CN109375578B - Efficient machining control method for deep hole in engine oil pump shell - Google Patents
Efficient machining control method for deep hole in engine oil pump shell Download PDFInfo
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- CN109375578B CN109375578B CN201811288538.1A CN201811288538A CN109375578B CN 109375578 B CN109375578 B CN 109375578B CN 201811288538 A CN201811288538 A CN 201811288538A CN 109375578 B CN109375578 B CN 109375578B
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- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
- G05B19/00—Programme-control systems
- G05B19/02—Programme-control systems electric
- G05B19/18—Numerical control [NC], i.e. automatically operating machines, in particular machine tools, e.g. in a manufacturing environment, so as to execute positioning, movement or co-ordinated operations by means of programme data in numerical form
- G05B19/19—Numerical control [NC], i.e. automatically operating machines, in particular machine tools, e.g. in a manufacturing environment, so as to execute positioning, movement or co-ordinated operations by means of programme data in numerical form characterised by positioning or contouring control systems, e.g. to control position from one programmed point to another or to control movement along a programmed continuous path
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- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
- G05B2219/00—Program-control systems
- G05B2219/30—Nc systems
- G05B2219/35—Nc in input of data, input till input file format
- G05B2219/35349—Display part, programmed locus and tool path, traject, dynamic locus
Abstract
The invention discloses a method for controlling efficient machining of deep holes in a pump shell of an engine oil pump, which comprises the following stepsThe method comprises the following steps: calculating to obtain a modal transfer function of the cutting machining system; according to the machining depth, a row of points are uniformly and sequentially arranged from the tool nose to the tail end of the tool bar at intervals, and modal transfer functions of all nodes of the tool are sequentially obtained through a modal test; establishing cutting processing transfer functions phi of different nodes of the cutter through the modal transfer function of the cutting processing system and the modal transfer function of each node of the cutter1iWill phi1iObtaining phi through Laplace transform1i(s); according to phi1i(s) obtaining stable areas in the cutting process of the cutter under different nodes by a method of solving the stable areas through a frequency domain; and carrying out efficient and stable machining on the workpiece according to the cutting parameters of the stable region. The design accurately obtains the optimal cutting parameters according to the dynamic characteristics of the cutter and the workpiece, optimizes the cutting path, realizes efficient and stable deep hole processing, and improves the processing stability in the cutting process and the surface quality of the workpiece.
Description
Technical Field
The invention relates to a mechanical deep hole machining method, in particular to a method for efficiently machining and controlling a deep hole in a pump shell of an oil pump.
Background
The internal structure of the engine oil pump shell is complex, and the surface appearance and residual height of the deep hole inside the engine oil pump shell become important factors for improving energy efficiency due to the fact that lubricating cooling liquid circularly flows in the internal pipeline of the engine oil pump shell. Due to the limitation of the diameter of the cutter and the requirement of the cantilever length of the deep hole cutter, the cutter is low in rigidity and difficult to machine with high material cutting efficiency, and in order to meet the machining requirement, more procedures are adopted in the traditional deep hole machining process, so that the cutting efficiency is low.
Disclosure of Invention
The present invention aims to solve the above technical problem at least to some extent. Therefore, the invention provides a method for efficiently processing and controlling a deep hole in a pump shell of an engine oil pump.
The technical scheme adopted by the invention for solving the technical problems is as follows: a method for controlling the efficient machining of deep holes in a pump shell of an engine oil pump comprises the following steps:
s1, calculating and obtaining a modal transfer function H of the cutting system according to a cutting system kinetic equation1(ω,n)；
S2, depending on the processing depth,set up a row of points from the knife tip to the terminal interval of cutter arbor evenly in proper order, k points altogether, mark in proper order: 1,2,3, …, k, sequentially obtaining the modal transfer function of each node of the cutter through a modal test, and setting the modal transfer function as H3i(ω1),i＝1,2,3,…,k；
S3, establishing a cutting processing transfer function phi under different nodes of the cutter through the modal transfer function of the cutting processing system and the modal transfer function of each node of the cutter1iWill phi1iObtaining phi through Laplace transform1i(s)；
S4, according to phi1i(s) obtaining stable areas in the cutting process of the cutter under different nodes by a method of solving the stable areas through a frequency domain;
and S5, performing efficient and stable machining on the workpiece according to the cutting parameters of the stable region.
Further, the distance between adjacent points in the step S2 is 1 mm.
Further, in the step S3, the phi1iAfter laplace transformation, the following formula is obtained:
h(s) is obtained by performing Laplace transform on the dynamic cutting depth h (t); h is0The ideal cutting depth in cutting; t is the period of cutting, apCutting width, k2The coefficient of tangential cutting force under the ultrasonic vibration assistance condition.
