CN111805360A

CN111805360A - Improved method for drum brake pad high-precision inner arc grinding machine structure

Info

Publication number: CN111805360A
Application number: CN202010726070.0A
Authority: CN
Inventors: 扆亮海; 王程
Original assignee: Individual
Current assignee: Individual
Priority date: 2020-07-24
Filing date: 2020-07-24
Publication date: 2020-10-23

Abstract

The invention provides a structural improvement method of a drum brake pad high-precision inner arc grinding machine, which is characterized in that the overall scheme and the structural composition of the drum brake pad inner arc grinding machine are constructed according to the processing and quality requirements of drum brake pads with different inner arc radiuses, different thicknesses and different angles in grinding.

Description

Improved method for drum brake pad high-precision inner arc grinding machine structure

Technical Field

The invention relates to a brake pad inner arc grinding machine structure improvement method, in particular to a drum brake pad high-precision inner arc grinding machine structure improvement method, and belongs to the technical field of brake pad grinding machine structures.

Background

The automobile plays an increasingly important role in the current society, but the number of automobile accidents is continuously increased, and according to incomplete statistics, the traffic accidents caused by the failure of the brake pad account for more than 30 percent of all the traffic accidents, so that the quality of the brake pad of the automobile is more and more widely concerned. The drum brake pad inner arc grinder is an important part in the production process of the automobile brake pad, the quality of the automobile brake pad is directly determined by the performances of the grinding processing brake pad, such as processing precision, surface roughness and the like, and the reliability of automobile braking and the safety of automobile driving are concerned. The automobile brake pad is mostly made of special non-metallic materials, and the drum brake pad made of special materials needs to be ground by a corresponding grinding machine. The early inner arc grinding machine is improved from an inner grinding machine, and along with continuous research on drum brake pad grinding machines and continuous improvement of science and technology in various countries in the world, the drum brake pad inner arc grinding machine is continuously improved, so that the grinding quality and the yield of the automobile brake pad are continuously improved.

In the prior art, the grinding equipment for the original automobile brake pad gradually quits the public view due to the defects of poor grinding processing applicability, low production efficiency, low processing precision and the like, and a drum type brake pad inner arc grinding machine with high precision and high applicability is continuously researched and developed, more and better machine tools are applied to the field of brake pad grinding processing, and the processing quality and the production efficiency of the brake pad are improved. However, since the automobile brake pad after the grinding process has to have appropriate characteristics such as a friction coefficient and wear resistance, the requirements for the surface roughness and accuracy of the ground brake pad are increased when the brake pad is ground by the drum brake pad inner arc grinding machine. The prior art has made some improvements to the traditional grinding patterns of drum brake pad grinders in order to enable brake pad grinders to grind different types of brake pads.

With the increasing demands on drum brake pads and automobiles and the increasing demands on the quality of brake pads, whether the analysis on the inner arc grinding machine of the drum brake pad can be completed quickly and in high quality becomes important. The finite element modeling, static and dynamic performance analysis and grinding machine structure improvement of the inner arc grinding machine are utilized to develop a new grinding machine, improve the processing precision, shorten the development period and reduce the development cost, thereby having very important significance and effect.

In the prior art, a company of Wuhan Hubei develops a set of drum brake pad inner arc combined grinding machine, and after the defects that different machining parts need to be completed by different equipment in the existing drum brake pad grinding process are fully considered, the set of grinding machine creatively integrates a brake pad edge grinding device, a chamfering device and an inner arc surface grinding device, so that the production efficiency is improved, and meanwhile, the grinding machining quality of the brake pad is better controlled. The intrados grinding device adopts a positioning and clamping device to fix the brake pad on an outer arc mould, and a main motor drives an inner arc grinding wheel through a belt to grind the intrados of the brake pad. The diameter and the position of the grinding wheel are adjusted by replacing the upper grinding head of the grinding wheel to realize grinding processing; considering the condition that the same drum brake pad has different thicknesses, a hydraulic clamp is adopted to stabilize the clamping work, the grinding amount is controlled by a lifting platform, and the feeding and returning of an operation platform are hydraulically controlled; and aiming at drum brake pads with different inner arc radiuses, different arc lengths and different eccentric distances, the grinding machining is realized by adjusting the clamp and the corresponding grinding wheel grinding head.

From the general development trend of the drum brake pad inner arc grinding machine, the characteristics are mainly as follows: firstly, the brake pad grinding machine is not a single device any more, and is integrated into a series of production such as chamfering, edging and grinding cambered surface of the brake pad more and more in the grinding process of the brake pad, so that the production efficiency and quality of the brake pad are improved; secondly, the grinding machine of the brake pad is not manually controlled any more, but an electrical system controls the whole grinding process, and after the feeding, clamping and fixing of the brake pad and the grinding and processing of the inner cambered surface are finished, the grinding and processing automation of the brake pad is realized; thirdly, the brake pad grinding machine does not only grind the brake pads of one type, but processes the brake pads of different types by adjusting and grinding, thereby improving the applicability of the inner arc grinding machine. The drum brake piece inner arc grinding machine structure has the following characteristics: firstly, grinding processing of brake blocks with different inner arc radiuses, different arc lengths and different angles is realized by replacing a grinding wheel corresponding to the inner arc surfaces of the drum brake blocks and adjusting the positions of the grinding wheel; secondly, the grinding machine realizes the clamping and fixing of the brake pad through hydraulic pressure or a certain structure; and thirdly, the inner arc grinding machine adopts a conveying chain, a hydraulic or pneumatic device to realize the feeding and the output of the drum type brake pad. With the continuous expansion of the demand of automobile brake pads, a grinding machine which can grind and process high-quality brake pads in a short time is more and more concerned.

In the prior art, on the aspect of analyzing and researching the structural performance of a machine tool, not only the structural reasonability needs to be considered, but also the structural performance needs to be analyzed. If the structural performance is poor, the machine tool will not operate well. However, the theoretical analysis and the practical analysis in the prior art are not combined sufficiently, and although some work is also performed on the establishment of a finite element model and the performance analysis of the machine tool, the achievement is less in the aspects of research, development, design, structural improvement and the like of the machine tool. In the prior art, a finite element model is established for a machine tool structure, and then is analyzed and researched, and key parts and integral static and dynamic characteristics of the machine tool structure are analyzed; the machine tool has excellent static and dynamic characteristics, so that the machine tool can process a workpiece with certain processing precision requirements, and the performance of the machine tool can be analyzed by performing static and dynamic analysis on key parts or the whole machine tool. In addition, in the prior art, an error model is established according to the cause of the machining error of the machine tool, the machining precision or the machining error of the machine tool is solved through different methods, error model methods such as a matrix method, a rigid body kinematics method, a device modeling method, a multi-body system theory method and the like continuously occur, the error model is established for the machine tool through different error modeling methods, and the machining error finally output by the machine tool is solved based on the established error model; in addition, the influence on the machining precision of the machine tool is maximized by adopting an error model, so that the subsequent improvement and perfection of the machine tool structure are prepared.

However, the structural design of the internal arc grinding machine for the drum brake block in the prior art has some obvious defects, or needs for improvement in the prior art are shown in the following aspects:

firstly, the static and dynamic performance of the bed body of the brake pad grinding machine in the prior art has obvious weak links, and the analysis of the layout of rib plates of the bed body structure, the number of the rib plates, the bed body and the thickness of the rib plates has obvious defects, the wall thickness of the bed body and the thickness of the rib plates are thicker, and the first-order natural frequency of the bed body is lower; the weight of the lathe bed is large, and the structure of the lathe bed is in urgent need of improvement;

secondly, the static and dynamic analysis of the operation table of the brake pad grinding machine in the prior art shows obvious weak points, the structure design of the operation table is unreasonable, the quality of the operation table is large, and the static performance is poor; the first-order natural frequency of the operating platform is less than the frequency of the driving motor, so that the vibration is easily caused by the vibration excitation of the driving motor, the machining precision of the drum brake pad is greatly influenced, and an obvious technical short plate exists on the operating platform of the brake pad grinding machine;

the structural improvement of the drum brake pad inner arc grinding machine in the prior art is basically based on experience, a solid model is not built in the drum brake pad inner arc grinding machine, key parts of the solid model are not analyzed, a finite element model is not built in the drum brake pad inner arc grinding machine by adopting a finite element method, the deformation condition of the key parts of the drum brake pad grinding machine under the action of static load is not existed, the analysis of equivalent strain and equivalent stress diagram of the corresponding structure is not existed, and the structural improvement by lacking theory and technical support is difficult to effectively improve the structural performance of the grinding machine;

fourthly, in the prior art, the static performance analysis of key parts of the brake pad grinding machine and the dynamic analysis of the brake pad grinding machine are lacked, so that the grinding machining precision of the drum brake pad cannot be influenced due to large vibration caused by the excitation of the driving motor in the grinding machining process of the intrados of the brake pad by the brake pad grinding machine. The natural frequency of the grinder body in the prior art is relatively low, and the vibration of the grinder body at the grinding part of the brake pad directly influences the processing precision of the brake pad, and is a weak link in the whole brake pad grinder construction process.

The invention researches and develops an inner arc grinding machine for the drum brake pad aiming at the grinding requirements of the drum brake pad with different thicknesses, different inner arc radiuses and different angles, and analyzes and improves the establishment, static and dynamic analysis and structure of a solid model and a finite element model of the grinding machine for the drum brake pad.

Disclosure of Invention

The invention provides a structural improvement method of a drum brake pad high-precision inner arc grinding machine, which is characterized in that the overall scheme and the structural composition of the drum brake pad inner arc grinding machine are constructed according to the processing and quality requirements of drum brake pads with different inner arc radiuses, different thicknesses and different angles in grinding. An improved scheme is provided by a control factor method, the structure is improved, the improved structural performance is greatly improved, and a foundation is laid for obtaining a drum brake pad inner arc grinding machine with better performance.

