JPH04353232A - Direct-injection type diesel engine - Google Patents

Abstract

PURPOSE:To suppress maximum pressure in a piston combustion chamber to reduce NOx, in a direct-injection type diesel engine. CONSTITUTION:A cylindrical recess 22 is formed in the bottom center of a piston combustion chamber 10, and a slider 28 is inserted into the cylindrical recess 22 so that it can slide on the external surface of a shaft portion 18 of a pin 14 and the internal surface of the cylindrical recess 22. A disc spring 26 energizes the slider 28 toward the bevel portion 16 of the pin 14.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a direct injection diesel engine, and more particularly to a direct injection diesel engine equipped with a piston combustion chamber of variable volume.

0002

2. Description of the Related Art A conventional piston combustion chamber of a direct injection diesel engine has a fixed volume and does not increase or decrease depending on operating conditions.

0003

The amount of NOx (nitrogen oxides) generated by a direct injection diesel engine increases as the maximum pressure in the combustion chamber increases. In conventional direct injection diesel engines, the maximum pressure in the piston combustion chamber is not suppressed, which increases the amount of NOx produced.

[0004] An object of the present invention is to provide a direct injection diesel engine that can reduce NOx by suppressing the maximum pressure in a piston combustion chamber.

[0005]

[Means for Solving the Problems] A direct injection diesel engine of the present invention has the following components (a) and (b). (a) A displacement member that is displaceably disposed on the piston and increases or decreases the volume of the piston combustion chamber. (b) A biasing member that biases the displacement member in the direction of decreasing the volume of the piston combustion chamber.

[0006]

[Operation] The displacement member receives the pressure of the piston combustion chamber from the piston combustion chamber side, and is displaced against the biasing member as the pressure of the piston combustion chamber increases. This increases the volume of the piston combustion chamber.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the embodiment shown in FIG. FIG. 1 is a vertical cross-sectional view of a piston 12 of a direct injection diesel engine. The piston combustion chamber 10 is formed in the piston 12 so as to open at the top surface of the piston 12, and has a heart-shaped vertical cross section. The pin 14 is arranged with its center line aligned with the center line of the piston combustion chamber 10, and includes an upper umbrella portion 16, a shaft portion 18 extending downward from the umbrella portion 16, and a screw thread at the lower end of the shaft portion 18. It is screwed onto the piston 12 in the groove 20. The cylindrical recess 22 is formed in the center of the bottom of the piston combustion chamber 10 concentrically with respect to the pin 14, and the cylindrical recess 22 includes spring seats 2 in order from the bottom.
4. A disc spring 26 and a slider 28 are provided. The slider 28 has the shaft portion 18 of the pin 14 on the inner and outer peripheries, respectively.
and slides around the periphery of the cylindrical recess 22,
The lower surface of the umbrella portion 16 serves as a stopper for the slider 28 on the upper side. The disc spring 26 is loaded with a predetermined residual load, is interposed between the spring seat 24 and the lower surface of the slider 28, and urges the slider 28 toward the umbrella portion 16. Cylindrical recess 2
2 is in contact with the umbrella part 16, the slope of the slider 28 smoothly connects to the wall surface around the bottom of the piston combustion chamber 10 and the slope of the umbrella part 16. Form a central bulge.

[0008] The operation of the embodiment will be explained. The slider 28 is inserted into the piston combustion chamber 10 from the piston combustion chamber 10 side.
subject to pressure. When the pressure in the piston combustion chamber 10 is less than a predetermined value, the slider 28 is in contact with the lower surface of the umbrella portion 16 due to the biasing force of the disc spring 26, and the volume of the piston combustion chamber 10 is at a minimum value. When the pressure in the piston combustion chamber 10 exceeds a predetermined value, the slider 28 moves toward the spring seat 24 against the disc spring 26, and the volume of the piston combustion chamber 10 increases accordingly. Thereby, the maximum pressure in the piston combustion chamber 10 is suppressed.

[0009]

[Effects of the Invention] In this invention, the displacement member receives the pressure of the piston combustion chamber from the piston combustion chamber side.
Since the piston is displaced in the direction of increasing the volume of the piston combustion chamber against the biasing member, the maximum pressure of the piston combustion chamber is suppressed, and as a result, the amount of NOx generated can be suppressed.

[Brief explanation of drawings]

FIG. 1 is a vertical cross-sectional view of a piston of a direct injection diesel engine.

[Explanation of symbols]

10 Piston combustion chamber 12 Piston 26 Disc spring (biasing member) 28 Slider (displacement member)

Claims (1)

[Claims] 1. A piston comprising: a displacement member which is displaceably disposed on the piston and increases or decreases the volume of the piston combustion chamber; and a biasing member which biases the displacement member in a direction to decrease the volume of the piston combustion chamber. A direct injection diesel engine with the following features: