JP2006312899A - Block dividing structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a block dividing structure for dividing a cylinder block and collecting strength requiring components while minimizing high quality components as required and giving less distortion to cylinder portions when assembled. <P>SOLUTION: In the block dividing structure for an engine having a bore part 10, a crank case part 13a, and a crank cap 17, a crank cap bolt 18b is fastened to a first female screw portion 21b of a thrust member 21 and the crank cap 17 is thus fitted to the crank case part 13a across the bore part 10. The thrust member 21 thrusts the bore part 10, and a cylinder head bolt 18a is fastened to a second female screw portion 21a of the thrust member 21, and a cylinder head 16 is thus fitted thereto. When the bore part 10 is fitted to the crank case part 13a, an outer wall part 13b encircling the bore part 10 is integrally formed on the crank case part 13a. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a structure in which a cylinder block of an engine is divided into two parts to separate a part particularly requiring strength and a part not particularly demanding strength.

Inside the cylinder block of the engine, during operation, after the compressed air / gasoline mixture is compressed by the piston, it is ignited and burned to generate high-temperature and high-pressure gas, which moves the piston sliding up and down. Power is generated by performing a cycle of changing.
Therefore, during engine operation, heat and pressure are always applied as loads to the inner wall of the piston. When the engine is actually operating, the temperature of the combustion gas reaches 2000 ° C. or more and is exposed to explosion pressure, so that it needs to have enough strength to withstand the severe conditions.
Furthermore, the cylinder block of the engine itself needs a certain cylinder diameter to secure the output of the engine, and the number of cylinders is a light car or a standard car of 1000 cc to 1500 cc class for light cars and 1000 cc or less in general. 4 cylinders, other than 6 cylinders and 8 cylinders, to the 12 cylinder class, multiple cylinders are required, the structure is complicated, and as the number of cylinders increases, Become. Naturally, material costs commensurate with the size are required, and the processing cost is also high because of the huge unit.

In recent years, environmental problems have been dealt with largely, and the amount of carbon dioxide and nitrogen compounds emitted by burning fossil fuels has become a problem. Therefore, a high-performance and fuel-efficient engine is demanded, and it is necessary to be an engine that is lightweight and has little friction loss.
In recent years, in order to reduce the weight of the engine as a part of improving the performance of cars, there are many cases of adopting aluminum as the material of the engine. Even in such a case, each cylinder manufacturer can assemble an iron cylinder liner to the cylinder block, or use a high-strength aluminum alloy casting for the sleeve itself and add silicon to the material to deposit it. However, the present situation is that it is an expensive part by repeating trial and error.
Even when a cast iron engine is used with emphasis on the strength of the engine, the output of the engine itself is increasing, and the inner surface of the cylinder is plated or coated with iron metal atoms sprayed. There is no change in being an expensive part.

  Also, in terms of reducing friction loss, in order to improve the roundness and surface roughness of the cylinder and piston, the processing accuracy is improved, the inner surface of the cylinder is plated, an aluminum material, etc. Techniques such as increasing the slidability by adding and precipitating silicon are used, and in order to perform these processes, the processability of the engine block becomes a problem. Although the engine itself has a complicated shape, an engine block that requires precision machining is preferably as small as possible and has no unevenness in terms of the above machining. In addition, the engine block may be distorted due to external factors such as assembly, so it is necessary to consider such a point.

Conventionally, the engine as shown in FIG. 8 disclosed in Patent Document 1 has been mainstream.
In Patent Literature 1, a block 110 in which a cylinder portion 111, a head portion 112, and a crankcase portion 113 are integrally formed is provided, and a bulkhead having a main bearing portion that supports a crankshaft by attaching a bearing cap 114 is referred to as the crankcase. The bulkhead is fixed to the block body with a fastening bolt.
As described above, the periphery of the cylinder block is integrated as much as possible to achieve rigidity, sealability, and weight reduction, and the workability is improved by dividing the bearing portion around the bearing that requires machining.
However, since it is necessary to improve the machining accuracy of the inner cylindrical surface of the cylinder portion along with the improvement of the engine output, the subsequent engines are disclosed in Patent Document 2 and Patent Document 3. Therefore, the number of shapes considering the ease of processing the cylinder inner cylinder has increased.

Patent Document 2 discloses an engine as shown in FIG. In the method of Patent Document 2, 121 is an upper main body including a cylinder head part 121a, 122 is a lower main body including a cylinder skirt part 122a, and both are integrated with the bore side dividing surface 123 and the outer wall side dividing surface 124 together. Has been. This makes it possible to increase the size of the upper body including the cylinder head and increase the rigidity, to reduce the size of the water jacket core and simplify the set, and to improve the castability. is doing.
FIG. 10 shows an engine disclosed in Patent Document 3. In the method of Patent Document 3, a cylinder part 132 is provided integrally and continuously with a water jacket part 134 of a cylinder head part 133 to form an upper body, and a crankcase 138, a water jacket outer wall 139, and a skirt guide cylindrical part 140. Are integrally formed with a lower main body 137. By using a two-body structure in this way, both ease of manufacture and assembly and performance are achieved.

As described above, in order to achieve both downsizing and rigidity, many methods such as casting the cylinder block integrally with the cylinder head and assembling it with the crankcase part have been adopted. Along with the improvement, further rigidity has been required. Therefore, a technique as disclosed in Patent Document 4 has been adopted.
FIG. 11 shows a method disclosed in Patent Document 4. The cylinder block 150 is used in a water-cooled four-cylinder engine and is divided into a cylinder part 151 and a crankcase part 152. The cylinder portion 151 is formed by extrusion or forging, and a water jacket 155, a stat bolt mounting hole 156, an oil drain passage 157, and the like are formed around the cylinder 154.