In order to achieve the technical effects, the technical scheme adopted by the invention is as follows:

a structural improvement method of a drum brake pad high-precision inner arc grinding machine comprises the steps of firstly establishing a solid model of the drum brake pad inner arc grinding machine, then realizing static analysis of the inner arc grinding machine based on a finite element analysis method, analyzing structural power characteristics of the drum brake pad inner arc grinding machine, and finally improving the structure of the drum brake pad inner arc grinding machine;

firstly, establishing a solid model of an inner arc grinding machine of a drum brake pad, and establishing a three-dimensional solid model of the inner arc grinding machine of the drum brake pad by adopting SolidWorks software based on a grinding structure of the inner arc grinding machine of the drum brake pad and a feeding device of the inner arc grinding machine of the drum brake pad;

secondly, realizing static analysis of the inner arc grinding machine based on a finite element analysis method, and laying a foundation for further optimizing the performance of the inner arc grinding machine of the drum brake pad through analyzing the overall characteristics of key parts of the inner arc grinding machine of the drum brake pad;

analyzing the structural power characteristics of the drum brake pad inner arc grinding machine, analyzing the vibration condition of the drum brake pad inner arc grinding machine key part under the excitation of a driving motor according to the dynamic performance and modal analysis of the drum brake pad inner arc grinding machine key part, and verifying the rationality of the built drum brake pad inner arc grinding machine;

and fourthly, improving the structure of the inner arc grinding machine of the drum brake pad, and performing structural improvement on weak links of key parts of the inner arc grinding machine of the drum brake pad in static and dynamic performance analysis by adopting a control factor method to improve the overall performance of the inner arc grinding machine of the drum brake pad.

The improved method of the drum brake pad high-precision inner arc grinding machine structure comprises the following steps that in the grinding structure of the brake pad grinding machine, the grinding assembly of the brake pad grinding machine mainly grinds the inner arc surface of the drum brake pad, the grinding structure mainly comprises a motor, a transmission system and a grinding wheel, the grinding wheel in the grinding assembly of the brake pad grinding machine is controlled by a three-phase asynchronous motor to continuously grind the inner arc surface of the drum brake pad, and power transmission is realized by a synchronous belt; grinding assembly of a brake pad grinding machine is carried out, wherein a bottom machine body of a grinding device and the bottom of a bearing grinding device are arranged to be arc-shaped;

the grinding and feeding device of the brake pad grinding machine comprises guide rails, a ball screw and a motor, and realizes the movement of the grinding device of the brake pad grinding machine, the grinding and feeding device of the brake pad grinding machine is provided with two guide rails in the vertical and horizontal directions, a servo motor in the vertical direction drives the ball screw through a coupler and then drives the grinding device and the horizontal feeding device, so that the movement in the vertical direction is realized, the structure in the horizontal direction is similar to that in the vertical direction, the servo drive motor drives the ball screw to realize the horizontal movement of the grinding device of the brake pad grinding machine, and the grinding device finally realizes the arc movement through the vertical and horizontal movements to finish the grinding processing of the inner arc;

the brake pad grinding machine operating platform comprises a bottom bracket, an outer arc clamping fixture and two side clamping plates, further clamps and fixes the drum brake pad from the brake pad clamping device, and finishes grinding the inner arc surface of the drum brake pad on the structure; the bottom clamping plate of the brake pad grinding machine operating platform is arranged on the bed of the inner arc grinding machine, the two side clamping plates of the brake pad and the outer arc clamping fixture are positioned on the bottom bracket, and the clamping plates and the outer arc clamping fixture restrain the circumferential and radial movement of the drum type brake pad.

The improved structure method of the high-precision inner arc grinding machine for the drum brake lining comprises the following steps that in a brake lining feeding device, a brake lining conveying device comprises a brake lining hopper, a conveying guide rail and an air cylinder, and the brake lining from the previous device is conveyed to a clamping device of the drum brake lining; the brake pad conveying device is arranged on the inner arc grinding machine body on one side different from the grinding device; after the grinding machine is started, the air cylinder drives the pushing block on the guide rail to push the drum brake piece at the bottommost layer of the hopper to the brake piece clamping device, the air cylinder drives the pushing block to return to the initial position after the brake piece is completely pushed out of the hopper, and the air cylinder drives the pushing block to reciprocate back and forth to feed the brake piece.

The brake pad clamping device comprises a brake pad clamping wedge block, a ball screw and a guide rail, the drum brake pad is clamped, the position of the drum brake pad under the grinding action of the grinding device is ensured, and the brake pad clamping device is arranged on the frame of the inner arc grinding machine and is positioned between the drum brake pad conveying device and the operating platform; the brake block clamping device adopts wedges and a guide rail to realize circumferential and radial fixation of a drum brake block, and the brake block is pushed to move backwards on the guide rail by a cylinder conveyed by the brake block.

The method for improving the structure of the drum brake pad high-precision inner arc grinding machine comprises the following steps of establishing a finite element model of the drum brake pad grinding machine on the basis of a solid model of the drum brake pad inner arc grinding machine, and defining material properties, selecting units, dividing grids, constraining boundaries and applying loads according to structural materials;

firstly, braking piece grinding machine grinding force analysis, braking piece grinding machine in the abrasive machining process, the power between emery wheel and drum-type braking piece is grinding force, and the grinding force A of emery wheel can be decomposed into three mutually perpendicular's component: feed grinding force A in axial direction_fGrinding force A in the tangential direction of the grinding wheel_cRadial cutting force A in the normal direction_pThe grinding force of the grinding wheel to the drum brake pad is as follows:

A＝0u_ωf_pa_aformula 1

In the formula: a is grinding force, O is grinding coefficient, u_ωAs the rotational speed of the grinding wheel, f_pFor grinding amount, a_aThe feed amount of the brake pad;

the grinding wheel rotating speed and the brake pad feeding amount are fixed, the grinding processing amount of the designed grinding wheel on the inner arc surface of the drum brake pad is also fixed, and under the action of vibration and various errors of a brake pad grinding machine, the grinding amount changes, and the grinding force of the grinding wheel on the drum brake pad changes;

secondly, stress analysis is carried out among the structures of the brake pad grinding machine, the sum of the gravity of all the structures of the brake pad grinding machine acts on the bed body of the grinding machine, and the grinding force acts on the operating platform and bears the gravity of a certain amount of drum brake pads; the bending moment effect caused by the grinding force is equivalently acted on the lathe bed on one side, and meanwhile, the lathe bed is also under the action of the gravity of the n-shaped bracket, the grinding device, the operating platform and a certain amount of drum brake pads, and the lathe bed on the other side is under the action of the gravity of the clamping device, the brake pad feeding device and a certain amount of drum brake pads;

calculating the acting force of the operating platform: the operating platform bears grinding force and a certain amount of gravity of the drum brake pads, the maximum mass of the drum brake pads which can be machined by the brake pad grinding machine is 3g multiplied by 1526-3052 g according to the size of the operating platform and relevant parameters of the drum brake pads ground by the brake pad grinding machine, the gravity borne by the operating platform is 30N, and cutting force equivalently acts on the operating platform;

equivalently calculating the grinding force acting on the grinding machine: the grinding force of the grinding machine acting on the drum brake pad acts on the body of the grinding machine through the grinding device and the n-shaped bracket of the grinding machine, the grinding force is equivalently acted on the joint surface of the n-shaped bracket and the body of the grinding machine, and only the grinding force in the tangential direction of the grinding wheel and the back cutting force in the normal direction are subjected to relevant equivalent calculation; the grinding force along the tangential direction of the grinding wheel is equivalent to a tangential component parallel to a joint surface, and the back cutting force along the normal direction is equivalent to a normal component perpendicular to the joint surface;

calculating the load acting on the lathe bed on one side: the lathe bed on one side under the action of the gravity of the clamping device, the drum brake pad feeding device and a certain amount of drum brake pads is subjected to the load of 520N;

brake block grinding machine vibration source frequency: the brake pad grinding machine vibrates due to external vibration in the process of grinding the drum brake pad, and the main vibration excitation sources of the brake pad grinding machine are a motor for controlling a grinding device to horizontally and vertically move and a three-phase asynchronous motor for controlling a grinding wheel to continuously rotate; controlling the rotating speed of a three-phase asynchronous motor of the grinding wheel to be 3000r/min, and controlling the rotating speed of a servo motor in the horizontal and vertical directions to be 2000 r/min; based on the formula of the excitation frequency caused by the rotation of the motor, the excitation frequency caused by the three-phase asynchronous motor is 50Hz, and the excitation frequency caused by the motor in the horizontal and vertical directions is 33.3 Hz.

The invention relates to a method for improving the structure of a high-precision inner arc grinding machine for a drum brake pad, which comprises the following steps of establishing models of parts of the inner arc grinding machine for the drum brake pad by adopting SolidWorks software, assembling the parts into corresponding mechanical system devices according to the overall design of the grinding machine for the brake pad, and finally assembling the devices into an overall model of the inner arc grinding machine for the drum brake pad; introducing a structural model of the brake pad grinding machine, which needs to be analyzed for performance, into finite element analysis software by adopting a data interface between SolidWorks software and the finite element analysis software to establish a finite element model;

the structure of the brake pad grinding machine is simplified to a certain extent, and the structure is specifically simplified as follows: firstly, an auxiliary structure which is subjected to small acting force or even no acting force in a brake pad grinding machine is removed; secondly, relevant process structures in the brake pad grinding machine are removed; thirdly, replacing a small-taper and small-curvature curved surface in the brake pad grinding machine by a plane; fourthly, removing a hole with a smaller size in the brake pad grinding machine;

the bed of the brake pad grinding machine supports the whole inner arc grinding machine, and the grinding device of the brake pad grinding machine moves on the n-shaped bracket and plays a supporting role for the grinding device; the method comprises the following steps of carrying out mechanical analysis on a lathe bed, an operating platform and a grinding device main shaft of a brake pad grinding machine, analyzing relevant characteristics of the brake pad grinding machine, and establishing a finite element analysis model for the lathe bed, the operating platform and the grinding device main shaft of the brake pad grinding machine:

firstly, defining unit types, and selecting specific analyzed unit types according to geometric shapes, analysis types and precision requirements of analyzed problems when carrying out finite element analysis; the invention selects a ten-node tetrahedral solid structure unit for analyzing the performance of the brake pad grinding machine component, and calculates the three-dimensional problem;

secondly, defining the material attribute of the component, analyzing the related performance of the brake pad grinding machine component, considering and defining the elastic modulus and the density of the component material, wherein key components of the brake pad grinding machine comprise a grinding machine body, an operating platform and a grinding device spindle of the grinding machine, and steel is selected;

dividing grids, namely dividing the grids of the three-dimensional solid model imported through a data interface between SolidWorks software and finite element analysis software to generate a finite element model consisting of nodes and units;

fourthly, constraint is applied, constraint conditions need to be set for static and dynamic performance analysis of the brake pad grinding machine, and constraint meeting actual conditions needs to be applied to obtain accurate analysis results; the invention mainly analyzes the static and dynamic performance of key parts of the brake pad grinding machine, so that the constraint condition is applied to the key parts: the method comprises the following steps of (1) restricting all degrees of freedom of a connecting surface of an operating table and a machine body, restricting the degree of freedom except the degree of freedom rotating along an axis of a main shaft of a grinding device, fixing the bottom surface of the machine body of a grinding machine, and restricting all degrees of freedom of the bottom surface of the machine body;

and fifthly, applying load, wherein when finite element analysis is carried out on key parts of the brake pad grinding machine, the operating platform mainly bears the gravity and the grinding force of the brake pad, and the operating platform mainly bears the gravity of the operating platform, the grinding device, the bracket and the brake pad feeding device through the action of the brake pad on the operating platform, and the grinding machine body mainly bears the gravity of the operating platform, the grinding device, the bracket and the.

