Polishing clamp, polishing apparatus, and polishing method

Abstract

Provided is a lapping technique capable of flexibly adjusting the holding posture of a ball screw nut and performing lapping finish using a shaping tool. The lapping technique includes a jig base fixedly arranged on a rotation center shaft, and a profiling holding portion installed to the jig base, which changes the posture of the ball screw nut relative to the jig base while profiling a processing region in the outer side surface of the shaping tool that is in sliding contact with the thread groove to perform grinding processing on the thread groove, and which holds the ball screw nut.

Description

[0001] This application is a divisional application of the invention patent application filed on April 28, 2021, with application number 201980071521.7, application date February 8, 2019, international application number PCT / JP2019 / 004594, entitled "Grinding jig, grinding apparatus and grinding method". Technical Field

[0002] This invention relates to the retention of a ball screw nut during grinding and finishing by grinding the thread groove of a ball screw nut using a forming tool. Background Technology

[0003] Traditionally, ball screw mechanisms have been used as one of the drive mechanisms in industrial robots. The ball screw nut used in this mechanism has a helical thread groove formed inside to allow the balls to roll. After the thread groove is formed into a specified shape by cutting, it is finished to the final size by grinding, also known as lapping, using a forming tool.

[0004] The grinding process is performed using a grinding apparatus, for example, as shown in Patent Document 1. In the apparatus described in Patent Document 1, a chuck unit (equivalent to the "grinding fixture" of the present invention) with three chuck jaws is used to hold the ball screw nut. Furthermore, above the chuck unit, with the axis of a grinding rod (equivalent to the "forming tool" of the present invention) having a shaft structure aligned with a rotational center axis extending in the vertical direction, the grinding rod is configured to rotate while reciprocating in the vertical direction. The rotating grinding rod is then screwed into the ball screw nut held by the chuck unit at a predetermined rotational speed and a predetermined feed rate, thereby performing the grinding process.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2002-292520 ( Figure 7 ) Summary of the Invention

[0008] The problem that the invention aims to solve

[0009] Thus, in the grinding apparatus of Patent Document 1, the ball screw nut is fixedly held by a chuck unit, and the grinding rod moves up and down along a track extending in the vertical direction. That is, in this grinding apparatus, grinding is performed on the premise that the axis of the ball screw nut held by the chuck unit is aligned with the axis of the grinding rod (rotation center axis). Therefore, if, for example, at least one of the holding posture of the ball screw nut by the chuck unit or the setting posture of the grinding rod is inappropriate, their axes will misalign, making it difficult to perform grinding with sufficient machining accuracy. In particular, if the ball screw nut deforms due to heat treatment performed between cutting and grinding, the holding posture of the ball screw nut by the chuck unit becomes poor, which cannot be addressed by existing apparatuses.

[0010] The present invention was made in view of the above-mentioned problems, and its object is to provide a grinding technology that can flexibly adjust the holding posture of the ball screw nut and perform grinding and finishing using a forming tool.

[0011] Technical solutions for solving the problem

[0012] The first aspect of the present invention is a grinding fixture that holds a ball screw nut that has been ground and finished by a forming tool grinding its thread groove. The forming tool rotates about a rotational central axis extending in a first direction and reciprocates in the first direction. The grinding fixture is characterized by comprising: a fixture base fixedly disposed on the rotational central axis; and a contour holding part mounted on the fixture base, which holds the ball screw nut by changing the posture of the ball screw nut relative to the fixture base while mimicking the processing area on the outer surface of the forming tool that slides in contact with the thread groove to grind the thread groove.

[0013] Another aspect of the present invention is a grinding apparatus that performs grinding finishing by grinding the thread groove of a ball screw nut using a forming tool having a shaft structure extending in a first direction. The apparatus is characterized by comprising: the aforementioned grinding fixture; and a tool drive unit that rotates the forming tool about a rotation center axis extending in the first direction while reciprocating the forming tool relative to the ball screw nut held in the grinding fixture in the first direction.

[0014] Furthermore, the third aspect of the present invention is a grinding method that uses a forming tool having a shaft structure extending in a first direction to grind the thread groove of a ball screw nut for finishing. The method is characterized by comprising: a first step of holding the ball screw nut in the grinding fixture; and a second step of rotating the forming tool about a rotation center axis extending in the first direction while reciprocating the forming tool relative to the ball screw nut held in the grinding fixture in the first direction.

[0015] In this invention, grinding and finishing are performed by rotating a forming tool about a rotational center axis extending in a first direction while simultaneously reciprocating the forming tool relative to the ball screw nut in the first direction, thereby grinding the thread groove of the ball screw nut. During this grinding and finishing process, the ball screw nut is held in a position that mimics the grinding area on the outer surface of the forming tool where the thread groove is slidably ground. Therefore, grinding and finishing are performed with the axis of the forming tool aligned with the axis of the ball screw nut.

[0016] Invention Effects

[0017] As described above, a grinding fixture is used to maintain the ball screw nut while changing its position, mimicking the machining area on the outer surface of a forming tool that slides into the thread groove to grind it. Therefore, grinding and finishing using a forming tool can be performed efficiently by flexibly adjusting the holding position of the ball screw nut. Attached Figure Description

[0018] Figure 1 This is a diagram illustrating a first embodiment of the grinding apparatus according to the present invention.

[0019] Figure 2 It means in Figure 1 A perspective view of the grinding fixture used in the grinding apparatus shown.

[0020] Figure 3 It means Figure 1 A block diagram of the electrical structure of the grinding device shown.

