JP6589391B2 - Electromagnetic chuck and composite grinding machine equipped with electromagnetic chuck - Google Patents

Description

  The present invention relates to an electromagnetic chuck for fixing a workpiece by electromagnetic in order to process the workpiece, and a composite grinding machine including the electromagnetic chuck.

  Conventionally, when processing such as cutting and grinding is performed on a workpiece, the workpiece is not fixed by a general mechanical chuck that is tightened with a nail or the like, but according to the shape of the workpiece and the part to be processed. Thus, there is a technique of fixing on a face plate using an electromagnetic attraction (magnetic attraction) (see Patent Document 1-2).

JP-A-53-111584 JP 54-90674 A

  However, in the technique disclosed in Patent Literature 1-2, both the workpiece and the material of the face plate of the electromagnetic chuck to which the workpiece is fixed are usually metals. For this reason, the coefficient of friction between the lower surface of the workpiece to contact and the upper surface of the face plate tends to be small. Therefore, for example, when a large force exceeding the attraction force (magnetic attraction force) for fixing the workpiece is applied to the workpiece during grinding of the workpiece, the workpiece may be shifted from the initial position on the face plate. . On the other hand, it is conceivable to increase the amount of current flowing through the coil or increase the number of turns of the coil to improve the attracting force on the workpiece and improve the holding force on the workpiece. However, when increasing the amount of current flowing through the coil, there is a problem that the amount of heat generation increases. Further, when increasing the number of turns of the coil, there is a problem that the size of the electromagnetic chuck becomes large.

  The present invention has been made in view of such circumstances, and provides a compact electromagnetic chuck capable of fixing a workpiece with a sufficient holding force during machining, and a composite grinding machine including the electromagnetic chuck. For the purpose.

To solve the above problem, an electromagnetic chuck according to claim 1 is provided with a groove outer shape Ru formed between the magnetic pole magnetic pole portions and the adjacent face plate upper surface of the circular, the magnetic pole by a magnetic force of the magnetic pole portion An electromagnetic chuck body for adsorbing and fixing a workpiece on the upper surface of the workpiece, and the groove portion, and when the workpiece is fixed to the upper surface of the magnetic pole portion, A pressing member that presses the workpiece in a direction opposite to the suction direction by the magnetic pole portion with a force smaller than the suction force to the workpiece, and the magnetic pole portion of the face plate is arranged alternately with the groove portion. Arranged at equal intervals in the circumferential direction around the axis, and when magnetized, S poles and N poles are alternately formed in the circumferential direction, and the pressing member is formed of a non-magnetic material, and the lower surface of the workpiece. And the outermost member that contacts the An elastic body that is formed of a non-magnetic material and is disposed between the outermost surface member and the bottom surface of the groove, and biases the outermost surface member toward the lower surface of the workpiece. Is formed of a high friction material in which the friction coefficient between the outermost member and the lower surface of the workpiece is larger than the friction coefficient between the upper surface of the magnetic pole part and the lower surface of the workpiece .

  In this way, the pressing member is disposed in the groove formed on the upper surface of the face plate, and the pressing member presses the workpiece against the lower surface of the workpiece in the direction opposite to the suction direction. At this time, the force with which the pressing member presses the lower surface of the workpiece is smaller than the attracting force of the magnetic pole portion on the workpiece. For this reason, the electromagnetic chuck attracts the workpiece onto the face plate by magnetic force and maintains the force for fixing the workpiece, while applying the friction force generated by the pressing member pressing the lower surface of the workpiece. it can. As a result, in addition to the frictional force between the lower surface of the workpiece and the face plate of the electromagnetic chuck, the frictional force between the lower surface of the workpiece and the pressing member is added. Well maintained.

In order to solve the above problem, the composite grinding machine according to claim 4 is provided on a turning table capable of turning around a turning axis and on a circumference around the turning axis of the turning table, and the turning A plurality of spindle stock having a work spindle that can rotate around a spindle parallel to the axis, a plurality of holding devices that are provided on the plurality of work spindles and each can hold a workpiece, and the swivel table Each of the workpieces is provided so as to be relatively movable, and when the workpiece is sequentially transferred by turning of the turning table, the corresponding workpiece is ground when the workpiece is positioned at the corresponding grinding turning position. And the holding device is the above-described electromagnetic chuck.

  As described above, by applying the electromagnetic chuck to the holding device of the composite grinding machine in which the grinding of the inner ring and the outer ring is continuously performed, the workpiece can be stably ground without being displaced on the face plate during processing. . Thereby, the processing accuracy of the inner ring and the outer ring is improved.

It is the schematic which shows the whole structure of the composite grinding machine which concerns on this embodiment. It is a top view of the turning table with which the composite grinding machine of FIG. 1 is provided. It is EE arrow sectional drawing of the turning table of FIG. It is a perspective view of an electromagnetic chuck. It is a top view of an electromagnetic chuck. FIG. 6 is a cross-sectional view of the electromagnetic chuck of FIG. 5 taken along the line FF in a state where the workpiece is fixed. It is a 1st figure explaining the state of a compound grinder. It is a 2nd figure explaining the state of a compound grinder. It is a 3rd figure explaining the state of a compound grinder. It is a 4th figure explaining the state of a compound grinder. It is a 5th figure explaining the state of a compound grinder. It is a 6th figure explaining the state of a compound grinder. It is a 7th figure explaining the state of a compound grinder. FIG. 6 is a cross-sectional view of the electromagnetic chuck of FIG. 5 taken along the line FF in a state where the workpiece is not fixed.