Further, the relationship of h (t) is as follows:
h(t)＝h0-[(h2(t)-h1(t))-(h2(t-T)-h1(t-T))]；
wherein h is2(T-T) represents the depth of cut, h, of the previous tooth machining of the tool2(t) represents the depth of cut, h, of the current tooth of the tool being machined1(t) represents a depth of cut due to workpiece deflection caused by workpiece vibration, h1(T-T) represents the depth of cut due to workpiece deflection caused by workpiece vibration in the previous cycle.
Further, the cutting force F during cutting2(t) is related to h (t) as follows:
F2(t)＝k2·h(t)·ap+ap·k3
wherein, F2(t) the following relationship can be obtained from the kinetic equation of the cutting example:
the dynamic depth of cut h (t) is subjected to laplace transform to obtain:
h(s)＝h0-(e-sT-1)(h2(s)-h1(s))
the cutting kinetics equation converts to:
wherein k is3Is the radial cutting force coefficient under the auxiliary condition of ultrasonic vibration, q2Is the displacement of the knife tip, and the knife edge,
the displacement speed of the tool nose is the speed of the tool nose,
is the displacement acceleration of the nose, k2Coefficient of tangential cutting force, M, under ultrasonic vibration assistance2Is the modal mass of the tool.
Furthermore, in the S1, the dynamic equation of the cutting machining system is,
wherein M (omega, n) is a mass matrix of the cutting processing system; k (omega, n) is a rigidity matrix of the cutting machining system; n is the rotating speed, omega is the ultrasonic vibration frequency, D is the equivalent viscous damping matrix; q is the displacement of the node point and,
and
respectively node velocity and node acceleration; f (t) is a node force vector; g and N are respectively a rotation influence coefficient and an ultrasonic vibration influence coefficient.
Further, in the step S1, H1(ω, n) is obtained by: firstly, establishing a finite element model of a cutting processing system, and obtaining a modal transfer function H of the finite element model under boundary conditions of different rotating speeds and ultrasonic vibration frequencies according to a cutting processing system kinetic equation1(ω1) Testing the mode transfer function H of the tool nose under the conditions of no rotation and ultrasonic vibration by experiments2(ω1) (ii) a Then using residual error epsilon minimum pair H1(ω1) And H2(ω1) Fitting to obtain a rigidity matrix K (omega, n) and a damping matrix C (omega, n) under different rotating speeds and ultrasonic vibration frequencies, fitting according to a least square method to obtain a variation function and a modal transfer function H of the rigidity matrix and the damping matrix along with the rotating speeds and the ultrasonic vibration frequencies1(ω,n)；
Wherein
ω2、ω3The minimum value and the maximum value of the cutting excitation frequency of the cutter in the cutting processing system are respectively.
Further, when the machining tool carries out deep hole machining, the rotating speed of the spindle is selected according to the peak value of the cutting depth in the stable area function on different nodes of the cutter, then the cutting depth is selected according to the rotating speed and the corresponding stable areas on different nodes, and the minimum value is selected on the cutting depth of all the nodes, so that efficient and stable machining is realized.
Further, the cutter includes the cutter arbor and the blade of fixed mounting on the cutter arbor, the blade both sides have the cutting edge, be provided with little cutting edge on the cutting edge.
Further, the cutter is connected with the cutter spindle through an ultrasonic vibration auxiliary system, the ultrasonic vibration auxiliary system comprises a first connecting piece and a vibration amplitude transformer, one end of the vibration amplitude transformer is arranged in the first connecting piece, the other end of the vibration amplitude transformer extends out of the first connecting piece to be fixedly connected with the cutter bar or a workpiece, and the vibration amplitude transformer is provided with a pair of piezoelectric actuators for generating axial vibration and transmitting the vibration to the blade
The invention has the beneficial effects that: the optimal cutting parameters are accurately obtained according to the dynamic characteristics of the cutter and the workpiece, the cutting path is optimized, the efficient and stable deep hole machining is realized, and the machining stability and the workpiece surface quality in the cutting process are improved.
Drawings
The invention is further illustrated with reference to the following figures and examples.
FIG. 1 is a schematic view of a tool mounting structure;
FIG. 2 is a cross-sectional view of a blade;
FIG. 3 is a front view of the blade;
FIG. 4 is an enlarged view at A of FIG. 3;
FIG. 5 is a schematic view of the attachment of the first attachment member to the vibrating horn;
FIG. 6 is a schematic view of the construction of the vibrating horn;
FIG. 7 is a sectional view showing a coupling structure of the first coupling member, the vibration horn, and the second coupling member;
fig. 8 is an enlarged view at D of fig. 5.