By extruding or forming the cylinder part 151 by forging, the yield is good and stable quality is secured, and the cylinder part 151 becomes a box shape with a compact shape, which is suitable for mass production and leads to low cost. In addition, local deformation can be avoided by keeping the entire cylinder portion 151 in a certain shape. Furthermore, since a highly accurate material can be created, the processing cost can be minimized.
In addition, the inner peripheral surface of the cylinder 154 of the cylinder portion 151 is plated. For this plating, for example, nickel or iron-based plating is performed, and there is no nest generated during casting on the cylinder inner peripheral surface of the cylinder portion 151, so that a high yield and stable quality plating cylinder can be secured. Further, since the cylinder portion 151 has a simple and compact box shape, handling in the plating process and sealing of the plating solution are easy, and the plating equipment becomes small. Moreover, you may perform the process which sprays and coats an iron-type metal atom on the internal peripheral surface of the cylinder 154 of the cylinder part 151. FIG.
Japanese Utility Model Publication No. 62-69045 Japanese Utility Model Publication No. 63-79453 JP-A 63-106350 JP-A-9-303197

However, in the method of Patent Document 4, since the entire cylinder block part is manufactured by extrusion molding or forging, the part of the outer wall that is originally unnecessary is also made of a highly rigid material, resulting in excessive quality.
Basically, the inner cylinder portion of the cylinder is required to be rigid in order to be exposed to high temperature and pressure, but the outer wall portion and the portion constituting the water jacket need not be so strong.
In the future, it will be required to reduce the cost of parts as well as to further increase the rigidity of the cylinder inner cylinder portion. Therefore, it is necessary to reduce the cost by minimizing the number of high-quality parts and configuring them.

Therefore, the applicant filed in Japanese Patent Application No. 2005-112155 for a block division structure in which the bore portion on which the piston slides and the outer wall formed outside the bore portion are divided, and the outer wall is integrated with the crankcase. did.
FIG. 12 shows a perspective view of the partially assembled state.
The crankcase portion 13a and the outer wall portion 13b are integrally formed to form the crankcase 13, and the bore portion 10 has a mounting portion 10a provided with a first female screw portion and a second female screw portion in contact with the crankcase portion 13a. It is provided on the side and assembled to the crankcase 13.
A space surrounded by the crankcase portion 13a, the outer wall portion 13b, the bore portion 10 and a crank cap (not shown) is defined as a space through which the coolant flows.
With this configuration, three problems in a general engine block division structure are solved.

(1) The first problem is that the engine block tends to become excessive quality when high performance is demanded. For this problem, the bore part that requires strength and the strength that is inherently required are not much. The outer wall is separated, and the outer wall is integrated with the crankcase that does not require much strength, making it possible to select the optimum material, reducing costs and ensuring the required quality for the cylinder. Is possible.

(2) The second problem is that in a general engine, a piston slides on the inner surface of a cylinder at a high speed, and sliding between the piston and the inner surface of the cylinder generates a considerable sliding resistance. In addition to the explosion, frictional heat is also generated by this sliding. Therefore, during operation of the engine, engine oil is constantly sprayed in order to reduce heat and sliding resistance and prevent seizure by reducing the heat generated by the explosion of the fuel, so as to lubricate the piston and prevent seizure.
For this reason, usually, multiple piston rings are fitted on the outer periphery of the piston, scraping off the engine oil sprayed on the inner wall surface of the cylinder, creating the minimum required oil film, and at the same time, excess oil enters the combustion chamber To prevent it.
The piston ring that fits into the piston is spring-like and fulfills its function by stretching against the inner surface of the cylinder, but when using a circular piston, if the shape accuracy of the inner surface of the cylinder is low, sliding resistance is reduced. In addition to the increase, the gap between the piston ring and the inner wall of the cylinder is larger than allowed, which increases the penetration of excess oil into the combustion chamber. As a result, it may cause various problems such as a decrease in engine output, deterioration in fuel consumption, and oil consumption.
The sliding resistance between the piston ring and the inner surface of the cylinder is said to be about 1/3 of the sliding resistance generated during engine operation, and it is extremely important to reduce the influence of strain on the inner surface of the cylinder.

On the other hand, when the engine is assembled, it is necessary to tighten the bolt by applying a torque of about several tens of kN in order to improve the sealing performance on the assembly surface, and the distortion generated by tightening the bolt gives shape accuracy. The effect is large, and when tightened in the vicinity of the piston sliding surface, the roundness of the inner surface of the cylinder is distorted due to strain, and a gap is likely to occur between the piston ring fitted into the piston and the inner surface of the cylinder. It is.
About this subject, by providing the attachment part 10a which provided the 1st internal thread part and the 2nd internal thread part in the bore part 10 in the side which contact | connects the crankcase part 13a, ie, the sliding part of the piston in a bore part By providing the mounting portion 10a at the most distant position, the effect of distortion on the piston sliding portion of the bore portion 10 is minimized, and problems such as engine output reduction, fuel consumption deterioration, and excessive oil consumption Is prevented.

(3) The third problem is that the combustion gas temperature in the combustion chamber formed by the piston, the bore portion 10 and the cylinder head is higher than 2000 ° C. and far exceeds the melting point of the material. The part needs to be cooled, and when the cooling efficiency is lowered, there is a problem that the influence of the above-described distortion or the like is increased due to the deformation due to heat, or the worst engine is destroyed.
About this subject, the cooling performance of an engine is ensured by making the space between the bore part 10 and the outer wall part 13b into a water channel.

As described above, the present applicant has disclosed an invention for solving three problems in Japanese Patent Application No. 2005-112155.
However, in the second problem described above, the mounting portion 10a is provided at the bore portion 10 on the crankcase portion 13a side so that it can be assembled even if consideration is given to suppress the influence of stress generated during assembly. At this time, the mounting portion 10a is tightened with a fastening bolt and pulled upward or downward, and depending on the assembly method, distortion occurs in the bore portion 10 and the shape accuracy required when the piston slides deteriorates. was there.
As described above, this is because the piston ring fitted into the piston sliding in the bore portion 10 scrapes off the engine oil sprayed on the inner wall surface of the cylinder to form the minimum required oil film, and at the same time, The oil prevents the oil from entering the combustion chamber. However, if the roundness of the inner surface of the cylinder is low, the sliding resistance of the piston ring is increased and a clearance between the piston ring and the inner wall of the cylinder is allowed. Will increase the penetration of excess oil into the combustion chamber. As a result, it may cause various problems such as a decrease in engine output, deterioration in fuel consumption, and oil consumption.

  Therefore, the present invention has been made in order to solve the above-described problems, and by dividing the portion where the strength of the cylinder block is necessary and the portion where the strength is not necessary, and consolidating the parts where the strength is necessary, The object is to provide a block division structure in which high quality parts are kept to a minimum and the cylinder portion is less distorted when assembled.