[0021] Figure 4A It is a diagram that schematically illustrates the movement of the grinding fixture in the grinding and finishing process.

[0022] Figure 4B This is a schematic diagram showing the movement of the grinding fixture 2 before and after grinding and finishing.

[0023] Figure 5 It means to utilize Figure 1 A flowchart showing the grinding and finishing steps performed by the grinding apparatus shown.

[0024] Figure 6 It is a schematic representation of the use Figure 1 The diagram shows the steps of the grinding and finishing process performed by the grinding apparatus shown.

[0025] Figure 7This diagram schematically illustrates the additional steps of the grinding and finishing process performed using the grinding apparatus according to the second embodiment of the present invention. Detailed Implementation

[0026] Figure 1 This is a diagram illustrating a first embodiment of the grinding apparatus according to the present invention. Additionally, Figure 2 It means in Figure 1 A perspective view of the grinding fixture used in the shown grinding apparatus. Furthermore, Figure 3 It means Figure 1 The diagram shows a block diagram of the electrical structure of the grinding apparatus. The grinding apparatus 1, with the axis AX1 of a forming tool (hereinafter referred to as "machining tool") 100 having a shaft structure extending in the vertical direction Z aligned with the rotation center axis AR, moves the machining tool 100 while rotating around the rotation center axis AR and reciprocating in the Z direction. This allows the machining tool 100 to perform grinding finishing by grinding the thread groove 201 of a ball screw nut 200 (hereinafter referred to as "nut 200") held in the grinding fixture 2. Furthermore, Figure 1 and Figure 2 To clarify the directional relationships in each figure, the XYZ rectangular coordinate axes are shown. In these figures, the vertical direction Z corresponds to an example of the "first direction" of this invention, with arrow Z1 pointing towards the outward direction of the machining tool 100 and arrow Z2 pointing towards the return direction of the machining tool 100. The XYZ rectangular coordinate axes are shown through this vertical direction Z and the horizontal directions X and Y, which are orthogonal to the Z direction. Figure 1 and Figure 2 Furthermore, the Y direction corresponds to an example of the "second direction" of the present invention, where arrow Y1 in the Y direction points towards the left side of the polishing device 1 when viewed from the front side, and arrow Y2 in the Y direction points towards the right side of the polishing device 1. Additionally, the X direction corresponds to an example of the "third direction" of the present invention, where arrow X1 in the X direction points towards the front side of the polishing device 1, and arrow X2 in the X direction points towards the back side of the polishing device 1. Moreover, Figure 1 The arrow R in the diagram indicates the rotation direction of the machining tool 100.

[0027] like Figure 1As shown, the grinding apparatus 1 includes: a base 3; a ball screw nut support device 4 mounted on the upper front side of the base 3; an upper support platform 5 erected on the upper back side of the base 3; a lifting head 7 supported on the upper support platform 5 via a lifting device 6; and a rotary drive device 8 disposed on the lifting head 7. The ball screw nut support device 4 is configured such that the worktable 42 is raised and lowered in the vertical direction Z by operating an operating lever 41. Furthermore, a grinding fixture 2 is fixed to the upper surface of the worktable 42, and the nut 200 can be easily held in place by the grinding fixture 2. The detailed structure and operation of the grinding fixture 2 will be described in detail later.

[0028] Above the grinding fixture 2 holding the nut 200, as Figure 1 As shown, the lifting head 7 is configured to reciprocate along the vertical direction Z, and is driven by the lifting device 6. Figure 1 As shown, the lifting device 6 includes: a pair of left and right slide rails 61, 61 mounted on the front (X1 direction side) of the upper support platform 5 extending along the vertical direction Z. Figure 1 The diagram only shows the Y2 direction side); a slider 62 supported by these slide rails 61, 61; a ball screw nut 63 installed at the center of the slider 62 in the left-right direction Y; a ball screw shaft 64 extending through the ball screw nut 63 and along the vertical direction Z; and a lifting motor 65 connected to the upper end of the ball screw shaft 64. Furthermore, according to the command from the control device 9 controlling the entire grinding apparatus 1, the lifting motor 65 rotates forward, thereby enabling the lifting head 7 configured as follows to move in the forward direction (Z1 direction side); on the other hand, the lifting motor 65 rotates in reverse, enabling the lifting head 7 to move in the return direction (Z2 direction side).

[0029] like Figure 1 As shown, the lifting head 7 includes: a main shaft housing 71 mounted on the front surface of the slider 62; a cylindrical main shaft 72 rotatably supported inside the main shaft housing 71 by bearings (not shown); and a tap chuck 73 mounted on the main shaft 72. At the upper end and both sides of the main shaft housing 71, counterweights 75 for weight offset are connected via wires 74. The wires 74 are mounted on pulleys 76, 76 located at the upper end of the upper support platform 5, and connect the counterweights 75 housed within the upper support platform 5 to the main shaft housing 71.

[0030] The upper end of the spindle 72 protrudes upward from the upper end of the spindle housing 71, and the lower end of the spindle 72 protrudes downward from the lower end of the spindle housing 71. A rotary drive device 8 for rotating the machining tool 100 is connected to the upper end of the spindle 72. The rotary drive device 8 includes: a reducer 82 mounted on a support plate 81 extending forward (X1 direction side) from the upper end of the spindle housing 71; a rotary drive motor 83 mounted on the reducer 82; and a belt drive device 84 for transmitting power from the reducer 82 to the upper end of the spindle 72. Therefore, by operating the rotary drive motor 83 according to the command from the control device 9, the spindle 72 can be rotated about the rotation center axis AR.

