JP2014034071A - Rest device of grinder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rest device of a grinder capable of improving roundness of a workpiece in grinding work.SOLUTION: A rest device of a grinder includes: three rest shoes 31, 32, 33 for supporting a workpiece W by coming into contact with an outer circumferential surface of the workpiece W, while being spaced apart from one another in a circumferential direction along the outer circumferential surface of a workpiece W; and a holding member 35 rotatably provided around a rotating shaft 35a positioned between either two rest shoes 31, 33 next to each other, and holding each of the rest shoes 31, 32, 33 so that the rest shoes 31, 32, 33 each come into a state of being tangent to a virtual circle Cv that is set in a diameter Dv between an outer diameter Dw1 of the workpiece W before the grinding work and an outer diameter Dw2 of the workpiece W after the grinding work.

Description

  The present invention relates to a rest device applied to a grinding machine that performs grinding by relatively moving a grinding wheel and a workpiece.

  The grinding machine performs grinding by bringing a rest device into contact with the outer peripheral surface of the workpiece and supporting the workpiece. As described above, by using the rest device, even when the rigidity of the workpiece is relatively small, it is possible to perform the grinding process in which the bending of the workpiece due to the grinding resistance is suppressed. However, when the outer peripheral surface of the workpiece has irregularities, the axial center of the workpiece is displaced when these concave and convex portions come into contact with the rest device. In grinding with a grinder, it is known that the grinding resistance fluctuates with the displacement of the axis of the workpiece, and periodic waviness occurs on the outer peripheral surface of the workpiece.

  On the other hand, Patent Documents 1 and 2 disclose a grinding machine rest device that can remove waviness generated in a workpiece by appropriately setting the positions of two rest shoes. According to Patent Document 1, a configuration is described in which the position of one rest shoe is adjusted based on the number of irregularities on the outer peripheral surface of a workpiece. Patent Document 2 describes a configuration for adjusting the installation angle of two rest shoes.

JP 2008-246622 A JP 2009-56519 A

  However, in the configurations of Patent Documents 1 and 2, undulations with various periods and amplitudes are generated depending on the initial positions of the two rest shoes. Therefore, in the configurations of Patent Documents 1 and 2, there is a possibility that the swell cannot be sufficiently removed depending on the period of the swell that has occurred. In addition, there is a demand for a grinding machine to be highly accurate so that the roundness of the workpiece can be improved.

  The present invention has been made in view of such circumstances, and an object thereof is to provide a rest device for a grinding machine that can improve the roundness of a workpiece in grinding.

  (Claim 1) A rest apparatus for a grinding machine according to the present invention is applied to a grinding machine that performs grinding by relatively moving a grinding wheel and a workpiece, and is separated from each other in the circumferential direction along the outer peripheral surface of the workpiece. The three rest shoes are arranged in contact with the outer peripheral surface of the workpiece and support the workpiece, and are provided so as to be rotatable around a rotation shaft positioned between any two adjacent rest shoes. Each rest shoe is in contact with a virtual circle set to a diameter between the outer diameter of the workpiece before grinding and the outer diameter of the workpiece after grinding. A holding member for holding, and in the grinding process, when the workpiece has a diameter larger than the imaginary circle, the work is performed by two rest shoes positioned on both ends in the circumferential direction of the rest shoes. To support things Said workpiece supporting the workpiece by two the rest shoe adjacent to each other with the rotating shaft of the holding member of each said rest shoe in the case of smaller diameter than the virtual circle.

  (Claim 2) Further, the first rest shoe is shifted by a first angle α in the circumferential direction with respect to a reference line passing through a grinding point where the grinding wheel contacts the workpiece and an axis of the workpiece. The second rest shoe is disposed at a position shifted from the first rest shoe by a second angle β in the circumferential direction, or at a position shifted by 90 ° in the circumferential direction with respect to the reference line. The third rest shoe is disposed between the first rest shoe and the second rest shoe, and is third in the circumferential direction from the first rest shoe to the second rest shoe. The first angle α is set in a range of 0 ° <α <90 °, and the second angle β is (2m · α) ° where m is an integer other than 0. And the third angle γ is {(2n−1) · α} °, where n is a positive integer. The rotation shaft of the holding member may be positioned between the first rest shoe and the third rest shoe.

(Claim 3) Further, the rotation shaft of the holding member may be arranged at the center of the first rest shoe and the third rest shoe.
(Claim 4) The first angle α may be set to {180 / (p + 2)} °, where p is a positive integer.
(Claim 5) Further, the contact surface of each rest shoe that contacts the outer peripheral surface of the workpiece is formed into a curved surface having a curvature smaller than the curvature of the outer peripheral surface of the workpiece before the grinding. You may do it.