The invention relates to a method for improving the structure of a high-precision inner arc grinding machine for a drum brake pad, which comprises the following steps of establishing a finite element equation of structural static analysis by adopting a variational method, expressing a field problem by adopting a partial differential equation by adopting the variational method, approximately solving by adopting a linear equation instead of a pan function extreme value problem in the process of solving the partial differential equation, dividing the structure into units with certain size by adopting the finite element method, and regarding the structure as being formed by interconnected unit nodes;

the equivalent equation for the static analysis is:

[B]×{μ}＝{A}

[B]×{μ}＝{A^γ}+{A^αformula 2

In the formula: [ B ]]In order to construct the overall stiffness matrix of the structure,

{ mu } is a displacement vector of the unit node; { A } is a load matrix of the structure; { A^γThe branch load vector is used as the branch load vector; { A^αIs the total external load experienced; n is the number of structural division units; [ Be ]]Is a structural unit stiffness matrix;

obtaining the displacement vector of each unit node by solving a finite element equation 2, and obtaining an expression of the relationship between the stress and the strain of the unit node by adopting a displacement interpolation function according to the strain, the displacement and the relationship between the strain and the displacement obtained by elasticity mechanics:

{θ^h}＝[Y]×{v}-{^th}

{σ}＝[H]×{θ^thformula 3

In the formula: { theta ]^hIs induced by stressStrain induced; [ Y ]]Is a strain-displacement matrix on the node; { v } is the node displacement vector; {^thIs the other strain of the node; { theta ]^thIs the thermal strain vector; { ζ } is the stress vector; [ H ]]Is an elastic matrix;

and (3) obtaining the stress corresponding to each node by solving the formula 3, solving the displacement and the stress of the unit node of the structure by a finite element analysis method, and finally obtaining the static characteristic of the structure.

The method for improving the structure of the high-precision inner arc grinding machine for the drum brake pad is characterized in that an operating platform of the grinding machine for the brake pad is directly acted by grinding force through the brake pad, and the vibration of the operating platform directly influences the grinding precision of the drum brake pad; according to the fixed condition of the operating platform, the combined surface of the operating platform and the brake pad grinding machine is subjected to full constraint, and modal analysis is performed on the basis to obtain the first four-order frequency and the vibration mode of the operating platform of the brake pad grinding machine: the first-order vibration mode of the operation table has larger deformation; the second and third vibration modes of the operating platform can be obtained, and the operating platform is twisted along the X-axis direction under the influence of the vibration of the driving motor; according to the four-order mode vibration mode, the operation table is bent along the Y-axis direction; when the inner arc surface of the drum brake pad is ground and processed by the inner arc forming grinder, the operating platform cannot influence the processing precision of the drum brake pad due to the resonance with the driving motor;

the static performance of the brake pad grinder body is stable, and the dynamic performance of the brake pad grinder body is a main factor influencing the performance; simplifying and establishing a finite element model for a solid model of the bed body, limiting all degrees of freedom of the bottom surface of the grinding machine, and carrying out modal analysis on the finite element model to obtain the front four-order frequency and the vibration mode of the inner arc grinding machine of the drum brake pad: the first-order vibration frequency of the lathe bed is relatively smaller but larger than the excitation frequency, and the natural frequency of the grinder frame is increased along with the increase of the order, so that the structure of the brake pad grinder meets the design and construction requirements; the first four-order vibration modes are local vibration, the first and second-order vibration modes appear at the feeding part of the drum brake pad, and have no influence on the processing precision of the drum brake pad, but the third and fourth-order vibration modes of the grinder body appear at the grinding position of the drum brake pad, the deformation is large, the grinding precision of the inner cambered surface of the drum brake pad is greatly influenced, and the grinding device is a weak link in the construction and design process of the brake pad grinder.

The improved method of the drum brake pad high-precision inner arc grinding machine structure is characterized in that the improved lathe bed structure is based on basic size parts of the lathe bed of the brake pad grinding machine, and the dynamic performance of the improved lathe bed structure is taken as a structural improvement optimization target;

deformation of a grinding machine body of the brake pad caused by excitation of a driving motor mainly occurs at a transmission part and a grinding position of the brake pad, the deformation direction is mainly in an X direction, and a transverse rib plate is applied to the grinding machine body under the deformation condition of the grinding position of the brake pad; the following two improvements were devised: the rib plate improvement scheme I: applying a transverse rib plate at the grinding position of the brake pad; the second rib plate improvement scheme: applying a transverse rib plate at the grinding and feeding positions of the brake pad respectively;

establishing a finite element model for the grinder body of the two improved schemes for modal analysis, wherein the vibration conditions of the grinder body of each scheme after the improvement are basically consistent with those of the original grinder body, but the corresponding natural frequency is improved to a certain extent, applying a transverse rib plate can improve the natural frequency of the grinder body by comparing and analyzing the modal analysis results of the three schemes including the original grinder body, the rib plate improved scheme I and the rib plate improved scheme II, and simultaneously applying the transverse rib plate at the grinding and feeding positions of a brake pad can play a greater role in improving the amplitude of the natural frequency of the grinder body; in addition, a transverse rib plate is applied to the grinding and feeding part of the brake pad, so that the vibration deformation caused by the excitation of a driving motor is obviously reduced, and compared with the original bed mode analysis result, the dynamic performance of the grinding machine bed body is greatly improved at the grinding part after the transverse rib plate is applied, so that the processing precision of the brake pad grinding machine is ensured; performing static analysis on the grinder body after a transverse rib plate is respectively applied to the grinding and feeding positions of the brake pad to obtain the static characteristics including deformation and stress of the grinder body of the brake pad;

performing static analysis on the grinder body of the second rib plate improvement scheme, wherein the maximum deformation of the grinder body applying the second transverse rib plate under the action of static load is 0.003mm, the maximum stress is 0.45MPa, and the deformation of the grinder body of the drum brake pad under the action of static load is small and can be ignored; however, the weight of the bed of the grinding machine is large, the structure has certain size allowance, and a better bed structure improvement scheme is obtained through analysis and comparison on the basis of ensuring certain improvement of dynamic performance by taking the front four-order natural frequency of the bed of the grinding machine as a target.

The method for improving the structure of the drum brake pad high-precision inner arc grinding machine further comprises the steps of controlling the wall thickness of a machine body and the wall thickness of a rib plate within a certain range, and designing the following three structure improvement schemes for improving the performance of the machine body of the grinding machine with the transverse rib plate: the first structural improvement scheme is as follows: the wall thickness of the lathe bed and the thickness of the rib plate are reduced by 2 mm; the structural improvement scheme II: the wall thickness of the lathe bed and the thickness of the rib plate are reduced by 4 mm; the structural improvement scheme is three: the wall thickness of the lathe bed and the thickness of the rib plate are reduced by 6 mm;

establishing a finite element model for the machine body of each structural improvement scheme for carrying out modal shape, wherein the mode shapes of the machine body of each improved scheme are basically consistent with those of the machine body of the second structural improvement scheme of the rib plate, but the natural frequency of the first four orders is obviously changed; the reduction of the wall thickness of the bed body and the thickness of the rib plate causes the reduction of the first four-order natural frequency of the bed body of the grinding machine in the second improvement scheme of the rib plate, compared with the original bed body, the dynamic performance of the bed body is obviously improved, but the deformation of the bed body of the grinding machine under the action of the load and the driving motor is continuously enlarged along with the continuous reduction of the thickness;

aiming at weak links in static and dynamic performances of the brake pad grinder body, analyzing the layout of rib plates of the grinder body structure, the number of the rib plates, the grinder body and the thickness of the rib plates to obtain a final brake pad grinder body structure improvement scheme: applying a transverse rib plate on the feeding and grinding part of the brake pad on the grinder body, and reducing the wall thickness of the grinder body and the thickness of the rib plate by 4mm to obtain a new grinder body with the first-order frequency of 256.49Hz and the first-order natural frequency of the grinder body improved by 46.1%; the weight of the new bed body is 720.1Kg, and the weight of the bed body is reduced by 20.3%.

