JP4501756B2 - Block division structure - Google Patents

Description

  The present invention relates to a method of dividing a cylinder block of an engine into two parts and separating a part requiring particularly high strength and a part not particularly requiring high 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.
In addition, 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 particles 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, 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-mentioned 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. 7 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. 9 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. 10 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 150.

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, machining costs 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 particle on the cylinder 154 inner peripheral surface 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, the prior art has the following problems.
First, in the method of Patent Document 4, since the entire cylinder block portion is manufactured by extrusion molding or forging, the portion 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, as the rigidity of the inner cylinder part of the cylinder is further increased and the cost of parts is required to be reduced, it is necessary to keep the cost to a minimum by configuring high-quality parts to the minimum necessary.
The first problem is that parts such as outer walls that do not need much strength are also made of high-rigidity materials because they include parts that require rigidity, resulting in excessive quality. A point is considered.

Further, in the engine blocks of Cited Document 1 to Cited Document 3, the screw part for assembling the cylinder head, the engine block, the crank cover and the like is provided on the outside of the jacket of the cylinder part, and can be assembled evenly. The device has been devised so as not to bring the strain generated by fastening at the inner surface of the cylinder, which is the piston sliding surface.
Also in the cited document 4, by bringing the female thread portion on the crankcase portion 152 side, only the compressive stress is applied to the cylinder portion 151, and a contrivance is made so as not to generate distortion in the cylinder 154. ing.
Such a problem has been pointed out heretofore, and in the present invention as well, it is necessary to solve the above problem (1) and at the same time, avoid distortion in the piston sliding surface.

In a general engine, a piston slides on the inner surface of a cylinder at a high speed.
This is because the higher the performance of the engine, the higher the speed of the engine, and the greater the impact of the sliding between the piston and the inner surface of the cylinder. Even frictional heat is generated. 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 works by being pushed against the inner surface of the cylinder. However, when using a circular piston, if the roundness of the inner surface of the cylinder is low, the sliding resistance In addition, the clearance between the piston ring and the inner wall of the cylinder becomes larger than allowed, and the intrusion of excess oil into the combustion chamber is increased. 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.
This is because 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 distortion generated by tightening the bolt gives shape accuracy. The effect is large, and when closed near the piston sliding surface, the roundness of the cylinder inner surface may be distorted due to distortion, and a gap may appear between the piston ring fitted into the piston and the cylinder inner surface. Because.
The second problem is that it is necessary to eliminate as much as possible the influence on the shape accuracy of the cylinder inner surface that slides with the piston due to the distortion generated by the fastening of the bolt for assembling the engine. Can be considered.

It should be noted that since the influence of the distortion generated due to the above-mentioned causes is easily influenced by heat, it is an important factor that the engine can be sufficiently cooled and the temperature can be controlled. Since engine performance is increasing year by year and miniaturization is required, it is important to secure a water channel with sufficient cooling performance in a limited space.
A third problem is that it is necessary to ensure the cooling performance of the engine.

  Therefore, the present invention has been made to solve the above-described problems, and by dividing the parts where the strength of the cylinder block is necessary and the parts that are not so, the parts that need the strength are aggregated. An object of the present invention is to provide a cylinder block division structure that minimizes the number of high-quality parts, minimizes distortion to the inner surface of the cylinder, and does not impair the cooling performance.

In order to achieve the above object, the present invention has the following features.
(1) In a block division structure of an engine 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 formed. The cylinder head is fastened to the first female screw portion by a first fastening bolt, and the crank cap is fastened to the crankcase portion by a second fastening bolt to the second female screw portion formed in the bore portion. An outer wall is formed integrally with the crankcase portion so as to surround the bore portion when the bore portion is assembled with the crankcase portion.

(2) In the block division structure described in (1), an attachment portion is provided on a side of the bore portion that contacts the crankcase portion, and the attachment portion is provided with the first female screw portion, The second female screw portion is provided on a side facing the first female screw portion.
(3) In the block division structure described in (1) or (2), in a space surrounded by the crankcase part, an outer wall formed in the crankcase part, the bore part, and the cylinder head The engine coolant is filled.