Detailed Description
The present invention will be described in detail below with reference to the accompanying drawings and examples.
The invention discloses a method for controlling efficient machining of deep holes in a pump shell of an engine oil pump, which comprises the following steps of:
s1, calculating and obtaining a modal transfer function H of the cutting system according to a cutting system kinetic equation1(ω,n)；
S2, according to the processing depth, a row of points are uniformly and sequentially arranged from the tool nose to the tail end of the tool bar at intervals, and k points are totally marked as: 1,2,3, …, k, sequentially obtaining the modal (transfer) function of each node of the cutter through a modal test, and setting the function as H3i(ω1),i＝1,2,3,…,k；
S3 mode transfer function H of cutting system1(omega, n) and the mode transfer function of each node of the cutter, and establishing the cutting processing transfer function phi of different nodes of the cutter1iWill phi1iObtaining phi through Laplace transform1i(s)；
S4, according to phi1i(s) obtaining stable areas in the cutting process of the cutter under different nodes by a method of solving the stable areas through a frequency domain;
and S5, performing efficient and stable machining on the workpiece according to the cutting parameters of the stable region.
The machine tool is a 5-axis numerical control machining center machine tool and comprises a workbench, a cutter, an electric spindle and the like; the control system consists of a control system of the machine tool and an ultrasonic vibration control system; the ultrasonic vibration auxiliary system consists of a vibration amplitude transformer, a piezoelectric actuator, a power supply and an ultrasonic generator, and transmits ultrasonic vibration to the cutter, so that the surface quality of the workpiece is improved.
Each calculation process is described in detail below.
The dynamic equation in the cutting processing system in step S1 is:
wherein: m (omega, n) is a mass matrix of the cutting processing system, is a constant, and can establish a finite element model for a motor, a main shaft, a tool holder and a bearing in the cutting processing system and quickly obtain the mass matrix in finite element software. n is the rotation speed, omega is the ultrasonic vibration frequency, C (omega, n) is the damping coefficient, considers the influence of rotation speed and ultrasonic vibration frequency, can obtain by the experiment of rotation and ultrasonic vibration. And selecting different rotating speed and ultrasonic vibration frequency combination parameters for testing, and obtaining the parameters by fitting according to a least square method. D is an equivalent viscous damping matrix, determined by the properties of the material. q is the nodal displacement, and F (t) is the nodal force vector. G and N are respectively decomposed from a C (omega, N) matrix and represent the influence of rotation and ultrasonic vibration.
Establishing a finite element model of a cutting processing system, and obtaining a modal transfer function H of the finite element model under boundary conditions of different rotating speeds and ultrasonic vibration frequencies1(ω1) Testing the mode transfer function H of the tool nose under the conditions of no rotation and ultrasonic vibration by experiments2(ω1)。
Fitting is carried out according to the formula by using the minimum residual epsilon, so as to obtain a rigidity matrix K (omega, n) and a damping matrix C (omega, n) under the conditions of different rotating speeds and ultrasonic vibration frequencies, and fitting is carried out according to a least square method. Obtaining a variation function and a modal transfer function H of the rigidity matrix and the damping matrix along with the rotating speed and the ultrasonic vibration frequency1(ω，n)。ω2、ω3Minimum and maximum values, typically ω, of the tool-cutting excitation frequency in the machining system, respectively2＝0，ω3＝n·N1，N1N is the number of teeth of the tool, the rotational speed of the machining system.
In the deep hole machining process, a cutter quotient and a contact area of the inner side of a deep hole of a workpiece are scattered into nodes, from a cutter point to the top from the tail end of a cutter rod, points are arranged at intervals of 1mm, and k points are marked sequentially: 1,2,3, …, k. Through a modal test, sequentially obtaining modal (transfer) functions of the nodes, and setting the modal (transfer) functions as follows: h3i(ω1)，i＝1，2，3，…，k。
The machining kinetic equation between the tool and the workpiece is:
q2is the displacement of the knife tip, and the knife edge,
the displacement speed of the tool nose is the speed of the tool nose,
is the displacement acceleration of the nose, k2Coefficient of tangential cutting force, M, under ultrasonic vibration assistance2Is the modal mass of the tool.
h(t)＝h0-[(h2(t)-h1(t))-(h2(t-T)-h1(t-T))]
F2(t)＝-F1(t)
F2(t)＝k2·h(t)·ap+ap·k3
F2(t) is the cutting force generated by the tool during cutting, and F1(t) is a pair of an acting force and a reaction force. h is2(T-T) represents the depth of cut, h, of the previous tooth machining of the tool2(t) the cutting depth, h, of the current tooth of the tool1(t) current depth of cut of workpiece deviation caused by workpiece vibration, h1(T-T) the depth of cut of the previous cycle of workpiece deflection caused by workpiece vibration.
