Insert used for connecting main bearing seat and top surface bolt lug in aluminum alloy cylinder body

Abstract

The invention discloses an insert used for connecting a main bearing seat and a top surface bolt lug in an aluminum alloy air cylinder body, and belongs to the field of diesel engine cylinder bodies, the insert is cast in the aluminum alloy air cylinder body and is connected with the aluminum alloy air cylinder body through casting, and the whole insert is composed of a lower insert body, an upper insert body and a connecting rib. The lower insert is used for replacing a main bearing seat of a cylinder body to be in contact with a main shaft diameter of a crankshaft, the upper insert is connected with the top surface of the cylinder body, and the lower insert and the upper insert are connected through a connecting rib. The upper bolt lug and the lower bolt lug are communicated through the connecting rib, so that the stress of the upper bolt lug and the lower bolt lug in opposite directions mainly acts on the connecting rib, and compared with a threaded connection pair which directly acts on the aluminum alloy cylinder body, the bearable tension limit is improved; compared with an air cylinder body with upper and lower independent inserts, the upper and lower parts of the inserts bear outward pulling force, external force can be converted into internal force of the inserts, mutual pulling is formed, the risk that the inserts fall off is reduced, and the bonding strength is improved.

Description

Technical Field

[0001] The invention relates to the field of diesel engine cylinder blocks, in particular to an insert in an aluminum alloy cylinder block, and in particular to an insert in the aluminum alloy cylinder block for connecting a main bearing seat and a top surface bolt saddle. Background Art

[0002] Currently, the design optimization of diesel engines mainly tends to be high power, light weight and clean.

[0003] The diesel engine cylinder block is the skeleton of the engine and the heaviest component in the diesel engine. Its design is becoming more and more compact. At present, the compactness of the structure has reached its limit. There is little space to achieve lightweight structure. It is urgent to achieve lightweight by replacing the materials of diesel engine parts.

[0004] Aluminum alloy materials are light in weight and have fast heat dissipation, which meets the requirements of diesel engine cylinder blocks. They can effectively reduce the overall weight of diesel engines, improve the power-to-weight ratio of diesel engines, and reduce fuel consumption.

[0005] Cylinder blocks made of aluminum alloy materials are currently widely used in the field of gasoline engines. A small number of diesel engine manufacturers have also tried to invest in the research and development of aluminum alloy cylinder blocks for diesel engines. However, due to the large size, poor material strength, large temperature changes, easy deformation, high friction coefficient and corrosion resistance of aluminum alloy cylinder blocks, the use of all-aluminum alloy cylinder blocks is difficult to fully meet the requirements of high explosion pressure and high operating temperature in the diesel engine cylinder. Therefore, there are generally problems such as low power output, low degree of strengthening and short life.

[0006] The cylinder block main bearing seat is an important structure of the engine cylinder block that supports the crankshaft. It needs to bear the load transmitted by the explosion pressure in the cylinder through the crank-connecting rod mechanism, and at the same time, it needs to meet the lubrication conditions necessary for the rotation of the crankshaft.

[0007] One of the current development trends of engines is small size and high power density, which leads to a continuous increase in the pressure inside the engine cylinder, especially for diesel engines.

[0008] In order to ensure the smooth combustion in the cylinder, the sealing of the cylinder block and cylinder head must be ensured during the engine installation, so high requirements are placed on the tightening process of the cylinder head bolts and the bolt pre-tightening force after installation. Because the explosion pressure of the gasoline engine during operation is lower than that of the diesel engine, the angle required for bolt tightening is about half of that of the diesel engine. In the load limit test of aluminum alloy threads, it was found that the probability of aluminum threads failing when subjected to the diesel engine cylinder head bolt tightening process is relatively high.

