A gear tooth surface laser shock peening path planning method

Abstract

This invention belongs to the field of laser shock peening technology, specifically a method for planning a laser shock peening path for gear tooth surfaces. The method includes the following steps: obtaining the characteristic parameters of the gear; obtaining the gear tooth surface equation based on the gear generating method; and then obtaining the coordinates of the tooth surface points and the normal vectors of the tooth surface points; converting the tooth surface point coordinates to the working coordinate system jointly determined by the robot manipulator and the laser path; obtaining the initial position and laser tilt angle of the gear tooth surface for strengthening; obtaining the correspondence between the tooth surface processing position (tooth surface arc length) and the gear center coordinates; then obtaining the angular displacement and angular velocity of the gear center in each degree of freedom direction during two adjacent impacts, i.e., the path parameters of the laser tooth surface in the tooth profile direction; calculating the laser step distance in the tooth width direction after one layer of tooth profile impact is completed based on the overlap rate, and repeating the laser shock peening in the next layer of tooth profile direction until the entire tooth surface laser shock peening is fully covered.

Description

Technical Field

[0001] This invention belongs to the field of laser shock peening processing technology, specifically a method for planning the laser shock peening path of gear tooth surface. Background Technology

[0002] Methods such as quenching, tempering, and carburizing can impart high hardness and fatigue resistance to gear surfaces, thereby extending their service life. However, these heat treatment processes often cause stress concentration and cracks on and around the gear surface. To overcome these shortcomings, shot peening and laser shock peening can create a compressive stress layer on the gear surface, improving the microstructure and preventing the propagation of microcracks. Compared to shot peening, laser shock peening generates a larger and deeper compressive stress on the surface. The impact location is controllable, eliminating the need for extensive shielding of the part. Therefore, it has broad application prospects in the field of gear surface strengthening.

[0003] Patent CN103409599A proposes a device for underwater laser shock peening of gear pump gears. This method enhances the laser shock pressure through an aqueous solution and can strengthen multiple gears in a single setup, significantly improving processing efficiency. Different scanning speeds are used for the tooth tips and tooth surfaces. However, this shock peening process for gears lacks flexibility, is complex, and has low strengthening efficiency. Furthermore, it does not address the shape characteristics of the gears, such as the tooth tips, roots, and surfaces, or the gear's characteristic parameters. This makes it difficult to effectively prevent interference between adjacent tooth tips and the laser beam path, thus failing to avoid ablation of adjacent tooth tips during the shock process and reducing the efficiency of laser shock peening.

[0004] Patent CN110438332A proposes a laser shock blasting method for the tenon groove of a small-sized turbine disk in high-temperature alloys. This method addresses the problem of poor beam reachability, achieving the advantage of beam reachability for small-sized components in aero-engines. However, it targets different laser shock blasting parameters and laser oblique incidence angles for different parts, rather than the components themselves. Even on gears, small-sized components in aerospace and shipbuilding, uneven stress distribution can occur. While this method can solve the problem of beam interference between different structural components, interference with the laser beam path still exists when multiple components or adjacent tooth tips are involved. Therefore, a laser shock blasting path planning method for gear tooth surfaces is urgently needed. Summary of the Invention

[0005] The purpose of this invention is to provide a method for planning the laser shock blasting strengthening path of gear teeth, which is designed for harsh working environments such as aviation, aerospace, and shipbuilding. It aims to solve the problems of increasing the fatigue life and improving the wear resistance of gears, and to address the technical problems existing in the current laser shock blasting strengthening methods.

[0006] The technical solution adopted by this invention to achieve the above objectives is: a method for planning the laser shock blasting strengthening path of gear tooth surfaces, comprising the following steps:

[0007] Step 1): Obtain the characteristic parameters of the gear, obtain the gear tooth surface equation according to the gear generating method of rack machining, and obtain the coordinates of the tooth surface points and the tooth surface point normal vectors according to the gear tooth surface equation.

[0008] Step 2): Transform the coordinates of the tooth surface points on the tooth surface to the working coordinate system jointly determined by the robot manipulator and the laser path;

[0009] Step 3): Calculate the initial position and laser tilt angle of the gear tooth surface strengthening process under the condition of the reserved clearance between adjacent tooth tips; to ensure that the phenomenon of adjacent tooth tips intruding does not occur within the laser path range;

[0010] Step 4): Based on the minimum tilt angle of the laser impact tooth surface at the initial position, obtain the initial values ​​of the current gear center position and gear rotation angle in the working coordinate system; and based on the principle of equal laser tilt angle, obtain the correspondence between the tooth surface machining position and the gear center coordinates for the tooth surface arc length.

