Monoblock pump cam box connecting bolt strength calculation method

Abstract

According to the method for calculating the strength of the connecting bolt of the cam box of the monoblock pump, the strength of the connecting bolt is calculated and evaluated by combining a one-dimensional simulation model and a finite element method, and the one-dimensional simulation model is used for providing an accurate load as input; meanwhile, the relative rigidity of the bolts and the box body can be accurately considered by utilizing a finite element method, and calculation and extraction of different types of stress of the bolt group under a complex assembly structure are realized, so that the stress calculation accuracy of the connecting bolts is greatly improved; and the difficulty that the calculation is difficult due to unknown input parameters and complex structure or the result error is too large due to excessive simplification in the traditional calculation based on a simplified formula is overcome.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of cam box connecting bolt strength calculation, and particularly relates to a single pump cam box connecting bolt strength calculation method. BACKGROUND

[0002] The single pump is still one of the mainstream technical routes of the current diesel fuel injection system, especially for marine or high-power diesel engines, each cylinder is matched with a single pump to supply fuel. The single pump itself does not contain a camshaft or a cam, and relies on the camshaft on the diesel engine to drive the plunger to complete the fuel pumping. During the factory test of the single pump, in order to simulate its working state on the diesel engine, a special cam box is generally used for testing. The cam box is usually installed on the test platform and connected and fastened by bolts. In order to facilitate hole processing, the connecting bolts are usually arranged on the bottom of both sides of the cam box along the axial direction of the camshaft.

[0003] Since the strength of the connecting bolt is crucial, its fracture failure may cause the displacement of the cam box, directly affecting the factory test of the single pump and even causing a series of accidents including damage to the test equipment. Due to the unique working process of the single pump, the stress condition of the connecting bolt is relatively complex, and it is difficult to provide the load for calculation by using the traditional formula calculation method, so it is difficult to calculate the bolt strength, and of course it cannot guide the selection of the bolt and the establishment of the torque parameter. SUMMARY

[0004] In view of the problems existing in the prior art, the present application provides a single pump cam box connecting bolt strength calculation method to solve the technical problems in the prior art that due to the unique working process of the single pump, the stress condition of the connecting bolt is relatively complex, it is difficult to provide the load for calculation by using the traditional formula calculation method, so it is difficult to calculate the bolt strength, and of course it cannot guide the selection of the bolt and the establishment of the torque parameter.

[0005] The present application provides a single pump cam box connecting bolt strength calculation method, comprising:

[0006] S1, according to the structure of the pump assembled in the cam box, a one-dimensional simulation model including at least a cam and a single pump is built;

[0007] S2, based on the one-dimensional simulation model, the plunger cavity hydraulic pressure, the spring force of the plunger spring and the inertia force of the moving part are extracted and calculated respectively, and the resultant force of the plunger cavity hydraulic pressure, the spring force of the plunger spring and the inertia force of the moving part is calculated;

[0008] S3, according to the cam angle-lift data and the geometric structure parameters of the cam, the pressure angle size is calculated;

[0009] S4, calculating the contact force and its components in the coordinate system based on the pressure angle and the resultant force;

[0010] S5, calculating the force on the bearing and the force on the hole in the mounting seat based on the contact force and the cam mounting position in the cam box;

[0011] S6, creating a three-dimensional finite element model including at least the upper body of the cam box, the lower body of the cam box, the mounting seat and the connecting bolt, loading the force, performing finite element calculation including the cam box and the connecting bolt, and outputting the finite element calculation result;

[0012] S7, based on the finite element calculation result, respectively carrying out static strength reliability evaluation and fatigue strength evaluation of the connecting bolt.

[0013] Optionally, the plunger cavity hydraulic pressure, the spring force of the plunger spring and the inertial force of the moving part are extracted and calculated respectively, and the resultant force of the plunger cavity hydraulic pressure, the spring force of the plunger spring and the inertial force of the moving part is calculated, comprising:

[0014] The plunger cavity hydraulic pressure, the spring force of the plunger spring, the inertial force of the moving part and the resultant force are calculated:

[0015]

[0016] Wherein, F h is the resultant force, F p is the plunger cavity hydraulic pressure, F s is the spring force of the plunger spring, F g is the inertial force of the moving part, d is the plunger diameter, P is the plunger cavity pressure, F i is the spring force of the plunger spring under the first load, k is the spring stiffness, H is the plunger lift, m v is the mass of the moving part, and a is the acceleration of the moving part.

