JP2010099802A - Rest device for thread groove grinder and thread groove grinder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rest device for a thread groove grinder and the rest device to ensure high toughness against multidirectional forces and satisfactorily maintain a machined surface of a machine thread groove. <P>SOLUTION: In the rest device 15 to support a screw shaft W as a workpiece by a rest shoe in order to prevent distortion due to grinding resistance during grinding of the thread groove by a grinding wheel G, the rest shoe has a lower rest shoe 45 to apply from below a helical groove surface Ws of the screw shaft, and a rear rest shoe 46 to apply it from the opposite side of the grinding wheel G. A rest shoe advance-retract mechanism 59 causing these rest shoes to follow the shape of the abutting helical groove surface Ws and advance/retract in directions in which they come in contact with and depart from the helical groove surface Ws, and a rest shoe fixing mechanism 60 to fix these rest shoes at a position where they make contact with the helical groove surface, are disposed in each of the lower rest shoe 45 and the rear rest shoe 46. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a rest device for preventing a workpiece from being shaken or bent due to a machining resistance in grinding a thread groove, and a grinding device provided with such a rest device.

Conventionally, when grinding a thread groove of a long workpiece such as a ball screw, the workpiece is shaken or bent due to the machining resistance and its own weight only by supporting both ends of the workpiece at the center. In order to prevent such deflection and deflection, for example, there is an invention of Patent Document 1. According to this, a pair of end support members (a tailstock and a headstock) that support the centers of both ends of a long workpiece having a thread groove on the outer periphery, and a thread groove of a long workpiece supported by the end support member And a rest device that supports the curved surface of the thread groove so as to face the grinding wheel. Thus, by making the position supported by the rest device facing the grindstone constant, it is possible to prevent the bending of the workpiece from changing with respect to the grindstone depending on the support position of the rest device. In addition, by supporting the processed thread groove with the rest device, it is possible to save the trouble of pre-processing the surface that receives the rest device, and the thread groove is accurate to the workpiece external surface (surface that receives the rest device) before processing. It is possible to prevent the processing from being affected.
JP-A-9-323217

  However, in Patent Document 1, since the thread groove is supported at one point facing the grinding wheel, the rigidity as a rest device against multidirectional forces due to machining resistance and workpiece weight that fluctuate complicatedly with thread grinding. However, there was a risk that it would not function as a steady rest. Further, since the surface of the thread groove ball on which the ball rolls is supported by the rest device, there is a risk that the processed surface of the thread groove processed with high accuracy may be roughened.

  In order to solve the above-mentioned problems, the present invention has an object to provide a thread groove grinding rest device that secures high rigidity against multidirectional forces and maintains a machined surface of the machined thread groove, and the rest device. A grinding device is provided.

  In order to solve the above-mentioned problem, the structural feature of the invention according to claim 1 is that the screw shaft, which is a workpiece, is used as a rest shoe to prevent bending due to grinding resistance when the thread groove is ground with a grindstone. In the supporting rest device, the rest shoe includes a lower rest shoe that contacts the spiral groove surface of the screw shaft from below and a rear rest shoe that contacts from the opposite side of the grindstone, and the lower rest shoe and the rear rest The shoe has a rest shoe advancing / retreating mechanism that moves these rest shoes in a direction to contact and separate from the spiral groove surface following the shape of the contacting spiral groove surface, and each of the rest shoes to contact the spiral groove surface. And a rest shoe fixing mechanism for fixing at each position.

  The structural feature of the invention according to claim 2 is that, in claim 1, the lower rest shoe and the rear rest shoe are provided with a lead angle adjusting device that follows the lead angle of the threaded portion of the screw shaft. That is.

  The structural feature of the invention according to claim 3 is that in claim 1 or 2, when the screw shaft is a ball screw shaft used for a ball screw, the lower rest shoe and the rear rest shoe are It is arrange | positioned so that it may contact | abut to parts other than the ball rolling surface of the spiral groove surface ground with the grindstone.

  The structural feature of the invention according to claim 4 is that, in any one of claims 1 to 3, the rest device for a thread groove grinding device is provided on a grindstone table for supporting the grindstone, and the grindstone is worn. The position adjustment mechanism which adjusts the relative position with respect to the said grindstone of the said lower rest shoe and the said back rest shoe is accompanied with reducing an outer diameter by.

