Pressure compensation method of floating grinding tool for grinding inner spherical surface of ball seat of spherical hinge

Abstract

The invention relates to a ball hinge inner spherical surface grinding floating grinding tool acting force compensation method which comprises the steps that a ball seat is set to rotate around a self rotating shaft Z, under the action of friction torque, a floating grinding tool rotates around a self rotating shaft Z ', and the ball seat rotating shaft Z does not coincide with a grinding tool rotating shaft Z'; the method includes: 1, determining an included angle phi between a normal direction of each grinding point of a spherical surface and a grinding tool rotating shaft; 2, establishing a pressure compensation mathematical model according to the included angle phi between the normal direction of the spherical grinding point and the rotating shaft of the grinding tool, namely calculating the positive pressure q borne by the inner spherical surface of the ball seat by using the pressure N applied to the floating grinding tool; calculating the rotating torque of the grinding tool by utilizing friction force generated by the surface of the grinding tool and the inner spherical surface of the ball seat; setting the contact between a grinding tool pressure piece and a grinding tool as plane contact in spherical grinding, and calculating the frictional resistance moment between the pressure piece and the grinding tool; in the actual grinding action, the pressure input to the grinding tool is adjusted in real time according to the established pressure compensation mathematical model, pressure compensation is achieved, and the grinding effect and efficiency are ensured.

Description

Technical Field

[0001] The invention belongs to the technical field of ball joint grinding, and in particular relates to a method for compensating pressure of a floating grinding tool for grinding a spherical surface inside a ball seat of a ball joint. Background Art

[0002] The spherical surface is an important workpiece profile surface. The ball hinge, as a spherical motion mechanism, consists of three parts: a ball seat, a ball journal, and a ball pressure cover. The ball journal can rotate freely within a certain range without sticking or movement, and the spherical contact is 60%-80%. The existing processing technology is pure manual scraping by workers, and the operator's skill level is required to be high, the production efficiency is low, and it cannot meet the needs of mass production. The development of automatic grinding technology is to solve the shortcomings of the current technology. The high-speed grinding of the spherical surface is mainly carried out on a high-speed spherical grinding machine. The ball seat is installed on the main shaft of the grinder, and a layer of abrasive is applied on the surface of the abrasive tool. The abrasive tool is installed at the pressure piece of the grinding tool installation position of the grinder. The pressure piece applies pressure to the abrasive tool to apply grinding pressure to the spherical surface inside the ball seat, and allows the abrasive tool to rotate around its own rotation center. At the same time, the grinding ball head of the abrasive tool is driven to approach the center of the ball seat and swing around the center O of the spherical surface of the ball seat.

[0003] During the grinding process, the ball seat makes an active rotation motion on the spindle, and the grinding tool makes a follow-up rotation motion in the inner spherical surface above the ball seat. As the grinding amount is removed, the parameters change, the existing grinding effect is not good, and the grinding efficiency is not high. In order to change this situation, it is necessary to study and analyze the force between the grinding tool and the ball seat during the spherical surface grinding process, and eliminate the method of compensating the force error after the parameters change as the grinding amount is removed during the grinding process. Achieve high-speed grinding of the spherical surface to meet technical requirements and improve production efficiency. Summary of the invention

[0004] Aiming at the deficiencies of the prior art, the present invention provides a method for compensating pressure of a floating grinding tool for grinding the inner spherical surface of a ball seat of a ball hinge.

[0005] The above-mentioned object of the present invention is achieved by the following technical solutions:

[0006] A method for compensating the force of a floating abrasive tool for grinding the inner spherical surface of a ball hinge, wherein the ball seat is set to rotate around its own rotation axis Z, and under the action of the friction torque, the floating abrasive tool rotates around its own axis Z′, and the ball seat rotation axis Z does not coincide with the abrasive tool rotation axis Z′; the method comprises the following steps:

[0007] Step 1, confirm the angle φ between the normal direction of each grinding point on the spherical surface and the rotation axis of the grinding tool;

[0008] Step 2: According to the angle φ between the normal direction of the spherical grinding point and the abrasive tool axis, a pressure compensation mathematical model is established, including:

[0009] 2.1. Using the pressure N applied to the floating mold, calculate the positive pressure q on the spherical surface in the ball seat;

[0010] 2.2. Use the friction force between the surface of the mold and the spherical surface inside the ball seat to calculate the rotational torque of the mold;

[0011] 2.3. In spherical grinding, the contact between the pressure piece and the mold is set to be plane contact, and the friction resistance torque between the pressure piece and the mold is calculated.