  (Claim 1) According to the present invention, in a grinding process by a grinder, when the workpiece has a larger diameter than the virtual circle, the rest device includes two rest shoes positioned on both circumferential sides of the three rest shoes. The work is supported by the rest shoe. Then, when the outer diameter of the workpiece is gradually reduced by grinding and becomes smaller than the virtual circle, the rest device has two rests adjacent to each other across the rotation shaft of the holding member among the three rest shoes. The work is supported by the shoe. That is, in the rest device of the present invention, when the outer diameter of the workpiece to be processed by the grinding machine changes, the two rest shoes brought into contact with the workpiece among the three rest shoes are automatically changed. Yes.

  Further, the holding member that holds the three rest shoes is provided so as to be rotatable about the rotation axis. Therefore, when the rest device has irregularities on the outer peripheral surface of the workpiece, the holding member swings (reciprocates) as it moves in the circumferential direction of the irregularities. That is, the rest device of the present invention is configured to move each rest shoe relative to the axis of the workpiece so as to follow the outer peripheral shape of the workpiece. With such a configuration, it becomes possible to suppress fluctuations in grinding resistance in grinding, and the roundness of the workpiece can be improved.

  (Claim 2) According to the present invention, when the workpiece has a larger diameter than the virtual circle, the first and second rest shoes positioned at both ends in the circumferential direction of the holding member support the workpiece. Become. When grinding is performed in this state, if there are irregularities on the outer peripheral surface of the workpiece, a double angle 2α of the first angle α is set on the outer peripheral surface of the workpiece depending on the installation angle of the first and second rest shoes. Swelling with one cycle occurs. When the workpiece has a smaller diameter than the virtual circle, the first and third rest shoes positioned across the rotation shaft of the holding member support the workpiece.

  At this time, the first and third rest shoes support the outer peripheral surface of the workpiece at a position separated by a half period of waviness (when n = 1). That is, when the first rest shoe supports the undulating concave portion, the third rest shoe supports the undulating convex portion. This prevents the movement of the axis of the workpiece even when any of the rest shoes supports the convex portion of the swell, and reliably supports the workpiece by contacting the concave portion of the swell. it can. Therefore, the fluctuation of the grinding resistance in the grinding process can be suppressed, and the generated waviness of the workpiece can be removed. Therefore, the roundness of the workpiece can be improved.

  (Claim 3) According to the present invention, in a state where the workpiece has a smaller diameter than the virtual circle and is supported by the first and third rest shoes, The sum of the distance from one rest shoe to the axis of the workpiece and the distance from the third rest shoe to the axis of the workpiece is constant. Thereby, even when the waviness is generated on the outer peripheral surface of the workpiece, the movement of the axis of the workpiece can be more reliably prevented. Therefore, since the waviness of the workpiece can be removed by supporting the workpiece more stably, the processing accuracy in grinding can be improved.

  (Claim 4) According to the present invention, when the workpiece has a larger diameter than the virtual circle and is supported by the first and second rest shoes, the undulation occurs in the workpiece. An integral multiple of the angle for one period is 360 °. That is, the undulation corresponding to (p + 2) periods occurs on the outer peripheral surface of the workpiece, where the double angle 2α of the first angle α is one period. As a result, the undulation of the workpiece is smoothly continued in the circumferential direction. Therefore, the rest device is operated by the first and third rest shoes in a state where the workpiece has a smaller diameter than the virtual circle. Can be suitably supported, and the undulation generated in the workpiece can be more reliably removed.

  (Claim 5) According to the present invention, each rest shoe is connected to the workpiece so as to follow the outer peripheral shape of the workpiece by the swinging of the holding member even when waviness is generated on the outer peripheral surface of the workpiece. The contact state can be suitably maintained. In addition, when each rest shoe is arranged so as to have a predetermined angle with respect to the reference line, the curvature of the contact surface is smaller than the curvature of the outer peripheral surface of the workpiece. A predetermined angle can be maintained. Therefore, the rest device can generate the undulation of the target period when the workpiece has irregularities, and can reliably remove the undulation. Therefore, the roundness of the workpiece can be improved.

It is a general view which shows the grinding machine in embodiment. It is sectional drawing of the AA direction in FIG. It is explanatory drawing which expands and shows a part of rest apparatus in FIG. It is a figure which shows a part of wave | undulation which generate | occur | produced in the outer peripheral surface of the workpiece. It is a schematic diagram which shows operation | movement of a rest apparatus.

