JP4998078B2 - Grinding machine and grinding method for non-circular or eccentric workpiece - Google Patents

Description

  The present invention relates to a grinding machine for grinding a non-circular or eccentric work and a grinding method thereof.

Examples of conventional non-circular or eccentric workpieces as grinding machines include those described in Japanese Utility Model Laid-Open No. 5-93757 (Patent Document 1) and Japanese Patent Laid-Open No. 10-156692 (Patent Document 2). . The grinding machine described in Patent Document 1 determines whether or not the workpiece material shape matches the shape of the machining program by bringing the touch sensor into contact with the workpiece material before grinding. The grinding process is started only when they match. In addition, the grinding machine described in Patent Document 2 measures the external dimension of a workpiece with a sizing device including a pair of measuring elements, and corrects machining data based on the measurement result.
Japanese Utility Model Publication No. 5-93757 Japanese Patent Laid-Open No. 10-156692

  It is also conceivable to correct the machining data based on the measurement result described in Patent Document 1. Here, in the measurement described in Patent Document 1, the touch sensor is attached to the grindstone platform, and the workpiece is attached to the main shaft. Therefore, when a thermal displacement occurs between the main spindle and the grindstone platform, the measurement result by the touch sensor is shifted. For this reason, highly accurate correction cannot be performed. Further, according to the sizing device described in Patent Document 2, even if a thermal displacement occurs between the main spindle and the grindstone table, it is not affected by the sizing device, so that highly accurate correction is possible. However, the sizing device is very expensive.

  The present invention has been made in view of such circumstances, and provides a grinding machine and a grinding method capable of performing high-precision correction even when thermal displacement occurs using an inexpensive apparatus. Objective.

<Grinding machine>
The grinding machine of the present invention supports a non-circular or eccentric workpiece rotatably supported around a spindle central axis, and supports a grindstone rotatably around a grinding wheel axis parallel to the spindle central axis. A grindstone base that is relatively movable in a direction orthogonal to the central axis of the spindle, a touch sensor that is attached to the grinding wheel base, a reference member that has a reference surface disposed at a predetermined reference distance from the central axis of the spindle, and a reference in advance A reference distance storage unit for storing the distance, and in a direction orthogonal to the spindle central axis of the spindle and the grindstone base when the grinding process is interrupted during grinding of one workpiece and the touch sensor is brought into contact with the reference surface The difference between the first relative position and the second relative position in the orthogonal direction of the spindle central axis between the spindle and the grindstone base when the touch sensor is brought into contact with a predetermined measurement point in the grinding part of the workpiece is calculated. The difference calculation unit and the reference distance One workpiece is ground by correcting the machining data of the workpiece based on the difference and the rotation angle of the spindle and the relative position of the spindle and the grindstone table based on the machining data corrected by the compensation portion. And a control unit that resumes machining.

  In the grinding machine of the present invention, when there is no processing error due to thermal displacement or grinding wheel wear, the difference between the reference distance from the spindle central axis to the reference surface and the design value at the grinding part of the workpiece is the first It corresponds to the difference between the relative position and the second relative position. Here, the reference distance from the main axis central axis to the reference plane is stored in advance. In other words, this reference distance is completely unrelated to the thermal displacement of the grinding machine and the workpiece, that is, not affected by the thermal displacement of the grinding machine and the workpiece. The design value at the workpiece grinding portion corresponds to the dimension at the workpiece grinding portion obtained from the uncorrected machining data. Therefore, the difference between the reference distance from the central axis of the spindle to the reference surface and the design value at the workpiece grinding part is known. On the other hand, the first relative position and the second relative position are measured by bringing the touch sensor into contact with the corresponding part.

  And in the grinding machine of this invention, the touch sensor for measuring a 1st relative position and a 2nd relative position is attached to the grindstone base. Therefore, when thermal displacement occurs between the spindle and the grindstone platform, the measurement result itself by the touch sensor is affected by the thermal displacement, as in Patent Document 1. That is, each of the first relative position and the second relative position measured by the touch sensor is affected by thermal displacement. However, the difference between the first relative position and the second relative position, i.e., the difference between those affected by the thermal displacement, is almost eliminated from the influence of the thermal displacement. In other words, the difference between the first relative position and the second relative position is the same value whether or not thermal displacement occurs between the spindle and the grindstone platform. It becomes.

  As described above, the reference distance from the main axis to the reference plane and the difference between the first relative position and the second relative position are all unaffected by thermal displacement. Therefore, in the grinding machine according to the present invention, if there is no processing error due to thermal displacement or grinding wheel wear, from the spindle central axis to the reference plane regardless of whether thermal displacement occurs during measurement. The difference between the reference distance and the design value at the grinding part of the workpiece coincides with the difference between the first relative position and the second relative position.

  On the other hand, when there is a processing error due to thermal displacement, grinding wheel wear, or the like, the actual dimension of the workpiece grinding part is deviated from the design value of the workpiece grinding part. In this case, the difference between the reference distance from the spindle central axis to the reference surface and the design value at the grinding portion of the workpiece does not match the difference between the first relative position and the second relative position. Here, as described above, the difference between the first relative position and the second relative position is a case where no thermal displacement occurs even when thermal displacement occurs between the spindle and the grindstone base. Even if it exists, it becomes the same value. Therefore, the amount of difference between the two differences does not change even when thermal displacement occurs or when no thermal displacement occurs.