The improved method of the structure of the high-precision inner arc grinding machine for the drum brake pad further improves the structure of the operation table by a topological optimization method, reduces the mass of the operation table under the condition of unchanged basic size, improves the static performance of the structure of the operation table and improves the overall performance of the grinding machine for the brake pad; carrying out structural improvement on the size allowance, and determining an optimal improvement scheme of an operation table through comparative analysis by taking the deformation of the brake pad grinding machine and the first four-order vibration frequency as optimization targets;

the upper surface of the operating platform is designed to be arc-shaped, the minimum vertical height of the structure is 40mm, and three improvement schemes are designed for the performance of the brake pad grinding machine in the optimizing process of the operating platform: the first optimization scheme of the operation platform is as follows: the operation platform is reduced by 10% in topological optimization; and (2) optimizing a second operating platform: reducing the weight by 20% through topological optimization of the operating platform; and the third optimization scheme of the operation platform is as follows: reducing the weight by 30% through topological optimization of the operating platform;

optimizing three operation table structure improvement schemes by adopting a topological optimization function of Design Xplorer in Ansys Workbench software, changing an operation table model according to a topological optimization calculation result, and finally performing statics and modal analysis on the changed operation table model, wherein the analysis result is as follows: under the condition that the overall size is kept unchanged, along with the continuous reduction of the weight of the bottom structure of the operating platform, the deformation of the operating platform is gradually increased under the action of the grinding force equivalent acting force and the self gravity, but the maximum deformation of the operating platform in the third operating platform optimization scheme with the maximum light weight degree of the operating platform is 0.03mm, the maximum stress is 3.51MPa, and the maximum stress is relatively small and hardly influences the grinding machining of the drum brake pad;

along with the continuous reduction of the weight of the bottom structure of the operation table, the vibration frequency generated by the operation table at the driving motor is sequentially reduced, but the lowest frequency in the optimization schemes of the operation table is greater than the frequency of the driving motor, and the three optimization schemes of the operation table cannot generate resonance due to the excitation of the driving motor; analyzing the three different topological optimization schemes to obtain a final structural improvement scheme of the operating platform of the drum brake pad inner arc grinding machine, which is an operating platform optimization scheme III: the quality of the operation table with the improved structure is reduced by 30 percent, the quality is greatly reduced, and the static performance is obviously improved; and the first-order natural frequency of the improved operating platform is 161.96Hz which is higher than the frequency of the driving motor, so that the influence of vibration caused by the excitation of the driving motor on the machining precision of the drum brake pad is avoided.

Compared with the prior art, the invention has the following contributions and innovation points:

firstly, the method for improving the structure of the high-precision inner arc grinding machine for the drum brake pad provided by the invention is based on the construction of the inner arc grinding machine for the drum brake pad, and aims at the processing and quality requirements of grinding drum brake pads with different inner arc radiuses, different thicknesses and different angles, a solid model is established for the built inner arc grinding machine for the drum brake pad, the key parts of the solid model are analyzed, the static and dynamic performances of the solid model are analyzed, and the structural improvement is carried out on weak links expressed in the analysis process. An improvement scheme is provided by a control factor method, the structure of the grinding wheel is improved, the improved structure performance is greatly improved, and a foundation is laid for obtaining a drum brake pad inner arc grinding machine with better performance;

secondly, the invention provides a structural improvement method of a drum brake pad high-precision inner arc grinding machine, which comprises the steps of constructing the overall scheme and the structural composition of the drum brake pad inner arc grinding machine, and establishing a three-dimensional solid model of the brake pad grinding machine by adopting SolidWorks software on the basis of the overall scheme and the structural composition for subsequent structural performance analysis and corresponding structural improvement. The method adopts a finite element method to perform the following steps on key parts of an inner arc grinding machine of the drum brake pad: the method comprises the steps that finite element models are established on an operation table, a grinding device spindle and a grinder body, static analysis is carried out on the finite element models on the basis, the deformation condition of key parts of a brake pad grinder under the action of static load is determined, the deformation and stress of the key parts of the brake pad grinder under the action of the static load are smaller and do not exceed the stress requirement of the structure through analysis of equivalent strain and equivalent stress graphs of corresponding structures, the static rigidity requirement of the grinder is met, but the structure of the grinder body of the brake pad grinder has certain size allowance, the structural performance needs to be improved through structural improvement, and a solid foundation is laid for structural improvement of the method;

thirdly, the improved structure method of the drum brake pad high-precision inner arc grinding machine provided by the invention is used for carrying out dynamic analysis on the brake pad grinding machine based on the static performance analysis of key parts of the brake pad grinding machine, so as to ensure that the brake pad grinding machine does not influence the grinding machining precision of the drum brake pad due to larger vibration caused by the excitation of a driving motor in the grinding machining process of the inner arc surface of the drum brake pad. Through carrying out modal analysis to the key part of braking piece grinding machine, the natural frequency of the key part of grinding machine and drive motor excitation frequency difference are great, and the grinding machine can not produce resonance under drive motor's effect. However, the natural frequency of the grinder body is relatively low, and the vibration of the grinder body at the grinding part of the brake pad directly influences the processing precision of the brake pad, so that the grinder is a weak link in the whole brake pad grinder construction process, needs to be improved, and defines the improvement direction and the improvement target;

fourthly, according to the improved method of the drum brake pad high-precision inner arc grinding machine body structure, aiming at weak links in static and dynamic performances of the brake pad grinding machine body, the final brake pad grinding machine body structure improvement scheme is obtained by analyzing the layout of rib plates of the machine body structure, the number of the rib plates, the thickness of the machine body and the thickness of the rib plates: applying a transverse rib plate on the feeding and grinding part of the brake pad on the grinder body, and reducing the wall thickness of the grinder body and the thickness of the rib plate by 4mm to obtain a new grinder body with the first-order frequency of 256.49Hz and the first-order natural frequency of the grinder body improved by 46.1%; the weight of the new lathe bed is 720.1Kg, the weight of the lathe bed is reduced by 20.3 percent, and the improvement of the lathe bed structure obtains good effect;

fifthly, according to the structural improvement method of the drum brake pad high-precision inner arc grinding machine, aiming at weak links expressed in static and dynamic analysis of the brake pad grinding machine operating platform, the weak links are analyzed through three different topological optimization schemes, and the final structural improvement scheme of the drum brake pad inner arc grinding machine operating platform is obtained as an operating platform optimization scheme III: the quality of the operation table with the improved structure is reduced by 30 percent, the quality is greatly reduced, and the static performance is obviously improved; the first-order natural frequency of the improved operating platform is 161.96Hz which is higher than the frequency of the driving motor, so that the influence of vibration caused by vibration of the driving motor on the machining precision of the drum brake pad is avoided, and the improved operating platform of the brake pad grinding machine achieves an ideal effect.

Drawings

FIG. 1 is a schematic diagram of the drum brake pad inner arc grinder system components of the present invention.

FIG. 2 is a schematic illustration of a solid model of a drum brake pad inner arc grinder of the present invention.

FIG. 3 is a schematic diagram of the topology optimization space of the present invention.

Fig. 4 is a schematic diagram of the optimal topology of the present invention.

Detailed Description

The technical scheme of the improved structure method of the drum brake pad high-precision inner arc grinding machine provided by the invention is further described below with reference to the accompanying drawings, so that a person skilled in the art can better understand the invention and can implement the invention.

The invention relates to a method for improving the structure of a drum brake pad high-precision inner arc grinding machine, which comprises the steps of firstly establishing a solid model of the drum brake pad inner arc grinding machine, as shown in figure 1, then realizing static analysis of the inner arc grinding machine based on a finite element analysis method, then analyzing the structural power characteristics of the drum brake pad inner arc grinding machine, and finally improving the structure of the drum brake pad inner arc grinding machine;

analyzing the structural power characteristics of the drum brake pad inner arc grinding machine, analyzing the vibration condition of the drum brake pad inner arc grinding machine key parts under the excitation of a driving motor according to the dynamic performance and modal analysis of the drum brake pad inner arc grinding machine key parts (comprising an operation table, a grinding device main shaft and a grinding machine body), and verifying the rationality of the built drum brake pad inner arc grinding machine;

Firstly, establishing a solid model of an inner arc grinding machine of a drum type brake pad

Grinding structure of brake pad grinding machine

The grinding structure of the drum brake pad inner arc grinding machine realizes grinding of the inner arc surface of the drum brake pad, and the processing quality of the drum brake pad is directly influenced by the structural rationality and the motion reliability of the grinding structure.

1. Grinding assembly of brake pad grinding machine

The assembly of the brake pad grinding machine mainly grinds the inner arc surface of the drum brake pad, the assembly mainly comprises a motor, a transmission system and a grinding wheel, the grinding wheel in the grinding assembly of the brake pad grinding machine is controlled by a three-phase asynchronous motor to realize continuous grinding of the inner arc surface of the drum brake pad, and power transmission is realized by a synchronous belt; the grinding assembly of the brake pad grinding machine sets the bottom machine body of the grinding device and the bottom of the bearing grinding device to be arc-shaped, so that the grinding device is prevented from interfering with other parts in the grinding process of the drum brake pad, and the grinding of the inner arc surface of the brake pad by the drum brake pad inner arc grinding machine is guaranteed.

For the grinding processing of drum brake pads with different arc lengths, different angles and different inner arc radiuses, only relevant parameters of driving motors in vertical and horizontal directions in a control system need to be adjusted, the assembling and adjusting operation of grinding brake pads of different types is simple and rapid, the production efficiency is greatly improved, and the production benefit is increased.

2. Grinding and feeding device of brake pad grinding machine

The grinding and feeding device of the brake pad grinding machine comprises guide rails, a ball screw and a motor, the movement of the grinding device of the brake pad grinding machine is realized, the grinding and processing of a drum brake pad are guaranteed, the grinding and feeding device of the brake pad grinding machine is provided with two vertical guide rails and two horizontal guide rails, a vertical servo motor drives the ball screw through a coupler to drive the grinding device and the horizontal feeding device, the movement in the vertical direction is realized, the structure in the horizontal direction is similar to that in the vertical direction, the servo drive motor drives the ball screw to realize the horizontal movement of the grinding device of the brake pad grinding machine, the grinding device finally realizes the arc movement through the vertical movement and the horizontal movement in the two directions, and the grinding and.

3. Brake block grinding machine operation panel

The brake pad grinding machine operating platform comprises a bottom bracket, an outer arc mould and two side clamping plates, and mainly has the functions of further clamping and fixing the drum brake pad from the brake pad clamping device and finishing grinding of the inner arc surface of the drum brake pad on the structure; the bottom clamping plate of the brake pad grinding machine operating platform is arranged on the bed body of the inner arc grinding machine to support the operating platform, the two side clamping plates and the outer arc clamping fixture of the brake pad are positioned on the bottom support, and the clamping plates and the outer arc clamping fixture constrain the circumferential and radial movement of the drum brake pad to realize the circumferential and radial fixation of the drum brake pad, and lay a foundation for grinding the high-precision drum brake pad.

(II) brake block feeding device

The brake block feeding device of the brake block grinder automatically conveys and clamps the drum brake block, the drum brake block feeding device plays an irreplaceable role in the grinding process of the drum brake block, and the clamping and fixing quality of the drum brake block has a great influence on the machining precision of the drum brake block.

