Force-position control rolling system and method for surface of tool withdrawal groove of bolt

Abstract

The invention discloses a force position control rolling system and method for the surface of a bolt tool withdrawal groove, and belongs to the technical field of bolt tool withdrawal groove surface strengthening. The system comprises a force measuring unit, a force position control unit and a bolt tool withdrawal groove rolling unit; and the force control unit can regulate and control the position extension and retraction of the bolt tool withdrawal groove rolling unit, so that the rolling force consistency control when the tool withdrawal groove rolling wheel rolls the surface of the tool withdrawal groove is realized. The rolling wheel with the taper angle is designed and is combined with a rolling method in the axial direction of the bolt, and the limitation that a forming rolling wheel used for manual rolling is suitable for machining the contour of a special tool withdrawal groove is avoided. According to the method, the average discrete deviation degree of rolling force is reduced, and the surface machining quality, consistency and machining efficiency of the tool withdrawal groove of the bolt are improved. The device can be widely popularized in the fields of bolt surface rolling and complex curved surface rolling.

Description

Technical Field

[0001] The present invention relates to the technical field of surface strengthening of bolt relief grooves, and in particular to a force-position control rolling system and a rolling method for the surface of bolt relief grooves. Background Art

[0002] The connection of ultra-high strength steel bolts is one of the main forms of connection of key load-bearing structural components in aerospace. However, during the long-term operation of aerospace equipment, bolt fasteners mainly bear large alternating loads and vibration shocks, and it is very easy to form micro-cracks on the bolt surface, which can cause fatigue fracture. According to data statistics, more than 32% of the failures in aerospace are caused by threaded connections, and the failures usually occur in three stress concentration areas: the fillet under the bolt head, the root of the thread, and the transition area between the bolt rod and the thread (bolt relief groove). It can be seen that improving the surface quality of bolts by a certain specific method is of great significance for improving the service life of bolts. Surface rolling strengthening is an economical, environmentally friendly and efficient anti-fatigue manufacturing technology, which can introduce double effects of finishing and strengthening on the machined surface, thereby improving the surface fatigue resistance.

[0003] At present, the rolling processing method of bolt relief grooves is mainly carried out on a manual lathe. A forming rolling wheel with the same contour as the bolt relief groove is used. The surface rolling of the bolt relief groove is completed by manual visual tool setting and using a fixed rolling amount and spindle speed. After that, the bolt is disassembled to observe the surface indentation, and the tool angle is adjusted, and the above rolling process is repeated until the surface is bright and uniform. The above method has the following problems:

[0004] 1. Manual visual tool setting results in low tool setting accuracy and poor tool setting consistency during batch production;

[0005] 2. Manual clamping error, machining error of machine tool accuracy, and bolt size error will all cause inconsistent rolling force during the rolling process;

[0006] 3. The forming rolling wheel is only suitable for the processing of specific structural contour samples, and its universality is very poor; and multiple manual visual observations of the rolling surface and multiple repeated rolling processes result in low processing efficiency.

[0007] Patent CN114178777B discloses a bolt rolling strengthening equipment and its tool setting method. The invention provides a bolt tool setting method, which solves the problem of low tool setting accuracy caused by manual visual tool setting. However, the problems of unstable rolling force, poor universality of the forming rolling wheel and low processing efficiency during the rolling process of the bolt relief groove in this invention are still not solved. Summary of the Invention

[0008] In order to solve the above problems existing in the prior art, the present invention is to design a force-position control rolling system and a rolling method for the surface of bolt relief grooves, which can achieve stable rolling force, improve universality, processing efficiency and quality.

[0009] To achieve the above object, the technical solution of the present invention is as follows:

[0010] A force-position control rolling system for the surface of a bolt relief groove, comprising a force measuring unit, a force-position control unit and a bolt relief groove rolling unit.

[0011] The force measuring unit includes a host computer, a force measuring sensor, a machine tool tool holder, a slide rail and a machine tool bed. The force measuring sensor is fixedly connected to the machine tool tool holder. The lower end of the machine tool tool holder is equipped with a slide rail and is fixed on the machine tool bed. The host computer is connected to the force measuring sensor to collect the real-time rolling force data of the rolling wheel.