  Then, by correcting the amount of deviation between the two differences in the correction unit of the present invention, the actual dimension of the workpiece grinding portion can be made to match the design value. In other words, by calculating the correction amount based on the reference distance from the spindle central axis to the reference plane that is not affected by the thermal displacement and the difference between the first relative position and the second relative position, the spindle and the grinder base Even if there is a thermal displacement between the two, the correction amount can be prevented from being affected by the thermal displacement. Then, the machining data is corrected based on the correction amount. Therefore, highly accurate grinding can be performed. Further, the grinding machine of the present invention uses a touch sensor attached to a grindstone table for measurement, and is very inexpensive as compared with a sizing device.

  In the grinding machine of the present invention, the reference member may be provided on the workpiece, or may be provided on, for example, a spindle stock, a tailstock, or a bed. In particular, the reference member is preferably provided on the workpiece. In this case, the separation distance between the reference surface of the reference member and the predetermined measurement point in the ground portion of the workpiece can be shortened. Therefore, after the touch sensor is brought into contact with the reference surface of the reference member, the time until the touch sensor is brought into contact with a predetermined measurement point in the ground portion of the workpiece can be shortened. If the time until the touch sensor is brought into contact with a predetermined measurement point in the ground portion of the workpiece after the touch sensor is brought into contact with the reference surface of the reference member is long, thermal displacement may occur during that time. Then, the difference between the first relative position and the second relative position is affected by the thermal displacement. Therefore, by providing the reference member on the workpiece and shortening the time for the touch sensor to move between the two contact positions, it is possible to suppress the influence of the thermal displacement that occurs when the touch sensor moves between the two contact positions. That is, more accurate grinding can be performed.

  Furthermore, by providing the reference member on a member that is arranged across the central axis of the spindle like a workpiece, the following effects can be obtained when thermal displacement (thermal expansion) occurs in the reference member itself. When the reference member is provided on the work, the center line of the work including the reference member coincides with the central axis of the main shaft. Then, the reference member is provided on the touch sensor side and the opposite side of the touch sensor across the main axis. For this reason, when thermal displacement (thermal expansion) occurs in the reference member itself, the work including the reference member has the touch sensor side portion and the touch sensor opposite side portion equally spaced from the central axis of the spindle. Thermal expansion will occur. Accordingly, the distance from the central axis of the main shaft to the reference plane is half of the thermal expansion of the entire workpiece. On the other hand, when the reference member is provided on the headstock, for example, if the reference member itself is thermally expanded, the reference member is directly affected by the thermal expansion. As described above, by providing the reference member on the workpiece, when the reference member itself is thermally expanded, the influence can be reduced.

  Here, since the predetermined measurement point in the grinding part of the workpiece abutted by the touch sensor has a non-circular shape or an eccentric shape, a better position is often specified in the grinding part. In that case, it is necessary to determine the rotation angle of the main shaft in order to bring the touch sensor into contact with a predetermined measurement point in the grinding portion of the workpiece.

  In this case, in the grinding machine according to the present invention in which the reference member is provided on the workpiece, the workpiece has a non-round shape or an eccentric shape to be ground and a central axis coaxially positioned with the central axis of the main shaft. It is preferable that the reference member is a journal part, and the reference surface is an outer peripheral surface of the journal part.

  As a result, the reference surface may be anywhere on the outer peripheral surface of the journal portion. That is, for the reference plane, it is not necessary to determine the rotation angle of the spindle. In this case, before making contact with the touch sensor, the rotation angle of the spindle that can make contact with the touch sensor at a predetermined measurement point in the ground portion of the workpiece is calculated in advance. Thereafter, the touch sensor is brought into contact with the reference surface and a predetermined measurement point on the grinding portion of the workpiece. That is, by making the reference surface the outer peripheral surface of the journal portion, it is not necessary to rotate the main shaft when the touch sensor moves between both contact positions. Therefore, in addition to the influence of the thermal displacement directly generated by rotating the main shaft, it is possible to prevent the influence of the thermal displacement caused by the extension of time by rotating the main shaft. As a result, more accurate grinding can be performed.

  Furthermore, by using the outer peripheral surface of the journal portion located at a position very close to the central axis of the spindle as the reference surface, even if the workpiece is affected by thermal displacement (thermal expansion), the influence can be minimized.

  Some of them have a plurality of journal portions, such as a camshaft and a crankshaft. Thus, when a workpiece | work is provided with a some journal part, it is preferable that a reference | standard member shall be the journal part nearest to the grinding | polishing target part among several journal parts. As a result, the time and amount of movement of the touch sensor between the two contact positions can be shortened. And when movement time and movement amount become long, there exists a possibility of receiving the influence of a thermal displacement. That is, since the movement time and the movement amount can be shortened, the influence of the thermal displacement caused by this can be suppressed.

