CN112699499B - Gasoline engine flywheel bolt type selection and check method - Google Patents
Gasoline engine flywheel bolt type selection and check method Download PDFInfo
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- CN112699499B CN112699499B CN202011240059.XA CN202011240059A CN112699499B CN 112699499 B CN112699499 B CN 112699499B CN 202011240059 A CN202011240059 A CN 202011240059A CN 112699499 B CN112699499 B CN 112699499B
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- G06F2119/14—Force analysis or force optimisation, e.g. static or dynamic forces
Abstract
The invention relates to a gasoline engine flywheel bolt type selection and checking method, which belongs to the technical field of vehicle manufacturing, the method provided by the application calculates the total torque borne by a flywheel through the static torque and the dynamic torque borne by the flywheel, obtains the pretightening force required to be applied to the flywheel by a single bolt on the flywheel through calculation, determines a preset safety factor according to the attenuation of axial force, finally simplifies the pretightening force to enable the flywheel to be fastened with a crankshaft by the single bolt, then carries out forward type selection on the bolt, accurately obtains the actual maximum pretightening force and the actual minimum pretightening force calculation by considering the specification, the size, the friction coefficient dispersion, the yield strength dispersion and the actual situation of the bolts among multiple batches in a mass production state, and finally carries out checking, can accurately carry out forward type selection on the gasoline engine flywheel bolt, is simpler and more convenient and perfect, the selected bolt can better meet the actual running condition of the gasoline engine.
Description
Technical Field
The invention belongs to the technical field of vehicle manufacturing, and particularly relates to a method for selecting and checking a flywheel bolt of a gasoline engine.
Background
When the vehicle engine runs, the torque converted by acting in the cylinder is transmitted to the vehicle by connecting the flywheel with the gearbox, and the flywheel is tightly connected to the rear end face of the crankshaft through the flywheel bolt. The flywheel bolt is screwed down to generate uniform and proper axial pretightening force to the flywheel, and static friction force is generated between the joint surface of the flywheel and the crankshaft, so that the flywheel and the crankshaft do not generate relative displacement all the time, and the stable torque output of the engine is ensured. The flywheel bolt needs sufficient strength and rigidity to overcome the output torque of the engine in high-speed operation and the transverse load generated by the dynamic torsional vibration torque of a crankshaft system, otherwise faults such as loosening of the flywheel and twist-off of the crankshaft, serious damage to the engine and the like easily occur, and therefore the flywheel bolt belongs to a key bolt of the engine.
However, in the prior art, the design method of the flywheel bolt is not perfect, so that the flywheel bolt has safety risk in the use process.
Disclosure of Invention
The invention provides a gasoline engine flywheel bolt type selection and checking method, which is used for solving the technical problem that safety risks exist in the use process of a flywheel bolt due to the fact that a flywheel bolt design method in the prior art is not complete.
The invention is realized by the following technical scheme: a gasoline engine flywheel bolt type selection and check method comprises the following steps:
obtaining the total torque borne by the flywheel according to the static torque and the dynamic torque borne by the flywheel;
obtaining the minimum static friction force required by fastening the flywheel according to the total torque borne by the flywheel;
obtaining the pretightening force which is required to be applied to the flywheel by a single bolt on the flywheel according to the minimum static friction force required by fastening the flywheel;
obtaining the pretightening force for fastening the flywheel and the crankshaft by the single bolt according to the pretightening force which is required to be applied to the flywheel by the single bolt on the flywheel and a preset safety coefficient, wherein the preset safety coefficient is determined according to the attenuation of the axial force in the use process of the bolt;
preliminarily selecting the type of the bolt according to the pretightening force for fastening the flywheel and the crankshaft by the single bolt and the bolt assembling boundary condition on the flywheel;
in a mass production state of the combined bolts, the parameters of the bolts in multiple batches have dispersion, the actual minimum pretightening 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 model, and the actual maximum pretightening force of the bolt is obtained according to the maximum yield strength and the minimum friction coefficient of the bolt;
obtaining an actual safety coefficient of the bolt according to the actual minimum pretightening force of the bolt and the pretightening force which needs to be applied to the flywheel by a single bolt on the flywheel, and comparing the actual safety coefficient with the preset safety coefficient;
obtaining the contact stress of the pressure bearing surface of the flywheel, which is connected with the bolt head, according to the actual maximum pretightening force of the bolt and the pressure bearing area between the flywheel and the bolt head, and comparing the contact stress of the pressure bearing surface of the flywheel, which is connected with the bolt head, with the allowable contact stress of the manufacturing material of the flywheel;
and when the actual safety factor is greater than the preset safety factor and the contact stress of the pressure bearing surface of the flywheel, which is connected with the head of the bolt, is smaller than the allowable contact stress of the manufacturing material of the flywheel, determining that the selected bolt model is qualified.
