JP2022001750A - Sub chamber type diesel engine - Google Patents

Abstract

To provide a sub chamber type diesel engine capable of preventing a nozzle part 4a of a fuel injector 4 from being overheated.SOLUTION: In a sub chamber type diesel engine, a nozzle part accommodating chamber 3a comprises a heat shield wall 3b that covers a tip surface 4b of a nozzle part 4a; the heat shield wall 3b is composed of a thick wall that comprises an injection fuel passage hole 3c and is continuous with the surrounding sub-chamber peripheral wall 2a; the nozzle part accommodating chamber 3a comprises a heat shield space 3d between the tip surface 4b of the nozzle part 4a and the heat shield wall 3b; and the heat shield space 3d communicates with a sub chamber 2 via the injection fuel passage hole 3c.SELECTED DRAWING: Figure 1

Description

The present invention relates to a sub-chamber diesel engine, and more particularly to a sub-chamber diesel engine in which the nozzle portion of a fuel injector is unlikely to overheat.

Conventionally, a sub chamber provided in the cylinder head, an injector insertion hole penetrating the cylinder head toward the sub chamber, a fuel injector inserted through the injector insertion hole, and an injector insertion hole for accommodating the nozzle portion of the fuel injector. There is a sub-chamber diesel engine provided with a nozzle housing (see, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2000-345940 (see FIGS. 1 and 2)

"problem"
Since the engine of Patent Document 1 is provided with a heat shield cap that covers the nozzle portion of the fuel injector, the heat of the heat shield cap, which is a separate component from the cylinder head, is not easily transferred to the cylinder head, the heat shield cap becomes hot, and the fuel injector becomes hot. The nozzle part of the engine tends to overheat.

An object of the present invention is to provide a sub-chamber diesel engine in which the nozzle portion of the fuel injector is less likely to overheat.

The main configurations of the present invention are as follows.
As illustrated in FIGS. 1 to 3, the nozzle portion accommodating chamber (3a) includes a heat shield wall (3b) that covers the tip surface (4b) of the nozzle portion (4a), and the heat shield wall (3b) allows injection fuel to pass through. It is provided with a hole (3c) and is composed of a wall of a cylinder head (1) that is continuous with the surrounding sub-chamber peripheral wall (2a).
The nozzle portion accommodating chamber (3a) is provided with a heat shield space (3d) between the tip surface (4b) of the nozzle portion (4a) and the heat shield wall (3b), and the heat shield space (3d) is an injection fuel passage hole (3c). A sub-chamber diesel engine characterized in that it communicates with the sub-chamber (2) via).

The invention of the present application has the following effects.
<< Effect 1 >> The nozzle portion (4a) of the fuel injector (4) is unlikely to overheat.
In this engine, as shown in FIGS. 1 to 3, the heat shield wall (3b) covering the tip surface (4b) of the nozzle portion (4a) is a cylinder head (1) continuous with the surrounding sub-chamber peripheral wall (2a). Since it is composed of a wall, the heat of the heat shield wall (3b) is dissipated to the cylinder head (1), the heat shield wall (3b) does not become hot, and the nozzle portion (4a) of the fuel injector (4) becomes hot. It is hard to overheat.

