A method for controlling pre-deformation of the main shaft holes of an engine lower cylinder block and an engine

Abstract

The present application relates to a method for controlling pre-deformation of the main shaft holes of an engine lower cylinder block and an engine, which comprises the following steps: tightening the upper cylinder block and the main bearing seat of the lower cylinder block with connecting bolts according to a tightening torque M and a first tightening rotation angle σ, and completing rough machining of the main shaft holes of the lower cylinder block; loosening the connecting bolts, assembling the main shaft, and tightening the upper cylinder block and the main bearing seat of the lower cylinder block with the connecting bolts according to the tightening torque M and a second tightening rotation angle β; wherein, based on the first tightening rotation angle σ and a pre-deformation rotation angle γ, the second tightening rotation angle β is obtained. The present application can solve the problem in the related art that when the explosion pressure generated by the main shaft holes of the lower cylinder block acts on the crankshaft during the operation of the engine, large elastic deformation will occur, and this elastic deformation will cause excessive local clearance between the main shaft holes of the lower cylinder block and the crankshaft journal, resulting in out-of-tolerance neck runout of the main shaft holes of the lower cylinder block, causing damage such as vibration noise and serious bearing shell wear, and affecting the normal operation of the engine.

Description

Technical Field

[0001] The present application relates to the technical field of automotive engines, and particularly relates to a method for controlling pre-deformation of the main bearing holes of an engine lower cylinder block and an engine. Background Art

[0002] At present, during the lightweighting process of passenger vehicle engines, the upper cylinder block material is mostly aluminum alloy material, while the lower cylinder block is simplified to a single steel material main bearing seat (similar to the lower cylinder block), or a main bearing seat of steel material is cast in an integral aluminum alloy lower cylinder block frame to bear the force acting on the crankshaft journal during the power stroke of the engine. The advantage of this structure is that a steel material with higher elastic modulus and mechanical properties is still used as the main bearing hole seat in the direction of the maximum force of the main bearing hole, effectively suppressing and reducing the deformation amount of the main bearing hole.

[0003] For commercial vehicle engines, due to higher power and explosion pressure requirements, the upper cylinder block still maintains cast iron material, and only a lightweighting scheme for the lower cylinder block can be adopted in the engine weight reduction plan.

[0004] When a commercial vehicle engine adopts a cast iron upper cylinder block and achieves weight reduction by using an aluminum alloy lower cylinder block, the following problem points exist at the main bearing holes of the integral frame-type aluminum alloy lower cylinder block with main bearing seats:

[0005] 1) After the lower cylinder block adopts aluminum alloy material, its elastic modulus is only 71.5 GPa, about 1 / 3 of that of cast iron material. Under the action of the same explosion pressure, the deformation amount of its main bearing hole in the direction of the maximum force is much larger than that of the original cast iron material, resulting in an out-of-tolerance main shaft runout, causing vibration, poor oil film lubrication, and in severe cases, local wear of the main shaft bearing and bearing seizure.

[0006] 2) After adopting an aluminum alloy lower cylinder block, there is no theoretical calculation control method for the deformation amount of its main bearing holes, and there is a lack of actual control process measures, so mass stable production and manufacturing cannot be achieved. Summary of the Invention

[0007] The embodiments of the present application provide a method for controlling pre-deformation of the main bearing holes of an engine lower cylinder block and an engine, so as to solve the problem in the related art that when the explosion pressure generated during the operation of the engine acts on the crankshaft, the main bearing holes of the lower cylinder block will have large elastic deformation, and this elastic deformation will cause too large a local gap between the main bearing holes of the lower cylinder block and the crankshaft journal, resulting in an out-of-tolerance runout of the main bearing hole neck of the lower cylinder block, causing damage such as vibration noise and severe bearing seizure, and affecting the normal operation of the engine.

[0008] In a first aspect, a method for controlling pre-deformation of the main bearing holes of an engine lower cylinder block is provided, which includes the following steps:

[0009] Tighten the main bearing seat of the upper cylinder block and the lower cylinder block with the connecting bolts according to the tightening torque M and the first tightening rotation angle σ to complete the rough machining of the main shaft hole of the lower cylinder block;

[0010] Loosen the connecting bolts, assemble the main shaft, and tighten the main bearing seat of the upper cylinder block and the lower cylinder block with the connecting bolts according to the tightening torque M and the second tightening rotation angle β;

[0011] Wherein, based on the first tightening rotation angle σ and the pre-deformation rotation angle γ, the second tightening rotation angle β is obtained.