<Embodiment>
(Configuration of grinding machine 1)
Hereinafter, an embodiment embodying a rest device for a grinding machine of the present invention will be described with reference to FIGS. The grinding machine 1 is a machine tool that performs grinding by moving the grinding wheel 11 relative to a supported workpiece W. The grinding machine 1 includes a grinding wheel base 10, a spindle device 20, and a rest device 30. In this embodiment, the grinding machine 1 illustrates a case where grinding is performed on a journal of a crankshaft that is a workpiece W.

  The grinding wheel base 10 includes a grinding wheel 11 that grinds the workpiece W and a grinding wheel shaft 12 that supports the grinding wheel 11. The grinding wheel 11 is configured by bonding hard abrasive grains to the outer periphery of a disk-shaped metal core, for example. The grindstone shaft 12 is supported by the grindstone base 10 so as to be rotatable about an axis parallel to the Z-axis direction (left-right direction in FIG. 1), and is rotationally driven by a grindstone shaft driving motor (not shown). The grindstone platform 10 is disposed on the upper surface of the bed 2 and is disposed on a guide rail (not shown) extending in the X-axis direction (vertical direction in FIG. 1) perpendicular to the Z-axis direction. The grinding wheel platform 10 can move the grinding wheel 11 in the X-axis direction by the rotational drive of the X-axis servomotor. The grinding wheel base 10 is controlled by the control device of the grinding machine 1 to move the grinding wheel 11 in the X-axis direction and the rotation speed of the grinding wheel shaft 12.

  The spindle device 20 supports both ends of the workpiece W sandwiched in the axial direction by the center so that the workpiece W can rotate around the Z axis. The spindle device 20 is installed on the upper surface of a table 21 arranged on a guide rail (not shown) extending in the Z-axis direction on the upper surface of the bed 2, and the workpiece W is moved to the Z-axis by rotational driving of a Z-axis servo motor. It can move in the direction. The spindle device 20 includes a spindle stock 25 that supports one end of the workpiece W and a tailstock 26 that supports the other end of the workpiece W.

  The headstock 25 is installed on the table 21 and rotatably supports the main shaft 25a. A spindle center 25b that supports one end of the workpiece W is attached to the tip of the spindle 25a. The main shaft 25a is rotationally driven by a servo motor. The spindle stock 25 is controlled by the control device of the grinding machine 1 such as the rotational speed and rotational phase of the spindle. The tailstock 26 is coaxially installed on the table 21 so as to face the headstock 25 in the Z-axis direction. In the tailstock 26, a tailstock center 26b that supports the other end of the workpiece W is attached to the end of the headstock 25 side (left side in FIG. 1).

  The rest device 30 is a device that supports the workpiece W by bringing a rest shoe into contact with the outer peripheral surface of the workpiece W in the grinding process by the grinding machine 1. The rest device 30 includes three rest shoes 31, 32, 33 disposed on the rear side of the workpiece W (on the opposite side of the grinding wheel 11 with the workpiece W interposed therebetween and on the right side in FIG. 2), and the workpiece. A rest shoe 34 disposed immediately below W, a holding member 35, and a rest arm 36 are provided.

  The three rest shoes 31, 32, 33 located on the rear side of the workpiece W are spaced apart in the circumferential direction along the outer peripheral surface of the workpiece W, and come into contact with the outer peripheral surface of the workpiece W to contact the workpiece. Support W. These three rest shoes 31, 32, 33 are held by a holding member 35. Here, the first rest shoes 31, in the order in which they are arranged on the upper end side, the lower end side, and the center side of the holding member 35, The second rest shoe 32 and the third rest shoe 33 are used. Each rest shoe 31, 32, 33 is formed with a cylindrical curved surface extending in the direction of the rotation axis 35 a of the holding member 35 with contact surfaces 31 a, 32 a, 33 a contacting the outer peripheral surface of the workpiece W being formed on the workpiece W. The workpiece W can be supported by making line contact with each other.

  The holding member 35 is a member that supports the three rest shoes 31, 32, 33. As shown in FIG. 2, the holding member 35 is provided so as to be rotatable about the rotation shaft 35 a with respect to the rest device 30. The rotation shaft 35 a is located between the first and third rest shoes 31, 32, 33 adjacent to each other. With such a configuration, when the holding member 35 swings about the rotation shaft 35a, the distance between the three rest shoes 31, 32, 33 to be held and the axis O of the workpiece W varies. Yes.

  As shown in FIG. 3, the holding member 35 holds the rest shoes 31, 32, 33 so that the rest shoes 31, 32, 33 are in contact with the virtual circle Cv. Here, the diameter Dv of the virtual circle Cv is set between the material diameter Dw1 and the finishing diameter Dw2 of the workpiece W (Dw1> Dv> Dw2). The material diameter Dw1 of the workpiece W is the outer diameter Dw of the workpiece W before grinding, and the finishing diameter Dw2 of the workpiece W is the outer diameter Dw of the workpiece W after grinding.