  The structural features of the invention according to claim 5 are: a workpiece support device that rotatably supports a screw shaft having a screw shaft formed in a spiral shape; and a rotational drive of the screw shaft supported by the workpiece support device. A screw shaft rotation drive device that rotates, a grindstone table that rotatably supports a grindstone that grinds the spiral groove surface of the screw groove, and the grindstone table relative to the workpiece support device in the axial direction of the screw shaft. An axial movement device for movement, a radial movement device for moving the wheel head relative to the workpiece support device in the radial direction of the screw shaft, and the wheel head in synchronization with the rotation of the screw shaft. In the thread groove grinding apparatus comprising the screw shaft rotation driving device and the synchronous operation device that operates the axial movement device so as to move relative to each other in the axial direction of the screw shaft, the grindstone table includes the grindstone table. Along with this, it can move in the axial direction of the screw shaft Rest device according to claims 1 to 4 is that are provided.

  According to the first aspect of the present invention, when the rest shoe is inserted into the screw groove, the rest shoe advance / retreat mechanism is operated, and the lower rest shoe and the rear rest shoe are brought into contact with the spiral groove surface of the screw shaft, respectively. Follow the groove surface outline. Then, the rest shoe fixing mechanism is operated, and the screw shaft is ground while maintaining the position following the outer shape of the spiral groove surface. Thus, since it supports from two directions below and back, it can respond with strong rigidity to the multidirectional force by the processing resistance which fluctuates complicated with thread grinding processing, or the dead weight of a work. Also, when supporting from two directions in this way, the outer diameter of the workpiece to be supported and the depth of the groove are different, so it is difficult to support the two rest shoes in contact with each other at an optimal position. There is. However, in the present invention, even if there is a difference in the outer diameter of the spiral groove surface of the screw shaft and the depth of the groove, the rest shoe is actually brought into contact from below and rearward to make it follow, so that the optimum position can be obtained. The rest shoe can be easily arranged and supported, and the processing accuracy of the screw shaft can be greatly improved by effectively preventing run-out and bending during grinding. Further, since the rest shoe is received by the spiral groove surface of the screw shaft, it is possible to save the labor for pre-processing the rest receiving surface and to reduce the production cost.

  According to the second aspect of the present invention, even when a plurality of types of screw shafts are ground, the lower rest shoe and the rear rest are made to follow the lead angle of the threaded portion by the lead angle adjusting device for each screw shaft to be ground. Since it is possible to adjust the shoe, these two rest shoes can be easily adjusted and supported at an optimal position without requiring a lot of setup time.

  According to the invention of claim 3, the rest shoe abuts the ball screw shaft at a portion other than the ball rolling surface of the spiral groove surface ground by the grindstone, so that the ball rolling surface is brought into contact with the rest shoe. It can be ground with high accuracy without scratching.

  According to the invention according to claim 4, when the grindstone is worn by shaping such as use by grinding or dressing / truing and the grindstone outer diameter is reduced, the rest device is provided on the grindstone base, so the grindstone (rotation center) As a result, the relative position between the support surface of the rest shoe and the rest shoe does not change, and the surface where the grindstone should come into contact with the grinding surface of the ball screw shaft and the support surface of the rest shoe are separated. Even in such a case, according to the rest device of the present invention, the relative position of the rest shoe with respect to the grindstone (rotation center) can be adjusted by the position adjusting mechanism, so that it can be continuously supported at the most appropriate position.

  According to the fifth aspect of the present invention, it is possible to support with high rigidity against multi-directional force due to machining resistance and workpiece weight that fluctuate in complex with thread grinding from the lower and rear two directions. In addition, the rest shoe can be placed in contact with the shoe from the bottom and rear to make it follow, so that the rest shoe can be easily placed and supported at the optimum position at all times. Therefore, the processing accuracy of the screw shaft can be dramatically improved.

  Hereinafter, a thread groove grinding device provided with a rest device according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a plan view showing an outline of a thread groove grinding apparatus, and FIG. 2 is a view showing a use state of a rest apparatus provided on a grindstone table. The thread groove grinding device 10 includes a bed 11, a workpiece support device 12 that is placed on the bed 11 and supports the ball screw shaft W so as to be rotationally driven, and an axial direction and a radial direction of the ball screw shaft W on the bed 11. A grindstone base 13 movably mounted on the grindstone, and a grindstone G for grinding a spiral groove surface Ws (see FIG. 8) of a thread groove Wg supported on the grindstone base 13 so as to be rotationally driven and formed on the ball screw shaft W. In order to prevent bending of the ball screw shaft W due to grinding resistance, a rest device 15 that supports the ball screw shaft W with rest shoes 45 and 46 described later is provided.