  When the journal part and the grinding target part are close to each other, when the work is supported by the rest, both positions are affected to the same extent by the pushing margin by the rest. That is, the difference between the first relative position and the second relative position is hardly affected by the pushing margin due to the rest. As a result, when the journal part and the grinding target part are close to each other, it is possible to perform grinding with higher accuracy.

  Here, when the reference member is provided on the workpiece, the reference distance storage unit may store a reference distance measured in advance for each workpiece. Usually, there are slight differences between workpieces due to the effect of machining accuracy. Therefore, in a strict sense, the reference distance differs for each workpiece. That is, the difference between the first relative position and the second relative position differs for each workpiece. Therefore, by setting the reference distance stored in the reference distance storage unit in advance for each workpiece, the workpiece can be appropriately corrected for each workpiece, and as a result, highly accurate grinding can be performed. In addition to this, for example, when the machining accuracy of the work for each lot is stable, the reference distance may be measured at a rate of once per lot.

  However, it takes a lot of time to measure the reference distance in advance. Therefore, when the processing accuracy of the reference surface for each workpiece is always stable, the reference distance storage unit may store the tolerance center value of the design dimension of the reference distance. Thus, the reference distance can be determined without measuring the reference distance in advance for each workpiece. This is an effective means when the dimensional tolerance is sufficiently large.

  In the grinding machine of the present invention, it is preferable that the predetermined measurement point is a point that is ground by the grindstone when positioned on a plane passing through the spindle central axis and the grindstone axis among the grinding portions of the workpiece. That is, the tangent at the predetermined measurement point is orthogonal to the line segment connecting the central axis of the main axis and the predetermined measurement point. Here, grinding errors and measurement errors are unlikely to occur at the predetermined measurement points. Therefore, highly accurate correction is possible.

  In particular, the workpiece may have a shape having a base circle, and the predetermined measurement point may be a base circle. The base circle is ground by the grindstone when it is located on a plane passing through the main shaft central axis and the grindstone axis at any position. And when grinding a base circle part, it will be in the state where the grindstone was positioned. Therefore, the processing accuracy of the base circle is very stable. That is, it is possible to perform correction with higher accuracy by setting the base circle portion as the predetermined measurement point.

  Here, in a grinding machine equipped with the sizing device described in Patent Document 2, for example, in the case of a workpiece having a base circular portion having a range of 180 degrees or more, both of the pair of measuring elements contact the base circular portion. The base circle diameter can be measured. However, for a workpiece in which the base circle portion is less than 180 degrees, the diameter of the base circle cannot be measured by a pair of measuring elements, and is affected by a machining error of the lift amount. On the other hand, in the grinding machine of the present invention, even if the base circle is in a range of less than 180 degrees, it is possible to reliably contact the base circle by the touch sensor. Therefore, even with the grinding machine described in Patent Document 2, grinding can be performed with higher accuracy.

<Grinding method for non-circular or eccentric workpiece>
In the above, the case where this invention was grasped | ascertained as a grinding machine was demonstrated. In addition, the present invention can also be grasped as a grinding method for a non-circular or eccentric workpiece.

  That is, in the grinding method of the present invention, a non-circular or eccentric work piece is supported so as to be rotatable around the central axis of the spindle, and the grindstone is supported so as to be rotatable about a grindstone axis parallel to the central axis of the spindle. A grindstone base that is relatively movable in the direction orthogonal to the main spindle center axis with respect to the main spindle, a touch sensor attached to the grindstone stand, and a reference member that has a reference surface arranged at a predetermined reference distance from the main spindle central axis, A reference distance storing step for storing the reference distance in advance, and based on the machining data of one workpiece, the rotation angle of the spindle and the relative position between the spindle and the grindstone are controlled to grind one workpiece. First grinding step to be performed, and the first relative position in the orthogonal direction of the spindle central axis between the spindle and the grinding wheel head when the grinding process in the first grinding process is interrupted and the touch sensor is brought into contact with the reference surface , Workpiece grinding A difference calculating step for calculating a difference between the main axis and the second relative position in the orthogonal direction of the main axis of the grinding wheel head when the touch sensor is brought into contact with a predetermined measurement point, and a reference distance and a difference Based on the correction process for correcting the machining data based on the correction data, and controlling the rotation angle of the spindle and the relative position between the spindle and the grindstone table based on the machining data corrected in the correction process, the grinding of one workpiece is resumed. A second grinding step.

  Thereby, there exists the same effect as the effect which the grinding machine of the present invention mentioned above shows. That is, correction can be performed using a measurement result that can reduce the influence of thermal displacement using an inexpensive touch sensor. Further, the other characteristic portions of the above-described grinding machine of the present invention can be similarly applied to the grinding method of the present invention. The effect in this case also has the same effect as described above.

  Next, the present invention will be described in more detail with reference to embodiments.

<First embodiment>
The grinding machine of the first embodiment will be described by taking as an example a case where a camshaft is used as a workpiece and a cam portion of the camshaft is ground. The configuration of the grinding machine according to the first embodiment will be described with reference to FIG. FIG. 1 is a diagram showing the configuration of the grinding machine of the first embodiment. First, the camshaft W that is a workpiece will be described, and then the mechanical configuration of the grinding machine and the control block configuration of the grinding machine will be described.