  According to such a configuration, the rest device 30 has the three rest shoes 31, 32, 33 when the outer diameter Dw of the workpiece W is larger than the diameter Dv of the virtual circle Cv (Dw> Dv). Of these, the third rest shoe 33 located on the center side is not in contact with the workpiece W. Therefore, the rest device 30 supports the workpiece W with the first rest shoe 31 and the second rest shoe 32 that are located on both ends of the holding member 35.

  When the outer diameter Dw of the workpiece W becomes smaller than the diameter Dv of the virtual circle Cv by grinding (Dw <Dv), the rest device 30 rotates the rotation shaft 35a among the three rest shoes 31, 32, 33. The second rest shoe 32 that is farthest away from the workpiece is not in contact with the workpiece W, and the first rest shoe 31 and the third rest shoe 33 that are arranged in the circumferential direction with the rotation shaft 35a of the holding member 35 interposed therebetween. Will support the workpiece W. As described above, the rest device 30 includes two rest shoes that are brought into contact with the workpiece W among the three rest shoes 31, 32, 33 in accordance with the change in the outer diameter Dw of the workpiece W to be processed by the grinding machine 1. Is configured to change automatically.

  The fourth rest shoe 34 disposed immediately below the workpiece W supports the workpiece W from below and maintains the position of the axis O of the workpiece W in the Y direction. The fourth rest shoe 34 is supported by a rest arm 36 that can rotate around a support shaft 36a. The detailed configuration of the rest device 30 and the details of the operation in grinding will be described later.

(Detailed configuration of rest device 30)
Next, the detailed configuration of the rest device 30 will be described with reference to FIGS. 2 and 3. In the rest device 30, as shown in FIG. 3, the first rest shoe 31 held by the holding member 35 is disposed at a position shifted by the first angle α on the lower side in the circumferential direction with respect to the reference line Ls. . Here, the reference line Ls is a straight line passing through the grinding point T at which the grinding wheel 11 contacts the workpiece W and the axis O of the workpiece W, as shown in FIG.

  The first angle α of the first rest shoe 31 is set in a range of (0 ° <α <90 °). Further, the first angle α is set to an angle represented by {180 / (p + 2)} °, where p is a positive integer, and is set to 15 ° in this embodiment (p = 10, α = 15 °). Here, assuming that the angle at which the rear-side rest shoe is displaced in the circumferential direction from the reference line Ls is the installation angle, the installation angle of the first rest shoe 31 is equal to the first angle α and is 15 °.

  In the rest device 30, the second rest shoe 32 held by the holding member 35 is, as shown in FIG. 3, a second angle β from the first rest shoe 31 to the lower side in the circumferential direction in the contact state before processing. It is arranged at a shifted position. The second angle β of the second rest shoe 32 is set to (2m · α) °, where m is an integer other than 0. That is, the second angle β is set to an even multiple of the first angle α, and is set to 30 ° (α = 15 °, m = 1) in the present embodiment. Therefore, the installation angle of the second rest shoe 32 is 45 ° obtained by adding the second angle β to the first angle α.

  In the rest device 30, the third rest shoe 33 held by the holding member 35 is disposed between the first rest shoe 31 and the second rest shoe 32, and the second rest shoe 31 extends from the first rest shoe 31 to the second rest shoe 31. It is arranged at a position shifted by the third angle γ toward the lower side in the circumferential direction toward the rest shoe 32. The third angle γ of the third rest shoe 33 is set to {(2n−1) · α} °, where n is a positive integer. That is, the third angle γ is set to an odd multiple of the first angle α and smaller than the second angle β, and is set to 15 ° in this embodiment (α = 15 °, n = 1). Therefore, the installation angle of the third rest shoe 33 is 30 ° obtained by adding the third angle γ to the first angle α.

  The rotation shaft 35 a of the holding member 35 is disposed at the center of the first rest shoe 31 and the third rest shoe 33. That is, in this embodiment, the distance from the rotating shaft 35a to the first and third rest shoes 31, 33 is configured to be equal. Accordingly, the rotation shaft 35 a of the holding member 35 is disposed at a position shifted from the first rest shoe 31 toward the second rest shoe 32 by a half angle (γ / 2) of the third angle γ. Therefore, the rotation shaft 35a is disposed at a position shifted by 22.5 ° in the circumferential lower side with respect to the reference line Ls.

  In addition, as described above, each of the rest shoes 31, 32, and 33 has contact surfaces 31 a, 32 a, and 33 a that are in contact with the outer peripheral surface of the workpiece W formed in a cylindrical curved surface. And each contact surface 31a, 32a, 33a is formed so that it may become a curvature smaller than the curvature of the outer peripheral surface of the workpiece W before grinding. That is, the diameter of the curvature circle of each contact surface 31a, 32a, 33a is at least smaller than the material diameter Dw1 of the workpiece W.

