TW202334546A - Pre-chamber combustion four-stroke engine - Google Patents

Abstract

A pre-chamber combustion four-stroke engine (1) does not comprise an ignition assistance device that assists in ignition of a gaseous mixture, but does comprise a pre-chamber (20) that is in communication with a main combustion chamber (2) via a plurality of communication holes (21), and that is configured so that a portion of a pre-chamber spark plug (23) is exposed to an internal space of the pre-chamber. A control device (70) controls an intake passage injection valve (8) that injects a fuel into an intake passage (5) so that, in at least a part of a low-load region, a gaseous mixture will have a first air-fuel ratio that allows treatment with a three-way catalyst after combustion or a second air-fuel ratio that is richer than the first air-fuel ratio. A cylinder head (10) comprises a cooling section (16) that accommodates a cooling medium that receives heat from an electrode section (24) of the pre-chamber spark plug and a pre-chamber wall section (22) in which the plurality of communication holes are formed. The following are each formed so as to be dispersed in a circumferential direction: a plurality of spark discharges (33) produced by the electrode section of the pre-chamber spark plug; the plurality of communication holes; a plurality of heat paths (14) from the electrode section of the pre-chamber spark plug to the cooling section; and a plurality of heat paths (15) from the pre-chamber wall section to the cooling section.

Description

auxiliary chamber combustion four-stroke engine

The invention relates to an auxiliary chamber combustion four-stroke engine having a main combustion chamber and an auxiliary chamber.

Conventionally, a sub-chamber combustion four-stroke engine having a main combustion chamber and a sub-chamber connected through a plurality of communication holes is known, for example, disclosed in Patent Document 1. The mixed gas inside the auxiliary chamber is ignited by the spark plug. The sub-chamber combustion four-stroke engine in Patent Document 1 does not have a sub-chamber fuel injection valve for injecting fuel into the sub-chamber, but has an intake passage injection valve for injecting fuel into the intake passage. The intake passage injection valve of Patent Document 1 is controlled to generate a stoichiometric or rich air-fuel ratio mixed gas in the main combustion chamber. The sub-chamber combustion four-stroke engine of Patent Document 1 has a cooling jacket (cooling section) on the cylinder head. Furthermore, the sub-chamber combustion four-stroke engine of Patent Document 1 has an auxiliary spark plug (ignition assist device) that assists the ignition of the mixed gas in the main combustion chamber. [Prior technical literature] [Patent Document]

[Patent Document 1] U.S. Patent No. 10612454

[Problem to be solved by the invention]

In the subchamber combustion four-stroke engine shown in Patent Document 1, the temperature around the plurality of communication holes and the electrode portion of the spark plug is relatively high. Their temperatures are particularly high under high loads, so pre-ignition is likely to occur near them. Furthermore, the so-called pre-ignition refers to the phenomenon that the mixed gas ignites itself before using the spark plug to ignite. If the cooling jacket volume is increased in order to suppress the occurrence of pre-ignition, the cylinder head will be enlarged.

An object of the present invention is to provide a sub-chamber combustion four-stroke engine that can suppress the enlargement of the cylinder head and suppress the occurrence of pre-ignition. [Technical means to solve problems]

A subchamber combustion four-stroke engine according to one embodiment of the present invention has the following configuration. The auxiliary chamber combustion four-stroke engine of the present invention has: a main combustion chamber connected to an intake passage and an exhaust passage; and a throttle valve that adjusts the amount of air sucked into the main combustion chamber through the intake passage. ; An intake passage injection valve, which injects gasoline fuel, alcohol fuel, or liquid fuel as a gasoline/alcohol mixed fuel into the interior of the above-mentioned intake passage; an auxiliary chamber, which is formed in a smaller volume than the above-mentioned main combustion chamber; A cylinder head whose internal space is connected to the internal space of the above-mentioned main combustion chamber through a plurality of communication holes, and a part of the spark plug in the auxiliary chamber is exposed to its internal space; and a control device that controls the above-mentioned intake passage injection valve and the above-mentioned auxiliary chamber Spark plug. The control device controls the intake passage injection valve so that the mixed gas mixed in the intake passage and the main combustion chamber becomes a combustion medium in at least a part of the low load area where the opening of the throttle valve is small. The first air-fuel ratio that can be processed by the three-way catalyst or the second air-fuel ratio that is richer than the above-mentioned first air-fuel ratio. The auxiliary chamber combustion four-stroke engine does not have any of the auxiliary chamber fuel injection valve for injecting fuel into the auxiliary chamber and the ignition assist device for assisting the ignition of the mixed gas in the auxiliary chamber or the main combustion chamber. The cylinder head has a cooling portion that accommodates a cooling medium that receives heat from the electrode portion of the spark plug in the sub-chamber and the sub-chamber wall portion in which the plurality of communication holes are formed. The electrode portion of the sub-chamber spark plug is formed to generate a plurality of spark discharges dispersedly in the circumferential direction of the electrode portion; the plurality of communication holes are formed to be dispersed in the circumferential direction; and the cylinder head is formed from the sub-chamber spark plug. A plurality of thermal paths from the electrode portion to the cooling portion and a plurality of thermal paths from the auxiliary chamber wall portion to the cooling portion are formed dispersedly in the circumferential direction.

According to this configuration, gasoline fuel, alcohol fuel, or liquid fuel that is gasoline/alcohol mixed fuel is injected into the intake passage from the intake passage injection valve. Furthermore, in at least part of the low load region, the mixed gas mixed in the intake passage and the main combustion chamber has a first air-fuel ratio or a second air-fuel ratio that is richer than the first air-fuel ratio. Therefore, even when the load is low, there are many places where the mixed gas is likely to catch fire in the internal space of the auxiliary chamber. Therefore, for example, when a spark plug having an electrode portion including a plurality of ground electrodes or annular ground electrodes arranged in the circumferential direction is used as a sub-chamber spark plug, at low load and high load, the spark plug in the sub-chamber The electrode part of the plug can generate a plurality of spark discharges dispersedly along the circumferential direction. By generating a plurality of spark discharges dispersedly in the circumferential direction, heat is generated dispersedly in the circumferential direction at the electrode portion of the sub-chamber spark plug. In addition, a plurality of communication holes are formed dispersedly in the circumferential direction. Therefore, heat is generated dispersedly in the circumferential direction in the sub-chamber wall portion where a plurality of communication holes are formed. In this way, heat is generated dispersedly in the circumferential direction at the electrode portion and the sub-chamber wall portion of the sub-chamber spark plug. Furthermore, the cylinder head is formed such that a plurality of thermal paths from the electrode portion of the sub-chamber spark plug to the cooling portion and a plurality of thermal paths from the sub-chamber wall portion to the cooling portion are formed dispersedly in the circumferential direction. Therefore, heat is particularly easy to move from the electrode portion and the sub-chamber wall portion of the sub-chamber spark plug where the temperature is relatively high to the cooling portion. Furthermore, assuming that an ignition auxiliary device such as a spark plug is installed in the main combustion chamber, since the temperature of the ignition auxiliary device is also high, it is difficult for heat to move from a position close to the ignition auxiliary device in the auxiliary chamber wall. By not providing an ignition assist device in the main combustion chamber, the uniformity in the circumferential direction of the ease of heat movement from the sub-chamber wall to the cooling section can be improved, so that heat can easily move from the sub-chamber wall. Furthermore, assuming that an ignition auxiliary device is provided in the auxiliary chamber, since the temperature of the ignition auxiliary device is also relatively high, it is difficult for heat to move from a position close to the ignition auxiliary device in the electrode portion of the spark plug in the auxiliary chamber. By not providing an ignition auxiliary device in the sub-chamber, the uniformity in the circumferential direction of the ease of heat movement from the electrode portion of the sub-chamber spark plug to the cooling portion can be further improved, so that heat can easily move from the electrode portion of the sub-chamber spark plug. In this way, heat can easily move from the electrode portion and the sub-chamber wall portion of the sub-chamber spark plug to the cooling portion, so that the cooling portion can be suppressed from being enlarged and the occurrence of pre-ignition can be suppressed. Furthermore, since the ignition assist device is not provided, the cylinder head can be further suppressed from being enlarged. Thereby, it is possible to suppress the cylinder head from being enlarged and to suppress the occurrence of pre-ignition.

The auxiliary chamber combustion four-stroke engine according to one embodiment of the present invention may also have the following configuration. Regarding the base material of the above-mentioned auxiliary chamber wall, its melting point is higher than that of the base material of the above-mentioned cylinder head, and the value obtained by multiplying the specific heat and specific gravity is higher than that of the base material of the above-mentioned cylinder head. The thermal conductivity is the same as or higher than that of chromium-based stainless steel. Chrome stainless steel.

