before supplying it to the combustion chamber 11 . The water injection device 4 can supply only vaporized water to the combustion chamber 11 due to the above-described boiling under reduced pressure and the temperature increase of the temperature raising unit 42 . By supplying the vaporized water to the combustion chamber 11, the water can be vaporized and expanded without consuming the combustion heat generated when the air-fuel mixture is burned. This configuration is advantageous for improving the thermal efficiency of the engine 1 .

The temperature raising portion 42 has an attachment portion 421 , a body portion 422 and a heat transfer portion 423 . The body portion 422 is attached to the tip of the water injection valve 41 . The heat transfer portion 423 continues to the side portion of the main body portion 422 . The attachment portion 421 is connected to the main body portion 422 with the heat transfer portion 423 interposed therebetween.

A tip portion of the heat pipe 44 is attached to the attachment portion 421 . Although not shown, the base end of the heat pipe 44 is attached to the exhaust pipe 62 . The heat pipe 44 sends the heat of the exhaust gas to the temperature raising section 42 .

The body portion 422 is a substantially cylindrical block. The body portion 422 stores the heat of the heat pipe 44 . As illustrated in FIG. 5, a large number of passages 45 are formed in the central portion of the body portion 422 . Water flows in each passage 45 . Body portion 422 heats the water flowing through passage 45 . As shown in FIG. 3 , each passage 45 opens to the upper end surface and the lower end surface of the body portion 422 respectively. Each passage 45 extends straight in the axial direction of the body portion 422 from the upper end surface to the lower end surface of the body portion 422 . Since the water injection device 4 is tilted with respect to the axis of the cylinder 14 as described above, each passage 45 is also tilted with respect to the axis of the cylinder 14 .

The plurality of passages 45 are arranged at regular intervals. Here, the plurality of passages 45 are not arranged symmetrically with respect to the center of the body portion 422 . The body portion 422 has a non-forming portion 46 in which the passage 45 is not formed. The non-formation portion 46 is the non-mounting side when the body portion 422 is divided into a side (mounting side) to which the heat pipe 44 is mounted via the heat transfer portion 423 (mounting side) and the opposite side (counter-mounting side). provided in part of the The non-formed portion 46 is substantially fan-shaped in the configuration example of FIG. The passage 45 is provided on the attachment side of the main body portion 422 and on a part of the opposite side of the attachment side.

The non-forming portion 46 is separated from the heat pipe 44 . The heat of the heat pipe 44 is less likely to be transmitted to the non-forming portion 46 . Even if the passage 45 is formed in the non-forming portion 46, the body portion 422 cannot provide sufficient heat to the water flowing therethrough, and the water may not evaporate. When non-vaporized water is injected into the combustion chamber 11, the water takes away combustion heat. In this case, the thermal efficiency of the engine 1 is lowered.

On the other hand, if the body portion 422 is provided with the non-forming portion 46 that does not form the passage 45, the body portion 422 can sufficiently apply heat to the water passing through the passage 45, and vaporize all the water. becomes possible. Injection of non-vaporized water into the combustion chamber 11 is suppressed. A decrease in the thermal efficiency of the engine 1 is suppressed, and the torque of the engine 1 is improved.

The heat transfer portion 423 connects the body portion 422 and the attachment portion 421 . The heat transfer portion 423 is formed to connect the main body portion 422 and the mounting portion 421 at the shortest distance. The length L of the heat transfer portion 423 is short. Moreover, the heat transfer portion 423 has a predetermined width W in the direction in which the passage 45 of the body portion 422 extends. Width W is greater than or equal to half the length of passageway 45 . Since the length L of the heat transfer portion 423 is short and the width W thereof is wide, the thermal resistance of the heat transfer portion 423 is low. The heat transfer portion 423 can efficiently transfer the heat of the heat pipe 44 to the main body portion 422 .

The water injection valve 41 is connected to the body portion 422 of the temperature raising portion 42 via the connection portion 47 . A recess 471 recessed from the lower end (that is, the lower end in FIG. 3) is formed in the connecting portion 47 . A tip of the water injection valve 41 is connected to the recess 471 . Also, the upper end surface of the main body portion 422 is positioned within the recess 471 . The passage 45 is opened in the upper end surface of the body portion 422 as described above. The concave portion 471 functions as a distribution portion that distributes the water injected from the water injection valve 41 to the plurality of injection holes 432 .

