JPS60217009A - Piston head forming for direct injection 4 valves type diesel engine - Google Patents

Abstract

PURPOSE:To reduce ineffective space and obtain high compression ratio in an engine, by moving the rotary shaft of a milling cutter parallel to a piston pin in the creation method of the piston head of a direct injection 4 valves type Diesel engine. CONSTITUTION:A milling cutter 61, which is used for accomplishing the creation of a piston head, is made to have an outward form with a small diameter cylindrical surface 63 at its central part and almost conical surfaces 62, having gradual increasing diameters foward its both ends, on both sides. And, for machining the piston head, the rotary shaft of the milling cutter 61 is moved along the line which makes a right angle with the piston pin 51, namely along the X-line, keeping the rotary shaft parallel to the pin 51, then, the piston head which conforms to a given design is formed. Furthermore, as for the cutting depth of the cutter 61, the maximum depth is located at the right sideline of the piston head and the depth is gradually reduced by shifting the cutter 61 to upper right direction. By this method, it becomes possible to reduce ineffective space and obtain high compression ratio in an engine.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] The present invention relates to a method for creating a piston crown surface of a direct injection four-valve diesel II cabinet mainly used in a vehicle.

In a direct injection diesel engine, in which each cylinder has one intake and exhaust valve, the amount of intake air is insufficient at high speeds, resulting in a limit to output.

Gasoline engines with two intake and exhaust valves per cylinder are already common, but diesel engines require a higher compression ratio than gasoline engines, especially small direct injection diesel engines that have multiple intake and exhaust valves. Placing separate intake and exhaust valves in the cylinder head poses the following problems.

Because it is difficult to keep the wasted volume of the combustion chamber small in small direct-injection four-valve diesel engines, the intake and exhaust valves are generally arranged vertically, that is, parallel to the cylinder center axis, and the lower surface of the cylinder head and the piston crown are arranged vertically. Generally, the surface is approximately flat. However, in small engines with small cylinder inner diameters, it is difficult to secure space for arranging fuel injection nozzles, glow plugs, etc. in the center, so the intake and exhaust valves must be arranged in a square shape.

However, in the case of direct-injection diesel engines that require a high compression ratio, it is necessary to minimize the gap volume between the lower surface of the cylinder head and the crown surface of the piston, while in the case of small engines, the displacement There is a limit to how small the dimensions of the valve train mechanism can be made in accordance with the above. In addition, in order to arrange the intake and exhaust valves in a slanted shape with an included angle of 40 to 50 degrees like a gasoline engine due to the compression ratio, the cylinder head is formed by die-casting like a conventional gasoline engine. If the combustion chamber is structured so that the bottom surface is spherically concave and the piston crown surface protrudes spherically, not only is the wasted volume too large, but molding with die casting cannot achieve sufficient precision, which affects the compression ratio. This causes variations in engine output.

In view of the above-mentioned problems, an object of the present invention is to provide a piston crown for a direct injection type four-valve diesel engine that can reduce waste volume and obtain a high compression ratio in a four-valve diesel engine that adopts a V-shaped arrangement. The objective is to provide a method for creating surfaces.

[Structure of the Invention] For this reason, the first invention is such that the milling cutter has a cylindrical surface at the center and a gradually larger diameter at both ends. It is characterized by moving the rotation axis of the cutter parallel to the piston pin.

The second invention is a milling cutter equipped with a conical surface having a minimum outside diameter at the center and gradually increasing the outside diameter toward both ends. The rotary shaft of the milling cutter is moved in parallel in a direction perpendicular to the piston pin so as to increase the size of the milling cutter.

The present invention will be explained based on examples. As shown in FIG. 1, the direct injection four-valve diesel engine according to the present invention includes a cylinder block 22, a piston 30 fitted into the cylinder block 22, and a piston 30 that is connected to the top end of the cylinder block 22 via a known gasket. The cylinder head 2 includes a cylinder head 2, a valve train supported by the cylinder head 2, and a housing 37 for supporting the valve train. The upper end of the housing 37 is closed by a head cover 38.

The cylinder block 22 has a hollow water chamber 29 formed in its wall, which is connected to the water chamber 9 of the cylinder head 2 via a passage 19. The piston 30 is in the cylinder block 2
The piston pin 51 is fitted into the cylinder 17 of No. 2.
The connecting rods 31 are connected with each other. The base end of the connecting rod 31 is connected to a crank arm of a crankshaft (not shown) with a pin.

