JPS632008B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a combustion chamber of a diesel engine in which fuel is directly injected and supplied to a combustion chamber recessed in the top surface of a piston.

Examples of the combustion chamber of this type of diesel engine include those described in Japanese Patent Publications No. 49-16881 and Japanese Patent Publication No. 42249-1982. Here, in the former case, the side surface of the combustion chamber, which is the collision surface of the fuel spray, is inclined in the direction of the vortex to promote the vortex flow of air. The side surface of the fuel tank is flat so that the fuel collides with it at an angle.

Therefore, although all of these have the advantage of improving the mixing performance of fuel and air to some extent, the former leaves a protrusion on the side of the combustion chamber that tends to become a heat spot. The protrusion becomes the starting point for cracks in the piston, or
There was a risk that the protrusion would be damaged by melting. Moreover, in the latter case, corners are left on the side surfaces of the combustion chamber, which causes incomplete combustion and tends to deteriorate exhaust characteristics.

In order to avoid this situation, for example, as seen in Japanese Utility Model Application Publication No. 56-2020, a constriction extending toward the center is provided on the entire periphery of the inlet of the combustion chamber, while a constriction is provided on the side of the combustion chamber. It is effective to leave the side surfaces as surfaces between the provided recesses.

However, even in such conventional examples, the shape of the impact surface of the fuel spray injected from each nozzle was standardized by matching the number of recesses and the number of nozzles provided in the nozzle. Under certain operating conditions, the fuel spray is ideally diffused and a mixture with properties suitable for ignition is produced, but if the operating conditions change, the fuel spray diffusion conditions change and the mixture is Since the properties change, it may not always be possible to obtain an air-fuel mixture with properties suitable for ignition, which has the problem of deteriorating ignition performance and lengthening the ignition delay period.

In addition, when a concave portion is provided corresponding to each nozzle in this manner, there is also a risk that the properties of the air-fuel mixture may deteriorate due to nozzle assembly errors, resulting in difficulty in ignition.

The present invention has been made in view of the above circumstances, and includes providing a constriction toward the center on the entire periphery of the entrance of the combustion chamber, and at the same time providing a plurality of recesses on the side surface of the combustion chamber, and providing space between these recesses. In each case, at least the sides of the combustion chamber remain as surfaces. Furthermore, by varying the number of the recesses and the number of nozzles provided in the nozzle, the shape of the collision surface of the fuel spray injected from each nozzle is made different for each collision position.

In this way, the constriction is provided around the entire periphery of the inlet of the combustion chamber, making it possible to obtain a tight squeeze.Furthermore, the provision of the concave portion generates a small vortex due to the swirl, which improves the interaction between the fuel spray and the air. Mixing performance is improved. In addition, because the shape of the impact surface of the fuel spray differs depending on the impact location, mixtures with various properties are always generated, and under any operating conditions, at least one spot will not be able to ignite. A mixture of suitable properties exists. Therefore, the first stage combustion can be kept small (the ignition delay period can be shortened), and the fuel consumption rate can be improved while reducing the exhaust gas components generated by combustion.

Embodiments of the present invention will be described in detail below based on the drawings.

A piston 1 that reciprocates within a cylinder (not shown)
A combustion chamber 3 is recessed in the top surface of the combustion chamber, with a constriction part 2 extending toward the center formed around the entire periphery of the inlet part.
A nozzle 4 for injecting fuel toward the side surface of the combustion chamber 3 is attached to a cylinder head (not shown) to constitute a diesel engine.

Further, concave portions 5 continuous to the side surface are provided at a plurality of locations on the side surface of the combustion chamber 3, and at least the side surface is left as a surface (side surface) 6 between adjacent concave portions 5. The recess 5 is composed of a curved surface having a smaller radius than the curved surface forming the side surface 6 of the combustion chamber 3, and the connecting portion between the recess 5 and the side surface 6 is cut into, for example, an arc shape to connect the recess 5 and the side surface 6. To ensure smooth continuity, it is necessary to leave side surfaces 6 between adjacent recesses 5, and by forming these recesses 5, the width of the narrowed portion 2 is partially increased.
Although the number of recesses 5 varies depending on the size of the combustion chamber 3, by making the number of recesses 5 larger or smaller than the number of nozzles provided in the nozzle 4, collision of fuel sprays injected from each nozzle can be prevented. The shape of the surface differs depending on the collision location.