(1. Configuration of composite grinding machine)
Hereinafter, each holding device 61, 62, 63, 64 corresponding to the electromagnetic chuck according to the present invention is a composite grinding machine 1 that performs plural types of grinding on the outer ring Wa and the inner ring Wb of the bearing, which is the workpiece W, by one unit. The case where it applies to is demonstrated. In FIG. 1, the direction orthogonal to the horizontal plane is defined as the X axis direction and the Y axis direction, and the direction orthogonal to the X axis direction and the Y axis direction is defined as the Z axis direction. As shown in FIG. 1, the composite grinding machine 1 includes a bed 2. On the bed 2, a swivel table 5, columns 3 a, 3 b, 3 c, and a Zd parallel to the Z-axis direction by an unillustrated drive mechanism. A swivel arm 3d that can swivel about an axis.

  The turning table 5 is configured to be turnable about a C axis (swivel axis) parallel to the Z axis direction by a drive mechanism 51 shown in FIG. As shown in FIGS. 1 and 2, the rotating table 5 includes four holding devices 61 to 64 (electromagnetic chucks, which will be described in detail later) at equal angular intervals (90 on the same circumference around the C axis. Degree intervals). As shown in FIG. 3, spindle stocks 81 to 84 are attached to the holding devices 61 to 64 (however, only the holding device 61 and the spindle stock 81 are shown as representatives in FIG. 3). Here, the holding devices 61 to 64 are the same device, and the headstocks 81 to 84 are also the same headstock. The headstock 81 includes a main spindle body 811 and a work spindle 812. The work spindle 812 is provided so as to protrude from the upper end of the spindle body 811 so as to be rotatable about a G axis (main axis) parallel to the C axis direction by a drive mechanism (not shown) built in the spindle body 811. A holding device (the holding device 61 is shown in FIG. 3) is fixed to the upper end of the work spindle 812.

  Through-holes 52 are formed in the turntable 5 on which the holding devices 61 to 64 are arranged. The spindle body 811 of the headstock 81 is fixed to the back surface of the turntable 5 corresponding to each through hole 52, and the work spindle 812 of the headstock 81 is inserted into each through hole 52. Each holding device 61 to 64 attracts the outer ring Wa or the inner ring Wb (workpiece W) by magnetic force and holds it on the upper surface of the face plate, and rotates around the G axis along with the work spindle 812.

  The outer ring Wa or the inner ring Wb is carried into a holding device (the holding device 61 in the state of FIG. 2 is replaced by turning of the turning table 5. The same applies hereinafter) located on the left side on the paper surface of FIG. 2 is carried out from the holding device (the holding device 64 in the state of FIG. 2 is replaced by turning of the turning table 5. The same applies hereinafter) located on the lower side on the paper surface of FIG. The outer ring Wa or the inner ring Wb is carried in and out by a robot (not shown). The robot is configured to be able to carry the outer ring Wa or the inner ring Wb in a state where the center axis of the outer ring Wa or the inner ring Wb is aligned with the rotation center of the holding device 61. The outer ring Wa or the inner ring Wb may be carried in and out by an operator, and the center alignment in that case is performed using a jig or the like.

  Although details will be described later, the turning table 5 turns at a predetermined angle clockwise in FIG. 2 to convey the outer ring Wa or the inner ring Wb. In FIG. 2, the holding device 61 located on the left side performs outer peripheral surface grinding when the workpiece W to be loaded is the outer ring Wa. Further, when the work W to be loaded is an inner ring Wb, inner peripheral surface grinding is performed. In the holding device 62 located on the upper side, outer ring raceway groove surface grinding, which is grinding with respect to the raceway groove WaG provided on the inner peripheral surface of the outer ring Wa, is performed.

  Further, in the holding device 63 located on the right side, inner ring raceway groove surface grinding that is grinding with respect to the raceway groove WbG provided on the outer peripheral surface of the inner ring Wb is performed. In the holding device 64 positioned on the lower side, the outer ring raceway surface superfinishing grinding performed on the raceway groove WaG of the outer ring Wa or the inner ring raceway surface superfinishing grinding performed on the raceway groove WbG of the inner ring Wb. Is carried out. In the following description, in the turning table 5, the left position is the peripheral grinding position Pp, the upper position is the outer ring grinding position Po, the right position is the inner ring grinding position Pi, and the lower position. Is referred to as a superfinishing grinding position Pb.