[0031] Although the direction was omitted Figure 1 The diagram shows a tapered sleeve at the lower end of the spindle 72 with an opening facing downwards, and a tapered shank of a tap chuck 73 is mounted thereon. The upper end of the machining tool 100 is held by the tap chuck 73, and the machining tool 100 is mounted on the tap chuck 73 with the axis AX1 aligned with the rotational axis AR. Then, according to instructions from the control device 9, the machining tool 100 is rotated around the rotational axis AR by the rotary drive motor 83, and reciprocated along the vertical direction Z by the lifting motor 65, i.e., Z-axis movement. By rotating the machining tool 100 around the rotational axis AR while reciprocating along the vertical direction Z, abrasive grains attached to the outer surface of the machining tool 100 by electrodeposition or bonding are used to grind the thread groove 201 of the nut 200. This allows for the finishing grinding of the nut 200. Furthermore, during the grinding and finishing process, as explained below, the nut 200 can be adjusted in position to mimic the outer surface of the machining tool 100 so that the axis AX2 of the nut 200 (refer to...) Figure 2 , Figure 6 The rotation center axis AR (axis AX1 of machining tool 100) is aligned with the rotation center axis. On the other hand, before and after grinding and finishing, the nut 200 is held in a predetermined initial position by the grinding fixture 2. (See reference...) Figure 2 , Figure 4A and Figure 4B The structure and operation of the grinding fixture 2 that holds the nut 200 will be explained.

[0032] Figure 4A and Figure 4B yes Figure 2 A partial sectional view of the grinding fixture shown. Figure 4A The diagram schematically illustrates the movement of the grinding fixture 2 during the grinding and finishing process. Figure 4B The diagram schematically illustrates the movement of the grinding fixture 2 before and after the grinding and finishing process. For example... Figure 2 , Figure 4A and Figure 4B As shown, the grinding fixture 2 includes: a fixture base 21, which is fixedly disposed on the upper surface of the worktable 42 along the extension line of the rotation center axis AR of the machining tool 100; and a contour holding part 22, which, as will be described in detail later, holds the nut 200 while changing the posture of the nut 200 relative to the fixture base 21 in accordance with the shape of the outer side of the machining tool 100.

[0033] The clamp base 21 is a frame with a border shape when viewed from above (Z2 direction side), and the nut 200 is held in the nut holding member 23 in its central space. In this embodiment, the nut holding member 23 has a clamping table 231 and a support frame 232, and the clamping table 231 holding the nut 200 is supported by the support frame 232 in a horizontally enclosed state. Furthermore, in order to adjust the posture of the nut 200 by displacing the nut holding member 23, the contour holding part 22 is configured to have both a tilt adjustment function to adjust the tilt posture of the nut 200 relative to the rotation center axis AR and a horizontal adjustment function to adjust the horizontal position of the nut 200 relative to the rotation center axis AR.

[0034] The contour-following retaining part 22 has a universal joint mechanism 24 consisting of a movable frame 240, a first swing support 241, and a second swing support 242. More specifically, the movable frame 240 is a frame with the same border shape as the clamp base 21, configured to horizontally surround the nut retaining member 23 in the central space of the clamp base 21. The first swing support 241 is provided at two separate locations in the Y direction between the movable frame 240 and the clamp base 21. Figure 4A and Figure 4B As shown, both swing shafts 241 have an inner bushing 241a, a sliding shaft 241b, and a connecting pin 241c, and are symmetrically arranged with respect to the nut 200 held by the nut retaining member 23. Therefore, the structure of the first swing shaft 241 on the Y2 direction side will be described here, and the description of the Y1 direction side will be omitted.

[0035] In the sidewall of the clamp base 21 on the Y2 direction side, a through hole is provided at approximately the center position in the X direction along the Y direction, and a cylindrical inner bushing 241a is inserted into the through hole along the Y direction. A sliding shaft 241b is slidably inserted into the hollow portion of the inner bushing 241a relative to the inner bushing 241a along the Y direction. The sliding shaft 241b has a through hole in the Y direction. A connecting pin 241c is inserted into the through hole from the Y2 direction side toward the Y1 direction side, and its front end is connected to the sidewall of the movable frame 240 on the Y2 direction side. Additionally, a first swing support shaft 241 is also provided on the Y1 direction side in the same manner as on the Y2 direction side. Therefore, through these two first swinging pivots 241, the movable frame 240 can swing freely relative to the clamp base 21 in the Y direction, and the movable frame 240, the sliding shaft 241b and the connecting pin 241c can slide freely along the Y direction as a whole.

[0036] Furthermore, between the movable frame 240 and the nut retaining member 23, the second swing support shaft 242 is disposed at two locations separated in the X direction. For example... Figure 4A and Figure 4B As shown, both swing shafts 242 have an inner bushing 242a, a sliding shaft 242b, and a connecting pin 242c, and are symmetrically arranged with respect to the nut 200 held by the nut retaining member 23. Therefore, the structure of the second swing shaft 242 on the X2 direction side will be described here, and the description of the X1 direction side will be omitted.

