CN112580156B - A kind of gasoline engine cylinder head bolt selection and checking method - Google Patents

Abstract

The invention relates to a method for selecting and checking a cylinder head bolt of a gasoline engine, and belongs to the technical field of vehicle manufacturing. The method provided by this application obtains the maximum working load of the engine and further obtains the maximum external load of the single bolt of the cylinder head through the maximum burst pressure of the engine, and finally simplifies to a single bolt to seal the cylinder head according to the predetermined safety factor determined by the attenuation of the axial force. The required pre-tightening force, followed by positive selection of the bolts, and then considering the bolts in the mass production state, the specifications and dimensions, friction coefficient dispersion, yield strength dispersion and actual conditions between multiple batches of bolts are accurate. Obtain the actual maximum pre-tightening force and the actual minimum pre-tightening force of the bolts, and finally check them. The method can accurately select the type of the cylinder head bolts of the gasoline engine, the method is simpler and more perfect, and the selected bolts are more suitable for the actual operation of the gasoline engine.

Description

A kind of gasoline engine cylinder head bolt selection and checking method

technical field

The invention belongs to the technical field of vehicle manufacturing, and in particular relates to a method for selecting and checking the type of a cylinder head bolt of a gasoline engine.

Background technique

Cylinder head bolts are mainly used for the fastening and connection of engine cylinder head, cylinder gasket and cylinder block. By tightening, a uniform and appropriate axial tightening force is generated on the cylinder gasket to seal the high temperature and high pressure gas in the cylinder, and at the same time seal the cooling water, lubricating Oil. Cylinder head bolts must have sufficient rigidity and fatigue strength to withstand the pressure and thermal load of the gas in the cylinder, otherwise the "three leakage" problem of the engine will easily occur, affecting the reliability of the engine and even causing engine damage; therefore, cylinder head bolts belong to the engine. key piece.

However, in the prior art, the design method of the bolts on the cylinder head is not perfect, which leads to safety risks in the use of the cylinder head bolts.

SUMMARY OF THE INVENTION

The invention provides a method for selecting and checking the cylinder head bolt of a gasoline engine, which is used to solve the technical problem that the bolt design method on the cylinder head is not perfect in the prior art, which leads to the safety risk of the cylinder head bolt during use.

The present invention is realized through the following technical solutions: a method for selecting and checking the cylinder head bolts of a gasoline engine, comprising:

obtaining the maximum working load of the engine according to the maximum burst pressure of the engine;

Obtain the maximum external load of a single bolt of the cylinder head according to the maximum working load of the engine;

The pre-tightening force required by a single bolt to seal the cylinder head is determined according to a predetermined safety factor and the maximum external load of the single bolt, and the predetermined safety factor is determined according to the attenuation of the axial force during the use of the bolt ;

Preliminarily select the bolt type and the gasket type according to the boundary conditions of the bolt assembly of the cylinder head and the pre-tightening force required by the single bolt to seal the cylinder head;

Combined with the mass production of bolts, there are differences in the parameters of multiple batches of bolts. According to the minimum yield strength and maximum friction coefficient of the bolts corresponding to the selected bolt types, the actual minimum preload force of the bolts is obtained, and according to The maximum yield strength and the minimum friction coefficient of the bolts obtain the actual maximum preload force of the bolts;

Obtain the actual safety factor of the bolt according to the actual minimum pre-tightening force of the bolt and the maximum external load of the single bolt of the cylinder head, and compare the actual safety factor of the bolt with the predetermined safety factor;

According to the actual maximum pre-tightening force of the bolts and the pressure bearing area between the cylinder head and the gasket, the contact stress of the bearing surface between the cylinder head and the gasket is obtained, and the cylinder head is connected to the gasket. Comparing the contact stress of the pressure bearing surface between the cover and the gasket and the allowable contact stress of the cylinder head manufacturing material;

According to the actual maximum pre-tightening force of the bolt and the pressure-bearing area between the washer and the bolt head, the contact stress of the pressure-bearing surface between the washer and the bolt head is obtained, and the Compare the contact stress of the pressure-bearing surface between the gasket and the bolt head with the allowable contact stress of the gasket manufacturing material;

When the actual safety factor is greater than the predetermined safety factor, and the contact stress of the pressure-bearing surface of the cylinder head and the gasket is less than the allowable contact stress of the cylinder head manufacturing material and the gasket and the gasket When the contact stress of the pressure-bearing surface where the bolt heads are connected is less than the allowable contact stress of the gasket manufacturing material, the selected bolt type is determined to be qualified.