  The columns 3a, 3b, 3c can be reciprocated (advanced / retracted) in the Xa axis direction, Xb axis direction, and Xc axis direction parallel to the X axis direction by a driving mechanism (only the driving mechanism 3A of the column 3a is shown in FIG. 1). Configured. As shown in FIG. 1, the side surfaces of the columns 3a, 3b, 3c are moved up and down (advanced / retracted) by drive mechanisms 41a, 41b, 41c in the Za axis direction, Zb axis direction, and Zc axis direction parallel to the Z axis direction, respectively. ) Possible grindstone stands 4a, 4b, 4c are provided. Each of the grinding wheel bases 4a, 4b, 4c is a rotary type that can be driven to rotate around the Za axis (grinding wheel axis), the Zb axis (grinding wheel axis), and the Zc axis (grinding wheel axis) by drive mechanisms 91a, 91b, 91c, respectively. Grinding wheels 9a, 9b, 9c. Each grinding wheel 9a, 9b, 9c is held at the lower end of a holding shaft 92a, 92b, 92c extending downward.

  The columns 3a, 3b, and 3c are arranged on the bed 2 so that the grinding wheels 9a, 9b, and 9c can advance and retreat with respect to the circumferential grinding position Pp, the outer ring grinding position Po, and the inner ring grinding position Pi, respectively. The For the grinding wheel 9a, for example, a CBN (Cubic Boron Nitride) grinding wheel is used for grinding the outer peripheral surface of the outer ring Wa or the inner peripheral surface of the inner ring Wb. For the grinding wheels 9b and 9c, for example, an alumina grinding wheel is used for grinding the outer ring raceway groove surface of the outer ring Wa and the inner ring raceway surface grinding of the inner ring Wb.

  The swivel arm 3d includes a monolithic grindstone 9d that can be moved up and down in the Ze axis direction parallel to the Z axis direction by a drive mechanism (not shown) and that can rotate about the Ze axis (grinding stone axis line). The grindstone 9d is held on the peripheral surface of the lower end portion of the holding shaft 92d extending downward from the tip of the turning arm 3d so that the grinding portion of the grindstone 9d faces a direction perpendicular to the Ze axis. For the grindstone 9d, for example, a CBN grindstone is used to perform outer ring raceway surface super-finish grinding of the outer ring Wa or inner ring raceway surface super-finish grinding of the inner ring Wb. Note that a rotary grinding wheel may be used instead of the single stone grinding wheel 9d.

(2. Electromagnetic chuck)
Next, the holding devices 61 to 64 that are electromagnetic chucks according to the present invention will be described with reference to FIGS. As shown in FIGS. 4 to 6, the holding devices 61 to 64 include an electromagnetic chuck main body 170 and a pressing member 180. Although the holding devices 61 to 64 include electromagnetic coils and the like, since they are well-known, detailed description of the configuration and operation thereof will be omitted.

  The electromagnetic chuck main body 170 is formed in a bottomed cylindrical shape, for example, of an iron-based magnetic material with the face plate 171 as a bottom portion facing upward. As shown in FIGS. 4 to 6, the upper surface of the face plate 171 includes a magnetic pole part 172 and a groove part 173. In the present embodiment, the eight magnetic pole portions 172 formed in a fan shape are arranged at equal intervals in the circumferential direction around the G axis (main axis) of the face plate 171. The top surface heights of the eight magnetic pole portions 172 are all the same. Hereinafter, the upper surface of the magnetic pole portion 172 is referred to as a holding surface 172a. When the eight magnetic pole portions 172 are magnetized, an S pole and an N pole are sequentially formed in the circumferential direction (see FIG. 5). And the groove part 173 is formed by the recessed part between the adjacent magnetic pole parts 172.

  As shown in FIG. 5, the width of the groove 173 is formed so as to increase from the center (G axis) of the face plate 171 toward the outer periphery. The width of the groove 173 may be parallel from the center (G axis) of the face plate 171 toward the outer periphery. The width of the groove 173 may be formed so as to be reduced from the center (G axis) of the face plate 171 toward the outer periphery. Further, the number of the magnetic pole portions 172 and the groove portions 173 may be less than 8 or more than 8.

  As shown in FIG. 6, the groove 173 includes side surfaces 173a and 173a and a bottom surface 173b. As described above, the groove portion 173 is formed radially along the side surface of the magnetic pole portion 172 from the center (G axis) of the face plate 171 toward the outer periphery. The groove 173 has a constant distance from the top surface of the magnetic pole portion 172 to the bottom surface 173b, that is, the depth from the top surface of the magnetic pole portion 172, over the entire length of the face plate 171 in the radial direction. Since the portion surrounded by the groove 173 is a space, it is a nonmagnetic region.

  The magnetic pole portion 172 is magnetized by energizing a coil (not shown) wound around the magnetic pole steel (not shown) in the electromagnetic chuck body 170. As a result, the workpiece W placed so that the bottom surface is brought into close contact with the holding surface 172a (upper surface) of each magnetic pole portion 172 is attracted and fixed to the holding surface 172a by magnetic force (see FIG. 6). .