Further, in order to better implement the present invention, the obtaining of the total torque borne by the flywheel according to the static torque and the dynamic torque borne by the flywheel specifically includes:
total torque M borne by the flywheel a ＝M T +M S Said M is T For static torque experienced by the flywheel, said M S Dynamic torque to which the flywheel is subjected, and M S ＝N×M T And the N is determined by shafting torsional vibration simulation analysis.
Further, in order to better implement the present invention, the minimum static friction force required for fastening the flywheel is obtained according to the total torque borne by the flywheel, specifically:
minimum static friction force required for fastening the flywheel
And r is the distance between the shaft axis of a single bolt and the shaft axis of the flywheel.
Further, in order to better implement the present invention, the pre-tightening force that needs to be applied to the flywheel by a single bolt on the flywheel is obtained according to the minimum static friction force required for fastening the flywheel, and the pre-tightening force is specifically:
the pretightening force of the flywheel needs to be applied to the single bolt on the flywheel
And n is the number of bolts used for fastening the flywheel and the crankshaft, and mu is the friction coefficient of the joint surface of the flywheel and the crankshaft.
Further, in order to better implement the present invention, the pre-tightening force that the single bolt fastens the flywheel and the crankshaft is obtained according to the pre-tightening force that the single bolt on the flywheel needs to apply to the flywheel and a predetermined safety factor, specifically:
pretightening force F for fastening the flywheel and the crankshaft by the single bolt v ＝K×F μ And K is a preset safety factor of the bolt.
Further, in order to better implement the present invention, the predetermined safety factor K of the bolt is 1.3.
Further, in order to better implement 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 model, which specifically includes: actual minimum pretension of the bolt
The actual maximum pretightening force of the bolt is obtained according to the maximum yield strength and the minimum friction coefficient of the bolt, and the method specifically comprises the following steps:
actual maximum pre-tightening force of the bolt
V is a yield strength utilization coefficient of the bolt, R P0.2max Is the maximum yield strength of the bolt, said R P0.2min Is the minimum yield strength of the bolt, said A s Is the nominal stress cross-sectional area of the external thread of the bolt, d 2 Is the pitch diameter of the thread of the bolt, d 0 Is the nominal stress cross-sectional area equivalent diameter of the external thread of the bolt, the alpha' is the thread flank angle of the bolt, and the mu smin Is the minimum coefficient of friction of the screw thread, mu smax And P is the maximum friction coefficient of the screw thread of the bolt, and the pitch of the bolt.
Further, in order to better implement the present invention, the actual safety factor of the bolt is obtained according to the actual minimum pretightening force of the bolt and the pretightening force which needs to be applied to the flywheel by a single bolt on the flywheel, specifically:
the actual safety factor
Further, in order to better implement the present invention, the obtaining of the contact stress of the bearing surface where the flywheel is connected with the bolt head according to the actual maximum pre-tightening force of the bolt and the bearing area between the flywheel and the bolt head specifically includes:
contact stress of the flywheel and the bearing surface connected with the head of the bolt
A is described C The bearing area of the flywheel connected with the bolt head is provided.
Further, to better implement the present invention, the above-described method is performed in an EXCEL form.