[0037] In the sidewall of the movable frame 240 on the X2 direction side, a through hole is provided at approximately the center position in the Y direction along the X direction, and a cylindrical inner bushing 242a is inserted into this through hole along the X direction. A sliding shaft 242b is slidably inserted into the hollow portion of the inner bushing 242a relative to the inner bushing 242a along the X direction. A connecting pin 242c is inserted into the through hole in the sliding shaft 242b along the X direction, extending from the X2 direction side towards the X1 direction side, and its front end is connected to the sidewall of the support frame 232 on the X2 direction side. Furthermore, a second swing support shaft 242 is also provided on the X1 direction side in the same manner as on the X2 direction side. Therefore, through these two second swing support shafts 242, the support frame 232 can swing freely about the X direction relative to the movable frame 240, and the support frame 232, the sliding shaft 242b, and the connecting pin 242c slide freely together along the X direction.

[0038] Thus, in this embodiment, by providing the universal joint mechanism 24, the tilting posture of the nut 200 can be changed by tilting the nut holding member 23 relative to the rotation center axis AR. Furthermore, the first swing support shaft 241 and the second swing support shaft 242 respectively have sliding bearing structures in the Y and X directions, functioning as the "moving mechanism" of the present invention, enabling the nut holding member 23 to move along the Y and X directions. That is, the horizontal position of the nut 200 relative to the rotation center axis AR can be changed by the moving mechanism. Therefore, as... Figure 4A As shown, when the movable frame 240 and the support frame 232 are free to move, during the grinding process where the outer surface of the machining tool 100 slides into contact with the threaded groove 201 of the nut 200 to perform grinding finishing, the nut 200 tilts or moves horizontally in accordance with the outer surface of the machining tool 100. Therefore, as explained later... Figure 6 As shown, the posture of the nut 200 can be adjusted so that the axis AX2 of the nut 200 is aligned with the rotation center axis AR (the axis AX1 of the machining tool 100). Furthermore, in this specification, this mode, which allows the posture of the nut 200 to be changed in accordance with the machining tool 100, is referred to as the "contour setting mode".

[0039] Here, if only the grinding and finishing process is considered, it is also considered that the grinding fixture 2 is always set to the contour setting mode. However, if the workability when installing the nut 200 on the grinding fixture 2, the phase assurance when inserting the machining tool 100 into the threaded groove 201 of the nut 200 to perform the grinding and finishing process, and the workability when removing the nut 200 after the grinding and finishing process are considered, it is preferable to position the nut 200 in an initial position suitable for phase assurance, etc., before and after the grinding and finishing process, and to restrict the displacement of the nut 200 from that initial position. Therefore, in this embodiment, in addition to the contour setting mode described above, an "initial setting mode" is provided in which the nut 200 is positioned in an initial position and the displacement from the initial position is restricted, and a mode switching mechanism 25 for switching these modes is provided.

[0040] The mode switching mechanism 25 includes: a cylinder 251 for positioning and fixing the nut 200 in the initial position in the X direction; and a cylinder 252 for positioning and fixing the nut 200 in the initial position in the Y direction. Corresponding to the piston portion 251p of the cylinder 251, through holes 211, 2401 and recesses 2321 are respectively provided on the walls of the fixture base 21, the movable frame 240 and the support frame 232 in the Y1 direction, and they are arranged in a straight line in the Y direction when the nut 200 is in the initial position. Therefore, even if the movable frame 240 and the support frame 232 are displaced relative to the fixture base 21 in the X direction in accordance with the machining tool 100, the piston portion 251p of the cylinder 251 extends in the Y2 direction according to the command from the control device 9, thereby returning the movable frame 240 and the support frame 232 to the initial position in the X direction. That is, through the entry of the piston portion 251p into the through holes 211, 2401 and the recess 2321, the clamp base 21, the movable frame 240 and the support frame 232 are pierced by the piston portion 251p along the Y direction, and in this process... Figure 4A The state transition shown Figure 4B As shown, the nut 200 is positioned in the initial position in the X direction.

[0041] Furthermore, the positioning in the Y direction is the same as in the X direction. That is, corresponding to the piston portion 252p of the cylinder 252, the through hole 212 and the recess 2402 are respectively provided on the wall portion of the fixture base 21 and the movable frame 240 in the X2 direction. When the nut 200 is in the initial position, they are arranged in a straight line in the X direction. Therefore, even if the movable frame 240 and the support frame 232 are displaced relative to the fixture base 21 in the Y direction in accordance with the machining tool 100, the piston portion 252p of the cylinder 252 extends in the X1 direction according to the command from the control device 9, thereby returning the movable frame 240 and the support frame 232 to the initial position in the Y direction. That is, through the entry of the piston portion 252p into the through hole 212 and the recess 2402, the fixture base 21 and the movable frame 240 are pierced by the piston portion 252p in the X direction, and in this process... Figure 4A The state transition shown Figure 4B As shown, the nut 200 is positioned in the initial position in the Y direction.

[0042] Thus, through the extension action of cylinders 251 and 252, such as Figure 4B As shown, pistons 251p and 252p enter, thereby positioning the nut retaining member 23 in its initial position in the horizontal direction. Therefore, by design, the nut 200 is held in the nut retaining member 23 at its axis ( Figure 2 , Figure 6The reference numeral AX2) is aligned with the rotation center axis AR of the machining tool 100 within a certain range. Simultaneously with this positioning action, the horizontal movement and tilting of the nut 200 relative to the rotation center axis AR are restricted at this position, i.e., the universal joint mechanism 24 is locked (initial setting mode).