[0017] Optionally, the contact force and its components in the coordinate system are calculated, comprising:

[0018] The contact force F T is calculated as:

[0019]

[0020] The direction of the cam shaft axis in the cam box is taken as the Z axis, and the outward direction when the cam rotates clockwise is taken as the positive direction. The vertical upward direction is taken as the Y axis positive direction, and then the X axis direction is determined by the right hand rule. The components are calculated as:

[0021]

[0022] Wherein, the subscript x(y,z) represents the component along the coordinate axis X(Y,Z).

[0023] Optionally, the calculating the contact force and its components in the coordinate system further comprises:

[0024] At least the intersection of the force growth segment and the pressure angle curve and the maximum point of the force are calculated respectively, and are brought into steps S5-S7 for static strength reliability evaluation of the connecting bolt.

[0025] Optionally, the solving the force on the bearing and the force on the hole in the mounting seat based on the contact force and the cam installation position in the cam box comprises:

[0026] S51, measure the distance values at 1 / 2 of the cam width and 1 / 2 of the bearing width at the left and right ends respectively, and express the ratio of the two distance values as 1:k respectively;

[0027] S52, calculating the contact force and the cam installation position in the cam box to solve the force on the bearing, wherein the force component of the left end bearing is the contact force component multiplied by the coefficient k / 1+k, and the force component of the right end bearing is the contact force component multiplied by the coefficient 1 / 1+k;

[0028] S53, the force on the hole in the mounting seat is equal to the component in the coordinate system, and the force on the hole in the mounting seat is opposite to the component in the coordinate system.

[0029] Optionally, the loading the force, performing finite element calculation including the cam box and the connecting bolt, and outputting the finite element calculation result, comprises:

[0030] The three-dimensional finite element model loads the corresponding force on the bearing mounting hole of the cam box and the hole in the mounting seat respectively, and includes at least two analysis steps, the first analysis step corresponds to the state of only applying bolt pretightening force on the connecting bolt, and the second analysis step corresponds to the state of applying the force on the bearing and the force on the hole in the mounting seat after applying the pretightening force on the connecting bolt, performing finite element calculation including the cam box and the connecting bolt, and outputting the finite element calculation result.

[0031] Optionally, the static strength reliability evaluation and fatigue strength evaluation of the connecting bolt are carried out based on the finite element calculation result, comprising:

[0032] S71, extracting the maximum tensile stress and the maximum bending stress on the connecting bolt in the second analysis step of the finite element calculation result, and performing static strength evaluation;

[0033] S72, extracting the maximum tensile stress and the maximum bending stress on the connecting bolt in the first analysis step and the second analysis step of the finite element calculation result respectively, and performing fatigue strength evaluation.

[0034] Optionally, the static strength evaluation comprises:

[0035]

[0036] wherein σ eq is the equivalent stress for evaluation, [σ] is the allowable stress, σ t2max is the maximum tensile stress on the connecting bolt in the second analysis step, σ b2max is the maximum bending stress on the connecting bolt in the second analysis step, R eL is the yield strength of the bolt material, S s is the safety factor.

[0037] Optionally, the fatigue strength evaluation comprises:

[0038]

[0039] wherein σ a is the stress amplitude, [σ a ] is the allowable stress amplitude σ t2max is the maximum tensile stress on the connecting bolt in the second analysis step, σ t1max is the maximum tensile stress on the connecting bolt in the first analysis step, σ b2max is the maximum bending stress on the connecting bolt in the second analysis step, σ b1max is the maximum bending stress on the connecting bolt in the first analysis step, d is the nominal diameter of the bolt.

[0040] Compared with the prior art, the present application has the following advantages:

[0041] The present application combines one-dimensional simulation model and finite element method to calculate and evaluate the strength of the connecting bolt, uses one-dimensional simulation model to provide accurate load as input, and uses finite element method to accurately consider the relative stiffness of the bolt and the box, realizes the calculation and extraction of different types of stress of the bolt set under complex assembly structure, greatly improves the accuracy of stress calculation of the connecting bolt, and gets rid of the difficulties of being difficult to calculate due to unknown input parameters and complex structure or too large result error due to oversimplification in traditional calculation based on simplified formula. BRIEF DESCRIPTION OF DRAWINGS

[0042] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and serve to explain the principles of the present application, together with the description.

[0043] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or prior art description will be briefly introduced as follows. Obviously, those drawings can also give other drawings based on the drawings without creative labor.