Further, in order to better realize the present invention, obtaining the maximum working load of the engine according to the maximum explosion pressure of the engine is specifically:

所述P_max为所述发动机的最大爆发压力，所述d_g为所述发动机气缸垫缸孔直径。The maximum working load of the engine

The P _max is the maximum explosion pressure of the engine, and the d _g is the diameter of the cylinder head of the engine.

Further, in order to better realize the present invention, the maximum external load of a single bolt of the cylinder head is obtained according to the maximum working load of the engine, specifically:

The maximum external load of the single bolt of the cylinder head

Further, in order to better realize the present invention, the pre-tightening force required by a single bolt to seal the cylinder head is determined according to a predetermined safety factor and the maximum external load of the single bolt, specifically:

The pre-tightening force F _v =K×F _b required by the single bolt to seal the cylinder head, where K is a predetermined safety factor of the bolt.

Further, in order to better realize the present invention, the value range of the predetermined safety factor K of the bolt is 1.6-1.8.

Further, in order to better realize the present invention, the actual minimum pre-tightening force of the bolt is obtained according to the minimum yield strength and the maximum friction coefficient of the bolt corresponding to the selected bolt type, specifically: the actual minimum pre-tightening force of the bolt is: Minimum preload

The actual maximum pre-tightening force of the bolt is obtained according to the maximum yield strength and the minimum friction coefficient of the bolt, specifically:

Actual maximum preload of said bolts

The v is the yield strength utilization coefficient of the bolt, the R _P0.2max is the maximum yield strength of the bolt, the R _P0.2min is the minimum yield strength of the _bolt , and the As is the The nominal stress cross-sectional area of the external thread of the bolt, the d ₂ is the pitch diameter of the bolt's thread, the d ₀ is the equivalent diameter of the nominal stress cross-sectional area of the external thread of the bolt, and the α' is the thread of the bolt flank angle, the μ _smin is the minimum friction coefficient of the bolt thread, the μ _smax is the maximum friction coefficient of the bolt thread, and the P is the thread pitch of the bolt.

Further, in order to better realize the present invention, the actual safety factor of the bolt is obtained according to the actual minimum pre-tightening force of the bolt and the pre-tightening force required for the single bolt to seal the cylinder head. ,Specifically:

Actual safety factor of said bolts

Further, in order to better realize the present invention, the phase between the cylinder head and the gasket is obtained according to the actual maximum pre-tightening force of the bolt and the pressure bearing area between the cylinder head and the gasket. The contact stress of the bearing surface of the connection is as follows:

所述A_C为所述气缸盖与垫片之间的承压面积。The contact stress of the pressure bearing surface where the cylinder head and the gasket are connected

The _AC is the pressure bearing area between the cylinder head and the gasket.

Further, in order to better realize the present invention, the washer and the bolt head are obtained according to the actual maximum pre-tightening force of the bolt and the pressure bearing area between the washer and the bolt head. The contact stress of the pressure-bearing surface where the parts are connected, specifically:

所述A_d为所述垫片与螺栓之间的承压面积。The contact stress of the bearing surface where the gasket is connected to the head of the bolt

The _Ad is the pressure bearing area between the gasket and the bolt.

Further, in order to better realize the present invention, the above method is executed in an EXCEL form.

Compared with the prior art, the present invention has the following beneficial effects:

The method for selecting and checking the cylinder head bolts of the gasoline engine provided by the invention obtains the maximum working load of the engine based on the maximum burst pressure of the engine, thereby calculating the maximum external load of a single bolt of the cylinder head, simplifying the force model and improving the design safety margin. In the design process, the axial force attenuation during the use of the bolt is fully considered to determine the predetermined safety factor, and combined with the maximum external load of a single bolt, the preload required for a single bolt to seal the cylinder head is calculated, and then according to the cylinder head. The boundary conditions of bolt assembly and the pre-tightening force required to seal the cylinder head by a single bolt are used to carry out positive selection of cylinder head bolts and gaskets to determine the direction of bolt selection, avoid blind trial among many types of bolts, and improve work efficiency. Efficiency. After the initial selection of bolts, the actual minimum preload force and the actual maximum preload force are calculated for the selected bolts. During this process, the key parameters of the selected bolts under mass production, such as yield strength and friction, are fully considered. There is a dispersion difference in the coefficient, and the actual maximum pre-tightening force and the actual minimum pre-tightening force of the bolt are accurately calculated according to the bolt specification and actual situation. For example, the yield strength utilization coefficient is determined according to the bolt tightening method, and finally the actual minimum pre-tightening force of the selected bolt is used. The actual safety factor of the selected bolt is determined by the ratio between the maximum external load of a single bolt of the cylinder head, and the actual safety factor of the selected bolt is compared with the estimated safety factor. If the actual safety factor is less than or equal to the estimated safety factor When the actual safety factor is greater than the estimated safety factor, it is qualified, and then the actual maximum preload of the selected bolts and the pressure-bearing area between the cylinder head and the gasket are determined. Calculate the contact stress of the pressure-bearing surface of the cylinder head and the gasket, and compare the calculated contact stress of the pressure-bearing surface of the cylinder head and the gasket with the allowable contact stress of the material of the cylinder head. Select the ratio of the actual maximum pre-tightening force of the bolt to the pressure-bearing area between the gasket and the selected bolt to calculate the contact stress of the pressure-bearing surface between the gasket and the bolt head. Compare the contact stress of the bearing surface of the gasket with the allowable contact stress of the manufacturing material of the gasket, so as to verify whether the bolt selection meets the allowable contact stress of the gasket and the cylinder head, so as to ensure that the selected bolts meet the requirements. The method provided by the invention fully considers the axial force attenuation of the bolts in the process of selecting the engine cylinder head bolts, and the bolt parameters such as bolt specifications, friction coefficient and yield strength are scattered among multiple batches under the mass production state of the bolts. Therefore, the range of bolt pre-tightening force is determined in combination with the actual production state when the pre-tightening force is defined, which makes the selection of bolts more accurate and reduces the probability of safety problems during the use of cylinder head bolts.

Description of drawings

In order to explain the embodiments of the present invention or the technical solutions in the prior art more clearly, the following briefly introduces the accompanying drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only These are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can also be obtained from these drawings without creative efforts.

Fig. 1 is the flow chart of the gasoline engine cylinder head bolt selection and checking method in the present application;

Figure 2 is an example table of the process used in this application to determine the preload required for a single bolt to seal the cylinder head;

Figure 3 is an example table of the calculation process of bolt selection and actual maximum preload force and actual minimum preload force in this application;

Figure 4 is an example form of the bolt checking process in this application;

FIG. 5 is a schematic structural diagram of the connection between the cylinder head and the cylinder block in the present application.

In the picture:

1- Cylinder head; 2- Cylinder block; 3- Bolt; 4- Gasket.

Detailed ways

In order to make the objectives, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be described in detail below. Obviously, the described embodiments are only some, but not all, embodiments of the present invention. Based on the embodiments of the present invention, all other implementations obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present invention.

Example 1:

This embodiment provides a method for selecting and checking the cylinder head bolt of a gasoline engine, which is used to solve the technical problem that the bolt design method on the cylinder head is not perfect in the prior art, which leads to the safety risk of the cylinder head bolt during use. . Specifically, in the existing engine cylinder head bolt design methods, the actual conditions such as the friction coefficient dispersion, yield strength dispersion, specifications and dimensions of the bolts are not considered, and most of the bolts of different specifications are tested by testing bolts of different specifications. If the wrong method is selected, the pre-tightening force of the selected bolts may not meet the requirements due to the above reasons, and the selection and verification process are complicated and error-prone, so that the selected bolts have a greater safety risk in use.

The method for selecting and checking the cylinder head bolts of a gasoline engine includes the following steps:

计算发动机的最大工作载荷F_g，由于汽车发动机的最大工作载荷为在发动机气缸体内发生爆震、产生最大爆发压力工况下产生，因此，P_max为发动机的最大爆发压力，d_g为所述发动机气缸垫缸孔直径；Step 1.1: Pass

Calculate the maximum working load F _g of the engine. Since the maximum working load of the automobile engine is generated under the condition of knocking and generating the maximum explosion pressure in the engine cylinder body, P _max is the maximum explosion pressure of the engine, and d _g is the Engine cylinder head cylinder bore diameter;

计算气缸盖1单颗螺栓3的最大动载荷，由于整体式气缸盖结构，各缸周围均布置4颗螺栓3，但相邻两缸体2共用布置在两缸之间的螺栓3，并且螺栓3与气缸盖1之间还设有垫片4。因此在受力分析时，可简化受力模型，即认为每一缸由两颗独立的气缸盖1螺栓3来紧固密封，因此气缸盖1单颗螺栓3的最大外载荷通过发动机最大工作载荷除以2。Step 1.2: Pass

Calculate the maximum dynamic load of a single bolt 3 of cylinder head 1. Due to the integral cylinder head structure, 4 bolts 3 are arranged around each cylinder, but two adjacent cylinder blocks 2 share the bolt 3 arranged between the two cylinders, and the bolts 3 are arranged between the two cylinders. A gasket 4 is also provided between 3 and the cylinder head 1 . Therefore, in the force analysis, the force model can be simplified, that is, it is considered that each cylinder is fastened and sealed by two independent cylinder heads 1 bolts 3, so the maximum external load of a single bolt 3 of the cylinder head 1 passes the maximum working load of the engine Divide by 2.

