JP3226680B2 - Engine block width direction center mold - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mold for casting a widthwise central portion of an engine block of an internal combustion engine mounted on a motorcycle or the like.

[0002]

2. Description of the Related Art As shown in FIG. 9, an engine block 01 is formed by integrating a cylinder block and an upper crankcase of a multi-cylinder parallel-type internal combustion engine in which the upper part of a cylinder is inclined forward. A crankshaft 05, a main shaft (not shown) supporting a gear group of a transmission, and a counter shaft are rotatably pivoted on an upper and lower division surface 04 obtained by dividing the crankcase into upper and lower portions by a crankcase 02 and a lower crankcase 03. In the supporting internal combustion engine, the chain storage chamber 07 for driving the overhead valve camshaft 06 is formed between adjacent cylinders without being formed on one of the left and right sides of the engine block 01. An engine block 01 having an accommodation hole 09 for a tensioner lifter 08 was formed in the upper portion toward the center of the cylinder.

In order to cast such an engine block 01, conventionally, a mold as shown in FIG. 9 has been used. That is, the upper inner mold 010, the lower inner mold 011, the outer mold 012, and the rear outer mold 013 constitute a mold.

[0004]

In the conventional mold shown in FIG. 9, the thickness of the block wall near the storage hole 09 of the tensioner lifter 08 is increased in order to reliably bear the tensioner vibration. In addition, due to the removal of the mold, the waste of the engine block increases, so that cavities tend to occur,
In 09, the amount of cutting was increased, the cutting time was increased, the material cost was increased, and it was difficult to improve the productivity.

[0005]

SUMMARY OF THE INVENTION The present invention relates to an improvement in a center mold in the width direction of an engine block, which overcomes such difficulties, and relates to a multi-cylinder parallel-type internal combustion engine in which cylinders are inclined forward and backward. A hollow chamber oriented in the cylinder axis direction is formed between the cylinders, and a hole inclined obliquely downward toward the center of the cylinder is provided on the upper surface of the hollow chamber, and a crankshaft centerline oriented horizontally in the left-right direction is provided. The crankcase is divided into two parts vertically by the engine block integrating the cylinder block and the upper crankcase along the plane that passes through, and the lower crankcase is divided into two parts, and the crankshaft is rotatably held between the upper and lower divided surfaces of the crankcase. A central mold in the width direction for casting an engine block to be formed, comprising a projection projecting upward from an upper portion of an inner opening edge of a hole facing the hollow chamber and forming an upper surface of the hole. Both form a lower inner die that is pulled vertically downward with respect to the crankcase split surface, an upper inner die that is drawn upward along the longitudinal direction of the cylinder, and an upper inclined surface of the engine, and An upper outer die having a projection protruding downward from a lower portion of an upper opening edge to form a lower surface of a hole, and an upper outer die that is pulled out vertically upward with respect to the crankcase split surface; It is characterized by comprising a lower outer mold that is pulled out along the case split surface.

Since the present invention is configured as described above,
Even if the depth of the hole opening into the hollow chamber is increased and the wall thickness of the peripheral wall of the hole is large, a lower inner projection that partially projects into the hole from the hollow chamber, A part of the space enclosed by the hole can be filled with the upper outer projection projecting partly into the hole from the side.

For this reason, according to the present invention, the wall of the cast block casting can be made as thin as possible to suppress the occurrence of cavities, and the amount of molten metal injected into the mold is reduced to reduce material costs. In addition, the cutting time for forming the holes can be reduced, and the productivity can be greatly improved.

Further, in the present invention, a core which must be destroyed at the time of demolding is not used every time casting is performed, so that processing before and after casting is simplified, and the cost can be reduced in this respect as well. .

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention shown in FIGS. 1 to 7 will be described below. In the overhead-valve cam type two-cylinder four-cycle internal combustion engine 1 shown in FIG. 1 mounted on a motorcycle (not shown), the lower crankcase 2, which is divided into upper and lower parts, and the upper crankcase and the cylinder block are integrated. The crankshaft 6 is rotatably supported via a sliding bearing between the engine block 3 and the cylinder block 4 and the head cover 5 are superimposed on the engine block 3 and integrally connected to each other. These lower crankcase 2, engine block 3 and cylinder head 4 are made of aluminum or aluminum alloy cast by die casting.

As shown in FIG. 2, the crankshaft 6 is connected via a connecting rod (not shown) to a piston (not shown) fitted reciprocally up and down on a cylinder 7 of the engine block 3. The crankshaft 6 is driven to rotate in accordance with the elevation of the piston.