Wherein T is the period of the cut;
h (t) is the dynamic depth of cut;
apthe cutting width is determined according to the total number k of discrete nodes of the area where the cutter contacts the workpiece from the cutting edge and the length L of the area where the cutter contacts the workpiece,
k2the coefficient of tangential (direction parallel to cutting speed) cutting force under ultrasonic vibration assistance.
k3The coefficient of radial (direction perpendicular to cutting speed) cutting force under ultrasonic vibration assistance. Wherein the coefficient of tangential cutting force k under the ultrasonic vibration assistance condition2And k3All can pass through the straight hole under different cutting depthsAngle cutting test and fitting the test data.
The cutting depth h is laplace transformed to obtain:
h(s)＝h0-(e-sT-1)(h2(s)-h1(s))
the cutting kinetics equation converts to:
in the cutting process, under the action of cutting force, transfer functions between the cutter and the workpiece on different nodes are as follows:
Φ1iis transformed into phi by Laplace1i(s)
According to the method for solving the stable region in the frequency domain, the stable region in the cutting process under different nodes on the cutter is solved:
when the processing machine tool carries out deep hole processing, the rotating speed of the main shaft is selected according to the peak value of the cutting depth in the stable area function on different nodes of the cutter, namely different rotating speeds on different nodes of the cutter are obtained, then the cutting depth is selected according to the rotating speed and the stable areas on different nodes, and the minimum value is selected on the cutting depth of all the nodes, so that efficient and stable processing is realized.
In order to better realize high-efficiency machining and improve the surface quality of a workpiece, an optimized cutter and an ultrasonic vibration auxiliary system are adopted for auxiliary machining.
Referring to fig. 1 to 8, the tool of the present invention includes a holder 7 and an insert 8 fixedly mounted on the holder 7, the insert 8 having cutting edges on both sides thereof, and the cutting toolThe blade is provided with a micro cutting edge 83. A plurality of blades 8 are arranged on the cutter bar 7, and the blades 8 are uniformly and fixedly connected on the cutter bar 7 through bolts 81 and gaskets 82. The blades 8 are arranged at intervals along the axial direction of the cutter bar 7, the number of the blades installed on the cutter bar is n, and the blades are arranged according to the depth h of the hole in the cutting process4And the length L of the blade, are determined,
n is an integer. So that the blade can cover the entire depth of the hole. The distance h between adjacent blades is 0.5-1um, which is lower than the axial amplitude of the ultrasonic vibration amplitude transformer.
The cutting edges on two sides are composed of micro cutting edges with the radius of 5-8um microns, the cutting edges are arranged on the left side and the right side, the cutting edges are not arranged at the middle positions of the upper side and the lower side due to the fact that the cutting edges cannot be used in machining, and the cutting edges are not arranged only at the middle 1/2 lengths of the upper side and the lower side and are used for improving machining stability in the cutting process and improving surface quality, such as reducing burrs on the inner surface and the round corners of the deep hole. The joint of the cutting edge is composed of a plurality of arcs with the radius of 1-2 microns, and is used for improving the heat dissipation effect of the blade, improving the surface quality of a workpiece and reducing the cutting force. The front angle C of the blade with a specific structure is 2-3 degrees, the rear angle is 10-15 degrees, the middle of the blade is of an inwards concave structure and is used for installing bolts and gaskets for fixing the blade and the cutter bar, the inwards concave angle is 70-75 degrees, chips are prevented from being deposited in the groove, and the surfaces of workpieces are prevented from being scratched by the chips. The remaining preferred dimensions are a height h2 of 5-6um and h1 of about 10 um. The angle B2 is 25-30 degrees, the angle B3 is 12-15 degrees, the angle B4 is 70-65 degrees, and the angle h3 is 15-18 um.
The cutting edges on two sides of the blade are arranged in a central symmetry mode, so that when the blade is worn in the cutting process, the blade can be directly replaced or one side, which is not worn, of the other side is rotated by 180 degrees and is installed on the cutter bar to be used continuously, the service life of the blade is prolonged, and the processing cost is reduced. The cutter rod is provided with an arc structure 71 for guiding chips, and the angle B1 is an arc of-50-60 degrees and is used for guiding the chips out.