[0043] Conversely, through the contraction action of cylinders 251 and 252, such as Figure 4A As shown, pistons 251p and 252p retract toward the through holes 211 and 212 of the fixture base 21, respectively, and the locking of the universal joint mechanism 24 is released. In this state, when the machining tool 100 is inserted into the threaded groove 201 of the nut 200 and reciprocates for grinding and finishing, the nut 200 conforms to the machining tool 100 and moves horizontally and tilts relative to the rotation center axis AR. With the axis AX2 of the nut 200 aligned with the rotation center axis AR (axis AX1 of the machining tool 100), the outer surface of the machining tool 100 appropriately slides into contact with the threaded groove 201 (contouring setting mode). Furthermore, with the reciprocating motion of the machining tool 100, the threaded groove 201 is effectively ground by the abrasive grains attached to the outer surface of the machining tool 100.

[0044] A control device 9 is provided to control the grinding apparatus 1 configured as described above. This control device 9 includes an arithmetic processing unit 91 composed of a CPU (Central Processing Unit). A storage unit 92, a motor control unit 93, a cylinder control unit 94, an external input / output unit 95, a display unit 96, and an input unit 97 are connected to the arithmetic processing unit 91. Furthermore, the arithmetic processing unit 91 controls each part of the device to perform the grinding and finishing process according to a program pre-stored in the storage unit 92.

[0045] The motor control unit 93 drives the lifting motor (Z-axis motor) 65 to raise and lower the machining tool 100, and drives the rotation drive motor (R-axis motor) 83 to rotate the machining tool 100 around the rotation center axis AR. Furthermore, the motor control unit 93 provides the current values ​​of the driving control motors 65 and 83 as information related to the motor torque to the arithmetic processing unit 91. Therefore, the arithmetic processing unit 91 can detect with high precision whether the rotation of the machining tool 100 is abnormal based on this information.

[0046] The cylinder control unit 94 controls the compressed air supplied to the cylinders 251 and 252 to extend and retract the pistons 251p and 252p, thereby switching between the initial setting mode and the contour setting mode.

[0047] The external input / output unit 95 is a so-called interface, configured to receive detection signals output from various sensor types 951 provided on the grinding apparatus 1. These detection signals include signals from proximity sensors 951a that detect the position of the tap chuck 73, and the arithmetic processing unit 91 can detect whether the tap chuck 73 has any floating abnormality based on these signals.

[0048] The display unit 96 consists of a liquid crystal display device or the like, which displays the status of the grinding device 1 on the screen. The input unit 97 consists of a keyboard or the like, which receives input from the outside through manual operation by the operator.

[0049] In the grinding apparatus 1 configured as described above, the program stored in the storage unit 92 is read out to the arithmetic processing unit 91, which controls each part of the apparatus to perform the grinding and finishing of the nut 200 in the following manner. Hereinafter, refer to... Figure 4A , Figure 4B , Figure 5 and Figure 6 The grinding and finishing process using grinding device 1 will be explained.

[0050] Figure 5 It means to utilize Figure 1 A flowchart illustrating the grinding and finishing steps performed by the shown grinding apparatus. Additionally, Figure 6 It is a schematic representation of the use Figure 1 The diagram illustrates the grinding and finishing steps performed by the grinding apparatus shown. Furthermore, the hollow arrows in columns (a), (b), and (d) of this diagram indicate the locking state of the universal joint mechanism 24 due to the extension action of cylinders 251 and 252. The dashed line in column (c) of this diagram indicates the release of the locking of the universal joint mechanism 24 due to the retraction action of cylinders 251 and 252, thereby allowing the nut 200 to move freely horizontally and tilt relative to the rotation center axis AR.

[0051] With one end face 202 of the nut 200 (before grinding and finishing) facing the machining tool 100, the operator places the nut 200 in the grinding fixture 2 (an example corresponding to the "first step" of this invention). At this time, all parts of the grinding device 1 are at their origin positions. That is, as shown... Figure 1 As shown, the machining tool 100 mounted on the lifting head 7 is positioned at the origin position P1, which is vertically upward from the grinding jig 2, i.e., in the Z2 direction, when it is stopped rotating. Figure 6 Additionally, in grinding fixture 2, cylinders 251 and 252 extend ( Figure 4B The universal joint mechanism 24 is locked. This prevents the nut retaining member 23 from moving horizontally or tilting relative to the rotation center axis AR, making it easier for the operator to install the nut 200 onto the nut retaining member 23.

[0052] When the nut 200 is set onto the grinding fixture 2, the operator provides a start command for grinding and finishing to the control device 9 via the input unit 97. Upon receiving this signal, the arithmetic processing unit 91 of the control device 9 controls each part of the device to perform the grinding and finishing of the nut 200 in the following manner. First, the lifting motor (Z-axis motor) 65 operates, as follows: Figure 6 As shown in column (a), the machining tool 100 is lowered from the origin position P1 to a position P2 directly above the nut 200 (step S1). The descent of the machining tool 100 is performed at a relatively high speed, while the rotation of the machining tool 100 stops.

[0053] When the descent to position P2 is complete, the lifting motor 65 reduces its speed, switching the descent speed of the machining tool 100 to a low speed. Simultaneously, the rotary drive motor (R-axis motor) 83 operates synchronously with this low-speed descent, initiating the forward rotation of the machining tool 100 (step S2). Here, "forward rotation" means that while the machining tool 100 is descending, the thread groove 201 is ground using abrasive grains attached to the outer surface of the machining tool 100. "Reverse rotation," the opposite of "forward rotation," means that while the machining tool 100 is rising, the thread groove 201 is ground using abrasive grains attached to the outer surface of the machining tool 100.