(Operation in grinding of the rest device 30)
The operation | movement in the grinding process of the rest apparatus 30 which consists of the structure mentioned above is demonstrated with reference to FIGS. First, the workpiece W is supported by the spindle stock 25 and the tailstock 26. Next, the Z axis servo motor of the spindle device 20 is operated to position the grinding wheel 11 at the machining position on the workpiece W, that is, the axial position where the journal of the crankshaft is located. Then, the rest device 30 is moved so as to approach the workpiece W, and the rest arm 36 is rotated around the support shaft 36 a to bring the fourth rest shoe 34 into contact with the workpiece W.

  Here, the three rest shoes 31, 32, 33 are arranged so as to be in contact with the virtual circle Cv by the holding member 35, and the diameter Dv of the virtual circle Cv is smaller than the material diameter Dw 1 of the workpiece W. Therefore, when the rest device 30 is brought close to the workpiece W, as shown in FIG. 3, among the three rest shoes 31, 32, 33 held by the holding member 35, the first located on both ends of the holding member 35. The rest shoe 31 and the second rest shoe 32 come into contact with the workpiece W. As described above, the rest device 30 supports the rear side of the workpiece W by the first and second rest shoes 31 and 32 at the start of the grinding process, and lowers the workpiece W by the fourth rest shoe 34. Support the side.

  Next, the workpiece W is rotated around the axis O by the servo motor of the headstock 25. Then, the grinding wheel 11 is advanced to the workpiece W by the X-axis servomotor of the grinding wheel base 10 while the grinding wheel 11 is rotated, and the grinding process is started. At this time, the first and second rest shoes 31 and 32 that are located on the rear side of the workpiece W and are in contact with the workpiece W are maintained in a state of pressing the workpiece W toward the grinding wheel 11. ing. Therefore, when the outer peripheral surface of the workpiece W has irregularities, the axis O of the workpiece W is displaced, and the grinding resistance at the grinding point T varies.

  Here, the fluctuation of the grinding resistance is caused, for example, when the unevenness caused by uncut material in another processing before grinding processing contacts the rest shoe, or when the coolant flows into the oil hole provided in the journal and the dynamic pressure decreases. It occurs in some cases. In any case, the fluctuation of the grinding resistance is periodically increased and decreased by the rotation of the workpiece W. And if the convex part of the outer peripheral surface of the workpiece W contacts the rest shoe on the rear side and the axis O of the workpiece W is displaced to the grinding wheel 11 side, the grinding resistance increases and the grinding at the grinding point T is performed. The amount is increased and a recess is formed. Further, when the concave portion of the outer peripheral surface of the workpiece W comes into contact with the rest shoe on the rear side and the axis O of the workpiece W is displaced toward the rest device 30 side, the grinding resistance is reduced and the grinding amount at the grinding point T is reduced. And the convex part is formed.

  Then, the newly formed recesses and protrusions come into contact with the rear-side rest shoe, so that the protrusions and recesses are further formed at the grinding point T, and this is repeated to periodically form the outer peripheral surface of the workpiece W. A swell may occur. The waviness period correlates with the positional relationship among the grinding wheel 11, the workpiece W and the rear rest shoe. More specifically, the swell cycle is a cycle corresponding to the angle at which the rear rest shoe is displaced in the circumferential direction with respect to the reference line Ls. Specifically, when the rear-side rest shoe is disposed at a position shifted from the reference line Ls in the circumferential direction by the installation angle θ, undulation occurs with a double angle 2θ of the installation angle θ as one cycle.

  That is, in this embodiment, the installation angles of the first rest shoe 31 and the second rest shoe 32 arranged on the rear side of the workpiece W are 15 ° (α) and 45 ° (α + β), respectively. The first rest shoe 31 generates a swell with 30 ° (2α) as one cycle, and the second rest shoe 32 generates a swell with 90 ° (2 (α + β)) as one cycle. Here, since the 2 (α + β) cycle is an odd multiple (here, 3 times) of the 2α cycle, the phase in which the convex portion and the concave portion are formed in the undulation of the 2 (α + β) cycle is convex in the undulation of the 2α cycle. This coincides with the phase in which the portion and the recess are formed. Therefore, when waviness occurs due to the support of the workpiece W by the first rest shoe 31 and the second rest shoe 32, only waviness with a 2α period is substantially generated as shown in FIG. It can be regarded as a thing.