  As shown in FIG. 1, the camshaft W has a long shaft shape, and includes a plurality of cam portions C1 to C4 (corresponding to “grinding target portions” in the present invention) and a plurality of journal portions J1 and J2. I have. Specifically, the journal portion J1 is located between the two left cam portions C1 and C2 in FIG. 1, and the journal portion J2 is located between the two right cam portions C3 and C4 in FIG. positioned.

  Here, the detailed shapes of the cam portions C1 to C4 and the journal portions J1 and J2 in the final product shape will be described with reference to FIG. FIG. 2 is a view of the cam portions C1 to C4 and the journal portions J1 and J2 as viewed from the axial direction (in the direction of the main shaft central axis O1). As shown in FIG. 2, the radial cross-sectional shape of the outer peripheral surfaces of the journal portions J1 and J2 is a circle having a radius Rj. That is, the journal parts J1 and J2 are formed in a cylindrical shape or a columnar shape. Each of the cam portions C1 to C4 includes a base circle portion B having a radius Rc and a protruding portion T having a distance from the center point larger than that of the base circle portion B. Here, the center of the base circle part B and the centers of the journal parts J1 and J2 coincide. Further, the radius Rc of the base circle portion B is larger than the outer peripheral surface radius Rj of the journal portions J1 and J2.

  Here, in the following, a grinding target portion to be ground by the grinding machine of the first embodiment is a cam portion C1. On the other hand, the journal portions J1 and J2 are already ground.

  Next, the mechanical configuration of the grinding machine will be described. As shown in FIG. 1, the mechanical configuration of the grinding machine is as follows: bed 1, table 2, Z-axis motor 3, spindle head 4, spindle motor 5, tailstock 6, rest 7, and grinding wheel base 8, an X-axis motor 9, a grindstone 10, a grindstone driving motor 11, and a touch sensor 12. Here, in the mechanical configuration of the grinding machine shown in FIG. 1, the left-right direction is the Z-axis direction, and the up-down direction is the X-axis direction.

  The bed 1 is installed on the floor surface. A table 2 is supported on the front side of this bed 1 (lower side in FIG. 1) so as to be movable in the Z-axis direction. The table 2 is moved by driving a Z-axis motor 3 attached to the bed 1. The headstock 4 is mounted on the left side of FIG. 1 on the table 2 and includes a main shaft 4a that can rotate around the center axis of the main shaft (around the Z axis). The rotation of the spindle 4 a is performed by driving a spindle motor 5 attached to the spindle stock 4.

  The tailstock 6 is placed on the right side of FIG. 1 on the table 2 so as to face the spindle stock 4. Then, both ends of the camshaft W are supported by the main shaft 4a and the tailstock 6 so that the central axes of the cam portions C1 to C4 and the central axes of the journal portions J1 and J2 are located coaxially with the main shaft central axis. ing. That is, the camshaft W is supported so as to be rotatable around the central axis of the main shaft that coincides with the central axis of the journal portion J1 or the like.

  The rest 7 is placed below the table 2 in FIG. 1 and supports the axial center of the camshaft W, specifically, the journal portion J1. That is, the rest 7 prevents the camshaft W from being bent during grinding.

  The grindstone bed 8 is supported behind the upper surface of the bed 1 (upward in FIG. 1) so as to be movable in the X-axis direction. The movement of the grindstone table 8 is performed by driving an X-axis motor 9 attached to the bed 1. A grindstone 10 is supported on the grindstone base 8 on the left side of FIG. 1 so as to be rotatable around the grindstone axis. Here, the grindstone axis is parallel to the main axis. The grindstone 10 has a disk shape. The grindstone 10 is rotated by driving a grindstone driving motor 11 via a belt.

  The touch sensor 12 is attached to the grindstone base 8 so that the probe 12a at the tip is positioned below in FIG. When the probe 12a of the touch sensor 12 comes into contact with the work, a contact signal is output. The touch sensor 12 is attached to the grindstone table 10 so as to be rotatable about an axis perpendicular to the paper surface of FIG. 1, and moves to a position indicated by a solid line in FIG. It moves to the position indicated by the broken line in FIG.

  Next, the control block configuration of the grinding machine will be described with reference to FIG. As shown in FIG. 1, the control block configuration of the grinding machine includes a reference distance storage unit 21, various data storage units 22, a control unit 23, a motor drive unit 24, a position detection unit 25, and a touch sensor drive unit. 26, a difference calculation unit 27, and a correction unit 28.

  The reference distance storage unit 21 measures and stores in advance a reference distance that is a distance from the central axis of the spindle to the reference surface of the reference member. Here, in the grinding method of the first embodiment described below, the reference member is the journal portion J1 that is closest to the cam portion C1 that is the grinding target portion. The reference surface is the outer peripheral surface of the journal portion J1. In the state where the camshaft W is attached to the main shaft 4a and the tailstock 6, the central axis of the journal portion J1 is coaxially positioned with respect to the main shaft central axis, so the reference distance is equal to the radius Rj of the journal portion J1. Become. Here, the radius Rj of the journal portion J1 is measured in advance. This measurement is performed every time the workpiece is changed. That is, the reference distance Rj is measured for each work.