[0011] Step 5): Based on the process parameters that affect the laser overlap rate, and by using the principle of equal arc length of the tooth profile, obtain the angular displacement and angular velocity of the gear center in each degree of freedom during two adjacent impacts, thus obtaining the path parameters of the laser-strengthened tooth surface in the tooth profile direction.

[0012] Step 6): After the first layer of tooth profile impact is completed based on the overlap rate, calculate the laser step distance in the tooth width direction, and repeat steps 4) to 5) to perform laser impact strengthening in the next layer of tooth profile direction until the entire tooth surface is fully covered by laser impact strengthening.

[0013] The characteristic parameters of the gear include: module, number of teeth, addendum, clearance, and displacement coefficient.

[0014] The gear tooth surface equation is obtained by using the gear generating method based on rack machining, specifically as follows:

[0015] 1-1) Define the position state where the rack tooth surface and the gear tooth tip are tangent at point A as the machining start state, and establish x along the pitch line. t The axis, the center line of the rack tooth groove is y t The axis is defined as the coordinate system S of the rack. t Then in S t In the coordinate system, the position of point A is:

[0016]

[0017] Where z is the number of teeth, α a The tooth tip pressure angle, r b Let α be the radius of the base circle. t The tooth profile angle of the rack is given by the origin O of the rack blank coordinate system. g With respect to the origin O of the machine tool coordinate system m coincide;

[0018] 1-2) Initial moment, the tool center O t In machine tool coordinate system S m Middle edge y m Direction and position y t0 for:

[0019] y t0 =r+χm

[0020] Where r is the pitch circle radius, χ is the gear displacement coefficient, and m is the gear module;

[0021] 1-3) Center O of the blade tip arc tip To S t The distance from the origin is expressed as:

[0022]

[0023] Where, r t h is the radius of the rack cutter tip arc. a * is the tooth tip height coefficient, and c is the clearance coefficient;

[0024] 1-4) Because the rack and gear roll tangentially at the pitch circle, the translational displacement Δx of the rack... t Angle with the gear blank Relationship, that is:

[0025]

[0026] 1-5) Based on the kinematic relationship of the gears, the tool coordinate S t To machine tool coordinate S m The transformation matrix is:

[0027]

[0028] Where, x t0 Let S be the tool coordinates at the initial moment. t Origin t In machine tool coordinate system S m x in m Directional position value;

[0029] 1-6) Machine tool coordinate S m To gear blank coordinate S g Transformation matrix:

[0030]

[0031] The pressure angle α at any point i on the tooth profile of the gear i With meshing pressure angle The relationship is as follows:

[0032]

[0033] Where, θ b The tooth base half angle is equal to half the central angle from the point where the extension of the involute intersects the base circle to the center line of the tooth.

[0034] 1-7) In coordinate system S t In the diagram, the tooth profile coordinates of the straight cutting edge of the rack are:

[0035]

[0036] Where s is the distance from any point on the straight edge of the tool to the starting point A;

[0037] Based on tool coordinates S t To machine tool coordinate S m Transformation matrix, machine tool coordinates S m To gear blank coordinate S g Using the transformation matrix and the tooth profile coordinates of the straight cutting edge of the rack, the tooth surface equation is obtained as follows:

[0038] r ga =M gm M mt r ta .

[0039] The coordinates of the points on the tooth surface and the normal vector of the points on the tooth surface are obtained based on the tooth surface equation of the gear, specifically:

[0040] 2-1) In the tool coordinate system S t The normal vector of the rack tooth profile is expressed as:

[0041]

[0042] Where, r ta The tooth profile coordinates of the straight cutting edge of the rack, where s is the distance from any point on the straight cutting edge of the tool to the starting point A;

[0043] 2-2) In the machine tool coordinate system S m Inside, the spatial position of the rack tooth profile and its normal vector are as follows:

[0044]

[0045] Among them, L mt For Mmt The first three submatrices, r ma n represents the spatial position of the rack tooth profile in the machine tool coordinate system. ma The normal vector of the rack tooth profile in the machine tool coordinate system;

[0046] 2-3) In the machine tool coordinate system S m Inside, the relative speed between the gear and the rack is:

[0047]

[0048] 2-4) The relative velocity between the gear blank and the gear rack is perpendicular to the normal direction at the cutting point, and the following equation is satisfied at the cutting point:

[0049]

[0050] The above equation includes the unknown variable s and Δx. t Given any value of s, the corresponding Δx can be obtained using the above formula. t value;

[0051] 2-5) Due to displacement, when the end point T of the straight cutting edge of the rack is inside the base circle of the gear, the effective length of the straight cutting edge of the machined gear is less than the actual length of the straight cutting edge of the rack. Therefore, the maximum value of s is expressed as:

[0052]

[0053] 2-6) s and Δx t Substitute the equations into the tooth surface equations to solve for the coordinates of the gear tooth surface.