[0044] Figure 1 Flow chart of the method of the present application

[0045] Figure 2 Sectional view of the single pump installed on the cam box

[0046] Figure 3 Three-dimensional axonometric view of the single pump installed on the cam box in the present application Figure 2

[0047] Figure 4 Variation of the resultant force and pressure angle with the camshaft angle in the present application

[0048] Figure 5 Tensile stress nephogram of the connecting bolt in the first analysis step obtained by finite element calculation in the present application

[0049] Figure 6 Bending stress nephogram of the connecting bolt in the first analysis step obtained by finite element calculation in the present application

[0050] Figure 7 Tensile stress nephogram of the connecting bolt in the second analysis step obtained by finite element calculation in the present application

[0051] Figure 8 Bending stress nephogram of the connecting bolt in the second analysis step obtained by finite element calculation in the present application

[0052] Explanation of reference numerals:

[0053] 1, single pump; 11, plunger sleeve; 12, plunger; 13, plunger spring; 14, guide piston assembly; 101, plunger cavity; 141, roller pin; 142, roller; 2, cam box; 21, upper body of cam box; 22, lower body of cam box; 23, bearing; 24, end cover; 25, camshaft; 26, cam; 27, lubricating oil; 201, connecting bolt mounting hole; 30, mounting seat. DETAILED DESCRIPTION

[0054] ​To make the purposes, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some but not all of the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the scope of the present application. The functional units with the same and similar structures and functions having the same reference numerals in the embodiments of the present application have the same and similar structures and functions.

[0055] Referring to Figure 1 The present application provides a single pump 1 cam box 2 connecting bolt strength calculation method, comprising:

[0056] S1, according to the structure of the pump assembled in the cam box 2, a one-dimensional simulation model including at least cam 26 and single pump 1 is built;

[0057] S2, based on the one-dimensional simulation model, the plunger cavity 101 hydraulic pressure, the spring force of the plunger spring 13 and the inertia force of the moving part are extracted and calculated respectively, and the resultant force of the plunger cavity 101 hydraulic pressure, the spring force of the plunger spring 13 and the inertia force of the moving part is calculated;

[0058] S3, according to the cam 26 rotation angle-lift data and the geometric structure parameters of the cam, the pressure angle size is calculated;

[0059] S4, based on the pressure angle and the resultant force, the contact force size and its component in the coordinate system are calculated;

[0060] S5, based on the contact force size and the installation position of the cam 26 in the cam box 2, the force on the bearing 26 and the force on the hole in the mounting seat 30 are solved;

[0061] S6, a three-dimensional finite element model including at least cam box upper body 21, cam box lower body 22, mounting seat 30 and connecting bolt is created, and the force is loaded, the finite element calculation including cam box 2 and connecting bolt is carried out, and the finite element calculation result is output;

[0062] S7, based on the finite element calculation result, the static strength reliability evaluation and the fatigue strength evaluation of the connecting bolt are carried out respectively.

[0063] In the present embodiment, the connecting bolt strength calculation method is applicable to the cam box 2 of a single pump 1. In marine diesel engines or high-power diesel engines, a single pump 1 is usually used for fuel supply due to the large amount of fuel required per cycle and the large cylinder center distance of the engine. The single pump 1 is usually not integrated with a cam 26 or a cam shaft 25, so the out-of-factory test of the single pump 1 needs to be carried out on a customized cam box 25. In order to input power to the cam box 25 to drive the single pump 1 to run, the above process is usually carried out on a test bench, at this time, the cam box 25 needs to be fixed on the test bench by connecting bolts.

[0064] In order to better understand the method, please refer to Figure 2 As shown in Figure 3 , the single pump 1 is installed on the cam box 2, and the single pump 1 mainly includes a plunger sleeve 11, a plunger 12, a plunger spring 13, a guide piston assembly 14 and other components, wherein the guide piston assembly 14 includes a roller pin 141 and a roller 142, the roller 142 is sleeved on the roller pin 141, the plunger 12 is installed in the middle hole of the plunger sleeve 11, and the two form a plunger cavity 101. The upper body 21 of the cam box and the lower body 22 of the cam box are connected by bolts, the top of the upper body 21 of the cam box is provided with an opening, and the mounting seat 30 is nested by the end and locked on the upper body 21 of the cam box by screws; in other possible embodiments, the upper body 21 of the cam box and the mounting seat 30 can be an integrated structure. The middle of the mounting seat 30 is provided with an opening for installing the single pump 1, and the single pump 1 and the mounting seat 30 are also pre-tightened by screws. The cam shaft 25 is installed in the cam box 2 through the bearings 23 arranged at the left and right ends of the cam box 2, the cam 26 is installed on the cam shaft 25, and there is no relative movement between the two, and in other embodiments, the two can be an integral whole. The end cover 24 is installed at the end of the cam box 2, which usually plays a role in dustproof and leakage prevention.