  Usually, there are slight differences between workpieces due to the effect of machining accuracy. Therefore, in a strict sense, the reference distance Rj is different for each work. Therefore, by measuring the reference distance Rj for each workpiece and storing it in the reference distance storage unit 21, the accurate reference distance Rj can be used for each workpiece. As a result, since highly accurate correction described later can be performed, highly accurate grinding can be performed.

  The various data storage unit 22 inputs and stores various data such as the final radius Rc of the base circle B, the profile data of the protrusion T, the cutting depth, and the measurement program.

  The control unit 23 creates machining data based on the radius R1, the profile data, the cutting amount, and the like of the base circle B stored in the various data storage unit 22, and the motor drive unit 24 is controlled based on the machining data. Control. At this time, the drive unit 24 is controlled in consideration of the detection result by the position detection unit 25. Further, when the machining data is corrected by the correction unit 28 described later, the control unit 23 controls the motor driving unit 24 based on the corrected machining data. The control unit 23 controls the touch sensor driving unit 26 based on the measurement program stored in the various data storage unit 22.

  The motor driving unit 24 is controlled by the control unit 23 and drives the Z-axis motor 3, the main shaft motor 5, the X-axis motor 9, and the grindstone driving motor 10. That is, when machining data is being executed, the motor drive unit 24 controls the position of the table 2 in the X direction, the rotation angle of the main shaft 4a, the relative position between the main shaft 4a and the grindstone base 8, and the grindstone 10 Is rotated to grind the cam portion C1 of the camshaft W. When the measurement program is being executed, the motor driving unit 24 moves the spindle 4 a, the table 2, and the grindstone table 8 so as to come into contact with the measurement target by the touch sensor 12.

  The position detection unit 25 inputs the rotation angle of the Z-axis motor 3 to detect the Z-axis coordinate value of the table 2, and detects the X-axis coordinate value of the grindstone base 8 based on the rotation angle of the X-axis motor 9. Further, the position detector 25 detects the rotation angle of the main shaft 4 a based on the rotation angle of the main shaft motor 5. When the machining data is being executed, the detection result is fed back to the control unit 23. When the measurement program is being executed, the measurement program is output to a difference calculation unit 27 described later.

  The touch sensor driving unit 26 is controlled by the control unit 23 and drives the touch sensor 12. Specifically, when the measurement program is executed by the control unit 23 and a measurement start signal is output from the control unit 23, the touch sensor 12 is rotated clockwise in FIG. 1, and the probe 12a is moved downward in FIG. To be located. When the measurement program ends, the touch sensor 12 is rotated counterclockwise in FIG. 1, and the probe 12a is positioned on the right side in FIG.

  The difference calculation unit 27 inputs the X-axis coordinate value X1 of the grinding wheel base 8 when the probe 12a of the touch sensor 12 is brought into contact with the journal unit J1. Further, the difference calculation unit 27 is configured to make the X-axis coordinates of the grinding wheel base 8 when the probe 12a of the touch sensor 12 is brought into contact with the base circle B of the cam unit C1 (corresponding to the “predetermined measurement point” of the present invention). Enter the value X2. Hereinafter, the X-axis coordinate value X1 of the grinding wheel base 8 is referred to as “first relative position X1”, and the X-axis coordinate value X2 of the grinding wheel base 8 is referred to as “second relative position X2”. Then, the difference calculation unit 27 calculates a difference ΔX (hereinafter referred to as “measurement difference ΔX”) between the first relative position X1 and the second relative position X1.

  First, the correction unit 28 calculates the ideal radius R1 of the base circle B of the cam unit C1 based on the machining data created by the control unit 23. Then, the correction unit 28 calculates an ideal difference ΔXr between the ideal radius R1 and the reference distance Rj stored in the reference distance storage unit 21. Then, a deviation amount (ΔX−ΔXr) between the measurement difference ΔX calculated by the difference calculation unit 27 and the ideal difference ΔXr is calculated. Using this deviation amount (ΔX−ΔXr) as a correction amount, this correction amount is output to the control unit 23 to correct the machining data.

  Here, the relationship between the measurement difference ΔX, the ideal difference ΔXr, and the correction amount will be described with reference to FIG. As shown in FIG. 3A, the ideal radius of the base circle portion B of the cam portion C1 is R1. That is, the ideal radius R1 is a target value for the radius of the base circle B.

  In actual grinding, a processing error occurs due to various factors such as a change in the wheel diameter due to wear of the wheel and an increase in the X-direction separation distance between the spindle 4a and the wheel head 8 due to thermal displacement. Therefore, as shown in FIG. 3B, even if grinding is performed so that the ideal radius R1 is obtained, the actual radius R2 of the base circle B is shifted by (R2-R1) with respect to the ideal radius R1. That is, the actual radius R2 of the base circle B can coincide with the ideal radius R1 if the cut amount can be corrected by the amount of deviation (R2-R1) between the actual radius R2 and the ideal radius R1.