[0012] The force-position control rolling unit includes a connecting rod, a set screw, a fixing frame, a coupling, a motor and a motion controller. The connecting rod is connected to the motor through a coupling. The motor is fixedly installed on the fixing frame, and the fixing frame is fixed on the machine tool tool holder. The host computer is connected to the motion controller, and the motion controller is connected to the motor.

[0013] The bolt relief groove rolling unit includes a rolling wheel, a bearing, a mandrel, a gland, a lubricating washer, a roller holder, a tool shank, a stud, a spring, a digital display force gauge, a square nut, a guide groove, a pin shaft, a fastening bolt, a washer and a fixing screw.

[0014] The rolling wheel is installed on the mandrel. The mandrel is nested in the bearing. The bearing is installed in the ear hole of the U-shaped structure at the upper end of the roller holder. The lubricating washer is placed between the rolling wheel and the roller holder, and between the mandrel and the roller holder. The gland is fixed on one side of the roller holder. A spring is inserted into the lower end of the stepped groove of the roller holder. The roller holder and the spring are sleeved together in the upper stepped hole inside the tool shank. The digital display force gauge is in a ring structure, and its lower end surface contacts the bottom surface of the upper stepped hole inside the tool shank. A gasket is stuffed between the lower end of the spring and the digital display force gauge. The stud passes through the center of the stepped hole of the roller holder, the spring, the gasket, the digital display force gauge and the stepped hole of the tool shank. The upper end of the stud is threadedly connected to the upper stepped groove inside the roller holder and is fastened with a screw. The lower end of the stud is tightened by a square nut. The square nut contacts the surface of the lower stepped hole of the tool shank and is sleeved with a washer. The pin shaft is fixed to the lower end of the roller holder through a fastening bolt and slides in the guide groove on the tool shank.

[0015] Furthermore, the rolling wheel is an asymmetric disc-shaped structure with a taper angle. The outer diameter of the roller is 60 mm, the diameter at the step is 40 mm, the inner diameter is 12 mm, the taper angle at the outer circle is 45°, and an arc is provided at the edge of the taper angle, and the radius of the arc is 0.9 mm.

[0016] Further, the upper end of the roller stand is of a U-shaped structure with ear holes opened thereon, and the lower end is of a cylindrical structure with a stepped groove opened inside. The diameter of the upper end of the stepped groove is smaller than that of the lower end, and the inner surface of the upper end stepped groove is provided with threads.

[0017] Further, the tool shank is of a cuboid structure with a stepped hole opened from the lower end to the upper end. The diameter of the upper section of the stepped hole is larger than those of the middle and lower sections, and the diameter of the lower section of the stepped hole is larger than that of the middle section. Moreover, a guiding groove is provided on one side of the tool shank.

[0018] Further, the fixing bracket is a thin plate member bent at 90°. A U-shaped hole is opened on the side end face of the fixing bracket and it is assembled on the machine tool tool rest through a set screw.

[0019] Further, a connecting rod is inserted into the coupling. A square groove is provided at the head of the connecting rod and is screwed with a square nut. The connecting rod, the coupling, the motor, the square nut, the tool shank, the digital display force gauge, the spring, the stud and the roller stand are concentric.

[0020] Further, the tool shank and the fixing bracket are installed on the tool rest of the bolt rolling machine through set screws, and the tool rest drives the bolt relief groove rolling unit to move.

[0021] A force-position control rolling method for the surface of a bolt relief groove, which uses a force-position control rolling system for the surface of a bolt relief groove to perform rolling, includes the following steps:

[0022] S1. The upper computer drives the motor, the coupling and the connecting rod to drive the square nut to rotate through regulating the motion controller, so that the spring force compressed by the roller stand is N1. Then, set the rolling force N2 in the force-position control program interface of the upper computer, and N2 < N1.

[0023] S2. The rolling wheel completes automatic tool setting with the bolt relief groove, and the rolling wheel is ready to contact the relief groove.