  The ball screw shaft W is a ball screw shaft used in, for example, a rack coaxial type electric power steering apparatus, and a screw groove Wg having a spiral groove surface Ws on both sides of the groove is formed in a spiral shape. A rack Wr is formed at one end of the ball screw shaft W, and a connecting shaft Wc is formed at the other end. For example, as shown in FIG. 8, the cross-sectional shape of the screw groove Wg is slightly displaced in the axial direction of the ball screw shaft W with respect to the center O1, O2 of both arcs so that the radii R of both arcs intersect each other. Arcs C1 and C2 and escape grooves D that connect both arcs C1 and C2 by escaping in the radial direction at the bottom of the valley of the thread groove Wg. A steel ball B interposed between the ball screw shaft W and a nut (not shown) rolls on the ball rolling surface Wb at the center of the two arcs C1 and C2 forming the spiral groove surfaces Ws on both sides of the groove. Is configured to do.

  As shown in FIG. 1, the workpiece support device 12 includes a headstock 16 and a tailstock 17 which are installed on the bed 11 of the thread groove grinding device 10 at a predetermined distance from each other. A main shaft 19 to which a chuck 18 that holds one end of the ball screw shaft W is attached is rotatably supported. The main shaft 19 is driven to rotate by a servo motor 20.

  The tailstock 17 supports a tailstock shaft 22 to which a tailstock center 21 that supports the other end of the ball screw shaft W is attached so as to be able to advance and retreat in the Z-axis direction. It is supposed to be advanced and retracted by. The ball screw shaft W is supported at the center hole provided at the other end by the tailstock center 21 by the advancement and retraction of the tailstock shaft 22, and one end thereof is gripped by the chuck 18 of the head stock 16. The ball screw shaft W is rotated by the servo motor 20. The main shaft 19, chuck 18, servo motor 20, etc. constitute a screw shaft rotation drive device 24 that rotationally drives the ball screw shaft W supported by the workpiece support device 12.

  On the bed 11, a slide 25 is guided and supported by a pair of linear guides 26 so as to be movable in a direction parallel to the axial direction of the ball screw shaft W (Z-axis direction). The slide 25 is moved in the Z-axis direction by the servo motor 27 via the ball screw 28. A grinding wheel base 13 is mounted on the slide 25 so as to be movable in a horizontal direction (X-axis direction) parallel to the radial direction of the ball screw shaft W by a pair of linear guides 30. 29 in the X-axis direction.

    The slide 25, the linear guide 26, the servo motor 27, the ball screw 28, and the like constitute an axial movement device 32 that moves the grindstone base 13 in the axial direction of the ball screw shaft W with respect to the workpiece support device 12. The linear guide 30, the ball screw 29, the servo motor 31, and the like constitute a radial movement device 33 that moves the grindstone base 13 in the radial direction of the ball screw shaft W with respect to the workpiece support device 12.

  A grindstone shaft 34 is rotatably supported at both ends by a bearing portion 35 provided on the workpiece support device 12 side on the grindstone table 13, and is rotationally driven by a motor 36 via a belt 47. A grindstone G is fixed to the central portion of the grindstone shaft 34 so as to face the ball screw shaft W.