[0054] The initial position and laser tilt angle of the gear for gear tooth surface strengthening are obtained as follows:

[0055] The laser tilt angle λ reaches its minimum value at the boundary of the tooth surface near the root. Based on this minimum tilt angle value, the tooth surface is impacted at an equal tilt angle to ensure that the tip of the adjacent tooth does not enter the range of the laser beam.

[0056] At the initial laser impact position, a laser with a spot radius of r impacts point C at the root of the tooth surface at an angle of λ. The vertical safety distance δ between the tip T of the adjacent tooth and the straight line of the optical path is then used to determine the position x of the gear center in the working coordinate system. g0 y g0 and the initial rotation angle θ of the gear g0 Its equation is:

[0057]

[0058] Where, r b Let α be the base circle of the gear. C as well as These are the pressure angle at the root of the tooth surface and the meshing pressure angle, α. a as well as These are the pressure angle at the tooth tip and the meshing pressure angle, respectively. a Let z be the radius of the addendum circle, and z be the number of teeth on the gear.

[0059] The position x of the gear center in the working coordinate system g0 y g0 and the initial rotation angle θ of the gear g0 Given the initial position of the gear, laser shock peening begins. To ensure consistent impact intensity along the tooth surface during the shock process, the initial laser tilt angle is:

[0060]

[0061] Step 4) specifically includes:

[0062] To maintain a constant laser tilt angle, gears are needed at the x-axis. g y g and θ g When the gears move in a coordinated manner in different directions, the displacements of the gears in each direction satisfy the following relationship:

[0063]

[0064] Where, α i as well as Let r be the pressure angle and meshing pressure angle at any point i on the tooth surface. i x is the distance from the point to the center of the gear. gi y gi and θ gi The displacement and rotation angle of the gear center relative to the working coordinate system when laser impacts point i on the tooth surface.

[0065] The process parameters affecting the laser overlap rate include: laser overlap rate, spot diameter, laser repetition frequency, and gear running speed v. xg v yg and v θg .

[0066] Step 5) specifically includes:

[0067] For a circular light spot with radius r, to satisfy the overlap ratio L, it is necessary to use a gear running at a speed v within a time range of 1 / f. xg v yg and v θg The linkage causes a point on the tooth surface at a distance Δs from the current position to move to the laser impact point, where Δs satisfies the following equation:

[0068]

[0069] To obtain the angular displacement and angular velocity of the gear center in each degree of freedom during two consecutive impacts, the velocity of the robot manipulator during this impact is:

[0070]

[0071] Where, x g1 y g1 and θ g1 x represents the current center position and rotation angle of the impact gear. g2 y g2 and θ g2 The gear displacement and rotation angle values ​​for the next impact are obtained from the determined Δs value using the principle of equal arc length of the tooth profile;

[0072] The final obtained v xg v yg and v θg The path parameters of the laser-shock-reinforced tooth surface in the tooth profile direction are obtained.

[0073] Step 6) specifically includes:

[0074] Based on the obtained gear running speed v xg v yg and v θg The laser impact path along the tooth profile direction is planned. Since the tooth width direction and the tooth profile direction are completely decoupled, after impacting one layer of tooth profile, it is only necessary to offset by a certain distance in the tooth width direction to ensure the overlap rate, and then the impact of the next layer of tooth profile can be repeated until the strengthening process of the entire tooth surface is completed.

[0075] The present invention has the following beneficial effects and advantages:

[0076] This invention proposes a laser shock peening (LSP) method for machining gear teeth that considers the actual tooth surface morphology. By introducing a tooth surface equation into the LSP process, a more accurate LSP trajectory can be obtained. The movement of a six-DOF manipulator results in a more uniform compressive stress distribution on the machined gear teeth, leading to higher processing efficiency. Accurate gear spatial relationships effectively prevent interference between adjacent tooth tips and the laser beam path, avoiding ablation of adjacent tooth tips during the impact process and eliminating the time wasted on protecting adjacent tooth tips. Attached Figure Description

[0077] Figure 1 This is a flowchart of the laser shock enhancement trajectory planning scheme of the present invention.