According to this structure, the melting point of the base material of the auxiliary chamber wall is higher than that of the base material of the cylinder head. Therefore, the heat resistance of the sub-chamber wall portion can be ensured. In addition, the value obtained by multiplying the specific heat and specific gravity of the base material of the auxiliary chamber wall is higher than that of the base material of the cylinder head. Here, the value obtained by multiplying specific heat and specific gravity represents the heat capacity per unit volume. The greater the heat capacity per unit volume, the less likely the temperature will rise. By using a material with a higher heat capacity per unit volume than the base material of the cylinder head to form the base material of the auxiliary chamber wall, the rise in temperature of the auxiliary chamber wall is suppressed, and heat easily moves from the high-temperature auxiliary chamber wall to the In the cooling part of the cylinder head. In addition, the thermal conductivity of the base material of the auxiliary chamber wall is the same as or higher than that of chromium-based stainless steel. Therefore, heat moves from the sub-chamber wall portion to the cooling portion more easily. As a result, the occurrence of pre-ignition can be further suppressed.

The auxiliary chamber combustion four-stroke engine according to one embodiment of the present invention may also have the following configuration. Except for the spark plug of the above-mentioned auxiliary chamber, no protrusions are formed on the inner surface of the above-mentioned auxiliary chamber. The axial length of the spark plug of the above-mentioned auxiliary chamber in the internal space of the above-mentioned auxiliary chamber is less than the length of the internal space of the above-mentioned auxiliary chamber with the axis of the above-mentioned spark plug 2 times the maximum length in the orthogonal direction.

If protrusions are formed on the inner surface of the sub-chamber, heat is likely to accumulate in the protrusions. Since no protrusions are formed on the inner surface of the auxiliary chamber except for the spark plug of the auxiliary chamber, heat can easily move from the wall of the auxiliary chamber to the cooling part. Furthermore, the axial length of the spark plug in the internal space of the auxiliary chamber is less than twice the maximum length of the internal space of the auxiliary chamber in the direction orthogonal to the axial direction of the spark plug. Therefore, the capacity of the auxiliary chamber can be ensured, and the circumference of the auxiliary chamber can be made longer. This ensures more heat paths from the auxiliary chamber wall to the cooling part. Therefore, heat moves from the sub-chamber wall portion to the cooling portion more easily. As a result, the occurrence of pre-ignition can be further suppressed.

The auxiliary chamber combustion four-stroke engine according to one embodiment of the present invention may also have the following configuration. The auxiliary chamber wall is formed to protrude toward the internal space of the main combustion chamber, and the auxiliary chamber is formed so as to pass through the internal space of the auxiliary chamber without passing through the outer surface of the auxiliary chamber wall and is connected to the auxiliary chamber. When any plane orthogonal to the spark plug axis of the chamber spark plug divides the internal space of the above-mentioned auxiliary chamber into two spaces, the volume of the space close to the above-mentioned main combustion chamber among the above-mentioned two spaces is smaller than the above-mentioned two spaces. The volume of the space far away from the above-mentioned main combustion chamber.

According to this configuration, although the sub-chamber wall protrudes toward the internal space of the main combustion chamber, the protruding amount is small. Therefore, heat is less likely to be accumulated in the sub-chamber wall portion, and heat is easily transferred from the sub-chamber wall portion to the cooling portion. As a result, the occurrence of pre-ignition can be further suppressed.

The auxiliary chamber combustion four-stroke engine according to one embodiment of the present invention may also have the following configuration. A plane passing through the cooling part and orthogonal to the spark plug axial direction of the sub-chamber spark plug passes through the sub-chamber spark plug.

According to this structure, since the sub-chamber spark plug is close to the cooling part, the heat of the electrode part of the sub-chamber spark plug can easily move to the cooling part. As a result, the occurrence of pre-ignition can be further suppressed.

The auxiliary chamber combustion four-stroke engine according to one embodiment of the present invention may also have the following configuration. The internal space of the above-mentioned auxiliary chamber is a space surrounded by the auxiliary chamber component and the above-mentioned auxiliary chamber spark plug. The above-mentioned auxiliary chamber component, the cylinder head body partially exposed to the internal space of the above-mentioned main combustion chamber, and the above-mentioned auxiliary chamber spark plug are all Independent and including the above-mentioned auxiliary chamber wall.

According to this configuration, compared with the case where the internal space of the auxiliary chamber is a space surrounded by the auxiliary chamber member including the auxiliary chamber wall, the auxiliary chamber spark plug, and other members (such as the cylinder head body), it is possible to maintain the safety of the auxiliary chamber. The shape and size of the internal space can make the auxiliary chamber component elongate in the axial direction of the spark plug of the auxiliary chamber spark plug. Therefore, when a material that can easily move heat is used as the material of the sub-chamber member, heat can more easily move from the sub-chamber wall to the cooling portion. As a result, the occurrence of pre-ignition can be further suppressed.

The auxiliary chamber combustion four-stroke engine according to one embodiment of the present invention may also have the following configuration. A plane that passes through the cooling portion and is orthogonal to the axial direction of the spark plug in the auxiliary chamber passes through the auxiliary chamber member.

According to this structure, since the sub-chamber member is close to the cooling part, heat can more easily move from the sub-chamber wall to the cooling part. As a result, the occurrence of pre-ignition can be further suppressed.

The auxiliary chamber combustion four-stroke engine according to one embodiment of the present invention may also have the following configuration. A part of the inner surface of the cooling part is at least a part of the outer peripheral surface of the auxiliary chamber member.

According to this structure, the cooling medium flowing in the cooling part comes into contact with the outer peripheral surface of the sub chamber member. Therefore, heat moves from the sub-chamber wall portion to the cooling portion more easily. As a result, the occurrence of pre-ignition can be further suppressed.

The auxiliary chamber combustion four-stroke engine according to one embodiment of the present invention may also have the following configuration. The male thread formed in the sub-chamber spark plug meshes with the female thread formed in the sub-chamber member and comes into contact.

According to this structure, the contact area between the sub-chamber spark plug and the sub-chamber member is large. Therefore, heat easily moves from the auxiliary chamber spark plug to the auxiliary chamber components. Therefore, heat easily moves from the electrode part of the sub-chamber spark plug to the cooling part via the sub-chamber member. As a result, the occurrence of pre-ignition can be further suppressed.

The auxiliary chamber combustion four-stroke engine according to one embodiment of the present invention may also have the following configuration. A plane passing through the cooling portion and orthogonal to the spark plug axial direction of the sub-chamber spark plug passes through the portion where the male thread formed on the sub-chamber spark plug engages and contacts the female thread formed on the sub-chamber member.

According to this structure, since the sub-chamber member is close to the cooling part, heat can more easily move from the sub-chamber wall to the cooling part. Furthermore, since the contact portion formed by the thread between the sub-chamber spark plug and the sub-chamber member is close to the cooling portion, heat can more easily move from the electrode portion of the sub-chamber spark plug to the cooling portion via the sub-chamber member. As a result, the occurrence of pre-ignition can be further suppressed.

The auxiliary chamber combustion four-stroke engine according to one embodiment of the present invention may also have the following configuration. The outer peripheral surface of the above-mentioned auxiliary chamber member is in contact with the above-mentioned cylinder head body.

According to this structure, compared with the case where the outer peripheral surface of the sub-chamber member is not in contact with the cylinder head body, heat can more easily move from the sub-chamber wall to the cylinder head body. As a result, the occurrence of pre-ignition can be further suppressed.

The auxiliary chamber combustion four-stroke engine according to one embodiment of the present invention may also have the following configuration. A plane that passes through the internal space of the above-mentioned auxiliary chamber and is orthogonal to the axial direction of the spark plug of the above-mentioned auxiliary chamber passes through the portion of the outer peripheral surface of the above-mentioned auxiliary chamber member that is in contact with the above-mentioned cylinder head body.

According to this structure, the internal space of the auxiliary chamber is close to the portion of the outer peripheral surface of the auxiliary chamber member that is in contact with the cylinder head body. Therefore, the auxiliary chamber wall portion is close to the portion of the outer peripheral surface of the auxiliary chamber member that contacts the cylinder head body. Therefore, heat easily moves from the sub-chamber wall to the cylinder head body. As a result, the occurrence of pre-ignition can be further suppressed.

The auxiliary chamber combustion four-stroke engine according to one embodiment of the present invention may also have the following configuration. A plane that passes through the internal space of the auxiliary chamber and is orthogonal to the axial direction of the spark plug is in contact with the male thread formed in the auxiliary chamber member and the female thread formed in the cylinder head body.