According to the present invention having such characteristics, the following actions and effects can be obtained.
(1) In a block division structure of an engine 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 formed. The cylinder head is fastened to the first female screw portion by a first fastening bolt, and the crank cap is fastened to the crankcase portion by a second fastening bolt to the second female screw portion formed in the bore portion. When the bore portion is assembled with the crankcase portion, an outer wall surrounding the bore portion is formed integrally with the crankcase portion when the bore portion is assembled with the crankcase portion. The first female screw part and the second female screw part are integrated into the necessary bore part, and the crank cap and the outer wall, which do not require strength, are integrated into a crank cap. So as to sandwich at flop, by engagement with the second fastening bolt in the bore, it is reduced as much as possible the parts is excessive quality, an excellent effect that it is possible to suppress the cost. In addition, since the portions requiring strength are concentrated in the bore portion, it can be made smaller than making it integrally with other portions, and the workability of the bore portion is improved.

(2) In the block division structure described in (1), an attachment portion is provided on a side of the bore portion that contacts the crankcase portion, and the attachment portion is provided with the first female screw portion, Since the second female threaded portion is provided on the side facing the first female threaded portion, it is possible to cut the screw on the mounting portion that is rimmed with the strong bore portion, which is necessary. In addition to being able to fasten with a strong fastening force, it requires high sealing performance and is far away from the joint surface of the cylinder head and bore so that the sliding part between the piston and cylinder inner diameter is not affected as much as possible. By arranging the threaded portion, there is an excellent effect of minimizing the influence of distortion on the joint surface with the bore portion and the sliding portion.

(3) In the block division structure described in (1) or (2), in a space surrounded by the crankcase part, an outer wall formed in the crankcase part, the bore part, and the cylinder head Since the engine coolant is filled, there is no need to provide a bolt hole for the first fastening bolt, and the shape of the crankcase part, the outer wall part, and the bore part can be simplified. There is an excellent effect that can be reduced. It is also possible to make a wide space for the coolant to pass.

Embodiments of the present invention will be described below with reference to the drawings. First, the configuration of the embodiment will be described.
FIG. 1 schematically shows a cross-sectional view of the engine in the present embodiment. FIG. 2 is a component diagram, FIG. 2 (a) is a perspective view of the bore portion, and FIG. 2 (b) is a perspective view of the crankcase portion.
As shown in FIG. 2A, the bore portion 10 has a shape in which a plurality of cylinders are arranged, and in this 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 this embodiment, the number of cylinders is three, that is, an inline three-cylinder engine is used as an example for easy explanation. is doing.
In general, the inner diameter of the cylinder is referred to as a bore. In this embodiment, the cylinder portion that guides the piston 12 is distinguished from a cylinder that is a cylinder including a jacket structure for water cooling. A structure in which cylinders not including a jacket structure are arranged is referred to as a 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 11, and generates 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. Is often provided.
The bore portion 10 of this embodiment employs an aluminum alloy for die casting. For example, a high-strength aluminum alloy for die casting having excellent castability such as ADC12 is used.

Moreover, as shown to Fig.2 (a), the bore part 10 is provided with the bolt seat part 10a used as an attaching part, and is provided with the 1st internal thread part 10b and the 2nd internal thread part 10c.
The first female screw portion 10b and the second female screw portion 10c provided on the bolt seat portion 10a are provided on the same axis parallel to the center line of the bore portion 10, and are connected to the first fastening bolt 18a shown in FIG. When the second fastening bolt 18b is tightened with a necessary torque, as many threads as necessary are formed.
Further, the bolt seat portion 10a is edged so that the cylindrical member projects from the side surface of the bore portion 10 on the side assembled with the crankcase 13 by a plate-like member. And the 1st internal thread part 10b. The second female screw portion 10c is directed to a location located at the center of the cylindrical member. In this case, it is desirable that the bolt seat portion 10a is received even in a state where the bore portion 10 is not distorted. In this embodiment, the bolt seat portion 10a is integrally formed by casting. Alternatively, a joining method such as welding may be used as long as distortion during processing can be removed and position accuracy can be obtained.
Further, the thickness of the bolt seat portion 10a is only a thickness necessary for forming the first female screw portion 10b and the second female screw portion 10c, and the connection portion of the bore portion 10 with the main body is as follows. It is thinner than the portion where the first female screw portion 10b and the second female screw portion 10c are provided.
In the present embodiment, a total of eight bolt seats 10a are provided. Each cylinder 11 is arranged so as to be located at an equal distance, one at each of the four corners, and is configured to share the bolt seat 10a with the adjacent cylinder 11. Therefore, for example, in the case of an in-line four-cylinder engine, the number of bolt seats 10a is increased to two to be ten.
Of course, in order to disperse the distortion, it is effective to increase the bolt seat portion 10a to the equally divided position, but since it is necessary to consider the balance with the downsizing of the engine, the current situation is such an arrangement. It has become.