[0078] Figure 2 This is a schematic diagram illustrating the derivation principle of the gear tooth surface coordinates of this invention.

[0079] Figure 3 This is a schematic diagram of the laser shock strengthening device of the present invention.

[0080] Figure 4 This is a diagram showing the relative position of the constant inclination angle reinforced gear to the laser in this invention.

[0081] Figure 5a This is a graph showing the variation of the gear's x-direction displacement parameters relative to the tooth profile arc length.

[0082] Figure 5b This is a graph showing the variation of the gear's y-direction displacement parameter relative to the tooth profile arc length.

[0083] Figure 5c This is a graph showing the change of the gear directional displacement parameter relative to the tooth profile arc length in this invention.

[0084] Figure 5d This is the present invention. Figures 5a-5c A diagram showing the change in tooth profile arc length corresponding to the displacement.

[0085] Figure 6 This is a schematic diagram of the impact path on the tooth surface of the present invention. Detailed Implementation

[0086] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0087] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings and examples, but the present invention should not be limited to these embodiments. Other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are all within the scope of protection of the present invention.

[0088] A method for planning laser shock blasting strengthening paths for gears based on gear tooth surface coordinates is proposed. This method derives the normal direction of the tooth surface points based on the gear tooth surface equation, considers the occlusion state of adjacent teeth, establishes the correspondence between the laser direction and the tooth surface normal through coordinate transformation, and forms the laser shock blasting strengthening path through a six-degree-of-freedom robot programming.

[0089] The device mainly includes: gears, gear clamps, a six-degree-of-freedom manipulator, and a laser generator. The gears are fixed to the manipulator flange via the gear clamps, and the laser output port position is fixed. The manipulator changes the spatial position of the gears through its six-axis linkage to form a laser-enhanced impact path.

[0090] like Figure 1 The diagram shown is a flowchart of the laser shock strengthening trajectory planning scheme of the present invention. The present invention provides a method for laser shock strengthening path planning of gear tooth surfaces, which includes the following steps:

[0091] Step 1): Obtain the characteristic parameters of the gear, obtain the gear tooth surface equation according to the gear generating method of rack machining, and obtain the coordinates of the tooth surface points and the tooth surface point normal vectors according to the gear tooth surface equation.

[0092] The characteristic parameters of a gear include: module, number of teeth, addendum, clearance, and displacement coefficient.

[0093] Step 2): Transform the coordinates of the tooth surface points on the tooth surface to the working coordinate system jointly determined by the robot manipulator and the laser path;

[0094] Step 3): Calculate the initial position and laser tilt angle of the gear tooth surface strengthening process under the condition of the reserved clearance between adjacent tooth tips; to ensure that the phenomenon of adjacent tooth tips intruding does not occur within the laser path range;

[0095] Step 4): Based on the minimum tilt angle of the laser impact tooth surface at the initial position, obtain the initial values ​​of the current gear center position and gear rotation angle in the working coordinate system; and based on the principle of equal laser tilt angle, obtain the correspondence between the tooth surface machining position and the gear center coordinates for the tooth surface arc length.

[0096] Step 5): Based on the process parameters that affect the laser overlap rate, and by using the principle of equal arc length of the tooth profile, obtain the angular displacement and angular velocity of the gear center in each degree of freedom during two adjacent impacts, thus obtaining the path parameters of the laser-strengthened tooth surface in the tooth profile direction.

[0097] Step 6): After the first layer of tooth profile impact is completed based on the overlap rate, calculate the laser step distance in the tooth width direction, and repeat steps 4) to 5) to perform laser impact strengthening in the next layer of tooth profile direction until the entire tooth surface is fully covered by laser impact strengthening.

[0098] In this embodiment, the gear being processed is made of 45# steel, with a gear module of 2, 20 teeth, and a displacement coefficient of 0.01.

[0099] like Figures 1-3 As shown in the figure, in the laser shock peening method for machining gear tooth surfaces designed in this embodiment, step 1, obtaining the coordinates of the tooth surface points and the normal vector of the tooth surface points, is specifically as follows:

[0100] like Figure 2 As shown, this is a scheme for machining gear tooth profiles using a rack and pinion method via the generating method. The position state where the rack tooth surface and the gear tooth tip are tangent at point A is defined as the machining start state. An x-axis is established along the pitch line. t The axis, the center line of the rack tooth groove is y t The axis is defined as the coordinate system S of the rack. t Then in S t Within the coordinate system, the position of point A can be described as follows:

[0101]

[0102] Where z is the number of teeth, α a The tooth tip pressure angle, r b Let α be the radius of the base circle. t The tooth profile angle of the rack is given by the origin O of the rack blank coordinate system. g With respect to the origin O of the machine tool coordinate system m Coincidence. Initially, the tool center O... t In machine tool coordinate system S m Middle edge y m The direction and position are:

[0103] y t0 =r+χm

[0104] Where r is the pitch circle radius, χ is the gear modification coefficient, and m is the gear module. The center of the tool tip arc O... tip To S t The distance from the origin can be expressed as:

[0105]

[0106] Where, r t h is the radius of the rack cutter tip arc. a * is the tooth tip height coefficient, and c is the clearance coefficient.