[0024] S3. The upper computer executes the force-position control program, and the motor drives the connecting rod to loosen the square nut to make the roller stand extend, unloading the spring compression force N3, so that the real-time rolling force value N4 acting on the surface of the bolt relief groove by the rolling wheel is N4 = N2. At this time, N3 = N1 - N4.

[0025] S4. The machine tool tool rest drives the rolling wheel to machine the surface of the relief groove along the axial direction of the bolt. The force measuring sensor transmits the real-time rolling force N4 received by the rolling wheel to the upper computer. The upper computer analyzes the real-time rolling force N4 by using the force-position control program, and drives the motor to rotate the square nut in real time to control the extension or contraction of the rolling wheel to make the rolling force stable at N4 until the rolling of the surface of the bolt relief groove is completed.

[0026] Further, in the step S4, when the real-time rolling pressure N4 > the set rolling pressure N1, it indicates that the rolling wheel compresses the roller frame further under the action of the bolt. At this time, the host computer sends a signal to the motion controller, and the motion controller drives the motor to screw out the square nut to drive the roller frame to contract, reducing the real-time rolling pressure of the rolling wheel on the bolt. The contraction amount ΔX of the rolling wheel = (N4 - N1) / K, where K is the elastic coefficient of the spring.

[0027] Further, when the real-time rolling pressure N4 < the set rolling pressure N1 in the step S4, it indicates that the real-time rolling pressure on the roller frame by the rolling wheel under the action of the bolt is relatively small. At this time, the host computer sends a signal to the motion controller, and the motion controller drives the motor to screw in the square nut to drive the roller frame to extend, increasing the real-time rolling pressure of the rolling wheel on the thread. The extension amount ΔX of the rolling wheel = (N1 - N4) / K.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] 1. The rolling system of the present invention controls the extension and contraction of the rolling wheel in real time through the force measuring unit and the force-position control unit, improving the stability of the rolling pressure acting on the surface of the bolt relief groove, and solving the problems of unstable rolling amount, poor surface quality and consistency of the bolt surface during the rolling process of the bolt relief groove surface.

[0030] 2. The present invention designs a rolling wheel with a taper angle to roll the surface of the bolt relief groove along the axial direction of the bolt. Compared with the extrusion processing method of the forming rolling wheel used in manual processing, it not only improves the processing quality and efficiency, but also improves the universality of the rolling wheel.

[0031] 3. The present invention can be widely promoted in the fields of bolt surface rolling and complex curved surface rolling. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 is the overall structural schematic diagram of the force-position control rolling system of the present invention.

[0033] Figure 2 is Figure 1 the assembly schematic diagram of the machine tool tool rest, the bolt relief groove rolling unit and the force-position control unit components in

[0034] Figure 3 is the structural schematic diagram of the bolt relief groove rolling unit provided by the present invention.

[0035] Figure 4 is Figure 3 the central vertical sectional schematic diagram of

[0036] Figure 5 is Figure 3 the A-A sectional view schematic diagram of

[0037] Figure 6 It is a schematic structural diagram of the rolling wheel provided by the present invention.

[0038] Figure 7 is Figure 6 a partially enlarged schematic view at position B of

[0039] Figure 8 It is a force-position control rolling processing flow chart of an embodiment of the present invention.

[0040] Figure 9 It is a schematic structural diagram of a bolt sample in the embodiment.

[0041] Figure 10 It is a data graph of the real-time rolling force during the rolling processing in the embodiment.

[0042] Figure 11 It is a discrete deviation analysis graph of the real-time rolling force data during the rolling processing in the embodiment.

[0043] Figure 12 It is a data graph of the surface roughness of the relief groove of the ultra-high strength bolt in the embodiment.

