GB2404694A - Method of phasing a camshaft - Google Patents

Abstract

A method of phasing a camshaft comprises the following steps: setting the centre line of an injector cam at about 48.5 degrees past top dead centre; starting an exhaust profile at about 78.5 degrees past TDC, opening the exhaust valve at about 110 degrees, with maximum lift occurring at about 174.5 degrees; ending an injection profile at about 228.5 degrees; closing the exhaust valve at about 238.5 degrees; ending the exhaust profile at about 256.5 degrees; and ending the injection profile at about 317.5 degrees.

Description

2404694

LOW EMISSION FUEL EFFICIENT DIESEL LOCOMOTIVE ENGINE INCLUDING A PISTON HAVING A TOROIDAL SURFACE

CROSS-REFERENCE TO RELATED APPLICATIONS 5 [0001] This application claims the benefit of U.S. Provisional

Application No. 60/286,933 filed 27 April 2001.

FIELD OF THE INVENTION

[0002] The present invention relates to combustion engines, £nd„ 10 more particularly to a diesel locomotive engine having a piston with a bowl geometry.

BACKGROUND OF THE INVENTION

[0003] The use of a compression ratio piston with higher injection 15 pressures is an acceptable method for achieving emission reduction in a diesel engine. However, raising the compression ratio also creates smoke of particulate matter. Furthermore, increasing the injection pressures results in reduction of particulate with an increase in NO* emissions.

20 SUMMARY OF THE INVENTION

[0004] The present invention includes a diesel locomotive engine including a piston having a unique bowl geometry. A piston according to the present invention includes an upper face having a center portion that is partially spherical in shape. A cone portion is adjacent to the center portion.

25 An annular toroidal surface is formed adjacent to the cone portion and is

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defined by a toroidal major diameter and a toroidal minor radius. A crown rim is adjacent the annular toroidal surface. The geometry of the piston bowl provides increased compression ratio and at the same time low emissions and high fuel efficiency.

5 [0005] Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the 10 invention.

BRIEF DESCRIPTION OF THE DRAWINGS [0006] The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein: 15 [0007] Figure 1 is an elevational view generally showing the piston of the present invention;

[0008] Figure 2 illustrates a piston having a bowl geometry including a toroidal surface according to one presently preferred embodiment of the present invention; and 20 [0009] Figure 3 is a camshaft timing diagram illustrating the timing sequence of one presently preferred embodiment of the present invention.

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DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. Figure 1 shows a piston generally indicated at 10. The

5 piston 10 may be used in an internal combustion engine, such as a locomotive engine. As is known in the art, the engine may have a plurality of cylinders each for receiving a piston 10. The cylinders may be configured in a traditional V-12 design, or any other design.

[0011] The piston 10 includes a generally annular sidewall 12 10 having a plurality of grooves 14 thereon. The grooves are for receiving a plurality of rings to seal the piston 10 against the sidewall of the cylinder, as is well known in the art. The piston 10 also includes a top wall 16 at the top of annular sidewall 12. A connecting rod 18 may also be pivotally secured to the piston 10 in a conventional manner.

15 [0012] As shown in Figure 2, the top wall 16 of the piston includes a center portion 20 having a partially spherical shape. Preferably, the center portion has a spherical radius Rc of about three inches. A cone portion 22 is connected to the center portion 20 and preferably is formed at an angle Ac of about 14 degrees. An annular toroidal surface 24 is formed adjacent to the 20 cone portion 22 and is defined in part by a toroidal major diameter Dt™ of about 0.822 inches and a toroidal minor radius Rtm of about 0.77 inches. A crown rim 26 is formed adjacent to the annular toroidal surface 24 and is connected to an upper flat rim face of sidewall 12. The crown rim 26 preferably has a radius Rcr of about 0.38 inches.

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[0013] The annular toroidal surface 24 is preferably formed wherein the toroidal minor radius is measured from a point that is submerged approximately 0.496 inches below the upper flat rim face. This is also known as the toroidal submersion below squish land and is denoted as Ts in Figure

5 2. Preferably a piston 10 having a bowl configuration as described above would have a bowl volume of approximately 35.185 cubic inches.

[0014] One unique feature of the above-stated dimensions provides the ability to retard injection timing of the engine to lower emission while meeting smoke criterion and optimizing fuel economy. In the fuel injection

10 camshaft lobe, changes were made to the lobe to ensure that optimum injection pressure was realized. By phasing the camshaft to the correct position, an optimum location favorable from emission and fuel economy standpoint was discovered. Additional changes to the exhaust cam lobe were made to improve lower NO* emission. From the tests it was found that

15 phasing the camshaft as schematically illustrated in Figure 3 provided benefits in reducing NOx emissions. Figure 3 provides a schematic representation of camshaft timing angles according to one embodiment of the present invention. The angular representation of Figure 3 as described below is base on degrees of rotation from top dead center.

20 [0015] The centerline of the injector cam is at 48.5 degrees. The start of the exhaust profile is at 78.5 degrees. The valve open 0.026-inch lift occurs at 110 degrees. The max valve lift occurs at 174.5 degrees. The injection profile ends at 228.5 degrees. The valve close 0.026-inch lift occurs

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at 238.5 degrees. The end of the exhaust profile occurs at 256.5 degrees. The start of the injection profile occurs at 317.5 degrees.

[0016] The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention 5 are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.

Claims (1)

1. A method of phasing a camshaft comprising:

providing the center line of the injector cam at about 48.5 degrees past top dead center;

starting the exhaust profile at about 78.5 degrees past top dead center;

opening the valve at about 110 degrees past top dead center; maximizing the valve lift at about 174.5 degrees past top dead center; ending the injection profile at about 228.5 degrees past top dead center;

closing the valve lift at about 238.5 degrees past top dead center; ending the exhaust profile at about 256.5 degrees past top dead center; and starting the injection profile at about 317.5 degrees past top dead center.