  The rest device 15 is provided side by side with the bearing portion 35 on the front side of the grindstone table 13. As shown in FIG. 2, a rest body 38 is mounted on the front end portion 37 of the grindstone 13 so as to be movable in the vertical direction by a pair of linear guides 39, and a ball screw 49 (see FIG. 2) is attached by a servo motor 40. Moved up and down. That is, a ball screw 49 that is rotationally driven by a servo motor 40 fixed to the upper surface of the rest body 38 is rotatably supported by the rest body 38, and a nut 50 that is screwed into the ball screw 49 is attached to the front end portion of the grindstone base 13. It is fixed. The rest main body 38 is provided with a guide portion 41 extending in the X-axis direction, and an advance / retreat member 42 is mounted on the guide portion 41 so as to be movable in the front-rear direction by a pair of linear guides 51 (see FIG. 2 and FIG. 2). (See FIG. 3). The advance / retreat member 42 is moved back and forth with respect to the ball screw shaft W by the hydraulic cylinder 43. The hydraulic cylinder 43 communicates with a hydraulic pump (not shown), and an electromagnetic valve (not shown) is provided between the hydraulic pump and the hydraulic cylinder 43. The hydraulic cylinder is controlled by a numerical controller 48 that controls opening and closing of the electromagnetic valve. The drive of 43 is controlled. The advance / retreat member 42 and the hydraulic cylinder 43 constitute a position adjusting mechanism. The advancing / retreating member 42 is provided with an L-shaped shoe base 44 having a vertical wall portion 44a and a horizontal wall portion 44b. As shown in FIG. 3, the shoe base 44 is provided so as to be rotatable about the center of the rotation support shaft 52 with respect to the advance / retreat member 42, and a pair of arc holes 53 having a predetermined width. The rotation of the shoe base 44 is stopped and fixed at a predetermined position by a fixing screw 54 loosely fitted to each other. The grindstone G is inclined in accordance with the grinding of the ball screw shaft W, and the rest device 15 attached to the grindstone base 13 is also inclined in the same direction as the grindstone G is inclined. However, the rest device 15 receives the ball screw shaft W from the opposite side of the grindstone G. In order to follow the thread groove Wg of the ball screw shaft W, the rest device 15 needs to be inclined in the reverse direction. Therefore, the angle of the rest device 15 with respect to the grindstone is corrected by inclining in the opposite direction by the rotation support shaft 52, the arc hole 53, and the fixing screw 54.

  Further, a rear rest shoe 46 is provided on the vertical wall portion 44a of the shoe base 44 so as to contact the spiral groove surface Ws from the opposite side of the grindstone G. As shown in FIG. 4, a rotation support projection shaft 55 is formed at the base end portion of the rear rest shoe 46, and a contact portion with the ball screw shaft W with respect to the rotation support projection shaft 55 (a contact portion described later). The contact portions 46a, 46b) are provided at eccentric positions. The rotation support protrusion shaft 55 is supported in a rotation support hole 56 penetrating the vertical wall portion 44a of the shoe base 44 so as to be rotatable around the center O3 of the rotation support protrusion shaft 55. The rotation of the rear rest shoe 46 is restricted to a predetermined range by a fixing screw 58 loosely fitted in a pair of circular arc holes 57 formed above and below the vertical wall portion 44a, and is positioned and fixed at a predetermined position. . Thus, by rotating the contact portions (contact portions 46a and 46b) to the ball screw shaft W within a predetermined range around the center O3 of the rotation support projection shaft 55, the lead angle of the screw groove Wg is imitated. It is supposed to adjust so that.

  Further, as shown in FIG. 5, the rear rest shoe 46 includes an air cylinder mechanism 59 as a rest shoe advancement / retraction mechanism and a stopper mechanism 60 as a rest shoe fixing mechanism. The air cylinder mechanism 59 has a cylinder 62 in which an air supply hole 61 is opened on the distal end side and the proximal end side, and an abutting piston member 63 in which the distal end abuts on the spiral groove surface Ws by moving forward and backward from the cylinder 62. ing. The contact piston member 63 is provided with a flange portion 64 that slides on the inner wall of the cylinder 62 at the outer periphery of the central portion thereof, and the contact piston member 63 advances and retreats on the side surface from the base end portion to the flange portion 64. A single V-shaped groove 65 is formed along the direction in which the line is formed. An air seal 77 is provided on the outer periphery of the collar portion 64. A cylindrical sliding part 66 is formed from the flange part 64 to the tip part, and the sliding part 66 is slidably guided by the sliding guide part 67 of the cylinder 62. The tip of the contact piston member 63 (contact portions 46a and 46b) is formed of a wear-resistant material and supports the workpiece W by contacting the spiral groove surface Ws (see FIG. 8). ). Air supply holes 61 that open to the distal end side and the proximal end side of the cylinder 62 are opened before and after the flange portion 64, respectively, and communicated with an air pump (not shown). An electromagnetic valve (not shown) controlled by a numerical controller 48 described later is provided between the air pump and the supply hole 61 so that the contact piston member 63 is driven by air pressure. The sliding guide portion 67 is provided with an air seal 68.