[0009] The cylinder block main bearing seat is an important structure of the engine cylinder block that supports the crankshaft. It needs to bear the load transmitted by the explosion pressure in the cylinder through the crank-connecting rod mechanism, and at the same time, it needs to meet the lubrication conditions necessary for the rotation of the crankshaft. In order to ensure the stability of the engine crank-connecting rod mechanism and reduce the leakage of the main bearing seat lubricating oil, there are also high requirements for the tightening process of the main bearing seat bolts and the bolt preload after installation.

[0010] In addition, compared with the internal threads on cast iron cylinder blocks, the life of the internal threads of aluminum alloy cylinder blocks is reduced by half. Currently, the number of repeated tightening allowed for the internal threads of aluminum alloy cylinder blocks is generally only 3 times, which also includes the necessary tightening when using simulated cylinder head processing.

[0011] In the existing technical solutions, the cylinder block is generally formed in one piece with aluminum alloy materials when manufacturing. Some products will insert cast iron cylinder liners in the cylinder bores. At the same time, a small number of products try to insert U-shaped cast iron inserts in the main bearing seat of the aluminum alloy cylinder block, so that the contact surface between the cylinder block and the crankshaft is cast iron material. For example:

[0012] CN201301758Y discloses an engine crankcase lower case insert structure, which involves using a relatively high-strength material to manufacture the main bearing seat surface and the bolt bracket to bear the load brought by the crankshaft and the bolt, and at the same time includes an aluminum alloy containing hole to prevent the insert from moving up and down; however, in actual work, the insert has the risk of being separated from the cylinder body due to the force direction thereof tending to pull the insert out of the cylinder body, or fatigue cracks are generated at the joint of the aluminum alloy and the insert, which eventually leads to the failure of the cylinder body. The main problem of this scheme is that the force direction design of the insert is unreasonable, and the force area originally bearing the crankshaft and bolt force of the aluminum alloy is only transferred to the area where the insert and the aluminum alloy cylinder body are combined, which increases the force area to a certain extent, but fails to balance the force in all directions of the cylinder body, so the improvement of the reliability of the multi-cylinder body is limited.

[0013] In the face of the above-mentioned problems in the development of aluminum alloy cylinder blocks for diesel engines, adding main bearing seats and threaded hole inserts, optimizing the force flow transmission inside the cylinder block, and guiding the force transmission of various parts of the cylinder block as much as possible to make it as balanced as possible are effective methods to improve the strength and life of the cylinder block. Therefore, it is necessary to design an insert that is cast in the aluminum alloy cylinder block and connected by upper and lower bolts. Summary of the invention

[0014] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide an insert in an aluminum alloy cylinder body for connecting the main bearing seat and the top bolt bracket to solve technical problems such as insufficient strength of the main bearing seat and insufficient thread strength of the aluminum alloy threaded hole.

[0015] The technical solution of the present invention is:

[0016] An insert in an aluminum alloy cylinder body for connecting a main bearing seat and a top surface bolt strap, the insert is cast in the aluminum alloy cylinder body and connected to the aluminum alloy cylinder body by casting, the insert as a whole is composed of a lower insert 1, an upper insert 2 and a connecting rib 3; the lower insert 1 is used to replace the cylinder body main bearing seat as a contact with the crankshaft main shaft diameter; the upper insert 2 is connected to the top surface of the cylinder body; the lower insert 1 and the upper insert 2 are connected by the connecting rib 3.

[0017] Furthermore, the lower insert 1 is composed of a main bearing seat body 12, a main bearing cover positioning baffle 13, a lower insert shoulder 14, a main bearing seat bolt bracket 15, an aluminum inclusion process hole 16, a main bearing seat threaded hole 17 and an oil channel hole 18.

[0018] Furthermore, the main bearing seat bearing surface 11 is a semicircular surface, which is located below the lower insert 1 and is used to replace the cylinder main bearing seat as the contact with the crankshaft main shaft diameter, and plays the role of bearing load and providing a lubrication platform; the main bearing seat body 12 is offset by a certain thickness according to the side contour line of the main bearing seat bearing surface 11.