[0065] When the single pump 1 carries out the out-of-factory test, the cam box 2 is placed on the test bench, the motor drives the cam shaft 25 to rotate by using a clutch (not shown in the figure), and then drives the cam 26 to rotate, drives the roller 142 to drive the guide piston assembly 14 and the plunger 12 to move up and down, at this time, with the opening and closing of the oil outlet valve assembly and other valve components in the single pump 1, the fuel in the plunger cavity 101 is periodically compressed and pumped out, therefore, the pressure in the plunger cavity 101 presents a periodic change. During the test, the cam box 2 is filled with lubricating oil 27 for lubrication and heat dissipation of the cam 26 and the roller 142. During the whole test process, the cam box 2 body is fixed in the connecting bolt mounting hole 201 by connecting bolts. In order to facilitate processing and installation, the connecting bolt mounting hole 201 is generally arranged on the left and right sides of the cam box 2 and distributed in the front and back directions. Therefore, the safety of the connecting bolt is very important to ensure the smooth progress of the test, and then the specific description is as follows:

[0066] S1, according to the structure of the pump assembled in the cam box 2, at least a one-dimensional simulation model including the cam 26 and the unit pump 1 is built;

[0067] For the mechanical fuel injection system, the unit pump 1 is connected with the high-pressure oil pipe and the injector to realize the complete function, therefore, the one-dimensional simulation model needs to be built together with the structural parameters of the high-pressure oil pipe, the injector and the like. For the common rail type fuel injection system, the function of the unit pump 1 is only to supply fuel to the high-pressure accumulator chamber, therefore, the one-dimensional simulation model can be built only by using the structural parameters of the unit pump 1 itself. Since the unit pump 1 usually does not contain the cam 26, regardless of the fuel injection system, the structural parameters of the cam 26 in the cam box 2, mainly including the cam angle-lift data of the cam 26, need to be combined when the one-dimensional simulation modeling is performed.

[0068] The pump in the embodiment is a mechanical unit pump 1, and the one-dimensional simulation model is built by using the structural parameters of the plunger 12, the plunger sleeve 11, the plunger spring 13, the cam 26 and the like in combination with the structural parameters of the associated parts such as the high-pressure oil pipe and the injector.

[0069] S2, based on the one-dimensional simulation model, the plunger cavity 101 hydraulic pressure, the spring force of the plunger spring 13 and the inertial force of the moving part are respectively extracted and calculated, and the resultant force of the plunger cavity 101 hydraulic pressure, the spring force of the plunger spring 13 and the inertial force of the moving part is calculated;

[0070] Referring to Figure 4 , the resultant force and the plunger cavity 101 hydraulic pressure and the like are calculated by formula (1):

[0071]

[0072] Wherein, F h is the resultant force, N; F p is the plunger cavity 101 hydraulic pressure, N; F s is the spring force of the plunger spring 13, N; F g is the inertial force of the moving part, N; d is the diameter of the plunger 12, mm; P is the plunger cavity 101 pressure, MPa; F i is the spring force of the plunger spring 13 at the first load, N, which is usually directly given in the plunger spring 13 design drawing; k is the spring stiffness, N / mm, which can also be obtained based on the plunger spring 13 design drawing; H is the plunger lift, mm; m v is the mass of the moving part, kg, including the mass of the guide piston assembly 14, the plunger 12 and 1 / 3 of the mass of the plunger spring 13, which can be obtained based on the part drawing; a is the acceleration of the moving part, N / m 2Based on the one-dimensional simulation model calculation, the plunger cavity 101 pressure P corresponding to the cam 26 rotation angle and the plunger 12 lift H can be directly extracted; a can be obtained by differentiating the velocity of the moving part.

[0073] S3, based on the cam 26 rotation angle-lift data and the cam 26 geometric structure parameters, the pressure angle size is calculated;

[0074] Generally, when the cam 26 structure design is determined, the corresponding follower lift data of different cam 26 rotation angles can be directly obtained on the product design drawing of the cam 26, and the pressure angle size and variation law of the cam 26 driving roller 142 in the movement process are calculated by combining the geometric structure parameters of the cam 26.