The ultrasonic vibration auxiliary system comprises a first connecting piece 1 and a vibration amplitude transformer 2, wherein one end of the vibration amplitude transformer 2 is arranged in the first connecting piece 1, the other end of the vibration amplitude transformer extends out of the first connecting piece 1 and is fixedly connected with a cutter bar 7, and the vibration amplitude transformer 2 is provided with a pair of piezoelectric actuators for generating axial vibration and transmitting the vibration to a blade. Of course, the ultrasonic vibration is generated between the workpiece and the cutter, the workpiece can be clamped at the end of the vibration amplitude transformer 2, and the first connecting piece 1 is fixed on the workbench.
The structure of the vibration horn will be described in detail below.
The first connecting part 1 is provided with an inner cavity 11, and the inner cavity 11 extends along the axis of the outer ring thereof. The vibration amplitude transformer 2 is inserted in the inner cavity 11, and the axis of the vibration amplitude transformer coincides with the axis of the outer ring of the first connecting piece 1 or the inner cavity 11. The cross section of the inner cavity 11 can be circular or diagonal, in order to make the vibration horn 2 rotate randomly, the cross section of the inner cavity 11 in this embodiment is polygonal for transmitting and bearing the torsion moment, preferably, the cross section of the inner cavity 11 is regular hexagon, and the rigidity can be kept to be the maximum when the external condition is fixed.
The vibration amplitude transformer 2 is made of titanium alloy, so that the material loss in working frequency is low, the fatigue resistance is high, the acoustic impedance is low, and the vibration amplitude transformer can bear larger vibration speed and displacement amplitude. The stepped vibration amplitude transformer 2 has great stress concentration at the abrupt change position of the section, and the problem of fracture caused by fatigue is easy to occur at the position close to the abrupt change position, so that the stress concentration value can be reduced by adopting a Gaussian curve, arc and cone line transition at the abrupt change position. The tail end of the vibration amplitude transformer is in transition by 1 Gaussian curve, the diameter of the section with a smaller cross section area is 1/2 of the section with a larger diameter, the length of the section with a smaller cross section area is 2/3 of the section with a larger cross section area, the cantilever of the cutter is longer, the axial radial rigidity is relatively lower, deformation is easy to generate after stress, in order to improve the stability of the cutter in the deep hole processing process, the amplitude ratio of the axial direction and the radial direction of the ultrasonic vibration auxiliary processing system is not lower than 4:1, the cutter deviation from a preset path caused by transverse vibration is reduced, and the possibility that the cutter collides a workpiece when the cutter retracts from uncut materials is avoided; the principle that the tail end adopts 1 Gaussian curve transition is firstly to prolong the service life of the vibration amplitude transformer and enable the vibration amplitude transformer to be in an equal stress state.
As shown in fig. 3 and 4, the vibration horn 2 includes a fitting positioning section 21, a first connecting section 22, a second connecting member mounting section 23, an actuator mounting section 24, a third connecting member mounting section 25, and a blade bar connecting section 26, which are sequentially provided. The first connecting piece mounting section 22, the second connecting piece mounting section 23, the actuator mounting section 24 and the third connecting piece mounting section 25 are all cylindrical, the diameter of the second connecting piece mounting section 23 is reduced by 0.1-0.15mm compared with that of the first connecting piece mounting section 22, and the second connecting piece mounting section 23 is positioned at a vibration mode node position of the vibration amplitude transformer. The matching positioning section 21 and the cutter bar connecting section 26 are positioned at two ends of the vibration amplitude transformer 2, and the cutter bar connecting section 26 is used for connecting the cutter bars. The matching positioning section 21 is connected with the bottom of the inner cavity 11 in a matching mode, preferably, a circular groove is formed in the bottom of the inner cavity 11, a first gasket 12 is installed at the circular groove, a conical groove is formed in the outer end of the first gasket 12, the matching positioning section 21 is a cone and matched with the conical groove, the taper of the cone is 1:8, the matching positioning section 21 is inserted into the conical groove and installed in the conical groove, the matching positioning section 21 and the first gasket 12 are used for transmitting and bearing axial loads, the first gasket 12 is made of glass fibers and PET in a composite mode according to a sandwich layer structure, the middle portion of the first gasket is PET, and the inner portion and the outer portion of the first gasket.