[0054] Thus, when the machining tool 100 rotates clockwise while descending, as... Figure 6 As shown in column (b), the front end of the machining tool 100 slides along the Z2 direction side of the nut 200 while entering in phase with the thread groove 201. At this time, if the axis AX1 of the machining tool 100 is significantly offset from the axis AX2 of the nut 200, or if the front end of the machining tool 100 is not in phase with the thread groove 201, problems arise such as applying a large torque to the machining tool 100 in the rotational direction (R-axis direction) (abnormal R-axis torque) or the tap chuck 73 connected to the machining tool 100 extending or contracting beyond its expected range (abnormal floating). If the operation is performed under these conditions, it will cause poor grinding and finishing, a short lifespan of the machining tool 100, and device malfunctions. Therefore, in this embodiment, as... Figure 6As shown in column (b), before the machining tool 100 descends to the preset initial insertion position P3 and is inserted into the nut 200 by the initial insertion amount (e.g., about 1 / 3 of the way into the nut 200), the current value of the lifting motor 65 is monitored to detect R-axis torque abnormalities, and the proximity sensor 951a is used to monitor for float abnormalities (steps S3, S4). Here, to detect R-axis torque abnormalities, the torque applied to the machining tool 100 can also be directly measured using a torque sensor. Furthermore, the sensor for detecting float abnormalities is not limited to the proximity sensor 951a; any position detection sensor can be used.

[0055] When at least one of the abnormal R-axis torque and abnormal floating is detected in step S3 above, the control device 9 stops the lifting motor 65 and the rotary drive motor 83, and notifies the display unit 96 that the device has stopped due to the abnormality (step S5). Upon confirming the alarm notification, the operator operates the lifting motor 65 and the rotary drive motor 83 via the input unit 97 to eliminate the abnormality, and returns the device to its origin by returning the machining tool 100 to its origin position P1. Then, when the abnormality is eliminated and preparation for another grinding and finishing attempt is complete, the operator operates the input unit 97 to provide a restart command to the control device 9. Upon receiving this restart command ("Yes" in step S6), the control device 9 returns to step S1 and attempts grinding and finishing again.

[0056] On the other hand, when the initial insertion of the machining tool 100 is completed without any abnormal R-axis torque or floating, ("Yes" in step S4), cylinders 251 and 252 retract. Figure 4A Then the universal joint mechanism 24 is released from its lock (step S7). At this time, if the axis AX2 of the nut 200 held in the nut holding member 23 is aligned with the rotation center axis AR of the machining tool 100, the nut holding member 23 does not move and maintains its position. On the other hand, if they are not aligned, the nut holding member 23 moves horizontally and / or tilts relative to the rotation center axis AR in accordance with the outer surface of the machining tool 100. As a result, the axis AX2 of the nut 200 held in the nut holding member 23 is aligned with the rotation center axis AR of the machining tool 100.

[0057] After the universal joint mechanism 24 is released from locking, the machining tool 100 begins to rotate and reciprocate in the Z direction at a rotational and traversal speed suitable for grinding and finishing (hereinafter referred to as "rotational reciprocating movement of the machining tool 100") (step S8). That is, the machining tool 100 rotates in a clockwise direction while descending in the Z1 direction at a speed suitable for grinding and finishing, thereby causing the central region 101 in the Z direction of the outer surface of the machining tool 100 to ( Figure 6 The central region 101 (column (c)) is in sliding contact with the thread groove 201, and the thread groove 201 is ground using abrasive grains attached to it. Conversely, the machining tool 100 rotates in reverse and rises in the Z2 direction, thereby causing the central region 101 to slide into contact with the thread groove 201, and the thread groove 201 is ground using abrasive grains attached to it. Thus, as the machining tool 100 moves back and forth in both directions, the thread groove 201 of the nut 200 moves horizontally and tilts appropriately relative to the rotation center axis AR, mimicking the outer surface of the machining tool 100, and finishing grinding is performed when the axis AX2 of the nut 200 is aligned with the rotation center axis AR of the machining tool 100 (an example of the "second step" of the present invention).

[0058] Thus, during the grinding and finishing process, an R-axis torque abnormality may occur. Therefore, in this embodiment, during the period when the number of reciprocating movements is repeated to a value pre-instructed by the operator, the processing unit 91 monitors the occurrence of the R-axis torque abnormality based on the current value of the lifting motor 65 (steps S9 and S10). Furthermore, when an R-axis torque abnormality occurs ("Yes" in step S9), the processing unit 91 temporarily stops the driving of the lifting motor 65 and the rotary drive motor 83, interrupting the reciprocating movement of the machining tool 100, and then reverses the drive by a certain amount at a low speed. For example, if an R-axis torque abnormality occurs when the machining tool 100 is descending in the Z1 direction while rotating clockwise, the machining tool 100 is reversed a certain amount while rising in the Z2 direction. On the other hand, if an R-axis torque abnormality occurs when the machining tool 100 is rising in the Z2 direction while reversing the drive, the machining tool 100 is descending in the Z1 direction while rotating clockwise a certain amount. Afterwards, the process returns to step S8, and the reciprocating movement of the machining tool 100 is restarted.

[0059] When the number of reciprocating rotations of the aforementioned machining tool 100 reaches a specified value, completing the grinding and finishing of the nut 200 ("Yes" in step S10), the machining tool 100 reverses direction and rises in the Z2 direction. After returning to the origin position P1 (step S12), the rotation and movement of the machining tool 100 stop. Additionally, in the grinding fixture 2, cylinders 251 and 252 extend ( Figure 4B ), and lock the universal joint mechanism 24. In this way, a series of processes for a nut 200 are completed.