[0019] Furthermore, two raised main bearing cover positioning baffles 13 are symmetrically distributed between the two waists of the main bearing seat body 12, which are used for positioning when installing the main bearing cover, and at the same time form an interference fit with the side of the main bearing cover to ensure that the main bearing cover is not prone to slip during assembly and operation; the bearing surface 11 of the main bearing seat and the contact surface between the main bearing seat and the main bearing cover need to be further fine-machined after the insert is cast into the aluminum alloy cylinder block, so a processing allowance should be left when designing the insert.

[0020] Furthermore, lower insert shoulders 14 are symmetrically provided on the left and right shoulders of the main bearing seat body 12, which are used to accommodate the main bearing seat bolt bracket 15, the aluminum inclusion process hole 16, the main bearing seat threaded hole 17 and the oil channel hole 18, and at the same time play a role in enhancing the overall rigidity of the lower insert. Its shape is obtained based on the internal shape of the cylinder body and the various structures that need to be included, and its edges need to be as smooth as possible.

[0021] Furthermore, the main bearing seat bolt bracket 15 is located above the main bearing seat body 12 and is contained in the lower insert shoulder 14, which is used to provide a certain wall thickness for the main bearing seat internal threaded hole 17 and ensure the reliability of the thread.

[0022] Furthermore, the aluminum inclusion process hole 16 is located where the left and right lower insert shoulders 14 are close to each other.

[0023] Furthermore, a main bearing seat threaded hole 17 is provided inside the main bearing seat body 12; the insert is connected to the aluminum alloy cylinder block by casting and can be regarded as an integral whole. When the insert is manufactured, there is no main bearing seat threaded hole 17 and thread, only the insert has a bolt bracket 15 reserved for processing the threaded hole on the surface. After the insert is cast into the aluminum alloy cylinder block, the threaded hole and thread are processed. Processing the thread on ductile iron can improve the strength and life of the thread compared to directly starting the thread on the aluminum alloy cylinder block.

[0024] Furthermore, an oil passage 18 leading to the main bearing seat is further provided inside the main bearing seat body 12. When designing the connecting rib 3, the direction of the rib is arranged along the path of the lubricating oil passage to reduce the simultaneous action of the tool on the bimetallic surface during processing, and the occurrence of tool jumping and other behaviors that affect the processing accuracy. The oil passage 18 should be fully contained in the insert as much as possible, and the oil passage opening should be made perpendicular to the center line of the oil passage as much as possible to facilitate tool processing; at the same time, the connecting rib containing the oil passage is appropriately thickened to ensure that after the oil passage is opened, there is still sufficient wall thickness to ensure the strength of the connecting rib.

[0025] Furthermore, the upper insert 2 is composed of a bolt bracket 21 on the top surface of the cylinder block and an internal threaded hole 22 for connecting to the cylinder head. The upper surface of the upper insert 2 is connected to the top surface of the cylinder block, and the position of the internal threaded hole 22 coincides with the position of the original cylinder block threaded hole. The threads processed after the insert is cast into the interior of the aluminum alloy cylinder block are all on the insert, so as to improve the yield of the processed threads and at the same time improve the strength and life of the threads.

[0026] Furthermore, the insert is made of ductile iron, steel, grey cast iron or other materials.

[0027] The lower insert 1 and the upper insert 2 of the present invention are connected by means of connecting ribs 3, and the connecting ribs 3 connect the bolt bracket 21 on the top surface of the cylinder block with the end of the bolt bracket 15 of the lower insert. In this way, the tension of the cylinder block-cylinder head bolt on the cylinder block and the tension of the cylinder block-main bearing cap bolt on the cylinder block are directly transmitted through the connecting ribs 3 to reduce the stress concentration formed by the bolt preload acting on the aluminum alloy part of the cylinder block. If the center lines of the upper and lower bolt brackets are collinear, the connecting ribs are arranged along the center lines; if the center lines of the upper and lower bolt brackets are not collinear, the ends of the upper and lower bolt brackets are connected together.