In order to achieve the above object, the present invention has the following features.
(1) In an engine block division structure including a bore portion in which a piston slides, a crankcase portion that holds a crankshaft, and a crank cap that holds the crankshaft together with the crankcase portion, the bore portion is connected to the crank The crank cap has the crank case part and the bore part by having a pressing member for assembling to the case part and fastening a first fastening bolt to a first female thread part formed on the pressing member. The pressure member presses the bore portion and the second fastening bolt is fastened to the second female screw portion formed on the pressure member, so that the cylinder head is assembled and the bore portion is When assembled with the crankcase part, an outer wall surrounding the bore part is formed integrally with the crankcase part. The features.
The pressing member here has a thickness such that, for example, the female screw part is provided vertically, the inner side is hollowed into a shape along the outer shape of the bore part, and the outer side is a shape along the substantially inner side. A shape having a mounting hole in which the first female screw portion and the second female screw portion are coaxial with each other at a position divided into four at equal angular intervals with respect to the central axis of each cylinder is conceivable.

(2) In the block division structure described in (1), an attachment portion is provided on a side of the bore portion that is in contact with the crankcase portion, and the pressing member has a plurality of surfaces on a surface that holds the bore portion. A pressing projection is provided, and the pressing projection presses the mounting portion when the bore portion is assembled.
Note that the attachment portion referred to here is rimmed on the side of the bore portion that contacts the crankcase portion. For example, the contact surface of the bore portion with the crankcase portion is on the outer side of the bore portion, and has a certain thickness. It is conceivable that the plate having the length is extended and the thickness of the mounting portion is thinner than that of the pressing member and is provided over the entire outer periphery of the bore portion.
The plurality of pressing protrusions herein refers to protrusions provided so that the bore portion and the pressing member are in point contact with each other. For example, a hemispherical shape having no corners to prevent stress concentration. It is. Furthermore, it is desirable to be provided at a position that is evenly allocated on the pressing member so that a load is evenly applied to the mounting portion. For example, it is conceivable that a circle on a plane perpendicular to the central axis of the cylinder is divided into eight so as to have the same angle, and provided for each of the assigned angles.

(3) In the block division structure described in (1) or (2), the bore portion is made of a part for each cylinder, and the first female screw portion formed on the pressing member is connected to the first female screw portion. When assembling the crank cap with the fastening bolt, a plurality of the bore portions are integrally assembled together with the crank case.
(4) In the block division structure described in any one of (1) to (3), the crankcase portion, the outer wall formed in the crankcase portion, the bore portion, and the cylinder head The enclosed space is filled with engine coolant.

According to the present invention having such characteristics, the following actions and effects can be obtained.
(1) In an engine block division structure including a bore portion in which a piston slides, a crankcase portion that holds a crankshaft, and a crank cap that holds the crankshaft together with the crankcase portion, the bore portion is connected to the crank The crank cap has the crank case part and the bore part by having a pressing member for assembling to the case part and fastening a first fastening bolt to a first female thread part formed on the pressing member. The pressure member presses the bore portion and the second fastening bolt is fastened to the second female screw portion formed on the pressure member, so that the cylinder head is assembled and the bore portion is When assembled with the crankcase part, an outer wall surrounding the bore part is formed integrally with the crankcase part. In addition to the minimum required size of the bore, the shape is simplified, and when assembled, it is held in a state of being sandwiched between the crankcase and the pressing member. It is held in the received state, and there is an excellent effect that the bore portion is hardly distorted and the shape accuracy of the bore portion is easily maintained.

In addition, since the bore portion is required to have a minimum size, an expensive material that can withstand high temperature and high pressure, which is the material of the bore portion, also has a minimum size, and the material cost can be reduced. Furthermore, materials that can withstand high temperatures and pressures are generally difficult to process, but they are not complex processes and do not have threaded parts, so that the number of processing steps can be reduced and the manufacturing cost can be reduced.
In addition, although a pressing member is required as a separate member, versatility is born by separating the bore part and parts, and there is a possibility that parts can be shared with other types of engines with the same number of cylinders. Cost reduction can be expected. Further, since it is not necessary to use the same material as the bore portion, the cost can be reduced and the material can be optimized.

(2) In the block division structure described in (1), an attachment portion is provided on a side of the bore portion that is in contact with the crankcase portion, and the pressing member has a plurality of surfaces on a surface that holds the bore portion. When the bore portion is assembled with the pressing projection, the pressing projection presses the mounting portion, so that the pressing member and the mounting portion of the bore portion do not come into surface contact, and at a plurality of points. By making point contact, the pressing force is dispersed and does not come into contact with each other. As a result, it is possible to prevent the stress from being biased and suppress the occurrence of distortion.
In addition, the attachment portion provided on the bore portion is provided on the side in contact with the crankcase and does not need to be screwed, so that it does not require a thickness as much as when forming a screw thread.
Since the mounting part is pressed by the pressing member, there is a considerable amount of distortion, but due to this, it is considered that it is not directly applied to the sliding part between the piston and the cylinder inner diameter in the bore part and is provided as far as possible. Further, it is possible to minimize the occurrence of distortion on the joint surface with the bore portion and the sliding portion. Furthermore, the occurrence of distortion can be reduced as compared with the case where a screw is provided directly in the bore portion.
In addition, since the pressing member is pressing the mounting portion of the bore portion by point contact, the distortion generated by being pulled by the first fastening bolt and the second fastening bolt during assembly is not directly transmitted to the bore portion, Since the pressing force is exerted by the pressing protrusions after being dispersed and averaged, when stress is transmitted, it can be expected that the stress is transmitted uniformly to the bore portion and the generation of strain is suppressed.

(3) In the block division structure described in (1) or (2), the bore portion is made of a part for each cylinder, and the first female screw portion formed on the pressing member is connected to the first female screw portion. When assembling the crank cap with the fastening bolt, a plurality of the bore portions are integrally assembled together with the crankcase, so that the bore portion is divided into a plurality of cylindrical bodies. It is possible to process the cylindrical body from a columnar or cylindrical member, and there is an excellent effect that a bore part can be created by lathe processing.
The cylindrical member can be generally processed from a cylindrical or columnar member, and the cylindrical and columnar members can be manufactured by a processing method such as extrusion processing due to the characteristics of the shape. A general engine block is manufactured by a method such as casting. If a cylindrical body that is a part of the bore can be manufactured by additional processing of a member made by extrusion, etc. In addition to ensuring uniformity, there is a possibility that the range of material selection is widened and the optimum member can be selected at a low cost. Furthermore, machining accuracy can be increased and machining can be performed at a lower cost by machining a cylindrical part and cylindrical member with a lathe than when casting parts are generally machined by milling. Also become.