The nozzle portion 43 of the water injection device 4 is attached to the lower end of the body portion 422 of the temperature raising portion 42 . The nozzle portion 43 has a concave portion 431 recessed from its upper end and a plurality of injection holes 432 . Each injection hole 432 is connected to the concave portion 431 and opens to the lower end surface of the nozzle portion 43 . All of the water coming out of the passage 45 of the body portion 422 once enters the recess 431 and is distributed to the plurality of injection holes 432 .

A lower end surface of the nozzle portion 43 corresponds to the injection surface 433 of the water injection device 4 . A plurality of injection holes 432 are opened in the injection surface 433 as described above. The injection surface 433 faces the inside of the combustion chamber 11 at the ceiling portion 111 of the combustion chamber 11 . As shown in FIG. 2, substantially the entire injection surface 433 is located at the same position as the cavity 31 described later with respect to the direction perpendicular to the axis of the cylinder 14 . In other words, the injection surface 433 is included in the region 33 inside the cavity, which will be described later.

As illustrated in FIG. 6 , in this configuration example, the nozzle portion 43 has 12 injection holes 432 . The number of injection holes 432 can be any number. The multiple nozzle holes 432 are parallel to each other. The plurality of injection holes 432 are arranged symmetrically with respect to the center of the nozzle portion 43 . The plurality of injection holes 432 are arranged at approximately equal intervals. Here, the center-to-center distance P between adjacent injection holes 432 is 5 mm or less. As an example, the diameter φ of each nozzle hole 432 is φ=1.5 mm and the center-to-center distance P of the nozzle holes is P=2.5 mm.

The water injection device 4 may be arranged such that the nozzle portion 43 is omitted and the lower end surface of the main body portion 422 faces the ceiling portion 111 of the combustion chamber 11 .

A cavity 31 is formed in the upper surface of the piston 3 . The cavity 31 has a circular shape in plan view, as illustrated in FIGS. The center of the circle of the cavity 31 is positioned on the center line between the intake side and the exhaust side of the cylinder 14 (see one-dot chain line in FIG. 2). The cavity 31 is located on the rear side of the engine 1 with respect to the center axis X of the cylinder 14 . The cavity 31 faces the water injection device 4 in the axial direction of the cylinder 14 .

In the illustrated example, the diameter of the circle of the cavity 31 is less than half the diameter of the piston 3 . Incidentally, the size of the cavity 31 can be set to an appropriate size. However, as will be described later, the cavity 31 has a function of suppressing the diffusion of water by containing the water injected into the combustion chamber 11 within the region 33 within the cavity. It is preferable that the cavity 31 is not too large.

The illustrated cavity 31 is composed of a bottom portion 311 and side walls 312 . Cavity 31 is relatively shallow. The bottom portion 311 has a circular shape in a plan view, and is composed of a flat surface extending in a direction orthogonal to the axis of the cylinder 14 . Side wall 312 continues to the periphery of bottom 311 . Bottom 311 and sidewall 312 are orthogonal. Side wall 312 is circumferential because bottom 311 is circular.

A heat shield layer 32 is provided on the upper surface of the piston 3 and the surface of the cavity 31 . The heat shield layer 32 has a lower thermal conductivity than the piston 3 . In addition, the piston 3 is made of, for example, aluminum or an aluminum alloy. The heat shield layer 32 suppresses heat transfer to the inside of the piston 3 . The cooling loss of the engine 1 can be reduced by providing the heat shield layer 32 . The heat shield layer 32 also has a smaller volumetric specific heat than the piston 3 . The heat capacity of the heat shield layer 32 is small. If the heat capacity of the heat shielding layer 32 is small, the temperature of the heat shielding layer 32 changes to follow the fluctuation of the temperature inside the combustion chamber 11 . When the air-fuel mixture burns in the combustion chamber 11, the temperature difference between the combustion temperature and the heat shield layer 32 becomes smaller, so that the heat transfer to the piston 3 can be further suppressed.