<< Effect 2 >> The overheat suppression function of the nozzle portion (4a) is high.
In this engine, the overheat suppression function of the nozzle portion (4a) shown in FIGS. 1 to 3 is high. The reason is presumed as follows.
In this engine, the high-pressure combustion gas generated in the sub chamber (2) near the compression top dead point tries to flow into the heat shield space (3d) from the injection fuel passage hole (3c) at high speed, so that the injection fuel passes. The pressure loss of the combustion gas passing through the hole (3c) becomes large, the inflow of the combustion gas into the heat shield space (3d) is suppressed, and a relatively large amount of low-temperature air described later remains in the heat shield space (3d). Due to the heat insulating action of this low temperature air, heat transfer from the heat insulating wall (3b) to the tip surface (4b) of the nozzle portion (4a) is suppressed. Then, the relatively low-pressure high-temperature air heated in the heat-shielding space (3d) during the combustion stroke tries to flow out from the injection fuel passage hole (3c) to the sub chamber (2) at a low speed in the exhaust stroke and the intake stroke. Therefore, the pressure loss of the high-temperature air passing through the injection fuel passage hole (3c) is reduced, and the outflow of the high-temperature air to the sub-chamber (2) is promoted. Then, in the first half of the compression stroke, relatively low-pressure low-temperature air pushed from the main combustion chamber (9) into the sub chamber (2) tries to flow into the heat-shielding space (3d) from the injection fuel passage hole (3c) at a low speed. Therefore, the pressure loss of the low-temperature air passing through the injection fuel passage hole (3c) is reduced, and the inflow of the low-temperature air into the heat-shielding space (3d) is promoted. Therefore, the exchange of the high temperature air in the heat shield space (3d) and the low temperature air in the sub chamber (2) is promoted, the nozzle portion (4a) is strongly cooled by the low temperature air, and the overheating of the nozzle portion (4a) is suppressed. To.

It is sectional drawing of the main part of the sub-chamber type diesel engine which concerns on 1st Embodiment of this invention. It is sectional drawing of the main part of the sub-chamber type diesel engine which concerns on 2nd Embodiment of this invention. It is sectional drawing of the main part of the sub-chamber type diesel engine which concerns on 3rd Embodiment of this invention.

1 to 3 are views for explaining a sub-chamber diesel engine according to an embodiment of the present invention, FIG. 1 shows a first embodiment, FIG. 2 shows a second embodiment, and FIG. 3 shows a third embodiment. There is. In this embodiment, a vertical water-cooled vortex chamber type diesel engine will be described.

First, the first embodiment will be described.
As shown in FIG. 1, the engine of the first embodiment includes a cylinder block (5), a cylinder head (1) assembled on the upper part of the cylinder block (5), and a piston head (8). ..

As shown in FIG. 1, the cylinder block (5) includes a cylinder portion (5a), and a piston head (8) is retractably fitted in the cylinder portion (5a) so as to be retractably fitted in the cylinder portion (5a). A main combustion chamber (9) sandwiched between a cylinder head (1) and a piston head (8) is formed.

As shown in FIG. 1, the cylinder head (1) includes a sub chamber (2).
The cylinder head (1) has a recessed portion (1b) recessed upward from the lower surface thereof, and has an upper hemispherical surface (1c) recessed upward on the inner side of the recessed portion (1b). A base (10) is internally fitted on the inlet side of (1b), and the base (10) has a lower hemisphere (10a) recessed downward from the upper side thereof, and has an upper hemisphere (1c) and a lower side. A spherical sub-chamber (2) is formed by the side hemisphere (10a).
The sub chamber (2) communicates with the main combustion chamber (9) by the nozzle (10b) of the base (10).
The nozzle portion (4a) of the fuel injector (4) faces the sub chamber (2), and the glow plug (12) is inserted.
As shown in FIG. 1, the fuel injection axis (4c) of the fuel injector (4) passes through the center point (2d) and the injection port (10b) of the vortex chamber (2) and is directed toward the main combustion chamber (9). Has been done.
The fuel injection axis (4c) of the fuel injector (4) may be directed to the main combustion chamber (9) through the central portion of the vortex chamber (2) and the injection port (10b). The central portion of the vortex chamber (2) means a region including the central point (2d) of the vortex chamber (2) and its periphery.

As shown in FIG. 1, the cylinder head (1) includes a head jacket (1a) that surrounds the sub chamber (2) from the surroundings, and the cylinder block (5) has a cylinder jacket (5a) that surrounds the cylinder portion (5a) from the surroundings. 5b) is provided. The cylinder jacket (5b) and the head jacket (1a) communicate with each other to form a water-cooled jacket (11), and the engine cooling water passing through the water-cooled jacket (11) is the cylinder portion (5a) and the cylinder head (1). ) Is water-cooled.