Step 1.3: Calculate the preload force F _v required for a single bolt 3 to seal the cylinder head 1 through F _v =K×F _b (Equation 3). The determined estimated safety factor. In this step, the microscopic surface unevenness of the pressure bearing surface of the cylinder head 1, the compression deformation of the cylinder head gasket and the engine operation, due to the long-term mechanical, cold and hot alternating loads, cause the material of the connected parts to creep and thin, resulting in the shaft Force attenuation, and for cylinder gaskets with different layers and different sealing structures, the preload required for sealing changes accordingly, and the estimated safety factor K determined from this is more reasonable, so that the calculated single The bolts 3 make the preload force F _v required for the sealing of the cylinder head 1 more precise, and the safety margin left is more compliant. As an implementation of this embodiment, the value of K in this embodiment ranges from 1.6 to 1.8. Preferably, the value of K is 1.6.

It is worth noting that the single bolt 3 in steps 1.1 to 1.3 corresponds to the bolt assumed to meet the assembly requirements.

进行螺栓3的实际最小预紧力计算，式4中的v为螺栓3的屈服强度利用系数，R_P0.2min为螺栓3的最小屈服强度，A_s为螺栓3的外螺纹公称应力截面积，d₂为螺栓3的螺纹中径，d₀为螺栓3的外螺纹公称应力截面积当量直径，α′为螺栓3的螺纹牙侧角，μ_smax为螺栓3螺纹的最大摩擦系数，P为螺栓3的螺距。该步骤中，首先根据装配边界确定螺栓规格以及尺寸，也即对螺栓3进行正向选型，避免在众多型号的螺栓3中盲目选型，提高工作效率，随后通过式4算出选出的螺栓3的实际最小预紧力，并与F_v进行对比，以进行螺栓3的初步选型。而且，该步骤中，充分考虑到在量产状态下，不同批次螺栓3自身规格以及尺寸、摩擦系数散差、屈服强度散差以及具体使用情况而更加精准地确定的螺栓3的实际最小预紧力。Step 2.1: According to the assembly boundary conditions of bolt 3 of cylinder head 1 and F _v , the type of bolt 3 and the type of gasket 4 are preliminarily selected. The rated minimum preload force of bolt 3 must be greater than that required for a single bolt 3 to seal cylinder head 1. Preload force F _v . pass

Calculate the actual minimum pre-tightening force of bolt 3. In formula 4, v is the yield strength utilization coefficient of bolt 3, R _P0.2min is the minimum yield strength of bolt 3, and As is the nominal stress cross-sectional area of external thread of bolt ₃ . d ₂ is the pitch diameter of the bolt 3, d ₀ is the nominal stress cross-sectional area equivalent diameter of the bolt 3, α′ is the thread flank angle of the bolt 3, μ _smax is the maximum friction coefficient of the bolt 3 thread, P is the bolt 3 pitches. In this step, first determine the bolt specification and size according to the assembly boundary, that is, perform positive selection of bolt 3 to avoid blind selection among many types of bolts 3 and improve work efficiency, and then calculate the selected bolts by formula 4. The actual minimum preload force of 3 and compared with F _v for the preliminary selection of bolt 3. Moreover, in this step, the actual minimum pre-measurement of the bolts 3 is more accurately determined by fully considering the specifications and dimensions of the bolts 3 in different batches, the friction coefficient dispersion, the yield strength dispersion and the specific use conditions under the mass production state. tight.