According to this structure, the contact area between the sub chamber member and the cylinder head body is large. Therefore, heat moves more easily from the auxiliary chamber components to the cylinder head body. As a result, the occurrence of pre-ignition can be further suppressed.

The auxiliary chamber combustion four-stroke engine according to one embodiment of the present invention may also have the following configuration. There is no main combustion chamber fuel injection valve for injecting fuel into the main combustion chamber.

According to this configuration, compared with the case where the main combustion chamber fuel injection valve is provided, the cylinder head can be suppressed from being enlarged.

In the present invention and embodiments, the so-called low load area refers to an area where the engine load is lower when the area with the lowest engine load and the highest engine load is divided into two halves.

In the present invention and embodiments, the air-fuel ratio, which is a mixing ratio of fuel and air, is expressed by a first air-fuel ratio, a second air-fuel ratio, and a third air-fuel ratio. The first air-fuel ratio refers to an air-fuel ratio that can be processed by a three-way catalyst after combustion. The first air-fuel ratio may be a theoretical air-fuel ratio (stoichiometric ratio), or an air-fuel ratio window including the theoretical air-fuel ratio. The first air-fuel ratio may be an air-fuel ratio close to the theoretical air-fuel ratio. The first air-fuel ratio may be a window that includes air-fuel ratios near the theoretical air-fuel ratio and does not include the theoretical air-fuel ratio. The second air-fuel ratio is an air-fuel ratio richer than the first air-fuel ratio. When the first air-fuel ratio is an air-fuel ratio close to the theoretical air-fuel ratio, or is a window that does not include the theoretical air-fuel ratio, the second air-fuel ratio may be richer than the theoretical air-fuel ratio or not. The third air-fuel ratio refers to an air-fuel ratio that is poorer than the first air-fuel ratio. In the present invention and embodiments, the term "rich" means that the mixed gas is rich in fuel. The so-called lean means that the fuel mixture is thinner. In the present invention and embodiments, the air-fuel ratio that can be treated with a three-way catalyst after combustion refers to a mixed gas that can be treated with a three-way catalyst after the exhaust gas generated after the mixed gas is burned. Air fuel ratio. In the present invention and embodiments, the control device may also control the intake passage injection valve so that in at least part of the low load region, the mixed gas mixed in the intake passage and the main combustion chamber becomes the theoretical air-fuel ratio or is rich in air-fuel ratio. Theoretical air fuel ratio air fuel ratio. The auxiliary chamber combustion four-stroke engine of the present invention has a catalyst arranged in the exhaust passage. The auxiliary chamber combustion four-stroke engine of the present invention may also have a three-way catalyst arranged in the exhaust passage. The auxiliary chamber combustion four-stroke engine of the present invention may also have a catalyst other than a three-way catalyst arranged in the exhaust passage. The auxiliary chamber combustion four-stroke engine of the present invention has an oxygen sensor. The oxygen sensor is arranged between the main combustion chamber and the catalyst and detects the oxygen concentration of the exhaust gas flowing in the exhaust passage.

In the present invention and the embodiments, the so-called ignition auxiliary device that assists in the ignition of the mixed gas in the auxiliary chamber or the main combustion chamber refers to, for example, a device that generates microwave discharge, a device that generates dielectric barrier discharge (silent discharge), or a device that auxiliary to the main combustion chamber. Spark plug, etc. for igniting the mixed gas in the chamber. In the present invention and embodiments, the so-called auxiliary chamber combustion four-stroke engine does not have an ignition auxiliary device. This includes not only not being provided with an ignition auxiliary device independent of the auxiliary chamber spark plug, but also including that the auxiliary chamber spark plug does not have the function of an ignition auxiliary device.

In the present invention and embodiments, the term "auxiliary chamber has a smaller volume than the main combustion chamber" means that the volume of the auxiliary chamber is smaller than the minimum volume of the main combustion chamber. Furthermore, the volume of the main combustion chamber changes as the piston moves. The so-called volume of the auxiliary chamber refers to the volume of the internal space of the auxiliary chamber. In the present invention and embodiments, the internal space of the auxiliary chamber does not include the internal space of the plurality of communicating holes. In the present invention and embodiments, the inner surface of the auxiliary chamber refers to the surface forming the internal space of the auxiliary chamber. In the present invention and embodiments, the auxiliary chamber spark plug forms part of the inner surface of the auxiliary chamber. In the present invention and embodiments, the term "no protrusions are formed on the inner surface of the auxiliary chamber except for the spark plug of the auxiliary chamber" means that no protrusions are formed on the inner surface of the auxiliary chamber, or the protrusions formed on the inner surface of the auxiliary chamber are only The protrusion formed by the spark plug of the secondary chamber. In the present invention, the auxiliary chamber wall portion in which a plurality of communication holes are formed refers to a wall portion having a single surface exposed to the internal space of the main combustion chamber. The auxiliary chamber wall may be formed to protrude toward the internal space of the main combustion chamber, or may not be formed to protrude. When the auxiliary chamber wall is formed to protrude toward the internal space of the main combustion chamber, the auxiliary chamber wall has a cylindrical portion.

In the present invention and embodiments, the cooling medium is liquid or gas. The liquid cooling medium may be, for example, water or lubricating oil. The gas cooling medium may also be air, for example. In the present invention and embodiments, the cooling unit that accommodates the cooling medium is at least one chamber (chamber) or at least one passage. The cooling medium may also flow in the cooling part. A passage for the flow of the cooling medium flowing into the cooling part and a passage for the flow of the cooling medium discharged from the cooling part may be connected to the cooling part. The cooling part may also be a plurality of chambers (chambers) or a plurality of passages that are not connected to each other.

In the present invention and embodiments, the heat path is a path along which heat is moved. In the present invention and embodiments, the plurality of thermal paths from the electrode part of the sub-chamber spark plug to the cooling part are not limited to mutually independent thermal paths. That is, heat can also move between multiple thermal paths. The same applies to the definition of a plurality of heat paths from the auxiliary chamber wall to the cooling part in the present invention and embodiments.

In the present invention and embodiments, the electrode portion of the sub-chamber spark plug includes at least one center electrode and at least one ground electrode. The electrode part may also include, for example, a single center electrode and a plurality of ground electrodes or annular ground electrodes. The plurality of ground electrodes may be, for example, two ground electrodes. The plurality of ground electrodes may be, for example, three or more ground electrodes. When the electrode part has a single center electrode and a plurality of ground electrodes, a plurality of discharge gaps will be formed. When the electrode part has a single center electrode and an annular ground electrode, an annular discharge gap will be formed. Spark discharge occurs in the discharge gap. In the present invention and embodiments, the so-called spark plug axial direction of the sub-chamber spark plug refers to the direction parallel to the central axis of the sub-chamber spark plug. The axial direction of the spark plug of the auxiliary chamber spark plug may be parallel to the central axis of the cylinder hole forming the main combustion chamber, or may not be parallel.

In the present invention and embodiments, "a plurality of spark discharges are generated dispersedly in the circumferential direction" means that the locations where spark discharges are generated are dispersed in the circumferential direction. The phrase "a plurality of spark discharges are generated dispersedly in the circumferential direction" does not mean that a plurality of spark discharges are generated simultaneously at positions dispersed in the circumferential direction. Instead, multiple spark discharges can be generated simultaneously at positions dispersed along the circumferential direction. In this case, at least one of the plurality of spark discharges generated simultaneously becomes the starting point of ignition. The circumferential direction in the description "a plurality of spark discharges are dispersedly generated in the circumferential direction" is, for example, the circumferential direction centered on a straight line parallel to the axial direction of the spark plug of the sub-chamber spark plug. An example of a case where a plurality of spark discharges are not dispersedly generated in the circumferential direction is a case where the electrode portion has a single center electrode and a single ground electrode. Another example of a case where a plurality of spark discharges are not dispersedly formed in the circumferential direction is a case where the electrode portion has a single center electrode, a first ground electrode for main use, and a second ground electrode for auxiliary use. Another example of a situation where a plurality of spark discharges are not generated dispersedly in the circumferential direction is when the positions where the mixed gas is easily ignited are not substantially uniform in the circumferential direction due to concentration deviations of the mixed gas inside the sub-chamber. Specific examples of the case where a plurality of spark discharges are not dispersedly generated in the circumferential direction are not limited to these.

In the present invention and embodiments, "a plurality of communication holes are formed dispersedly along the circumferential direction" means that a plurality of communication holes are arranged and formed along the circumferential direction without extreme deviation. When the plurality of communication holes are formed dispersedly in the circumferential direction, the plurality of communication holes are formed in an array along the circumferential direction. The phrase "the plurality of communication holes are formed dispersedly in the circumferential direction" is not limited to the plurality of communication holes being formed at equal intervals in the circumferential direction. The circumferential direction in the description "a plurality of communication holes are formed dispersedly in the circumferential direction" is, for example, the circumferential direction centered on a straight line parallel to the axial direction of the spark plug of the sub-chamber spark plug.