The heat shield layer 32 may be formed by applying a heat shield material to the upper surface of the piston 3 and the surface of the cavity 31 and curing the heat shield material by heat treatment. The heat shield material contains hollow particles such as glass balloons and a binder such as silicone resin. As described above, since the cavity 31 has a simple shape consisting of the bottom portion 311 and the side wall 312 , it is easy to apply the heat shielding material to the upper surface of the piston 3 and the surface of the cavity 31 . Formation of the heat shield layer 32 is relatively easy.

Although the details will be described later, the water injection device 4 injects water into the combustion chamber 11 when the combustion chamber 11 is in the compression stroke. Since the water supplied to the water injection device 4 is pressurized by the water pump 53 , it can be injected into the high-pressure combustion chamber 11 . As indicated by the dashed line in FIG. 3, the water injection device 4 directs the cavity 31 and injects water. At least part of the water injected by the water injection device 4 reaches the inside of the cavity 31 .

(Structure for Suppressing Diffusion of Water Injected into Combustion Chamber)
As described above, when a large amount of water is injected into the combustion chamber 11, the concentration of water near the spark plug 65 increases as the water diffuses into the combustion chamber 11, and the spark plug 65 stabilizes. It becomes impossible to ignite the air-fuel mixture.

As a result of investigations by the inventors of the present invention, the water injection form of the water injection device 4 that suppresses the diffusion of the water injected into the combustion chamber 11, the shape of the cavity 31, and combinations thereof were found. As a result, the technique disclosed herein has been completed.

As described above, the nozzle portion 43 of the water injection device 4 has a plurality of injection holes 432 . The multiple nozzle holes 432 are parallel to each other as shown in FIG. According to studies by the inventors of the present application, if the axes of the plurality of nozzle holes 432 are parallel or substantially parallel to each other, the water jet flow injected by the water injection device 4 is less likely to spread in a direction perpendicular to the injection direction. . Since the water injected into the combustion chamber 11 from the plurality of nozzle holes 432 travels in the same or substantially the same direction, the momentum of the water jets traveling in the direction increases. This is probably because, as the momentum increases, the force that draws the fluid around the jet of water injected by the water injection device 4 into the jet becomes stronger. In the illustrated water injection device 4, the axes of all twelve nozzle holes 432 are parallel or substantially parallel to each other. When the axes of all the orifices 432 are parallel or nearly parallel to each other, the momentum of the water is further increased, resulting in a stronger entrainment force of the fluid around the jet. Thus, the water injection device 4 can suppress diffusion of the water injected into the combustion chamber 11 .

According to studies by the inventors of the present application, if the angular difference between the axes of the injection holes 432 is within 5 degrees, the water jet flow injected by the water injection device 4 is less likely to spread in the direction perpendicular to the injection direction. and can suppress the diffusion of water. Incidentally, in the water injection device 4, the axes of all the injection holes 432 may not be parallel or substantially parallel to each other.

Also, as shown in FIG. 6, the center-to-center distance P of the plurality of nozzle holes 432 is relatively short. When the center-to-center distance P is short, the density of water injected by the water injection device 4 increases. If the water is denser, the increased momentum will result in a stronger entrainment force of the fluid around the jet. According to studies by the inventors of the present application, if the center-to-center distance P of the injection holes 432 is 5 mm or less, the entrainment force of the fluid around the jet becomes sufficiently strong, and the diffusion of water can be suppressed more effectively. It turns out that it can be done.

Cavity 31 has a flat bottom 311 and sidewalls 312 orthogonal to bottom 311, as shown in FIG. The water injection device 4 directs the inside of the cavity 31 and injects water. The water injected by the water injection device 4 reaches the bottom 311 of the cavity 31 . Water spreads along the bottom 311 in a direction perpendicular to the axis of the cylinder 14 and reaches the side wall 312 . The side walls 312 are perpendicular to the bottom 311 and thus roll up the water towards the water injection device 4 . Since the cavity 31 is relatively shallow, the sidewalls 312 can effectively roll up water. The side wall 312 of the cavity 31 prevents water from spreading to areas outside the cavity 31 . Side wall 312 is an example of a winding portion.