[0012] Step 3: In actual grinding, the pressure input to the grinding tool is adjusted from time to time according to the established pressure compensation mathematical model to achieve pressure compensation.

[0013] Moreover, in step 1, the method for obtaining the φ angle is: using a high-precision three-coordinate measuring instrument to measure the ball seat and evenly collect three-standard data of a large number of discrete points; the three-coordinate data are processed by reverse engineering software to construct an accurate mathematical model of the spherical surface after research, and then through the Ansys software algorithm, the normal direction and pressure distribution of each point on the spherical surface can be obtained, and the software directly obtains the size and angle of the resultant force.

[0014] Moreover, in step 2.1, the positive pressure q on the spherical surface in the ball seat is:

[0015]

[0016] Among them, R is the inner spherical radius of the ball seat, which is equal to the ball head radius of the mold.

[0017] Furthermore, step 2.2 includes

[0018] 2.2.1. According to the friction law, the friction force per unit area of ​​the spherical surface in the ball seat is obtained The expression is:

[0019]

[0020] Where μ is the friction coefficient;

[0021] —Unit vector in the direction of the contact spherical surface relative to the grinding speed;

[0022] The minus sign before the formula indicates that the friction force is in the opposite direction to the relative grinding speed;

[0023] 2.2.2. Through the relative motion of the ball seat and the mold, using the relationship of spatial activity, the rotational torque of the floating mold generated by the friction force is calculated. The rotational torque is equal to the algebraic sum of the friction force on the Z′ axis torque, then:

[0024]

[0025] Then M is:

[0026]

[0027] in: The axial unit vector,

[0028] — Angular velocity vector of the abrasive tool around the Z′ axis;

[0029] -The moment radius vector of the mold rotation.

[0030] Moreover, in step 2.3, the friction rotation torque during the grinding process is related to the pressure value N input to the mold; the friction resistance torque M0 between the pressure piece that inputs pressure to the mold and the mold, the pressure piece and the pressure input end face of the mold are in planar contact, then the calculation of M0 is M0=M according to the torque balance condition.

[0031] The advantages and positive effects of the present invention are:

[0032] The compensation method of the present invention establishes a compensation model. According to the supplementary model, when the inner spherical surface of the ball hinge is ground at high speed, the input force is adjusted by using the input member, so that the pressure acting on the floating grinding tool changes with the change of the removal amount of grinding, thereby realizing the error compensation of the floating grinding tool force, ensuring the invariance of friction and various friction parameters, eliminating the change of force caused by the error change of the cumulative grinding depth, and ensuring the effect and efficiency of grinding. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a schematic diagram of the structure of the ball seat and the grinding tool involved in the present invention;

[0034] Figure 2 This is a schematic diagram of the grinding principle of the spherical surface grinding tool of the ball hinge of the present invention;

[0035] Figure 3 It is a force diagram of the ball seat of the ball hinge of the present invention. DETAILED DESCRIPTION

[0036] The structure of the present invention is further described below with reference to the accompanying drawings and by way of examples. It should be noted that the present examples are descriptive rather than restrictive.

[0037] The present invention studies the force analysis of ball hinge grinding, and takes the case of grinding with a spherical grinding tool, rotating the ball seat, and floating the grinding tool as an example. The ball seat rotates around its own rotation axis Z at an angular velocity Ω, and under the action of the friction torque, the floating grinding tool rotates around its own axis Z' at an angular velocity ω. The process requires that the ball seat rotation axis Z does not coincide with the grinding tool rotation axis Z', and there is a deflection angle a. During the working process, the deflection angle a changes at any time with the change of the grinding amount. This is the swing reflected by the floating grinding tool with the rotation change of the ball seat.