[0044] In the figure: 1 - host computer, 2 - motion controller, 3 - motor, 4 - force measuring sensor, 5 - slide rail, 6 - machine tool bed, 7 - machine tool tool rest, 8 - connecting rod, 9 - set screw, 10 - fixing bracket, 11 - coupling, 101 - rolling wheel, 102 - bearing, 103 - mandrel, 104 - gland, 105 - lubricating washer, 106 - roller stand, 107 - tool shank, 108 - stud, 109 - spring, 110 - digital display force gauge, 111 - square nut, 112 - guide groove, 113 - pin shaft, 114 - fastening bolt, 115 - gasket, 116 - washer. Specific embodiments

[0045] The present invention will be further described below with reference to the accompanying drawings.

[0046] As Figure 1-12 shown, a force-position control rolling system for the surface of the relief groove of a bolt includes a force measuring unit, a force-position control unit, and a relief groove rolling unit for bolts.

[0047] The force measuring unit includes a host computer 1, a force measuring sensor 4, a machine tool tool rest 7, a slide rail 5, and a machine tool bed 6. The force measuring sensor 4 is fixedly connected to the machine tool tool rest 7. The lower end of the machine tool tool rest 7 is equipped with a slide rail 5 and is fixed on the machine tool bed 6. The host computer 1 is connected to the force measuring sensor 4 to collect the real-time rolling force data of the rolling wheel 101.

[0048] The described force-position control rolling unit includes a connecting rod 8, a set screw 9, a fixing bracket 10, a coupling 11, a motor 3, and a motion controller 2. The connecting rod 8 is connected to the motor 3 through the coupling 11. The motor 3 is fixedly installed on the fixing bracket 10, and the fixing bracket 10 is fixed on the machine tool turret 7. The host computer 1 is connected to the motion controller 2, and the motion controller 2 is connected to the motor 3.

[0049] The described bolt relief groove rolling unit includes a rolling wheel 101, a bearing 102, a mandrel 103, a gland 104, a lubricating washer 105, a roller holder 106, a tool shank 107, a stud 108, a spring 109, a digital display force gauge 110, a square nut 111, a guide groove 112, a pin 113, a fastening bolt 114, a washer 116, and a fixing screw.

[0050] The rolling wheel 101 is installed on the mandrel 103. The mandrel 103 is nested in the bearing 102. The bearing 102 is installed in the ear hole of the U-shaped structure at the upper end of the roller holder 106. The lubricating washer 105 is placed between the rolling wheel 101 and the roller holder 106, and between the mandrel 103 and the roller holder 106. The gland 104 is fixed on one side of the roller holder 106. A spring 109 is inserted into the lower end of the stepped groove of the roller holder 106. The roller holder 106 and the spring 109 are together sleeved in the upper stepped hole inside the tool shank 107. The digital display force gauge 110 is of a ring structure, and its lower end surface contacts the bottom surface of the upper stepped hole inside the tool shank 107. A spacer 115 is stuffed between the lower end of the spring 109 and the digital display force gauge 110. The stud 108 passes through the center of the stepped hole of the roller holder 106, the spring 109, the spacer 115, the digital display force gauge 110, and the stepped hole of the tool shank 107. The upper end of the stud 108 is threadedly connected to the upper stepped groove inside the roller holder 106 and is fastened by a fixing screw. The lower end of the stud 108 is tightened by the square nut 111. The square nut 111 contacts the surface of the lower stepped hole of the tool shank 107 and is sleeved with a washer 116. The pin 113 is fixed to the lower end of the roller holder 106 through the fastening bolt 114, and the pin 113 slides in the guide groove 112 on the tool shank 107.

[0051] Further, the rolling wheel 101 is an asymmetric cake-like structure with a taper angle. The outer diameter of the roller is 60 mm, the diameter at the step is 40 mm, the inner diameter is 12 mm, the taper angle at the outer circle is 45°, and an arc is provided at the edge of the taper angle, and the radius of the arc is 0.9 mm.

[0052] Further, the upper end of the roller holder 106 is of a U-shaped structure, and ear holes are provided on the U-shaped structure. The lower end is of a cylindrical structure, and a stepped groove is provided inside the cylindrical structure. The diameter of the upper end of the stepped groove is smaller than that of the lower end, and a thread is provided on the inner surface of the upper stepped groove.