[0075] Referring to Figure 4 , the pressure angle is calculated according to formula (2):

[0076]

[0077] In the above formula, a represents the pressure angle, °; s represents the lift of the roller, mm, which is a function of the cam 26 rotation angle θ; R b represents the base circle radius of the cam 26, mm; e represents the eccentricity between the rotation center of the cam 26 and the roller motion track, mm. s'(θ) represents the motion speed of the roller, mm / s.

[0078] Preferably, s'(θ) is calculated by using two-point central difference formula (formula (3)) or four-point central difference formula (formula (4)). The accuracy of formula (4) is higher than that of formula (3).

[0079]

[0080] Wherein, s(θ i ) is the roller lift under the current i-degree cam 26 rotation angle, and h is the step length between the i-degree and i-1-degree cam 26 rotation angles.

[0081] S4, based on the pressure angle and the resultant force, the contact force size and its component in the coordinate system are calculated;

[0082] Based on the existing pressure angle and resultant force data, the size and direction of the contact force F T between the cam 26 and the roller 142 can be calculated. The contact force F

[0083]

[0084] The contact force F T The direction of the contact force F

[0085] In this embodiment, the camshaft 25 rotates clockwise when viewed from left to right during operation, see Figure 2 As shown, the axis direction of the camshaft 25 is the horizontal direction, which is the Z direction, and the vertical direction is the Y direction. At this time, the components of the X, Y, and Z axes are calculated by formula (6), where the subscript x(y, z) represents the component along the coordinate axis X(Y, Z). It should be noted that the orientation of the coordinate system will change the sign and direction of formula (6) to some extent.

[0086]

[0087] Preferably, at least two data points, the intersection of the resultant force growth segment and the pressure angle curve, and the maximum value point of the resultant force, are included in the calculation. The two data points need to be calculated separately and evaluated for strength reliability according to the subsequent steps.

[0088] S5, based on the contact force and the installation position of the cam 26 in the cam box 2, the force on the bearing and the force on the hole in the mounting seat 30 are solved;

[0089] S51: measure the distance between the 1 / 2 of the cam 26 width and the 1 / 2 of the bearing width at both ends, and calculate the ratio of the two.

[0090] Preferably, the ratio of the above two is simplified to the form of 1:k.

[0091] S52: based on the ratio of the two and the contact force component calculation result in S4, the force component on the cam box bearing 23 is calculated.

[0092] Specifically, for the left end bearing, the force component is the contact force component in S4 multiplied by the coefficient k / 1+k; for the right end bearing, the force component is the contact force component in S4 multiplied by the coefficient 1 / 1+k. The direction is the same as that of the contact force component in S4.

[0093] S53: according to the contact force component calculation result in S4, the force size and direction on the hole in the mounting seat 30 are obtained.

[0094] S52 is performed after S51, and the steps of S53 have no sequence relationship with S51 and S52.

[0095] The force on the hole in the mounting seat 30 is equal in size to the contact force component calculated in S4, and opposite in direction.

[0096] S6, create a three-dimensional finite element model including at least the cam box upper body 21, the cam box lower body 22, the mounting seat 30, and the connecting bolt, and load the force, perform finite element calculation including the cam box 2 and the connecting bolt, and output the finite element calculation result;

[0097] The three-dimensional finite element modeling is performed following the steps of geometry modeling, material definition, analysis step creation, meshing, boundary condition, etc., wherein:

[0098] Preferably, a three-dimensional finite element model is created for the cam box upper body 21, the cam box lower body 22 and the mounting seat 30.

[0099] Preferably, a beam element model is used to simulate the connecting bolt, and the cross-sectional size of the beam element is defined by the small diameter of the connecting bolt.

[0100] Preferably, a tie contact is used between the cam box upper body 21 and the cam box lower body 22, and between the mounting seat 30 and the cam box upper body 21.

[0101] Preferably, a mass point is set at the center of the top end of the mounting seat 30 and is given a mass equal to that of the single-body pump 11, and a mass point is set at the center of gravity of the cam box lower body 22 and is given a mass equal to the sum of the mass of the lubricating oil 27 and the masses of the cam shaft 25 and the cam 26.

[0102] Preferably, the finite element model comprises at least two analysis steps, the first analysis step corresponds to a state where only the bolt pretightening force is applied on the connecting bolt, and the second analysis step corresponds to a state where the bolt pretightening force is applied on the connecting bolt and then the forces on the bearing and the hole in the mounting seat 30 are applied, finite element calculation is performed for the cam box and the connecting bolt, and the finite element calculation result is output.