  The pressing member 180 is formed of a nonmagnetic material and is disposed in the groove portion 173. When the workpiece W is attracted and fixed to the holding surface 172a of the magnetic pole portion 172 by magnetic force, the pressing member 180 is applied to the workpiece W by the magnetization of the magnetic pole portion 172 with respect to the lower surface of the workpiece W. The workpiece W is pressed in the direction opposite to the attracting direction with a pressing force Fg smaller than the attracting force Fmag (magnetic attractive force) (Fmag> Fg). Specifically, the pressing member 180 includes an outermost surface member 181, a support body 182, and N springs 183 (elastic bodies), and the workpiece is obtained by summing up reaction forces of the compressed springs 183. Press W in the direction opposite to the suction direction. That is, the pressing force Fg is equal to the pressing force fg × N of one spring 183 (Fg = fg × N). In FIG. 5, five springs 183 are arranged from the center of the face plate 171 toward the outer periphery.

  The outermost surface member 181 is a member that is formed of a non-magnetic material and contacts the lower surface of the workpiece W. For example, the outermost surface member 181 is formed by mixing abrasive grains having a predetermined particle diameter with epoxy resin. Specifically, in the outermost surface member 181, the friction coefficient μ2 between the outermost surface member 181 and the lower surface of the workpiece W is larger than the friction coefficient μ1 between the holding surface 172 a of the magnetic pole portion 172 and the lower surface of the workpiece W. It is formed by a large high friction material (μ1 <μ2).

  The support 182 is formed of a nonmagnetic material such as SUS304 or SUS316, for example. The support body 182 is interposed between the outermost surface member 181 (high friction material) and the spring 183. The support body 182 is formed of a high hardness material having higher hardness than the outermost surface member 181 (high friction material). By arranging in this way, direct contact between the outermost surface member 181 and the spring 183 can be avoided, and wear of the outermost surface member 181 by the spring 183 can be effectively prevented. When the support body 182 is fitted in the groove portion 173, the support body 182 is formed such that there is almost no gap between the side surfaces 182a and 182a of the support body 182 and the side surfaces 173a and 173a of the groove portion 173. However, the size of the gap at this time is ensured so that at least the support 182 can move in the vertical direction in FIG. 6 within the groove 173. The material of the support 182 is not limited to a metal such as SUS304 or SUS316, and may be formed of a resin having a hardness higher than that of the outermost surface member 181.

  The spring 183 (elastic body) is formed of, for example, a nonmagnetic material such as SUS304 or SUS316. In the present embodiment, the spring 183 is a plurality (N) of leaf springs including wave washers. As described above, the necessary number (N) of the springs 183 is disposed between the support 182 and the bottom surface 173b (corresponding to the space between the outermost surface member 181 and the bottom surface 173b of the groove portion 173), and the workpiece When W is fixed to the holding surface 172a of the magnetic pole portion 172, the outermost surface member 181 is urged toward the lower surface of the workpiece W with a pressing force Fg (= fg × N).

  As shown in FIG. 1, the composite grinding machine 1 includes a control device 30. As a functional configuration of the control device 30, the feed control of the columns 3 a, 3 b, 3 c, the grindstone tables 4 a, 4 b, 4c elevation control, turning table 5 turning control, rotation of spindle heads 81-84 and holding device 61-64 suction control, grinding wheel 9a, 9b, 9c rotation control, turning arm 3d turning Control of rotation and elevation of the grindstone 9d and recording of data and programs are performed. The control device 30 can perform a plurality of grinding steps by controlling each device based on preset control data.

(3. Operation of composite grinding machine)
Next, grinding of the outer ring Wa of the bearing, outer ring raceway surface grinding, outer ring raceway surface superfinishing grinding, inner ring Wb inner circumference surface grinding, inner ring raceway surface grinding, and inner ring raceway as grinding of a plurality of types of workpieces W The operation of the composite grinding machine 1 that performs surface superfinish grinding will be described with reference to FIGS. 2 and 7A to 7G. Here, in the composite grinding machine 1, the state in which the holding device 61 is positioned at the circumferential grinding position Pp (the state shown in FIGS. 2 and 7A) is set as an initial state, and the turning position of the turning table 5 at this time is used as a reference. The position is 0 degree.

  First, the control device 30 sucks and fixes the first outer ring Waa to the holding surface 172a of the magnetic pole portion 172 of the holding device 61 by magnetic attraction (magnetic attraction) (see FIG. 7A). Then, the control device 30 controls the outer peripheral surface grinding of the outer ring Waa based on the outer peripheral surface grinding program (see FIG. 7A).