Compared with the prior art, the invention has the following beneficial effects:
the invention provides a gasoline engine flywheel bolt type selection and checking method, which comprises the steps of calculating the total torque borne by a flywheel through the static torque and the dynamic torque borne by the flywheel, then calculating the minimum static friction force required by flywheel fastening according to the total torque borne by the flywheel, converting the minimum static friction force required by flywheel fastening into the pretightening force required by a single bolt on the flywheel to be applied to the flywheel, simplifying a stress model, improving the design safety margin, fully considering the axial force attenuation in the use process of the bolt in the design process to determine the preset safety coefficient, calculating the pretightening force required by the single bolt on the flywheel to fasten the flywheel and a crankshaft by combining the pretightening force required by the single bolt on the flywheel, carrying out forward type selection on the flywheel bolt according to the bolt assembly boundary condition on the flywheel and the pretightening force required by the single bolt to fasten the flywheel and the crankshaft so as to determine the bolt type selection direction, the blind trial of bolts of various types is avoided, the working efficiency is improved, after the bolts are preliminarily selected, the actual minimum pretightening force and the actual maximum pretightening force of the selected bolts are calculated, in the process, the dispersion of key parameters, such as yield strength and friction coefficient, of the selected bolts in the mass production state is fully considered, the actual maximum pretightening force and the actual minimum pretightening force of the bolts are accurately calculated by combining the specifications and actual conditions of the bolts, for example, the yield strength utilization coefficient is determined according to the bolt tightening mode, the actual safety coefficient of the selected bolts is determined by utilizing the actual minimum pretightening force of the selected bolts and the pretightening force which needs to be applied to the flywheel by a single bolt on the flywheel, the actual safety coefficient of the selected bolts is compared with the estimated safety coefficient, when the actual safety coefficient is less than or equal to the estimated safety coefficient, the bolts are reselected, when the actual safety factor is larger than the estimated safety factor, the bolt is qualified, then the contact stress of the pressure-bearing surface connected with the head part of the flywheel and the head part of the bolt is calculated according to the ratio of the actual maximum pretightening force and the pressure-bearing area of the selected bolt, and the calculated contact stress of the pressure-bearing surface connected with the head part of the flywheel and the allowable contact stress of the manufacturing material of the flywheel are compared, so that whether the bolt type selection meets the allowable contact stress of the manufacturing material of the flywheel is verified, and the selected bolt meets the requirements can be ensured. The probability of safety problems in the use process of the flywheel bolt is reduced.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
FIG. 1 is a flow chart of a gasoline engine flywheel bolt type selection and verification method of the present application;
FIG. 2 is a schematic view of a flywheel mounting arrangement of the present application;
FIG. 3 is a side view of the flywheel mounting arrangement of the present application;
FIG. 4 is a table illustrating an exemplary process for determining the preload force for tightening the flywheel and crankshaft with a single bolt according to the present application;
FIG. 5 is a table illustrating exemplary bolt sizing and actual maximum pretension and actual minimum pretension calculation processes in the present application;
fig. 6 is a table illustrating an example of a bolt checking process in the present application.
In the figure:
1-a flywheel; 2-bolt; 3-a crankshaft; 4-crank connecting rod; 5-piston.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be described in detail below. It is to be understood that the described embodiments are merely exemplary of the invention, and not restrictive of the full scope of the invention. All other embodiments, which can be derived by a person skilled in the art from the examples given herein without any inventive step, are within the scope of the present invention.
Example 1:
the embodiment provides a gasoline engine flywheel bolt type selection and checking method, which is used for solving the technical problem that safety risks exist in the use process of a flywheel bolt due to the fact that a flywheel bolt design method in the prior art is not complete. In particular, in the existing method for designing the engine flywheel bolt, the actual conditions of the friction coefficient dispersion, the yield strength dispersion, the specification, the size and the like of the bolt are not considered, and most of the bolts with different specifications are selected in a trial and error mode during model selection, so that the pretightening force of the selected bolt cannot meet the requirement due to the reasons, and the model selection and the checking process are complex and prone to error, so that the selected bolt has a large safety risk during use.
The gasoline engine flywheel bolt type selection and checking method comprises the following steps:
step 1.1: as shown in fig. 2 and 3, when the engine is running, the torque converted from work in the cylinder is transmitted to the vehicle through the flywheel 1 connected with the gearbox. However, since the crankshaft 3 is made of a material having a certain inertia and elasticity and has a certain natural frequency, when the engine is running, the reciprocating inertia force acting on the piston 5 due to the explosion pressure in the cylinder, the rotational inertia force and gravity of the crank connecting rod 4, and the irregular resistance torque and the external reaction force of the accessory system all generate the excitation torque on the crankshaft 3, and when the excitation frequency is the same as the fixed frequency of the crankshaft 3 itself, the crankshaft 3 resonates, so that the flywheel 1 needs to bear not only the static torque of the engine (i.e., the rated torque of the engine) but also the dynamic torque generated by the torsional vibration of the crankshaft 3. Sufficient pretightening force needs to be applied to the bolts 2 of the flywheel 1 to overcome the static torque and the dynamic torque, otherwise, the flywheel 1 and the crankshaft 3 are loosened, and serious engine faults are caused.