[0060] As described above, in this embodiment, the nut holding member 23 is moved horizontally and tilted relative to the rotation center axis AR, mimicking the central region 101 (corresponding to the "machining region" of the present invention) on the outer surface of the machining tool 100 where the thread groove 201 is ground. Therefore, during the grinding and finishing process, the posture of the nut 200 is adjusted so that the axis AX2 of the nut 200 is aligned with the rotation center axis AR of the machining tool 100. Thus, the thread groove 201 can be ground while the axis of the machining tool 100 is aligned with the axis of the nut 200, thereby enabling high-precision grinding and finishing of the nut 200 by the machining tool 100.

[0061] Furthermore, since the grinding and finishing process is performed with the axis AX1 of the machining tool 100 aligned with the axis AX2 of the nut 200, it is possible to prevent the application of excessive external forces, such as bending stress, to the machining tool 100 during the grinding and finishing process, thereby extending the life of the machining tool 100.

[0062] Furthermore, when the nut 200 is placed in the grinding fixture 2, the mode switching mechanism 25 switches to the initial setting mode. That is, the universal joint mechanism 24 is locked to position the nut 200 held in the nut holding member 23 in the initial position. In this state, the nut 200 can be stably placed in the grinding fixture 2.

[0063] Furthermore, before performing grinding and finishing by rotating the machining tool 100, the front end of the machining tool 100 needs to be inserted into the nut 200 while aligning the phase with the thread groove 201. However, in this embodiment, the initial insertion is performed while maintaining the initial setting mode. Therefore, the initial insertion can be performed stably while limiting the displacement of the nut 200.

[0064] Furthermore, after the grinding and finishing process is completed, the mode switching mechanism 25 returns the modeling setting mode to the initial setting mode. Therefore, the nut 200, after grinding and finishing, can be stably removed from the grinding fixture 2.

[0065] In the above embodiments, the rotation center shaft AR corresponds to an example of the "rotation center shaft extending along the first direction" of the present invention. Furthermore, the combination of the lifting device 6 and the rotation drive device 8 functions as the "tool drive unit" of the present invention. Additionally, the Z2 direction side end face 202 of the nut 200 corresponds to an example of the "one end face of the ball screw nut" of the present invention, and the Z1 direction side end face 203 of the nut 200 corresponds to an example of the "other end face of the ball screw nut" of the present invention.

[0066] Furthermore, the present invention is not limited to the above-described embodiments. Various modifications can be made to the embodiments without departing from their spirit. For example, in the above embodiments, grinding and finishing are performed only when one end face 202 of the nut 200 faces the machining tool 100, performing a specified number of reciprocating rotations, such as 2N times. However, similar to the first embodiment, after grinding and finishing, the grinding fixture 2 can be flipped up and down, for example... Figure 7 As shown, grinding and finishing are performed with the other end face 203 of the nut 200 facing the machining tool 100 (second embodiment). By performing grinding and finishing in two different ways, the finishing accuracy can be further improved. Furthermore, regarding the number of rotational reciprocating movements in the second embodiment, it can be configured such that N times are performed with one end face 202 of the nut 200 facing the machining tool 100, and N times are performed with the other end face 203 of the nut 200 facing the machining tool 100.

[0067] Furthermore, in the above embodiment, in addition to the tilting function of tilting the nut retaining member 23 relative to the rotation center axis AR to change the tilting posture of the nut 200, the contour retaining member 22 also has a moving function of moving the nut retaining member 23 along the Y and X directions to change the horizontal posture of the nut 200 by horizontal displacement relative to the rotation center axis AR. As a variation, only a moving mechanism for moving the nut retaining member 23 along the X direction may be added, or conversely, only a moving mechanism for moving the nut retaining member 23 along the Y direction may be added.

[0068] Alternatively, the contour retaining part 22 may be configured to have only the function of moving the nut retaining part 23 along the Y and X directions to change the horizontal posture of the nut 200 by causing it to be horizontally displaced relative to the rotation center axis AR.

[0069] Furthermore, in the above embodiments, the mutually orthogonal Z-direction, Y-direction, and X-direction are designated as the "first direction," "second direction," and "third direction" of the present invention. However, the Y-direction or X-direction can also be designated as the "first direction," and the remaining two directions can be designated as the "second direction" and "third direction," respectively. Additionally, the mutual orthogonality of the "first direction," "second direction," and "third direction" of the present invention is not mandatory; they can also be designated as intersecting.

[0070] Industrial availability

[0071] This invention can be applied to all grinding techniques that use forming tools to grind the thread grooves of ball screw nuts for finishing.