  At this time, in order to grind the outer peripheral surface of the outer ring Waa, the grindstone 9a is pressed against the outer peripheral surface of the outer ring Waa. Accordingly, the outer ring Waa receives a large grinding resistance in the normal direction and the tangential direction at the contact point with the grindstone 9a. The holding device 61 needs to be fixed so that the outer ring Waa does not move on the face plate (holding surface 172a) even when the outer ring Waa receives such a large grinding resistance from the grindstone 9a. An object of the present invention is to generate a large fixing force (adsorption force) in the holding device 61 so that the outer ring Waa does not move on the face plate in such a case. The outer ring Wa or the inner ring Wb is also the same as described above in each grinding on the inner circumferential surface of the outer ring Wa and each raceway groove surface, or in each grinding on the outer circumferential surface, inner circumference surface, and each raceway groove surface of the inner ring Wb. Each wheel receives a large grinding resistance. Therefore, the holding devices 61 to 64 generate a sufficient fixing force (adsorption force) so that the outer ring Wa or the inner ring Wb does not move on the face plates of the holding devices 61 to 64 even when receiving such grinding resistance. Objective. The details of fixing the outer ring Wa or the inner ring Wb to the holding devices 61 to 64 by the magnetic attractive force according to the present invention will be described in detail later.

  Next, when the outer peripheral surface grinding of the outer ring Waa is completed, the control device 30 turns the turning table 5 by 90 degrees (see FIG. 7B). Thereby, the holding device 61 is positioned at the outer ring grinding position Po, and the holding device 64 is positioned at the circumferential surface grinding position Pp. Then, the control device 30 attaches the first inner ring Wba to the holding device 64 (see FIG. 7C). Also at this time, like the outer ring Waa in the holding device 61, the inner ring Wba is fixed to the holding surface 172a of the magnetic pole portion 172 of the holding device 64 by a magnetic attraction force (magnetic attraction force).

  Then, the control device 30 controls the inner circumferential surface grinding of the inner ring Wba based on the inner circumferential surface grinding program, and also controls the outer ring raceway groove grinding of the outer ring Waa based on the outer ring raceway groove surface grinding program (see FIG. 7C). . These controls are performed in parallel. In the following, the outer ring Wa or the inner ring Wb is fixed to the holding surface 172a of the magnetic pole portion 172 of the holding device 64 by the magnetic attraction force with respect to the holding devices 62 and 63.

  Next, when the inner peripheral surface grinding of the inner ring Wba and the outer ring raceway groove surface grinding of the outer ring Waa are completed, the control device 30 turns the turning table 5 by 180 degrees (see FIG. 7D). Thereby, the holding device 61 is positioned at the superfinishing grinding position Pb. The holding device 64 is positioned at the inner ring grinding position Pi, and the holding device 62 is positioned at the circumferential surface grinding position Pp. The holding device 63 is positioned at the outer ring grinding position Po in an empty state in which the outer ring Wa and the inner ring Wb are not attracted.

  Next, the control device 30 fixes the next outer ring Wab to the holding device 62 by magnetic force (see FIG. 7E). And the control apparatus 30 controls the outer peripheral surface grinding of the outer ring Wab based on an outer peripheral surface grinding program. Further, the control device 30 controls the inner ring raceway surface grinding of the inner ring Wba based on the inner ring raceway surface grinding program. Further, the control device 30 controls the outer ring raceway surface super finishing grinding of the outer ring Waa based on the outer ring super finishing grinding program (see FIG. 7E). These controls are performed in parallel.

  Further, the control device 30 turns the turning arm 3d, rotates and lowers the grindstone 9d, and contacts the grindstone 9d with the raceway surface of the outer ring Waa on the holding device 61 to perform super-finishing of the outer ring, thereby super-finishing the outer ring. After the grinding is completed, the grindstone 9d is retracted to the standby position. When the outer ring raceway surface superfinishing grinding of the outer ring Waa is completed, the control device 30 releases the magnetic attraction force of the holding device 61 and takes out the outer ring Waa from the holding device 61 (see FIG. 7E).

  Next, when the outer peripheral surface grinding of the outer ring Waa and the inner ring raceway groove surface grinding of the inner ring Wba are completed, the control device 30 turns the turning table 5 by 90 degrees (see FIG. 7F). As a result, the holding device 61 is positioned at the circumferential grinding position Pp, the holding device 62 is positioned at the outer ring grinding position Po, and the holding device 64 is positioned at the superfinishing grinding position Pb. The holding device 63 is positioned at the inner ring grinding position Pi in an empty state in which the outer ring Wa and the inner ring Wb are not attracted.

  Control device 30 fixes the next inner ring Wbb to holding device 61 by magnetic force (see FIG. 7G). The control device 30 controls the inner peripheral surface grinding of the inner ring Wbb based on the inner peripheral surface grinding program, and controls the outer ring raceway groove surface grinding (inner peripheral surface) of the outer ring Wab based on the outer ring raceway groove surface grinding program. Based on the inner ring raceway groove surface superfinishing grinding program, the inner ring raceway groove surface superfinishing grinding (outer peripheral surface) of the inner ring Wba is controlled (see FIG. 7G). These controls are performed in parallel.

  Next, the control device 30 retracts the grindstone 9d to the standby position after completing the inner ring super finishing of the inner ring Wba. And the control apparatus 30 cancels | releases the magnetic attraction force of the holding | maintenance apparatus 64, and takes out the inner ring | wheel Wba from the holding | maintenance apparatus 64 (refer FIG. 7G).