The total torque to which the flywheel 1 is subjected is therefore the static torque mentioned aboveAfter the dynamic torque and the dynamic torque, passing through M a ＝M T +M S (formula 1) wherein M is a For the total torque to which the flywheel 1 is subjected, M T For the static torque (i.e. the engine rated torque) to which the flywheel 1 is subjected, M S The dynamic torque borne by the flywheel 1 can be determined through shafting torsional vibration simulation analysis, or the dynamic torque borne by the flywheel 1 can be determined to be N times of the static torque, namely M according to experience S ＝N×M T (equation 2), it can be known from experience that N is 6 for a three-cylinder gasoline engine and 5 for a four-cylinder gasoline engine, and the above experience can be used for quick verification in bolt calculation.
Step 1.2: according to the total torque M borne by the flywheel 1 a The minimum static friction force required by fastening the flywheel 1 is obtained, because the flywheel 1 needs to be fixed relative to the rear end of the crankshaft 3, namely, the flywheel 1 is tightly pressed by the bolt 2, the disc surface of one side of the flywheel 1 close to the crankshaft 3 is tightly attached to the rear end surface of the crankshaft 3 to generate a large friction force, and the friction force enables the flywheel 1 to be fixed relative to the rear end of the crankshaft 3. In particular, the minimum static friction force required for the fastening of the flywheel 1
Wherein r is the distance between the axial lead of the single bolt 2 and the axial lead of the flywheel 1. It should be noted that the minimum static friction force to be fastened by the flywheel 1 obtained by the equation 3 is the friction force generated between the flywheel 1 and the crankshaft 3 by pressing the flywheel 1 together with all the bolts 2 on the flywheel 1 for fastening with the crankshaft 3.
Step 1.3: according to F obtained in step 2 b And the pretightening force which needs to be applied to the flywheel 1 by the single bolt 2 is obtained by combining the number n of the bolts 2 arranged on the flywheel 1. It is to be noted that the effect of the bolts 2 on the flywheel 1 is related to the arrangement of the bolts 2, i.e. the position of the bolts 2 from the center of the crankshaft 3, but all the bolts 2 are distributed on the flywheel 1 in a circumferential array centered on the center of the flywheel 1. Thus, a single bolt 2 requires a preload force to be applied to the flywheel 1
Wherein mu is the friction coefficient of the combining surface of the flywheel 1 and the crankshaft 3. Through the steps, the stress model is simplified, so that the calculation process is simplified, the design accuracy is improved, and the design safety margin can be improved.
Step 1.4: due to the fact that unevenness and roughness exist on the microscopic surfaces of the flywheel 1 and the crankshaft 3, the bolt 2 is embedded into a joint surface after being assembled and screwed down, and the bolt 2 is loosened; and during the operation of the engine, the material creep thinning of the bolt 2 and the connected piece is caused to attenuate the axial force due to long-time mechanical and heat exchange load, thereby determining a safety factor K and passing F v ＝K×F μ (equation 5) Pretightening force for fastening the flywheel 1 and the crankshaft 3 by the single bolt 2 is obtained, namely, at least F is applied to the single bolt 2 v So that the frictional force between the flywheel 1 and the crankshaft 3 reaches F b . Thus, by setting the safety factor K in consideration of the attenuation of the axial force of the bolt 2 in the use process, the pretightening force for fastening the flywheel 1 and the crankshaft 3 by the single bolt 2 can be more compliant, the type selection of the bolt 2 is more accurate, and a sufficient safety margin is reserved. As a best mode for this embodiment, the value of K in this embodiment is 1.3.
It is noted that the single bolt 2 in steps 1.1 to 1.4 corresponds to the bolt assumed to meet the assembly requirements.