[0107] Because the rack and gear roll tangentially at the pitch circle, the translational displacement Δx of the rack... t Angle with the gear blank The following relationship exists:

[0108]

[0109] Based on the kinematic relationship of the gears, the tool coordinate S t To machine tool coordinate S m Transformation matrix:

[0110]

[0111] In the formula x t0 Let S be the tool coordinates at the initial moment. t Origin t In machine tool coordinate system S m x in m The direction and position value is expressed as follows:

[0112] x t0 =-x A +(y A +χm)cotα t

[0113] Machine coordinate S m To gear blank coordinate S g Transformation matrix:

[0114]

[0115] The pressure angle α at any point i on the tooth profile of the gear i With meshing pressure angle The relationship is as follows:

[0116]

[0117] In the formula θ b The central angle from the point where the extension of the involute curve intersects the base circle to the center line of the gear tooth is called the tooth base half angle.

[0118]

[0119] In the formula, inv is the involute function.

[0120] In coordinate system S t In this context, the tooth profile coordinates of the straight cutting edge of the rack are defined as follows:

[0121]

[0122] Where s is the distance from any point on the straight edge of the tool to the starting point A, such as Figure 2 As shown. Then in coordinate system S t Inside, the normal vector of the rack tooth profile can be expressed as:

[0123]

[0124] In machine tool coordinate system S m Inside, the spatial position of the rack tooth profile and its normal vector are as follows:

[0125]

[0126] Among them, L mt For M mt The first three submatrices.

[0127] In machine tool coordinate system S m Inside, the relative speed between the gear and the rack is:

[0128]

[0129] The relative velocity between the gear blank and the gear rack should be perpendicular to the normal direction at the cutting point. Therefore, the following equation is satisfied at the cutting point:

[0130]

[0131] The above equation includes the unknown variable s and Δx. t Given any value of s, then the corresponding Δx t The value can be solved using the above formula. Due to the influence of displacement, the end point T of the straight cutting edge of the rack may be inside the base circle of the gear. In this case, the effective length of the straight cutting edge of the machined gear is less than the actual length of the straight cutting edge of the rack. Therefore, the maximum value of s can be expressed as:

[0132]

[0133] s and Δx t Substitute into the tooth surface equation:

[0134] r ga =M gm M mt r ta

[0135] The coordinates of the gear tooth surface can then be solved.

[0136] Steps 2 and 3 are as follows:

[0137] First, in step 2, the coordinates of the tooth surface points need to be transformed to the working coordinate system jointly determined by the robot manipulator and the laser path; the working coordinate system S w Set at the laser focal point;

[0138] like Figure 3 The diagram shown is a schematic of the laser shock peening device of the present invention. The tooth surface equation obtained through step 1 is r. ga It is worth noting that r at this point... ga Given two-dimensional coordinates, and since the dimensional changes in the z-direction of the spur gear tooth surface equation are decoupled from those in the (x,y) direction, our analysis below only considers the (x,y) dimension. Let r... ga In S w Representation in a coordinate system. Several variables need to be added, namely θ in the gear coordinate system. g and the position x of the gear center in the working coordinate system. g y g To ensure a uniform distribution of residual compressive stress on the tooth surface, the angle λ between the laser direction and the tooth surface normal must remain constant. Simultaneously, to avoid interference from adjacent tooth tips, the optical path must avoid adjacent tooth tips. It is easy to observe that the laser tilt angle λ reaches its minimum value at the boundary near the root of the tooth surface. Using this minimum tilt angle as a basis for impacting the tooth surface at a constant tilt angle ensures that adjacent tooth tips do not enter the laser beam range. The minimum laser tilt angle is derived below. It is worth noting that due to the constant characteristic of the laser tilt angle, and the requirement that the normal of the involute be tangent to the base circle, the angle between the laser optical path direction and the tangent of the gear's base circle is also fixed. Without loss of generality, let's set it as follows... Figure 3The position shown is the initial position of the laser impact. At this time, the laser with a spot radius of r impacts point C at the root of the tooth surface at an angle of λ. The vertical safety distance δ between the tip T of the adjacent tooth and the straight line of the optical path is used to determine the position x of the gear center in the working coordinate system. g0 y g0 and the initial rotation angle θ of the gear g0 Its equation is:

[0139]

[0140] Where, r b Let α be the base circle of the gear. C as well as These are the pressure angle at the root of the tooth surface and the meshing pressure angle, α. a as well as These are the pressure angle at the tooth tip and the meshing pressure angle, respectively. a Let x be the addendum circle radius, and z be the number of teeth on the gear. g0 y g0 and θ g0 The determined gear position is the initial position from which laser shock peening begins, such as... Figure 3 As shown. To ensure consistent impact strength along the tooth surface during the impact process, this invention selects a constant tilt angle machining method. The initial laser tilt angle can be expressed as:

[0141]

[0142] Step 4: To ensure consistent laser tilt angle during the laser shock process, tooth surface strengthening is performed based on the laser tilt angle obtained in Step 3. To maintain a constant laser tilt angle, the gear needs to be in the x... g y g and θ g When the gears move in a coordinated manner in different directions, the displacements of the gears in each direction satisfy the following relationship:

[0143]

[0144] Where, α i as well as Let r be the pressure angle and meshing pressure angle at any point i on the tooth surface. i x is the distance from the point to the center of the gear. gi y gi and θ gi Let be the displacement of the gear center relative to the working coordinate system when laser impacts point i on the tooth surface. Under the working conditions of a laser spot diameter of 0.4 mm and an obstacle avoidance distance δ = 0.1 mm, the position of the gear relative to the laser beam during laser impact is as follows: Figure 4As shown in the figure, for fixed laser tilt angle machining, the δ value reaches its minimum at the root of the impact tooth surface, and gradually increases as the impact position moves upward on the tooth surface. The variation law of gear displacement in various directions is as follows: Figures 5a-5d As shown, from Figures 5a-5c As can be seen from this, as the arc length increases, x g y g and θ g All of them exhibit a trend of initial high speed followed by a slowdown. For example... Figure 5d As shown, the gear center trajectory exhibits a linear pattern. To ensure the overlap rate L of the light spots, it is necessary to control the speed of the gear's rotation.

[0145] Step 5: The main process parameters affecting the beam overlap rate are beam radius r, laser repetition frequency f, and gear running speed v. xg v yg and v θg According to the definition of beam overlap ratio, for a circular beam with radius r, in order to satisfy the overlap ratio L, it is necessary to pass through v within a time range of 1 / f. xg v yg and v θg The linkage causes a point on the tooth surface at a distance Δs from the current position to move to the laser impact point, where Δs satisfies the following equation:

[0146]

[0147] Without loss of generality, assume the current center position of the impact gear is x. g1 y g1 and θ g1 Once the value of Δs is determined, the arc length-displacement diagram obtained in step 4 is shown below. Figures 5a-5d As shown, the gear displacement x at the next impact can be queried. g2 y g2 and θ g2 Subtracting the coordinates of the two positions and dividing by the laser repetition period gives the speed at which the robot manipulator moved during this impact.

[0148]

[0149] Step 6: At this point, the laser impact path planning along the tooth profile direction is complete. Since the tooth width direction and the tooth profile direction are completely decoupled, after impacting one layer of the tooth profile, it is only necessary to offset a certain distance in the tooth width direction to ensure the overlap rate, and then repeat the impact of the next layer of the tooth profile until the entire tooth surface strengthening process is completed. Figure 6 As shown.

[0150] With a laser repetition frequency of 1Hz, an overlap rate of 50%, and a laser spot radius of 1mm as experimental conditions, the experiment verified that the residual compressive stress on the tooth surface after impact remains consistent due to the constant laser tilt angle. This avoids the uncontrollable process effect caused by uneven distribution of residual compressive stress. At the same time, the strengthening process uses the minimum laser tilt angle that does not interfere with the impact process of adjacent tooth tips to strengthen the tooth surface, ensuring the highest efficiency of laser impact gears.

[0151] The above description is merely an embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, extensions, etc., made within the spirit and principles of the present invention are included within the scope of protection of the present invention.