FIG. 2 (b) shows the crankcase 13, which comprises 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 it is sufficient to have a function of isolating from the outside so as not to enter and a function of receiving the crankshaft 15, it does not require much strength.
In this embodiment, the crankcase 13 is not provided with a screw hole such as a bolt that needs to be fastened with a strong torque, and therefore, 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.

During engine operation, an explosion occurs in the combustion chamber 20 as described above, and the gas pressure and temperature increase. Naturally, the temperature of the bore 10 that is in direct contact with the combustion gas also rises. However, the melting point of aluminum as a material is about 660 ° C., and even iron is about 1535 ° C., and if not cooled as it is, the bore portion 10 is melted by heat.
Therefore, it is usually necessary to use a jacket structure to allow cooling water to pass through and cool the engine to operate 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. This situation is also shown in the cross-sectional view of FIG.

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 like the bore portion 10. The 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, assembly of the above parts will be described.
FIG. 3 shows a bolt fastening state, FIG. 3 (a) is a schematic view of a state in which the first fastening bolt 18a and the second fastening bolt 18b are fastened to the bore portion 10, and FIG. 3 (b) shows a fastening portion. The enlarged view of is shown. The assembled state is shown in FIG. 4 is a perspective sectional view of the state in which the bore portion 10, the crankcase 13, the cylinder head 16, and the crank cap 17 are assembled, and FIG. 5 is a perspective sectional view cut 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, from the lower side of the crankcase 13. A crank cap 17 is assembled.

In this case, as shown in FIG. 4, the eight first fastening bolts 18 a and the eight second fastening bolts 18 b are all fastened to the bolt seat portion 10 a provided in the bore portion 10.
Thus, the cylinder head 16 is assembled by tightening the first fastening bolt 18a to the first female screw portion 10b provided on the bolt seat portion 10a 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 second fastening bolt 18b into the second female screw portion 10c provided in the bolt seat portion 10a.
Therefore, the crankcase 13 is assembled so as to be sandwiched between the bore portion 10 and the crank cap 17, so that it is always subjected to compressive stress in the assembled state.

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. In order to generate high-temperature and high-pressure combustion gas in the combustion chamber 20, the high sealing performance is required. Therefore, the first fastening bolt 18a needs to be fastened with a high torque of several tens of kN.
Further, the joint 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 the coolant or the like does not leak.
At the joint surface 10d, the crankcase 13 is sandwiched between the crank cap 17 and the second fastening bolt 18b is fastened to the second female screw portion 10c of the bolt seat portion 10a provided in the bore portion 10 with a high torque of about several tens of kN. It is possible to ensure the necessary surface pressure. 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.

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 through which engine cooling water passes, and the gap between the bore portion 10 and the outer wall portion 13b is set to about several millimeters. The cooling water flows during this time, thereby suppressing the heat generated during engine operation. Note that the first fastening bolt 18a is submerged in the coolant, and therefore, the first fastening bolt 18a is subjected to rust prevention measures using a paint such as a rust preventive material.