Step 2.1: according to the assembly boundary conditions of the bolts 2 on the flywheel and F v The model of the bolt is preliminarily selected, and the rated minimum pretightening force of the bolt 2 is larger than the pretightening force required by fastening the flywheel 1 and the crankshaft 3 by the single bolt 2
Calculating the actual minimum pretightening force of the bolt 2, wherein v in the formula 6 is the yield strength utilization coefficient of the bolt 2, and R P0.2min Is the minimum yield strength of the bolt 2, A s Is the nominal stress cross-sectional area, d, of the external thread of the bolt 2 2 Is the pitch diameter of the thread of the bolt 2, d 0 Is the nominal stress cross-sectional area equivalent diameter of the external thread of the bolt 2, alpha' is the thread flank angle of the bolt 2, mu smax Is the maximum coefficient of friction of the threads of the bolt 2,p is the pitch of the bolt 2. In the step, firstly, the specification and the size of the bolt 2 are determined according to the assembly boundary, namely, the bolt 2 is subjected to forward type selection, blind type selection among bolts of various types is avoided, the working efficiency is improved, and then the actual minimum pretightening force of the selected bolt 2 is calculated through the formula 6 and is matched with the F v A comparison is made to perform a preliminary model selection of the bolt 2. In this step, the actual minimum tightening force of the bolts 2 is determined more precisely in consideration of the specifications and dimensions of the bolts 2 themselves, the variation in friction coefficient, the variation in yield strength, and the specific conditions of use in mass production.
Step 2.2: according to
Calculating the actual maximum pretension force F of the bolt 2 Mmax Where v in formula 7 is the yield strength utilization coefficient of bolt 2, R P0.2max Maximum yield strength of bolt 2, A s Is the nominal stress cross-sectional area, d, of the external thread of the bolt 2 2 Is the pitch diameter of the thread of the bolt 2, d 0 Is the nominal stress cross-sectional area equivalent diameter of the external thread of the bolt 2, alpha' is the thread flank angle of the bolt 2, mu smin P is the minimum coefficient of friction of the thread of the bolt 2 and P is the pitch of the bolt 2. In this step, the actual maximum pre-tightening force of the bolts 2 determined more accurately in consideration of the specifications and sizes of the bolts 2 of different batches, the dispersion difference of friction coefficients, the dispersion difference of yield strengths and specific use conditions in a mass production state is fully considered, and it should be noted that, in the calculation process of the actual maximum pre-tightening force of the bolts 2, except for R, R is P0.2max And mu smin Except for the difference in the calculation of the minimum pretightening force, all other parameters are the same.
In step 2.1 and step 2.2, the maximum yield strength R of the bolt 2 is specified P0.2max And minimum yield strength R P0.2min Depending on the material batch and production process control, R is required P0.2max And R P0.2min Is within a specified range, and in one embodiment of this embodiment, R is P0.2max And R P0.2min The value range of the difference is within 100 MPa.
In addition, μ smax And mu smin Mainly depending on the bolt 2 surface treatment process. Specifically, when the surface of the bolt 2 is phosphated and then oiled, mu smax ＝0.14，μ smin 0.08; after the surface of the bolt 2 is blackened, oil is applied to the surface smax ＝0.16，μ smin ＝0.10。
Also, v in the expressions 6 and 7 depends on the specific tightening condition of the bolt 2, and when the bolt 2 is tightened in the elastic region, the yield strength utilization coefficient v of the bolt 2 ranges from 70% to 90%, and most preferably, in this case, the yield strength utilization coefficient v of the bolt 2 is 90%; when the bolt 2 is tightened in the plastic region, the yield strength utilization coefficient v of the bolt 2 ranges from 100% to 110%, and most preferably, the yield strength utilization coefficient v of the bolt 2 is 100%.
Therefore, the method provided by the invention fully considers the axial force attenuation of the bolt 2 in the process of selecting the type of the bolt 2 of the flywheel 1, and the parameters of the bolt 2, such as the bolt specification, the friction coefficient and the yield strength, of the bolts 2 among multiple batches have dispersion difference in the mass production state of the bolt 2, so that the pretightening force range of the bolt 2 is determined by combining the actual production state when the pretightening force is defined, the type selection of the bolt 2 is more accurate, and the probability of safety problems occurring in the use process of the bolt 2 of the flywheel 1 is reduced.