(4. Action of electromagnetic chuck)
Next, the operation of the holding devices 61 to 64 (electromagnetic chuck) will be described in detail. As a representative, a case will be described in which the outer ring Waa is attracted and fixed to the holding surface 172a of the magnetic pole portion 172 of the holding device 61 (electromagnetic chuck) by magnetic attraction (magnetic attraction).

  First, a state where the outer ring Waa is not placed on the holding surface 172a of the magnetic pole portion 172 will be described. As shown in FIG. 8, in the state where the outer ring Waa is not placed on the holding surface 172a of the magnetic pole portion 172, the outermost surface member 181, the support 182 and the spring 183 (elastic body) constituting the pressing member 180 are moved. It arrange | positions in the groove part 173 according to the above-mentioned. In the present embodiment, for example, five springs 183 are arranged in one groove 173 (see FIG. 5). Thereby, the outermost surface member 181 slightly protrudes upward from the opening of the groove 173 (see dimension L in FIG. 8). This is because the spring 183 is not compressed and is in a free height (free length) state. At this time, the dimension protruding from the opening of the groove 173 is, for example, on the order of several tens of μm. However, the present invention is not limited to this aspect, and the dimensions protruding from the opening of the groove 173 may be any number as long as the pressing member 180 is completely accommodated in the groove 173.

  Next, the magnetic pole portion 172 is magnetized by energizing a coil (not shown) wound around the steel for a magnetic pole (not shown). As a result, the bottom surface of the outer ring Waa is attracted by the magnetic force to the holding surface 172a of each magnetic pole portion 172, and the outer ring Waa is tightly fixed on each holding surface 172a (see FIG. 6).

  In a state where the outer ring Waa is fixed on the holding surface 172a of the magnetic pole portion 172, the lower surface of the outer ring Waa presses the upper surface of the outermost surface member 181 protruding upward from the opening of the groove portion 173 downward, and moves downward. Move. At this time, the upper surface of the outermost member 181 and the holding surface 172a have the same height. Accordingly, the spring 183 (elastic body) is pushed downward via the outermost surface member 181 and the support body 182 and is bent by a predetermined deflection amount δ (= L) in the compression direction. At this time, if the spring constant of one spring 183 is k, the pressing force fg per spring 183 is fg = kδ. Thereby, the N springs 183 arranged in total press the outer ring Waa in the direction opposite to the attracting direction with a pressing force Fg (= fg × N) as a reaction force deflected.

  At this time, the pressing force Fg is set to be a pressing force smaller than the attractive force Fmag to the outer ring Waa (workpiece W) due to the magnetization of the magnetic pole portion 172 (Fmag> Fg). For this reason, the pressing member 180 (the outermost surface member 181, the support 182, and the spring 183) is fixed to the holding surface 172 a of the outer ring Waa, so that the outermost surface member 181 contacts the lower surface of the outer ring Waa, It is securely pushed into the interior.

From the above, the frictional force F between the outer ring Waa (workpiece W) and the holding device 61 is obtained by the equation (1).
(Equation 1)
F = μ1 × (Fmag−N × fg) + μ2 × N × fg
F: Friction force between the outer ring Waa (workpiece W) and the holding device 61 μ1; Friction coefficient between the eight holding surfaces 172a (upper surface) of each magnetic pole portion 172 and the lower surface of the outer ring Waa Fmag: Magnetic pole portion Adsorption force μ2 on the outer ring Waa due to magnetization of 172; friction coefficient between the eight outermost surface members 181 and the lower surface of the outer ring Waa N; total number of springs 183 fg; pressing force per one spring 183 (spring load) (Fg = kδ)

  As can be seen from the above equation (1), when the attractive force Fmag changes, the total number N of the springs 183 is changed, or the springs constituting the pressing force fg (spring load) per one spring 183 What is necessary is just to respond | correspond by changing at least one of the constant k or bending amount (delta). Each numerical value is set so that the frictional force F is equal to or greater than a predetermined value. In addition, what is necessary is just to set the predetermined value of the frictional force F by experiment etc. beforehand.

  From the above, not only the holding device 61 but also the holding devices 62 to 64 having the same configuration as the holding device 61, the outer ring Waa (workpiece W) or the inner ring Wba (workpiece W) is the same as the holding devices 61 to 64. It is firmly fixed to each holding surface 172a of each magnetic pole portion 172 by a sufficient frictional force F. Thereby, since the workpiece W does not shift | deviate from the position initially arrange | positioned on the upper surface of the holding | maintenance apparatuses 61-64, each grinding | polishing can be performed accurately.

(5. Effect by embodiment)
As is clear from the above description, according to the above embodiment, the holding devices 61 to 64 (electromagnetic chucks) include the groove portion 173 formed between the magnetic pole portion 172 and the adjacent magnetic pole portion 172 on the upper surface of the face plate 171. . The magnetic chuck body 170 that attracts and fixes the workpiece W to the holding surface 172a of the magnetic pole portion 172 by the magnetic force of the magnetic pole portion 172 and the nonmagnetic material is disposed in the groove portion 173, and the workpiece W is disposed in the magnetic pole portion. When fixed to the upper surface of the workpiece 172, the workpiece W is applied to the lower surface of the workpiece W with a pressing force Fg (= fg × N) smaller than the attractive force Fmag (magnetic attractive force) of the magnetic pole portion 172 to the workpiece W. There is provided a pressing member 180 for pressing in the direction opposite to the suction direction.