  As shown in FIG. 5, the stopper mechanism 60 includes a piston member 69 that advances and retreats at right angles to the advancing and retreating direction of the contact piston member 63. A seal 70 is provided on the outer peripheral portion of the piston member 69 on the main body side, and a seal 78 is provided on a sliding guide portion 79 that slides on the tip end side of the piston member 69. In the cylinder 71 of the stopper mechanism 60, air supply holes 72 are opened before and after the seal 70 on the distal end side and the proximal end side, respectively. These air supply holes 72 communicate with an air pump (not shown). An electromagnetic valve (not shown) controlled by the numerical control device 48 is provided between the air pump and the supply hole 72, and the piston member 69 advances and retreats toward the contact piston member 63 of the air cylinder mechanism 59 by air pressure. It is like that. The tip of the piston member 69 is brought into contact with the V groove 65 of the contact piston member 63 to stop the movement of the contact piston member 63. The rear rest shoe 46 is moved forward by the air cylinder mechanism 59 and abutting piston member 63 abutting against the spiral groove surface Ws is fixed and maintained at the abutting position by the stopper mechanism 60, whereby the ball screw shaft W is supported at an optimum position.

  Further, as shown in FIG. 9, the rear rest shoe 46 is screwed from a position where the grindstone G abuts so as to abut on a portion other than the ball rolling surface Wb in the spiral groove surface Ws ground by the grindstone G. For example, the groove Wg is disposed opposite to the grindstone G at a position where the groove is shifted by 2 to 3 and the phase is shifted by 180 degrees. The ball screw shaft W with the helical groove surface Ws ground has a ball nut screwed through a steel ball B to constitute a ball screw device. When the ball rolling surface Wb in the spiral groove surface Ws is scratched, the ball rolls on the scratched portion, thereby inducing vibration and generating abnormal noise. In order to prevent the ball rolling surface Wb from being damaged, the both sides of the front end surface of the rear rest shoe 46 are separated from the ball rolling surface Wb to the valley side by both spiral groove surfaces Ws ground by the grindstone G. Abutting portions 46a and 46b that abut each other are formed.

  Further, the lateral wall portion 44b of the shoe base 44 is formed on the spiral groove surface Ws of the screw groove Wg of the ball screw shaft W so as to prevent the ball screw shaft W from being bent by the grinding force acting on the screw groove Wg from the grindstone G. A lower rest shoe 45 that abuts from below is provided. As shown in FIG. 4, a fitting hole 73 is provided at the lower end of the lower rest shoe 45, and contact portions (contact portions 45 a and 45 b described later) are eccentric with respect to the center 04 of the fitting hole 73. It is provided at the position. The lower rest shoe 45 is rotatably supported by a shoe support shaft 74 that protrudes at a right angle from the lateral wall portion 44 b of the shoe base 44 in the fitting hole 73. The lower rest shoe 45 is rotated within a predetermined range by a fixing screw 76 loosely fitted in the arc hole 75 of the vertical wall portion 44a, a fixing screw 77 (see FIG. 3) loosely fitted in the arc hole (not shown), and the like. And is fixed at a predetermined position. Thus, by adjusting the contact portions (contact portions 45a and 45b) to the ball screw shaft W within a predetermined range around the center O4 of the fitting hole 73, adjustment is performed so as to follow the lead angle of the screw groove Wg. It is supposed to be.

  The lower rest shoe 45 is also provided with an air cylinder mechanism 59 and a stopper mechanism 60 similar to the rear rest shoe 46. Since the structure is the same, description is abbreviate | omitted. Further, the lower rest shoe 45 has a thread groove Wg of 2 to 2 from a position where the grindstone G abuts so as to abut on a portion other than the ball rolling surface Wb in the spiral groove surface Ws ground by the grindstone G from below. It is arranged at a position where the three grooves are shifted and the phase is shifted by 90 degrees. As indicated by reference numerals in FIG. 8, both side edge portions of the front end surface of the lower rest shoe 45 are also formed on both spiral groove surfaces Ws ground by the grindstone G so as to be separated from the ball rolling surface Wb toward the valley side. Abutting portions 45a and 45b that abut are formed. The shoe support shaft 74, the fitting hole 73, the arc holes 57 and 75, the fixing screws 58 and 76, the rotation support protrusion shaft 55, the rotation support hole 56, and the like constitute a lead angle adjusting device.