(4) In the block division structure described in any one of (1) to (3), the crankcase portion, the outer wall formed in the crankcase portion, the bore portion, and the cylinder head Since the enclosed space is filled with engine coolant, there is no need to provide bolt holes for the first fastening bolts, and the shapes of the crankcase, outer wall, and bore are simplified. As a result, there is an excellent effect that the processing cost can be reduced. In addition, the space through which the coolant passes can be made more freely and contributes to the improvement of the cooling efficiency.

Embodiments of the present invention will be described below with reference to the drawings. First, the configuration of the first embodiment will be described.
(First embodiment)
FIG. 1 schematically shows a cross-sectional view of the engine in the first embodiment. FIG. 2 shows an assembled perspective view thereof.
As shown in FIG. 2, the bore portion 10 has a shape in which a plurality of cylinders are arranged. In the first embodiment, three cylinders are arranged in parallel. In general, the number of cylinders in the cylinder block represents the number of cylinders of the engine. In the first embodiment, the number of cylinders is three, that is, an inline three-cylinder engine is used as an example for easy explanation. Explains.
The cylinder inner diameter is generally referred to as a bore. In the first embodiment, the cylinder portion that guides the piston 12 is distinguished from a cylinder block including a jacket structure having a water channel for water cooling. Thus, the one in which the cylinders not including the jacket structure are arranged is referred to as the bore portion 10.

As shown in FIG. 1, a normal engine ignites a gas mixture of gasoline and air in a combustion chamber 20 inside the cylinder block 11 and causes an explosion to generate a force that causes the piston 12 to move up and down. The combustion gas generated at the time of explosion becomes 2000 ° C. or more, and a large force is generated by the explosion. Therefore, the bore portion 10 needs a high-strength material that can withstand such heat and force. In the past, cast iron was mainly used with emphasis on strength, workability, and heat resistance, but recently, for the purpose of reducing the weight of the engine itself, aluminum alloys, etc., or iron liners on aluminum alloy blocks, etc. The engine block is often provided with.
The material of the bore portion 10 of the first embodiment is an aluminum alloy for die casting. For example, a high-strength aluminum alloy for die casting having excellent castability such as ADC12 is used.

Further, the bore portion 10 shown in FIG. 2 includes an attachment portion 10a. The attachment portion 10a is provided with an edge so as to extend to the outer shape side of the bore portion 10 with a certain thickness in the form of extending the contact surface with the crankcase 13. Since it is not necessary to provide an internal thread part, the thickness of the attaching part 10a is about half or less of the thickness of the press member 21 mentioned later.
However, since this mounting portion 10a requires a high sealing performance between the bore portion 10 and the cylinder head 16 and the crankcase 13 when the bore portion 10 is assembled to the engine, the bolt to be assembled has a high tightening torque of about several tens of kN. Since the pressing member 21 is pressed against the crankcase portion 13a by the pressing member 21, a large force is applied to the mounting portion 10a. Therefore, the strength that can withstand it is necessary.

The crankcase 13 includes a crankcase portion 13a and an outer wall portion 13b.
A crankcase portion 13a shown in FIG. 1 is a room in which a connecting rod 14 that transmits the force of a piston 12 that moves up and down in the bore portion 10 and a crankshaft 15 that is connected to the connecting rod 14 are stored. Since the function of isolating from the outside so as not to enter and the function of receiving the crankshaft 15 are sufficient, the strength of the bore portion 10 is not required.
In the first embodiment, since the crankcase 13 is not provided with screw holes such as bolts for assembling the crank cap 17 and the bore portion 10 and the like, the material is configured using an inexpensive aluminum alloy for casting.
Next, the outer wall portion 13b is a wall surface formed outside the bore portion 10 when the bore portion 10 and the crankcase 13 are assembled.

This outer wall portion 13b is for forming a water channel between the bore portion 10 and the cylinder head 16, and an explosion occurs in the combustion chamber 20 as described above during engine operation, and when the gas pressure and temperature increase, Naturally, since the temperature of the bore portion 10 that is in direct contact with the combustion gas also rises, it is necessary to cool the bore portion 10 as in the case of a normal engine. In particular, an aluminum alloy is used as the material, and since the melting point of aluminum as the material is about 660 ° C., it is necessary to sufficiently cool it. Needless to say, the melting point of iron is about 1535 ° C., and if it is not cooled as it is, the bore portion 10 is melted by heat.
Therefore, a normal engine has a jacket structure, and it is necessary to pass cooling water through the inside to suppress heat generated during operation of the engine. For this reason, the outer wall portion 13b is required outside the bore portion 10, and cooling water flows between the bore portion 10 and the outer wall portion 13b so that the engine is always cooled.

As shown in FIG. 1, the cylinder head 16 is a part that forms part of the bore portion 10 and the combustion chamber 20, and is a part that receives pressure from heat and explosion as in the case of the bore portion 10. Aluminum alloy is used. The cylinder head 16 includes a valve, a camshaft, and the like.
A crank cap 17 is provided at the lower part of the crank case 13. As shown in FIG. 1, the crankcase portion 13 a and the crank cap 17 form a chamber in which the crankshaft 15 is accommodated and a portion that receives the shaft portion of the crankshaft 15. An oil pan (not shown) is fixed under the crank cap 17.

Next, FIG. 3 will be described. FIG. 3 is a plan view of the pressing member 21 and shows the surface of the portion to which the bore portion 10 hits.
As described above, the bore portion 10 has the mounting portion 10a provided at the edge. When the bore portion 10 is assembled to the crankcase 13, the pressing member 21 presses the mounting portion 10a of the bore portion 10.
The pressing member 21 is configured by a plate-like member that is wound in a shape in which three circles are connected so that the inside thereof is fitted to the outside of the cylindrical portion of the bore portion 10. The shape of the penetration portion 21c varies depending on the number of cylinders, and is formed in accordance with the shape of the bore portion 10.
The pressing member 21 includes a first female screw portion 21b on one surface and a second female screw portion 21a on the other surface. In addition, the 1st internal thread part 21b is visible on the surface shown by FIG.
In the first embodiment, the first female screw portion 21b and the second female screw portion 21a provided on the pressing member 21 have eight first female screw portions 21b on one surface and the second female screw portion 21a on the other surface. 8 are provided, and the first female screw portion 21b and the second female screw portion 21a are provided coaxially.
The first female screw portion 21b and the second female screw portion 21a are arranged one by one at the four corners of each cylinder, and share the first female screw portion 21b and the second female screw portion 21a with the adjacent cylinder. ing. Therefore, for example, in the case of an in-line four-cylinder engine, the number of the first female screw portion 21b and the second female screw portion 21a is increased by two to ten.

