JPH0760404A - Mold for central part in width direction of engine block - Google Patents

Abstract

PURPOSE:To reduce machining of an engine block for internal combustion engine as little as possible and reduce the cost. CONSTITUTION:In an upper mold 27 in a mold for casting the engine block for two-cylinder four cycle internal combustion engine, an upper inner mold 30 for cam chain enclosed chamber which is positioned at the intermediate of an injecting part for holding right and left liners and regulated to the upper part of the inner surface of a tensioner lifter enclosed hole, is integrally formed. In a lower inner mold 28, an lower inner mold 31 for cam chain enclosed chamber which is faced to the upper inner mold 30 for cam chain enclosed chamber in the upper mold 27 and regulated to the lower part of the inner surface of the tensioner lifter enclosed hole is formed. Further, an upper projecting part 32 projected upward from the upper part 22a of an inside opening edge in the tensioner lifter enclosed hole 22 faced to the cam chain enclosed chamber 10 is formed. In a rear outer mold 24, a lower projecting part 33 projected downward from the lower part 22b of an outside opening edge in the tensioner lifter enclosed hole 22 faced to the cam chain enclosed chamber 10 is formed.

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 central portion in the width direction 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 constructed by integrating a cylinder block and an upper crankcase of a multi-cylinder parallel internal combustion engine in which the upper part of the cylinder is inclined forward. A crankshaft 05, a main shaft (not shown) that supports a gear group of the transmission, and a counter shaft are rotatably pivoted on an upper and lower split surface 04 obtained by dividing the crankcase into upper and lower halves by the crankcase 02 and the lower crankcase 03. In the supported internal combustion engine, the chain storage chamber 07 that drives the overhead valve camshaft 06 is formed between adjacent cylinders without being formed on either the left or right side of the engine block 01. On the upper side, there was an engine block 01 in which a storage hole 09 of the tensioner lifter 08 was formed toward the center of the cylinder.

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

[0004]

In the conventional mold shown in FIG. 9, the block wall thickness in the vicinity of the storage hole 09 of the tensioner lifter 08 is thick in order to reliably bear the vibration of the tensioner. In addition, due to the die-cutting, the amount of engine block waste increases, making it easier for porosity to occur.
The cutting amount of 09 was large, the cutting time was long, the material cost was high, and it was difficult to improve the productivity.

[0005]

DISCLOSURE OF THE INVENTION The present invention relates to an improvement of a center mold in the width direction of an engine block that overcomes the above-mentioned problems, and it 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 side surface of the hollow chamber, and a crankshaft centerline oriented in the horizontal direction is provided. An engine block in which a cylinder block and an upper crankcase are integrated along a passing plane, and a lower crankcase divides the crankcase into two parts, and a crankshaft is rotatably sandwiched between the upper and lower split surfaces of the crankcase. A widthwise central part mold for casting an engine block, comprising a protrusion projecting upward from an inner opening edge upper part of the hole facing the hollow chamber and forming an upper surface of the hole. Together, they form the lower inner mold that is vertically drawn downward with respect to the split surface of the crankcase, the upper inner mold that is vertically pulled up along the longitudinal direction of the cylinder, and the upper inclined surface of the engine, and An upper outer die having a protrusion projecting 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 vertically upwardly drawn with respect to a split surface of the crankcase; and a lower inclined surface of the engine and the crank. It is characterized in that it comprises a lower outer mold that is pulled out along the split surface of the case.

Since the present invention is constructed as described above,
Even if the depth of the hole opening to the hollow chamber is increased and the wall thickness of the peripheral wall of the hole is thick, a lower inner die projection partially protruding from the hollow chamber into the hole, and an engine outside A part of the space surrounded by the hole can be filled with the upper outer mold protrusion partly projecting into the hole from one side.

Therefore, according to the present invention, the wall of the cast block casting can be made as thin as possible to suppress the occurrence of porosity, and the amount of molten metal injected into the mold can be reduced to reduce the material cost. Moreover, it is possible to shorten the machining time for forming the holes and greatly improve the productivity.