1. Brake pad conveying device

The brake pad conveying device of the brake pad grinding machine comprises a brake pad hopper, a conveying guide rail and an air cylinder, and conveys a brake pad from the previous equipment to the clamping device of the drum brake pad, so that a foundation is laid for grinding the inner cambered surface of the drum brake pad; the brake pad conveying device is arranged on the inner arc grinding machine body on one side different from the grinding device; the brake pieces are orderly stacked in the brake piece hopper; after the grinding machine is started, the air cylinder drives the pushing block on the guide rail to push the drum brake piece at the bottommost layer of the hopper to the brake piece clamping device, the air cylinder drives the pushing block to return to the initial position after the brake piece is completely pushed out of the hopper, and the air cylinder drives the pushing block to reciprocate back and forth to feed the brake piece.

2. Brake pad clamping device

The brake pad clamping device comprises a brake pad clamping wedge block, a ball screw and a guide rail, and has the main function of clamping the drum brake pad, ensuring the position of the drum brake pad under the grinding action of the grinding device and providing guarantee for the machining precision of the drum brake pad. The brake shoe clamping device is arranged on the inner arc grinding machine frame and is positioned between the drum brake shoe conveying device and the operating platform; the brake block clamping device adopts wedges and a guide rail to realize circumferential and radial fixation of a drum brake block, and the brake block is pushed to move backwards on the guide rail by a cylinder conveyed by the brake block.

Establishing a finite element model of the drum brake pad inner arc grinding machine

Brake pad grinder force analysis

The brake pad grinder finite element model is established on the basis of a solid model of a drum brake pad inner arc grinder, and material properties, unit selection, grid division, boundary constraint and load application are defined according to structural materials; and corresponding mechanical analysis can be carried out only by applying load to the brake pad grinding machine, so that the brake pad grinding machine is subjected to stress analysis before a finite element model of the brake pad grinding machine is established, and the stress condition of the inner arc grinding machine is analyzed.

1. Brake pad grinding machine grinding force analysis

In the grinding process of the brake pad grinding machine, the force between the grinding wheel and the drum brake pad is grinding force, and the grinding force A of the grinding wheel can be decomposed into three components which are perpendicular to each other: feed grinding force A in axial direction_fGrinding force A in the tangential direction of the grinding wheel_cRadial cutting force A in the normal direction_pThe grinding force of the grinding wheel to the drum brake pad is as follows:

A＝0u_ωf_pa_aformula 1

the grinding wheel rotating speed and the brake pad feeding amount are fixed, the grinding processing amount of the designed grinding wheel on the inner arc surface of the drum brake pad is also fixed, and under the action of vibration and various errors of a brake pad grinding machine, the grinding amount changes, and the grinding force of the grinding wheel on the drum brake pad changes.

2. Analysis of stress between structures of brake pad grinding machine

The sum of all structural gravity of the brake pad grinding machine acts on the bed of the grinding machine, and grinding force acts on the operating platform and bears the action of a certain amount of gravity of drum brake pads; the bending moment caused by the grinding force acts on the lathe bed on one side equivalently, and simultaneously, the lathe bed on the other side is also acted by the gravity of the n-shaped bracket, the grinding device, the operating platform and a certain amount of drum brake pads, and the lathe bed on the other side is acted by the gravity of the clamping device, the brake pad feeding device and a certain amount of drum brake pads.

(1) Calculating operating table forces

The operating platform bears grinding force and a certain amount of gravity of the drum brake pads, the maximum mass of the drum brake pads which can be machined by the brake pad grinding machine is 3g multiplied by 1526-3052 g according to the size of the operating platform and relevant parameters of the drum brake pads ground by the brake pad grinding machine, the gravity borne by the operating platform is 30N, and cutting force equivalently acts on the operating platform.

(2) Equivalent calculation of grinding force on grinding machine

The grinding force of the grinding machine acting on the drum brake pad acts on the body of the grinding machine through the grinding device and the n-shaped bracket of the grinding machine, the n-shaped bracket of the grinding machine is in direct contact with the body of the grinding machine, the grinding force acts on a joint surface of the n-shaped bracket and the body of the grinding machine equivalently, and only the grinding force in the tangential direction of the grinding wheel and the back cutting force in the normal direction are subjected to relevant equivalent calculation; the grinding force along the tangential direction of the grinding wheel is equivalent to a tangential component parallel to the joint surface, and the back cutting force along the normal direction is equivalent to a normal component perpendicular to the joint surface.

(3) Calculating the load acting on one side of the bed

The side of the bed subjected to the weight of the clamping device, the drum brake pad advancement device and the number of drum brake pads was subjected to a load of 520N.

(4) Brake pad grinding machine vibration source frequency

The brake pad grinding machine can vibrate due to external vibration in the process of grinding the drum brake pad, and the main excitation sources of the brake pad grinding machine are a motor for controlling a grinding device to horizontally and vertically move and a three-phase asynchronous motor for controlling a grinding wheel to continuously rotate; controlling the rotating speed of a three-phase asynchronous motor of the grinding wheel to be 3000r/min, and controlling the rotating speed of a servo motor in the horizontal and vertical directions to be 2000 r/min; based on the formula of the excitation frequency caused by the rotation of the motor, the excitation frequency caused by the three-phase asynchronous motor is 50Hz, and the excitation frequency caused by the motor in the horizontal and vertical directions is 33.3 Hz.

(II) establishing a finite element model of a brake pad grinding machine

The finite element model is established for the simple structure by adopting finite element analysis, but the difficulty of directly establishing the finite element model for the complex structure or the irregular structure is high, and the finite element modeling aiming at the complex structure is realized by a data interface between three-dimensional modeling software and finite element analysis software.

The method comprises the steps of establishing models of parts of a drum brake pad inner arc grinding machine by adopting SolidWorks software, assembling the parts into corresponding mechanical system devices according to the overall design of the brake pad grinding machine, and finally assembling the devices into the overall model of the drum brake pad inner arc grinding machine; as shown in fig. 2, the drum brake pad inner arc grinder solid model is a finite element model established by importing a structural model of a brake pad grinder, which needs to be analyzed for performance, into finite element analysis software by using a data interface between solid works software and the finite element analysis software.

In addition, a certain process structure or related auxiliary structures are designed in the integral construction process of the brake pad grinding machine, so that the structure of the brake pad grinding machine is relatively complex; if the constructed actual model of the brake pad grinding machine is imported into finite element analysis software to establish a finite element model, the meshes for establishing the finite element model are divided into finite element units which have little influence on structural performance analysis, and meanwhile, the mesh division difficulty is increased. Therefore, before the constructed model of the brake pad grinding machine is imported into finite element analysis software, the structure of the brake pad grinding machine needs to be simplified to a certain extent under the condition that the machining precision is not influenced; the concrete simplification is as follows:

firstly, an auxiliary structure which is subjected to small acting force or even no acting force in a brake pad grinding machine is removed; secondly, relevant process structures in the brake pad grinding machine are removed, such as chamfers, fillets, threads and the like; thirdly, replacing small taper, small curvature and the like in the brake pad grinding machine by adopting a plane; and fourthly, removing small-sized holes, such as bolt holes, positioning holes and the like in the brake pad grinding machine.

The bed of the brake pad grinding machine supports the whole inner arc grinding machine, and the grinding device of the brake pad grinding machine moves on the n-shaped bracket and plays a supporting role for the grinding device; if the bed of the brake pad grinding machine is greatly deformed under the action of load, the grinding precision of the brake pad grinding machine on the drum type brake pad is reduced, and the brake pad grinding machine is seriously damaged; if the rigidity of the main shaft of the grinding device is insufficient, the rotation precision is affected, and the machining precision of the drum brake pad is affected. Therefore, the machine body, the operating platform and the grinding device spindle of the brake pad grinding machine need to be subjected to mechanical analysis, and relevant characteristics of the machine body, the operating platform and the grinding device spindle are analyzed, so that the whole design and construction process of the brake pad grinding machine is conveniently completed; the process of establishing a finite element analysis model for the bed, the operating platform and the grinding device spindle of the brake pad grinding machine is as follows:

firstly, defining unit types, and when carrying out finite element analysis, firstly, selecting a unit type which is suitable for specific analysis according to the geometric shape, the analysis type and the precision requirement of the analyzed problem; the invention selects a ten-node tetrahedral solid structure unit for analyzing the performance of the brake pad grinding machine component, and calculates the three-dimensional problem.

And secondly, defining the material attribute of the component, and analyzing the related performance of the brake pad grinding machine component by considering the elastic modulus and the density of the defined component material, wherein key components of the brake pad grinding machine comprise a grinding machine body, an operating platform and a main shaft of a grinding device of the grinding machine, and are made of steel.

And thirdly, dividing the mesh, namely dividing the mesh for the three-dimensional solid model imported through the data interface between the SolidWorks software and the finite element analysis software, and generating the finite element model consisting of nodes and units.

Constraint is applied, constraint conditions need to be set for static and dynamic performance analysis of the brake pad grinding machine, analysis results are different along with different set constraint conditions, and constraint meeting actual conditions needs to be applied to the obtained accurate analysis results; the invention mainly analyzes the static and dynamic performance of key parts of the brake pad grinding machine, so that the constraint condition is applied to the key parts: the whole freedom degree is restricted to the connection surface of the operation table and the machine body, the freedom degree of the grinding device spindle except the rotation along the axis is restricted, the bottom surface of the machine body of the grinding machine is fixed, and the whole freedom degree is restricted to the bottom surface.

Thirdly, analyzing the structural static force characteristics of the inner arc grinding machine for the drum brake pad

According to the established finite element model of the drum brake pad inner arc grinding machine, deformation of a brake pad grinding machine part under the action of static load in the grinding process is analyzed, the grinding machine body is the basis of the whole brake pad grinding machine, smooth grinding processing of a brake pad is guaranteed, and the rotation precision characteristic of a main shaft directly influences the quality of the brake pad produced by grinding.

Finite element equation for static analysis

The finite element equation of the structural static analysis is established by adopting a variational method, the variational method adopts a partial differential equation to express the field problem, a linear equation is adopted to replace a pan extreme value problem to be approximately solved in the process of solving the partial differential equation, the finite element method divides the structure into units with certain size, and the structure is regarded as being formed by interconnected unit nodes.