计算螺栓3的实际最大预紧力

式5中的v为螺栓3的屈服强度利用系数，R_P0.2max为螺栓3的最大屈服强度，A_s为螺栓3的外螺纹公称应力截面积，d₂为螺栓3的螺纹中径，d₀为螺栓3的外螺纹公称应力截面积当量直径，α′为螺栓3的螺纹牙侧角，μ_smin为螺栓3螺纹的最小摩擦系数，P为螺栓3的螺距。该步骤中，充分考虑到在量产状态下，不同批次螺栓3自身规格以及尺寸、摩擦系数散差、屈服强度散差以及具体使用情况而更加精准地确定的螺栓3的实际最大预紧力，需要注意的是，螺栓3的实际最大预紧力计算过程中，除了R_P0.2max和μ_smin与最小预紧力计算中不同以外，其余各参数均相同。Step 2.2: According to

Calculate the actual maximum preload for bolt 3

In formula 5, v is the yield strength utilization coefficient of bolt 3, R _P0.2max is the maximum yield strength of bolt 3, A _s is the nominal stress cross-sectional area of the external thread of bolt 3, d ₂ is the pitch diameter of the thread of bolt 3, d ₀ is the equivalent diameter of the nominal stress cross-sectional area of the external thread of the bolt 3, α′ is the thread flank angle of the bolt 3, μ _smin is the minimum friction coefficient of the thread of the bolt 3, and P is the pitch of the bolt 3. In this step, the actual maximum pre-tightening force of the bolts 3 is more accurately determined by fully considering the specifications and dimensions of the bolts 3 in different batches, the dispersion of the friction coefficient, the dispersion of the yield strength and the specific use conditions in the mass production state. , it should be noted that in the calculation process of the actual maximum preload force of bolt 3, except that R _P0.2max and μ _smin are different from those in the calculation of the minimum preload force, other parameters are the same.

It should be noted that in steps 2.1 and 2.2, the maximum yield strength R _P0.2max and the minimum yield strength R _P0.2min of bolt 3 depend on the material batch and production process control, and R _P0.2max and R _{P0.2min are required} The difference between R _P0.2max and R _P0.2min is within a range of 100MPa.

In addition, _μsmax and _μsmin mainly depend on the bolt 3 surface treatment process. Specifically, when the surface of the bolt 3 is oiled after phosphating, μ _smax =0.14, μ _smin =0.08; when the surface of the bolt 3 is blackened and oiled, μ _smax =0.16, μ _smin =0.10.

In addition, v in Equation 4 and Equation 5 depends on the specific tightening condition of bolt 3. When bolt 3 is tightened in elastic domain, the yield strength utilization coefficient v of bolt 3 ranges from 70% to 90%. Preferably, in this case, the yield strength utilization coefficient v of bolt 3 is 90%; when the tightening method of bolt 3 is plastic domain tightening, the yield strength utilization coefficient v of bolt 3 ranges from 100% to 110%. In this case, the yield strength utilization coefficient v of the bolt 3 is 100%.

In this way, the method provided by the present invention fully considers the axial force attenuation of the bolts 3 in the process of selecting the bolts 3 of the engine cylinder head 1, and the bolts 3 parameters such as bolt specifications between multiple batches under the mass production state of the bolts 3. There are differences in friction coefficient and yield strength. Therefore, when defining the pretightening force, combined with the actual production state, determine the range of bolt 3 pretightening force, which makes the selection of bolt 3 more accurate and reduces the occurrence of engine cylinder head 1 bolt 3 during use. chance of security issues.

计算选型后对应的螺栓3的实际安全系数K'，并将K'与K进行比较，在K'≤K时，则返回步骤2.1重新对螺栓3进行选型，在K'＞K时，则判定螺栓3选型合格。该步骤中，K’必须大于K值但应尽量接近，否则出现设计余量过大，造成材料浪费。Step 3.1: Pass

Calculate the actual safety factor K' of the corresponding bolt 3 after the selection, and compare K' with K. When K'≤K, go back to step 2.1 to select the bolt 3 again. When K'>K, Then it is judged that the selection of bolt 3 is qualified. In this step, K' must be greater than the K value but should be as close as possible, otherwise the design margin will be too large, resulting in material waste.

计算气缸盖1与垫片4相接的承压面接触应力σ_c，式7中的A_C为气缸盖1与垫片4之间的承压面积，随后将σ_c与气缸盖1的制造材料的许用接触应力进行比较，在σ_c小于气缸盖1的制造材料的许用接触应力时，则判定螺栓3选型合格，在σ_c大于或者等于气缸盖1的制造材料的许用接触应力时，则返回步骤2.1重新对螺栓3进行选型。Step 3.2: Pass

Calculate the contact stress σ _c of the pressure bearing surface of the cylinder head 1 and the gasket 4, AC in the _formula 7 is the pressure bearing area between the cylinder head 1 and the gasket 4, and then compare σ _c with the manufacture of the cylinder head 1 The allowable contact stress of the material is compared. When σ _c is less than the allowable contact stress of the manufacturing material of cylinder head 1, it is judged that the selection of bolt 3 is qualified. When σ _c is greater than or equal to the allowable contact stress of the manufacturing material of cylinder head 1 When the stress occurs, go back to step 2.1 to select bolt 3 again.

