Direct-injection diesel engine and combustion method for the same

• US 6,161,518 A
• Filed: 03/26/1999
• Issued: 12/19/2000
• Est. Priority Date: 03/27/1998
• Status: Expired due to Term

• Current Assignee: Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Original Assignee: Kabushiki Kaisha Toyota Chuo Kenkyusho (Toyota Motor Corporation)
• Inventors: Hotta, Yoshihiro, Inagaki, Kazuhisa, Nakakita, Kiyomi, Inayoshi, Minaji, Fuyuto, Takayuki
• Primary Examiner(s): Yuen, Henry C.
• Assistant Examiner(s): Vo, Hieu T.
• Application Number:
  US09/276,732
• Time in Patent Office: 634 Days
• Field of Search: 123/298, 123/276, 123/279, 123/261, 123/285
• US Class Current: 123/298
• CPC Class Codes: F02B 2275/14 Direct injection into combustion chamber
• CPC Class Codes: F02B 23/0621 Squish flow
• CPC Class Codes: F02B 23/0651 the fuel spray impinging on reflecting surfaces or being specially guided throughout the combustion space
• CPC Class Codes: F02B 23/0672 Omega-piston bowl, i.e. the combustion space having a central projection pointing towards the cylinder head and the surrounding wall being inclined towards the cylinder center axis the surrounding wall being exactly vertical F02B23/0696
• CPC Class Codes: F02B 23/0696 W-piston bowl, i.e. the combustion space having a central projection pointing towards the cylinder head and the surrounding wall being inclined towards the cylinder wall
• CPC Class Codes: F02B 3/06 with compression ignition compression ignition engines using air or gas for blowing fuel into compressed air in cylinder F02B13/02
• CPC Class Codes: F02F 2001/245 the valve stems being orientated at an angle with the cylinder axis
• CPC Class Codes: Y02T 10/12 Improving ICE efficiencies

Abstract

A direct-injection diesel engine in which a shallow-dish type piston cavity is formed on a top surface of a piston; wherein in the vicinity of the top dead center, a squish area is defined mainly by the top surface of the piston and an inner surface of a cylinder head opposite the top surface; when a velocity of a reverse squish flow from the shallow-dish type piston cavity to the squish area, generated due to a movement of the piston and is represented by Vs, and a fuel spray velocity in the vicinity of a lip portion of the shallow-dish type piston cavity is represented by Vsp, the distance between opposite wall portions of the shallow-dish type piston cavity is set such that the ratio Vs/Vsp is not greater than 1.25; and the squish area constitutes a part of the combustion chamber.

Claims

1. A direct-injection diesel engine comprising:

a combustion chamber defined by a piston, a cylinder head, and a cylinder liner;

a shallow-dish type piston cavity formed on a top surface of said piston;

a squish area defined by said top surface of said piston and said cylinder head in the vicinity of a compression top dead center;

a fuel injector for injecting fuel into said combustion chamber to combust in a fuel-air mixture state;

wherein;

a distance between opposite wall surfaces of said shallow-dish type piston cavity is set such that ratio Vs/Vsp is not greater than 1.25, in order to use said squish area effectively as a part of said combustion chamber by dispersing and burning a fuel uniformly within said shallow-dish type piston cavity and said squish area;

where;

Vs is a velocity of the reverse squish flow flowing from said shallow-dish type piston cavity to said squish area due to a movement of said piston; and

Vsp is a fuel spray velocity in the vicinity of a lip portion of said shallow-dish type piston cavity.

2. A direct-injection diesel engine according to claim 1, wherein

a specific power is set to 40 KW/l or higher.

3. A direct-injection diesel engine according to claim 1, wherein

a ratio of a minimum diameter of an inlet of the shallow-dish type piston cavity to a depth of the shallow-dish type piston cavity is set to 3.3 or higher.

4. A direct-injection diesel engine according to claim 1, wherein

a ratio of a minimum diameter of an inlet of the shallow-dish type piston cavity to a depth of the shallow-dish type piston cavity is set to 3.5 or higher.

5. A direct-injection diesel engine according to claim 1, wherein

a ratio of a minimum diameter of the shallow-dish type piston cavity inlet to a bore diameter of the cylinder is set to 0.5 or higher.

6. A direct-injection diesel engine according to claim 1, wherein

a ratio of a minimum diameter of the shallow-dish type piston cavity inlet to a bore diameter of the cylinder is set to 0.52 or higher.

7. A direct-injection diesel engine according to claim 1, wherein

a nozzle hole diameter of said fuel injector is set to 0.2 mm or less.

8. A direct-injection diesel engine according to claim 1, wherein

a nozzle hole diameter of said fuel injector is set to 0.15 mm or less.

9. A direct-injection diesel engine according to claim 1, wherein

the squish velocity Vs is a maximum value of the squish velocity.

10. A direct-injection diesel engine according to claim 1, wherein

the fuel spray velocity Vsp is calculated as a fuel spray velocity for a case where a radius of the lip portion is regarded as the fuel spray reach distance S.

11. A direct-injection diesel engine according to claim 1, wherein

the ratio Vs/Vsp is a value which is obtained at a maximum output.

12. A direct-injection diesel engine according to claim 1, wherein

said lip portion of said shallow-dish type piston cavity comprises a small lip formed by the difference of maximum diameter and minimum diameter of said shallow-dish type piston cavity in order to cause the reverse squish flow from said shallow-dish type piston to said squish area.