A pressing projection 21d is provided on the surface of the pressing member 21 on which the first female screw portion 21b is provided. The pressing protrusions 21d are provided to hold down the mounting portion 10a provided in the bore portion 10, and are distributed so as to be evenly positioned with reference to the center of each cylinder of the bore portion 10. For example, it is desirable to press the bore portion 10 so that the axial force of the fastening bolt is uniformly distributed in the circumferential direction, for example, the angle is divided into eight equal parts.
When assembled, the mounting portion 10a included in the bore portion 10 is pressed by the pressing protrusion 21d included in the pressing member 21, so that it is not a surface contact but a point contact, and a force is easily applied evenly.
Further, when the cylinder head bolt 18a and the crank cap bolt 18b are fastened, there is a possibility that the pressing member 21 is pulled upward or downward to cause distortion. Since it is a separate part, there is no direct distortion in the bore 10.

As shown in FIG. 2, when the bore portion 10 is assembled, the crank cap bolt 18b, which is the first fastening bolt, is tightened with the crank cap 17 sandwiched from the crank case portion 13a side, with a constant torque. The crank cap bolt 18b is tightened. However, if the crank cap 17, the crank case 13, and the bore portion 10 are sandwiched and tightened, naturally the flatness of each surface and the relative parallelism do not appear, and the crank cap bolt 18 b is evenly distributed. Even if tightened, it is inevitable that the tightening torque will vary. Further, the torque management itself of the crank cap bolt 18b cannot be performed completely in the same way in the mass production process.
When the bore portion 10 and the pressing member 21 are in surface contact, if those conditions are not cleared, a contact between the bore portion 10 and the portion that is pressed strongly and a portion that is pressed weakly occur. In such a case, an imbalance is generated in the force applied to the bore portion 10, and a constant surface pressure cannot be secured, and a distortion that affects the shape accuracy of the bore portion 10 occurs in the bore portion 10.
Therefore, in order to avoid these problems, the bore portion 10 and the pressing member 21 are brought into point contact, and the positions of the pressing protrusions 21d are distributed so as to be equal with respect to the center of each cylinder. Consideration is given to applying a uniform force.

Next, assembly of the above parts will be described.
FIG. 4 shows a bolt fastening state, FIG. 4 (a) is a schematic view showing a state in which the cylinder head bolt 18a and the crank cap bolt 18b are fastened to the bore portion 10, and FIG. 4 (b) is a fastening portion. The enlarged view of is shown.
Further, the assembled state is shown in FIG. FIG. 5 is a perspective sectional view showing a state in which the bore portion 10, the crankcase 13, the cylinder head 16, and the crank cap 17 are assembled. FIG. 5 is a perspective sectional view taken along a section different from FIG. Show.
As shown in FIG. 5, the bore portion 10 is assembled inside the crankcase 13 and inside the outer wall portion 13 b, and the cylinder head 16 is assembled on the upper surface thereof. The cap 17 is assembled.

In this case, as shown in FIG. 4, the crank cap bolt 18 b that is the first fastening bolt and the cylinder head bolt 18 a that is the second fastening bolt are all included in the first female screw portion 21 b and the first fastening screw 21 b provided in the pressing member 21. 2 Fastened to the female screw portion 21a. Accordingly, the cylinder head 16 is assembled by tightening the cylinder head bolt 18a to the second female screw portion 21a provided on the pressing member 21 from the cylinder head 16 side with a metal gasket (not shown) interposed therebetween, and the crank cap 17 is The crankcase 13 is disposed so as to sandwich the crankcase 13, and is assembled by tightening the crank cap bolt 18 b into the first female screw portion 21 b provided from the crankcase 13 side of the pressing member 21. At this time, the mounting portion 10 a of the bore portion 10 is directly pressed against the pressing member 21 and is sandwiched together with the crankcase 13.
In this way, the mounting portion 10a provided to the crankcase 13 and the bore portion 10 is assembled so as to be sandwiched between the pressing member 21 and the crank cap 17, so that it is always subjected to compressive stress in the assembled state. Become.

A contact surface between the bore 10 and the cylinder head 16 sealed by sandwiching a metal gasket or the like is configured by being surrounded by the inner surface of the bore 10, the upper part of the piston 12, and the cylinder head 16. The combustion chamber 20 is required to have high sealing performance because high-temperature and high-pressure combustion gas is generated. Therefore, the cylinder head bolt 18a is tightened with a high torque of about several tens of kN.
Further, the contact surface 10d between the crankcase 13 and the bore portion 10 is sealed using a liquid gasket or the like because sealability is required so that coolant or the like does not leak.
Surface pressure required to fasten the crank cap bolt 18b with a high torque of several tens of kN to the second female screw portion 21a of the pressing member 21 that holds the crank case 13 between the crank case 13 and presses the mounting portion 10a provided in the bore portion 10. Can be secured. Accordingly, the sealing performance between the outer surface of the bore portion 10 and the water channel 19 which is a space formed by the inner surface of the outer wall portion 13b of the crankcase 13 is maintained.
In addition, since the bolt hole of the crankcase 13 provided for the crank cap bolt 18b is provided in the surface which comprises the water channel 19, it seals separately so that cooling water may not leak. For example, a seal is made on the contact surface between the crank cap bolt 18b and the crank cap 17 and a necessary surface pressure can be secured, so that the coolant does not leak.

FIG. 6 is a cross-sectional view of the crankcase 13 with the bore portion 10 assembled thereto. From FIG. 6, it can be seen that there are spaces provided at regular intervals on the outer periphery of the bore portion 10 and on the inner periphery of the outer wall portion 13 b of the crankcase 13. This space is a water channel 19 for passing cooling water of the engine, and the gap between the bore portion 10 and the outer wall portion 13b is set to several mm, and the cooling water flows between them, and this occurred during operation of the engine. Reduce heat. The cylinder head bolt 18a is submerged in the coolant. However, if the cylinder head bolt 18a is corroded by the material used, the cylinder head bolt 18a is coated with a rust preventive agent, and a material that does not corrode is used. Just do it.
In addition, since the crank cap bolt 18b also comes into contact with the coolant, if necessary, rust prevention measures are taken.

