CROSS-REFERENCE TO RELATED APPLICATION

The present application is based on, and claims priority from, Japanese Patent Application Serial Number 2018-242548, filed on Dec. 26, 2018, the disclosure of which is hereby incorporated by reference herein in its entirety.

FIELD

A present disclosure relates to an internal combustion engine, and more particularly, to a compressed self-ignition type internal combustion engine which performs combustion by directly injecting fuel into a compressed combustion chamber. Background.

BACKGROUND

For example, US2017/0114763A discloses a technique for promoting premixing of fuel and charge air in a combustion chamber of a compressed self-ignition type internal combustion engine. In this technique, a duct constituted by a hollow tube is provided in the vicinity of an opening of a distal end portion of a fuel injection device exposed to a combustion chamber. The fuel injected from the opening is injected into the combustion chamber through the hollow tube. Inside the hollow tube, premixing with the filling air is promoted during the passage of the injected fuel. In this technique, a glow plug for assisting the ignition of the mixed gas of the fuel and the filling air is disposed on the downstream side of the duct. As a result, the ignitability of the mixed gas is improved.

SUMMARY

However, in the above technique, the mixed gas after passing through the duct is heated by the glow plug. The mixed gas after passing through the duct is susceptible to airflow in the combustion chamber. Therefore, in the above technique, heating of the mixed gas becomes insufficient, which may cause misfire.

The present disclosure has been made in view of the above-mentioned problems, and an object thereof is to provide a compressed self-ignition type internal combustion engine capable of suppressing the generation of smoke and improving ignitability.

In order to achieve the above object, a first disclosure is applied to a compressed self-ignition type internal combustion engine configured to perform combustion by injecting fuel into a compressed combustion chamber. The internal combustion engine includes a fuel injection nozzle having a plurality of injection holes for injecting fuel, and a plurality of hollow ducts configured to expose an inlet and an outlet to the combustion chamber. The fuel injection nozzle is provided so that a plurality of injection holes are exposed from the cylinder head of the internal combustion engine to the combustion chamber. The plurality of ducts are configured such that each fuel spray injected from the plurality of injection holes of the fuel injection nozzle passes from the inlet to the outlet. The internal combustion engine includes a heating device for heating at least one of the plurality of ducts.

A second disclosure has the following features in the first disclosure.

The plurality of ducts includes a first duct and a second duct having a duct length shorter than that of the first duct. The heating device is configured to heat the second duct.

A third disclosure has the following features in the first or second disclosure.

The plurality of ducts includes a small diameter duct and a large diameter duct having an inner diameter larger than that of the small diameter duct. The heating device is configured to heat the large diameter duct.

A fourth disclosure has the following features in any one of the first to third disclosures.

The plurality of ducts includes a low thermal conductivity duct and a high thermal conductivity duct having a higher thermal conductivity than the low thermal conductivity duct. The heating device is configured to heat the high thermal conductivity duct.

In order to achieve the above object, a fifth disclosure is applied to a compressed self-ignition type internal combustion engine configured to perform combustion by injecting fuel into a compressed combustion chamber. The internal combustion engine includes a fuel injection nozzle having a plurality of injection holes for injecting fuel, the plurality of injection holes being provided so as to be exposed from a cylinder head of the internal combustion engine to the combustion chamber; and a plurality of hollow ducts configured so that inlets and outlets are exposed to the combustion chamber. The plurality of ducts are configured such that each fuel spray injected from the plurality of injection holes of the fuel injection nozzle passes from the inlet to the outlet. The plurality of ducts are configured to include a low-ignitability duct having different ignition properties of the fuel spray that has passed therethrough and a high-ignitability duct. The internal combustion engine includes a heating device exposed at the outlet of the high-ignitability duct.

A sixth disclosure has the following features in the fifth disclosure.

The high-ignitability duct is configured to have a shorter duct length than the low-ignitability duct.

A seventh disclosure has the following features in the fifth or sixth disclosure.

The high-ignitability duct is configured to have a larger inner diameter than the low-ignitability duct.

An eighth disclosure has the following features in any one of the fifth to seventh disclosures.

The high-ignitability duct is configured to have a higher thermal conductivity than the low-ignitability duct.

In order to achieve the above object, a ninth disclosure is applied to a compressed self-ignition type internal combustion engine configured to perform combustion by injecting fuel into a compressed combustion chamber. The internal combustion engine includes a fuel injection nozzle and a hollow duct. The fuel injection nozzle has a plurality of injection holes for injecting fuel, and the injection holes is provided so as to be exposed from a cylinder head of the internal combustion engine to the combustion chamber. The duct is provided so that an inlet and an outlet are exposed to the combustion chamber and fuel spray injected from the injection holes of the fuel injection nozzle passes from the inlet to the outlet. The plurality of injection holes are provided so that each fuel spray is injected radially toward a bore wall surface of the combustion chamber. The duct is disposed corresponding to a part of the plurality of injection holes. The internal combustion engine includes a heating device for heating a fuel spray injected from an injection hole in which the duct is not arranged among the plurality of injection holes.