  In this way, the pressing member 180 formed of a non-magnetic material is disposed in the groove portion 173 formed on the upper surface of the face plate 171, and the pressing member 180 opposes the workpiece W against the lower surface of the workpiece W in the attracting direction. Press in the direction. At this time, the pressing force Fg (= fg × N) at which the pressing member 180 presses the lower surface of the workpiece W is smaller than the attracting force Fmag to the workpiece W by the magnetic pole portion 172. For this reason, the holding members 61 to 64 (electromagnetic chucks) attract the workpiece W onto the face plate 171 by magnetic force, and the pressing member 180 presses the lower surface of the workpiece W while maintaining the force for fixing the workpiece W. Thus, the frictional force F generated can be applied. Therefore, in addition to the frictional force between the lower surface of the workpiece W and the face plate 171 of the holding devices 61 to 64 (electromagnetic chuck), the frictional force between the lower surface of the workpiece W and the pressing member 180 is added. Even during grinding, the workpiece W is satisfactorily held on the face plate 171.

Further, according to the above embodiment, the pressing member 180 protrudes upward from the opening of the groove portion 173 in a state where the workpiece W is not placed on the upper surface of the magnetic pole portion 172, and the workpiece W protrudes from the upper surface of the magnetic pole portion 172. In the state fixed to the groove portion 173, the groove portion 173 is accommodated.
Thereby, the lower surface of the workpiece W is pressed by the reaction force of the compressed pressing member 180, and a sufficiently large friction force F is generated between the lower surface of the workpiece W and the pressing member 180. As described above, when the workpiece W is not placed on the upper surface of the magnetic pole portion 172, the pressing member 180 protrudes upward from the opening of the groove portion 173, so that the lower surface of the workpiece W can be reliably pressed. A frictional force F can be generated between the member 180 and the member 180.

In addition, according to the above embodiment, the pressing member 180 is formed of a nonmagnetic material and is formed of the outermost surface member 181 that contacts the lower surface of the workpiece W, and is formed of a nonmagnetic material, and includes the outermost surface member 181 and the groove portion 173. A spring 183 (elastic body) disposed between the bottom surface 173b and urging the outermost surface member 181 toward the lower surface of the workpiece W.
Thereby, the pressing force of the pressing member 180 can be easily adjusted by changing the specifications and the number of the springs 183.

  Further, according to the above embodiment, the outermost surface member 181 has a friction coefficient μ2 between the outermost surface member 181 and the lower surface of the workpiece W so that the friction between the upper surface of the magnetic pole part 172 and the lower surface of the workpiece W is the same. It is formed of a high friction material larger than the coefficient μ1. Thereby, a large frictional force F can be easily obtained between the workpiece W and the face plate 171.

  Further, according to the above-described embodiment, the elastic body is the spring 183, and the pressing member 180 is formed of a non-magnetic body, and is interposed between the high friction material (outermost surface member 181) and the spring 183, and has a high height. A support body 182 formed of a material harder than the friction material (outermost surface member 181) (eg, SUS304) is provided. Thereby, it is possible to prevent the high friction material (outermost surface member 181) from being worn by the spring 183.

  Further, according to the above embodiment, the composite grinding machine 1 is provided on the turning table 5 that can turn around the turning axis, and on the circumference around the turning axis in the turning table 5, and is parallel to the turning axis. A plurality of spindle stocks 81 to 84 having work spindles 812 to 842 (work spindles 822, 832, and 842 are not shown) rotatable around the spindle and work spindles 812 to 842, respectively, for holding the workpiece W Can be moved relative to the swivel table 5, and the workpieces W are sequentially conveyed by the swivel of the swivel table 5. A plurality of grindstones for grinding the corresponding workpiece W when the workpiece W is positioned, and the holding devices 61 to 64 are the above-described electromagnetic chucks.

  In this way, by applying the electromagnetic chuck according to the present invention to the holding devices 61 to 64 of the composite grinding machine 1 in which a large number of grindings of the inner ring and outer ring of the bearing are continuously performed, the grinding resistance is reduced on the XY axis plane. The workpiece W to be received can be stably ground without being displaced on the face plate 171 during processing. Thereby, the processing accuracy of the inner ring Wb and the outer ring Wa is improved. In addition, when a plurality of parts that require machining accuracy (parts that are combined to form a product) are simultaneously machined as the workpiece W, machining efficiency is also improved (such as ball bearings, plain bearings, etc. as the workpiece W). When bearings and other combination products are applied).

(6. Others)
In the above embodiment, the holding devices 61 to 64 (electromagnetic chucks) according to the present invention are applied to the composite grinding machine 1, but the present invention is not limited to this mode. The holding devices 61 to 64 may be applied as holding devices for any processing machine. Moreover, you may use for not only a processing machine but what kind of apparatus as a fixing tool which fixes components. The same effect can be expected by these.