Next, the function and effect of this embodiment will be described.
First, with respect to the bore portion 10, the bolt seat portion 10a is provided on the bore portion 10, and the first female screw portion 10b and the second female screw portion 10c are formed on the bolt seat portion 10a. The bore part 10 has an advantage that the first female screw part 10b and the second female screw part 10c having the same strength can be integrated into the bore part 10.
As described above, the bore portion 10 is subjected to a large load due to heat and pressure and requires strength, and the bolt seat portion 10a provided with the first female screw portion 10b and the second female screw portion 10c has combustion gas and cooling. This is because strength is required because the first fastening bolt 18a and the second fastening bolt 18b must be tightened with a large torque of several tens of kN in order to prevent leakage of water or the like. In particular, for the seal on the combustion chamber 20 side, since severe sealability is required, torque management is an important matter.

Further, since the shape of the bore portion 10 becomes simple, in the case where the bore portion 10 is manufactured by casting or the like, the effect of improving the flow of hot water is obtained, the nest is difficult to form, the strength is required, and the quality standard There is also a merit that it is easy to ensure the quality of the severe bore portion 10. Of course, even when a processing method such as forging is used, it is the same that the shape becomes simple and the workability is improved and the quality is easily secured.
Further, with respect to the structure of the bore portion 10, the bolt seat portion 10 a is provided on the crankcase portion 13 a side and is positioned as far as possible from the sliding portion between the combustion chamber 20 and the piston 12. This method is a commonly used method, but when the bore part 10 and the outer wall part 13b are separately manufactured as in this embodiment, the same effect can be expected by adopting this method. As a result, the influence of distortion generated by fastening the screw to the cylinder 11 during assembly is minimized, and the sliding resistance is reduced by ensuring the high roundness of the piston 12, thereby deteriorating fuel consumption. And the output drop is prevented.

This is because the first female screw portion 10b and the second female screw portion 10c provided on the bolt seat portion 10a when assembled by the first fastening bolt 18a and the second fastening bolt 18b are shown in FIG. This is because the first fastening bolt 18a and the second fastening bolt 18b are pulled. At this time, the bolt seat portion 10a itself is formed of a material having a necessary strength by being provided on the bore portion 10, so that it can withstand a fastening force from above and below and ensure a necessary surface pressure.
The first female screw portion 10b and the second female screw portion 10c provided on the bolt seat portion 10a need to be provided at positions where the upper and lower forces can be balanced when assembled, but in this embodiment, It is provided on the same axis and fulfills its function.
The bolt seat 10a is required to have a high sealing performance between the bore 10 and the cylinder head 16 and the crankcase 13 as described above when assembling the bore 10 to the engine. It is closed by the torque, and as a result, a large force is applied to the bolt seat 10a. Therefore, the strength that can withstand it is necessary.

However, as described above, a large force is applied to the bolt seat portion 10a by fastening, and the bolt seat portion 10a is edged to the bore portion 10, so that the bolt seat portion 10a is connected to the first fastening bolt 18a by the force of fastening. Alternatively, the second fastening bolt 18b is pulled up or down, and as a result, the strain generated by the pulling affects the bore portion 10 and deteriorates the shape accuracy of the bore portion 10 such as roundness. .
This is also shown from the analysis results. By being pulled by the first fastening bolt 18a or the second fastening bolt 18b, fourth-order distortion is generated with respect to one cylinder. It is known that the bore portion 10 is deformed.
Therefore, the distortion given to the bore part 10 by the bolt seat part 10a becomes a problem. In particular, if the bolt seat portion 10a is thick, the amount of deformation of the bolt seat portion 10a itself is reduced, but distortion at the joint between the bolt seat portion 10a and the bore portion 10 occurs to a degree that cannot be ignored.