Further, in the present invention, since a core which must be broken at the time of demolding is not used each time casting is carried out, the treatment before and after casting is simplified, and the cost can be reduced also from this aspect. .

[0009]

EXAMPLE An example of the present invention shown in FIGS. 1 to 7 will be described below. In an overhead valve cam type 2-cylinder 4-cycle internal combustion engine 1 shown in FIG. 1 mounted on a motorcycle (not shown), a vertically divided lower crankcase 2, an upper crankcase and a cylinder block are integrated. The crankshaft 6 is rotatably supported between the engine block 3 and the engine block 3 via a slide bearing, and the cylinder head 4 and the head cover 5 are stacked above the engine block 3 and integrally coupled to each other. The lower crankcase 2, the engine block 3 and the cylinder head 4 are made of die cast aluminum or aluminum alloy.

As shown in FIG. 2, the crankshaft 6 is connected to a piston (not shown) which is reciprocally fitted in a cylinder 7 of the engine block 3 through a connecting rod (not shown). The crankshaft 6 is rotationally driven according to the up and down movement of the piston.

Further, the cylinder head 4 is provided with an intake valve and an exhaust valve (not shown), and a valve operating cam (not shown) is arranged above the intake valve and the exhaust valve, and a cam shaft integrated with the valve operating cam. 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 described later is formed in the center portion in the width direction between the left and right cylinders 7 of the engine block 3, and a drive sprocket 11 is integrated in the center portion of the crankshaft 6. Cam sprocket 12 having a number of teeth twice that of the drive sprocket 11 is integrally fitted to the central portion of the cam shaft 9 to form a drive sprocket 11 and a cam sprocket 12 in the cam chain storage chamber 10. When the endless chain 13 is bridged and the crankshaft 6 makes two revolutions,
The cam sprocket 12 and the valve operating cam are driven to rotate once.

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

Further, 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, the tensioner lifter 20 is disposed at a position higher than the center of the tensioner body 17 and behind it, and the tip of the rod 21 of the tensioner lifter 20 is fitted into the recess 17a of the tensioner body 17. To be,
Tensioner lifter storage hole 22 on the rear wall of engine block 3
The endless chain 13 is provided with a substantially constant tension state by the tensioner lifter 20 that is operated by springs, hydraulic pressure, etc., regardless of the swing of the tensioner main body 17.

Further, as shown in FIG. 7, the mold for casting the engine block 3 is a front outer mold 23 that defines the shape of the front surface of the engine block 3.
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 ( (Refer to FIG. 4 ・ It is viewed from the front so that it is left-right reversed), the right outer mold 26 that defines the shape of the right surface of the engine block 3, and the shape of the top surface of the engine block 3 It comprises an upper mold 27 that holds the cylinder liner 8 and a lower inner mold 28 that defines the lower surface of the engine block 3.

In the upper die 27, however, as shown in FIG. 6, liner holding protrusions 29 are provided so as to hold the cylinder liner 8 and close the bottom surface thereof, and the liner holding protrusions 29 are projected downward to the left and right. 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 die 30 that defines the upper portion of the inner surface of 22 is integrally formed.

Further, in the lower inner mold 28, as shown in FIG. 7, the cam chain storage chamber upper inner mold 30 of the upper mold 27 is shown.
And 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 the cam chain storage chamber 10
An upper protrusion 32 protruding upward from the inner opening edge upper portion 22a of 22
Are formed.

Further, the rear outer mold 24 is provided with a lower projection 33 which projects downward from the outer opening edge lower portion 22b of the tensioner lifter housing hole 22 facing the cam chain housing chamber 10.

Then, the inner mold 30 of the upper part of the cam chain storage chamber of the upper mold 27 and the lower inner mold 31 of the cam chain storage chamber of the lower mold 28.
Is formed so as to be inclined and tilted upward, and further to be in contact with the rear part thereof via the folding split surface 34 whose inclination angle is further increased.