As shown in FIG. 1, this engine has a sub chamber (2) provided in the cylinder head (1), an injector insertion hole (3), and a fuel injector (4) inserted into the injector insertion hole (3). ) And the nozzle portion accommodating chamber (3a) of the injector insertion hole (3) accommodating the nozzle portion (4a) of the fuel injector (4).

As shown in FIG. 1, the nozzle portion accommodating chamber (3a) is provided with a heat shield wall (3b) that covers the tip surface (4b) of the nozzle portion (4a), and the heat shield wall (3b) is an injection fuel passage hole (3c). ), And is composed of a wall of the cylinder head (1) that is continuous with the surrounding sub-chamber peripheral wall (2a).
The nozzle portion accommodating chamber (3a) is provided with a heat shield space (3d) between the tip surface (4b) of the nozzle portion (4a) and the heat shield wall (3b), and the heat shield space (3d) is an injection fuel passage hole (3c). ) To communicate with the sub-room (2).

In this engine, as shown in FIG. 1, the heat shield wall (3b) covering the tip surface (4b) of the nozzle portion (4a) is a wall of the cylinder head (1) continuous with the surrounding sub-chamber peripheral wall (2a). Since the heat shield wall (3b) is easily transferred to the cylinder head (1), the heat shield wall (3b) does not easily reach a high temperature, and the nozzle portion (4a) of the fuel injector (4) overheats. hard.

In this engine, the overheat suppression function of the nozzle portion (4a) shown in FIG. 1 is high. The reason is presumed as follows.
In this engine, the high-pressure combustion gas generated in the sub chamber (2) near the compression top dead point tries to flow into the heat shield space (3d) from the injection fuel passage hole (3c) at high speed, so that the injection fuel passes. The pressure loss of the combustion gas passing through the hole (3c) becomes large, the inflow of the combustion gas into the heat shield space (3d) is suppressed, and a relatively large amount of low-temperature air described later remains in the heat shield space (3d). Due to the heat insulating action of this low temperature air, heat transfer from the heat insulating wall (3b) to the tip surface (4b) of the nozzle portion (4a) is suppressed. Then, the relatively low-pressure high-temperature air heated in the heat-shielding space (3d) during the combustion stroke tries to flow out from the injection fuel passage hole (3c) to the sub chamber (2) at a low speed in the exhaust stroke and the intake stroke. Therefore, the pressure loss of the high-temperature air passing through the injection fuel passage hole (3c) is reduced, and the outflow of the high-temperature air to the sub-chamber (2) is promoted. Then, in the first half of the compression stroke, relatively low-pressure low-temperature air pushed from the main combustion chamber (9) into the sub chamber (2) tries to flow into the heat-shielding space (3d) from the injection fuel passage hole (3c) at a low speed. Therefore, the pressure loss of the low-temperature air passing through the injection fuel passage hole (3c) is reduced, and the inflow of the low-temperature air into the heat-shielding space (3d) is promoted. Therefore, the exchange of the high temperature air in the heat shield space (3d) and the low temperature air in the sub chamber (2) is promoted, the nozzle portion (4a) is strongly cooled by the low temperature air, and the overheating of the nozzle portion (4a) is suppressed. To.

As shown in FIG. 1, the sub chamber (2) is a vortex chamber (2b), and the inner peripheral surface of the heat insulating wall (3ba) facing the vortex chamber (2b) and the vortex around the inner peripheral surface of the heat insulating wall (3ba). A spherical swirling flow guide surface (2c) is formed on the indoor peripheral surface (2ba).

In this engine, a spherical swirling flow guide surface (2c) formed by the inner peripheral surface of the heat insulating wall (3ba) shown in FIG. 1 and the peripheral surface of the vortex chamber (2ba) around the inner peripheral surface of the heat insulating wall (3ba). Since the swirling flow (6) of the compressed air in the vortex chamber (2b) swirls smoothly, the fuel (7) injected from the nozzle portion (4a) of the fuel injector (4) is smoothly swirled into the compressed air. The combustion performance is enhanced by promoting premixed combustion.
As a result, in this engine, it is possible to improve the engine output and reduce smoke.