[0053] Further, the tool shank 107 has a cuboid structure, and a stepped hole is drilled from the lower end to the upper end of the tool shank 107. The diameter of the upper section of the stepped hole is larger than that of the middle and lower sections, the diameter of the lower section of the stepped hole is larger than that of the middle section, and a guiding groove 112 is provided on one side of the tool shank 107.

[0054] Further, the fixing bracket 10 is a thin plate member bent at 90°. A U-shaped hole is drilled on the side end face of the fixing bracket 10, and it is assembled on the machine tool tool rest 7 through a set screw 9.

[0055] Further, a connecting rod 8 is inserted into the coupling 11. A square groove is provided at the head of the connecting rod 8 and is screwed with a square nut 111; the connecting rod 8, the coupling 11, the motor 3, the square nut 111, the tool shank 107, the digital display force gauge 110, the spring 109, the stud 108 and the roller bracket 106 are concentric.

[0056] Further, the tool shank 107 and the fixing bracket 10 are installed on the tool rest 7 of the bolt rolling machine through set screws 9, and the tool rest drives the bolt relief groove rolling unit to move.

[0057] A force-position control rolling method for the surface of a bolt relief groove, which uses a force-position control rolling system for the surface of a bolt relief groove to perform rolling, includes the following steps:

[0058] S1. The upper computer 1 drives the motor 3, the coupling 11 and the connecting rod 8 to drive the square nut 111 to rotate by regulating the motion controller 2, so that the force of the spring 109 compressed by the roller bracket 106 is N1. Then, set the rolling force N2 in the force-position control program interface of the upper computer 1, and N2 < N1.

[0059] S2. The rolling wheel 101 completes automatic tool alignment with the bolt relief groove, and the rolling wheel 101 is ready to contact the relief groove.

[0060] S3. The upper computer 1 executes the force-position control program, and the motor 3 drives the connecting rod 8 to loosen the square nut 111 to extend the roller bracket 106, unloading the compression force N3 of the spring 109, so that the real-time rolling force value N4 acting on the surface of the bolt relief groove by the rolling wheel 101 is N4 = N2. At this time, N3 = N1 - N4.

[0061] S4. The machine tool tool rest 7 drives the rolling wheel 101 to machine the surface of the relief groove along the axial direction of the bolt. The force measuring sensor 4 transmits the real-time rolling force N4 received by the rolling wheel 101 to the upper computer 1. The upper computer 1 analyzes the real-time rolling force N4 by using the force-position control program, and drives the motor 3 to rotate the square nut 111 in real time to control the extension or contraction of the rolling wheel 101 to keep the rolling force stable at N4 until the rolling of the surface of the bolt relief groove is completed.

[0062] Further, in step S4, when the real-time rolling pressure N4 > the set rolling pressure N1, it indicates that the rolling wheel 101 acts on the bolt, causing the roller frame 106 to be further compressed. At this time, the host computer 1 sends a signal to the motion controller 2, and the motion controller 2 drives the motor 3 to screw out the square nut 111 to drive the roller frame 106 to contract. The real-time rolling pressure of the rolling wheel 101 acting on the bolt decreases. The contraction amount ΔX of the rolling wheel 101 = (N4 - N1) / K, where K is the elastic coefficient of the spring 109.

[0063] Further, when the real-time rolling pressure N4 < the set rolling pressure N1 in step S4, it indicates that the real-time rolling pressure on the roller frame 106 caused by the rolling wheel 101 acting on the bolt is relatively small. At this time, the host computer 1 sends a signal to the motion controller 2, and the motion controller 2 drives the motor 3 to screw the square nut 111 in to drive the roller frame 106 to extend. The real-time rolling pressure of the rolling wheel 101 acting on the thread increases. The extension amount ΔX of the rolling wheel 101 = (N1 - N4) / K.

[0064] The embodiments of the present invention include the following steps:

[0065] T1. In this embodiment, the processed material is the bolt relief groove of 300M steel, and the structure of the bolt relief groove is as Figure 9 shown. The initial roughness is 0.50 μm, as Figure 11 shown.