According to the first aspect of the present disclosure, the internal combustion engine includes the heating device for heating at least one of the plurality of ducts. As a result, the fuel spray passing through the duct may be heated by the inner wall surface of the duct. Thereby, premixing with the filling air is promoted while the fuel spray is heated, so that generation of smoke may be suppressed and ignitability may be improved.

The shorter the duct length, the smaller the effect of extending the ignition position. Therefore, the second duct has a higher ignition performance in the cold state of the internal combustion engine as compared with the first duct. According to the second aspect, the heating device is configured to heat the second duct. According to such a configuration, the ignitability of the second duct may be further improved. Thereby, simultaneous formation of spraying in which the ignition position is extended by passing through the first duct and spraying in which the ignitability is improved by passing through the second duct may be performed, and therefore, both suppression of smoke and improvement of ignitability may be achieved.

The larger the duct inner diameter, the smaller the effect of extending the ignition position. Therefore, the large diameter duct has a higher ignition performance in the cold state of the internal combustion engine as compared with the small diameter duct. According to the third aspect, the heating device is configured to heat the large diameter duct. According to such a configuration, the ignitability of the large diameter duct may be further improved. As a result, it is possible to simultaneously form the spray in which the ignition position is extended by passing through the small diameter duct and the spray in which the ignitability is improved by passing through the large diameter duct, so that both suppression of smoke and improvement of the ignitability may be achieved.

The higher the thermal conductivity of the duct, the smaller the effect of extending the ignition position. Therefore, the high thermal conductivity duct has a higher ignition performance in the cold state of the internal combustion engine as compared with the low thermal conductivity duct. According to a fourth aspect, the heating device is configured to heat the high thermal conductivity duct. According to such a configuration, the ignitability of the high thermal conductivity duct may be further improved. As a result, simultaneous formation of spraying in which the ignition position is extended by passing through the low thermal conductivity duct and spraying in which the ignitability is improved by passing through the high thermal conductivity duct is possible, so that both suppression of smoke and improvement of ignitability may be achieved.

According to a fifth aspect of the present disclosure, an internal combustion engine includes a heating device exposed at an outlet of a highly ignitable duct among a plurality of ducts. This makes it possible to heat the fuel spray that has passed through the highly ignitable duct. As a result, it is possible to simultaneously form the spray in which the ignition position is extended by passing through the low-ignitability duct and the spray in which the ignitability is improved by passing through the high-ignitability duct, so that both suppression of smoke and improvement of the ignitability may be achieved.

The shorter the duct length, the smaller the effect of extending the ignition position. Therefore, a second duct (i.e. the high-ignitability duct) having a duct length shorter than that of a first duct (i.e. the low-ignitability duct) has a higher ignitability of the internal combustion engine during cold operation than the first duct. According to the sixth aspect, the heating device is provided so as to be exposed at the outlet portion of the second duct. According to such a configuration, the ignitability of the fuel spray passing through the second duct may be further improved. Thereby, simultaneous formation of spraying in which the ignition position is extended by passing through the first duct and spraying in which the ignitability is improved by passing through the second duct may be performed, and therefore, both suppression of smoke and improvement of ignitability may be achieved.

The larger the duct inner diameter, the smaller the effect of extending the ignition position. Therefore, the large diameter duct (i.e. the high-ignitability duct) having an inner diameter larger than that of a small diameter duct (i.e. the low-ignitability duct) has a higher ignition performance in the cold state of the internal combustion engine as compared with the small diameter duct. According to the seventh aspect of the present disclosure, the heating device is provided so as to be exposed at the outlet portion of the large diameter duct. According to such a configuration, the ignitability of the large diameter duct may be further improved. As a result, it is possible to simultaneously form the spray in which the ignition position is extended by passing through the small diameter duct and the spray in which the ignitability is improved by passing through the large diameter duct, so that both suppression of smoke and improvement of the ignitability may be achieved.

The higher the thermal conductivity of the duct, the smaller the effect of extending the ignition position. Therefore, a high thermal conductivity duct (i.e. the high-ignitability duct) having a high thermal conductivity than a low thermal conductivity duct (i.e. the low-ignitability duct) has a higher ignition performance in the cold state of the internal combustion engine as compared with the low thermal conductivity duct. According to the eighth aspect of the present disclosure, the heating device is provided so as to be exposed at the outlet portion of the high thermal conductivity duct. According to such a configuration, the ignitability of the high thermal conductivity duct may be further improved. As a result, simultaneous formation of spraying in which the ignition position is extended by passing through the low thermal conductivity duct and spraying in which the ignitability is improved by passing through the high thermal conductivity duct is possible, so that both suppression of smoke and improvement of ignitability may be achieved.

The fuel spray that does not pass through the duct has a higher ignition performance in the cold state of the internal combustion engine as compared with the fuel spray that passes through the duct. According to the ninth aspect of the present disclosure, since the fuel spray that does not pass through the duct may be heated by the heating device, the ignitability of the fuel spray that does not pass through the duct may be further improved. As a result, it is possible to simultaneously form the spray in which the ignition position is extended by passing through the duct and the spray in which the ignitability is improved without passing through the duct, and therefore it is possible to achieve both suppression of smoke and improvement of the ignitability.