In this embodiment, in order that the second connector 231 can transmit torque, preferably, a polyhedron connection is adopted to transmit torque, an outer ring of the cross section of the second connector 231 is a polygon matched with the inner cavity 11, and the cross section of the inner ring of the cross section of the second connector 231 and the cross section of the second connector mounting section 23 are polygons matched with each other, and the cross section is non-circular and can transmit torque. The second connector 231 is fixedly connected with the first connector 1, preferably, the section inner ring of the second connector 231 and the section of the second connector mounting section 23 are regular octagons, and the section outer ring of the second connector 231 is a regular hexagon. Further, the connection mode of the second connection member 231 and the first connection member 1 is preferably that the second connection member 231 and the first connection member 1 are provided with corresponding bolt holes so as to be fixed and pre-tightened through bolt connection, the number of the bolts is specifically three, the bolt holes of the second connection member 231 are blind holes, and a first washer 232 is mounted between the second connection member 231 and the second connection member mounting section 23. The first gasket 232 is in a regular octagon shape in cross section and is formed by compounding glass fibers and PET according to a sandwich layer structure, the PET is arranged in the middle, the glass fibers are arranged inside and outside, the high elastic modulus and the lubricating effect are achieved, and fatigue damage is not easily caused in the process that the vibration amplitude transformer is repeatedly twisted. The shaft diameter of the second connecting piece mounting section 23 is 0.1-0.2mm less than that of the first connecting section 22.
The second connecting member 231 is provided with a break-off portion, the break-off portion is provided with a second gasket 233, one end of the second gasket 233 is in contact with the first gasket 232, and the other end of the second gasket 233 is in contact with the first connecting member 1, specifically, as shown in fig. 4, the cross-sectional shape of the second gasket 233 is formed by splicing two right-angled folding blocks in opposite directions, and the splicing portion has a certain arc and an angle. This maintains a tight connection between the components while the bolt provides a compressive force toward the center. And the second gasket 233 has damping properties, and is capable of isolating vibrations of the vibration horn from the machine tool table, and likewise, preventing vibrations of the machine tool moving table from interfering with vibrations of the vibration horn.
The axial diameter of the actuator mounting section 24 is about 1/2 of the second connector mounting section 23, the piezoelectric actuator 6 is mounted on the actuator mounting section 24, the piezoelectric actuator 6 is used for realizing the axial resonance vibration of the vibration amplitude transformer, the piezoelectric actuator 6 is connected with the ultrasonic generator through an electric wire, the transmission of vibration frequency signals is transmitted through the wireless transmitter and the wireless receiver and is coded and decoded by the coding mechanism, the piezoelectric actuator 6 is specifically an ultrasonic transducer, and the ultrasonic frequency electric energy generated by the ultrasonic generator is converted into the mechanical energy of the ultrasonic vibration. Preferably, the second connector mounting section 23 and the actuator mounting section 24 form a stepped shaft, the diameters of the first connector section 22 and the actuator mounting section 24 are sequentially reduced, and the actuator mounting section 24 is provided with a pair of mounting grooves at intervals in the radial direction for mounting and matching the piezoelectric actuator 6. As shown in fig. 5, after the piezoelectric actuator 6 is installed in the installation groove, the outer ring of the piezoelectric actuator is provided with a snap spring 61 for clamping and fixing, a step is arranged on the periphery of the snap spring 61 close to the second connector installation section 23, the step is a regular hexahedron and forms a second groove capable of being matched with the second connector installation section 23 for installing the second connector 231, so that a part of the second connector 231 is installed on the step of the snap spring 61, which is equivalent to the clamping and fixing effect on the snap spring 61, so that the piezoelectric actuator 6 is more stably fixed, and the step of the snap spring 61 has a limiting effect on the second connector 231.
The third connecting piece mounting section 25 is provided with a first groove 251, a third connecting piece 2511 is mounted between the first groove 251 and the outer wall of the inner cavity 11, the third connecting piece 2511 is fixedly connected with the first connecting piece 1, the outer ring of the section of the third connecting piece 2511 is matched with the inner cavity 11, and a circular gasket is arranged between the third connecting piece 2511 and the first groove 251. The second connecting member 231, the third connecting member 2511, the first washer, the circular washer and the snap spring 61 are made of a material having a high elastic modulus, and are snap-fitted into the vibration horn 2 by deformation.
The inner circle of the cross section of the third connecting element 2511 is circular, and preferably, two first grooves 251 and two third connecting elements 2511 are correspondingly arranged and are arranged at intervals along the axis. Wherein, the vibration mode node of the vibration amplitude transformer 2 coincides with the positions of the second connecting piece 231 and the two third connecting pieces 2511. During installation, the second connecting element 231 rotates 180 ° with one of the third connecting elements 2511, and the angular difference between the two third connecting elements 2511 is 180 °, so that the dynamic unbalance mass caused by the installation of the connecting elements is mainly reduced as much as possible.