Since the cavity 31 has the roll-up portion, the water injected by the water injection device 4 can be contained in the region 33 in the cavity. As shown in FIG. 3, the "area within the cavity" includes the area inside the cavity 31 recessed from the upper surface of the piston 3 and the opening of the cavity 31 extending to the ceiling 111 of the combustion chamber 11. It means an area 33 obtained by combining the area from the projection plane projected in the direction to the opening of the cavity 31 . Further, the area outside the cavity 31 is an area other than the area 33 inside the cavity.

When the entrainment force of the jet of water injected by the water injection device 4 described above and the entrainment force of the water jet by the side wall 312 of the cavity 31 are combined, the water entrained by the side wall 312 is Pulled towards the jet. Spreading of the swirling water to the area outside the cavity 31 is suppressed. As a result, diffusion of water in the combustion chamber 11 is more effectively suppressed.

The spark plug 65 is offset in the direction perpendicular to the axis of the cylinder 14 with respect to the cavity 31 . Even if a large amount of water is injected into the combustion chamber 11, the concentration of water in the vicinity of the spark plug 65 is kept low due to the above-described suppression of water diffusion. The spark plug 65 enables stable ignition of the air-fuel mixture.

Here, FIG. 7 is a diagram comparing Comparative Example 71 in which the density of the injection holes 432 of the water injection device 4 is low and Example 72 in which the density of the injection holes 432 is high. Comparative Example 71 and Example 72 are examples in which the water injection device 4 directs the inside of the cavity 31 and injects water. 7 differs from the configuration example of FIG. 3 in that the water injection device 4 injects water along the axis of the cylinder 14, and the water collides with the bottom 311 of the cavity 31 in a direction perpendicular to the direction. do. In each of Comparative Example 71 and Example 72, the multiple injection holes 432 of the water injection device 4 are parallel to each other.

In Comparative Example 71, the center-to-center distance P of the injection holes 432 exceeds 5 mm. When the density of the injection holes 432 is low, the momentum of the jet of water injected by the water injection device 4 becomes small. The entanglement force described above becomes relatively weak. As a result, water picked up by the sidewalls 312 of the cavity 31 is not drawn towards the jet. As indicated by the arrows in the upper diagram of FIG. 7, in Comparative Example 71, the water swirled up by the side wall 312 of the cavity 31 spreads to the area outside the cavity.

In contrast, in Example 72, the center-to-center distance P of the injection holes 432 is 5 mm or less. Example 72 has a high density of injection holes 432 . When the density of the injection holes 432 is high, the momentum of the jet of water injected by the water injection device 4 is large, as described above, and the entrainment force described above is strong. As a result, water picked up by the side walls 312 of the cavity 31 is drawn towards the jet. As indicated by arrows in the lower diagram of FIG. 7, in Example 72, the water swirled up by the side wall 312 of the cavity 31 is contained in the region 33 within the cavity.

Thus, the water injection device 4 makes the plurality of injection holes 432 parallel or substantially parallel to each other and increases the density of the injection holes 432 , and the side wall 312 of the cavity 31 stirs up the water, thereby can be suppressed from diffusing.

Here, as indicated by the dashed line in FIG. 3, at least a portion of the injection hole 432 of the water injection device 4 points toward the side wall 312 of the cavity 31 at the timing of injecting water. Water reaching the center of the bottom 311 of the cavity 31 decelerates while spreading along the bottom 311 . If the flow velocity of the water is low when it reaches the side wall 312, it becomes difficult for the water to roll up.

When at least part of the injection hole 432 is directed toward the side wall 312 , at least part of the water injected by the water injection device 4 reaches the vicinity of the side wall 312 . The roll-up part 312 can roll up the water while the flow velocity of the water does not decrease. If at least a part of the nozzle hole 432 is directed toward the side wall 312 at the timing of jetting water, it is possible to effectively suppress the water from diffusing to the area outside the cavity.

When the direction of the axis of the injection hole 432 is inclined with respect to the axis of the cylinder 14 as in the configuration example shown in FIG. It changes according to the position of the piston 3. That is, when the timing at which the water injection device 4 injects water changes, the position where the water injected by the water injection device 4 reaches changes. The water injection device 4 may inject water toward the cavity 31 at the timing when the extension of the axis of at least some of the nozzle holes 432 intersects the cavity 31 .