Claims

1. A method for planning the laser shock blasting path for strengthening gear tooth surfaces, characterized in that, Includes the following steps: Step 1): Obtain the characteristic parameters of the gear, obtain the gear tooth surface equation according to the gear generating method of rack machining, and obtain the coordinates of the tooth surface points and the tooth surface point normal vectors according to the gear tooth surface equation. Step 2): Transform the coordinates of the tooth surface points on the tooth surface to the working coordinate system jointly determined by the robot manipulator and the laser path; Step 3): Calculate the initial position and laser tilt angle of the gear tooth surface strengthening process under the condition of the reserved clearance between adjacent tooth tips; To ensure that no adjacent tooth tips intrude within the laser path range; The initial position and laser tilt angle of the gear for gear tooth surface strengthening are obtained as follows: The laser tilt angle λ reaches its minimum value at the boundary of the tooth surface near the root. Based on this minimum tilt angle value, the tooth surface is impacted at an equal tilt angle to ensure that the tip of the adjacent tooth does not enter the range of the laser beam. At the initial laser impact position, a laser with a spot radius of r impacts point C at the root of the tooth surface at an angle of λ. The vertical safety distance δ between the tip T of the adjacent tooth and the straight line of the optical path is determined. Therefore, the position x of the gear center in the working coordinate system is determined based on point C at the root of the tooth surface and point T of the adjacent tooth. g0 y g0 and the initial rotation angle θ of the gear g0 Its equation is: ； Where, r b Let α be the base circle of the gear. C and φ C These are the pressure angle at the root of the tooth surface and the meshing pressure angle, α. a and φ a These are the pressure angle at the tooth tip and the meshing pressure angle, respectively. a Let z be the radius of the addendum circle, and z be the number of teeth on the gear. The position x of the gear center in the working coordinate system g0 y g0 and the initial rotation angle θ of the gear g0 Given the initial position of the gear, laser shock peening begins. To ensure consistent impact intensity along the tooth surface during the shock process, the initial laser tilt angle is: ; Step 4): Based on the minimum tilt angle of the laser impact tooth surface at the initial position, obtain the initial values ​​of the current gear center position and gear rotation angle in the working coordinate system; and based on the principle of equal laser tilt angle, obtain the correspondence between the tooth surface machining position and the gear center coordinates in terms of the tooth surface arc length. Step 5): Based on the process parameters that affect the laser overlap rate, and by using the principle of equal arc length of the tooth profile, obtain the angular displacement and angular velocity of the gear center in each degree of freedom during two adjacent impacts, thus obtaining the path parameters of the laser-strengthened tooth surface in the tooth profile direction. Step 6): Calculate the laser step distance in the tooth width direction after the first layer of tooth profile impact is completed based on the overlap rate. Repeat steps 4) to 5) to perform laser impact strengthening in the next layer of tooth profile direction until the entire tooth surface is fully covered by laser impact strengthening.

2. The method for planning a laser shock blasting strengthening path for gear tooth surfaces according to claim 1, characterized in that, The characteristic parameters of the gear include: module, number of teeth, addendum, clearance, and displacement coefficient.