Step 3.1: obtaining the actual safety factor of the selected bolt 2 according to the actual minimum pretightening force of the selected bolt 2 and the pretightening force which needs to be applied to the flywheel 1 by the single bolt 2 on the flywheel 1
And comparing K ' with K, returning to the step 2.1 to perform model selection on the bolt 2 again when K ' is less than or equal to K, and judging that the model selection of the bolt 2 is qualified when K ' is greater than K. In this step, K' must be greater than K but as close as possible, otherwise, too much design margin occurs, resulting in material waste.
Step 3.2: by passing
Bearing for connecting calculating flywheel 1 and bolt 2 headContact stress sigma of press face c A in formula 9 C To the bearing area between the flywheel 1 and the head of the bolt 2, sigma is then adjusted c Compared with allowable contact stress of the material of which the flywheel 1 is made, at σ c When the allowable contact stress is smaller than that of the flywheel manufacturing material, the type selection of the bolt 2 is judged to be qualified, and the allowable contact stress is within the range of sigma c If the allowable contact stress is larger than or equal to the allowable contact stress of the manufacturing material of the bolt 2, the step 2.1 is returned to perform the model selection on the bolt 2 again.
In this embodiment, step 3.1 and step 3.2 may be performed simultaneously, i.e. alternately. As long as the selected bolt 2 can satisfy K' > K and σ at the same time c The two conditions of the allowable contact stress of the manufacturing material of the flywheel 1 are smaller, which indicates that the selected bolt 2 is qualified in model selection.
It should be noted that the above steps 1.1 to 1.4 are actually the process of determining the minimum assembly preload of the bolt 2 (i.e. the preload of the bolt 2 for fastening the flywheel 1 and the crankshaft 3), the steps 2.1 and 2.2 are the process of selecting the bolt 2 and calculating the actual maximum preload and the actual minimum preload, and the steps 3.1 and 3.2 are the process of checking the bolt 2. In addition, the bolt 2 in the steps 2.1 to 3.2 is a bolt with a selected model.
Specifically, when the bolt 2 is produced, the drawing definition of the bolt 2 is consistent with the key parameter definition, and the production control requirement of a supplier is restrained so as to produce the bolt meeting the drawing requirement.
Example 2:
example as an exemplary embodiment of example 1, the following:
step 1.1: given a certain engine rated torque of M T 220 Nm; according to input information such as explosion pressure of an engine, rotational inertia of a flywheel and a transmission driving part, rotational inertia of an outer ring of a torsional vibration damper, torsional rigidity and the like, the maximum torque M transmitted by torsional vibration of a crankshaft 3 system is obtained through simulation analysis calculation S 1100 Nm. The maximum torque M to which the flywheel 1 is subjected is therefore a ＝1320Nm。
Step 1.2: according to the arrangement boundary of the flywheel 1 and the crankshaft 3, the number n of the fixing bolts 2 of the flywheel 1 is confirmed to be 8, and the axis of the bolt 2 of the flywheel 1 rotates away from the crankshaft 3The pitch r of the axes (i.e., the axis of the flywheel 1) is 73mm, and the minimum static friction force F required for fastening the flywheel 1 can be calculated from equation 3 b ＝4.52KN。
Step 1.3: the flywheel 1 is made of 45# steel material, the crankshaft 3 is forged steel, the friction coefficient of the pressure bearing surface is checked to be 0.12, and the pretightening force F which needs to be applied to the flywheel 1 by the single bolt 2 can be obtained through the formula 4 μ ＝37.67kN。
Step 1.4: because of the existence of the axial force attenuation factor in the assembly process and the operation of the engine, the safety factor K of the pre-tightening force of the bolt 2 is 1.3, and the pre-tightening force F for fastening the flywheel 1 and the crankshaft 3 by the single bolt 2 can be obtained by the formula 5 v ＝48.97kN。
Step 2.1: according to the limit of the arrangement boundary of the bolts 2 of the flywheel 1, the specification of the bolts 2 is required to be less than or equal to M10, the bolts 2 need to play a role in fastening and sealing, therefore, fine threads are selected, namely the specification of the bolts 2 is M10, the diameter of the head of each bolt 2 is phi 16.5mm, the diameter of a bolt through hole in the flywheel 1 is phi 12mm, the yield strength range of the bolts 2 is determined to be 100MPa and the minimum yield strength is 940MPa according to the consistency of raw materials and production processes provided by suppliers, a phosphating surface treatment mode is selected according to the anti-corrosion requirement, in order to prevent the bolts 2 of the flywheel 1 from loosening, thread fastening glue is coated on the surfaces of the threads, according to the consistency of the surface treatment process fed back by the suppliers, the friction coefficient range of phosphating and glue coating is defined to be 0.08-0.14, R is defined, and the friction coefficient after phosphating and glue coating is 0.08-0.14 P0.2min 940MPa, the bolt 2 is screwed in a plastic region, the yield strength utilization coefficient v is set to 100%, and the actual minimum pretightening force, namely F, of the bolt 2 is calculated by the formula 6 Mmin 53.68KN, therefore, F of the initially selected bolt 2 Mmin Greater than F v 。
Step 2.2: calculating the actual maximum pretension force F of the bolt 2 according to equation 7 Mmax 63.52KN, wherein, mu smin Is 0.08, R P0.2max Is 1040 MPa.