[0012] In some embodiments, the second tightening rotation angle β is the sum of the first tightening rotation angle σ and the pre-deformation rotation angle γ.

[0013] In some embodiments, the method further includes the step of obtaining the pre-deformation rotation angle γ.

[0014] In some embodiments, obtaining the pre-deformation rotation angle γ specifically includes:

[0015] Based on the maximum deformation amount Ly of the main shaft hole of the lower cylinder block in the direction of the explosion pressure transmitted by the crankshaft, the radius R of the main shaft hole of the lower cylinder block, and the height Hs of the main bearing seat of the lower cylinder block, obtain the pressing-down amount Lm of the clamping surface of the connecting bolts of the main bearing seat of the lower cylinder block;

[0016] Based on the mapping relationship between Lm, the pre-tightening force Fm of the connecting bolts and Lm, and the mapping relationship between Fm and the rotation angle of the connecting bolts, obtain the pre-deformation reference rotation angle δ;

[0017] Based on the pre-deformation reference rotation angle δ, obtain the pre-deformation rotation angle γ.

[0018] In some embodiments, based on the pre-deformation reference rotation angle δ, obtaining the pre-deformation rotation angle γ specifically includes:

[0019] Round down the pre-deformation reference rotation angle δ to obtain the pre-deformation rotation angle γ.

[0020] In some embodiments, based on the pre-deformation reference rotation angle δ, obtaining the pre-deformation rotation angle γ specifically includes:

[0021] Subtract the correction value from the pre-deformation reference rotation angle δ to obtain the pre-deformation rotation angle γ.

[0022] In some embodiments, after completing the rough machining of the main shaft hole of the lower cylinder block and before loosening the connecting bolts and assembling the main shaft, the method further includes:

[0023] Loosen the connecting bolts and tighten the main bearing seat of the upper cylinder block and the lower cylinder block with the connecting bolts again according to the tightening torque M and the first tightening rotation angle σ to complete the finish machining of the main shaft hole of the lower cylinder block.

[0024] In some embodiments, the lower cylinder block is made of cast iron material.

[0025] In some embodiments, the lower cylinder block is made of aluminum alloy material.

[0026] In a second aspect, an engine is provided, which includes an upper cylinder block and a main bearing seat of the lower cylinder block, and the upper cylinder block and the main bearing seat of the lower cylinder block are connected by connecting bolts. The connecting bolts have a tightening torque M and a second tightening rotation angle β. Among them, based on the first tightening rotation angle σ and the pre-deformation rotation angle γ, the second tightening rotation angle β is obtained.

[0027] The beneficial effects brought by the technical solutions provided in this application include:

[0028] The embodiments of this application provide a method and an engine for controlling the pre-deformation of the main shaft hole of the lower cylinder block of an engine. The cylinder block of the engine is assembled by the main bearing seat of the lower cylinder block and the upper cylinder block through connecting bolts. The main shaft hole of the cylinder block is divided into two parts, namely the main shaft hole of the upper cylinder block and the main shaft hole of the lower cylinder block. After the upper cylinder block and the main bearing seat of the lower cylinder block are installed, they are butted to form the main shaft hole. Generally, the deformation of the main shaft hole of the engine's lower cylinder block is affected by materials, structural shapes, connecting bolts, and tightening processes. Under the selected material and shape structure conditions, the bolt tightening process becomes the most influential factor. When tightening the connecting bolts according to the normal tightening torque and tightening rotation angle, that is, the tightening torque M and the first tightening rotation angle σ, when the explosion pressure generated when the engine is working acts on the crankshaft, the main shaft hole of the lower cylinder block will have a large elastic deformation. This elastic deformation will cause too large a local gap between the main shaft hole of the lower cylinder block and the crankshaft journal, resulting in an out-of-tolerance neck runout of the main shaft hole of the lower cylinder block, causing damage such as vibration noise and severe bearing shell wear, affecting the normal operation of the engine.