The crown surface of the piston 30 is sloped in a roof shape so that the cross-sectional shape when viewed from the direction of the crankshaft or piston pin is highest at the center and lower at both sides.

Then, a recess is provided in the crown surface of the piston 30 to form a combustion chamber 27.
is formed.

°The cylinder head 2 has an intake boat 3 on the left side that is opened and closed by a pair of intake valves 13 arranged in parallel in the crankshaft direction.
Exhaust boats 5 that are opened and closed by a pair of exhaust valves 15 arranged in parallel in the crankshaft direction are formed on the right side. The lower surface of the cylinder head 2 is also shaped like a roof, with the center being most concave in correspondence with the crown surface of the piston 30, and the outer surface becoming shallower, and this slope is set to about 7 to 15'.

An intake valve 13 that opens and closes in a direction perpendicular to the inclined lower surface of the cylinder head 2 is supported by a wall of the cylinder head 2 with a cylindrical guide 43. A tappet 41 is attached to the upper end of the intake valve 13 by a known retainer 39a.
A valve spring 39 is interposed between the retainer 39a and the wall of the cylinder head 2, and the force of the valve spring 39 presses the tappet 41 against the cam 34 of the camshaft 33, and the tappet 41 is pressed against the lower end of the cylinder head 2. The formed valve body is pressed against a valve seat 13a formed on the intake boat 13. Preferably, as shown in FIG. 2, one of the pair of intake boats 13 arranged in the crankshaft direction has an edge h.
One boat is combined with the other boat as a tangential boat, and the intake air swirl in the combustion chamber 27 is effectively formed.

As shown in FIG. 1, similarly, the stem of the exhaust valve 15 arranged on the right side of the cylinder head 2 is slidably supported on the wall of the cylinder head 2 via a guide 44. A tappet 42 is connected to the upper end by a retainer 40a, and a valve spring 40 is interposed between the retainer 408 and the wall of the cylinder head 2. The valve spring 40 presses the tappet 42 against the cam 36 of the camshaft 35, and also presses the valve element formed at the lower end of the stem against the valve seat 15a of the exhaust boat 5.

The intake port 3 opens on the left side wall of the cylinder head 2, and is connected to the intake manifold 23 with a bolt (not shown). The exhaust boat 15 opens onto the right side wall of the cylinder head 2, and is connected to the exhaust manifold 25 with bolts here.

Each camshaft 33, 35 is supported at the upper end of the housing 37 with a bearing (not shown). This bearing is clamped by a bearing cap (not shown) whose lower half is connected to the upper end wall of the housing 37 and whose upper half is connected to the housing 37.

As shown in Fig. 2, a pair of intake valves 1 are arranged in the direction of the crankshaft.
3 and a pair of exhaust valves 15 are arranged, and a fuel injection nozzle 8 and a glow plug 56 are arranged at the center of the cylinder.

As shown in FIG. 3, the intake valve 13 and the exhaust valve 15 are each arranged so that their stems are inclined in a V-shape. For this reason, the piston crown surface forms a roof-shaped wall surface that is highest at approximately the center and gradually becomes lower on both sides. In other words,
A flat inclined surface 7 facing the intake valve 13 and the exhaust valve 15
1.72 is defined in FIG. 2 by a line 71a on the intake valve side and a line 72a on the exhaust valve side with the center line y parallel to the piston pin 51 (FIG. 1) as the boundary.

However, when viewed from the side, as shown in FIG. 4, the stems of each pair of intake valves and exhaust valves 15 are arranged parallel to each other (in a direction perpendicular to the axis of the camshaft). Therefore, as shown in FIG. 4, the shape of the piston crown surface is not spherical but an inclined flat surface, and both ends thereof become gradually lower as shown by curved surfaces 62a and 62b.

The first method of creating a piston crown surface according to the invention is achieved by a milling cutter 61 shown in FIG. The outer shape of this milling cutter 61 is a cylindrical surface 63 with a small diameter at the center, and approximately conical surfaces 62 with gradually larger outer diameters at both ends. When machining the piston crown surface, the rotation axis of the milling cutter 61 is kept parallel to the piston pin 51 (Fig. 1) and moved in a direction perpendicular to the piston pin, that is, in the direction of the line X. It forms the

In this case, as shown in FIG. 6, the depth of cut S of the milling cutter 61 is maximized at the right edge of the piston crown surface, and the depth of cut S is gradually decreased by moving the milling cutter 61 toward the upper right. , the depth of cut S is gradually increased from the ridge line y that crosses approximately the center of the piston crown surface.