计算垫片4与螺栓3头部相接的承压面接触应力σ_d，式8中的A_d为垫片4与螺栓3头部之间的承压面积，随后将σ_d与垫片4的制造材料的许用接触应力进行比较，在σ_d小于垫片4的制造材料的许用接触应力时，则判定螺栓3选型合格，在σ_d大于或者等于垫片4的制造材料的许用接触应力时，则返回步骤2.1重新对螺栓3进行选型。Step 3.3: Pass

Calculate the contact stress σ _d of the bearing surface between the gasket 4 and the head of the bolt 3, A _d in Equation 8 is the bearing area between the gasket 4 and the head of the bolt 3, then σ _d and the gasket 4 The allowable contact stress of the manufacturing material is compared, and when σ _d is less than the allowable contact stress of the manufacturing material of gasket 4, it is judged that the selection of bolt 3 is qualified, and when σ _d is greater than or equal to the allowable contact stress of the manufacturing material of gasket 4 When using contact stress, return to step 2.1 to select bolt 3 again.

Through step 3.1, step 3.2 and step 3.3, the selected bolt 3 can be checked and checked, the accuracy of bolt 3 selection can be improved, and the safety of bolt 3 during use can be ensured.

In this embodiment, step 3.1, step 3.2, and step 3.3 may be performed simultaneously, that is, performed staggered. As long as the selected bolt 3 can simultaneously satisfy the three conditions of K'>K and σ _c less than the allowable contact stress of the manufacturing material of the cylinder head 1 and σ _d less than the allowable contact stress of the manufacturing material of the gasket 4, the The selected bolt 3 is qualified.

It is worth noting that the above steps 1.1 to 1.3 are actually the process of determining the minimum assembly pre-tightening force of bolt 3 (the pre-tightening force required for a single bolt 3 to seal the cylinder head 1). Steps 2.1 and 2.2 are the selection of bolt 3. And the calculation process of the actual maximum pre-tightening force and the actual minimum pre-tightening force, step 3.1, step 3.2 and step 3.3 are the verification process of bolt 3. In addition, the bolt 3 in step 2.1 to step 3.3 is the bolt after the selected model.

Specifically, when producing bolt 3, the definition of bolt 3 drawing is consistent with the above key parameter definitions, and the supplier's production control requirements are constrained to produce bolt 3 that meets the drawing requirements.

Example 2:

Embodiment is as a kind of example implementation of embodiment 1, as follows:

Step 1.1: It is known that the maximum explosion pressure P _max of the engine is 105MPa, the diameter d _g of the cylinder bore of the cylinder block 2 is 73 mm, and the maximum working load F _g =43.95kN of the engine is calculated by formula 1.

Step 1.2: Calculate the maximum dynamic load F _b =21.97kN of the single bolt 3 of the cylinder head by formula 2.

Step 1.3: Calculate the preload force F _v =K×F _b =1.6×21.97=35.16kN required for a single bolt 3 to seal the cylinder head 1 by formula 3. In this step, the cylinder head 1 is made of aluminum alloy material, the flatness of the pressure bearing surface of the cylinder head 1 is required to be 0.1, the roughness is required to be Ra3.2, and the cylinder head gasket is a double-layer sealing structure.

Step 2.1: In order to ensure the sealing of the cylinder head gasket, the minimum rated preload force of the bolt 3 is required to be greater than the preload force F _v required by a single bolt 3 to seal the cylinder head 1 . According to the bolt assembly boundary conditions of cylinder head 1 and F _v , the type of bolt 3 and the type of gasket 4 are preliminarily selected. The specification of bolt 3 is required to be ≤ M9, and the function of bolt 3 is to tighten. Therefore, the coarse thread is selected, that is, the pitch is 1.25, that is The specification of bolt 3 is M9×1.25, the maximum outer diameter of gasket 4 is Φ19.5mm, the inner diameter of gasket 4 is Φ11.1mm, the head diameter of bolt 3 is Φ13.7mm, and the diameter of through hole of bolt 3 on cylinder head 1 is Φ10. 5mm. The initial material of gasket 4 is 65Mn, and the maximum allowable contact stress is 980MPa. According to the consistency of raw materials and production process provided by the supplier, the yield strength range of bolt 3 is determined to be 100MPa; according to the anti-corrosion requirements, anti-rust oil is selected after phosphating, and the friction coefficient is 0.08-0.14. The yield strength of the bolt 3 is 1000 MPa using the coefficient v=100% and R _P0.2min . The actual minimum pre-tightening force F _Mmin = 39.27kN of the bolt 3 is calculated by formula 4, so it is greater than F _v .