In the above configuration, the fuel spray 7 injected from the nozzle 4 is mixed with air while being swept away by the swirl, and a part of it collides with the side surface 6 of the combustion chamber 3 and is reflected toward the center. At this time, the collision conditions (the shape of the collision surface) of the fuel spray from each nozzle can be varied by, for example, making the number of nozzles 4 and the number of recesses 5 different by one and forming them equally spaced. Because of this, a mixture with different properties is generated depending on the collision location. Therefore, even when the operating conditions of the engine change, the properties of the air-fuel mixture become ideal in at least one location, and the mixture steadily ignites and starts combustion. For this reason, the ignition delay period is shortened and combustion becomes smoother under any operating conditions.

Further, since the length of the throttle part 2 is partially increased by providing the recess 5, sufficient squishing occurs and combustion efficiency is improved. Since the inner surface of the combustion chamber has a smooth uneven shape due to the provision of the recess 5, a local vortex (small vortex) is caused by the swirl and adheres to the side surface of the combustion chamber. Fuel evaporation is promoted and the combustion period is shortened. Furthermore, since it is possible to obtain a sufficiently strong squeeze as described above without increasing the overall size of the constriction, the flame that was once confined in the combustion chamber by the constriction can be released at an appropriate time. It also erupts in the Sukitsuyu area. For this reason, the generation of exhaust gas components is suppressed, and at the same time, the air utilization rate is increased, and the exhaust gas concentration and fuel consumption rate are improved. Furthermore, since a part of the side surface 6 of the combustion chamber 3 is left as a surface between the recesses 5, the combustion chamber has a shape that is advantageous in terms of heat load.

As explained above, according to the present invention, it is possible to obtain strong squishing without making the throttle part very large, and also to induce local vortices (turbulence) by the vortices generated in the combustion chamber, so that air and fuel This allows for good mixing with the flame, and also prevents the flame confinement period from becoming excessively long. For this reason, the generation of exhaust gas components can be suppressed without delaying the fuel injection timing, and combustion efficiency is increased to improve fuel consumption rate and exhaust gas concentration. Furthermore, since there are no edges or corners on the inner surface of the combustion chamber, there are no heat spots, and at the same time, the amount of unburned components emitted due to incomplete combustion can be reduced. Furthermore, by varying the number of nozzles provided in the nozzle and the number of recesses provided on the side surface of the combustion chamber, the shape of the collision surface of the fuel spray injected from the nozzle can be varied depending on the collision position. Therefore, even if the diffusion state of the fuel spray changes as the engine operating conditions change, air-fuel mixtures with various properties are still generated within the combustion chamber. Therefore, under any operating conditions, an air-fuel mixture with properties suitable for ignition exists in at least one location, reducing ignition delay and improving engine output characteristics, exhaust characteristics, fuel consumption rate, etc. Everything can be improved. Furthermore,
By varying the number of nozzles and the number of recesses, the shape of the collision surface of the fuel spray from each nozzle is made to differ, so even if the nozzle assembly error becomes large, the overall The diffusion state (reflection state) of the fuel spray does not change significantly.
Therefore, the nozzle assembly tolerance can be increased, the nozzle assembly work efficiency can be increased, and the manufacturing cost of the diesel engine can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a piston equipped with an embodiment of the present invention, FIG. 2 is a sectional view of FIG. 1, and FIG.
This is a sectional view of the figure. 1... Piston, 2... Throttle part, 3... Combustion chamber, 4...
Nozzle, 5... recess, 6... side surface.

Claims (1)

[Claims] 1. In a diesel engine in which a combustion chamber is recessed in the top surface of the piston and a nozzle is provided for injecting fuel toward the side surface of the combustion chamber, a throttle portion extending toward the center is provided on the entire periphery of the inlet portion of the combustion chamber. a collision surface of fuel spray injected from each nozzle by forming recesses continuous with the side surface at a plurality of positions on the side surface of the combustion chamber, and making the number of nozzles provided in the nozzle different from the number of the recesses; A combustion chamber for a diesel engine, characterized in that the shape of the combustion chamber differs depending on the collision position, and at least a side surface of the combustion chamber is left between adjacent recesses as a surface.