[0029] Therefore, in order to offset part of the deformation amount of the main shaft hole of the lower cylinder block under the explosion pressure condition, this application adopts a reverse pre-deformation process during assembly, that is, on the basis of the tightening torque M and the first tightening rotation angle σ, over-tightening is carried out based on the pre-deformation rotation angle γ until the connecting bolts are tightened to the second tightening rotation angle β, so that the main shaft hole of the lower cylinder block has a reverse deformation trend in advance. In this way, even when the explosion pressure generated when the engine is working acts on the crankshaft, the positive deformation of the main shaft hole of the lower cylinder block will offset this reverse deformation trend, realizing that the main shaft hole of the lower cylinder block maintains an approximately circular aperture under the explosion pressure condition, thereby preventing the out-of-tolerance neck runout of the main shaft hole of the lower cylinder block, causing damage such as vibration noise and severe bearing shell wear, and affecting the normal operation of the engine. Description of the Drawings

[0030] In order to more clearly illustrate the technical solutions in the embodiments of this application, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of this application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0031] Figure 1 Schematic diagram of the fitting curve of the aperture deformation of the main shaft hole and the basic circle of the main shaft hole provided by the embodiment of the present application;

[0032] Figure 2 Schematic diagram of the mapping conversion of the aperture deformation of the main shaft hole provided by the embodiment of the present application. Detailed implementation manners

[0033] To make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Apparently, the described embodiments are some, but not all, of the embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative efforts shall fall within the protection scope of the present application.

[0034] The embodiment of the present application provides a method for controlling the pre-deformation of the main shaft hole of the engine lower cylinder block, which includes the following steps:

[0035] 101: Tighten the upper cylinder block and the main bearing seat of the lower cylinder block with the connecting bolts according to the tightening torque M and the first tightening rotation angle σ to complete the rough machining of the main shaft hole of the lower cylinder block;

[0036] 102: Loosen the connecting bolts, assemble the main shaft, and tighten the upper cylinder block and the main bearing seat of the lower cylinder block with the connecting bolts according to the tightening torque M and the second tightening rotation angle β; wherein, based on the first tightening rotation angle σ and the pre-deformation rotation angle γ, the second tightening rotation angle β is obtained.

[0037] The principle of the present application is as follows:

[0038] The cylinder block of the engine is assembled by the main bearing seat of the lower cylinder block and the upper cylinder block with connecting bolts. The main shaft hole of the cylinder block is divided into two parts, namely the upper cylinder block main shaft hole on the upper cylinder block and the lower cylinder block main shaft hole on the main bearing seat of the lower cylinder block. After the upper cylinder block and the main bearing seat of the lower cylinder block are installed, the two are butted to form the main shaft hole. Generally, the deformation of the main shaft hole of the engine lower cylinder block is affected by materials, structural shapes, connecting bolts, and tightening processes. Under the conditions of selected materials and shape structures, the bolt tightening process becomes the biggest influencing factor. When tightening with the normal tightening torque and tightening rotation angle of the connecting bolts, that is, the tightening torque M and the first tightening rotation angle σ, the main shaft hole of the lower cylinder block will have large elastic deformation when the explosion pressure generated during the operation of the engine acts on the crankshaft. This elastic deformation will cause the local clearance between the main shaft hole of the lower cylinder block and the crankshaft journal to be too large, resulting in the over-tolerance of the main shaft hole neck runout, causing damage such as vibration noise and serious bearing shell wear, and affecting the normal operation of the engine.

[0039] Therefore, to offset part of the deformation of the main shaft hole of the lower cylinder block under the explosion pressure condition, the present application adopts a reverse pre-deformation process during assembly, that is, based on the tightening torque M and the first tightening rotation angle σ, over-tightening is performed based on the pre-deformation rotation angle γ until the connecting bolt is tightened to the second tightening rotation angle β, so that the main shaft hole of the lower cylinder block has a reverse deformation tendency in advance. In this way, even when the explosion pressure generated during engine operation acts on the crankshaft, the positive deformation of the main shaft hole of the lower cylinder block will offset this reverse deformation tendency, so that the main shaft hole of the lower cylinder block maintains an approximately circular aperture under the explosion pressure condition, thereby preventing the neck runout of the main shaft hole of the lower cylinder block from exceeding the tolerance, causing damage such as vibration noise and severe bearing shell wear, and affecting the normal operation of the engine.

[0040] Specifically, the second tightening rotation angle β is the sum of the first tightening rotation angle σ and the pre-deformation rotation angle γ.

[0041] It should be noted that the application direction of the pre-deformation rotation angle γ is the same as that of the first tightening rotation angle σ.