  The numerical controller 48 controls the rotation of the servo motors 20, 27 based on the NC data, the grindstone base 13 is moved in the Z-axis direction in synchronization with the rotation of the main shaft 19, and the grindstone G is a spiral groove surface of the thread groove Wg. Ws is ground helically. The lower and rear rest shoes 45 and 46 of the rest device 15 provided on the grindstone table 13 are also in contact with portions other than the ball rolling surface Wb of the spiral groove surface Ws ground by the grindstone G. It moves in the axial direction of the ball screw shaft W in synchronization with the rotation.

  Next, the operation of the thread groove grinding device provided with the rest device of the above embodiment will be described. First, the workpiece (ball screw shaft) W is gripped by phasing the chuck 18 of the main shaft 19 in the rotational direction, the rear end thereof is supported by the tailstock center 21 of the tailstock 17 and the start button is pushed. The numerical controller 48 executes a thread groove grinding program. The servo motor 27 is rotationally driven by a command from the numerical controller 48, and the slide 25 is moved in the Z-axis direction via the ball screw 28. Then, the grindstone is indexed to the grinding start position facing the starting end of the thread groove Wg of the ball screw shaft W.

  Next, the servomotors 20 and 27 are rotated under the simultaneous two-axis control by the thread creation NC data, and the grindstone base 13 is moved in the axial direction of the ball screw shaft W in synchronization with the rotation of the ball screw shaft W. A thread groove creating motion is performed between the screw shaft W and the grindstone G. At the same time, the servo motor 31 is rotated, the grindstone base 13 is moved to the advance position in the X-axis direction toward the workpiece support device 12, and the grindstone G is cut toward the workpiece (ball screw shaft) W. .

  When the spiral groove surface Ws at the start end portion of the thread groove Wg is ground by the grindstone G, the servo motor 40 and the hydraulic cylinder 43 are driven. In this case, correction is performed to incline the angle of the rest device 15 with respect to the grindstone bed 13 in the reverse direction. Further, the rear rest shoe 46 and the lower rest shoe 45 are rotated in advance around the centers O3 and O4 in accordance with the lead angle of the created thread groove Wg, and fixed and positioned at the rotation positions. The rear rest shoe 46 and the lower rest shoe 45 are maintained in a state in which the respective contact piston members 63 are retracted by the air cylinder mechanism 59. Next, the rest main body 38 is raised and the advance / retreat member 42 is retracted. The air cylinder mechanism 59 is driven to advance the abutting piston members 63 of the lower and rear rest shoes 45, 46, and both spiral groove surfaces in which the abutting portions 45a, 45b and 46a, 46b are ground by the grindstone G. Ws is brought into contact with a portion of the ball rolling surface Wb that is out of the valley. Subsequently, the contact piston member 63 that has advanced by operating the stopper mechanism 60 is fixed, and the contact portions 45a, 45b and 46a, 46b are separated from the ball rolling surface Wb to the valley side on both spiral groove surfaces Ws. The state of contact with is maintained. In this way, the lower and rear rest shoes 45, 46 are moved together with the grindstone table 13 in contact with the portions other than the ball rolling surface Wb of the spiral groove surface Ws ground by the grindstone G. The shaft W is supported and ground by the lower and rear rest shoes 45 and 46 at an axial position close to the grindstone G, so that the ball screw shaft W is prevented from being bent and the thread groove Wg is ground with high accuracy. At this time, since the lower and rear rest shoes 45 and 46 do not contact the ball rolling surface Wb, there is no damage. In addition, since the contact portions 45a, 45b and 46a, 46b provided on both front edge portions of the lower and rear rest shoes 45, 46 are in contact with both spiral groove surfaces Ws ground by the grindstone G, both The force from the spiral groove surface Ws acts on both side edges of the front end of the lower and rear rest shoes 45 and 46 in a balanced manner, and the ball screw shaft W can be supported in a state where the lower and rear rest shoes 45 and 46 are stable. .

  Further, the contact portions 45a, 45b and 46a, 46b of the lower and rear rest shoes 45, 46 are formed on both spiral groove surfaces Ws ground by the grindstone G from the ball rolling surface Wb as shown in FIG. Since the contact is made at the part deviated to the side, the angle formed by the common tangent at the contact portion between the contact portions 45a, 45b and 46a, 46b and both spiral groove surfaces Ws and the axial direction of the ball screw shaft W is reduced. The rest shoes 45 and 46 can slightly escape in the axial direction of the thread groove W with respect to both the spiral groove surfaces Ws, and a minute pitch error or the like can be absorbed during the grinding process.