In this embodiment, the joints of the different segments all adopt the optimal circular arc transition, and the radius R of the circular arc transition3The equivalent diameter D and the length L, D of two adjacent cross sections at the joint2The length L2 and the vibration amplification factor N are determined by referring to the relationship between the optimum transition arc radius and the amplification factor N. A determination step: radius of fillet R3The size determining step is as follows:
the first step is as follows: according to
Solving the value of N;
the second step is that: according to
Solving the value A;
thirdly, checking a relation table between the optimal transition arc radius of the step-type amplitude transformer and N to obtain β values;
the fourth step is based on R3＝β·D1Finding R3A value;
wherein D1Is the equivalent diameter of the cross section of the hexagonal prism section, L1Length of hexagonal prism, D2Is the equivalent diameter of the cross section at the middle position of the transition section, L2And N is the amplification factor.
In order to achieve a good vibration effect of the shank coupling section 26 and to ensure the transmission of axial vibrations as far as possible, an extension 27 and an intermediate shaft section 28 are arranged in succession between the actuator mounting section 24 and the third connecting part mounting section 25. The central shaft section 28 has the largest diameter throughout the vibration horn for further uniform transmission of axial vibrations to the third connector mounting section 25. The lengths of the extension 27 and the intermediate shaft section 28 are specifically adjusted according to the actual requirements.
The second connecting section 29 is arranged between the third connecting piece mounting section 25 and the cutter bar connecting section 26, and the second connecting section 29 is a cylindrical amplitude-variable steel taking a Gaussian curve as the appearance, and is mainly used for achieving high vibration speed and small amplitude of axial vibration, meeting the requirements of high vibration speed and low amplitude, enabling the cylindrical amplitude-variable steel to have faster vibration speed in a certain vibration period, being used for exciting a working medium to generate higher speed, improving the processing efficiency and meeting the requirements of surface quality of a workpiece. The first coupling member 1 is coupled to a tool spindle of a machine tool to obtain feed driving of the tool.
According to the invention, the cutter consisting of the blade and the cutter bar with special structures is matched with the ultrasonic vibration system to carry out deep hole machining on the workpiece, the surface quality of the workpiece can be improved by cutting machining of the micro cutting edge, the possibility of tool chatter in the deep hole machining of the cutter is sharply reduced by ultrasonic vibration, the cutting parameters can be optimized, the cutting efficiency is improved, the surface quality of the inner side of the deep hole is better, no residual height and burr are left on the inner surface and the fillet, and the chips in the deep hole machining process are thinner under the action of the limiting contact area of the blade and the ultrasonic vibration and the micro cutting edge, so that the surface of the workpiece is not influenced. The contact area is limited to avoid overlong chips, the chip breaking function is achieved, the chips are in periodic contact and non-contact with the cutter through ultrasonic vibration, the chips are broken easily, the temperature of the cutter is reduced, the service life of the cutter is prolonged, residual height of the inner surface of the deep hole after machining is cut off under the auxiliary effect of the ultrasonic vibration, and the surface quality is improved.
The above embodiments are only for illustrating the technical solutions of the present invention and are not limited thereto, and any modification or equivalent replacement without departing from the spirit and scope of the present invention should be covered within the technical solutions of the present invention.
Claims (9)
1. A method for controlling the efficient machining of deep holes in a pump shell of an engine oil pump is characterized by comprising the following steps:
s1, calculating and obtaining a modal transfer function H of the cutting system according to a cutting system kinetic equation1(ω，n)；
S2, according to the processing depth, a row of points are uniformly and sequentially arranged from the tool nose to the tail end of the tool bar at intervals, and k points are totally marked as: 1,2,3, …, k, sequentially obtaining the modal transfer function of each node of the cutter through a modal test, and setting the modal transfer function as H3i(ω1)，i＝1，2，3，…，k；
S3, establishing a cutting processing transfer function phi under different nodes of the cutter through the modal transfer function of the cutting processing system and the modal transfer function of each node of the cutter1iWill phi1iObtaining phi through Laplace transform1i(s)；
S4, according to phi1i(s) obtaining stable areas in the cutting process of the cutter under different nodes by a method of solving the stable areas through a frequency domain;
s5, performing efficient and stable machining on the workpiece according to the cutting parameters of the stable region;
wherein in step S3, the phi1iAfter laplace transformation, the following formula is obtained:
h(s) is obtained by performing Laplace transform on the dynamic cutting depth h (t);
h0the ideal cutting depth in cutting;
t is the period of cutting, apCutting width, k2The coefficient of tangential cutting force under the ultrasonic vibration auxiliary condition is shown, n is the rotating speed, and omega is the ultrasonic vibration frequency.