[0072] Label Explanation

[0073] 1…grinding device

[0074] 2… Grinding fixture

[0075] 6… Lifting device (tool drive unit)

[0076] 8… Rotary drive unit (tool drive unit)

[0077] 21… Fixture base

[0078] 22… Contouring and retaining section

[0079] 23…Nut retaining component

[0080] 24… Universal joint mechanism

[0081] 25…Mode switching mechanism

[0082] 100… (forming) machining tools

[0083] 101…Central Area (Processing Area)

[0084] 200… (ball screw) nut

[0085] 201… Threaded groove

[0086] 202… (one) end face

[0087] 203… (another) end face

[0088] 240… movable frame

[0089] 241…First swing support shaft

[0090] 242…Second swing support shaft

[0091] AR… Rotation Center Axis

[0092] AX1… (Machining tool) axis

[0093] AX2… (the axis of the ball screw nut)

[0094] X… Horizontal direction (third direction)

[0095] Y…left and right directions (second direction)

[0096] Z… Vertical direction (first direction)

Claims

1. A grinding fixture for holding a ball screw nut that is being finished by grinding its thread grooves using a forming tool, the forming tool rotating about a rotational central axis extending in a first direction while reciprocating along the first direction, the grinding fixture being characterized by comprising: A clamp base is fixedly mounted on the central axis of rotation; and The conformal retaining part, mounted on the fixture base, changes the posture of the ball screw nut relative to the fixture base while mimicking the machining area on the outer surface of the forming tool that slides in contact with the thread groove to grind the thread groove, thus retaining the ball screw nut. The conformal retaining part includes: a nut retaining component for retaining the ball screw nut; and a universal joint mechanism for causing the nut retaining component to oscillate about a second direction intersecting the first direction and about a third direction intersecting both the first and second directions, thereby changing the inclination of the ball screw nut relative to the rotation center axis. The universal joint mechanism has: Movable frame; The first swing support shaft, with two separate portions in the second direction, is directly disposed between the clamp base and the movable frame, and supports the movable frame relative to the clamp base in a manner that allows it to swing freely about the second direction; and The second swing support shaft is directly disposed between the movable frame and the nut retaining component at the two points that separate in the third direction, and supports the nut retaining component relative to the movable frame in a manner that allows it to swing freely about the third direction. The first direction is the vertical direction. The movable frame is a frame body configured to horizontally surround the nut retaining component. The first swing support has a sliding bearing configuration that allows the movable frame to slide freely relative to the clamp base in the second direction. The second swing support has a sliding bearing configuration that allows the nut retaining member to slide freely relative to the movable frame in the third direction.

2. The grinding fixture according to claim 1, wherein, The first swing support shaft is integrally and slidably disposed relative to the clamp base in the second direction with respect to the movable frame.

3. The grinding fixture according to claim 1 or 2, wherein, The second swing support shaft is integrally disposed with the nut retaining component and is slidably mounted on the third side relative to the movable frame.

4. The grinding fixture according to claim 1 or 2, wherein, The second direction is a direction orthogonal to the first direction. The third direction is a direction orthogonal to the first direction and the second direction.

5. The grinding fixture according to claim 3, wherein, The second direction is a direction orthogonal to the first direction. The third direction is a direction orthogonal to the first direction and the second direction.

6. The grinding fixture according to claim 1 or 2, wherein, The grinding fixture also has a mode switching mechanism that switches between an initial setting mode and a contour setting mode. The initial setting mode is a mode in which the ball screw nut held in the contour holding part is positioned relative to the fixture base at a preset initial position and the displacement of the ball screw nut is restricted. The contour setting mode is a mode in which the displacement restriction of the ball screw nut is lifted and the posture of the ball screw nut is allowed to change.

7. The grinding fixture according to claim 3, wherein, The grinding fixture also has a mode switching mechanism that switches between an initial setting mode and a contour setting mode. The initial setting mode is a mode in which the ball screw nut held in the contour holding part is positioned relative to the fixture base at a preset initial position and the displacement of the ball screw nut is restricted. The contour setting mode is a mode in which the displacement restriction of the ball screw nut is lifted and the posture of the ball screw nut is allowed to change.

8. The grinding fixture according to claim 4, wherein, The grinding fixture also has a mode switching mechanism that switches between an initial setting mode and a contour setting mode. The initial setting mode is a mode in which the ball screw nut held in the contour holding part is positioned relative to the fixture base at a preset initial position and the displacement of the ball screw nut is restricted. The contour setting mode is a mode in which the displacement restriction of the ball screw nut is lifted and the posture of the ball screw nut is allowed to change.

9. The grinding fixture according to claim 5, wherein, The grinding fixture also has a mode switching mechanism that switches between an initial setting mode and a contour setting mode. The initial setting mode is a mode in which the ball screw nut held in the contour holding part is positioned relative to the fixture base at a preset initial position and the displacement of the ball screw nut is restricted. The contour setting mode is a mode in which the displacement restriction of the ball screw nut is lifted and the posture of the ball screw nut is allowed to change.

10. A grinding apparatus for grinding and finishing a ball screw nut by using a forming tool having a shaft structure extending in a first direction to grind the thread groove, characterized in that, have: The grinding fixture according to any one of claims 1 to 9; and The tool drive unit rotates the forming tool about a rotation center axis extending along the first direction while simultaneously moving the forming tool back and forth along the first direction relative to the ball screw nut held in the grinding fixture.

11. A grinding method comprising grinding and finishing a ball screw nut by grinding the thread groove using a forming tool having a shaft structure extending in a first direction, characterized in that, Include: The first step involves holding the ball screw nut using the grinding fixture described in any one of claims 1 to 9; and In the second step, the forming tool is rotated about a rotation center axis extending along the first direction, while the forming tool is reciprocated relative to the ball screw nut held in the grinding fixture along the first direction.

12. The grinding method according to claim 11, wherein, The first step is to hold the ball screw nut with one end face facing the forming tool in the first direction. The second process includes: The process of reciprocating the forming tool with one end face of the ball screw nut facing the forming tool; The process of rotating the grinding fixture so that the other end face of the ball screw nut in the first direction faces the forming tool to position the grinding fixture; and The process of reciprocating the forming tool with the other end face of the ball screw nut facing the forming tool.

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