  Here, since the ideal radius R1 is a target value for the radius of the base circle B, it is a value obtained from the machining data. That is, the ideal radius R1 is a known value. On the other hand, since the actual radius R2 is an actual value, it is an unknown value. Therefore, in order to obtain this unknown actual radius R2, the measurement difference ΔX and the reference distance Rj are used.

  First, as shown in FIG. 3C, the first relative position X1 is calculated by bringing the probe 12a of the touch sensor 12 into contact with the outer peripheral surface (reference surface) of the journal portion J1. Subsequently, as shown in FIG. 3D, the probe 12a of the touch sensor 12 is brought into contact with the base circle B of the cam C1, and the second relative position X2 is calculated. Here, for convenience, the first relative position X1 and the second relative position X2 are the distances from the X-axis mechanical origin O3 to the grindstone axis O2 in each state.

  The measurement difference ΔX between the first relative position X1 and the second relative position X2 is equal to the value obtained by subtracting the reference distance Rj from the actual radius R2. That is, it has the relationship of Formula (1).

  Therefore, the unknown actual radius R2 can be calculated by converting the equation (1) into the equation (2).

  Here, if a thermal displacement occurs between the main spindle 4a and the grindstone table 8, each of the first relative position X1 and the second relative position X2 measured by the touch sensor 12 is affected by the thermal displacement. The value that received. However, since the measurement difference ΔX between the first relative position X1 and the second relative position X2 is a difference between those affected by the thermal displacement, the influence of the thermal displacement is almost eliminated. That is, the measurement difference ΔX has the same value regardless of whether a thermal displacement occurs between the main shaft 4a and the grindstone table 8 or no thermal displacement occurs.

  Further, the journal portion J1 that is a reference member is a journal portion that is closest to the cam portion C1 that is a grinding target portion. Accordingly, it is possible to shorten the movement time and the movement amount until the journal part J1 is brought into contact with the touch sensor 12 and then brought into contact with the base circle part B of the cam part C1. Therefore, when the touch sensor 12 moves between both contact positions, the occurrence of thermal displacement can be suppressed as much as possible, and both measurement results can be prevented from being affected by the thermal displacement.

  Further, since the journal portion J1 and the cam portion C1 are close to each other, both positions are affected to the same extent by the pushing margin by the rest 7. That is, the measurement difference ΔX is hardly affected by the push margin caused by the rest 7.

  Furthermore, the outer peripheral surface of the journal part J1 which is a reference member is located closer to the main shaft center axis than the outer peripheral surface of the cam part C1 which is a grinding target part. As described above, even when the influence of thermal displacement (thermal expansion) occurs on the workpiece W by using the outer peripheral surface of the journal portion J1 positioned nearer to the central axis of the spindle than the grinding part as a reference surface, the influence is exerted. Can be made as small as possible.

  Furthermore, the influence of the thermal expansion of the reference member itself is reduced by using a member that is arranged between the headstock 4 and the tailstock 6 as the workpiece W and is arranged across the spindle central axis. Can do. The reason will be described. When the journal portion J1 of the workpiece W is used as the reference member, the center line of the workpiece W including the reference member coincides with the central axis of the main shaft. Then, the reference member is provided on the touch sensor 12 side and the opposite side of the touch sensor 12 across the main axis. Therefore, when thermal displacement (thermal expansion) occurs in the reference member itself, the workpiece W constituting the reference member has a touch sensor 12 side portion and a portion on the opposite side of the touch sensor 12 from the spindle central axis. , Each will be evenly expanded. Accordingly, the distance from the central axis of the main shaft to the reference surface is half of the thermal expansion of the entire workpiece W. On the other hand, when the reference member is provided on the table 2, for example, if the reference member itself is thermally expanded, the reference member is directly affected by the thermal expansion. Thus, by using the workpiece as the reference member, when the reference member itself is thermally expanded, the influence can be reduced.

  As described above, the actual radius R2 of the base circle B obtained by the equation (2) is originally influenced by the measurement difference ΔX from which the influence of the thermal displacement and the pushing margin by the rest 7 are excluded, and the influence of the thermal displacement. By using no reference distance Rj, an accurate value that is not affected by thermal displacement is obtained.

  If the actual radius R2 can be obtained in this way, a deviation amount (R2-R1) between the obtained actual radius R2 and the known ideal radius R1 can be calculated, and this deviation amount (R2-R1). Can be used as the correction amount of the cutting amount.

  Next, the grinding method of 1st embodiment is demonstrated with reference to FIG. FIG. 4 is a flowchart showing the grinding method of the first embodiment. As shown in FIG. 4, first, the reference distance Rj is measured in advance, and is input and stored in the reference distance storage unit 21 (reference distance storage step) (step S1). Subsequently, various data such as the radius R1 of the base circle B, the profile data of the protruding portion T, the cutting depth, and the measurement program are input to the various data storage unit 22 and stored (step S2).