Next, the function and effect of the first embodiment will be described.
First, since it is assembled as described above, the bore portion 10 receives only compressive stress. Therefore, there is an advantage that stress management becomes easy. In addition, an optimum material can be selected by concentrating the screw portions in the pressing member 21 without providing the screw portions in the bore portion 10.
Further, the mounting portion 10a provided in the bore portion 10 is pressed against the crankcase portion 13a via the pressing protrusion 21d provided in the pressing member 21, but the pressing member 21 and the mounting portion 10a may come into contact with each other. Since the pressing protrusions 21d are distributed so as to be evenly positioned with respect to the center of each cylinder, the tightening torque of the crank cap bolt 18b is evenly distributed, and the stress applied to the bore portion 10 is not easily biased. Consideration has been made to suppress the occurrence of distortion.

As described above, since the bore portion 10 is subjected to a large load due to heat and pressure and requires strength, it is necessary to use an expensive material. Therefore, by separating the bore portion 10 and the outer wall portion 13b, it is possible to reduce the volume of the portion using the expensive material and reduce the cost.
Further, the shape of the bore portion 10 is composed of the bore portion 10 and the mounting portion 10a, and the shape is simplified and the shape is simplified. Therefore, in the case where the bore portion 10 is manufactured by casting or the like, the flow of hot water is improved. There is also a merit that it is difficult to form a nest, requires strength, and it is easy to ensure the quality of the bore portion 10 having strict quality standards.
In addition, since the size of the bore portion 10 can be reduced, the weight can be reduced as a result, which contributes to improvement of workability even when finishing or plating is required.

  In addition, the pressing member 21 is provided with a first female screw portion 21b and a second female screw portion 21a, and has a large size of about several tens of kN in order to prevent leakage of combustion gas, cooling water, and the like at the joint surface of each component. Since torque must be tightened with the crank cap bolt 18b and the cylinder head bolt 18a with torque, strength is required. Therefore, although a high-strength material is required, functions such as shape stability at high temperatures and sliding resistance, which are required for the bore portion 10, are not required. Since the shape becomes a plate shape and becomes simple, for example, it is also possible to manufacture the plate material by press working or the like. By using a plate material, there are merits such as uniformity of quality compared to using a casting material, and it becomes possible to manufacture at a relatively low cost.

Next, regarding the crankcase 13, since the crankcase portion 13a and the outer wall portion 13b are integrally formed, there is an advantage that structural strength can be obtained.
Further, by integrally forming the crankcase portion 13a and the outer wall portion 13b, unlike the method of Patent Document 4, there is no need to worry about leakage of coolant from between the crankcase portion 13a and the outer wall portion 13b. There is no need for a seal structure.
Furthermore, since both the crankcase portion 13a and the outer wall portion 13b are parts that do not require much strength, the crankcase 13 that is a portion that does not need much strength can be made of an inexpensive material.

In this way, the parts that require strength, such as the bore portion 10, the mounting portion 10a, and the pressing member 21, are gathered to minimize the portions that require strength, and the crankcase portion that does not require much strength originally. By forming the crankcase 13 by integrally forming the outer wall portion 13a and the outer wall portion 13b, even if an expensive material is used for improving the performance of the bore portion 10, a relatively inexpensive material is used for the crankcase 13. Since it can be manufactured, even if the performance of the engine is improved, the cost increase can be suppressed as compared with the conventional method.
And compared with the case where the bore part 10 is provided with the crankcase part 13a as in Patent Document 4 and is made by casting, the cost can be reduced by about 30 to 50% in general, although depending on the size and shape, the engine Since the bore part 10 can be changed by the output of, it is possible to change the material of only the bore part 10 by using the pressing member 21 and the crankcase 13 as common parts, and corresponding to the engine with different output with the same design. There are also benefits that can be achieved.

Further, in a state where the bore portion 10 and the crankcase 13 are combined, the engine coolant can be passed through the outer wall portion 13b provided in the crankcase 13 and the space surrounded by the bore portion 10, the crankcase portion 13a, and the cylinder head. It becomes possible. As a result, it is not necessary to separately manufacture the water passage having a complicated shape in the crankcase 13 or the bore portion 10 and the holes for the first fastening bolts provided therebetween, so that the processing cost can be reduced and the shape can be reduced. Simplification can also be expected to improve quality.
As a result, the cylinder head bolt 18a and the crank cap bolt 18b may need to be protected against rust. However, the cost of manufacturing a hole and the rust prevention on the cylinder head bolt 18a and the crank cap bolt 18b may be required. Compared with the cost of taking countermeasures, the cost of drilling a hole is considered in total, considering the improvement in quality, the simplification of processing, the shortening of the lead time due to the reduction of processing time, etc. It is thought that there is a merit because it is possible to make the cap bolt 18b rust prevention measures at a low cost.

Further, the cylinder head 16 is assembled by fastening the cylinder head bolt 18a to the second female screw portion 21a provided from the cylinder head 16 side to the pressing member 21 with a metal gasket or the like interposed therebetween. 13 is arranged so that the crank cap bolt 18b is fastened to the first female screw portion 21b provided from the crank case 13 side of the pressing member 21.
As described above, the crankcase 13 is assembled so as to be sandwiched between the pressing member 21 and the crank cap 17 in the same manner as the bore portion 10, so that it is always subjected to compressive stress in the assembled state. It is easy to guarantee strength against fatigue failure.
Since the engine constantly burns the gasified fuel in the combustion chamber 20 during operation, the engine is always exposed to vibration and heat, and there is stress fluctuation, so that fatigue tends to accumulate in the material metal. Therefore, it is easier to manage fatigue failure when the stress is always applied in one direction.