Step 2.2: Calculate the actual maximum pre-tightening force F _Mmax =46.73kN of the selected bolt 3 by formula 5. Notably, the _μsmin in this step was 0.08 and the R _P0.2max was 1100 MPa.

Step 3.1: Calculate the actual safety factor K'=1.79>K of the selected bolt 3 by formula 6.

Step 3.2: Calculate the contact stress σ _c = 231.744kN of the pressure bearing surface of the cylinder head 1 and the gasket 4 through Equation 7, where the pressure bearing area between the cylinder head 1 and the gasket 4 A _C =201.88mm ² , The manufacturing material of the cylinder head 1 is aluminum alloy, and the allowable contact stress of the manufacturing material of the cylinder head 1 is 280MPa, so the contact stress of the pressure bearing surface between the cylinder head 1 and the gasket 4 is smaller than the allowable contact stress of the manufacturing material of the cylinder head 1 stress.

Step 3.3, calculate the contact stress σ _d = 922.74kN of the pressure-bearing surface between the gasket 4 and the head of the bolt 3 through Equation 8, where the pressure-bearing area between the gasket 4 and the head of the bolt 3 A _d =50.64mm ^2. The manufacturing material of the gasket 4 is 65Mn, and the allowable contact stress of the manufacturing material of the gasket 4 is 980 MPa, so the contact stress of the bearing surface between the gasket 4 and the head of the bolt 3 is less than the allowable contact stress of the gasket 4 manufacturing material. with contact stress.

Combining steps 3.1 to 3.3, it can be determined that when the bolt 3 specification is M9×1.25, the yield strength range is 940-1040MPa, the friction coefficient is 0.08-0.14, and the preload force target is the yield point of the bolt, the corresponding bolt 3 preload force range is 39.27- 46.73kN. The actual bolt 3 tightening safety factor of 1.79 meets the requirements, the contact stress of the cylinder head 1 pressure bearing surface and the cylinder head 1 bolt 3 gasket 4 pressure bearing surface all meet the requirements, and the selection of bolt 3 and the range of pre-tightening force are determined to meet the design requirements .

Example 3:

This embodiment is a practical embodiment of the present invention. In this embodiment, the calculation function of the EXCEL table is used to execute the method in the above-mentioned embodiment, that is, the formulas 1 to 8 are entered into the EXCEL table and correlated. When When the corresponding input value is input, the corresponding output value is obtained, so that the accuracy and efficiency of the calculation by the above method can be improved.

The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited to this. Any person skilled in the art can easily think of changes or substitutions within the technical scope of the present invention. should be included within the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

F _v =K×F _b (3)

Claims (10)

1. a gasoline engine cylinder head bolt type selection and checking method, is characterized in that, comprises: obtaining the maximum working load of the engine according to the maximum burst pressure of the engine; Obtain the maximum external load of a single bolt of the cylinder head according to the maximum working load of the engine; The pre-tightening force required by a single bolt to seal the cylinder head is determined according to a predetermined safety factor and the maximum external load of the single bolt, and the predetermined safety factor is determined according to the attenuation of the axial force during the use of the bolt ; Preliminarily select the bolt type and the gasket type according to the boundary conditions of the bolt assembly of the cylinder head and the pre-tightening force required by the single bolt to seal the cylinder head; The actual minimum preload force of the bolt is obtained according to the minimum yield strength and the maximum friction coefficient of the bolt corresponding to the selected bolt type, and the actual maximum preload of the bolt is obtained according to the maximum yield strength and the minimum friction coefficient of the bolt. tightness; Obtain the actual safety factor of the bolt according to the actual minimum pre-tightening force of the bolt and the maximum external load of the single bolt of the cylinder head, and compare the actual safety factor of the bolt with the predetermined safety factor; According to the actual maximum pre-tightening force of the bolts and the pressure bearing area between the cylinder head and the gasket, the contact stress of the bearing surface between the cylinder head and the gasket is obtained, and the cylinder head is connected to the gasket. Comparing the contact stress of the pressure bearing surface between the cover and the gasket and the allowable contact stress of the cylinder head manufacturing material; According to the actual maximum pre-tightening force of the bolt and the pressure-bearing area between the washer and the bolt head, the contact stress of the pressure-bearing surface between the washer and the bolt head is obtained, and the Compare the contact stress of the pressure-bearing surface between the gasket and the bolt head with the allowable contact stress of the gasket manufacturing material; When the actual safety factor is greater than the predetermined safety factor, and the contact stress of the pressure-bearing surface of the cylinder head and the gasket is less than the allowable contact stress of the cylinder head manufacturing material and the gasket and the gasket When the contact stress of the pressure-bearing surface where the bolt heads are connected is less than the allowable contact stress of the gasket manufacturing material, the selected bolt type is determined to be qualified. 2. a kind of gasoline engine cylinder head bolt type selection and checking method according to claim 1, is characterized in that: described engine maximum working load obtained according to described engine maximum burst pressure, is specifically: The maximum working load of the engine