In the present invention and embodiments, "a plurality of heat paths from the electrode part of the sub-chamber spark plug to the cooling part are formed dispersedly in the circumferential direction" means the heat that moves from the electrode part of the sub-chamber spark plug to the cooling part. dispersed along the circumferential direction. That is, it means that the ease of heat transfer from the electrode part of the sub-chamber spark plug to the cooling part is substantially equal in the circumferential direction. "A plurality of thermal paths from the electrode part of the sub-chamber spark plug to the cooling part are formed dispersedly in the circumferential direction." The circumferential direction in this description is, for example, centered on a straight line parallel to the axial direction of the sub-chamber spark plug. circumferential direction. In the present invention and embodiments, "a plurality of heat paths from the auxiliary chamber wall to the cooling part are formed dispersedly in the circumferential direction" means that the heat moving from the auxiliary chamber wall to the cooling part is dispersed in the circumferential direction. That is, it means that the ease of heat transfer from the sub-chamber wall to the cooling part is substantially equal in the circumferential direction. The circumferential direction in the description "a plurality of heat paths from the sub-chamber wall to the cooling part is formed dispersedly in the circumferential direction" is, for example, the circumferential direction centered on a straight line parallel to the axial direction of the spark plug of the sub-chamber. The circumferential direction may also be the same as the circumferential direction in which a plurality of communication holes are arranged. The electrode portion is formed so that a plurality of spark discharges generated in the electrode portion are dispersedly generated in the circumferential direction. That is, the heat generated by the electrode portion is dispersedly generated in the circumferential direction. Therefore, in order to form a plurality of heat paths from the electrode part of the sub-chamber spark plug to the cooling part dispersedly in the circumferential direction, it is important to have the cooling part and the part between the sub-chamber spark plug and the cooling part in the cylinder head. In addition, the plurality of communication holes formed in the sub-chamber wall are formed dispersedly in the circumferential direction. That is, the heat generated in the sub-chamber wall is dispersed in the circumferential direction. Therefore, in order to form a plurality of thermal paths from the auxiliary chamber wall to the cooling portion dispersedly in the circumferential direction, the cooling portion and the portion between the auxiliary chamber wall and the cooling portion in the cylinder head are important. For example, when the cooling portion is formed in an annular shape, a plurality of thermal paths from the electrode portion of the sub-chamber spark plug to the cooling portion and a plurality of thermal paths from the sub-chamber wall portion to the cooling portion are easily dispersed in the circumferential direction. ground formation. For example, when the structure (shape and material) of the portion between the sub-chamber spark plug and the cooling section in the cylinder head is substantially uniform in the circumferential direction, it is easy to make the plurality of parts from the electrode section of the sub-chamber spark plug to the cooling section Thermal paths are formed dispersedly along the circumferential direction. Also, for example, when the structure (shape and material) of the portion between the sub-chamber wall and the cooling portion in the cylinder head is substantially uniform in the circumferential direction, it is easy to make the spark plug from the electrode portion of the sub-chamber to the cooling portion A plurality of thermal paths are formed dispersedly along the circumferential direction. An example of a case where a plurality of heat paths from the electrode part of the sub-chamber spark plug to the cooling part are not formed dispersedly in the circumferential direction is when the cooling part is formed only in an area about half of the circumference. This example may be a case where a plurality of heat paths from the sub-chamber wall to the cooling part are not dispersedly formed in the circumferential direction. Another example of a situation where multiple heat paths from the auxiliary chamber wall to the cooling part are not formed dispersedly in the circumferential direction is the material between the auxiliary chamber wall and the cooling part in the region of one half of the circumference and the remaining half of the circumference. Different situations. Furthermore, there are specific examples of the situation in which the plurality of heat paths from the electrode part of the sub-chamber spark plug to the cooling part are not dispersed in the circumferential direction and the plurality of heat paths from the sub-chamber wall part to the cooling part are not dispersed in the circumferential direction. Specific examples of geological formation are not limited to these.

In the present invention and embodiments, when the auxiliary chamber wall is composed of a plurality of parts with different materials, the base material of the auxiliary chamber wall refers to the material that occupies the largest volume among the plurality of parts. Furthermore, in the present invention and embodiments, the auxiliary chamber wall portion may not be composed of a plurality of parts made of different materials. In the present invention and embodiments, when the cylinder head is composed of a plurality of parts with different materials, the so-called base material of the cylinder head refers to the material that occupies the largest volume among the plurality of parts. When the base material of the auxiliary chamber wall is different from the base material of the cylinder head, the part occupying the largest volume among the plurality of parts constituting the cylinder head made of different materials does not include the auxiliary chamber wall. Furthermore, in the present invention and embodiments, the cylinder head includes a sub-chamber wall. In the present invention and embodiments, a portion of the cylinder head body that is exposed to the internal space of the main combustion chamber does not include the auxiliary chamber wall. The base material of the cylinder head body is the same as that of the cylinder head. The cylinder head body may or may not be composed of multiple parts of different materials.

In the present invention and embodiments, the thermal conductivity of the base material of the auxiliary chamber wall is the same as or higher than that of chromium-based stainless steel, which means that the main combustion chamber and the auxiliary chamber when the auxiliary chamber combustion four-stroke engine is running Under the temperature conditions, the thermal conductivity of the base material of the auxiliary chamber wall is equal to or higher than the thermal conductivity of chromium-based stainless steel. The temperature of the main combustion chamber and the auxiliary chamber when the auxiliary chamber combustion four-stroke engine is operating is, for example, about 850 to 1000°C when it is high, and about 500 to 600°C when it is low.

In the present invention and embodiments, the so-called axial length of the spark plug in the internal space of the auxiliary chamber refers to the axial length of the spark plug between one end and the other end of the internal space of the auxiliary chamber in the axial direction of the spark plug. In other words, it refers to the plane that passes through one end of the axial direction of the spark plug in the internal space of the auxiliary chamber and is orthogonal to the axial direction of the spark plug, and the other end of the axial direction of the spark plug that passes through the internal space of the auxiliary chamber and is orthogonal to the axial direction of the spark plug. the distance between the planes. In the present invention and embodiments, the definition of the length of the internal space of the auxiliary chamber in one direction orthogonal to the axial direction of the spark plug is also the same as above. In the present invention and embodiments, the maximum length of the internal space of the auxiliary chamber in the direction orthogonal to the axial direction of the spark plug refers to the lengths of the internal spaces of the auxiliary chamber in multiple directions orthogonal to the axial direction of the spark plug. the maximum length in .

In the present invention and embodiments, the term "the plane that passes through the cooling part and is orthogonal to the axial direction of the spark plug in the auxiliary chamber passes through the auxiliary chamber spark plug" does not mean to limit the plane that passes through the cooling part and is orthogonal to the axial direction of the auxiliary chamber spark plug. All planes orthogonal to the axial direction of the spark plug pass through the auxiliary chamber spark plug, but it means that any plane that passes through the cooling part and is orthogonal to the axial direction of the auxiliary chamber spark plug passes through the auxiliary chamber spark plug. In the present invention and embodiments, "the plane that passes through the cooling part and is orthogonal to the axial direction of the spark plug of the auxiliary chamber spark plug passes through the auxiliary chamber member", "passes through the cooling part and is orthogonal to the axial direction of the spark plug of the auxiliary chamber spark plug" The intersection plane passes through the part where the male thread formed on the spark plug of the auxiliary chamber engages with the female thread formed on the auxiliary chamber member", and "passes through the internal space of the auxiliary chamber and is axially orthogonal to the spark plug of the auxiliary chamber. The description of "the part where the plane passes through the outer circumferential surface of the auxiliary chamber member and is in contact with the cylinder head body" is also explained in the same way as above.

In the present invention and embodiments, the so-called "auxiliary chamber component is independent from the cylinder head body that is partially exposed to the internal space of the main combustion chamber" means that the auxiliary chamber component is separated from the cylinder head body, or that the auxiliary chamber component is detachable. way to contact the cylinder head body. In the present invention and embodiments, the cylinder head body may be composed of one inseparable member, or may be composed of a plurality of separable members each of which is partially exposed to the internal space of the main combustion chamber. When the cylinder head body is composed of a plurality of separable components, the cylinder head body does not include components without any part being exposed to the internal space of the main combustion chamber. In the present invention and embodiments, the so-called "auxiliary chamber component and the auxiliary chamber spark plug are independent" means that the auxiliary chamber component is separated from the auxiliary chamber spark plug, or that the auxiliary chamber component is in detachable contact with the auxiliary chamber spark plug. . The auxiliary chamber member does not include a part of the electrode portion of the auxiliary chamber spark plug (for example, a ground electrode).