  Further, since the integral multiple (here, 12 times) of the angle 2α (30 °) with respect to one period in this undulation is 360 °, the undulation of the workpiece W is generated so as to be smoothly continued in the circumferential direction. Further, the fourth rest shoe 34 is disposed at a position shifted by 90 ° from the reference line Ls, and supports the workpiece W from directly below. Therefore, when the irregularities on the outer peripheral surface of the workpiece W come into contact with the fourth rest shoe 34, the axis O of the workpiece W is only displaced in the vertical direction (Y-axis direction). Therefore, the contact between the fourth rest shoe 34 and the unevenness of the workpiece W has little influence on the grinding resistance at the grinding point T and is not directly involved in the occurrence of waviness.

  Thus, when grinding by the grinding machine 1 is started, the outer diameter Dw of the workpiece W is larger than the diameter Dv of the virtual circle Cv of the rest device 30 (Dw> Dv). Grinding is performed with the second rest shoes 31 and 32 supporting the workpiece W. And when a wave | undulation generate | occur | produces in the workpiece W, the wave | undulation of 2 (alpha) period is produced | generated. Then, when the outer diameter Dw of the workpiece W is gradually reduced by grinding and becomes smaller than the diameter Dv of the virtual circle Cv of the rest device 30 (Dw <Dv), as shown in FIG. Grinding is performed with the third rest shoes 31 and 33 supporting the workpiece W.

  Here, the undulation generated in the workpiece W in the grinding process is actually a minute unevenness, but in FIG. 4, the undulation of the workpiece W is exaggerated for explaining the operation of the rest device 30. Yes. The first and third rest shoes 31 and 33 that are in contact with the workpiece W are maintained in a state of pressing the workpiece W toward the grinding wheel 11. Therefore, the first and third rest shoes 31 and 33 follow the outer peripheral shape of the workpiece W as the workpiece W rotates because the holding member 35 holding them swings around the rotation shaft 35a. Thus, relative movement is performed in the circumferential direction and the radial direction.

  Further, as described above, the third rest shoe 33 is arranged at a position shifted from the first rest shoe 31 in the circumferential direction by a third angle γ. In other words, in the present embodiment, the distance between the first and third rest shoes 31 and 33 (γ = 15 °) is a half angle (α = γ =) of the angle 2α (30 °) with respect to one cycle in the wave of the workpiece W. 15 °). Therefore, as shown in FIG. 4, the first and third rest shoes 31, 33 are in contact with and supported by the workpiece W at positions shifted by a half cycle of the undulation of the workpiece W.

  Thereby, for example, when the first rest shoe 31 supports the undulating concave portion, the third rest shoe 33 supports the undulating convex portion. Further, the rotation shaft 35 a of the holding member 35 is disposed at the center of the first and third rest shoes 31 and 33. Therefore, when the first and third rest shoes 31 and 33 move relative to the outer peripheral shape of the workpiece W, the holding member 35 swings about the rotation shaft 35a, so that the first rest shoes The sum of the distance L1 from 31 to the axis O of the workpiece W and the distance L3 from the third rest shoe 33 to the axis O of the workpiece W is always constant.

  According to such a configuration, when supporting the undulation convex portion, conventionally, the grinding resistance at the grinding point T is increased, but one of the first and third rest shoes 31 and 33 is the diameter of the workpiece W. The workpiece W is supported while retracting outward in the direction. When supporting the undulation recess, the grinding resistance at the grinding point T is conventionally reduced, and the other of the first and third rest shoes 31 and 33 follows the inner side in the radial direction of the workpiece. Support the object W. In this way, by holding the rest shoes 31 and 33 while the holding member 35 swings, a change in the pressing force of the rest shoes 31 and 33 against the workpiece W is reduced, and the axis O of the workpiece W is reduced. Is suppressed from being displaced.

  In the grinding process, in the process in which the workpiece W is supported by the first and third rest shoes 31 and 33, the displacement of the axis O of the workpiece W is suppressed, and thereby the fluctuation of the grinding resistance at the grinding point T is suppressed. Is suppressed. When the grinding wheel 11 is advanced to the workpiece W by the X-axis servomotor of the grinding wheel base 10 and the grinding process is continued, the outer diameter Dw of the workpiece W gradually becomes smaller and the workpiece W becomes smaller. The swell is removed by grinding. When the outer diameter Dw of the workpiece W reaches the target finishing diameter Dw2, the grinding machine 1 stops the advancement of the grinding wheel 11 by the grinding wheel base 10 and ends the grinding process.