Step 3.1: the actual safety factor K 'chosen was calculated according to equation 8 as 1.43, so K' > K.
Step 3.2: according to the confirmation of the arrangement boundary, the head of the bolt 2 and the pressure-bearing area A of the flywheel 1 C Is 100.73mm 2 Bolt 2 head and flyThe contact stress of the pressure-bearing surface of the wheel 1 is calculated by equation 9 to obtain σ c 630.65MPa, and meets the requirement of 900MPa of the maximum allowable stress limit of 45# steel which is the manufacturing material of the flywheel.
In conclusion, when the bolt specification M10 × 0, the yield strength range 940-1040MPa, the friction coefficient 0.08-0.14 and the pre-tightening force target are the bolt yield point, the corresponding pre-tightening force range 53.68-63.52kN of the bolt 2 is obtained. The actual tightening safety factor 1.43 of the bolt 2 meets the requirement, the pressure bearing surface of the flywheel 1 meets the requirement, and the model selection and the pretightening force range of the bolt 2 are judged to determine that the design requirement is met.
Example 3:
in this embodiment, as a practical embodiment of the present invention, the method in the above embodiment is executed by using the calculation function of the EXCEL table, that is, the equations 1 to 9 are input into the EXCEL table and correlated, and when corresponding input values are input, corresponding output values are obtained, so that the accuracy and efficiency of the calculation of the above method can be improved.
The above description is only for the specific embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present invention, and the changes or substitutions should be covered within the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the appended claims.
M a ＝M T +M S (1)
M S ＝N×M T (2)
F v ＝K×F μ (5)
Claims (10)
1. A gasoline engine flywheel bolt type selection and check method is characterized by comprising the following steps:
obtaining the total torque borne by the flywheel according to the static torque and the dynamic torque borne by the flywheel;
obtaining the minimum static friction force required by fastening the flywheel according to the total torque borne by the flywheel;
obtaining the pretightening force which is required to be applied to the flywheel by a single bolt on the flywheel according to the minimum static friction force required by fastening the flywheel;
obtaining the pretightening force for fastening the flywheel and the crankshaft by the single bolt according to the pretightening force which is required to be applied to the flywheel by the single bolt on the flywheel and a preset safety coefficient, wherein the preset safety coefficient is determined according to the attenuation of the axial force in the use process of the bolt;
preliminarily selecting the type of the bolt according to the pretightening force for fastening the flywheel and the crankshaft by the single bolt and the bolt assembling boundary condition on the flywheel;
obtaining the actual minimum pretightening force of the bolt according to the minimum yield strength and the maximum friction coefficient of the bolt corresponding to the selected bolt model, and obtaining the actual maximum pretightening force of the bolt according to the maximum yield strength and the minimum friction coefficient of the bolt;
obtaining an actual safety coefficient of the bolt according to the actual minimum pretightening force of the bolt and the pretightening force which needs to be applied to the flywheel by a single bolt on the flywheel, and comparing the actual safety coefficient with the preset safety coefficient;
obtaining the contact stress of the pressure bearing surface of the flywheel, which is connected with the bolt head, according to the actual maximum pretightening force of the bolt and the pressure bearing area between the flywheel and the bolt head, and comparing the contact stress of the pressure bearing surface of the flywheel, which is connected with the bolt head, with the allowable contact stress of the manufacturing material of the flywheel;
and when the actual safety factor is greater than the preset safety factor and the contact stress of the pressure bearing surface of the flywheel, which is connected with the head of the bolt, is smaller than the allowable contact stress of the manufacturing material of the flywheel, determining that the selected bolt model is qualified.