Water diffusion can also be suppressed by the water injection device 4 injecting water during the compression stroke. During the compression stroke, the pressure inside the combustion chamber 11 is relatively high and the flow of gas inside the combustion chamber 11 is weaker than during the intake stroke. Injecting water into the combustion chamber 11 during the compression stroke suppresses diffusion of water due to gas flow in the combustion chamber 11 .

FIG. 8 illustrates simulation results of water concentration distribution in the combustion chamber structure of the example. FIG. 8 shows changes in water concentration distribution as the crank angle progresses. P81 in FIG. 8 shows the water concentration distribution at 60° bTDC (before Top Dead Center), which is immediately after the water injection device 4 completes water injection during the compression stroke, and P82 shows the concentration distribution at 45° bTDC. The concentration distribution of water is shown, P83 shows the concentration distribution of water at 10° bTDC, and P84 shows the concentration distribution of water at TDC. FIG. 8 is divided into a high water density area, a low water density area, and an intermediate water density area.

As indicated by P81, immediately after the water injection is completed, the concentration of water in the region on the rear side of the engine 1, including the cavity 31, is high, and the water concentration in the region on the front side of the engine 1, including the spark plug 65, is high. concentration is low. As the compression stroke progresses (P82 and P83), the water diffuses, so the area with high water concentration becomes smaller, but the area on the front side of the engine 1 remains low in water concentration. Wide diffusion of water in the combustion chamber 11 is suppressed. Then, as shown in P84, the concentration of water in the vicinity of the spark plug 65 is kept low even at TDC before and after the timing at which the spark plug 65 ignites. The spark plug 65 can stably ignite the air-fuel mixture.

Reference numeral 91 in FIG. 9 compares the change in cylinder pressure (solid line) when water is injected into the combustion chamber 11 and the change in cylinder pressure (broken line) when water is not injected into the combustion chamber 11. are doing. Reference numeral 92 in FIG. 9 compares the change in cylinder temperature when water is injected into the combustion chamber 11 (solid line) and the change in cylinder temperature when water is not injected into the combustion chamber 11 (broken line). are doing. The horizontal axis of FIG. 9 is the crank angle. By injecting water into the combustion chamber 11, the in-cylinder pressure increases due to an increase in the amount of working gas, as described above. By injecting water into the combustion chamber 11, the torque of the engine 1 is improved. Further, by injecting water into the combustion chamber 11, the temperature in the combustion chamber 11 is lowered. By injecting water into the combustion chamber 11, the occurrence of abnormal combustion can be suppressed.

The water injection device 4 and the water supply device 5 configured as described above heat water using the exhaust heat of the engine 1 and inject the vaporized water into the combustion chamber 11 . Since the exhaust loss of the engine 1 can be reduced, the thermal efficiency of the engine 1 is improved. Further, since the water supplied into the combustion chamber 11 is water extracted from the exhaust gas, the water injection device 4 and the water supply device 5 configured as described above allow the occupant to supply water for injection to the water tank. It also has the advantage that it is not necessary.

(Configuration of engine control device)
FIG. 10 exemplifies the configuration of the control device for the engine 1. As shown in FIG. A control device for the engine 1 includes an ECU 10 . The ECU 10 is a well-known microcomputer-based controller, and includes a central processing unit (CPU) 101 that executes programs, and a RAM (random access memory) or ROM (read only memory), for example. It has a memory 102 for storing programs and data, and an input/output bus 103 for inputting/outputting electrical signals.

Various sensors SW1 to SW3 are connected to the ECU 10 . The sensors SW1 to SW3 output signals to the ECU 10. FIG. The sensors include at least the following sensors.

The airflow sensor SW1 is arranged in the intake pipe 61 and measures the flow rate of air flowing through the intake pipe 61 . A crank angle sensor SW2 is attached to the engine 1 and measures the rotation angle of the crankshaft. The accelerator opening sensor SW3 is attached to an accelerator pedal mechanism (not shown) and measures the accelerator opening corresponding to the amount of operation of the accelerator pedal.