In the present invention and embodiments, when the number of a certain constituent element is not clearly specified (that is, when it is expressed in singular form when translated into English), the number of the constituent element may be one or plural. Piece. In the present invention and the embodiments, the components whose number is not clearly specified include, for example, the main combustion chamber, the intake passage, the exhaust passage, the throttle valve, the intake passage injection valve, the auxiliary chamber, the auxiliary chamber spark plug, etc. . The auxiliary chamber combustion four-stroke engine of the present invention and embodiments may have a single main combustion chamber or a plurality of main combustion chambers. That is, the auxiliary chamber combustion four-stroke engine of the present invention and embodiments may be a single-cylinder engine unit or a multi-cylinder engine unit. The number of auxiliary chambers and auxiliary chamber spark plugs is the same as the number of main combustion chambers respectively. The number of injection valves in the intake passage may be the same as the number of main combustion chambers, or may be greater. The number of throttle valves may be the same as the number of main combustion chambers, or may be less. The air intake passage may be branched into two or more shapes. The number of intake passages connected to one main combustion chamber is one. It is also possible to connect one branch-shaped intake passage to a plurality of main combustion chambers. The exhaust passage may be branched into two or more shapes. The number of exhaust passages connected to one main combustion chamber is one. It is also possible to connect one branch-shaped exhaust passage to a plurality of main combustion chambers.

The auxiliary chamber combustion four-stroke engine of the present invention and embodiments can be mounted on a straddle-type vehicle that is lighter than a car and requires a lightweight and compact engine. The so-called straddle-type vehicles refer to all vehicles in which the driver rides as if he is sitting astride the back of the vehicle. Straddle-type vehicles include motorcycles, scooters, motor tricycles, ATVs (All Terrain Vehicles), snowmobiles, and watercraft (Personal Water Craft). )wait. In addition, the subchamber combustion four-stroke engine of the present invention and embodiments can be mounted on a work vehicle that requires weight reduction and downsizing of the engine. Furthermore, the auxiliary chamber combustion four-stroke engine of the present invention and embodiments can of course be mounted on an automobile. Products equipped with the subchamber combustion four-stroke engine of the present invention and embodiments are not limited to specific products. When the sub-chamber combustion four-stroke engine according to one embodiment of the present invention is mounted on a product, it may be mounted so that the central axis of the cylinder bore becomes 0 degrees or more and 45 degrees or less with respect to the vertical, or it may be 45 degrees. It can be installed in the above 90 degrees or below.

In the present invention and embodiments, "including, having, comprising, and derivatives thereof" is intended to include additional items in addition to the exemplified items and their equivalents.

Unless otherwise defined, all terms (including technical terms and scientific terms) used in the present invention and embodiments have the same meaning as commonly understood by those skilled in the art to which the present invention belongs. Terms such as those defined in commonly used dictionaries should be interpreted to have a meaning consistent with the meaning in the context of the relevant technology and the present invention, and should not be interpreted in an idealized or overly formalized meaning.

In the present invention and embodiments, the term "maybe" is non-exclusive. "Also~" means "Also~, but not limited to this." In the present invention and embodiments, the configuration described as “maybe” exhibits at least the above-described effects obtained by the configuration of claim 1.

Before describing the embodiments of the present invention in detail, it should be understood that the present invention is not limited to the details of the construction and arrangement of the constituent elements described in the following description or illustrated in the drawings. The present invention may be implemented in other embodiments than those described below. The present invention can also be an embodiment obtained by adding various modifications to the following embodiments. [Effects of the invention]

The sub-chamber combustion four-stroke engine according to the present invention can suppress the enlargement of the cylinder head and suppress the occurrence of pre-ignition.

Hereinafter, a subchamber combustion four-stroke engine as one embodiment of the present invention will be described with reference to the drawings. In addition, the embodiment described below is an illustration. The present invention is not to be construed in any way as being limited to the embodiments described below.

<First Embodiment> The auxiliary chamber combustion four-stroke engine 1 according to the first embodiment of the present invention will be described using FIGS. 1(a) to 1(f). Fig. 1(b) shows an example of a part of the cross section along line A-A in Fig. 1(a). Figure 1(c) and Figure 1(d) show two examples of a part of the cross section along line B-B in Figure 1(a). Figure 1(e) and Figure 1(f) show two examples of a part of the cross section along line C-C in Figure 1(a). The auxiliary chamber combustion four-stroke engine 1 of the first embodiment has at least one main combustion chamber 2 . The intake passage 5 and the exhaust passage 6 are connected to the main combustion chamber 2 . The main combustion chamber 2 is formed by the cylinder head 10 , the cylinder bore 11 and the piston 12 . The intake passage 5 includes a passage formed inside the cylinder head 10 and a passage connected to the passage. The exhaust passage 6 includes a passage formed inside the cylinder head 10 and a passage connected to the passage. The auxiliary chamber combustion four-stroke engine 1 has at least one throttle valve 7 . The throttle valve 7 adjusts the amount of air sucked into the main combustion chamber 2 through the intake passage 5 . The auxiliary chamber combustion four-stroke engine 1 has at least one intake passage injection valve 8 . The intake passage injection valve 8 injects gasoline fuel, alcohol fuel, or liquid fuel that is a gasoline/alcohol mixed fuel into the inside of the intake passage 5 . The auxiliary chamber combustion four-stroke engine 1 has at least one auxiliary chamber 20 . The internal space of the auxiliary chamber 20 is connected with the internal space of the main combustion chamber 2 via a plurality of communication holes 21 . The volume of the auxiliary chamber 20 is smaller than the volume of the main combustion chamber 2 . A part of the spark plug 23 of the auxiliary chamber is exposed to the internal space of the auxiliary chamber 20 . The auxiliary chamber 20 is formed in the cylinder head 10 . A plurality of communication holes 21 are formed in the sub-chamber wall portion 22 of the cylinder head 10 . The auxiliary chamber wall 22 has a single surface exposed to the internal space of the main combustion chamber 2 . The relationship between the position of the central axis C11 of the cylinder bore 11 and the position of the central axis C23 of the auxiliary chamber spark plug 23 is not limited to the positional relationship shown in Figure 1(a) and Figure 1(b). Let the direction parallel to the central axis C23 of the sub-chamber spark plug 23 be the spark plug axial direction DP. In Figure 1 (a) and Figure 1 (b), the spark plug axial direction DP is parallel to the central axis C11 of the cylinder bore 11, but the spark plug axial direction DP does not need to be parallel to the central axis C11 of the cylinder bore 11. Furthermore, the shape of the internal space of the auxiliary chamber 20 is not limited to the shape shown in FIG. 1(a) and FIG. 1(b). The auxiliary chamber combustion four-stroke engine 1 has a control device 70 that controls at least one intake passage injection valve 8 and at least one auxiliary chamber spark plug 23 . The control device 70 controls the intake passage injection valve 8 so that the mixed gas mixed in the intake passage 5 and the main combustion chamber 2 becomes the combustion gas in at least a part of the low load area where the opening of the throttle valve 7 is small. The first air-fuel ratio that can be processed by the three-way catalyst or the second air-fuel ratio that is richer than the first air-fuel ratio can be used. For example, the control device 70 may also control the intake passage injection valve 8 so that in at least part of the low load region, the mixed gas mixed in the intake passage 5 and the main combustion chamber 2 becomes a three-way trigger after combustion. The first air-fuel ratio for media processing. The auxiliary chamber combustion four-stroke engine 1 may or may not have a three-way catalyst. The auxiliary chamber combustion four-stroke engine 1 does not have any of the auxiliary chamber fuel injection valves for injecting fuel into the auxiliary chamber 20 and the ignition assist device for assisting the ignition of the mixed gas in the auxiliary chamber 20 or the main combustion chamber 2 .