2. The gasoline engine flywheel bolt type selection and check method as defined in claim 1, wherein: the obtaining of the total torque borne by the flywheel according to the static torque and the dynamic torque borne by the flywheel specifically comprises:
total torque M borne by the flywheel a ＝M T +M S Said M is T Static torque to which the flywheel is subjected, M S Dynamic torque to which the flywheel is subjected, and M S ＝N×M T And the N is determined by shafting torsional vibration simulation analysis.
3. The gasoline engine flywheel bolt type selection and check method as defined in claim 2, wherein: obtaining the minimum static friction force required by fastening the flywheel according to the total torque borne by the flywheel, specifically:
minimum static friction force required for fastening the flywheel
And r is the distance between the shaft axis of a single bolt and the shaft axis of the flywheel.
4. The gasoline engine flywheel bolt type selection and check method as defined in claim 3, wherein: the method comprises the following steps of obtaining the pretightening force which is required to be applied to the flywheel by a single bolt on the flywheel according to the minimum static friction force required by fastening the flywheel, and specifically comprises the following steps:
the pretightening force of the flywheel needs to be applied to the single bolt on the flywheel
And n is the number of bolts used for fastening the flywheel and the crankshaft, and mu is the friction coefficient of the joint surface of the flywheel and the crankshaft.
5. The gasoline engine flywheel bolt type selection and check method as defined in claim 4, wherein: the method comprises the following steps of obtaining the pretightening force for fastening the flywheel and the crankshaft by using a single bolt according to the pretightening force required to be applied to the flywheel by the single bolt on the flywheel and a preset safety factor:
pretightening force F for fastening the flywheel and the crankshaft by the single bolt v ＝K×F μ And K is a preset safety factor of the bolt.
6. The gasoline engine flywheel bolt type selection and check method as defined in claim 5, wherein: the value of the preset safety factor K of the bolt is 1.3.
7. The gasoline engine flywheel bolt type selection and check method as defined in claim 6, wherein: the actual minimum pretightening 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 model, and the actual minimum pretightening force is specifically as follows:
actual minimum pretension of the bolt
The actual maximum pretightening force of the bolt is obtained according to the maximum yield strength and the minimum friction coefficient of the bolt, and the method specifically comprises the following steps:
actual maximum pre-tightening force of the bolt
V is a yield strength utilization coefficient of the bolt, R P0.2max Is the maximum yield strength of the bolt, R P0.2min Is the minimum yield strength of the bolt, said A s Is the nominal stress cross-sectional area of the external thread of the bolt, d 2 Is the pitch diameter of the thread of the bolt, d 0 Is the nominal stress cross-sectional area equivalent diameter of the external thread of the bolt, the alpha' is the thread flank angle of the bolt, and the mu smin Is the minimum coefficient of friction of the screw thread, mu smax And P is the maximum friction coefficient of the screw thread of the bolt, and the pitch of the bolt.
8. The gasoline engine flywheel bolt type selection and check method as defined in claim 7, wherein: according to the actual minimum pretightning force of bolt and the pretightning force that single bolt need apply for the flywheel on the flywheel obtains the actual factor of safety of bolt, specifically do:
the actual safety factor
9. The gasoline engine flywheel bolt type selection and check method as defined in claim 8, wherein: the method for obtaining the contact stress of the bearing surface, connected with the bolt head, of the flywheel according to the actual maximum pretightening force of the bolt and the bearing area between the flywheel and the bolt head comprises the following steps:
contact stress of the flywheel and the bearing surface connected with the head of the bolt
A is described C The bearing area of the flywheel connected with the bolt head is provided.
10. The gasoline engine flywheel bolt type selecting and checking method according to any one of claims 1-9, characterized in that: performing the method of any one of claims 1-9 in an EXCEL form.
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