[0028] Compared with the prior art, the beneficial effects of the present invention include:

[0029] 1) The elastic modulus of cast iron material is higher than that of aluminum alloy material, and the linear expansion coefficient is lower than that of aluminum alloy material. The temperature at the main bearing seat is generally between 100℃ and 200℃. At this temperature, the mechanical properties of ductile iron or steel are more stable. Compared with aluminum alloy material, it is more adaptable to the high explosion pressure and high temperature working environment of high-strength diesel engine. When used under normal working conditions, it produces smaller elastic deformation, is not prone to plastic deformation and cracking, and improves the overall stiffness of the main bearing seat of the cylinder block;

[0030] 2) In the existing aluminum alloy cylinder engine, especially the diesel engine, in order to ensure the smooth combustion in the cylinder, the sealing of the cylinder block and the cylinder head must be ensured when the engine is installed, so high requirements are put forward for the tightening process of the cylinder head bolts and the bolt pre-tightening force after the installation is completed; at the same time, in order to ensure the stability of the operation of the engine crank-connecting rod mechanism and reduce the leakage of the lubricating oil of the main bearing seat, high requirements are also placed on the tightening process of the main bearing seat bolts and the bolt pre-tightening force after the installation is completed. In the present invention, the force direction of the internal thread of the upper part of the cylinder block is upward, and the force direction of the internal thread of the main bearing seat is downward. The upper and lower brackets are connected by connecting ribs, so that the forces of the upper and lower bolt brackets in opposite directions mainly act on the connecting ribs. Compared with the threaded connection pair directly acting on the aluminum alloy cylinder block, the tensile force limit that can be tolerated is improved; compared with the cylinder body with upper and lower independent inserts, the inserts are subjected to outward pulling force at the top and bottom, which can convert the external force into the internal force of the inserts, forming mutual pulling, reducing the risk of the inserts falling off, and improving the bonding strength;

[0031] 3) The thread of the threaded hole directly processed on the aluminum alloy cylinder body has low strength and short life. The thread is used in the step of closing the cover during the cylinder body processing, which consumes the life of the thread. Therefore, the number of repeated assembly times of the finished aluminum alloy cylinder body is very limited. The insert of the present invention has better material strength and better processing performance, and the thread processed on the insert has higher yield rate and strength, and longer service life. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a schematic diagram of the appearance structure of the insert in Example 1 of the present invention.

[0033] Figure 2 It is a front cross-sectional view of the insert according to Example 1 of the present invention.

[0034] Figure 3 This is a schematic diagram of the front view of the installation position of the insert in the aluminum alloy cylinder body according to Example 1 of the present invention.

[0035] Figure 4 This is a schematic diagram from an axonometric perspective of the installation position of the insert in the aluminum alloy cylinder body according to Example 1 of the present invention.

[0036] In the figure:

[0037] 1-lower insert, 11-main bearing seat bearing surface, 12-main bearing seat body, 13-main bearing cover positioning baffle, 14-lower insert shoulder, 15-main bearing seat bolt bracket, 16-aluminum inclusion process hole, 17-main bearing seat internal thread hole, 18-oil channel;

[0038] 2-upper insert, 21-bolt bracket on top of cylinder block, 22-internal threaded hole;

[0039] 3-Connecting ribs. DETAILED DESCRIPTION

[0040] The technical solution of the present invention is described in detail below with reference to the accompanying drawings.

[0041] like Figure 1 to Figure 3 As shown, an insert in an aluminum alloy cylinder body is used to connect the main bearing seat and the top bolt bracket. The insert is cast in the aluminum alloy cylinder body and connected to the aluminum alloy cylinder body by casting. The insert is generally composed of a lower insert 1, an upper insert 2 and a connecting rib 3 connecting the lower insert 1 and the upper insert 2.