As shown in FIGS. 1(a) and 1(b) , the cylinder head 10 has a cooling part 16 that accommodates a cooling medium that receives heat from the electrode part 24 of the sub-chamber spark plug 23 and the sub-chamber wall part 22 (not shown). In FIG. 1( b ), the cooling part 16 is annular, but the cooling part 16 may not be annular. The electrode portion 24 of the sub-chamber spark plug 23 is formed so that a plurality of spark discharges 33 are dispersedly generated in the electrode portion 24 in the circumferential direction. A plurality of communication holes 21 are formed dispersedly in the circumferential direction. The cylinder head 10 is formed such that a plurality of thermal paths 14 from the electrode portion 24 of the sub-chamber spark plug 23 to the cooling portion 16 and a plurality of thermal paths 15 from the sub-chamber wall portion 22 to the cooling portion 16 are formed dispersedly in the circumferential direction. . For example, a plurality of spark discharges 33 , a plurality of communication holes 21 , a plurality of heat paths 14 and a plurality of heat paths 15 may also be formed dispersedly along the circumferential direction centered on the central axis C23 of the sub-chamber spark plug 23 . The heat path 14 shown in FIG. 1(a) is only an example of the heat path 14 from the electrode part 24 of the sub-chamber spark plug 23 to the cooling part 16. The heat path 15 shown in FIG. 1(a) is only an example of the heat path 15 from the auxiliary chamber wall part 22 to the cooling part 16. The two spark discharges 33 shown in FIG. 1(c) are only one example of the plurality of spark discharges 33 generated dispersedly in the circumferential direction by the electrode portion 24 of the sub-chamber spark plug 23. The plurality of spark discharges 33 shown in FIG. 1(d) is only an example of the plurality of spark discharges 33 generated dispersedly in the circumferential direction by the electrode portion 24 of the sub-chamber spark plug 23. The structure of the electrode part 24 is not limited to the structure shown in FIG. 1(c) and FIG. 1(d). For example, as shown in FIG. 1(c) , the electrode part 24 may have a single center electrode 30 and a plurality of ground electrodes 31. For example, as shown in FIG. 1(d) , the electrode part 24 may also have a single center electrode 30 and an annular ground electrode 31. The plurality of ground electrodes 31 are configured such that spaces are formed between the ground electrodes 31 . The plurality of ground electrodes 31 are separated from the center electrode 30 in a direction orthogonal to the spark plug axial direction DP. The plurality of ground electrodes 31 and the center electrode 30 are not arranged along the spark plug axial direction DP. The inner peripheral end of the annular ground electrode 31 is separated from the center electrode 30 in a direction orthogonal to the spark plug axial direction DP. A plurality of discharge gaps or annular discharge gaps in a direction orthogonal to the spark plug axial direction DP are formed between a single center electrode 30 and a plurality of ground electrodes 31 or annular ground electrodes 31 . The number of the plurality of ground electrodes 31 may be two, for example. The number, position, shape and size of the plurality of communication holes 21 are not limited to those shown in Figure 1(e) and Figure 1(f). The number of the plurality of communication holes 21 may be, for example, three or more.

According to the structure of the first embodiment, since heat easily moves from the electrode portion 24 and the sub-chamber wall portion 22 of the sub-chamber spark plug 23 to the cooling portion 16, the cooling portion 16 can be suppressed from being enlarged and the occurrence of pre-ignition can be suppressed. Furthermore, since the ignition assist device is not provided, the increase in the size of the cylinder head 10 can be further suppressed. Thereby, it is possible to suppress the increase in the size of the cylinder head 10 and to suppress the occurrence of pre-ignition.

Furthermore, the auxiliary chamber combustion four-stroke engine 1 in FIG. 1(a) is formed such that any plane that passes through the cooling part 16 and is orthogonal to the spark plug axial direction DP passes through the auxiliary chamber spark plug 23. This plane is, for example, a plane that overlaps line A-A in Fig. 1(a). In FIG. 1( a ), the auxiliary chamber combustion four-stroke engine 1 is formed so that no plane passing through the cooling part 16 and orthogonal to the spark plug axial direction DP passes through the internal space of the auxiliary chamber 20 . In the first embodiment, the auxiliary chamber combustion four-stroke engine 1 may also be formed such that any plane orthogonal to the spark plug axial direction DP passes through the cooling part 16 and passes through the internal space of the auxiliary chamber 20 .

The subchamber combustion four-stroke engine 1 of the first embodiment does not need to have a main combustion chamber fuel injection valve for injecting fuel into the main combustion chamber 2 . The subchamber combustion four-stroke engine 1 of the first embodiment does not need to have either a supercharger or a turbocharger. That is, the auxiliary chamber combustion four-stroke engine 1 may be a naturally aspirated engine. The auxiliary chamber combustion four-stroke engine 1 of the first embodiment may not have an external exhaust gas recirculation device including an external exhaust gas recirculation passage that is detoured in the main combustion chamber 2 and connected to the exhaust passage 6 and air intake passage 5.

<Second Embodiment> The auxiliary chamber combustion four-stroke engine 1 according to the second embodiment of the present invention will be described. The second embodiment has the configuration of the first embodiment. In the second embodiment, the melting point of the base material of the sub-chamber wall portion 22 is higher than the melting point of the base material of the cylinder head 10 . The value obtained by multiplying the specific heat and the specific gravity of the base material of the auxiliary chamber wall portion 22 is higher than the value obtained by multiplying the specific heat and the specific gravity of the base material of the cylinder head 10 . The thermal conductivity of the base material of the auxiliary chamber wall 22 is equal to or higher than the thermal conductivity of chromium-based stainless steel. The base material of the cylinder head 10 is, for example, aluminum or aluminum alloy. When the base material of the cylinder head 10 is aluminum or an aluminum alloy, for example, materials shown in Examples 1 to 4 in Table 1 below may be used as the base material of the auxiliary chamber wall portion 22 . The base material of the auxiliary chamber wall 22 may also be the chromium-zirconium-copper alloy as in Embodiment 1. The base material of the auxiliary chamber wall 22 may also be a chromium copper alloy. Comparative Examples 1 to 3 shown in Table 1 are examples of materials that are not used as the base material of the auxiliary chamber wall portion 22 when the base material of the cylinder head 10 is aluminum or an aluminum alloy.

[Table 1] Material Thermal conductivity w/m·k Specific gravity g/cm ³ Specific heat J/g·k Specific gravity × specific heat J/cm ³ ·k Melting point℃ refer to Aluminum 239.0 2.690 0.917 2.467 660.3 refer to Chromium series stainless steel 26.0 7.700 0.460 3.542 1480 Example 1 Chromium Zirconium Copper (C18150) 320.0 8.900 0.376 3.346 1050 Example 2 Copper 393.0 8.930 0.386 3.447 1085 Example 3 iron 80.4 7.870 0.440 3.463 1538 Example 4 Alumina ceramics (alumina 99.7%) 29.0 3.900 0.800 3.120 2072 Comparative example 1 titanium 22.0 4.510 0.527 2.377 1668 Comparative example 2 Nickel chromium alloy 718 (registered trademark) 11.0 8.190 0.440 3.604 1280 Comparative example 3 SUS304 series stainless steel 16.3 7.930 0.502 3.981 1400～1500

The auxiliary chamber wall portion 22 may include only the base material. The auxiliary chamber wall 22 may also include the base material and materials other than the base material. For example, the auxiliary chamber wall portion 22 may also have a coating layer of a material different from that of the base material on at least a portion of the outer surface of the auxiliary chamber wall portion 22 . The thermal conductivity of the coating layer is preferably higher than the thermal conductivity of the auxiliary chamber wall 22 .

<3rd Embodiment> The auxiliary chamber combustion four-stroke engine 1 according to the third embodiment of the present invention will be described using FIG. 2(a) . The subchamber combustion four-stroke engine 1 of the third embodiment has the following configuration in addition to the configuration of the first embodiment or the second embodiment. Except for the spark plug 23 of the auxiliary chamber, no protrusions are formed on the inner surface of the auxiliary chamber 20 . Among the length L1 of the internal space of the auxiliary chamber 20 in the spark plug axial direction DP and the maximum length L2 of the internal space of the auxiliary chamber 20 in the direction orthogonal to the spark plug axial direction DP, the larger length is less than 2 of the smaller length. times. In Figure 2(a), the length L2 is greater than the length L1, but the length L1 can also be greater than the length L2.