(Second embodiment)
Next, a second embodiment according to the present invention will be described.
FIG. 7 shows an assembled perspective view of the pressing member 21, the bore portion 10, and the crankcase 13 of the second embodiment.
The configuration is substantially the same as in the first embodiment, but the configuration of the bore portion 10 is different.
The bore portion 10 includes three parts, a first cylinder 31, a second cylinder 32, and a third cylinder 33. Further, since the mounting portion 10a is also divided into respective cylinder portions, the first cylinder 31 has a first cylinder mounting portion 31a, the second cylinder 32 has a second cylinder mounting portion 32a, and the third cylinder 33 has a first cylinder. Divided into a three-cylinder mounting portion 33a.
In the first and second embodiments, an in-line three-cylinder engine is described, but the same configuration is obtained even when the number of cylinders is four or more. For example, in the case of an in-line four cylinder, the bore portion 10 is divided into four parts, one having the same shape as the first cylinder 31 and the third cylinder 33, and two having the same shape as the second cylinder 32 interposed therebetween. Therefore, the engine has a total of four cylinders. In this case, it goes without saying that the shape of the pressing member 21 is also changed, and the shape of the crankcase 13 is changed accordingly.

Further, although not specifically described in the first embodiment, normally, the bore portion 10 is provided with a narrow channel 10e between the cylinders in order to cool the bore portion 10.
The narrow channel 10e is formed by processing each of the first cylinder 31, the second cylinder 32, and the third cylinder 33.
The bore portion 10 of the second embodiment having such a configuration is assembled in the same manner as the first embodiment, and the first cylinder 31, the second cylinder 32, and the third cylinder constituting the bore portion 10 by the pressing member 21. 33 is integrally assembled to the crankcase 13.

The operational effect of the second embodiment having such a configuration has the same operational effects as those of the first embodiment, and further exhibits the following excellent effects.
First, since the bore portion 10 has a divided structure, the first cylinder 31, the second cylinder 32, and the third cylinder 33 are substantially cylindrical. For this reason, it becomes possible to process the material from a cylindrical or cylindrical extruded material. Usually, when a part is manufactured by casting, a certain degree of nest must be predicted, which affects the yield of the material. In addition, due to the nature of casting in which the molten material is solidified, it is inferior to a manufacturing method such as extrusion in terms of homogenizing the material.
Therefore, by forming a shape that can be processed using a lathe from a cylindrical or cylindrical material, the material can be homogenized and the processing cost can be reduced. In addition to reducing the size of the workpiece, the accuracy of the processing method can be improved easily. In the case of casting, it is necessary to produce the required accuracy by boring and milling after creating a rough shape by casting, but these machining methods are used when machining with a lathe. This is because it is difficult to obtain shape accuracy such as roundness and machined surface roughness.

Therefore, if the bore portion 10 is divided into the first cylinder 31, the second cylinder 32, and the third cylinder 33 as in the second embodiment and can be machined by a lathe, the number of parts is increased, but the machining cost is increased. And there is a possibility that parts can be shared by a combination such as inline 3 cylinder and inline 4 cylinder, leading to cost reduction.
Further, when processing the narrow channel 10e, the closer the distance between the cylinders, the higher the performance due to the design problem. Therefore, the wall of this part becomes thin, and the bore portion 10 as in the first embodiment is formed. When the cylinder block itself is integrated, it is necessary to additionally process the narrow channel 10e using a thin drill. Since the bore portion 10 is a component that requires strength, parts that are generally difficult to process are often used. Particularly, drilling with a thin drill becomes easier to break as the diameter of the drill decreases even in normal processing. Therefore, the processing of the narrow channel 10e is a processing that requires a short tool life and is expensive.
However, since the bore portion 10 is divided into the first cylinder 31, the second cylinder 32, and the third cylinder 33, the side surface can be machined by a milling machine, etc., and the machining time can be shortened and the machining cost is also reduced. There is a merit that it can be reduced.

As described above, according to the block division structure of the present invention, the following excellent effects can be obtained.
(1) In a block division structure of an engine including a bore portion 10 on which a piston 12 slides, a crankcase portion 13a that holds a crankshaft 15, and a crank cap 17 that holds the crankshaft 15 together with the crankcase portion 13a. A crank member 17 has a pressing member 21 for assembling the bore portion 10 to the crankcase portion 13a, and a crank cap bolt 18b is fastened to a first female screw portion 21b formed on the pressing member 21, whereby the crank cap 17 is cranked. The case member 13a and the bore portion 10 are assembled and the pressing member 21 presses the bore portion 10, and the cylinder head bolt 18a is fastened to the second female screw portion 21a formed on the pressing member 21, whereby the cylinder The head 16 is assembled and the bore 10 is assembled with the crankcase 13a. Since the outer wall portion 13b surrounding the bore portion 10 is integrally formed with the crankcase portion 13a when the bore portion 10 is formed, the bore portion 10 can be of a minimum size and the shape is simple. When assembled, it is held in a state of being sandwiched between the crankcase portion 13a and the pressing member 21, so that it is held in a state where only the compressive stress is received, and the bore portion 10 is unlikely to be distorted. There is an excellent effect that shape accuracy is easily maintained.

In addition, since the bore portion 10 can be of a minimum size, an expensive material that can withstand the high temperature and high pressure, which is the material of the bore portion 10, is also a minimum size, and the material cost can be reduced. Furthermore, materials that can withstand high temperatures and pressures are generally difficult to process, but they are not complex processes and do not have threaded parts, so that the number of processing steps can be reduced and the manufacturing cost can be reduced.
In addition, although the pressing member 21 is required as a separate member, versatility is born by separating the bore 10 and the components, and there is a possibility that the components can be shared with other types of engines of the same number of cylinders. As a result, production costs can be reduced. Further, since it is not necessary to use the same material as that of the bore portion 10, the cost can be reduced and the material can be optimized.

(2) In the block division structure described in (1), the mounting portion 10a is provided on the side of the bore portion 10 in contact with the crankcase portion 13a, and the pressing member 21 has a plurality of surfaces on which the bore portion 10 is pressed. When the bore portion 10 is assembled, the pressing projection 21d presses the mounting portion 10a. Therefore, the pressing member 21 and the mounting portion provided in the bore portion 10 do not come into surface contact. By making point contact at a plurality of points, the pressing force is dispersed and does not come into contact with each other. As a result, it is possible to prevent stress unevenness and suppress the occurrence of distortion.
Further, the attachment portion 10a provided on the edge of the bore portion 10 is provided on the side in contact with the crankcase 13 and does not need to be screwed. Therefore, the attachment portion 10a does not need to be as thick as when a screw thread is formed.
Since the mounting portion 10a is pressed by the pressing member 21, a considerable amount of distortion occurs. However, due to this, there is a consideration that the mounting portion 10a is not directly applied to the sliding portion of the piston 12 and the inner diameter of the cylinder in the bore portion 10 and is provided as far as possible. Therefore, the influence of distortion on the joint surface with the bore portion 10 and the sliding portion can be minimized. Furthermore, the occurrence of distortion can be reduced more than when the screw is provided directly in the bore portion 10.
Further, since the pressing member 21 pushes the mounting portion 10a of the bore portion 10 by point contact, the bore portion directly affects the influence of distortion generated by being pulled by the cylinder head bolt 18a and the crank cap bolt 18b during assembly. Since the pressing force is exerted by the pressing protrusions after being dispersed and averaged without being transmitted to 10, the stress can be expected to be uniformly transmitted to the bore portion 10 and the generation of distortion can be suppressed.