[0103] S7, based on the finite element calculation result, static strength reliability evaluation and fatigue strength evaluation of the connecting bolt are respectively carried out.

[0104] S71, the tensile stress on the connecting bolt due to the axial force and the bending stress due to the bending are respectively extracted, and static strength evaluation is performed.

[0105] Preferably, the static strength evaluation is performed according to formula (7):

[0106]

[0107] wherein σ eq is the equivalent stress for evaluation, MPa; [σ] is the allowable stress, MPa; σ t2max is the maximum tensile stress on the connecting bolt in the second analysis step in S6, MPa; σ b2max is the maximum bending stress on the connecting bolt in the second analysis step in S6, MPa; R eL is the yield strength of the bolt material, MPa; S s is the safety factor.

[0108] Preferably, S s is 1.2-1.5.

[0109] S72: extracting the tensile stress and the bending stress of the connecting bolt under the two analysis steps of only pre-tightening and applying the force component, calculating the stress amplitude and performing fatigue strength evaluation.

[0110] Preferably, the fatigue strength evaluation is performed according to formula (8):

[0111]

[0112] wherein σ a is the stress amplitude, MPa; [σ a ] is the allowable stress amplitude, MPa; σ t2max is the maximum tensile stress on the connecting bolt in the second analysis step in S6, MPa; σ t1max is the maximum tensile stress on the connecting bolt in the first analysis step in S6, MPa; σ b2max is the maximum bending stress on the connecting bolt in the second analysis step in S6, MPa; σ b1max is the maximum bending stress on the connecting bolt in the first analysis step in S6, MPa; and d is the nominal diameter of the bolt, mm.

[0113] It can be known from the embodiment that the connecting bolt strength is calculated and evaluated mainly by combining the one-dimensional simulation model and the finite element method, the one-dimensional simulation model is used to provide accurate load as input, the finite element method is used to more accurately consider the relative stiffness of the bolt and the box, the calculation and extraction of different types of stresses of the bolt set under the complex assembly structure are realized, the stress calculation accuracy of the connecting bolt is greatly improved, and the difficulty in calculation caused by unknown input parameters and complex structure or the large result error caused by oversimplification in the traditional calculation based on simplified formula is overcome.

[0114] In another embodiment, specific data are substituted for illustration, that is, the contact force size and its components in the coordinate system are calculated based on the pressure angle and the resultant force from S4:

[0115] Referring to Figure 4 , firstly, the resultant force and the pressure angle curve intersect at point A in the process of the resultant force increasing from small to large, the cam 26 angle at this time is θ1 and the pressure angle is α1; when the cam 26 angle is θ2, the pressure angle is α2, and the resultant force is the maximum value F hmax . This point is recorded as point B. Taking point B as an example, according to the maximum resultant force F hmax =251788N and the pressure angle α2=27.2° obtained after S1-S3 steps, the F T =283095N at point B is obtained, and further F Tx , F Ty , and FTz These are -129401N, -251788N, and 0, respectively. The negative sign indicates the negative direction along the current coordinate axis.

[0116] The same method was used to calculate the magnitude of the contact force at point A and its components in the coordinate system.

[0117] Secondly, S5, based on the magnitude of the contact force and the mounting position of the cam 26 in the cam box 2, solve for the force on the bearing and the force on the hole in the mounting seat 30:

[0118] Cam 26 is located in the center of bearing 23 (two bearings), meaning the distance from half the width of cam 26 to half the width of the left and right bearings is 1:1. Therefore, the force components on the left and right bearings are equal and half the contact force component in S4, which are -64700.5N, -125894N, and 0 (according to...). Figure 2 The X, Y, and Z directions in the coordinate system, where the negative sign indicates the negative direction of the coordinate axis (the same applies below);

[0119] The magnitudes of the forces acting on the holes in the mounting base 30 are 129401N, 251788N, and 0;

[0120] S6. Create a three-dimensional finite element model that includes at least the upper body 21 of the cam box, the lower body 22 of the cam box, the mounting base 30, and the connecting bolts. Apply the applied force, perform finite element calculations including the cam box 2 and the connecting bolts, and output the finite element calculation results:

[0121] Coordinate system orientation in finite element model Figure 2 With the coordinate system aligned, finite element modeling was performed using ANSYS software, focusing on the upper cam box 21, lower cam box 22, and mounting base 30. In this model, beam elements were used to simulate the connection between the connecting bolts and the countersunk portion of the bolt mounting hole 201 to the test bench. The test bench was modeled using a simplified approach. The beam element cross-sectional dimensions were set according to the designed bolt minor diameter of 14.37 mm. The upper body 21 and lower body 22 of the cam box are in bonded contact, as are the mounting base 30 and the upper body of the cam box 2. The force components applied at the bearing mounting hole of the lower body 22 of the cam box are -64700.5N, -125894N, and 0, respectively. The force components applied at the hole of the mounting base 3 are 129401N, 251788N, and 0, respectively. A mass point is set at the top center of the mounting base 30 and given a mass equal to that of the unit pump 1. A mass point is set at the center of gravity of the lower body 22 of the cam box and given a mass equal to the sum of the masses of the lubricating oil 27, camshaft 25, and cam 26. The sum of the masses of the upper body 21, lower body 22, mounting base 30, and the two mass points is 1200kg.

[0122] Finally, S7, based on the finite element calculation results, respectively, to carry out the static strength of the connecting bolt reliability assessment and fatigue strength assessment.

[0123] Step S71 can be extracted from Figure 7 With Figure 8 σ t2max = 236.99 MPa, σ b2max = 77.286 MPa, the equivalent stress σ eq = 389.273 MPa. According to the material of the connecting bolt, it is known that its yield strength R eL = 900 MPa, take the safety factor S s = 1.5, so the allowable stress [σ] is 600 MPa. Since σ eq = 389.273 MPa < [σ] = 600 MPa, so the static strength of the connecting bolt at this data point (see Figure 4 B point in the figure) is qualified.

[0124] Step S72 can be extracted from Figures 5 to 8 σ t1max = 207.39 MPa, σ b1max = 59.603 MPa, and the nominal diameter d of the connecting bolt is 16 mm, so σ a = 28.08 MPa < [σ a ] = 46 MPa, so the fatigue strength of the connecting bolt at this data point is qualified.

[0125] From the above specific examples, it can be seen that the strength of the connecting bolt of all data points in S4 is qualified, and it is considered that the strength of the connecting bolt meets the design requirements. The foregoing has calculated B point, and in this embodiment, the strength of the connecting bolt of A point is also calculated according to the steps of S4-S7 (the specific process is omitted), and the results show that the static strength and fatigue strength of the connecting bolt at A point are also qualified, so the strength of the connecting bolt used in the cam box 2 of the single pump 1 in this embodiment meets the requirements.

[0126] It has to be noted that, in the present document, relational terms are intended only to convey a possible relationship between elements or

[0127] The above description is merely that of the specific embodiments of the application and as such is not to be taken in a limiting sense, as the specific embodiments merely exemplify the general principles of the application. Certain modifications to the specific embodiments disclosed above can be apparent to one skilled in the art with the benefit of the present disclosure, and as such, should be within the purview of the application defined by the following claims, and their equivalents.

Claims

1. A method for calculating the strength of connecting bolts in a single-unit pump cam box, characterized in that, include: S1. Based on the structure of the pump assembled in the cam box, build a one-dimensional simulation model that includes at least the cam and the individual pump. S2. Based on the one-dimensional simulation model, extract and calculate the plunger cavity fluid pressure, the spring force of the plunger spring, and the inertial force of the moving parts, and calculate the resultant force of the plunger cavity fluid pressure, the spring force of the plunger spring, and the inertial force of the moving parts. S3. Calculate the pressure angle based on the cam's rotation angle-lift data and the cam's geometric parameters; S4. Based on the pressure angle and the resultant force, calculate the magnitude of the contact force and its components in the coordinate system; S5. Based on the magnitude of the contact force and the cam mounting position in the cam box, solve for the force on the bearing and the force on the hole in the mounting seat; S6. Create a three-dimensional finite element model that includes at least the upper body of the cam box, the lower body of the cam box, the mounting base, and the connecting bolts, and apply the applied force to perform finite element calculations including the cam box and the connecting bolts, and output the finite element calculation results. S7. Based on the finite element calculation results, conduct static strength reliability assessment and fatigue strength assessment of the connecting bolts respectively.