  Further, the coolant supplied during grinding is sufficiently supplied through the escape groove D between the spiral groove surfaces Ws to the lower side and the front end back surfaces of the rear rest shoes 45 and 46 as the screw shaft Wg rotates. No seizure occurs between the portions 45a, 45b and 46a, 46b and the spiral groove surfaces Ws.

  Next, when the grinding wheel G grinds the screw shaft Wg to the end, the servo motor 31 is rotated in the reverse direction, the grinding wheel base 13 is retracted to the retracted position, and the grinding wheel G is detached from the thread groove Wg. Further, the servo motor 40 and the hydraulic cylinder 43 are driven in reverse to move the rest main body 38 and the advance / retreat member 42 to the disengagement position, and the contact portions 45a, 45b and 46a, 46b of the lower and rear rest shoes 45, 46 are moved. Then, it leaves the spiral groove surface Ws ground by the grindstone G (see FIGS. 6 and 7).

  According to the thread groove grinding apparatus provided with the above-described rest device, when the rest shoes 45 and 46 are inserted into the thread groove Wg, the rest shoe advancement / retraction mechanism (air cylinder mechanism 59) is operated, and the lower rest shoe 45 and the rear rest shoe are operated. 46 are brought into contact with the spiral groove surface Ws of the ball screw shaft W so as to follow the outer shape of the spiral groove surface WS. Then, the rest shoe fixing mechanism (stopper mechanism 60) is operated, and the ball screw shaft W is ground while maintaining the position following the outer shape of the spiral groove surface Ws. In this way, since the ball screw shaft W is supported from the two directions of the lower side and the rear side, it is possible to cope with the processing resistance that fluctuates complicatedly with the thread grinding process and the multi-directional force due to the weight of the workpiece with strong rigidity. Can do. Further, when supporting from two directions in this way, the outer diameter of the workpiece to be supported and the depth of the thread groove are different, so that it is difficult to support the two rest shoes in contact with each other at an optimum position. There is a case. However, in the present invention, even if there is a difference in the outer diameter of the spiral groove surface Ws of the ball screw shaft W or the depth of the screw groove Wg, the rest shoes 45 and 46 are actually brought into contact with each other from below and behind to make them follow. This makes it possible to easily place and support the rest shoes 45, 46 at the optimal position, effectively preventing run-out and bending during grinding and dramatically improving the processing accuracy of the screw shaft. be able to. In addition, since the rest shoes 45 and 46 are received by the spiral groove surface Ws of the ball screw shaft W, it is possible to reduce the production cost by omitting the trouble of pre-processing the rest receiving surface as in the prior art.

  Further, even when grinding a plurality of types of screw shafts, the lead angle of the thread portion is adjusted by a lead angle adjusting device (55, 56, 57, 58, 73, 74, 75, 76, etc.) for each screw shaft to be ground. Since the lower rest shoe 45 and the rear rest shoe 46 can be adjusted so as to follow the above, the two rest shoes 45, 46 can be easily adjusted to the optimum positions without requiring a lot of setup time. Can be supported.

  In addition, when the grindstone G is worn by shaping or wear due to shaping such as dressing / truing, and the grindstone outer diameter becomes small, the rest device 15 is provided on the grindstone base 13, so the grindstone (rotation center) G and the rest shoe 45 , 46 does not change relative position to the support surface, and the position where the grindstone G should come into contact with the grinding surface of the ball screw shaft W and the support surface of the rest shoes 45, 46 are separated. Even in such a case, according to the rest device 15 of the present invention, the position adjustment mechanism (42, 43) can be adjusted to bring the rest shoes 45, 46 closer to the grindstone G, thereby continuing at the most appropriate position. Can be supported.

  Further, since the rest shoes 45 and 46 are in contact with the ball screw shaft W at portions other than the ball rolling surface of the spiral groove surface Ws ground by the grindstone G, the rest shoes 45 and 46 are in contact with the ball rolling surface Wb. Grinding can be performed with high accuracy without scratching by contact.