Since the embodiment shown in FIGS. 1 to 7 is constructed as described above, the front outer mold 23 and the rear outer mold are
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 28 are aligned and integrally coupled to each other, the die is set in a die casting device (not shown), and the molten metal is pressure-injected into the mold by operating the die casting device to perform die casting. You can

In the engine block 3 cast in this way, the cam chain storage chamber 10 is formed without any machining work.
In the portion where the tensioner lifter storage hole 22 facing the 10 is provided, the wall thickness of the peripheral wall portion of the tensioner lifter storage hole 22 is indicated by t by the upper projection 32 and the lower projection 33. The thickness T of the peripheral wall of the tensioner lifter housing hole 22 is smaller than the wall thickness T of the tensioner lifter housing hole 22.
Is formed to a thickness that can sufficiently bear the external force such as vibration applied to the cam chain tensioner device 15, so that the molten metal injection amount can be suppressed to the necessary minimum and the material cost can be reduced. Become. Therefore, the machining allowance for cutting the tensioner lifter housing hole 22 is significantly reduced, the machining time is significantly shortened, and the productivity can be greatly improved.

Further, since a core that must be broken each time casting is not required, the pretreatment and posttreatment of casting can be simplified and the cost can be reduced in this respect.

Further, as shown in FIG. 8, if a concave portion 35 is formed in the cam chain storage chamber upper inner die 30 so as to face the cam chain storage chamber 10 adjacent to the upper portion 34a of the folding mold splitting surface 34,
In the cam chain storage chamber 10, it is possible to configure a swing stop that suppresses lateral swing of the tensioner main body 17.

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

[Brief description of drawings]

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

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

3 is a plan view of an engine block of the 2-cylinder 4-cycle internal combustion engine shown in FIG. 1. FIG.

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

5 is a vertical side view cut along the line VV of FIG. 3. FIG.

6 is a vertical sectional side view cut along the line VI-VI in FIG.

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

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]

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 chamber, 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 housing hole, 23 ... Front outer mold, 24 ... Outer rear Mold, 25 ... Left outer mold, 26 ...
Right outer type, 27 ... upper type, 28 ... lower inner type, 29 ... liner holding protrusion, 30 ... cam chain storage chamber upper inner type, 31 ... cam chain storage chamber lower inner type, 32 ... upper protrusion, 33 ... the lower protrusion,
34 ... Bent mold split surface, 35 ... Recessed part.

Claims (3)

[Claims] 1. A multi-cylinder parallel internal combustion engine having cylinders inclined forward and backward, wherein a hollow chamber oriented in the cylinder axis direction is formed between adjacent cylinders, and an 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 with a plane that passes through the centerline of the crankshaft, which has a downwardly sloping hole and is oriented in the horizontal direction, and the lower crankcase move the crankcase up and down. A widthwise central mold for casting an engine block which is divided into two parts and which rotatably clamps a crankshaft on the upper and lower split surfaces of the crankcase, and which is located above the inner opening edge of the hole facing the hollow chamber. A lower inner die that is vertically protruded from the crankcase split surface, and an upper inner die that is upwardly ejected along the longitudinal direction of the cylinder. An upper outer mold for forming an upper inclined surface of the engine, projecting downward from a lower portion of an upper opening edge of the hole to form a lower surface of the hole, and being vertically withdrawn with respect to the split surface of the crankcase; An engine block width direction central mold comprising: a lower outer mold that forms a lower inclined surface of the engine and is pulled outward along the split surface of the crankcase. 2. The engine block width direction central portion according to claim 1, wherein the hollow chamber is a chain storage chamber that drives an overhead valve camshaft, and the hole is a tensioner lifter storage hole. template. 3. The engine block width direction central portion mold according to claim 1, wherein the hollow chamber is a cooling water passage, and the hole is a cooling water communication hole.