[0042] The lower insert 1 is composed of a main bearing seat body 12, a main bearing cover positioning baffle 13, a lower insert shoulder 14, a main bearing seat bolt bracket 15, an aluminum inclusion process hole 16, a main bearing seat threaded hole 17 and an oil passage 18.

[0043] Below the lower insert 1 is a semicircular main bearing seat bearing surface 11, the main function of which is to replace the cylinder main bearing seat as a contact with the crankshaft main shaft diameter, bear the load and provide a lubrication platform; according to the side contour line of the main bearing seat bearing surface 11, a certain thickness is offset to obtain a main bearing seat body 12, and the offset thickness is mainly determined by the load size that the main bearing seat needs to bear; two raised main bearing cover positioning baffles 13 are symmetrically distributed between the two waists of the main bearing seat body 12, such as Figure 3 As shown, the main bearing cap positioning baffle 13 is located at the main bearing seat baffle position below the original cylinder body, and contacts the main bearing cap on the left and right to form an interference fit. Its main function is to provide positioning when installing the main bearing cap. At the same time, the interference fit formed with the side of the main bearing cap ensures that the main bearing cap is not easy to slip during assembly and operation. The bearing surface 11 of the main bearing seat and the surface where the main bearing seat contacts the main bearing cap need to be further fine-machined after the insert is cast into the aluminum alloy cylinder body, so a machining allowance should be left when designing the insert.

[0044] The left and right shoulders of the main bearing seat body 12 are symmetrically provided with lower insert shoulders 14, whose main function is to accommodate the main bearing seat bolt bracket 15, the aluminum inclusion process hole 16, the main bearing seat threaded hole 17 and the oil channel 18, and at the same time play a role in enhancing the overall rigidity of the lower insert. Its shape is mainly obtained by combining the internal shape of the cylinder body and the various structures that need to be included, and its edges need to be as smooth as possible.

[0045] The main bearing seat bolt bracket 15 is located above the main bearing seat body 12 and is contained in the lower insert shoulder 14. Its function is to provide a certain wall thickness for the main bearing seat internal threaded hole 17 to ensure the reliability of the thread.

[0046] The aluminum inclusion process hole 16 is located where the left and right lower insert shoulders 14 are close to each other. There is no specific requirement for its position, as long as it avoids areas with special functions. Its main functions are: 1. reducing the weight of the insert to improve the lightweight of the aluminum alloy cylinder body; 2. The hole allows the molten liquid aluminum alloy to pass through and solidify during the casting of the cylinder body, so that the aluminum alloy cylinder body and the insert are intertwined after casting, thereby improving the bonding strength between the aluminum alloy cylinder body and the insert; because the hole is the aluminum-iron bonding surface during the casting process, in order to solve the problem that the different shrinkage rates of the aluminum alloy material and the ductile iron material are prone to form gaps, which affects the bonding strength, the aluminum inclusion process hole 16 should be as smooth as possible.

[0047] A main bearing seat threaded hole 17 is provided inside the main bearing seat body 12; the insert is connected to the aluminum alloy cylinder block by casting and can be regarded as an integral whole. When the insert is manufactured, there is no main bearing seat threaded hole 17 and thread, only the main bearing seat bolt bracket 15 with threaded holes reserved for machining is provided on the appearance of the insert. After the insert is cast into the aluminum alloy cylinder block, the threaded holes and threads are machined out. Machining threads on ductile iron can improve the strength and life of the threads compared to directly machining threads on the aluminum alloy cylinder block.