<4th Embodiment> The auxiliary chamber combustion four-stroke engine 1 according to the fourth embodiment of the present invention will be described using FIG. 2(b). The fourth embodiment has the configuration of at least one of the first to third embodiments. In the fourth embodiment, the sub-chamber wall portion 22 is formed to protrude toward the internal space of the main combustion chamber 2 . Furthermore, in the fourth embodiment, the auxiliary chamber 20 is formed such that the protrusion amount of the auxiliary chamber wall 22 is smaller than the volume of the auxiliary chamber 20 . Specifically, the internal space of the auxiliary chamber 20 is divided into two on any plane S1 that passes through the internal space of the auxiliary chamber 20 without passing through the outer surface of the auxiliary chamber wall 22 and is orthogonal to the spark plug axial direction DP. In the case of a space, the auxiliary chamber 20 is formed such that the volume of the space closer to the main combustion chamber 2 among the two spaces is smaller than the volume of the space farther from the main combustion chamber 2 among the two spaces. The plane S1 shown in FIG. 2(b) is only an example of the plane S1 that does not pass through the outer surface of the auxiliary chamber wall 22 but passes through the internal space of the auxiliary chamber 20 and is orthogonal to the spark plug axial direction DP. Furthermore, the outer surface of the sub-chamber wall 22 refers to the surface exposed to the main combustion chamber 2 . When the internal space of the auxiliary chamber 20 is divided into two spaces by any plane S1 that does not pass through the outer surface of the auxiliary chamber wall 22 but passes through the internal space of the auxiliary chamber 20 and is orthogonal to the spark plug axial direction DP. The so-called auxiliary chamber 20 formed in such a manner that the volume of the space close to the main combustion chamber 2 among the two spaces is smaller than the volume of the space farther from the main combustion chamber 2 is not the auxiliary chamber 20 as described below. This auxiliary chamber 20 has the following relationship with respect to all planes that do not pass through the outer surface of the auxiliary chamber wall 22 but pass through the internal space of the auxiliary chamber 20 and are orthogonal to the spark plug axial direction DP. This relationship is that when the internal space of the auxiliary chamber 20 is divided into two spaces using a plane, the volume of the space closer to the main combustion chamber 2 among the two spaces is equal to or greater than the volume of the space further away from the main combustion chamber 2 among the two spaces. relationship between the volume of space.

<5th Embodiment> Using Figures 3(a) to 3(c), Figures 4(a) to 4(e), Figure 5(a) and Figure 5(b), the auxiliary chamber combustion four-stroke of the fifth embodiment of the present invention is Engine 1 is explained. 3(a) to 3(c) show three examples of the fifth embodiment. 4(a) to 4(e) show five examples of the fifth embodiment. FIG. 5(a) and FIG. 5(b) show two examples of the fifth embodiment. The fifth embodiment has the configuration of at least one of the first to fourth embodiments. In the fifth embodiment, the inner surface of the sub chamber 20 is formed by the sub chamber member 25 including the sub chamber wall portion 22 and the sub chamber spark plug 23 . That is, the internal space of the sub chamber 20 is a space surrounded by the sub chamber member 25 and the sub chamber spark plug 23 . The outer peripheral surface of the auxiliary chamber spark plug 23 is in contact with the inner peripheral surface of the auxiliary chamber member 25 . The auxiliary chamber member 25 is independent from the cylinder head body 13, which is partially exposed to the internal space of the main combustion chamber 2, and is independent from the auxiliary chamber spark plug 23. The cylinder head body 13 may include one inseparable component, or may include a plurality of separable components each of which is partially exposed to the internal space of the main combustion chamber 2 . When the cylinder head body 13 includes a plurality of separable components, the cylinder head body 13 does not include any component without any part being exposed to the internal space of the main combustion chamber 2 .

For example, as shown in FIGS. 3(a) and 3(b) , the outer peripheral surface of the auxiliary chamber member 25 may also be in contact with the cylinder head body 13 . For example, as shown in FIG. 3( b ), the male thread 41 formed in the sub-chamber member 25 may be meshed with the female thread 40 formed in the cylinder head body 13 to make contact. When the outer peripheral surface of the auxiliary chamber member 25 is in contact with the cylinder head body 13, for example, as shown in Figure 3 (a) and Figure 3 (b), it passes through the internal space of the auxiliary chamber 20 and is orthogonal to the spark plug axial direction DP. Any plane S2 may also pass through the portion of the outer peripheral surface of the auxiliary chamber member 25 that is in contact with the cylinder head body 13 . For example, as shown in FIG. 3(b) , the plane S2 passing through the contact part may also be the part where the male thread 41 formed in the auxiliary chamber member 25 meshes with the female thread 40 formed in the cylinder head body 13 to make contact. For example, as shown in FIG. 3(b) , the plane S2 passing through the contact portion may also pass through the auxiliary chamber member 25 and the non-threaded portion (the male thread 41 and the female thread 40 ) of the cylinder head body 13 . The outer peripheral surface of the auxiliary chamber member 25 shown in FIG. 3(c) may also be in contact with the cylinder head body 13 at a location not shown in the figure. For example, any plane (not shown) orthogonal to the spark plug axial direction DP that passes through the auxiliary chamber spark plug 23 and does not pass through the internal space of the auxiliary chamber 20 may also pass through the outer peripheral surface of the auxiliary chamber member 25 and the cylinder head body. 13, so that the outer peripheral surface of the auxiliary chamber member 25 shown in Fig. 3(c) is in contact with the cylinder head body 13. In this case, the contact portion between the outer peripheral surface of the auxiliary chamber member 25 and the cylinder head body 13 may be a threaded portion (male thread 41 and female thread 40 ), or may not be a threaded portion.

The outer peripheral surface of the auxiliary chamber member 25 does not need to be in contact with the cylinder head body 13 . For example, the outer peripheral surface of the auxiliary chamber member 25 shown in Figure 3(c) does not need to be in contact with the cylinder head body. For example, the auxiliary chamber member 25 may be connected to the cylinder head body through a member other than the cylinder head body 13 (such as a cylinder head cover).

For example, as shown in FIGS. 4(a) to 4(d) , the auxiliary chamber member 25 and the cooling unit 25 may also be formed by passing the auxiliary chamber member 25 through any plane S3 orthogonal to the spark plug axial direction DP through the cooling part 16 . Department 16. When the plane S3 passes through the auxiliary chamber member 25, for example, as shown in FIGS. 4(a) to 4(c), part of the inner surface of the cooling part 16 may also be at least part of the outer peripheral surface of the auxiliary chamber member 25. When the plane S3 passes through the auxiliary chamber member 25, for example, as shown in FIG. 4(d), the inner surface of the cooling part 16 may not include part of the outer peripheral surface of the auxiliary chamber member 25. Moreover, for example, as shown in FIG. 4(e) , the auxiliary chamber member 25 and the cooling portion 16 may be formed such that the auxiliary chamber member 25 and the cooling unit 16 pass through the cooling portion 16 and any plane S3 orthogonal to the spark plug axial direction DP does not pass through the auxiliary chamber member 25 . . Furthermore, the relationship between the auxiliary chamber member 25 and the cylinder head body 13 shown in FIGS. 4(a) to 4(d) is not limited to the same relationship as in FIG. 3(a), and may be any of the above relationships.

When a part of the inner surface of the cooling part 16 is at least a part of the outer peripheral surface of the auxiliary chamber member 25, for example, as shown in FIG. At least one heat sink 26. The heat dissipation part 26 may be annular or non-annular. For example, the heat dissipation part 26 may be in the shape of an arc larger than a semicircle, or may not be in the shape of an arc. The annular heat dissipation part 26 may also be formed by dividing the internal space of the cooling part 16 into a plurality of spaces. The auxiliary chamber member 25 may also have a plurality of heat dissipation parts 26 arranged in the spark plug axial direction DP.

When any plane S3 passing through the cooling part 16 passes through the auxiliary chamber member 25 (for example, FIGS. 4(a) to 4(d) ), any plane S3 passing through the cooling part 16 may also pass through the auxiliary chamber member 25 The part where the inner peripheral surface contacts the outer peripheral surface of the auxiliary chamber spark plug 23. When any plane S3 passing through the cooling part 16 passes through the auxiliary chamber member 25, for example, as shown in FIGS. 5(a) and 5(b), any plane S3 passing through the cooling part 16 may also pass through the auxiliary chamber member 25. The female thread 42 of the chamber member 25 engages and contacts the male thread 43 formed on the sub-chamber spark plug 23 . Furthermore, the cooling part 16 of FIG. 5(a) is the same as the cooling part 16 of FIG. 4(a), but may also be the same as the cooling part 16 of FIG. 4(b). The cooling part 16 in FIG. 5(b) is the same as the cooling part 16 in FIG. 4(d), but may also be the same as the cooling part 16 in FIG. 4(c). Furthermore, the relationship between the auxiliary chamber member 25 and the cylinder head body 13 shown in FIGS. 5(a) and 5(b) is not limited to the same relationship as in FIG. 3(a) , and may be any of the above relationships. When any plane S3 passing through the cooling part 16 passes through the auxiliary chamber member 25, any plane S3 passing through the cooling part 16 may not contact the inner peripheral surface of the auxiliary chamber member 25 and the outer peripheral surface of the auxiliary chamber spark plug 23. parts.

The present invention is not limited to the above-described embodiment, and various modifications can be made within the scope described in the patent application. For example, the auxiliary chamber combustion four-stroke engine of the present invention may also have a supercharger or a turbocharger. The auxiliary chamber combustion four-stroke engine may also have a main combustion chamber fuel injection valve that injects fuel into the main combustion chamber.