(Effects of the configuration of the present embodiment)
According to the rest device 30 of the grinding machine 1 described above, the rest device 30 holds the three rest shoes 31, 32, 33 by the holding member 35 that is rotatably provided, and the outer diameter Dw of the workpiece W by grinding processing. In accordance with the change, the two rest shoes brought into contact with the workpiece W are automatically changed. Therefore, when the outer peripheral surface of the workpiece W is uneven, the rest device 30 moves the rest shoes 31, 32, 33 with respect to the axis O of the workpiece W so as to follow the outer peripheral shape of the workpiece W. Relative movement. With such a configuration, it becomes possible to suppress fluctuations in grinding resistance in grinding, and the roundness of the workpiece W can be improved.

  Further, when the workpiece W has a larger diameter than the virtual circle Cv, the rest device 30 moves the workpiece W by the first and second rest shoes 31 and 32 positioned on both ends in the circumferential direction of the holding member 35. To support. Thereby, when the outer peripheral surface of the workpiece W is uneven, the outer peripheral surface of the workpiece W is substantially changed depending on the installation angles (15 °, 45 °) of the first and second rest shoes 31, 32. In particular, the undulation with the double angle 2α of the first angle α as one cycle occurs. That is, although the workpiece W is supported by the two rest shoes 31 and 32 from the rear side of the workpiece W, the undulation having substantially one kind of period is generated.

  In the rest device 30, when the workpiece W has a smaller diameter than the virtual circle Cv, the first and third rest shoes 31 and 33 positioned with the rotation shaft 35 a of the holding member 35 interposed therebetween support the workpiece W. . At this time, the third rest shoe 33 is located at a position shifted from the first rest shoe 31 by a half cycle (α) of undulation. This prevents the movement of the axial center O of the workpiece W even when any of the rest shoes 31, 33 supports the convex portion of the swell, and reliably contacts the concave portion of the swell with the workpiece. W can be supported. Therefore, fluctuation of the grinding resistance in the grinding process can be suppressed, and the generated waviness of the workpiece W can be removed.

  Further, the rotation shaft 35 a of the holding member 35 is arranged at the center of the first rest shoe 31 and the third rest shoe 33. Thus, in a state where the two rest shoes 31 and 33 support the workpiece W, the holding member 35 swings around the rotation shaft 35a, so that the axis of the workpiece W is removed from the first rest shoe 31. The sum of the distance L1 to the center O and the distance L3 from the third rest shoe 33 to the axis O of the workpiece W is constant. Thereby, even when the waviness is generated on the outer peripheral surface of the workpiece W, the movement of the axis O of the workpiece W can be more reliably prevented. Therefore, since the waviness of the workpiece W can be removed by supporting the workpiece W more stably, the processing accuracy in grinding can be improved.

  The first angle α of the first rest shoe 31 is set to an angle satisfying {180 / (p + 2)} °, where p is a positive integer. In this embodiment, when p = 10, the first angle α is 15 °, so that the angle with respect to one cycle of the waviness of the workpiece W is 30 °. As a result, an integral multiple of the angle for one period of undulation is 360 °. In other words, in the present embodiment, undulation corresponding to (p + 2 = 12) cycles occurs on the outer peripheral surface of the workpiece W, where the double angle 2α (30 °) of the first angle α (15 °) is one cycle. become. As a result, the undulation of the workpiece W is smoothly continued in the circumferential direction. Therefore, the rest device 30 is configured so that the first and third rest shoes are in a state where the workpiece W has a smaller diameter than the virtual circle Cv. The workpiece W can be suitably supported by 31 and 33, and the undulation generated in the workpiece W can be more reliably removed.

  Here, the three rest shoes 31, 32, 33 are relatively moved in the circumferential direction and the radial direction so as to follow the outer peripheral shape of the workpiece W by the swinging of the holding member 35 when waviness occurs in the workpiece W. Will do. Therefore, the contact point with the workpiece W may move in the circumferential direction on the contact surfaces 31a, 32a, 33a of the rest shoes 31, 32, 33 that are in contact with the outer peripheral surface of the workpiece W. When the contact point with the workpiece W moves in the circumferential direction, the installation angles of the rest shoes 31, 32, 33 are shifted.

  Thus, as in the present embodiment, the contact surfaces 31a, 32a, 33a of the respective rest shoes 31, 32, 33 are formed into cylindrical curved surfaces, and the curvature thereof is the curvature of the outer peripheral surface of the workpiece W before grinding. To make it smaller. As a result, each of the rest shoes 31, 32, 33 follows the outer peripheral shape of the workpiece W by the swinging of the holding member 35 even when waviness occurs on the outer peripheral surface of the workpiece W. And the set installation angle of each of the rest shoes 31, 32, 33 can be suitably maintained. Therefore, when the workpiece W has irregularities, the rest device 30 can generate the swell of the target period and can reliably remove the swell. Therefore, the roundness of the workpiece W can be improved.