The equivalent equation for the static analysis is:

[B]×{μ}＝{A}

[B]×{μ}＝{A^γ}+{A^αformula 2

{ mu } is a displacement vector of the unit node; { A } is a load matrix of the structure; { A^γThe branch load vector is used as the branch load vector; { A^αIs the total external load experienced; n is the number of structural division units; [ Be ]]Is a structural unit stiffness matrix.

{θ^h}＝[Y]×{v}-{^th}

{σ}＝[H]×{θ^thformula 3

In the formula: { theta ]^hIs strain due to stress; [ Y ]]Is a strain-displacement matrix on the node; { v } is the node displacement vector; {^thIs the other strain of the node; { theta ]^thIs the thermal strain vector; { ζ } is the stress vector; [ H ]]Is an elastic matrix.

(II) static analysis of brake pad grinder Key Member

For important components of the brake pad grinder: the static analysis is carried out on the brake pad grinding machine body, the operating platform and the grinding device spindle, the key point is the determination of the load born by the component and the boundary condition, and in order to better determine the influence of the grinding force on the brake pad grinding machine, the static analysis is carried out on each structure in sequence according to the transmission process of the grinding force on each component of the brake pad grinding machine. The grinding force of the brake pad grinding machine is transmitted from the contact surface of the grinding wheel and the drum brake pad to a main shaft of the grinding device for mounting the grinding wheel, a main shaft controlled by a motor in the grinding device, an n-shaped bracket of the brake pad grinding machine and a grinding machine body.

1. Static analysis of a console

During the grinding process of the drum brake block, the operating platform circumferentially fixes the drum brake block, so that the grinding force between the grinding wheel and the drum brake block is directly transmitted to the operating platform through the drum brake block. The grinding wheel of the brake pad grinding machine grinds the drum brake pad along an arc line through a guide rail and a ball screw in the vertical and horizontal directions, the influence of grinding force on an operating platform is changed, when a grinding device grinds the lowest point of the drum brake pad, the influence of the grinding force on the operating platform is the largest, therefore, the position is selected to analyze the static performance of the operating platform, an equivalent strain distribution diagram of the operating platform is obtained through finite element analysis software, the maximum deformation of the operating platform of the brake pad grinding machine appears on a stop block on one side of the operating platform, the grinding force is generated when the brake pad grinding machine grinds the brake pad, and the component tangential grinding force of the grinding force extrudes the stop block on one side of the operating platform through the brake pad. Although the tangential grinding force is much smaller than the radial grinding force, the action plane of the tangential grinding force is much smaller than the action plane of the radial grinding force on the operating platform through the brake pad, so that the maximum deformation is generated at the position, the maximum deformation is 0.0076mm, the deformation is very small and can be ignored, and the structural design of the drum type brake pad inner arc grinding machine meets the stress requirement.

Fourthly, analyzing the structural power characteristics of the inner arc grinding machine for the drum brake pad

The static analysis of the brake pad grinding machine mainly includes that the gravity of the brake pad grinding machine and the grinding force generated in the grinding process are approximately equivalent to static loads, and the performance of the brake pad grinding machine under the action of the static loads is analyzed. However, during the actual grinding process of the drum brake pad, the vibration of the drum brake pad will cause the brake pad grinder to vibrate due to the existence of the motor. The vibration of the brake pad grinder affects the grinding precision of the drum brake pad, and even affects the normal operation of the brake pad grinder seriously. Therefore, after the key components of the brake pad grinder are subjected to static analysis, the key components are subjected to dynamic analysis, and the dynamic characteristics of the key components are analyzed.

Finite element method structure dynamic characteristic analysis

1. Finite element equation for kinetic analysis

In the finite element method-based static analysis, the displacement of a unit inner point is described by a shape function M and a unit node displacement v as follows:

a (x, y, z) M v formula 4

The strains that occur are:

g v formula 5

The stress to which it is subjected is:

ζ ═ G hv formula 6

In the formula: g is a strain-displacement matrix on the node; h is an elastic matrix;

the dynamic equilibrium equation of the structure is:

in the formula: n is a system quality matrix; b is a system total stiffness matrix; o is a system damping matrix;

is a unit node acceleration matrix;

is a unit node velocity matrix; v is a unit node displacement matrix.

2. Dynamic modal analysis

The modal analysis determines the natural frequency of the structural vibration caused by external excitation and the corresponding mode shape, which are important parameters for designing a structure with relatively small influence on the machining precision under the dynamic load. Modal analysis is also an analytical process that must be done before transient dynamics analysis, modal superposition harmonic response analysis, and spectral analysis.

Identifying an undamped vibration system based on modal analysis as:

in the formula: [ B ]]Is a structural stiffness matrix; [ N ]]Is a quality matrix;

is a unit node acceleration matrix; v is a unit node displacement matrix;

using amplitude X, frequency omega and initial phase

The displacement of the node is expressed in matrix form:

in the formula: { X } is a node amplitude matrix in a cell;

derivation of equation 16 over time can be found:

equation 9 and equation 10 are calculated by taking equation 8:

[B]{X}＝ω²[N]{ X } formula 11

The characteristic equation of equation 11 is:

det([B]-ω²[N]) 0-0 formula 12

The natural frequency of the i-th order mode can be obtained by solving equation 12.

Dynamic analysis of brake pad grinder key component

The maximum rotating speed of a motor of the brake pad grinding machine is 3000r/min, the action frequency of an exciting force caused by the motor is low, each vibration system has a plurality of different high-order modes or low-order modes, the natural frequency of the high-order modes appearing on the brake pad grinding machine exceeds the frequency of the exciting force which possibly appears on the brake pad grinding machine, so that the influence on the grinding stability of the brake pad grinding machine is small, and the requirements for determining the structure dynamic performance of each key part of the brake pad grinding machine can be met only by considering the natural frequency of the low-order modes in the analysis of the relevant modes of each key part.

1. Console modal analysis

The brake pad grinding machine operating platform is directly acted by grinding force through the brake pad, and the vibration of the brake pad directly influences the grinding machining precision of the drum brake pad. And (3) fully constraining the joint surface of the operating platform and the brake pad grinding machine according to the fixed condition of the operating platform, and carrying out modal analysis on the basis to obtain the front four-order frequency and the vibration mode of the operating platform of the brake pad grinding machine.

The first-order vibration mode of the operation table has larger deformation, which is the influence result of the analysis tangential grinding force of the grinding force borne by the baffle on one side of the operation table; the second and third vibration modes of the operating platform can be obtained, and the operating platform is twisted along the X-axis direction under the influence of the vibration of the driving motor; according to the four-order mode vibration mode, the operation table is bent along the Y-axis direction; when the inner arc surface of the drum brake pad is ground and processed by the inner arc forming grinder, the operating platform does not affect the processing precision of the drum brake pad due to the resonance with the driving motor.

2. Brake pad grinding machine bed mode analysis

The static performance of the brake pad grinder bed is stable, so the dynamic performance of the bed is a main factor influencing the performance of the brake pad grinder bed. Simplifying and establishing a finite element model for the solid model of the bed body, limiting all degrees of freedom of the bottom surface of the grinding machine, and carrying out modal analysis on the finite element model to obtain the front four-order frequency and the vibration mode of the inner arc grinding machine of the drum brake pad;

the first-order vibration frequency of the lathe bed is relatively small but is greater than the excitation frequency; and the natural frequency of the grinder frame is increased along with the increase of the order, and the grinding structure of the brake pad meets the design and construction requirements. The first four-order vibration modes are local vibration, the first and second-order vibration modes appear at the feeding part of the drum brake pad, and have no influence on the processing precision of the drum brake pad, but the third and fourth-order vibration modes of the grinder body appear at the grinding position of the drum brake pad, the deformation is large, the grinding precision of the inner arc surface of the drum brake pad is greatly influenced, and the three-order and four-order vibration modes are weak links in the construction and design process of the brake pad grinder and need to be structurally improved.

Structure of improved drum brake pad inner arc grinding machine

A finite element model is established for key parts of the brake pad grinding machine, and dynamic and static performance analysis is carried out, so that the grinding force of the inner arc surface of the brake pad is not large, the static characteristics of the key parts of the brake pad grinding machine are stable, and the deformation and stress levels are low. However, the driving motor is excited to cause the vibration of all the structures of the grinding machine, the first four-order vibration frequency of the bed of the grinding machine is relatively small and is local vibration, the third and fourth-order vibration appears at the grinding position of the brake pad, the processing precision is greatly influenced, the three-order and the fourth-order vibration are weak links designed for the inner arc grinding machine of the drum brake pad, the stress distribution is uneven, and the structure has certain size allowance. Therefore, the invention aims at the weak link of the brake pad grinding machine to improve the structure so as to reduce the quality of the brake pad grinding machine, improve the static and dynamic characteristics of the parts and obtain the drum brake pad inner arc grinding machine with better performance.

Improved lathe bed structure

The brake pad grinding machine constructed and designed by the invention mainly performs grinding processing on the inner arc surface of the drum brake pad, the grinding amount is 2-5 mm, and under the condition of small grinding force, the static rigidity of the grinding machine body is relatively stable, but vibration is caused by excitation of a driving motor, and the third-order vibration and the fourth-order vibration are particularly prominent. The dynamic performance of the grinder body directly influences the processing precision of the inner arc surface of the brake pad. Based on basic size parts of the bed of the brake pad grinder, the dynamic performance of the parts is taken as a structural improvement optimization target.

1. Layout of bed rib plate

The reinforcing ribs comprise transverse ribs, longitudinal ribs, diagonal ribs and combined ribs according to different rib plate arrangement forms.

(1) Transverse and longitudinal ribs

First, perpendicular bending moment of inertia, when horizontal muscle is applyed to the lathe bed, when the thickness of gusset plate was far less than structure length, the moment of inertia of gusset can neglected, and outside curb plate mainly bears the moment of flexure, and when vertical muscle was applyed to the lathe bed, when the moment of flexure that it bore was great, vertical muscle and two side lathe beds backup pads all can bear the effort.

The second is horizontal bending inertia moment, when the structure bears the action of bending moment in the horizontal direction, the horizontal bending deflection a of the transverse rib plate can be converted by adopting an empirical formula_xExpressed as:

in the formula: m is the number of the rib plates; w is the length of the side plate;₁the thickness of the rib plate.