[0038] As shown in the attached figure, a method for compensating the force of a floating grinding tool for grinding the inner spherical surface of a ball hinge comprises the following steps:

[0039] Step 1, confirm the angle φ between the normal direction of each grinding point on the spherical surface and the rotation axis of the grinding tool;

[0040] The above method for obtaining the φ angle is as follows: the ball seat is measured using a high-precision three-coordinate measuring instrument to uniformly collect three-standard data of a large number of discrete points; the three-coordinate data is processed by reverse engineering software to construct an accurate digital model of the spherical surface after research, and then the normal direction and pressure distribution of each point on the spherical surface can be obtained through the Ansys software algorithm, and the software directly obtains the magnitude and angle of the resultant force;

[0041] Step 2: According to the angle φ between the normal direction of the spherical grinding point and the abrasive tool axis, a pressure compensation mathematical model is established, including:

[0042] (1) Using the pressure N applied to the floating mold, calculate the positive pressure q on the spherical surface in the ball seat;

[0043] (2) Calculate the rotational torque of the grinding tool by using the friction force generated between the grinding tool surface and the spherical surface inside the ball seat;

[0044] (3) In spherical grinding, the contact between the pressure piece and the grinding tool is set to be a plane contact, and the friction resistance torque between the pressure piece and the grinding tool is calculated.

[0045] Step 3: In actual grinding, the pressure input to the grinding tool is adjusted from time to time according to the established pressure compensation mathematical model to achieve pressure compensation.

[0046] The method for establishing the pressure compensation mathematical model is as follows:

[0047] During the stable grinding process, the ball seat is subjected to a downward force. The forces acting on the ball seat are: the pressure N input to the mold; the normal reaction force of the mold, that is, the pressure q(φ,θ) between the mold and the ball seat, which is a function of φ,θ; the friction force F per unit area; and the friction resistance torque M0 between the pressure piece and the mold, which is the pressure input to the mold.

[0048] In this set of spatial force systems, the ball seat is in a state of equilibrium under the action of the force system. When the pressure N is known, the distribution and magnitude of the positive pressure q(φ,θ) on the ball seat can be calculated; then the distribution and magnitude of the friction force F, the friction driving force and the friction resistance M0 can be calculated, and the force error compensation can be achieved as the grinding amount is removed during the grinding process.

[0049] First, during the grinding process of the spherical surface, the pressure distribution between the grinding tool and the inner spherical surface is affected by the rotation of the ball seat. The pressure distribution in the spherical space is complex, and the pressure values ​​are different at different angles. In certain grinding situations, the distribution of q is determined. When the distribution of q is symmetrical with the Z′ axis, it has nothing to do with the angle θ and is only a function of the angle φ. When φ=0, q is at most q0, and when φ=π / 2φ, q is 0. Find the value of q0, solve the pressure distribution, and achieve pressure compensation. During the grinding process, maintain pressure balance and use the balance conditions of external forces in the Z′ axis direction:

[0050] Calculate the pressure on the tee:

[0051]

[0052] It is concluded that the pressure value on the ball seat is related to the pressure input to the grinding tool. With the removal of the grinding amount and the slight change in the gap, the pressure value q on the spherical surface in the ball seat changes. In order to keep the required pressure value q unchanged, the structure is adjusted to change the pressure value N input to the grinding tool to achieve pressure error compensation.

[0053] Secondly, the inner spherical surface of the ball seat is in contact with the surface of the grinding tool to complete the grinding of the inner spherical surface of the ball seat. The friction force per unit area of ​​the inner spherical surface of the ball seat is The expression, according to the friction law, is:

[0054]

[0055] Where: μ—friction coefficient;

[0056] —Unit vector of the contact sphere in the direction of the relative grinding speed.

[0057] The minus sign before the formula indicates that the friction force is in the opposite direction to the relative grinding speed.

[0058] It is concluded that during the grinding process of the spherical surface in the ball seat, changing the value of the pressure N input to the grinding tool can change the magnitude of the friction force, and the error compensation of the friction force can be achieved during the grinding process.

[0059] Finally, when calculating the friction between the spherical surfaces, the relative motion of the ball seat and the mold is used to calculate the rotational torque of the floating mold generated by the friction force using the relationship of spatial activity. This rotational torque is equal to the algebraic sum of the friction force on the Z′ axis torque. Then the following formula is obtained:

[0060]

[0061] Calculate M as:

[0062]

[0063] in: The axial unit vector,

[0064] — Angular velocity vector of the abrasive tool around the Z′ axis;

[0065] -The moment radius vector of the mold rotation.

[0066] During the grinding process, the friction rotation torque is related to the pressure value N input to the abrasive tool. The friction resistance torque M0 between the pressure piece that inputs pressure to the abrasive tool and the abrasive tool is a plane contact between the pressure piece and the pressure input end surface of the abrasive tool, so the calculation of M0 is based on the torque balance condition of M0=M.