[0042] Under the action of the explosion pressure transmitted by the crankshaft, the main shaft hole of the lower cylinder block will expand outward in the explosion pressure direction. In fact, even if the upper cylinder block is made of cast iron material, the main shaft hole of the upper cylinder block will also show a certain degree of deformation, that is, it will expand outward in the explosion pressure direction (it should be noted that this deformation of the main shaft hole of the upper cylinder block is usually ignored because this deformation of the main shaft hole of the upper cylinder block is within the allowable range). At the same time, in the direction perpendicular to the explosion pressure direction, the main shaft holes of the upper cylinder block and the lower cylinder block will contract inward. Eventually, this deformation makes the main shaft hole of the cylinder block gradually change from a circular shape to an approximately elliptical shape.

[0043] The applicant can obtain an ellipse by measuring the aperture change of the main shaft hole of the cylinder block under the action of the explosion pressure and performing curve fitting, which also proves the above conclusion. Specifically, as shown in Figure 1 As shown, with the arrangement direction of the main bearing seats of the upper cylinder block and the lower cylinder block as the Y direction, the X direction is perpendicular to the Y direction, and the explosion pressure direction transmitted by the crankshaft is along the Y direction. Obviously, the fitting curve A of the aperture deformation of the main shaft hole approaches an elliptical curve. Comparing this elliptical curve with the base circle B of the main shaft hole, the applicant unexpectedly found that the deformation amount is almost 0 at the angle of 45° in the first quadrant. Therefore, within the elastic deformation range of the material: the maximum deformation amount Ly in the Y direction and the maximum deformation amount Lx in the X direction of the main shaft hole satisfy a certain functional relationship of the difference between the fitting curve and the base circle. Only in this way can an ellipse be formed during the process of deformation offsetting each other. Therefore, for the deformation amount of the main shaft hole, only the unidirectional deformation amount can be controlled, that is, only Ly or only Lx can be controlled. Usually, the maximum deformation affecting the main shaft runout generally appears in the direction same as the explosion pressure. Therefore, it is preferred to control the deformation in the Y direction, that is, to control the value of Ly.

[0044] In addition, since the engine block is assembled by the lower block main bearing seat and the upper block through connecting bolts, and the axial direction of the connecting bolts is the same as the layout direction of the upper block and the lower block main bearing seat, and this direction is also the same as the direction of the explosion pressure, the reverse pre-deformation of the lower block main shaft hole can be achieved by using the tightening process of the connecting bolts. Therefore, the applicant is further driven to preferentially control the deformation of the lower block main shaft hole in the direction of the explosion pressure transmitted by the crankshaft, that is, to control Figure 1 the Ly value in the Y direction in

[0045] Based on the above findings, in order to obtain the pre-deformation angle γ, the method provided in this application further includes the step of obtaining the pre-deformation angle γ.

[0046] The principle of obtaining the pre-deformation angle γ is as follows: within the elastic deformation range, the pre-deformation amount of the lower block main shaft hole is mapped and converted into the pressing-down amount of the connecting bolt clamping surface of the lower block main bearing seat through the principle of similar triangles, and then converted into the pre-deformation angle γ of the connecting bolt torque.

[0047] Specifically, referring to Figure 2 the schematic diagram of the mapping conversion of the main shaft hole aperture deformation amount shown, the steps of obtaining the pre-deformation angle γ include the following:

[0048] 201: Based on the maximum deformation amount Ly of the lower block main shaft hole in the direction of the explosion pressure transmitted by the crankshaft, the radius R of the lower block main shaft hole, and the height Hs of the lower block main bearing seat, obtain the pressing-down amount Lm of the connecting bolt clamping surface of the lower block main bearing seat. Among them, Figure 2 the elliptical curve C in

[0049] is the trend line of the main shaft hole after reverse pre-deformation.

[0050] In step 201, the engine working condition CAE analysis can be carried out to obtain the maximum deformation amount Ly value of the lower block main shaft hole relative to the main shaft hole base circle B in the Y direction. For example, taking the aperture of the lower block main shaft hole of the cast iron material under the explosion pressure as the base circle (the default deformation amount is tiny and negligible).

[0051] Using the geometric similar triangle mapping method, the Ly value is converted to the pressing-down amount Lm of the connecting bolt clamping surface of the lower block main bearing seat.