The P _max is the maximum explosion pressure of the engine, and the d _g is the diameter of the cylinder head of the engine. 3. a kind of gasoline engine cylinder head bolt type selection and checking method according to claim 2, is characterized in that: the described maximum external load of cylinder head single bolt obtained according to described engine maximum working load, is specifically: The maximum external load of the single bolt of the cylinder head

4. The method for selecting and checking the type of cylinder head bolts of a gasoline engine according to claim 3, characterized in that: the single bolt is determined according to a predetermined safety factor and the maximum external load of the single bolt to make the The preload required for the cylinder head seal, specifically: The pre-tightening force F _v =K×F _b required by the single bolt to seal the cylinder head, where K is a predetermined safety factor of the bolt. 5 . The method for selecting and checking bolts of a gasoline engine cylinder head according to claim 4 , wherein the predetermined safety factor K of the bolts ranges from 1.6 to 1.8. 6 . 6 . The method for selecting and checking the type of cylinder head bolts of a gasoline engine according to claim 5 , characterized in that: according to the minimum yield strength and the maximum friction coefficient of the bolts corresponding to the selected bolt types, the described The actual minimum preload force of the bolt, specifically: Actual minimum preload of the bolts

The actual maximum pre-tightening force of the bolt is obtained according to the maximum yield strength and the minimum friction coefficient of the bolt, specifically: Actual maximum preload of said bolts

The v is the yield strength utilization coefficient of the bolt, the R _P0.2max is the maximum yield strength of the bolt, the R _P0.2min is the minimum yield strength of the _bolt , and the As is the The nominal stress cross-sectional area of the external thread of the bolt, the d ₂ is the pitch diameter of the bolt's thread, the d ₀ is the equivalent diameter of the nominal stress cross-sectional area of the external thread of the bolt, and the α' is the thread of the bolt flank angle, the μ _smin is the minimum friction coefficient of the bolt thread, the μ _smax is the maximum friction coefficient of the bolt thread, and the P is the thread pitch of the bolt. 7 . The method for selecting and checking the type of cylinder head bolts of a gasoline engine according to claim 6 , wherein the cylinder head is made according to the actual minimum pre-tightening force of the bolts and the single bolt. 8 . The preload required for sealing to obtain the actual safety factor of the bolt, specifically: Actual safety factor of said bolts

8 . The method for selecting and checking the type of cylinder head bolts of a gasoline engine according to claim 7 , wherein: the actual maximum pre-tightening force of the bolts and the relationship between the cylinder head and the gasket are as follows. 9 . The pressure-bearing area between the cylinder head and the gasket is obtained to obtain the contact stress of the pressure-bearing surface of the cylinder head and the gasket, specifically: The contact stress of the pressure bearing surface where the cylinder head and the gasket are connected

The _AC is the pressure bearing area between the cylinder head and the gasket. 9 . The method for selecting and checking the type of cylinder head bolts of a gasoline engine according to claim 8 , wherein: the actual maximum pre-tightening force of the bolt and the gasket and the head of the bolt are as follows: 10 . The pressure-bearing area between the gasket and the bolt head is obtained by obtaining the contact stress of the pressure-bearing surface, which is specifically: The contact stress of the bearing surface where the gasket is connected to the head of the bolt

The _Ad is the pressure bearing area between the gasket and the bolt. 10. A gasoline engine cylinder head bolt type selection and checking method according to any one of claims 1-9, characterized in that: execute the method described in any one of claims 1-9 in an EXCEL table method.

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