In order to reduce the influence on the bore portion 10 by such distortion caused by the force applied to the bolt seat portion 10a, the mounting position of the bolt seat portion 10a is more than the sliding portion between the piston 12 and the inner surface of the bore portion 10. It is necessary to take it to a place as far away as possible. Further, it is necessary to keep away from the joint surface between the cylinder head 16 and the bore portion 10 in order to improve the confidentiality of the combustion chamber 20 formed inside.
Specifically, it is located away from the sliding portion of the piston ring and is far from the joint surface between the cylinder head 16 and the bore portion 10, that is, on the joint surface 10d side of the crankcase 13 and the bore portion 10. It is desirable that the bolt seat portion 10a is provided at the bore portion 10 at a height that does not cover the sliding surface of the piston ring.
Furthermore, in order to reduce the influence of distortion on the bore portion 10 as much as possible, it is desirable that the joint portion of the bolt seat portion 10a to the bore portion 10 is thinned to such an extent that a necessary surface pressure at the joint surface 10d is generated.
Further, the first female screw portion 10b and the second female screw portion 10c provided in the bolt seat portion 10a are provided coaxially, and the bolt seat portion 10a has a thickness of the first female screw portion 10b and the second female screw portion 10c. Since it is only thick enough to be provided, it can be expected that the first fastening bolt 18a and the second fastening bolt 18b pull each other and reduce distortion.

  Further, as in Patent Document 4, since the bore portion 10 is not provided with the outer wall portion 13b, the size of the bore portion 10 is minimized and the shape is simple. In the machining and plating processes, the bore 10 and the outer wall 13b can be performed with smaller equipment than the conventional one, and the weight of the bore 10 is reduced, which contributes to the improvement of workability. ing.

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.
Further, 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 require much strength can be made of an inexpensive material.

In this way, the parts that require strength, such as the bore part 10 and the bolt seat part 10a, are gathered to minimize the parts that require strength, and the crankcase part 13a and outer wall that do not require much strength originally. By forming the portion 13b integrally to form the crankcase 13, even if an expensive material is used for the bore portion 10 to improve performance, the crankcase 13 is manufactured using a relatively inexpensive material. Therefore, 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 portion 10 can be changed by the output of, there is a merit that it is possible to cope with engines of different outputs with the same design.

  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. If a complicatedly shaped water channel is provided, processing restrictions will occur and it will be costly to provide a sufficient water channel, but it is possible to secure the water channel by assembling the bolt part However, since the periphery of the first fastening bolt 18a can also be a water channel, the cooling effect can be enhanced without extra shielding.

  Since the first fastening bolt 18a is immersed in the cooling liquid, it may be necessary to take a rust prevention measure depending on the material of the first fastening bolt 18a and the nature of the cooling liquid. Although the rust prevention measures are taken, compared with the cost of manufacturing the machining holes and the cost of taking the rust prevention measures on the first fastening bolt 18a, the cost of making the machining holes improves quality, simplifies the machining, In consideration of the reduction of the lead time due to the reduction of the processing time and the like, considering the total, it is cheaper to take a rust prevention measure on the first fastening bolt 18a.

Further, the cylinder head 16 is assembled by fastening the first fastening bolt 18a to the first female screw portion 10b provided from the cylinder head 16 side to the bolt seat portion 10a with a metal gasket or the like interposed therebetween, and the crank cap 17 is The crankcase 13 is arranged so as to sandwich the crankcase 13 and is assembled by tightening the second fastening bolt 18b into the second female screw portion 10c provided from the crankcase 13 side of the bolt seat portion 10a.
Since the crankcase 13 is assembled so as to be sandwiched between the bore portion 10 and the crank cap 17 in this manner, it is always subjected to compressive stress in the assembled state. Easy to guarantee.
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.

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. The cylinder head 16 is fastened to the first female screw portion 10b formed in the bore portion 10 by the first fastening bolt 18a, and the second fastening bolt is attached to the second female screw portion 10c formed in the bore portion 10. In 18b, the crank cap 17 is fastened with the crankcase portion interposed therebetween, and an outer wall portion 13b surrounding the bore portion 10 is integrated with the crankcase portion 13a when the bore portion is assembled with the crankcase portion. The first female screw portion 10b and the second female screw portion are added to the bore portion 10 which requires strength. A portion of excessive quality by consolidating the crank cap 17 and the outer wall portion 13b, which do not require strength, together with the crank cap 17 and fastening them to the bore portion 10 with the second fastening bolts 18b. As a result, it is possible to reduce the cost as much as possible and to reduce the cost. Moreover, since the part which requires intensity | strength is collected by the bore part 10, it can be made small rather than making it integrally with another part, and the workability of the bore part 10 improves.