[0052] Its conversion mapping relationship is: Lm = K1 × K2 × Ly, where K2 = Hs / R, K1 is a correction coefficient, and its value range is 0.85 - 1.2; R is the radius of the main shaft hole base circle B, and Hs is the height of the lower block main bearing seat.

[0053] The mapping relationships between the pre-tightening force Fm of the connecting bolt and Lm, and between Fm and the rotation angle of the connecting bolt are known quantities.

[0054] Among them, the mapping relationship between the pre-tightening force Fm of the connecting bolt and Lm can be obtained by looking up the tightening calculation formula of the torque-rotation angle method.

[0055] The mapping relationship between Fm and the rotation angle of the connecting bolt is obtained by looking up the tightening calculation formula of the torque-rotation angle method.

[0056] Specifically, from Lm = Fm / Cp, we get Fm = Lm × Cp, where Cp is the stiffness of the lower cylinder block;

[0057] δ is calculated by δ = 360°×(Fm / P)×(1 / Cs + 1 / Cp); Cs is the stiffness of the connecting bolt; P is the pitch of the connecting bolt.

[0058] 203: Based on the pre-deformation reference rotation angle δ, the pre-deformation rotation angle γ is obtained.

[0059] In step 203, based on the pre-deformation reference rotation angle δ, the pre-deformation rotation angle γ is obtained. The pre-deformation reference rotation angle δ can be directly used, that is, the pre-deformation reference rotation angle δ is used as the pre-deformation rotation angle γ.

[0060] Of course, sometimes in order to leave some margin to prevent over-tightening, and at the same time, there may be decimal values during calculation, which are not easy to quantify during the actual tightening. Therefore, rounding is usually performed. That is, based on the pre-deformation reference rotation angle δ, the pre-deformation rotation angle γ is obtained, specifically including: rounding down the pre-deformation reference rotation angle δ to obtain the pre-deformation rotation angle γ.

[0061] For example, as an example, when the actually calculated pre-deformation reference rotation angle δ is 30.3°, after rounding down, 30° is used as the pre-deformation reference rotation angle δ.

[0062] Of course, a correction value can also be designed, and a mathematical operation is performed on the pre-deformation reference rotation angle δ and the correction value to obtain the pre-deformation rotation angle γ. The size of the correction value can be determined according to experience or actual needs.

[0063] For example, subtracting the correction value from the pre-deformation reference rotation angle δ to obtain the pre-deformation rotation angle γ.

[0064] As an example, the pre-deformation reference rotation angle δ is 30°, and the correction value is 2°, then the pre-deformation rotation angle γ is taken as 28°.

[0065] Therefore, in step 203, based on the pre-deformation reference rotation angle δ, the pre-deformation rotation angle γ is obtained, and different processing schemes can be selected according to the actual situation.

[0066] It should be noted that after rough machining of the main shaft holes of the lower cylinder block and before loosening the connecting bolts and assembling the main shaft, the method further includes: loosening the connecting bolts, and then using the connecting bolts to tighten the upper cylinder block and the main bearing seat of the lower cylinder block again according to the tightening torque M and the first tightening rotation angle σ to complete the finish machining of the main shaft holes of the lower cylinder block.

[0067] In this application, a finish machining step, that is, a re-tightening operation, is added between step 101 and step 102. The advantage is that it can eliminate the shape errors generated during the rough machining process.

[0068] It should be noted that the method for controlling the pre-deformation of the main shaft holes of the engine lower cylinder block provided in the embodiments of this application, that is, by adopting the reverse pre-deformation process, enables the main shaft holes to have a reverse deformation trend in advance, thereby preventing the neck runout of the main shaft holes of the lower cylinder block from exceeding the tolerance, causing damage such as vibration noise and severe bearing shell wear, which affects the normal operation of the engine. It is not only applicable to the lower cylinder block made of aluminum alloy material, but also applicable to the lower cylinder block made of other materials, as long as the main shaft holes of such lower cylinder blocks are deformed due to the explosion pressure and this deformation needs to be eliminated, even for the lower cylinder block made of cast iron material.

[0069] The embodiments of this application also provide an engine, which includes an upper cylinder block and a main bearing seat of the lower cylinder block, and the upper cylinder block and the main bearing seat of the lower cylinder block are connected by connecting bolts. The connecting bolts have a tightening torque M and a second tightening rotation angle β, wherein the second tightening rotation angle β is obtained based on the first tightening rotation angle σ and the pre-deformation rotation angle γ.