[0066] T2. Set the rolling pressure to 350 N, the spindle speed to 600 r / min, and the axial feed rate to 0.01 mm / r.

[0067] T3. The host computer 1 drives the motor 3 to drive the square nut 111 to rotate through the motion controller 2, so that the spring 109 force N1 = 400 N that compresses the roller frame 106. Then, input the set rolling pressure N2 = 350 N in the force control program interface of the host computer 1.

[0068] T4. The rolling wheel 101 completes automatic tool alignment with the bolt relief groove, and the rolling wheel 101 is ready to contact the relief groove.

[0069] T5. The host computer 1 executes the force-position control program, and the motor 3 unscrews the square nut 111 to make the roller frame 106 extend, unloading the spring 109 compression force N3 = 50 N, so that the real-time rolling pressure value N4 of the rolling wheel 101 acting on the bolt relief groove surface = N2 = 350 N.

[0070] T6. The machine tool turret 7 drives the rolling wheel 101 to machine the surface of the relief groove along the axial direction of the bolt. The force sensor 4 transmits the real-time rolling force received by the rolling wheel 101 to the host computer 1, and the host computer 1 analyzes the real-time rolling force by using the force-position control program. When the real-time rolling force N4 > the set rolling force N2, the host computer 1 sends a signal to the motion controller 2, and the motion controller 2 drives the motor 3 to rotate the square nut 111 outwards to drive the roller frame 106 to contract, and the real-time rolling force of the rolling wheel 101 acting on the bolt decreases. The contraction amount ΔX of the roller frame 106 = (N4 - 350) / K, where K is the elastic coefficient of the spring 109. When the real-time rolling force N4 < the set rolling force N2, it indicates that the real-time rolling force received by the roller frame 106 is small due to the action of the bolt on the rolling wheel 101. The host computer 1 sends a signal to the motion controller 2, and the motion controller 2 drives the motor 3 to rotate the square nut 111 inwards to drive the roller frame 106 to extend, and the real-time rolling force of the rolling wheel 101 acting on the thread increases. The extension amount ΔX of the rolling wheel 101 = (350 - N4) / K. And the motor 3 is driven to rotate the square nut 111 in real time to control the extension or contraction of the rolling wheel 101 to make the rolling force stable at N4 = 350 N until the rolling of the surface of the bolt relief groove is completed.

[0071] In the process of rolling the relief groove along the axial direction of the bolt in this embodiment, the original surface has a high roughness. During the force-position control rolling process, the rolling wheel 101 causes plastic deformation on the surface of the relief groove, and plastic flow occurs along the axial movement, and the surface roughness is significantly reduced.

[0072] After the rolling of the bolt relief groove is completed in this embodiment, the rolling force collected by the host computer 1 is analyzed. As Figure 10 shown, the fluctuation range of the rolling force processed by the force-position control rolling system in this embodiment is significantly smaller, and the fluctuation range of the traditional manual processing rolling force is larger. By analyzing the rolling force data with the average discrete deviation, the average absolute deviation of the force-position control rolling process is 23.9 N. Compared with the average absolute deviation of 52.84 N of the traditional manual rolling process, the degree of dispersion is reduced by 54.8%, as Figure 11 shown. The rolling force data results show that the force-position control rolling system of the present invention significantly improves the consistency of the rolling force.

[0073] After the rolling of the bolt relief groove is completed in this embodiment, the surface roughness of the relief groove is detected by using a 3D surface optical profiler ZYGO Nex View. As Figure 12 shown, the surface roughness value of the bolt relief groove processed by the force-position control rolling system in this embodiment is 0.14 μm. Compared with the initial surface roughness of the bolt relief groove of 0.5 μm and the surface roughness of the bolt relief groove after manual rolling of 0.26 μm, the surface roughness of the force-position control rolling process is the lowest, and the error fluctuation is the smallest. The detection results show that the present invention can effectively improve the rolling quality.

[0074] The results of the embodiments show that the present invention solves the problems of poor consistency in rolling amount and poor surface quality in the existing manual rolling process. At the same time, the rolling wheel 101 of the present invention has a structure with a taper angle, and is processed by axial movement along the surface profile of the bolt relief groove, which can adapt to bolt relief grooves with various structural profiles, and solves the limitation problem of the forming rolling wheel 101 used in manual processing.