(3) In the block division structure described in (1) or (2), the bore portion 10 is composed of parts for each cylinder, and a crank cap bolt is connected to a first female screw portion 21b formed in the pressing member 21. When assembling the crank cap 17 at 18b, the plurality of bore portions 10 are integrally assembled together with the crankcase 13, so that the bore portion 10 is divided into a plurality of cylindrical bodies, so that It is possible to process the cylindrical body from a columnar or cylindrical member, and there is an excellent effect that the bore portion 10 can be created by lathe processing.
The cylindrical member can be generally processed from a cylindrical or columnar member, and the cylindrical and columnar members can be manufactured by a processing method such as extrusion processing due to the characteristics of the shape. A general engine block is manufactured by a method such as casting. However, if a cylindrical body that is a part of the bore portion 10 can be manufactured by additionally processing a member made by extrusion or the like, a material can be used. In addition to ensuring uniformity, there is a possibility that the range of material selection is widened and the optimum member can be selected at a low cost. Furthermore, machining accuracy can be increased and machining can be performed at a lower cost by machining a cylindrical part and cylindrical member with a lathe than when casting parts are generally machined by milling. Also become.

(4) In the block division structure described in any one of (1) to (3), the crankcase portion 13a, the outer wall portion 13b formed in the crankcase portion 13a, the bore portion 10, and the cylinder head 16 is filled with engine coolant, so that it is not necessary to provide a bolt hole for the cylinder head bolt 18a, and the crankcase portion 13a, the outer wall portion 13b, and the bore portion are provided. Since the shape of 10 can be simplified, there is an excellent effect that the processing cost can be reduced. In addition, the space through which the coolant passes can be made more freely and contributes to the improvement of the cooling efficiency.

In addition, this invention is not limited to 1st Embodiment and 2nd Embodiment, A various change is possible in the range which does not deviate from the meaning.
For example, in the first example and the second embodiment, an aluminum alloy for die casting such as ADC 12 is used for the bore portion 10, but the material is not particularly limited to this material. For example, aluminum casting by other casting or forging It is possible to use not only aluminum but also cast iron or the like. In short, it does not prevent the selection of other materials that can withstand the heat and pressure generated in the combustion chamber 20.
The crankcase 13 and the cylinder head 16 are also made of an aluminum alloy for casting, but the material is not particularly limited to this.

Sectional drawing of the engine in the 1st example and the 2nd example is shown. The assembly perspective view of a bore part, a press member, and a crankcase in the 1st example is shown. The top view of the single side | surface of the press member in 1st Example is shown. (A) The perspective view of the state which assembled | attached the bore part, the press member, the crankcase outer wall part, the 1st fastening bolt, and the 2nd fastening bolt in 1st Example is shown. (B) The partial detailed sectional view of the pressing member, the 1st fastening bolt, and the 2nd fastening bolt in the 1st example is shown. The assembly perspective sectional view of a cylinder head, a crankcase, a bore part, a crank cap, a 1st fastening bolt, and a 2nd fastening bolt in the 1st example is shown. It is sectional drawing in the state which assembled | attached the bore part to the crankcase in 1st Example. The assembly perspective view of a bore part, a press member, and a crankcase in the 2nd example is shown. 1 is a cross-sectional view of an engine structure in Patent Document 1. FIG. FIG. 6 is a cross-sectional view of an engine structure in Patent Document 2. FIG. 6 is a cross-sectional view of an engine structure in Patent Document 3. FIG. 6 is a perspective view showing how an engine is assembled in Patent Document 4. It is assembly sectional drawing of an engine in Japanese Patent Application No. 2005-112155.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Bore part 10a Attachment part 10d Contact surface 10e Narrow flow path 11 Cylinder block 12 Piston 13 Crankcase 13a Crankcase part 13b Outer wall part 14 Connecting rod 15 Crankshaft 16 Cylinder head 17 Crank cap 18a Cylinder head bolt 18b Crank cap bolt 19 Water channel 20 Combustion Chamber 21 Press member 21a Second female screw portion 21b First female screw portion 21c Penetrating portion 21d Protrusion 31 First cylinder 31a First cylinder mounting portion 32 Second cylinder 32a Second cylinder mounting portion 33 Third cylinder 33a Third cylinder Mounting part

Claims (4)

In the block division structure of the engine comprising a bore portion where the piston slides, a crankcase portion holding the crankshaft, and a crank cap holding the crankshaft together with the crankcase portion,
A pressing member for assembling the bore portion to the crankcase portion;
A first fastening bolt is fastened to a first female screw portion formed on the pressing member, whereby the crank cap is assembled with the crank case portion and the bore portion interposed therebetween, and the pressing member is connected to the bore portion. Hold down
The cylinder head is assembled by fastening the second fastening bolt to the second female screw portion formed on the pressing member,
A block division structure, wherein an outer wall surrounding the bore portion is integrally formed with the crankcase portion when the bore portion is assembled with the crankcase portion. In the block division structure according to claim 1,
The mounting portion is provided on the side of the bore portion in contact with the crankcase portion,
The pressing member includes a plurality of pressing protrusions on a surface that presses the bore portion,
The block division structure, wherein the pressing projection presses the mounting portion when the bore portion is assembled. In the block division structure according to claim 1 or 2,
The bore part is composed of parts for each cylinder,
When assembling the crank cap with the first fastening bolt to the first female thread portion formed on the pressing member, a plurality of the bore portions are integrally assembled together with the crank case. Block division structure to be performed. In the block division structure according to any one of claims 1 to 3,
A block division structure characterized in that engine coolant is filled in a space surrounded by the crankcase part, an outer wall formed in the crankcase part, the bore part, and a cylinder head.

Images