<Modification of Embodiment>
In the present embodiment, each of the rest shoes 31, 32, 33 has a first angle α = 15 ° (p = 10), a second angle β = 30 ° (m = 1), and a third angle γ = 15 ° ( n = 1). On the other hand, each angle may be set as appropriate. Even in such a configuration, as the outer diameter Dw of the workpiece W changes, the combination of the two rest shoes that support the workpiece W changes during the grinding process, which improves the processing accuracy of the grinding process. The roundness of the workpiece can be improved.

  However, it is preferable that each angle is set so as to satisfy the range or the mathematical expression shown in the present embodiment. For example, the first angle α = 30 (p = 4), the second angle β = −30 ° (m = −1), and the third angle γ = 30 ° (n = 1) may be arranged. Here, the second angle β = −30 ° indicates that the second rest shoe 32 is arranged at a position shifted by 30 ° toward the opposite side of the circumferential direction in which the first rest shoe 31 takes an angle. Show. That is, the first rest shoe 31 is arranged at a position shifted by 30 ° from the reference line Ls in the circumferential lower side, whereas the second rest shoe 32 is 30 from the reference line Ls in the circumferential upper side. It is arranged at a position shifted. Further, since the third rest shoe 33 is 30 ° from the first rest shoe 31 toward the second rest shoe 32, the third rest shoe 33 is disposed on the reference line Ls. Even in such a configuration, the same effects as in the present embodiment can be obtained.

  Further, the second angle β of the second rest shoe 32 may be set to 90 °. In such a configuration, the second rest shoe 32 supports the workpiece W from below similarly to the fourth rest shoe 34 in the present embodiment. Then, when the unevenness of the workpiece W comes into contact with the second rest shoe 32, the axis O of the workpiece W is only displaced in the vertical direction (Y-axis direction). It is not necessary to determine the installation angle of the second rest shoe 32 depending on the positional relationship. Even in such a configuration, the same effects as in the present embodiment can be obtained.

  1: grinding machine, 11: grinding wheel, 30: rest device, 31: first rest shoe, 32: second rest shoe, 33: third rest shoe, 31a, 32a, 33a: contact surface, 35: Holding member, 35a: rotation axis, α: first angle, β: second angle, γ: third angle, Ls: reference line, T: grinding point, W: workpiece, O: shaft center, Dw: workpiece , Cv: virtual circle, Dv: virtual circle diameter

Claims (5)

Applied to grinding machines that perform grinding by moving the grinding wheel and workpiece relative to each other,
Three rest shoes that are spaced apart from each other in the circumferential direction along the outer peripheral surface of the workpiece, and that support the workpiece in contact with the outer peripheral surface of the workpiece;
It is provided rotatably around a rotation shaft located between any two of the adjacent rest shoes, and an outer diameter of the workpiece before the grinding and an outer diameter of the workpiece after the grinding A holding member that holds each rest shoe so that each said rest shoe comes into contact with a virtual circle set to a diameter between,
In the grinding process, when the workpiece is larger in diameter than the virtual circle, the workpiece is supported by the two rest shoes positioned on both ends in the circumferential direction of the rest shoes, and the workpiece is When the diameter is smaller than the imaginary circle, the rest device of the grinding machine supports the workpiece by the two rest shoes adjacent to each other with the rotation shaft of the holding member among the rest shoes. The first rest shoe is disposed at a position shifted by a first angle α in the circumferential direction with respect to a grinding point at which the grinding wheel contacts the workpiece and a reference line passing through the axis of the workpiece,
The second rest shoe is disposed at a position shifted from the first rest shoe by a second angle β in the circumferential direction, or at a position shifted by 90 ° in the circumferential direction with respect to the reference line,
The third rest shoe is disposed between the first rest shoe and the second rest shoe, and a third angle in the circumferential direction from the first rest shoe toward the second rest shoe. It is arranged at a position shifted by γ,
The first angle α is set in a range of 0 ° <α <90 °,
The second angle β is set to (2m · α) °, where m is an integer other than 0,
The third angle γ is set to {(2n−1) · α} °, where n is a positive integer,
The rest device for a grinding machine according to claim 1, wherein the rotation shaft of the holding member is located between the first rest shoe and the third rest shoe.   The rest device for a grinding machine according to claim 2, wherein the rotation shaft of the holding member is arranged at the center of the first rest shoe and the third rest shoe.   The said 1st angle (alpha) is a rest apparatus of the grinding machine of Claim 2 or 3 set to {180 / (p + 2)} degree by making p into a positive integer.   The contact surface of each said rest shoe which contacts the outer peripheral surface of the said workpiece is formed in the curved surface used as a curvature smaller than the curvature of the outer peripheral surface of the said workpiece before the said grinding process, Any one of the grinding machine rest devices.

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