Thirdly, the torsional polar inertia moment of the transverse rib plate perpendicular to the torsional center is smaller and can be ignored under the action of torque; the torsional moment of inertia of the two side plates is only calculated, and the torsional rigidity Y of the two side plates_nExpressed as:

Y_n＝2βBd³w formula 14

In the formula: b is the shear modulus of the structural material; β is a torsional constant, β is 1/3; w is the length of the side plate; d is the frame structure height; the thickness of the rib plate;

assuming that the spacing distance between the transverse rib plates is g and the number of the baffle plates is m, W is mg, and thus formula 14 is expressed as:

Y_n＝2Bd³/3mg of formula 15

Therefore, the torsional rigidity of the longitudinal rib plate structure is greater than that of the transverse rib plate structure.

(2) Calculating torsional stiffness of diagonal ribs

The total torsional rigidity of the diagonal rib is the sum of the rigidity of the diagonal rib and the rigidity of the frame, and the torsional rigidity Y of the diagonal rib plate_iExpressed as:

in the formula: m is the number of diagonal ribs; i is the modulus of elasticity; the thickness of the rib plate;

if the torsional rigidity of the side plate is known to be Y_nThe torsional stiffness of the diagonal rib frame structure is expressed as:

the second term is the torsional stiffness of the diagonal rib plate which is improved compared with the transverse rib plate.

2. Determining structural dimensions of a rib plate

Deformation of the grinding machine body of the brake pad caused by excitation of the driving motor mainly occurs at a transmission part and a grinding position of the brake pad, the deformation direction is mainly in the X direction, and a transverse rib plate is applied to the grinding machine body under the condition of deformation of the grinding machine body at the grinding position of the brake pad. The method is characterized in that the first four-order natural frequency and the vibration mode are taken as targets, the performance of the rib plate of the grinder body is researched, a better structure improvement method is obtained through analysis and comparison, and as the rib plate is not applied to the grinder body of the brake pad grinder which is initially constructed and designed, the following two improvement schemes are designed for researching the change situation of the performance of the grinder body after the rib plate is applied:

(1) the rib plate improvement scheme I: applying a transverse rib plate at the grinding position of the brake pad;

(2) the second rib plate improvement scheme: and respectively applying a transverse rib plate at the grinding and feeding positions of the brake pad.

The method is characterized in that a finite element model is established on the grinder body in two improved schemes for modal analysis, the vibration conditions of the grinder body in each scheme after the improvement are basically consistent with those of the original grinder body, but the corresponding natural frequency is improved to a certain extent, through the modal analysis results of three schemes including the original grinder body, the rib plate improved scheme I and the rib plate improved scheme II, the natural frequency of the grinder body can be improved by applying the transverse rib plate, and meanwhile, the amplitude of the natural frequency of the grinder body can be improved by applying the transverse rib plate at the grinding and feeding positions of the brake pad. In addition, a transverse rib plate is applied to the grinding and feeding part of the brake pad, so that the vibration deformation caused by the excitation of a driving motor is obviously reduced, and compared with the original bed mode analysis result, the dynamic performance of the grinding machine bed body is greatly improved at the grinding part after the transverse rib plate is applied, so that the processing precision of the brake pad grinding machine is ensured. And (3) performing static analysis on the grinding machine body on which a transverse rib plate is respectively applied at the grinding and feeding positions of the brake pad to obtain the static characteristics including deformation and stress of the grinding machine body of the brake pad.

And (3) performing static analysis on the grinder body of the second rib plate improvement scheme, wherein the maximum deformation of the grinder body applying the second transverse rib plate under the action of static load is 0.003mm, the maximum stress is 0.45MPa, and the deformation of the grinder body of the drum brake pad under the action of static load is small and can be ignored. Therefore, the static performance of the grinding machine is excellent, but the weight of the bed of the grinding machine is large, a certain size allowance exists in the structure, the static performance of the bed is researched on the basis of ensuring that the dynamic performance is improved to a certain extent by taking the front four-order natural frequency of the bed of the grinding machine as a target, and a better improvement scheme of the bed structure is obtained through analysis and comparison.

The static and dynamic performance of the brake pad grinding machine is greatly improved by applying the transverse rib plates, but the mass of the machine body is increased due to the application of the rib plates, and the machine body performance is affected due to the fact that the machine body is inconvenient to manufacture and process due to the fact that the machine body is too large in mass. Therefore, in order to avoid the stress concentration generated in the working process of the grinding machine on one hand and reduce the overall quality of the grinding machine and improve the performance of the grinding machine on the other hand, the wall thickness of the machine body and the wall thickness of the rib plate are controlled within a certain range, and in order to improve the performance of the machine body of the grinding machine after the transverse rib plate is applied, the following three structure improvement schemes are designed:

(1) the first structural improvement scheme is as follows: the wall thickness of the lathe bed and the thickness of the rib plate are reduced by 2 mm;

(2) the structural improvement scheme II: the wall thickness of the lathe bed and the thickness of the rib plate are reduced by 4 mm;

(3) the structural improvement scheme is three: the wall thickness of the lathe bed and the thickness of the rib plate are reduced by 6 mm;

and establishing a finite element model for the machine body of each structural improvement scheme for carrying out the mode, wherein the mode shapes of the machine body of each improved scheme are basically consistent with those of the machine body of the second structural improvement scheme of the rib plate, but the natural frequency of the first four orders is obviously changed. The reduction of the wall thickness of the bed body and the thickness of the rib plate causes the reduction of the first four-order natural frequency of the bed body of the grinding machine in the second improvement scheme of the rib plate, compared with the original bed body, the dynamic performance of the bed body is obviously improved, but the deformation of the bed body of the grinding machine under the action of the load and the driving motor is continuously enlarged along with the continuous reduction of the thickness.

3. Improved structure of machine tool body

Aiming at weak links in static and dynamic performances of the brake pad grinder body, analyzing the layout of rib plates of the grinder body structure, the number of the rib plates, the grinder body and the thickness of the rib plates to obtain a final brake pad grinder body structure improvement scheme: applying a transverse rib plate on the feeding and grinding part of the brake pad on the grinder body, and reducing the wall thickness of the grinder body and the thickness of the rib plate by 4mm to obtain a new grinder body with the first-order frequency of 256.49Hz and the first-order natural frequency of the grinder body improved by 46.1%; the weight of the new lathe bed is 720.1Kg, the weight of the lathe bed is reduced by 20.3 percent, and the improvement of the lathe bed structure achieves good effect.

(II) improved operation table structure

Under the condition that the received grinding force is not large, the static rigidity of the operating platform of the brake pad grinding machine is good, the generated main deformation is caused by the equivalent action of the grinding force of the grinding wheel acting on the drum type brake pad, and the frequency of the operating platform of the brake pad grinding machine, which generates vibration under the excitation of the driving motor, is larger than the frequency of the driving motor, so that when the brake pad grinding machine works, the operating platform is difficult to generate resonance under the excitation of the driving motor, the processing precision of the brake pad grinding machine cannot be influenced, but through the analysis of a stress distribution diagram and a strain distribution diagram, the structural deformation of the bottom of the operating platform is relatively small, and a certain. Aiming at the problem that the size allowance exists in the operating platform structure, the operating platform structure is improved through a topological optimization method, the quality of the operating platform structure is reduced under the condition that the basic size is not changed, the static performance of the operating platform structure is improved, and the overall performance of a brake pad grinding machine is improved.

1. Operation platform topology optimization method

The structural topology optimization is in a given material quality and design domain, the structural layout which meets constraint conditions and enables an objective function to be optimal is obtained through an optimization design method, the initial constraint conditions of the topology design are fewer, a designer only needs to put forward the design domain without knowing a specific structural topology form, and the topology design method is an innovative structural topology design method.

The structural topological optimization discusses the interconnection mode of structural members, and the structural position topological form has holes or not, so that certain performance indexes (such as rigidity and weight) of the structure can be optimized under the constraint conditions of strength, rigidity and stability. The structural topology optimization schematic is shown in fig. 3 and 4. Knowing that the topological optimization space is S, wherein the optimal topological structure is S ', if S ' is unknown, S can be divided into a plurality of small micro-elements, then an optimization design method is adopted to calculate whether each micro-element is reserved or removed, and finally the reserved micro-elements are approximate solutions of the optimal topological structure S '. If the concept of virtual density is introduced: the reserved micro element virtual density is called as 1, the removed micro element virtual density is called as O, the virtual density X of all micro elements in the design space is taken as a design variable, and then the mathematical model of the structural topology optimization is expressed as:

solving the following steps: x ═ X₁，x₂，……，x_n}^TFormula 18

The following steps are performed: min B₀(X) formula 19

Satisfies the following conditions: b is_j(X) 0 j ≦ 1, 2, …, E20

Wherein n is the number of design variables; b is₀(X) is an objective function; b is_j(X) is a constraint equation; e is the number of constraint equations。

In the optimization model, the number of the microelements is limited, the virtual density of each infinitesimal is independently changed, the optimization result may have a jagged result, and the topological optimization result cannot be directly used for production and manufacturing and must be subjected to manufacturable processing; the initial constraint conditions of topological optimization are less, so that the optimization potential is greater relative to size optimization and shape optimization if the method is applied to light weight.

The structural topology optimization is divided into two types of discrete topology optimization and continuous topology optimization, in the process of the discrete topology optimization, a base structure is selected firstly, then the optimal layout position of components in the base structure is determined through an optimization searching method, or the optimal layout position of the components in the base structure is determined, or the optimal layout position of the components is determined, which components need to be reserved and which components can be removed, n components in the base structure need to be determined to have the existing state through optimization, and a variable x is used for determining the existing state of the components_i(i-1, 2, …, n) denotes that when the ith member is present in the optimum configuration, X_iTake 1, and take 0 in the absence. If X is ═ X₁，x₂，……，x_n)^TFor optimizing the design variables, the discrete result topology optimization model is:

solving the following steps: x ═ X₁，x₂，……，x_n)^TFormula 21

The following steps are performed: min A (X) formula 22

Satisfies the following conditions:

wherein A (x) is an objective function; b_j(X) is an inequality constraint; m is the number of inequality constraints; d_i(X) is an equality constraint; n is the number of inequality constraints.

The continuous topological optimization process is that firstly, a topological optimization design space of the structure is established, namely, which structural regions participate in optimization and which structural regions do not participate in optimization are determined, corresponding load and boundary conditions are applied, then, an effective topological optimization algorithm is selected for optimization, invalid or inefficient materials are gradually removed in the optimization process, and the rest structure gradually tends to the optimal structure. The methods for solving the topology optimization of the continuum structure include a variable thickness method, a uniform method and a variable density method.