2. The oil pump shell deep hole efficient machining control method according to claim 1, characterized in that: the distance between adjacent points in the step S2 is 1 mm.
3. The oil pump shell deep hole efficient machining control method according to claim 2, characterized in that: the relationship of h (t) is as follows:
h(t)＝h0-[(h2(t)-h1(t))-(h2(t-T)-h1(t-T))]；
wherein h is2(T-T) represents the depth of cut, h, of the previous tooth machining of the tool2(t) represents the depth of cut, h, of the current tooth of the tool being machined1(t) represents a depth of cut due to workpiece deflection caused by workpiece vibration, h1(T-T) represents the depth of cut due to workpiece deflection caused by workpiece vibration in the previous cycle.
4. The oil pump shell deep hole efficient machining control method according to claim 3, characterized in that: cutting force F during cutting2(t) is related to h (t) as follows:
F2(t)＝k2·h(t)·ap+ap·k3
wherein, F2(t) the following relationship can be obtained from the kinetic equation of the cutting example:
the dynamic depth of cut h (t) is subjected to laplace transform to obtain:
h(s)＝h0-(e-sT-1)(h2(s)-h1(s))
the cutting kinetics equation converts to:
wherein k is3Is the radial cutting force coefficient under the auxiliary condition of ultrasonic vibration, q2Is the displacement of the knife tip, and the knife edge,
the displacement speed of the tool nose is the speed of the tool nose,
is the displacement acceleration of the nose, k2Coefficient of tangential cutting force, M, under ultrasonic vibration assistance2Is the modal mass of the tool, n is the rotational speed, and omega is the ultrasonic vibration frequency.
5. The oil pump shell deep hole efficient machining control method according to claim 1, characterized in that: the dynamic equation of the cutting machining system in the S1 is that,
wherein M (omega, n) is a mass matrix of the cutting processing system;
k (omega, n) is a rigidity matrix of the cutting machining system;
n is the rotating speed, omega is the ultrasonic vibration frequency, D is the equivalent viscous damping matrix;
q is the displacement of the node point and,
and
respectively node velocity and node acceleration;
f (t) is a node force vector;
g and N are respectively a rotation influence coefficient and an ultrasonic vibration influence coefficient.
6. The oil pump shell deep hole efficient machining control method according to claim 1, characterized in that: in the step S1, H1(ω, n) is obtained by: firstly, establishing a finite element model of a cutting processing system, and obtaining a modal transfer function H of the finite element model under boundary conditions of different rotating speeds and ultrasonic vibration frequencies according to a cutting processing system kinetic equation1(ω1) Testing the mode transfer function H of the tool nose under the conditions of no rotation and ultrasonic vibration by experiments2(ω1) (ii) a Then using residual error epsilon minimum pair H1(ω1) And H2(ω1) Fitting to obtain a rigidity matrix K (omega, n) and a damping matrix C (omega, n) under different rotating speeds and ultrasonic vibration frequencies, fitting according to a least square method to obtain a variation function and a modal transfer function H of the rigidity matrix and the damping matrix along with the rotating speeds and the ultrasonic vibration frequencies1(ω，n)；
Wherein
ω2、ω3The minimum value and the maximum value of the cutting excitation frequency of the cutter in the cutting processing system are respectively.
7. The oil pump shell deep hole efficient machining control method according to claim 1, characterized in that: when the machining machine tool carries out deep hole machining, the rotating speed of the spindle is selected according to the peak value of the cutting depth in the stable area function on different nodes of the cutter, then the cutting depth is selected according to the rotating speed and the corresponding stable areas on different nodes, and the minimum value is selected on the cutting depth of all the nodes, so that efficient and stable machining is realized.
8. The oil pump shell deep hole efficient machining control method according to claim 1, characterized in that: the cutter includes cutter arbor (7) and fixed mounting blade (8) on cutter arbor (7), the blade both sides have the cutting edge, be provided with little cutting edge (83) on the cutting edge.
9. The oil pump shell deep hole efficient machining control method according to claim 8, characterized in that: the cutter is connected with the cutter main shaft through an ultrasonic vibration auxiliary system, the ultrasonic vibration auxiliary system comprises a first connecting piece (1) and a vibration amplitude transformer (2), one end of the vibration amplitude transformer (2) is arranged in the first connecting piece (1), one end of the vibration amplitude transformer extends out of the first connecting piece (1) to be fixedly connected with a cutter bar or a workpiece, and the vibration amplitude transformer (2) is provided with a pair of piezoelectric actuators for generating axial vibration and transmitting the vibration to the cutter blade.
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