1: Secondary chamber combustion four-stroke engine 2: Main combustion chamber 5:Inlet passage 6:Exhaust passage 7: Throttle valve 8: Intake passage injection valve 10:Cylinder head 11:Cylinder hole 12:Piston 13:Cylinder head body 14: Thermal path from the electrode part of the auxiliary chamber spark plug to the cooling part 15: Multiple heat paths from the auxiliary chamber wall to the cooling part 16: Cooling department 20:Deputy Room 21:Connecting hole 22:Accessory chamber wall 23: Deputy chamber spark plug 24:Electrode part 25: Auxiliary room components 26:Heat dissipation part 30: Center electrode 31:Ground electrode 33:Spark discharge 40: Female thread of cylinder head body 41: Male thread of auxiliary chamber component 42: Female thread of auxiliary chamber component 43: Male thread of spark plug in auxiliary chamber 70:Control device C11: Central axis of cylinder bore C23: Central axis of the spark plug in the auxiliary chamber DP: Spark plug axial direction L1: The axial length of the spark plug in the internal space of the auxiliary chamber L2: The maximum length of the internal space of the auxiliary chamber in the direction orthogonal to the axial direction of the spark plug S1: Plane S2: Plane S3: Plane

1(a) to 1(f) of FIG. 1 are schematic diagrams of a sub-chamber combustion four-stroke engine according to the first embodiment of the present invention. Figure 2(a) is a schematic diagram of a sub-chamber combustion four-stroke engine according to the third embodiment of the present invention, and Figure 2(b) is a schematic diagram of a sub-chamber combustion four-stroke engine according to the fourth embodiment of the present invention. . 3(a) to 3(c) are schematic diagrams of three examples of the auxiliary chamber combustion four-stroke engine according to the fifth embodiment of the present invention. 4(a) to 4(e) are schematic diagrams of five examples of the auxiliary chamber combustion four-stroke engine according to the fifth embodiment of the present invention. 5(a) and 5(b) are schematic diagrams of two examples of the auxiliary chamber combustion four-stroke engine according to the fifth embodiment of the present invention.

1: Secondary chamber combustion four-stroke engine

2: Main combustion chamber

5:Inlet passage

6:Exhaust passage

7: Throttle valve

8: Intake passage injection valve

10:Cylinder head

11:Cylinder hole

12:Piston

14: Thermal path from the electrode part of the auxiliary chamber spark plug to the cooling part

15: Multiple heat paths from the auxiliary chamber wall to the cooling part

16: Cooling department

20:Deputy room

21:Connecting hole

22:Accessory chamber wall

23: Deputy chamber spark plug

24:Electrode part

30: Center electrode

31:Ground electrode

33:Spark discharge

70:Control device

C11: Central axis of cylinder bore

C23: Central axis of the spark plug in the auxiliary chamber

DP: Spark plug axial direction

Claims (14)

An auxiliary chamber combustion four-stroke engine is characterized by: The main combustion chamber is connected with an air intake passage and an exhaust passage; A throttle valve that adjusts the amount of air sucked into the main combustion chamber through the air intake passage; An intake passage injection valve that injects gasoline fuel, alcohol fuel, or liquid fuel as a gasoline/alcohol mixed fuel into the interior of the above-mentioned intake passage; An auxiliary chamber is formed in the cylinder head with a smaller volume than the above-mentioned main combustion chamber. Its internal space is connected to the internal space of the above-mentioned main combustion chamber through a plurality of communication holes, and a part of the spark plug in the auxiliary chamber is exposed to its internal space; and A control device that controls the above-mentioned intake passage injection valve and the above-mentioned auxiliary chamber spark plug; and The control device controls the intake passage injection valve so that the mixed gas mixed in the intake passage and the main combustion chamber becomes a combustion medium in at least a part of the low load area where the opening of the throttle valve is small. The first air-fuel ratio that can be processed by the three-way catalyst or the second air-fuel ratio that is richer than the above-mentioned first air-fuel ratio; The above-mentioned auxiliary chamber combustion four-stroke engine does not have any of the auxiliary chamber fuel injection valve for injecting fuel into the above-mentioned auxiliary chamber, nor the ignition auxiliary device for assisting the ignition of the mixed gas in the above-mentioned auxiliary chamber or the above-mentioned main combustion chamber; The cylinder head has a cooling portion that contains a cooling medium that receives heat from the electrode portion of the spark plug in the auxiliary chamber and the auxiliary chamber wall portion in which the plurality of communication holes are formed; The electrode portion of the sub-chamber spark plug is formed to generate a plurality of spark discharges dispersedly along the circumferential direction of the electrode portion; The plurality of communication holes are formed dispersedly along the circumferential direction; The cylinder head is formed such that a plurality of thermal paths from the electrode portion of the sub-chamber spark plug to the cooling portion and a plurality of thermal paths from the sub-chamber wall portion to the cooling portion are formed dispersedly in the circumferential direction. For example, the auxiliary chamber combustion four-stroke engine of claim 1, wherein the base material of the auxiliary chamber wall has a higher melting point than the base material of the cylinder head, and the value obtained by multiplying the specific heat and the specific gravity is higher than the base material of the cylinder head. High, the thermal conductivity is the same as or higher than that of chromium series stainless steel. For example, the auxiliary chamber combustion four-stroke engine of claim 1 or 2, in which, except for the spark plug of the auxiliary chamber, no protrusions are formed on the inner surface of the auxiliary chamber, and the spark plug shaft of the spark plug of the auxiliary chamber in the internal space of the above auxiliary chamber The length in the direction is less than twice the maximum length of the internal space of the auxiliary chamber in the direction orthogonal to the axial direction of the above-mentioned spark plug. The auxiliary chamber combustion four-stroke engine according to any one of claims 1 to 3, wherein the auxiliary chamber wall is formed to protrude toward the internal space of the main combustion chamber, The auxiliary chamber is formed on any plane that passes through the internal space of the auxiliary chamber without passing through the outer surface of the auxiliary chamber wall and is orthogonal to the axial direction of the spark plug of the auxiliary chamber spark plug. When the internal space is divided into two spaces, the volume of the space close to the main combustion chamber among the two spaces is smaller than the volume of the space further away from the main combustion chamber among the two spaces. The auxiliary chamber combustion four-stroke engine as claimed in any one of claims 1 to 4, wherein a plane passing through the cooling part and orthogonal to the spark plug axial direction of the auxiliary chamber spark plug passes through the auxiliary chamber spark plug. The auxiliary chamber combustion four-stroke engine as claimed in any one of claims 1 to 5, wherein the internal space of the auxiliary chamber is a space surrounded by auxiliary chamber components and the auxiliary chamber spark plug, and the auxiliary chamber components and part of the above-mentioned auxiliary chamber are exposed to The cylinder head body in the internal space of the main combustion chamber and the spark plug of the auxiliary chamber are both independent and include the wall of the auxiliary chamber. The auxiliary chamber combustion four-stroke engine of claim 6, wherein a plane passing through the cooling part and orthogonal to the axial direction of the spark plug of the auxiliary chamber spark plug passes through the auxiliary chamber member. The auxiliary chamber combustion four-stroke engine of claim 7, wherein a part of the inner surface of the cooling part is at least a part of the outer peripheral surface of the auxiliary chamber member. The auxiliary chamber combustion four-stroke engine according to any one of claims 6 to 8, wherein the male thread formed on the spark plug of the auxiliary chamber engages and contacts the female thread formed on the auxiliary chamber member. The auxiliary chamber combustion four-stroke engine of claim 9, wherein a plane passing through the cooling part and orthogonal to the axial direction of the spark plug of the auxiliary chamber spark plug passes through the male thread formed on the auxiliary chamber spark plug and is formed on the above The part where the above-mentioned female thread of the auxiliary chamber member engages and contacts. The auxiliary chamber combustion four-stroke engine as claimed in any one of claims 6 to 10, wherein the outer peripheral surface of the auxiliary chamber member is in contact with the cylinder head body. The auxiliary chamber combustion four-stroke engine of claim 11, wherein the plane passing through the internal space of the above auxiliary chamber and orthogonal to the axial direction of the spark plug of the above auxiliary chamber spark plug passes through the outer peripheral surface of the above auxiliary chamber member and the above cylinder head. The part where the body contacts. The auxiliary chamber combustion four-stroke engine of claim 12, wherein the plane passing through the internal space of the above auxiliary chamber and orthogonal to the axial direction of the above spark plug passes through the male thread formed in the above auxiliary chamber member and the thread formed in the above cylinder head body. The part where the female threads engage and contact. The auxiliary chamber combustion four-stroke engine according to any one of claims 1 to 13 does not have a main combustion chamber fuel injection valve for injecting fuel into the main combustion chamber.