The ECU 10 determines the operating state of the engine 1 based on the signals from these sensors SW1 to SW3, and calculates control amounts for each device according to predetermined control logic. The control logic is stored in memory 102 . The control logic includes using the operational map stored in memory 102 to compute target and/or control variables.

The ECU 10 outputs an electric signal related to the calculated control amount to the injector 64 , the spark plug 65 , the throttle valve 66 and the water injection device 4 .

FIG. 11 illustrates a control map 110 relating to the injection amount of water. Control map 110 is stored, for example, in memory 102 . The injection amount of water is determined by the relationship between the rotation speed of the engine 1 and the load on the engine 1 . The ECU 10 grasps the rotation speed and load of the engine 1 based on the signals from the sensors SW1 to SW3, and determines the injection amount of water from the grasped rotation speed and load and the control map 110. FIG.

More specifically, the control map 110 illustrated in FIG. 11 is divided into three areas, a first area 1101, a second area 1102 and a third area 1103, with respect to the load of the engine 1. FIG. The second area 1102 is an area with a higher load than the first area 1101 . A third area 1103 is an area with a higher load than the first area 1101 and the second area 1102 . The first area 1101 roughly corresponds to the low load area, the second area 1102 roughly corresponds to the medium load area, and the third area 1103 roughly corresponds to the high load area. Here, the low load range, medium load range, and high load range may be the low load range, the medium load range, and the high load range, respectively, when the entire operating range of the engine 1 is divided into three equal parts with respect to the level of the load. .

The first area 1101 corresponds to the low load area, as described above. The first region 1101 extends from the lowest rotation speed to the highest rotation speed of the engine 1 . In the first region 1101, the injection amount of water is small. This is because the exhaust energy is low when the load of the engine 1 is low. That is, when the load of the engine 1 is low, it is not possible to sufficiently heat a large amount of water using exhaust heat.

A second region 1102 corresponds to a medium load region. A second region 1102 extends from the lowest rotation speed to the highest rotation speed of the engine 1 . In the second region 1102 , the injection amount of water is larger than that in the first region 1101 . As the load of the engine 1 increases, the exhaust energy increases, so the amount of water that can be heated using the exhaust heat of the engine 1 increases.

A third area 1103 corresponds to the high load area. A third region 1103 extends from the lowest rotation speed to the highest rotation speed of the engine 1 . In the third region 1103 , the injection amount of water is larger than the injection amount in the first region 1101 and the injection amount in the second region 1102 . Abnormal combustion is likely to occur in the high load region. By increasing the injection amount of water in the third region 1103, the torque of the engine 1 can be improved and the occurrence of abnormal combustion can be suppressed.

Here, the boundary between the second area 1102 and the third area 1103 is tilted in FIG. That is, when the rotation speed of the engine 1 is high, the second region 1102 spreads toward high load. When the rotation speed of the engine 1 is low, the third region spreads toward low loads. This is because as the rotation speed increases, the time interval for injecting water into the combustion chamber 11 becomes shorter, making it difficult to ensure sufficient time to heat the water. When the rotation speed of the engine 1 is high, by enlarging the second region 1102 where the injection amount of water is small, sufficiently heated water can be injected into the combustion chamber 11, and the torque of the engine 1 can be improved. be able to. When the rotation speed of the engine 1 is low, the amount of water injected into the combustion chamber 11 can be increased by enlarging the third region where the injection amount of water is large, and the torque of the engine 1 can be further improved. be able to. This is advantageous for improving the fuel efficiency of an automobile equipped with the engine 1 .

FIG. 12 illustrates timings of fuel injection, water injection, and ignition controlled by the ECU 10 . The horizontal axis of FIG. 12 is the crank angle. The double-headed arrow in FIG. 12 indicates the duration of injection.

The injector 64 of this engine 1 is arranged in the intake port 15 . The injector 64 injects fuel into the intake port 15 during the intake stroke. Fuel is introduced into the combustion chamber 11 along with the intake air. A homogeneous mixture is formed in the combustion chamber 11 . A homogeneous air-fuel mixture is advantageous for stable ignition by the spark plug 65 and stable compression ignition. When the load of the engine 1 is high, the injection amount of fuel increases. In the example of FIG. 12, the injector 64 injects fuel during high load P121 over substantially the entire period from the start to the end of the intake stroke.