Further, an intake valve and an exhaust valve (not shown) are provided on the cylinder head 4, and a valve operating cam (not shown) is arranged above the extension of the intake valve and the exhaust valve, and a camshaft integrated with the valve operating cam is provided. Reference numeral 9 is rotatably held between the cylinder head 4 and a cam holder (not shown).

Further, a cam chain storage chamber 10 for storing an endless chain 13, which will be described later, is formed at the center in the width direction between the left and right cylinders 7 of the engine block 3, and a drive sprocket 11 is integrally formed at the center of the crankshaft 6. A cam sprocket 12 having twice the number of teeth of the drive sprocket 11 is integrally fitted to the center of the camshaft 9, and the cam sprocket 11 and the cam sprocket 12 are fitted in the cam chain storage chamber 10. When the endless chain 13 is bridged and the crankshaft 6 rotates twice,
The cam sprocket 12 and the valve cam are driven one rotation.

Further, a chain guide is provided in front of the cam chain storage chamber 10 on the vehicle body side (the left exhaust port side in FIG. 1).
A cam chain tensioner device 15 is provided on the rear side of the cam chain storage chamber 10 (on the intake port side), and a chain guide 16 is also provided above the cam sprocket 12. ing.

In the cam chain tensioner device 15,
A pin 19 is integrally fitted to a mounting base 18 of the tensioner body 17, and the pin 19 is swingably held between the lower crankcase 2 and the engine block 3.

Further, a tensioner lifter 20 is disposed at a position slightly above or above the center of the tensioner main body 17, and the tip of a rod 21 of the tensioner lifter 20 is fitted into a concave portion 17a of the tensioner main body 17. To be,
Tensioner lifter storage hole 22 in rear wall of engine block 3
The endless chain 13 is provided with a substantially constant tension state by a tensioner lifter 20 operated by a spring, a hydraulic pressure, or the like irrespective of the swing of the tensioner main body 17.

Further, as shown in FIG. 7, a mold for casting the engine block 3 is a front outer mold 23 for defining the shape of the front surface of the engine block 3.
And a rear outer mold 24 that defines the shape of the rear surface of the engine block 3 on the side where the cam chain tensioner device 15 is provided, and a left outer mold 25 that defines the shape of the left surface of the engine block 3 ( The right and left outer molds 26 that define the shape of the right surface of the engine block 3 and the shape of the top surface of the engine block 3 are defined; An upper mold 27 for holding the cylinder liner 8 and a lower inner mold 28 for defining the lower surface of the engine block 3 are provided.

In the upper mold 27, as shown in FIG. 6, a liner holding projection 29 is provided so as to hold the cylinder liner 8 and cover the bottom surface thereof, and to project right and left downward. As shown in the figure, the tensioner lifter storage hole is located in the middle of the left and right liner holding protrusions 29.
A cam chain storage chamber upper inner mold 30 that defines an upper portion of the inner surface of 22 is integrally formed.

In the lower inner mold 28, as shown in FIG.
, A cam chain storage chamber lower inner mold 31 that defines a lower portion of the inner surface of the tensioner lifter storage hole 22 is formed,
Tensioner lifter storage hole facing cam chain storage room 10
An upper protruding portion 32 that protrudes upward from the inner opening edge upper portion 22a of the 22
Are formed.

Further, in the rear outer mold 24, a lower protruding portion 33 is formed which protrudes downward from a lower portion 22b of an outer opening edge of the tensioner lifter housing hole 22 facing the cam chain housing chamber 10.

The upper inner die 30 of the cam chain storage chamber of the upper die 27 and the lower inner die 31 of the cam chain storage room of the lower inner die 28
Is formed so as to be inclined upward after being inclined, and to be in contact with the rear part via a bent-type split surface 34 whose inclination angle is further increased.

The embodiment shown in FIGS. 1 to 7 is constructed as described above, so that the front outer mold 23 and the rear outer mold 23 are used.
24, left outer mold 25, right outer mold 26, upper mold 27 and lower inner mold
In a state in which the mating surfaces of the 28 are joined together and integrally connected to each other, it is set in a die casting device (not shown), and by operating the die casting device, the molten metal is injected under pressure into the mold to perform die casting. Can be.

In the engine block 3 thus cast, the cam chain storage chamber 10 is formed without any need for any machining.
At the portion where the tensioner lifter storage hole 22 facing the surface 10 is provided, the thickness of the portion by the upper protrusion 32 and the lower protrusion 33 is indicated by t, so that the thickness of the peripheral wall of the tensioner lifter storage hole 22 is increased. The thickness T of the peripheral wall of the tensioner lifter housing hole 22
Is formed to a thickness that can sufficiently bear external forces such as vibrations applied to the cam chain tensioner device 15, so that the amount of molten metal injected can be suppressed to a minimum and material costs can be reduced. Become. For this reason, the machining allowance for cutting the tensioner lifter housing hole 22 is significantly reduced, and the machining time is significantly shortened, so that productivity can be greatly improved.