[0048] An oil passage 18 leading to the main bearing seat is also provided inside the main bearing seat body 12. When designing the connecting rib 3, the direction of the rib is arranged along the path of the lubricating oil passage. Since the processing of the oil passage needs to be carried out after the insert is cast into the aluminum alloy cylinder block, in order to reduce the simultaneous action of the tool on the bimetallic surface during the processing, the tool jump and other behaviors that affect the processing accuracy, the oil passage 18 should be included in the insert as much as possible. If it is really difficult to include it in the insert, the oil passage opening should be made perpendicular to the center line of the oil passage as much as possible to facilitate tool processing; at the same time, the connecting rib containing the oil passage is appropriately thickened to ensure that after the oil passage is opened, there is still sufficient wall thickness to ensure the strength of the connecting rib.

[0049] like Figure 3As shown, the upper insert 2 is composed of a bolt bracket 21 on the top surface of the cylinder block and an internal threaded hole 22 for connecting the cylinder head. The upper surface of the upper insert 2 is connected to the top surface of the cylinder block, and the position of the internal threaded hole 22 coincides with the position of the original cylinder block threaded hole. Its main function is to ensure that after the insert is cast into the interior of the aluminum alloy cylinder block, all the threads processed are on the insert, so as to improve the yield of the processed threads and improve the strength and life of the threads. In order to ensure that the bolt bracket has sufficient strength after drilling and tapping the threaded holes, when designing the bolt bracket, a certain thickness of the wall thickness needs to be increased on the basis of the diameter of the original threaded hole. The shape can be cylindrical, or in the shape of the original threaded hole.

[0050] The lower insert 1 and the upper insert 2 are connected by means of connecting ribs 3, and the connecting ribs 3 connect the cylinder top surface bolt bracket 21 with the end of the main bearing seat bolt bracket 15. In this way, the tension of the cylinder block-cylinder head bolt on the cylinder block and the tension of the cylinder block-main bearing cap bolt on the cylinder block are directly transmitted through the connecting ribs 3 to reduce the stress concentration formed by the bolt preload acting on the aluminum alloy part of the cylinder block. If the center lines of the upper and lower bolt brackets are collinear, the connecting ribs are arranged along the center lines; if the center lines of the upper and lower bolt brackets are not collinear, the ends of the upper and lower bolt brackets are connected together.

[0051] When the insert is initially manufactured, the surface of the insert is cast with spike-like casting protrusions, or before being cast into the cylinder block, a rough surface is processed by sandblasting, tool roughening and other processes to improve the bonding strength of the insert cast into the aluminum alloy cylinder block.

[0052] It should be noted that, except for the main bearing seat threaded hole 17, the upper insert internal threaded hole 22 and the internal oil passage 18, all other parts of the insert have been manufactured before the cylinder block is cast.

[0053] like Figure 3 and Figure 4 As shown, during casting, attention should be paid to setting up a structure for placing and accurately positioning the insert position, so that the lower insert 1 is located at the position of the original cylinder main bearing seat. After machining, the surface of the main bearing seat body 12 that contacts the crankshaft is completely the main bearing seat surface 11 of the insert, so that the top surface of the upper insert 2 is located on the top surface of the cylinder, and the center point of each upper insert 2 is located on the center of the cylinder threaded hole; after machining, the top surface of the upper insert 2 is exposed on the top surface of the cylinder; it is necessary to ensure that the insert has a certain position accuracy when cast into the cylinder to ensure that the wall thickness of the cylinder bolt hole can meet the standard when machining the cylinder.

Claims

1. An insert in an aluminum alloy cylinder body for connecting a main bearing seat and a top bolt bracket, characterized in that: The insert is cast in an aluminum alloy cylinder body and connected to the aluminum alloy cylinder body by casting. The insert is generally composed of a lower insert (1), an upper insert (2) and a connecting rib (3). The lower insert (1) is used to replace the cylinder body main bearing seat as a contact with the crankshaft main shaft diameter, and the upper insert (2) is connected to the top surface of the cylinder body. The lower insert (1) and the upper insert (2) are connected by the connecting rib (3).