[0075] The present invention is not limited to this embodiment, and any equivalent concept or change within the technical scope disclosed by the present invention shall be included in the protection scope of the present invention.

Claims

1. A force-position control rolling system for the surface of a bolt relief groove, characterized in that: It includes a force measuring unit, a force-position control unit and a bolt relief groove rolling unit; The force measuring unit includes a host computer (1), a force measuring sensor (4), a machine tool turret (7), a slide rail (5) and a machine tool bed (6). The force measuring sensor (4) is fixedly connected to the machine tool turret (7). The lower end of the machine tool turret (7) is equipped with a slide rail (5) and is fixed on the machine tool bed (6). The host computer (1) is connected to the force measuring sensor (4) to collect the real-time rolling force data of the rolling wheel (101); The force-position control rolling unit includes a connecting rod (8), a set screw (9), a fixing bracket (10), a coupling (11), a motor (3) and a motion controller (2); the connecting rod (8) is connected to the motor (3) through the coupling (11). The motor (3) is fixedly installed on the fixing bracket (10), and the fixing bracket (10) is fixed on the machine tool turret (7); the host computer (1) is connected to the motion controller (2), and the motion controller (2) is connected to the motor (3); The bolt relief groove rolling unit includes a rolling wheel (101), a bearing (102), a mandrel (103), a gland (104), a lubricating washer (105), a roller holder (106), a tool shank (107), a stud (108), a spring (109), a digital display force gauge (110), a square nut (111), a guide groove (112), a pin shaft (113), a fastening bolt (114), a washer (116) and a fixing screw; The rolling wheel (101) is installed on the mandrel (103). The mandrel (103) is nested in the bearing (102). The bearing (102) is installed in the ear hole of the U-shaped structure at the upper end of the roller holder (106). The lubricating washer (105) is padded between the rolling wheel (101) and the roller holder (106), and between the mandrel (103) and the roller holder (106). The gland (104) is fixed on one side of the roller holder (106); a spring (109) is inserted into the lower end of the stepped groove of the roller holder (106). The roller holder (106) and the spring (109) are together sleeved in the upper stepped hole inside the tool shank (107); the digital display force gauge (110) is of a circular ring structure, and its lower end surface contacts the bottom surface of the upper stepped hole inside the tool shank (107). A gasket (115) is stuffed between the lower end of the spring (109) and the digital display force gauge (110); the stud (108) passes through the center of the stepped hole of the roller holder (106), the spring (109), the gasket (115), the digital display force gauge (110) and the stepped hole of the tool shank (107); the upper end of the stud (108) is threadedly connected to the upper stepped groove inside the roller holder (106) and is fastened by a fixing screw; the lower end of the stud (108) is tightened by a square nut (111). The square nut (111) contacts the surface of the lower stepped hole of the tool shank (107) and is sleeved with a washer (116); the pin shaft (113) is fixed to the lower end of the roller holder (106) through the fastening bolt (114), and the pin shaft (113) slides in the guide groove (112) on the tool shank (107).

2. The force-position control rolling system for the surface of the bolt relief groove according to claim 1, wherein: The described rolling wheel (101) has an asymmetrical disc shape with a taper angle. The outer diameter of the roller is 60 mm, the diameter at the step is 40 mm, the inner diameter is 12 mm, the taper angle at the outer circle is 45°, and an arc is provided at the edge of the taper angle with a radius of 0.9 mm.

3. The force-position control rolling system for the surface of the bolt relief groove according to claim 1, wherein: The upper end of the described roller holder (106) is of a U-shaped structure with ear holes opened thereon, and the lower end is of a cylindrical structure with a stepped groove opened inside. The diameter of the upper end of the stepped groove is smaller than that of the lower end, and a thread is provided on the inner surface of the upper stepped groove.