  Subsequently, the first grinding process is started (first grinding process) (step S3). In the first embodiment, the first grinding step is a grinding process from the material shape of the cam portion C1 until the cutting amount D reaches a predetermined interrupted cutting amount D1. In the first grinding step, the control unit 23 performs grinding by controlling the rotation angle of the main shaft 4a and the relative position between the main shaft 4a and the grindstone base 8 based on various data. Then, it is determined whether or not the cutting depth D has reached the interrupting cutting amount D1, and if it has not reached the interrupting cutting amount D1, the first grinding process is continued until the interrupting cutting amount D1 is reached (step) S4).

  When the cut amount D reaches the interrupted cut amount D1, the first grinding process is interrupted (step S5). Subsequently, the control unit 23 executes a measurement program. First, the control unit 23 calculates the angle of the spindle 4a (step S6).

  Here, the indexing angle will be described with reference to FIG. FIG. 5 is a view of the cam portion C1 viewed from the central axis direction of the main shaft 4a in a state where the angle of the main shaft 4a is determined. As shown in FIG. 5, the angle of the main shaft 4 a is determined so that the predetermined measurement point P of the base circle portion B of the cam portion C <b> 1 is in contact with the probe 12 a of the touch sensor 12. The predetermined measurement point P of the base circle B is ground by the grindstone 10 when positioned on a plane passing through the spindle central axis O1 and the grindstone axis O2 in the outer peripheral surface which is a grinding portion of the cam portion C1. Is a point. That is, the tangent at the predetermined measurement point P is orthogonal to the line segment connecting the main axis O1 and the predetermined measurement point P. Such a grinding part is a part where a grinding error and a measurement error are unlikely to occur. Therefore, highly accurate correction can be performed.

  Returning to FIG. After indexing the angle of the main shaft 4a, the probe 12a of the touch sensor 12 is brought into contact with the outer peripheral surface (reference surface) of the journal portion J1, and the X-axis coordinate value at that time, that is, the first relative position X1 is determined. Measure (Step S7). Subsequently, the probe 12a of the touch sensor 12 is brought into contact with the predetermined measurement point P of the base circle portion B of the cam portion C1, and the X-axis coordinate value at that time, that is, the second relative position X2 is measured (step S8). .

  Here, after first determining the angle of the main shaft 4a, the first relative position X1 and the second relative position X2 are measured. As described above, when determining the angle of the main shaft 4a, the predetermined measurement point P of the base circle portion B of the cam portion C1 is brought into contact with the probe 12a of the touch sensor 12. However, the journal part J1 is not considered at all. This is because the radial cross section of the outer peripheral surface of the journal portion J1 is circular, so that the point where the probe 12a of the touch sensor 12 abuts can be any position on the outer peripheral surface (reference surface) of the journal portion J1. is there. That is, the angle of the main shaft 4a is first calculated, and the angle of the main shaft 4a need not be calculated while the probe 12a of the touch sensor 12 is brought into contact with both contact positions. Therefore, in addition to the influence of the thermal displacement directly generated by rotating the main shaft 4a, both measurement results can be prevented from being affected by the thermal displacement caused by the extension of the time by rotating the main shaft 4a.

  Subsequently, the difference calculating unit 27 calculates a measurement difference ΔX between the first relative position X1 and the second relative position X2 (difference calculating step) (step S9). Then, the correction unit 28 calculates a deviation amount (R2−R1) based on the measurement difference ΔX, the reference distance Rj, and the ideal radius R1 of the base circle B obtained from the processing data, and corrects the processing data. (Correction process) (step S10).

  Subsequently, the second grinding process is started (second grinding process) (step S11). In the first embodiment, the second grinding step is a final cutting amount D2 in which the cutting amount D is determined in advance from the interrupted shape of the cam portion C1 in which the cutting amount D is in the interrupted cutting amount D1 state. Grinding until it reaches. In the second grinding step, the control unit 23 resumes the grinding process by controlling the rotation angle of the main spindle 4a and the relative position between the main spindle 4a and the grindstone base 8 based on various data. The machining data at this time is the machining data corrected by the correction unit 28. Then, it is determined whether or not the cutting depth D has reached the final cutting depth D1, and if the final cutting depth D2 is not reached, the second grinding process is continued until the final cutting depth D2 is reached (step) S12). Then, when the cutting depth D reaches the final cutting depth D2, the second grinding process is ended (step S13).

  As described above, according to the grinding method using the grinding machine of the first embodiment, the machining error can be calculated based on the measurement result excluding the influence of the thermal displacement. Therefore, by correcting the machining data according to the correction amount corresponding to the machining error, the final shape of the cam portion C1 can be matched with the target value.

<Other embodiments>
In the above embodiment, the reference distance Rj is measured for each workpiece and stored in the reference distance storage unit 21. In addition, the reference distance Rj stored in the reference distance storage unit 21 may be a tolerance median of design dimensions of the reference distance Rj. Thus, the reference distance can be determined without measuring the reference distance in advance for each workpiece. This is an effective means when the dimensional tolerance is sufficiently large. Further, instead of measuring the reference distance Rj for each workpiece, for example, the reference distance Rj may be measured at a rate of once per lot.

  In the above embodiment, the camshaft is described as an example of the workpiece. However, the present invention can be applied to, for example, a crankshaft, and can be applied to a non-circular or eccentric workpiece. .