[0070] Specifically, for the above-mentioned engine, the connecting bolts can be tightened by using the method for controlling the pre-deformation of the main shaft holes of the engine lower cylinder block provided in the above embodiments.

[0071] When assembling the engine provided in the embodiments of this application, a reverse pre-deformation process is adopted, that is, on the basis of the tightening torque M and the first tightening rotation angle σ, over-tightening is performed based on the pre-deformation rotation angle γ until the connecting bolts are tightened to the second tightening rotation angle β, so that the main shaft holes have a reverse deformation trend in advance. In this way, even when the explosion pressure generated during the operation of the engine acts on the crankshaft, the positive deformation of the main shaft holes of the lower cylinder block will offset this reverse deformation trend, realizing that the main shaft holes of the lower cylinder block maintain an approximately circular aperture under the explosion pressure condition, thereby preventing the neck runout of the main shaft holes of the lower cylinder block from exceeding the tolerance, causing damage such as vibration noise and severe bearing shell wear, which affects the normal operation of the engine.

[0072] Embodiment

[0073] Through the CAE analysis of the main bearing seat of the aluminum alloy lower cylinder block of the engine under the explosion pressure condition, the maximum difference Ly in the deformation amount in the Y direction between it and the main shaft holes of the cast iron lower cylinder block is about 0.19 mm.

[0074] Through the deformation control mapping method of this application, the deformation of the main shaft hole is mapped to obtain the pressing-down amount Lm of the connecting bolt clamping surface of the main bearing seat of the lower cylinder block, Lm = 0.9×100 / 48×0.19 ≈ 0.356mm, where the base circle radius R = 48mm, the height of the main bearing seat of the lower cylinder block is 100mm, and the correction coefficient is taken as 0.9;

[0075] Substitute Lm = 0.356mm into the formula of bolt rotation angle, pre-tightening force and pressing-down amount to calculate the pre-deformation reference rotation angle δ ≈ 31.4°, and round it to get the pre-deformation rotation angle γ = 30°.

[0076] Then the pre-deformation control process of the main shaft hole of the aluminum alloy lower cylinder block is as follows:

[0077] During the rough machining of the main shaft hole of the aluminum alloy lower cylinder block, connect the main bearing seat of the aluminum alloy lower cylinder block and the cast iron upper cylinder block with connecting bolts. The tightening torque of the connecting bolts is 75N.M, and the tightening rotation angle is 115°; then carry out the rough machining of the main shaft hole;

[0078] Next, carry out the finish machining of the main shaft hole of the aluminum alloy lower cylinder block: completely loosen the connecting bolts between the main bearing seat of the aluminum alloy lower cylinder block and the cast iron upper cylinder block. After waiting for 5 - 10S, connect the main bearing seat of the aluminum alloy lower cylinder block and the cast iron upper cylinder block with connecting bolts, and still use the tightening process with a tightening torque of 75N.M and a tightening rotation angle of 115° to tighten it for the second time, and then carry out the finish machining of the main shaft hole. At this time, the aperture of the main shaft hole is approximately the base circle;

[0079] During the assembly of the whole engine: loosen the connecting bolts of the cylinder block assembly (the upper cylinder block and the combined part of the main bearing seat of the lower cylinder block) after finishing the finish machining. After assembling parts such as bearing shells and main shafts, connect the main bearing seat of the aluminum alloy lower cylinder block and the cast iron upper cylinder block with connecting bolts. The tightening torque of the connecting bolts is 75N.M, and the tightening rotation angle is 115° + 30° = 145°, so as to realize the controllable pre-deformation of the main shaft hole, and its aperture is approximately elliptical.

[0080] In the description of this application, it should be noted that the orientation or positional relationship indicated by terms such as "upper" and "lower" is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing this application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it cannot be understood as a limitation to this application. Unless otherwise clearly specified and limited, the terms "installation", "connection" and "connection" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, or an electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to specific situations.

[0081] It should be noted that in this application, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, such that a process, method, article or device comprising a series of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "comprising an..." does not exclude the presence of additional identical elements in the process, method, article or device comprising the element.