As shown in FIG. 1, the tip surface (4b) of the nozzle portion (4a) is exposed toward the heat-shielding space (3d).
In this engine, the nozzle portion (4a) is cooled by the low-temperature air flowing into the heat-shielding space (3d) shown in FIG. 1 in the first half of the compression stroke, so that the nozzle portion (4a) has a high overheat suppression function.

Next, the engine of the second embodiment will be described.
The second embodiment of FIG. 2 has a ring-shaped ridge (3bb) added to the first embodiment of FIG. 1, and has the same configuration and function as the first embodiment in other respects. In FIG. 2, the same elements as those in the first embodiment of FIG. 1 are designated by the same reference numerals as those in FIG.
As shown in FIG. 2, the heat shield wall (3b) is provided with a ring-shaped ridge (3bb) approaching the tip surface (4b) of the nozzle portion (4a) at the peripheral edge of the injection fuel passage hole (3c). A throttle gap (3da) is formed between (3bb) and the tip surface (4b) of the nozzle portion (4a).

In the engine of the second embodiment of FIG. 2, the overheat suppressing function of the nozzle portion (4a) shown in FIG. 2 is high. The reason is presumed as follows.
In this engine, the throttle gap (3da) also functions in the same way as the injection fuel passage hole (3c), and the exchange of high temperature air in the heat shield space (3d) and low temperature air in the sub chamber (2) is promoted, and the nozzle portion (3da) 4a) has a high overheat suppression function.

Next, the engine of the third embodiment will be described.
The third embodiment of FIG. 3 has a heat insulating plate (3e) added to the first embodiment of FIG. 1, and has the same configuration and function as the first embodiment in other respects. In FIG. 3, the same elements as those in the first embodiment of FIG. 1 are designated by the same reference numerals as those in FIG.
In this engine, a metal heat insulating plate (3e) is housed in the heat insulating space (3d) shown in FIG. 3, and the heat insulating plate (3e) includes the tip surface (4b) of the nozzle portion (4a) and the heat insulating wall (3b). ) Is sandwiched between them.

In this engine, the overheat suppression function of the nozzle portion (4a) shown in FIG. 3 is high. The reason is presumed as follows.
In this engine, the heat of the high-pressure combustion gas generated in the sub chamber (2) during fuel injection of the fuel injector (4) is blocked by the heat shield plate (3e), so that the tip surface (4b) of the fuel injector (4) is blocked. ) Is difficult to convey. Further, the heat of the tip surface (4b) of the nozzle portion (4a) of the fuel injector (4) is cooled by the relatively low temperature air pushed into the heat shield space (3d) from the sub chamber (2) in the first half of the compression stroke. The heat is dissipated to the cylinder head (1) via the heat shield plate (3e) and the heat shield wall (3b) made of metal. For these reasons, in this engine, the overheat suppression function of the nozzle portion (4a) is high.

As shown in FIGS. 1 to 3, in each embodiment, the diameter of the minimum portion (3ca) of the injected fuel passage hole (3c) is 50% or more of the diameter of the tip surface (4b) of the nozzle portion (4a). The length is within the range of less than%.

In this engine, the overheat suppression function of the nozzle portion (4a) is high.
The reason is presumed as follows.
When the diameter of the minimum portion (3ca) of the injection fuel passage hole (3c) is less than 20% or more of the diameter of the tip surface (4b) of the nozzle portion (4a), the injection fuel passage hole (3c) becomes small. The fuel (7) injected too much comes into contact with the peripheral wall of the injected fuel passage hole (3c) and diffuses into the heat shield space (3d), and the temperature of the air in the heat shield space (3d) rises due to combustion. , There is a risk of overheating the nozzle portion (4a). On the other hand, when the diameter of the minimum portion (3ca) of the injection fuel passage hole (3c) is 50% or more of the diameter of the tip surface (4b) of the nozzle portion (4a), the injection fuel passage hole (3c) becomes It becomes too large, the inflow of combustion gas from the sub chamber (2) into the heat shield space (3d) is promoted, the temperature of the air in the heat shield space (3d) rises, and the nozzle portion (4a) may be overheated. .. On the other hand, the diameter of the minimum portion (3ca) of the injected fuel passage hole (3c) is 20% or more and less than 50% of the diameter of the tip surface (4b) of the nozzle portion (4a). If so, the above problem does not occur, and the overheat suppression function of the nozzle portion (4a) is high.
The injected fuel passage hole (3c) has a frustum shape in which the inner diameter gradually decreases from the sub chamber (2) toward the heat shield space (3d). Further, the tip surface (4b) of the nozzle portion (4a) is circular.