2. Operating floor structure topology optimization

The bottom structure of the operating platform has small deformation under the action of load and certain size allowance. Therefore, structural improvement is made with respect to the dimensional margin thereof. And determining the optimal improvement scheme of the operating platform by comparison and analysis by taking the deformation of the brake pad grinding machine and the first four-order vibration frequency as optimization targets.

Through to braking piece grinding machine operation panel structural analysis, for the abrasive machining of guarantee realization to braking piece intrados, the operation panel upper surface design is circular-arc to the structure vertical height minimum is 40mm, can realize satisfying the grinding of required precision at the operation panel for guaranteeing drum-type braking piece, and the topological optimization degree of lightweight structure of operation panel can not be too big, for three kinds of improvement schemes of the performance design of braking piece grinding machine in the operation panel optimization process:

(1) the first optimization scheme of the operation platform is as follows: the operation platform is reduced by 10% in topological optimization;

(2) and (2) optimizing a second operating platform: reducing the weight by 20% through topological optimization of the operating platform;

(3) and the third optimization scheme of the operation platform is as follows: reducing the weight by 30% through topological optimization of the operating platform;

optimizing three operation table structure improvement schemes by adopting a topological optimization function of Design Xplorer in Ansys Workbench software, changing an operation table model according to a topological optimization calculation result, and finally performing statics and modal analysis on the changed operation table model, wherein the analysis result is as follows: under the condition that the overall size is kept unchanged, along with the continuous reduction of the weight of the bottom structure of the operating platform, the deformation of the operating platform under the action of the grinding force equivalent acting force and the self gravity is gradually increased, but the maximum deformation of the operating platform in the third operating platform optimization scheme with the maximum light weight degree of the operating platform is 0.03mm at most, the maximum stress is 3.51MPa, the maximum stress is relatively small, and the grinding machining of the drum brake pad is hardly influenced.

With the continuous reduction of the weight of the bottom structure of the operation table, the vibration frequency generated by the operation table at the driving motor is sequentially reduced, but the lowest frequency in the optimization schemes of the operation table is greater than the frequency of the driving motor, so the three optimization schemes of the operation table cannot generate resonance due to the excitation of the driving motor.

3. Improved structure of operation table

Aiming at weak links expressed in static and dynamic analysis of the brake pad grinding machine operating platform, the weak links are analyzed through three different topological optimization schemes, and the final structural improvement scheme of the drum brake pad inner arc grinding machine operating platform is obtained as an operating platform optimization scheme III: the quality of the operation table with the improved structure is reduced by 30 percent, the quality is greatly reduced, and the static performance is obviously improved; and the first-order natural frequency of the improved operating platform is 161.96Hz which is higher than the frequency of the driving motor, so that the influence of vibration caused by the excitation of the driving motor on the machining precision of the drum brake pad is avoided.

The invention aims at the structural improvement of weak links in the static and dynamic performance analysis process of the drum brake pad inner arc grinding machine. The method comprises the steps of firstly researching factors influencing the performance of the brake pad grinder body, then providing a plurality of different improvement schemes based on a control factor method, carrying out relevant dynamic and static performance analysis on the schemes, comparing and comparing the performances, finally determining the improvement scheme of the brake pad grinder structure, and simultaneously explaining the improvement result of the brake pad grinder structure. Through the structural improvement, the static and dynamic performance of the brake pad grinding machine is improved, and the drum brake pad inner arc grinding machine with better performance is obtained.

Claims

1. The method for improving the structure of the drum brake pad high-precision inner arc grinding machine is characterized by comprising the steps of firstly establishing a solid model of the drum brake pad inner arc grinding machine, then realizing static analysis of the inner arc grinding machine based on a finite element analysis method, then analyzing the structural power characteristics of the drum brake pad inner arc grinding machine, and finally improving the structure of the drum brake pad inner arc grinding machine;

2. The structural improvement method of the drum brake pad high-precision inner arc grinding machine according to claim 1, characterized in that in the grinding structure of the brake pad grinding machine, the grinding assembly of the brake pad grinding machine mainly grinds the inner arc surface of the drum brake pad, mainly comprising a motor, a transmission system and a grinding wheel, the grinding wheel in the grinding assembly of the brake pad grinding machine is controlled by a three-phase asynchronous motor to realize continuous grinding of the inner arc surface of the drum brake pad, and power transmission is realized by a synchronous belt; grinding assembly of a brake pad grinding machine is carried out, wherein a bottom machine body of a grinding device and the bottom of a bearing grinding device are arranged to be arc-shaped;

3. The structural improvement method of the drum brake lining high-precision inner arc grinder according to claim 1, is characterized in that in the brake lining feeding device, the brake lining conveying device comprises a brake lining hopper, a conveying guide rail and a cylinder, and the brake lining from the previous device is conveyed to the clamping device of the drum brake lining; the brake pad conveying device is arranged on the inner arc grinding machine body on one side different from the grinding device; after the grinding machine is started, the air cylinder drives a pushing block on the guide rail to push a drum brake piece at the bottommost layer of the hopper to a brake piece clamping device, the air cylinder drives the pushing block to return to an initial position after the brake piece is completely pushed out of the hopper, and the air cylinder drives the pushing block to reciprocate back and forth to feed the brake piece;

4. The method for improving the structure of the drum brake pad high-precision inner arc grinding machine according to claim 1, characterized in that a brake pad grinding machine finite element model is established on the basis of a solid model of the drum brake pad inner arc grinding machine, and material properties, selection units, grid division, boundary constraint and load application are defined according to structural materials;

firstly, the grinding force of the brake pad grinding machine is analyzed, and the brake pad grinding machineDuring the grinding process, the force between the grinding wheel and the drum brake pad is the grinding force, and the grinding force a of the grinding wheel can be decomposed into three components perpendicular to each other: feed grinding force A in axial direction_fGrinding force A in the tangential direction of the grinding wheel_cRadial cutting force A in the normal direction_pThe grinding force of the grinding wheel to the drum brake pad is as follows:

A＝0u_ωf_pa_aformula 1

5. The method for improving the structure of the drum brake pad high-precision inner arc grinding machine according to the claim 1 is characterized in that the invention adopts SolidWorks software to establish each part model of the drum brake pad inner arc grinding machine, assembles each part into a corresponding mechanical system device according to the overall design of the brake pad grinding machine, and finally assembles the device into the integral model of the drum brake pad inner arc grinding machine; introducing a structural model of the brake pad grinding machine, which needs to be analyzed for performance, into finite element analysis software by adopting a data interface between SolidWorks software and the finite element analysis software to establish a finite element model;

6. The method for improving the structure of the drum brake pad high-precision inner arc grinding machine according to claim 1 is characterized in that a variational method is adopted to establish a finite element equation for structural static analysis, the variational method adopts a partial differential equation to express a field problem, a linear equation is adopted to replace a pan extreme value problem to be approximately solved in the process of solving the partial differential equation, the finite element method divides the structure into units with a certain size, and the structure is regarded as being formed by unit nodes which are connected with each other;

the equivalent equation for the static analysis is:

[B]×{μ}＝{A}

[B]×{μ}＝{A^γ}+{A^αformula 2

{ u } is a displacement vector of the unit node; { A } is a load matrix of the structure; { A^γThe branch load vector is used as the branch load vector; { A^αIs the total external load experienced; n is the number of structural division units; [ Be ]]Is a structural unit stiffness matrix;

{θ^h}＝[Y]×{v}-{^th}

{σ}＝[H]×{θ^thformula 3

In the formula: { theta ]^hIs strain due to stress; [ Y ]]Is a strain-displacement matrix on the node; { v } is the node displacement vector; {^thIs the other strain of the node; { theta ]^thIs the thermal strain vector; { σ } is the stress vector; [ H ]]Is an elastic matrix;

7. The structural improvement method of the high-precision inner arc grinding machine for the drum brake pad according to claim 1 is characterized in that the brake pad grinding machine operating platform is directly acted by grinding force through the brake pad, and the vibration of the brake pad directly influences the grinding machining precision of the drum brake pad; according to the fixed condition of the operating platform, the combined surface of the operating platform and the brake pad grinding machine is subjected to full constraint, and modal analysis is performed on the basis to obtain the first four-order frequency and the vibration mode of the operating platform of the brake pad grinding machine: the first-order vibration mode of the operation table has larger deformation; the second and third vibration modes of the operating platform can be obtained, and the operating platform is twisted along the X-axis direction under the influence of the vibration of the driving motor; according to the four-order mode vibration mode, the operation table is bent along the Y-axis direction; when the inner arc surface of the drum brake pad is ground and processed by the inner arc forming grinder, the operating platform cannot influence the processing precision of the drum brake pad due to the resonance with the driving motor;

8. The method for improving the structure of the drum brake pad high-precision inner arc grinding machine according to claim 1, characterized in that the improved bed structure is based on basic size components of the bed of the brake pad grinding machine, and the dynamic performance of the improved bed structure is taken as a structural improvement optimization target;

9. The method for improving the structure of the drum brake pad high-precision inner arc grinding machine according to claim 8 is characterized in that the wall thickness of the machine body and the wall thickness of the rib plate are controlled within a certain range, and the following three structure improvement schemes are designed for improving the performance of the machine body of the grinding machine after the transverse rib plate is applied: the first structural improvement scheme is as follows: the wall thickness of the lathe bed and the thickness of the rib plate are reduced by 2 mm; the structural improvement scheme II: the wall thickness of the lathe bed and the thickness of the rib plate are reduced by 4 mm; the structural improvement scheme is three: the wall thickness of the lathe bed and the thickness of the rib plate are reduced by 6 mm;

10. The method for improving the structure of the high-precision inner arc grinding machine for the drum brake pad according to claim 1, is characterized in that the structure of the operation platform is improved through a topological optimization method, the mass of the operation platform is reduced under the condition that the basic size is not changed, the static performance of the structure of the operation platform is improved, and the overall performance of the grinding machine for the brake pad is improved; carrying out structural improvement on the size allowance, and determining an optimal improvement scheme of an operation table through comparative analysis by taking the deformation of the brake pad grinding machine and the first four-order vibration frequency as optimization targets;