2. The method for calculating the strength of the connecting bolts of the cam box of a single pump as described in claim 1, characterized in that, The process of extracting and calculating the plunger cavity fluid pressure, the plunger spring force, and the inertial force of the moving parts, and calculating the resultant force of the plunger cavity fluid pressure, the plunger spring force, and the inertial force of the moving parts, includes: Calculate the hydraulic pressure in the plunger chamber, the spring force of the plunger spring, the inertial force of the moving parts, and the resultant force: Among them, F h For the resultant force, F p F is the hydraulic pressure in the plunger chamber. s F is the spring force of the plunger spring. g Let F be the inertial force of the moving part, d be the plunger diameter, P be the plunger cavity pressure, and F be the inertial force. i Let k be the spring force of the plunger spring under the first load, k be the spring stiffness, H be the plunger lift, and m be the plunger stroke. v Let be the mass of the moving part, and 'a' be the acceleration of the moving part.

3. The method for calculating the strength of the connecting bolts of the cam box of a single pump as described in claim 1, characterized in that, The calculation of the contact force magnitude and its components in the coordinate system includes: The contact force F T The calculation is as follows: Taking the camshaft axis direction in the cam box as the Z-axis and the outward direction when facing the cam and rotating clockwise as the positive direction, and the vertically upward direction as the positive Y-axis, the X-axis direction is then determined by the right-hand rule. The components are calculated as follows: In this context, x(y,z) in the subscript represents the component along the coordinate axes X (Y, Z).

4. The method for calculating the strength of the connecting bolts of the cam box of a single pump as described in claim 3, characterized in that, The calculation of the magnitude of the contact force and its components in the coordinate system also includes: Calculate at least the intersection point of the resultant force growth segment and the pressure angle curve, and the maximum value point of the resultant force, and substitute them into steps S5-S7 to conduct a static strength reliability assessment of the connecting bolts.

5. The method for calculating the strength of the connecting bolts of the cam box of a single pump as described in claim 1, characterized in that, The process of calculating the force on the bearing and the force on the hole in the mounting base based on the magnitude of the contact force and the cam mounting position in the cam box includes: S51. Measure the distance between the cam width at 1 / 2 point and the left and right end bearing widths at 1 / 2 point, and express the ratio of the two distance values ​​as 1:k. S52. Calculate the magnitude of the contact force and the cam installation position in the cam box to solve the force on the bearing, wherein the force component of the left bearing is its contact force component multiplied by the coefficient k / 1+k, and the force component of the right bearing is its contact force component multiplied by the coefficient 1 / 1+k. S53. The force acting on the hole in the mounting base is equal to the component in the coordinate system, and the force acting on the hole in the mounting base is opposite in direction to the component in the coordinate system.

6. The method for calculating the strength of the connecting bolts of the cam box of a single pump as described in claim 1, characterized in that, The applied force is applied, and finite element analysis is performed on the cam box and connecting bolts. The finite element analysis results are output, including: The three-dimensional finite element model applies corresponding forces to the bearing mounting holes and the mounting base holes of the cam box, and includes at least two analysis steps. The first analysis step corresponds to the state in which only bolt preload is applied to the connecting bolt, and the second analysis step corresponds to the state in which the bearing force and the mounting base hole force are applied after the preload is applied to the connecting bolt. Finite element calculations are performed on the cam box and the connecting bolt, and the finite element calculation results are output.

7. The method for calculating the strength of the connecting bolts of the cam box of a single pump as described in claim 6, characterized in that, Based on the finite element calculation results, static strength reliability assessment and fatigue strength assessment of the connecting bolts are carried out, including: S71. Extract the maximum tensile stress and maximum bending stress on the connecting bolts in the second analysis step of the finite element calculation results, and perform static strength evaluation; S72. Extract the maximum tensile stress and maximum bending stress on the connecting bolts in the first and second analysis steps of the finite element calculation results, and perform fatigue strength evaluation.

8. The method for calculating the strength of the connecting bolts of the cam box of a single pump as described in claim 7, characterized in that, The static strength assessment includes: Where, σ eq The equivalent stress used for evaluation is [σ], where [σ] is the allowable stress. t2max σ is the maximum tensile stress on the connecting bolt in the second analysis step. b2max R is the maximum bending stress on the connecting bolt in the second analysis step. eL S is the yield strength of the bolt material. s This is for the safety factor.

9. The method for calculating the strength of the connecting bolts of the cam box of a single pump as described in claim 7, characterized in that, The fatigue strength assessment includes: Where, σ a For stress amplitude, [σ] a [σ is the allowable stress amplitude] t2max σ is the maximum tensile stress on the connecting bolt in the second analysis step. t1max σ is the maximum tensile stress on the connecting bolt in the first analysis step. b2max σ is the maximum bending stress on the connecting bolt in the second analysis step. b1max Let d be the maximum bending stress on the connecting bolt in the first analysis step, and d be the nominal diameter of the bolt.

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