3. The method for planning a laser shock blasting strengthening path for gear tooth surfaces according to claim 1, characterized in that, The gear tooth surface equation is obtained by using the gear generating method based on rack machining, specifically as follows: 1-1) Define the position state where the rack tooth surface and the gear tooth tip are tangent at point A as the machining start state, and establish x along the pitch line. t The axis, the center line of the rack tooth groove is y t The axis is defined as the coordinate system S of the rack. t Then in S t Within the coordinate system, the position of point A is: ； Where z is the number of teeth, α a r is the tooth tip pressure angle. b Let α be the radius of the base circle. t The tooth profile angle of the rack is given by the origin O of the rack blank coordinate system. g With respect to the origin O of the machine tool coordinate system m coincide; 1-2) Initial moment, the tool center O t In machine tool coordinate system S m Middle edge y m Direction and position for: ； Where r is the pitch circle radius, χ is the gear displacement coefficient, and m is the gear module; 1-3) Center O of the blade tip arc tip To S t The distance from the origin is expressed as: ； Where, r t h is the radius of the rack cutter tip arc. a * is the tooth tip height coefficient, and c is the clearance coefficient; 1-4) Because the rack and gear roll tangentially at the pitch circle, the translational displacement Δx of the rack... t Angle Δφ with the gear blank g Relationship, that is: ； 1-5) Based on the kinematic relationship of the gears, the tool coordinate S t To machine tool coordinate S m The transformation matrix is: ； Where, x t0 Let S be the tool coordinates at the initial moment. t Origin t In machine tool coordinate system S m x in m Directional position value; 1-6) Machine tool coordinate S m To gear blank coordinate S g Transformation matrix: ； The pressure angle α at any point i on the tooth profile of the gear i With meshing pressure angle φ i The relationship is as follows: ； Where, θ b The tooth base half angle is equal to half the central angle from the point where the extension of the involute intersects the base circle to the center line of the tooth. 1-7) In coordinate system S t In the diagram, the tooth profile coordinates of the straight cutting edge of the rack are: ； Where s is the distance from any point on the straight edge of the tool to the starting point A; Based on tool coordinate S t To machine tool coordinate S m Transformation matrix, machine tool coordinates S m To gear blank coordinate S g Using the transformation matrix and the tooth profile coordinates of the straight cutting edge of the rack, the tooth surface equation is obtained as follows: 。 4. The method for planning a laser shock blasting strengthening path for gear tooth surfaces according to claim 3, characterized in that, The coordinates of the points on the tooth surface and the normal vector of the points on the tooth surface are obtained based on the tooth surface equation of the gear, specifically: 2-1) In the tool coordinate system S t The normal vector of the rack tooth profile is expressed as: ； in, The tooth profile coordinates of the straight cutting edge of the rack, where s is the distance from any point on the straight cutting edge of the tool to the starting point A; 2-2) In the machine tool coordinate system S m Inside, the spatial position of the rack tooth profile and its normal vector are as follows: ； Among them, L mt For M mt The first three submatrices, This represents the spatial position of the rack tooth profile in the machine tool coordinate system. The normal vector of the rack tooth profile in the machine tool coordinate system; 2-3) In the machine tool coordinate system S m Inside, the relative speed between the gear and the rack is: ； 2-4) The relative velocity between the gear blank and the gear rack is perpendicular to the normal direction at the cutting point, and the following equation is satisfied at the cutting point: ； The above equation includes the unknown variable s and Δx. t Given any value of s, the corresponding Δx can be obtained using the above formula. t value; 2-5) Due to the influence of displacement, when the end point T of the straight cutting edge of the rack is inside the base circle of the gear, the effective length of the straight cutting edge of the machined gear is less than the actual length of the straight cutting edge of the rack. Therefore, the maximum value of s is expressed as: ； 2-6) s and Δx t Substitute the equations into the tooth surface equations to solve for the coordinates of the gear tooth surface.

5. The method for planning a laser shock blasting strengthening path for gear tooth surfaces according to claim 1, characterized in that, Step 4) specifically involves: To maintain a constant laser tilt angle, gears are needed at x g y g and θ g When the gears move in a coordinated manner in different directions, the displacements of the gears in each direction satisfy the following relationship: ； Where, α i and φ i Let r be the pressure angle and meshing pressure angle at any point i on the tooth surface. i x is the distance from the point to the center of the gear. gi y gi and θ gi The displacement and rotation angle of the gear center relative to the working coordinate system when laser impacts point i on the tooth surface.

6. The method for planning a laser shock blasting strengthening path for gear tooth surfaces according to claim 1, characterized in that, The process parameters affecting the laser overlap rate include: laser overlap rate, spot diameter, laser repetition frequency, and gear running speed v. xg v yg and v θg .

7. The method for planning a laser shock blasting strengthening path for gear tooth surfaces according to claim 1, characterized in that, Step 5) specifically involves: For a circular light spot with radius r, to satisfy the overlap ratio L, it is necessary to use a gear running at a speed v within a time range of 1 / f. xg v yg and v θg The linkage causes a point on the tooth surface at a distance Δs from the current position to move to the laser impact point, where Δs satisfies the following equation: ； To obtain the angular displacement and angular velocity of the gear center in each degree of freedom during two consecutive impacts, the velocity of the robot manipulator during this impact is: ； Where, x g1 y g1 and θ g1 x represents the current center position and rotation angle of the impact gear. g2 y g2 and θ g2 The gear displacement and rotation angle values ​​for the next impact are obtained from the determined Δs value using the principle of equal arc length of the tooth profile; The final obtained v xg v yg and v θg The path parameters of the laser-shock-reinforced tooth surface in the tooth profile direction are obtained.

8. The method for planning a laser shock blasting strengthening path for gear tooth surfaces according to claim 1, characterized in that, Step 6) specifically involves: Based on the obtained gear running speed v xg v yg and v θg The laser impact path along the tooth profile direction is planned. Since the tooth width direction and the tooth profile direction are completely decoupled, after impacting one layer of tooth profile, it is only necessary to offset by a certain distance in the tooth width direction to ensure the overlap rate, and then the impact of the next layer of tooth profile can be repeated until the strengthening process of the entire tooth surface is completed.

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