[0067] In the process described above, the floating abrasive tool realizes the grinding of the inner spherical surface. During the grinding process, as the grinding amount is removed, the relevant parameter sizes change in uncertain directions. In order to ensure normal grinding and not affect the quality of processing, it is necessary to input a variable pressure to the floating abrasive tool, and use the input part to adjust the change of input force to achieve error compensation of the floating abrasive tool force, ensure the invariance of friction and various friction parameters, eliminate the change of force caused by the error change of the cumulative grinding depth, and ensure the effect and efficiency of grinding.

[0068] Although the embodiments and drawings of the present invention are disclosed for illustrative purposes, those skilled in the art will appreciate that various substitutions, changes and modifications are possible without departing from the spirit and scope of the present invention and the appended claims. Therefore, the scope of the present invention is not limited to the contents disclosed in the embodiments and drawings.

Claims

1. A method for compensating the force of a floating grinding tool for grinding the inner spherical surface of a ball hinge, characterized in that: The ball seat is set to rotate around its own rotation axis Z, and under the action of the friction torque, the floating abrasive tool rotates around its own axis Z', and the ball seat rotation axis Z does not coincide with the abrasive tool rotation axis Z'; the steps include: Step 1, confirm the angle φ between the normal direction of each grinding point on the spherical surface and the rotation axis of the grinding tool; Step 2: According to the angle φ between the normal direction of the spherical grinding point and the abrasive tool axis, a pressure compensation mathematical model is established, including: 2.

1. Using the pressure N applied to the floating mold, calculate the positive pressure q on the spherical surface in the ball seat; 2.

2. Use the friction force between the surface of the mold and the spherical surface inside the ball seat to calculate the rotational torque of the mold; 2.

3. In spherical grinding, the contact between the pressure piece and the abrasive tool is set as plane contact, and the friction resistance torque between the pressure piece and the abrasive tool is calculated; Step 3: In actual grinding, the pressure input to the grinding tool is adjusted from time to time according to the established pressure compensation mathematical model to achieve pressure compensation.

2. The method for compensating the force of a floating grinding tool for grinding the inner spherical surface of a ball hinge according to claim 1, characterized in that: In step 1, the method for obtaining the φ angle is: use a high-precision three-coordinate measuring instrument to measure the ball seat and evenly collect three-standard data of a large number of discrete points; the three-coordinate data is processed by reverse engineering software to construct an accurate mathematical model of the spherical surface after research, and then through the Ansys software algorithm, the normal direction and pressure distribution of each point on the spherical surface can be obtained, and the software directly obtains the size and angle of the resultant force.

3. The method for compensating the force of a floating grinding tool for grinding the inner spherical surface of a ball hinge according to claim 1, characterized in that: In step 2.1, the positive pressure q on the spherical surface in the ball seat is: Among them, R is the inner spherical radius of the ball seat, which is equal to the ball head radius of the mold.

4. The method for compensating the force of a floating grinding tool for grinding the inner spherical surface of a ball hinge according to claim 3, characterized in that: Step 2.2 includes: 2.2.

1. According to the friction law, the friction force per unit area of ​​the spherical surface in the ball seat is obtained The expression is: Where μ is the friction coefficient; —Unit vector in the direction of the contact spherical surface relative to the grinding speed; The minus sign before the formula indicates that the friction force is in the opposite direction to the relative grinding speed; 2.2.

2. Through the relative motion of the ball seat and the mold, using the relationship of spatial activity, the rotational torque of the floating mold generated by the friction force is calculated. The rotational torque is equal to the algebraic sum of the friction force on the Z′ axis torque, then: Then M is: in: —Z′ axial unit vector, — Angular velocity vector of the abrasive tool around the Z′ axis; -The moment radius vector of the mold rotation.

5. The method for compensating the force of a floating grinding tool for grinding the inner spherical surface of a ball hinge according to claim 4, characterized in that: In step 2.3, the friction rotation torque during the grinding process is related to the pressure value N input to the mold; the friction resistance torque M0 between the pressure piece that inputs the pressure to the mold and the mold, the pressure piece and the pressure input end surface of the mold are in planar contact, then M0 is calculated according to the torque balance condition as M0=M.

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