Further, since a core which must be broken every time casting is not required, pre-casting and post-casting can be simplified, and the cost can be reduced in this aspect.

Further, as shown in FIG. 8, if a concave portion 35 is formed in the upper inner die 30 of the cam chain storage chamber adjacent to the upper part 34a of the bent mold splitting surface 34 and facing the cam chain storage chamber 10,
The cam chain storage chamber 10 can be provided with a vibration damper that suppresses the lateral vibration of the tensioner main body 17.

The position of the concave portion 35 can also be changed by changing the shape of the bending parting surface 34 as shown by a broken line.

[Brief description of the drawings]

FIG. 1 is an overall side view of a two-cylinder four-stroke internal combustion engine manufactured using a width direction center mold for an engine block of the present invention.

FIG. 2 is a vertical sectional side view of a main part of FIG.

FIG. 3 is a plan view of an engine block of the two-cylinder four-stroke internal combustion engine shown in FIG.

FIG. 4 is a front view of an engine block.

FIG. 5 is a vertical sectional side view taken along line VV of FIG. 3;

FIG. 6 is a vertical sectional side view taken along the line VI-VI of FIG. 6;

FIG. 7 is an enlarged vertical sectional side view of the mold cut along the line VI-VI in FIG. 3;

FIG. 8 is an enlarged vertical sectional side view of a main part of another embodiment.

FIG. 9 is a vertical sectional side view of a conventional engine block mold.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... 2 cylinder 4 cycle internal combustion engine, 2 ... Lower crankcase, 3 ... Engine block, 4 ... Cylinder head, 5 ...
Head cover, 6 ... Crank shaft, 7 ... Cylinder, 8 ... Cylinder liner, 9 ... Cam shaft, 10 ... Cam chain storage room, 11 ... Drive sprocket, 12 ... Cam sprocket, 13 ... Endless chain, 14 ... Chain guide, 15 ... Cam chain tensioner device, 16… Chain guide, 17… Tensioner body, 18… Mounting base, 19… Pin, 20… Tensioner lifter, 21… Rod, 22… Tensioner lifter storage hole, 23… Front outside type, 24… Back outside Type, 25 ... left outer type, 26 ...
Right outer type, 27 ... Upper type, 28 ... Lower inner type, 29 ... Liner holding protrusion, 30 ... Cam chain storage room upper inner type, 31 ... Cam chain storage room lower inner type, 32 ... Upper protrusion, 33 ... downward projection,
34… Bent type split surface, 35… Recess.

Continuation of the front page (56) References JP-A-4-295165 (JP, A) JP-A-2-137644 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B22C 9 / 24 B22C 9/22

Claims (3)

(57) [Claims] In a multi-cylinder parallel-type internal combustion engine in which cylinders are inclined forward and backward, a hollow chamber is formed between adjacent cylinders, the hollow chamber being oriented in the cylinder axis direction, and the upper surface of the hollow chamber is inclined toward the center of the cylinder. An engine block that integrates a cylinder block and an upper crankcase along a plane that passes through the centerline of the crankshaft that is oriented horizontally in the horizontal direction is provided with a hole that is inclined downward, and the crankcase is vertically moved by the lower crankcase. A width direction center mold for casting an engine block for rotatably holding a crankshaft on upper and lower divided surfaces of the crankcase, wherein the upper surface is located above an upper part of an inner opening edge of a hole facing the hollow chamber. A lower inner die that is drawn vertically downward with respect to the crankcase split surface, and an upper inner die that is drawn upward along the longitudinal direction of the cylinder. An upper outer mold that forms an upper inclined surface of the engine, includes a protrusion that projects downward from a lower portion of an upper opening edge of the hole to form a lower surface of the hole, and is pulled out vertically upward with respect to the crankcase split surface. A central mold in a width direction of an engine block, comprising a lower outer mold that forms a lower inclined surface of the engine and is drawn outward along the split surface of the crankcase. 2. The central portion in the width direction of the engine block according to claim 1, wherein the hollow chamber is a chain storage chamber for driving an overhead valve operating cam shaft, and the hole is a tensioner lifter storage hole. template. 3. The center mold in the width direction of the engine block according to claim 1, wherein the hollow chamber is a cooling water passage, and the hole is a cooling water communication hole.