After the intake stroke ends, the water injection device 4 injects water into the combustion chamber 11 in the subsequent compression stroke. When the load of the engine 1 is high, the injection amount of water is large (see FIG. 11). The period during which the water injection device 4 injects water is long. The water injection device 4 injects water into the combustion chamber 11 during the early to middle period of the compression stroke. The pressure in the combustion chamber 11 is low during the early to middle stages of the compression stroke. Even if the temperature of the water injected into the combustion chamber 11 is low, the water is vaporized. Since the pressure in the combustion chamber 11 is high in the latter half of the compression stroke, the water will not evaporate unless the temperature of the water injected into the combustion chamber 11 is high. Injecting water during the early to middle period of the compression stroke makes it possible to use the exhaust heat of the engine 1 to vaporize the water. This is advantageous for improving the thermal efficiency of the engine 1 .

In addition, the first half, middle half, and second half of the compression stroke are respectively defined as "first half", "middle half" and "late half" when the period of the compression stroke is divided equally into "first half", "middle half" and "late half". good too. The same applies to the early, middle, and late stages of the intake stroke described below.

When the load of the engine 1 is high, the spark plug 65 retards the ignition timing. The ignition plug 65 ignites after compression top dead center. As a result, the spark plug 65, which can suppress the occurrence of abnormal combustion, may ignite the air-fuel mixture within the period illustrated by the dashed arrow in FIG.

When the engine 1 is under medium load (P122), the fuel injection amount is smaller than during high load. The fuel injection period of the injector 64 is relatively short. The injector 64 injects fuel during a period including the middle of the intake stroke. The descending speed of the piston 3 is fast in the middle of the intake stroke. When fuel is injected in the middle of the intake stroke, the injected fuel diffuses and the mixture becomes homogeneous or nearly homogeneous. Note that the fuel injection timing when the engine 1 has a medium load may be set at an appropriate timing.

After the intake stroke ends, the water injection device 4 injects water into the combustion chamber 11 in the subsequent compression stroke. When the engine 1 is under medium load, the injection amount of water is smaller than during high load (see FIG. 11). The period during which the water injection device 4 injects water is relatively short. The water injection device 4 delays the injection start timing of water. If water is injected into the combustion chamber 11 at an early stage of the compression stroke, the compression resistance will increase due to the increase in working gas. By delaying the water injection start timing, an increase in compression resistance can be avoided. The thermal efficiency of the engine 1 is improved. The water injection device 4 also completes injection by the middle of the compression stroke, as at high load. This saves the amount of heat required to heat the water.

When the engine 1 is under medium load, the spark plug 65 advances the ignition timing more than during high load. As a result, the occurrence of abnormal combustion is suppressed, and the torque of the engine 1 is improved by optimizing the ignition timing. The spark plug 65 may ignite the air-fuel mixture within the period illustrated by the dashed arrow in FIG. 12 after compression top dead center.

When the engine 1 has a low load (P123), the fuel injection amount is smaller than that at medium load. The fuel injection period of the injector 64 is relatively short. The injector 64 injects fuel during a period including the middle of the intake stroke. This makes the air-fuel mixture homogeneous or nearly homogeneous. The fuel injection timing when the load of the engine 1 is low may be set to an appropriate timing.

After the intake stroke ends, the water injection device 4 injects water into the combustion chamber 11 in the subsequent compression stroke. When the engine 1 has a low load, the injection amount of water is smaller than when the engine 1 has a medium load (see FIG. 11). The period during which the water injection device 4 injects water is relatively short. The water injection device 4 further delays the water injection start timing. Thereby, an increase in compression resistance can be avoided. The water injector 4 also completes injection by the middle of the compression stroke, as at high and medium loads. This saves the amount of heat required to heat the water.

When the engine 1 is under low load, the spark plug 65 advances the ignition timing more than during medium load. As illustrated in FIG. 12, spark plug 65 may ignite the air-fuel mixture before top dead center of compression. By optimizing the ignition timing, the torque of the engine 1 can be improved.