  Further, although the journal portion J1 is applied as the reference member, a center provided on the headstock 4, a ram provided on the tailstock 6, or a reference block fixed to the table 2 may be applied. it can. However, it is preferable that the reference member is a workpiece.

It is a figure which shows the structure of the grinding machine of 1st embodiment. It is the figure of the state which looked at cam part C1-C4 and journal part J1, J2 from the axial direction (main-axis center axis | shaft O1 direction). It is a figure explaining the relationship between measurement difference (DELTA) X, ideal difference (DELTA) Xr, and a correction amount. It is a flowchart which shows the grinding method of 1st embodiment. It is the figure which looked at the cam part C1 in the state which calculated | required the angle of the main axis | shaft 4a from the main shaft central axis direction.

Explanation of symbols

1: bed, 2: table, 3: Z-axis motor, 4: spindle head, 4a: spindle
5: Spindle motor, 6: Tailstock, 7: Whetstone base, 8: Whetstone,
9: X-axis motor, 10: Wheel driving motor, 11: Wheel driving motor,
12: Touch sensor, 12a: Probe,
21: Reference distance storage unit, 22: Various data storage unit, 23: Control unit,
24: Motor drive unit, 25: Position detection unit, 26: Touch sensor drive unit,
27: difference calculation unit, 28: correction unit,
W: Camshaft (work)
C1-C4: Cam part, J1, J2: Journal part,
B: Base circle, T: Projection

Claims (9)

A spindle that supports a non-circular or eccentric workpiece so as to be rotatable about the spindle central axis;
A grindstone base that supports a grindstone rotatably around a grindstone axis parallel to the main spindle central axis, and is relatively movable in a direction orthogonal to the main spindle central axis with respect to the main spindle;
A touch sensor attached to the grinding wheel platform;
A reference member having a reference surface arranged at a position of a predetermined reference distance from the central axis of the main axis;
A reference distance storage unit for storing the reference distance in advance;
When the grinding process is interrupted in the middle of grinding one workpiece and the touch sensor is brought into contact with the reference surface, the first relative to the main axis of the main axis and the main axis of the grinding wheel base The difference between the position and the second relative position in the orthogonal direction of the spindle central axis between the spindle and the grinding wheel base when the touch sensor is brought into contact with a predetermined measurement point in the grinding part of the workpiece is calculated A difference calculating unit to
A correction unit that corrects the machining data of the workpiece based on the reference distance and the difference;
A control unit for controlling the rotation angle of the spindle and the relative position of the spindle and the grindstone base based on the machining data corrected by the correction unit, and restarting grinding of the one workpiece;
A grinding machine comprising:   The grinding machine according to claim 1, wherein the reference member is provided on the workpiece. The workpiece includes a grinding target portion having a non-circular shape or an eccentric shape, and a journal portion having a cylindrical shape or a columnar shape in which a central axis is positioned coaxially with the central axis of the main shaft,
The reference member is a journal part;
The grinding machine according to claim 2, wherein the reference surface is an outer peripheral surface of the journal portion. The work includes a plurality of the journal portions,
The grinding machine according to claim 3, wherein the reference member is the journal portion that is closest to the grinding target portion among the plurality of journal portions.   The grinding machine according to any one of claims 2 to 4, wherein the reference distance storage unit stores the reference distance measured in advance for each workpiece.   The grinding machine according to any one of claims 2 to 4, wherein the reference distance storage unit stores a median tolerance of design dimensions of the reference distance.   The said predetermined measurement point is a point ground by the said grindstone, when located on the plane which passes along the said spindle center axis | shaft and the said grindstone axis | shaft among the grinding parts of the said workpiece | work. The grinding machine according to one item. The workpiece has a shape having a base circle,
The grinding machine according to claim 7, wherein the predetermined measurement point is the base circle portion. A spindle that supports a non-circular or eccentric workpiece so as to be rotatable about the spindle central axis;
A grindstone base that supports a grindstone rotatably around a grindstone axis parallel to the main spindle central axis, and is relatively movable in a direction orthogonal to the main spindle central axis with respect to the main spindle;
A touch sensor attached to the grinding wheel platform;
A reference member having a reference surface arranged at a position of a predetermined reference distance from the central axis of the main axis;
With
A reference distance storing step for storing the reference distance in advance;
A first grinding step of controlling the rotation angle of the main shaft and the relative position between the main shaft and the grindstone table based on the processing data of the one workpiece, and grinding the one workpiece;
The first relative position in the orthogonal direction of the main axis of the main axis and the grinding wheel base when the touch sensor is brought into contact with the reference surface by interrupting the grinding process in the first grinding step, Difference calculation for calculating the difference between the main axis and the second relative position in the orthogonal direction of the main axis of the grinding wheel base when the touch sensor is brought into contact with a predetermined measurement point in the grinding portion of the workpiece. Process,
A correction step of correcting the machining data based on the reference distance and the difference;
A second grinding step of controlling the rotation angle of the spindle and the relative position between the spindle and the grindstone table based on the machining data corrected in the correction step and restarting the grinding of the one workpiece. When,
A method for grinding a non-circular or eccentric workpiece, comprising:

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