[0082] The above are only specific embodiments of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application will not be limited to these embodiments shown herein, but rather will conform to the broadest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for controlling the pre-deformation of the main shaft holes in the lower cylinder block of an engine, characterized in that, It includes the following steps: Tighten the main bearing seat of the upper cylinder block and the lower cylinder block with the connecting bolts according to the tightening torque M and the first tightening rotation angle σ to complete the rough machining of the main shaft hole of the lower cylinder block; Loosen the connecting bolts, assemble the main shaft, and tighten the main bearing seat of the upper cylinder block and the lower cylinder block with the connecting bolts according to the tightening torque M and the second tightening rotation angle β; Wherein, based on the first tightening rotation angle σ and the pre-deformation rotation angle γ, the second tightening rotation angle β is obtained; The specific steps for obtaining the pre-deformation rotation angle γ include: Based on the maximum deformation amount Ly of the main shaft hole of the lower cylinder block in the direction of the explosion pressure transmitted by the crankshaft, the radius R of the main shaft hole of the lower cylinder block, and the height Hs of the main bearing seat of the lower cylinder block, obtain the pressing-down amount Lm of the connecting bolt clamping surface of the main bearing seat of the lower cylinder block; Based on the mapping relationship between Lm, the pre-tightening force Fm of the connecting bolt and Lm, and the mapping relationship between Fm and the rotation angle of the connecting bolt, obtain the pre-deformation reference rotation angle δ; Based on the pre-deformation reference rotation angle δ, obtain the pre-deformation rotation angle γ.

2. The method for controlling the pre-deformation of the main shaft holes of the lower cylinder block of an engine according to claim 1, wherein: The second tightening rotation angle β is the sum of the first tightening rotation angle σ and the pre-deformation rotation angle γ.

3. The method for controlling the pre-deformation of the main shaft holes of the lower cylinder block of an engine according to claim 1, wherein, Based on the pre-deformation reference rotation angle δ, obtaining the pre-deformation rotation angle γ specifically includes: Round down the pre-deformation reference rotation angle δ to obtain the pre-deformation rotation angle γ.

4. The method for controlling the pre-deformation of the main shaft holes of the engine lower cylinder block according to claim 1, characterized in that Based on the pre-deformation reference rotation angle δ, obtaining the pre-deformation rotation angle γ specifically includes: Subtract the correction value from the pre-deformation reference rotation angle δ to obtain the pre-deformation rotation angle γ.

5. The method for controlling the pre-deformation of the main shaft holes of the lower cylinder block of an engine according to claim 1, characterized in that, After completing the rough machining of the main shaft hole of the lower cylinder block and before loosening the connecting bolts and assembling the main shaft, the method further includes: Loosen the connecting bolts, and tighten the main bearing seat of the upper cylinder block and the lower cylinder block with the connecting bolts again according to the tightening torque M and the first tightening rotation angle σ to complete the finish machining of the main shaft hole of the lower cylinder block.

6. The method for controlling the pre-deformation of the main shaft holes of the lower cylinder block of an engine according to claim 1, characterized in that: The lower cylinder block is made of cast iron material.

7. The method for controlling the pre-deformation of the main shaft holes of the engine lower cylinder block according to claim 1, wherein: The lower cylinder block is made of aluminum alloy material.

8. An engine, characterized in that: It includes the main bearing seat of the upper cylinder block and the lower cylinder block, and the main bearing seat of the upper cylinder block and the lower cylinder block are connected by connecting bolts. The connecting bolts have a tightening torque M and a second tightening rotation angle β. Wherein, based on the first tightening rotation angle σ and the pre-deformation rotation angle γ, the second tightening rotation angle β is obtained; The specific steps for obtaining the pre-deformation rotation angle γ include: Based on the maximum deformation amount Ly of the main shaft hole of the lower cylinder block in the direction of the explosion pressure transmitted by the crankshaft, the radius R of the main shaft hole of the lower cylinder block, and the height Hs of the main bearing seat of the lower cylinder block, obtain the pressing-down amount Lm of the connecting bolt clamping surface of the main bearing seat of the lower cylinder block; Based on the mapping relationship between Lm, the pre-tightening force Fm of the connecting bolt and Lm, and the mapping relationship between Fm and the rotation angle of the connecting bolt, obtain the pre-deformation reference rotation angle δ; Based on the pre-deformation reference rotation angle δ, obtain the pre-deformation rotation angle γ.

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