(1) ... Cylinder head, (2) ... Sub chamber, (2a) ... Sub chamber peripheral wall, (2b) ... Vortex chamber, (2ba) ... Vortex chamber peripheral surface, (2c) ... Swirling flow guide surface, (3) ... Injector insertion hole, (3a) ... Nozzle accommodation chamber, (3b) ... Heat shield wall, (3ba) ... Heat shield inner peripheral surface, (3bb) ... Ring-shaped ridge, (3c) ... Injection fuel passage hole, (3ca) ) ... Minimum part, (3d) ... Heat shield space, (3da) ... Squeeze gap, (3e) ... Heat shield plate, (4) ... Fuel injector, (4a) ... Nozzle part, (4b) ... Tip surface.

Claims (6)

A sub chamber (2) provided in the cylinder head (1), an injector insertion hole (3), a fuel injector (4) inserted into the injector insertion hole (3), and a nozzle portion of the fuel injector (4). In a sub-chamber type diesel engine provided with a nozzle portion accommodating chamber (3a) of an injector insertion hole (3) accommodating (4a).
The nozzle portion accommodating chamber (3a) is provided with a heat shield wall (3b) that covers the tip surface (4b) of the nozzle portion (4a), and the heat shield wall (3b) is provided with an injection fuel passage hole (3c) and surroundings. It is composed of a wall of the cylinder head (1) that is continuous with the peripheral wall of the sub-chamber (2a).
The nozzle portion accommodating chamber (3a) is provided with a heat shield space (3d) between the tip surface (4b) of the nozzle portion (4a) and the heat shield wall (3b), and the heat shield space (3d) is an injection fuel passage hole (3c). A sub-chamber diesel engine characterized in that it communicates with the sub-chamber (2) via). In the sub-chamber diesel engine according to claim 1,
The sub chamber (2) is a vortex chamber (2b), and the inner peripheral surface of the heat insulating wall (3ba) facing the vortex chamber (2b) and the peripheral surface of the vortex chamber (2ba) around the inner peripheral surface of the heat insulating wall (3ba). , A sub-chamber type diesel engine characterized in that a spherical swirling flow guide surface (2c) is formed. In the sub-chamber diesel engine according to claim 1 or 2.
A sub-chamber diesel engine characterized in that the tip surface (4b) of the nozzle portion (4a) is exposed toward the heat-shielding space (3d). In the sub-chamber diesel engine according to any one of claims 1 to 3.
The heat shield wall (3b) is provided with a ring-shaped ridge (3bb) approaching the tip surface (4b) of the nozzle portion (4a) at the peripheral edge of the injection fuel passage hole (3c), and the ring-shaped ridge (3bb) and the nozzle portion (3b). A sub-chamber diesel engine characterized in that a throttle gap (3da) is formed between the tip surfaces (4b) of 4a). In the sub-chamber diesel engine according to any one of claims 1 to 3.
A metal heat shield plate (3e) is housed in the heat shield space (3d), and the heat shield plate (3e) is sandwiched between the tip surface (4b) of the nozzle portion (4a) and the heat shield wall (3b). A sub-chamber diesel engine that is characterized by being. In the sub-chamber diesel engine according to any one of claims 1 to 5.
The diameter of the minimum portion (3d) of the injection fuel passage hole (3c) is 20% or more and less than 50% of the diameter of the tip surface (4b) of the nozzle portion (4a). It features a sub-chamber diesel engine.

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