By creating the piston in this manner, a flat surface is formed in which both sides of the ridge line y, which crosses approximately the center of the piston crown surface, slope downward. Then, the conical surface 62 of the milling cutter 61 creates a curved surface 62a and a curved surface 6 at both ends of the ridge line y, respectively.
2b is formed.

As a result, the peripheral edge 69 (FIG. 4) of the piston crown surface overlaps a plane perpendicular to the central axis of the piston crown surface.

Next, a method of creating a second piston crown surface according to the present invention is accomplished by a milling cutter 65 shown in FIG. This milling cutter 65 has a cylindrical surface with a large diameter on both ends.
8, 68a, and is provided with a conical surface 66, 66a whose outer diameter gradually decreases from both ends to the center portion 67. When processing the piston crown surface, the rotation axis of the milling cutter 65 is kept parallel to the line X perpendicular to the piston pin and moved in the direction of the ridge line y. In this case milling cutter 65
As shown in FIG. 8, the depth of cut It is the maximum depth of cut t @ at the edge 62b of the piston crown surface, and the depth of cut t is gradually decreased while feeding along the ridge line y, and the depth of cut t is decreased at the center part. is kept constant, and the depth of cut is gradually increased again at the edge 62a. In this way, the intake valve 13
an inclined surface 71 facing the exhaust valve 15; and an inclined surface 7 facing the exhaust valve 15;
2 is formed into a roof shape with the ridge line y as the boundary.

[Effects of the Invention] As described above, the present invention provides that the piston crown surface of a direct injection four-valve diesel engine is sloped in a roof shape on both sides of the ridge line that crosses approximately the center of the piston, and that the valves on both ends of the ridge line are sloped. Since the wall surface that does not interfere with the seat is gently cut into a spherical shape, by creating a similar shape for the downward direction of the cylinder head, a combustion chamber with less wasted volume can be obtained, achieving the high compression ratio required for a diesel engine. can be obtained. Therefore, it is possible to obtain a direct injection diesel engine that not only has excellent performance at high speeds, but also has improved emissions, produces less smoke, and has excellent startability. Since the piston crown surface is machined using a rotating blade such as a milling cutter, it is easy to process, and a highly accurate shape that fits the valve seats of multiple intake and exhaust valves arranged in a ■ shape can be obtained. This makes it possible to eliminate variations in engine output.

[Brief explanation of the drawing]

Fig. 1 is a front sectional view of a direct injection 4-valve diesel engine to which the present invention is applied, Fig. 2 is a plan view showing the relationship between the piston crown surface and the intake and exhaust valves, and Fig. 3 is a front view of the same. 4 is a side view of the same, and FIG. 5 is a plan view of a milling cutter for achieving the method of creating a piston crown surface of a direct injection 4-valve diesel engine according to the first embodiment of the present invention. FIG. 6 is a diagram illustrating the feeding operation of the milling cutter, and FIG. 7 is a diagram illustrating a method for creating a piston crown surface of a direct injection 4-valve diesel engine according to a second embodiment of the present invention. FIG. 8, a front view of the milling cutter, is a miniature diagram illustrating the feeding operation of the milling cutter. 2 cylinder head 8: Fuel injection nozzle 13: Intake valve 15: Exhaust valve 51: Piston bin 61.65:
Cutter 62, 66.66a: Conical surface 62a, 62b
: Curved surface 63.68.68a : Cylindrical surface 71.7
2: Sloped surface Fig. 2 c

Claims (2)

[Claims] (1) The rotation axis of the milling cutter is moved parallel to the piston pin so that the depth of cut of the milling cutter, which has a cylindrical surface at the center and gradually increases in diameter at both ends, is minimum at the center and gradually increases at both ends. A method for creating a lower surface of a cylinder head of a direct injection type four-valve diesel engine, characterized by: (2) The depth of cut of a milling cutter equipped with a conical surface where the outside diameter is minimum at the center and gradually increases toward both ends is the minimum at the center of the piston crown surface and gradually increases toward both ends. A method for creating a lower surface of a cylinder head of a direct injection type four-valve diesel engine, characterized in that the rotation axis of the milling cutter is moved in parallel in a direction perpendicular to the piston pin.