The engine combustion chamber structure disclosed herein is not limited to application to the engine 1 having the configuration described above. The engine combustion chamber structure disclosed herein can be applied to engines of various configurations.

1 engine 11 combustion chamber 111 ceiling portion 14 cylinder 15 intake port 3 piston 31 cavity 311 bottom portion 312 side wall (winding portion)
32 heat shield layer 4 water injection device 41 water injection valve 42 temperature raising portion 421 mounting portion 422 body portion 423 heat transfer portion 432 injection hole 433 injection surface 44 heat pipe (heating device)
45 passage 46 non-formed portion 5 water supply device 51 condenser 52 water tank 53 water pump 54 heat exchanger (heating device)
62 exhaust pipe 64 injector (fuel injection valve)
65 spark plug (igniter)

Claims (10)

a combustion chamber formed by a cylinder provided in the engine and a piston that reciprocates within the cylinder;
an ignition device disposed on the ceiling of the combustion chamber;
a water injection device for injecting water into the combustion chamber through an injection hole facing the combustion chamber;
The water injection device injects water when the combustion chamber is in a compression stroke,
The water injection device has a temperature raising unit that raises the temperature of the water by the heat of the heating device,
The temperature raising unit has a plurality of passages through which the water flows, and the plurality of passages are formed in the temperature raising unit on an attachment side to which the heating device is attached,
A combustion chamber structure for an engine, wherein a non-forming portion in which the passage is not formed is provided on the non-mounting side of the temperature raising portion. In the engine combustion chamber structure according to claim 1,
The heating device has a heat pipe that sends heat of the exhaust gas of the engine to the temperature raising unit,
The water injection device has a water injection valve,
The temperature raising unit is interposed between the water injection valve and the combustion chamber, each passage extends in a direction from the water injection valve toward the combustion chamber,
The combustion chamber structure of the engine, wherein the heat pipe is attached to a side portion of the temperature raising portion in a direction orthogonal to the passage. In the engine combustion chamber structure according to claim 2,
The temperature raising unit has a main body portion in which the passage is formed, a mounting portion to which the heat pipe is mounted, and a heat transfer portion connecting the main body portion and the mounting portion,
The combustion chamber structure of an engine, wherein the heat transfer section has a width equal to or more than half the length of the passage. In the engine combustion chamber structure according to any one of claims 1 to 3,
A water supply device for supplying water to the water injection device,
The water supply device is
a condenser for condensing water in the exhaust gas of the engine;
a water tank for storing water condensed by the condenser;
and a water pump for pressurizing water in the water tank and supplying it to the water injection device. In the engine combustion chamber structure according to any one of claims 1 to 4,
An ignition device arranged on the ceiling of the combustion chamber,
said piston having a cavity recessed from its top surface,
The water injection device injects water toward the cavity at a timing when an extension line of an axis of at least a part of the nozzle holes intersects the cavity,
The combustion chamber structure of the engine, wherein the ignition device is installed at a position deviated from the cavity with respect to a direction orthogonal to the axis of the cylinder. In the engine combustion chamber structure according to claim 5,
The combustion chamber structure of an engine, wherein the cavity has a bottom portion on which the water injected by the water injection device hits, and a roll-up portion that rolls up the water spreading along the bottom portion toward the water injection device. In the engine combustion chamber structure according to any one of claims 1 to 6,
The engine combustion chamber structure, wherein the water injection device injects water from the early stage to the middle stage of the compression stroke. In the engine combustion chamber structure according to claim 7,
The amount of water injected by the water injection device is less when the load of the engine is low than when the load is high,
A combustion chamber structure of an engine, wherein the water injection device delays the start timing of injection when the injection amount of water is small compared to when the injection amount is large. In the engine combustion chamber structure according to any one of claims 1 to 8,
Equipped with a fuel injection valve that injects fuel,
The combustion chamber structure of an engine, wherein the fuel injection valve is disposed in an intake port that communicates with the combustion chamber. In the engine combustion chamber structure according to any one of claims 1 to 9,
A combustion chamber structure of an engine, wherein the engine is a compression ignition gasoline engine in which at least part of an air-fuel mixture is combusted by compression ignition.

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