2. The insert according to claim 1, characterized in that: The lower insert (1) comprises a main bearing seat body (12), a main bearing cover positioning baffle (13), a lower insert shoulder (14), a main bearing seat bolt bracket (15), an aluminum inclusion process hole (16) and a main bearing seat threaded hole (17); The main bearing seat bearing surface (11) is a semicircular surface, which is located below the lower insert (1) and is used to replace the cylinder main bearing seat to contact the crankshaft main shaft diameter, and play the role of bearing load and providing a lubrication platform; the main bearing seat body (12) is obtained by offsetting a certain thickness according to the side contour line of the main bearing seat bearing surface (11); Two protruding main bearing cover positioning baffles (13) are symmetrically distributed between the two waists of the main bearing seat body (12) and are located at the main bearing seat baffle position below the original cylinder body, and are used for positioning when installing the main bearing cover, and at the same time form an interference fit with the side of the main bearing cover to ensure that the main bearing cover is not prone to slipping during assembly and operation; The lower insert shoulders (14) are symmetrically arranged on the left and right shoulders of the main bearing seat body (12) for accommodating the main bearing seat bolt bracket (15) and the main bearing seat threaded hole (17), and at the same time play a role in enhancing the overall rigidity of the lower insert; The main bearing seat bolt bracket (15) is located above the main bearing seat body (12) and is contained in the lower insert shoulder (14) and is used to provide a certain wall thickness for the main bearing seat internal thread hole (17) to ensure the reliability of the thread; A main bearing seat threaded hole (17) is provided inside the main bearing seat body (12).

3. The insert according to claim 2, characterized in that: The upper insert (2) is composed of a bolt bracket (21) on the top surface of the cylinder body and an internal threaded hole (22) for connecting to the cylinder head. The upper surface of the upper insert (2) is connected to the top surface of the cylinder body. The position of the internal threaded hole (22) coincides with the position of the original cylinder body threaded hole. After the insert is cast into the interior of the aluminum alloy cylinder body, all the threads processed are on the insert, so as to improve the yield rate of the processed threads and at the same time improve the strength and life of the threads.

4. The insert according to claim 3, characterized in that: The connecting rib (3) connects the cylinder block top surface bolt bracket (21) and the end of the lower insert bolt bracket (15) together, and is used to directly transmit the tension of the cylinder block-cylinder head bolt on the cylinder block and the tension of the cylinder block-main bearing cap bolt on the cylinder block through the connecting rib (3), so as to reduce the stress concentration formed by the bolt pre-tightening force acting on the aluminum alloy part of the cylinder block.

5. The insert according to claim 4, characterized in that: If the center lines of the cylinder block top surface bolt bracket (21) and the lower block bolt bracket (15) are collinear, the connecting rib (3) is arranged along the center line; if the center lines of the cylinder block top surface bolt bracket (21) and the lower block bolt bracket (15) are not collinear, the ends of the cylinder block top surface bolt bracket (21) and the lower block bolt bracket (15) are connected together.

6. The insert according to claim 2, characterized in that: It also includes an aluminum inclusion process hole (16) located near the left and right lower insert shoulders (14).

7. The insert according to claim 2, characterized in that: It also includes an oil passage (18) leading to the main bearing seat and arranged inside the main bearing seat body (12).

8. The insert according to claim 2, characterized in that: The shape of the lower insert shoulder (14) is obtained by integrating the internal shape of the cylinder body and the structure of the main bearing seat bolt bracket (15) and the main bearing seat threaded hole (17) required to be included, and its edge has a smooth transition.

9. The insert according to claim 1, characterized in that: The bearing surface (11) of the main bearing seat and the contact surface between the main bearing seat and the main bearing cover are further fine-machined after the insert is cast into the aluminum alloy cylinder body, and a machining allowance is reserved when designing the insert.

10. The insert according to any one of claims 1 to 9, characterized in that: The insert is made of ductile iron, steel or grey cast iron.

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