  Moreover, in the said embodiment, the outermost surface member 181 demonstrated that the abrasive grain of a predetermined particle size was mixed with an epoxy resin, for example. However, it is not limited to this aspect. The outermost surface member 181 is formed of a non-magnetic material, and the friction coefficient μ2 between the outermost surface member 181 and the lower surface of the workpiece W is a friction between the holding surface 172a of the magnetic pole portion 172 and the lower surface of the workpiece W. Any high friction material greater than the coefficient μ1 may be used. For example, you may use the clutch board normally used for the transmission of a motor vehicle. Moreover, the thing which provided the unevenness | corrugation on the surface of various metal plates, and improved the friction coefficient may be used.

  Moreover, in the said embodiment, the magnetization of the magnetic pole part 172 of an electromagnetic chuck shall be implement | achieved by supplying with electricity to the coil (not shown) wound around the steel material for magnetic poles (not shown). However, it is not limited to this aspect. Magnetization of the magnetic pole portion 172 of the electromagnetic chuck may be realized by moving a permanent magnet (not shown) in the electromagnetic chuck main body 170. This also provides the same effect.

  DESCRIPTION OF SYMBOLS 1 ... Composite grinding machine, 2 ... Bed, 4a, 4b, 4c ... Grinding wheel base, 5 ... Turning table, 9a, 9b, 9c ... Grinding wheel, 9d ... Grinding wheel, 61 -64 ... Holding device (electromagnetic chuck), 170 ... Electromagnetic chuck body, 171 ... Face plate, 172 ... Magnetic pole part, 172a ... Upper surface (holding surface), 173 ... Groove part, 173a・ ・ ・ Side surface, 173b ・ ・ ・ bottom surface, 81 to 84 ・ ・ ・ headstock, 180 ・ ・ ・ pressing member, 181 ・ ・ ・ outmost surface member, 182 ・ ・ ・ support, 182a ・ ・ ・ side surface, 183 ・..Spring (elastic body), F ... friction force, Fg ... pressing force (force), Fmag ... adsorption force (magnetic attraction force), k ... spring constant, N ... number, W: Workpiece, δ: Deflection, μ1, μ2: Friction .

Claims (5)

An electromagnetic chuck body outer shape comprises a groove that will be formed between the magnetic pole magnetic pole portions and the adjacent face plate upper surface of the circular, it adsorbs to secure the workpiece by the magnetic force of the magnetic pole portion on the upper surface of the magnetic pole portions,
When the workpiece is fixed to the upper surface of the magnetic pole portion and disposed in the groove portion, the workpiece is applied to the lower surface of the workpiece with a force smaller than the attracting force of the magnetic pole portion to the workpiece. A pressing member that presses in a direction opposite to the attracting direction by the magnetic pole part ,
The magnetic pole portions are arranged at equal intervals in the circumferential direction around the axis of the face plate so as to be alternately arranged with the groove portions, and when magnetized, S poles and N poles are alternately formed in the circumferential direction,
The pressing member is
An outermost member formed of a non-magnetic material and in contact with the lower surface of the workpiece;
An elastic body formed of a non-magnetic material, disposed between the outermost surface member and the bottom surface of the groove, and biasing the outermost surface member toward the lower surface of the workpiece;
The outermost surface member is formed of a high friction material in which a friction coefficient between the outermost surface member and the lower surface of the workpiece is larger than a friction coefficient between the upper surface of the magnetic pole part and the lower surface of the workpiece. The electromagnetic chuck. The pressing member is
In a state where the workpiece is not placed on the top surface of the magnetic pole part, it protrudes upward from the opening of the groove part,
The electromagnetic chuck according to claim 1, wherein the workpiece is accommodated in the groove portion in a state where the workpiece is fixed to an upper surface of the magnetic pole portion. The elastic body is a spring;
The pressing member is formed of a nonmagnetic material, interposed between the spring and the high friction material comprises a support body formed by a high hardness material than the high friction material according to claim 1 or 2 Electromagnetic chuck. A swivel table capable of swiveling around a swivel axis;
A plurality of headstocks each having a work spindle that is provided on a circumference around the swivel axis in the swivel table and is rotatable about a main axis parallel to the swivel axis;
A plurality of holding devices provided on the plurality of work spindles, each capable of holding a workpiece;
Corresponding to the case where the workpiece is positioned at each of the corresponding grinding turning positions by sequentially moving the workpiece by turning the turning table. A plurality of grindstones for grinding the workpiece;
With
The composite grinding machine, wherein the holding device is the electromagnetic chuck according to any one of claims 1 to 3 . The face plate of the electromagnetic chuck is disposed such that the axis coincides with the main axis of the headstock,
The workpiece includes an inner peripheral surface and an outer peripheral surface and is formed in a ring shape, and is fixed to the upper surface of the face plate so that a center axis coincides with the main axis
5. The composite grinding machine according to claim 4, wherein the grindstone is pressed against the inner peripheral surface or the outer peripheral surface of the workpiece rotating around the central axis to grind the inner peripheral surface or the outer peripheral surface .

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