4. The force-position control rolling system for the surface of the bolt relief groove according to claim 1, wherein: The described tool holder (107) is of a cuboid structure, and a stepped hole is opened from the lower end to the upper end of the tool holder (107). The diameter of the upper section of the stepped hole is larger than those of the middle and lower sections, the diameter of the lower section of the stepped hole is larger than that of the middle section, and a guiding groove (112) is provided on one side of the tool holder (107).

5. The force-position control rolling system for the surface of the bolt relief groove according to claim 1, wherein: The described fixing bracket (10) is a thin plate member bent at 90°. A U-shaped hole is opened on the side end face of the fixing bracket (10), and it is assembled on the machine tool tool rest (7) through a set screw (9).

6. The force-position control rolling system for the surface of the bolt relief groove according to claim 1, wherein: A connecting rod (8) is inserted into the described coupling (11). A square groove is provided at the head of the connecting rod (8) and is screwed with a square nut (111); the described connecting rod (8), coupling (11), motor (3), square nut (111), tool holder (107), digital display force gauge (110), spring (109), stud (108), and roller holder (106) are concentric.

7. The force-position control rolling system for the surface of the bolt relief groove according to claim 1, characterized in that: The described tool holder (107) and fixing bracket (10) are installed on the tool rest (7) of the bolt rolling machine through set screws (9), and the tool rest drives the bolt undercut rolling unit to move.

8. A force-position control rolling method for the surface of a bolt undercut, which uses any one of the force-position control rolling systems for the surface of a bolt undercut as claimed in claims 1-7 for rolling, including the following steps: S1. The upper computer (1) drives the motor (3), coupling (11), and connecting rod (8) through the regulated motion controller (2) to drive the square nut (111) to rotate, so that the force of the spring (109) compressed by the roller holder (106) is N1. Then, set the rolling force N2 in the force-position control program interface of the upper computer (1), and N2 < N1; S2. The rolling wheel (101) and the bolt undercut complete automatic tool alignment, and the rolling wheel (101) is ready to contact the undercut; S3. The upper computer (1) executes the force-position control program, and the motor (3) drives the connecting rod (8) to unscrew the square nut (111) to extend the roller holder (106), unloading the compression force N3 of the spring (109), so that the real-time rolling force value N4 of the rolling wheel (101) acting on the surface of the bolt undercut is N4 = N2. At this time, N3 = N1 - N4; S4. The machine tool tool rest (7) drives the rolling wheel (101) to process the surface of the undercut along the axial direction of the bolt. The force measuring sensor (4) transmits the real-time rolling force N4 received by the rolling wheel (101) to the upper computer (1). The upper computer (1) analyzes the real-time rolling force N4 using the force-position control program and drives the motor (3) to rotate the square nut (111) in real time to control the extension or contraction of the rolling wheel (101) to make the rolling force stable at N4 until the rolling of the surface of the bolt undercut is completed.

9. A force-position controlled rolling method for the surface of a bolt relief groove according to claim 8, characterized in that: In step S4, when the real-time rolling pressure N4 > the set rolling pressure N1, it indicates that the rolling wheel (101) acts on the bolt to further compress the roller frame (106). At this time, the host computer (1) sends a signal to the motion controller (2), and the motion controller (2) drives the motor (3) to screw out the square nut (111) to drive the roller frame (106) to contract. The real-time rolling pressure of the rolling wheel (101) acting on the bolt decreases, and the contraction amount ΔX of the rolling wheel (101) = (N4 - N1) / K, where K is the elastic coefficient of the spring (109).

10. The force-position controlled rolling method for the surface of the bolt relief groove according to claim 8, wherein: In step S4, when the real-time rolling pressure N4 < the set rolling pressure N1, it indicates that the real-time rolling pressure on the roller frame (106) caused by the rolling wheel (101) acting on the bolt is relatively small. At this time, the host computer (1) sends a signal to the motion controller (2), and the motion controller (2) drives the motor (3) to make the square nut (111) screw in to drive the roller frame (106) to extend, and the real-time rolling pressure of the rolling wheel (101) acting on the thread increases. The extension amount ΔX of the rolling wheel (101) = (N1 - N4) / K.

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