    In addition, although it was set as the ball screw shaft as a screw shaft, it is not limited to this, For example, it can be used for grinding of the screw shaft in which a general screw groove is formed.

BRIEF DESCRIPTION OF THE DRAWINGS The whole schematic diagram of the thread groove grinding apparatus provided with the rest apparatus of embodiment of this invention. The side view which shows a part of thread groove grinding apparatus provided with the rest apparatus in a cross section. The front view. The enlarged view of a rest shoe part. The schematic diagram which shows the air cylinder mechanism and the stopper mechanism. The side view of the thread groove grinding apparatus provided with the rest apparatus in the removal position. The front view in the separation position. The figure which shows the state which supports the ball screw shaft ground by the same with a rest shoe. The figure which shows the state which the grindstone and the rest shoe contact | abutted on the spiral groove surface of the thread groove.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Screw groove grinding device, 12 ... Workpiece support device, 13 ... Grinding wheel base, 15 ... Rest device, 24 ... Screw shaft rotation drive device, 32 ... Axial direction movement device , 33 ... Radial direction moving device, 42 ... Position adjustment mechanism (advance / retreat member), 43 ... Position adjustment mechanism (hydraulic cylinder), 45 ... Lower rest shoe, 46 ... Rear rest shoe, 48... Synchronous operation device (numerical control device) 55... Lead angle adjusting device (rotating support projection shaft) 56... Lead angle adjusting device (rotating support hole) 57. Adjusting device (circular hole), 58... Lead angle adjusting device (fixing screw), 59... Rest shoe advance / retreat mechanism (air cylinder mechanism), 60... Rest shoe fixing mechanism (stopper mechanism), 73.・ Lead angle adjustment device (fitting hole), 74 ・ ・ ・ Lee Angle adjusting device (shoe support shaft), 75 ... Lead angle adjusting device (arc hole), 76 ... Lead angle adjusting device (fixing screw), G ... Whetstone, W ... Screw shaft (ball screw) Axis), Wb ... ball rolling surface, Ws ... spiral groove surface.

Claims (5)

In order to prevent bending due to grinding resistance when grinding a thread groove with a grindstone, in a rest device that supports a screw shaft that is a workpiece with a rest shoe,
The rest shoe has a lower rest shoe that contacts the spiral groove surface of the screw shaft from below and a rear rest shoe that contacts from the opposite side of the grindstone,
The lower rest shoe and the rear rest shoe include a rest shoe advancing / retreating mechanism for moving the rest shoe in a direction of moving in and out of the spiral groove surface following the shape of the spiral groove surface to be in contact with each other. And a rest shoe fixing mechanism for fixing the shoe at a position in contact with the spiral groove surface.   2. The rest device for a thread groove grinding device according to claim 1, wherein the lower rest shoe and the rear rest shoe are provided with a lead angle adjusting device that follows the lead angle of the thread groove of the screw shaft.   3. The ball rolling surface of a spiral groove surface ground by the grindstone according to claim 1, wherein the screw shaft is a ball screw shaft used for a ball screw. A rest device for a thread groove grinding device, wherein the rest device is disposed so as to abut against a portion other than the above.   4. The thread groove grinding device rest device according to claim 1, wherein the thread groove grinding device rest device is provided on a grindstone table that supports the grindstone, and the lower rest as the grindstone reduces an outer diameter due to wear. 5. A rest device for a thread groove grinding device, comprising a position adjusting mechanism for adjusting a relative position of the shoe and the rear rest shoe with respect to the grindstone. A workpiece support device that rotatably supports a screw shaft having a screw shaft formed in a spiral shape, a screw shaft rotation drive device that rotationally drives the screw shaft supported by the workpiece support device, and a spiral of the screw groove A grindstone base that rotatably supports a grindstone that grinds the groove surface, an axial movement device that moves the grindstone base relative to the workpiece support device in the axial direction of the screw shaft, and the grindstone stand A radial movement device that moves relative to a workpiece support device in the radial direction of the screw shaft; and the screw that moves the grindstone table in the axial direction of the screw shaft in synchronization with the rotation of the screw shaft. In a thread groove grinding apparatus comprising: an axial rotation driving device and a synchronous operation device that operates the axial movement device;
The thread groove grinding apparatus according to claim 1, wherein the grinding wheel base is provided with a rest device according to claim 1, which is movable in the axial direction of the screw shaft along with the grinding wheel base.

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