(2) In the block division structure described in (1), a bolt seat portion 10a is provided on the side of the bore portion 10 in contact with the crankcase portion 13a, and the first female screw portion 10b is provided on the bolt seat portion 10a. Since the second female screw portion 10c is provided on the side facing the first female screw portion 10b, the bolt seat portion 10a rimmed on the strong bore portion 10 is threaded. The cylinder head 16 can be fastened with a required fastening force, requires a high sealing performance, and prevents the sliding portion between the piston 12 and the inner diameter of the cylinder 11 from being affected by distortion as much as possible. By disposing the screw portion far from the joint surface of the bore portion 10, there is an excellent effect of minimizing the influence of strain on the joint surface and the sliding portion with the bore portion 10.
(3) In the block division structure described in (1) or (2), the crankcase portion 13a, the outer wall portion 13b formed in the crankcase portion 13a, the bore portion 10, and the cylinder head 16 are surrounded. Since the engine coolant is filled in the space, it is not necessary to provide a bolt hole for the first fastening bolt 18a, and the shapes of the crankcase portion 13a, the outer wall portion 13b, and the bore portion 10 are simple. Therefore, there is an excellent effect that the processing cost can be reduced. It is also possible to make a wide space for the coolant to pass.

In addition, this invention is not limited to the said embodiment, A various change is possible in the range which does not deviate from the meaning.
For example, in this embodiment, an aluminum alloy for die casting such as ADC 12 is used for the bore portion 10, but it is not particularly limited to this material. For example, an aluminum casting by forging or a forged product may be used. Not limited to this, cast iron or the like may be used. 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.
Moreover, although the 1st internal thread part 10b and the 2nd internal thread part 10c provided in the bolt seat part 10a are provided centering on the same axis | shaft, the 1st fastening bolt 18a and the 2nd fastening bolt 18b Since it is only necessary to balance the pulling force, there is no need to have the center of the screw portion on the same axis.

1 is a cross-sectional view of an engine in the present embodiment. (A) The part figure of the bore part in a present Example is shown with the perspective view. (B) The parts figure of the crankcase in a present Example is shown with the perspective view. (A) The schematic diagram of the state in which the 1st fastening bolt and the 2nd fastening bolt were fastened by the bore part in a present Example is shown. (B) The cross section of the partial detailed view of (a) in the present embodiment is shown. The perspective sectional view in the state where a bore part, a crankcase, a cylinder head, and a crank cap were assembled in this example is shown. The perspective sectional view cut | disconnected in the cross section different from FIG. 4 in a present Example is shown. It is sectional drawing in the state in which the bore part was assembled | attached to the crankcase in a present Example. 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.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Bore part 10a Bolt seat part 10b 1st internal thread part 10c 2nd internal thread part 11 Cylinder 12 Piston 13 Crankcase 13a Crankcase part 13b Outer wall part 14 Connecting rod 15 Crankshaft 16 Cylinder head 17 Crank cap 18a 1st fastening bolt 18b Second fastening bolt 19 Water channel 20 Combustion chamber

Claims (3)

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 cylinder head is fastened with a first fastening bolt to the first female screw part formed in the bore part,
The crank cap is fastened to the second female screw portion formed in the bore portion by sandwiching the crank case portion with a second fastening bolt,
When the bore portion is assembled with the crankcase portion, an outer wall that surrounds the bore portion is formed integrally with the crankcase portion ,
A mounting portion is provided on the side of the bore portion that contacts the crankcase portion so as to protrude from the side surface of the bore portion,
Wherein the mounting portion, the first female screw portion is provided, wherein the second female screw portion is provided on the first side facing the female thread block division structure, characterized in Rukoto. In the block division structure according to claim 1 ,
The block division structure characterized in that the mounting portion is provided on a side surface of the bore portion by a plate-like member . In the block division structure according to claim 2 ,
A block division structure characterized in that engine coolant is filled in a space surrounded by the crankcase portion, an outer wall formed in the crankcase portion, the bore portion, and the cylinder head.

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