JP5287011B2 - Thread grinding machine and thread grinding method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a screw grinding machine and a screw grinding method allowing obtaining of high grinding accuracy without causing grinding burn in an effective screw part. <P>SOLUTION: The screw grinding machine includes a grinding resistance detecting part 61 for detecting grinding resistance when grinding a noneffective screw part 101b by a set grinding condition, a deciding part 62 for deciding whether or not the grinding resistance detected by the grinding resistance detecting part 61 is larger than a threshold Th1 set in advance, and a grinding condition determining part 64 for determining a fixed grinding condition for grinding the effective screw part 101 by changing the set grinding condition when it is decided that the grinding resistance is larger than the threshold Th1 by the deciding part 62. The effective screw part 101a is ground by the determined fixed grinding condition. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a thread grinding machine and a thread grinding method for grinding a thread groove on a long workpiece.

Conventionally, as a grinding machine, there is one described in JP-A-7-60640 (Patent Document 1). This grinding machine compares the detected value of the grinding resistance of the grindstone with a set value, and changes the relative lateral feed drive speed between the grindstone and the workpiece according to the comparison value. This set value is the grinding resistance value that does not cause grinding abnormalities such as grinding burn and chatter on the work piece, and the relative lateral distance between the grindstone and the work piece is set so that the comparison value between the set value and the grinding resistance is always zero. The feed speed (traverse speed) is controlled. As a result, the traverse speed decreases at the grinding position where the grinding resistance is high, and the traverse speed increases up to the set value at the grinding position where the grinding resistance is low. Therefore, extremely efficient grinding is performed without excessive grinding resistance.
Japanese Patent Laid-Open No. 7-60640

  However, in the grinding machine described in Patent Document 1, when the grinding resistance becomes larger than the set value, the relative lateral feed speed is changed so as to approach the set value, so that the grinding resistance can be instantaneously larger than the set value. There is sex. A particular problem with increased grinding resistance is that the product is subject to grinding burn. That is, according to the above grinding machine, no grinding burn is taken into consideration. Furthermore, the grinding conditions (relative lateral feed speed) are changed during grinding. Changing the grinding conditions may adversely affect the grinding accuracy.

  By the way, for example, in a product having a thread groove such as a ball screw, the thread groove is more accurate than an effective thread portion that requires a highly accurate thread groove shape as a product and both ends of the effective thread portion. There is an ineffective threaded portion that does not require. When the above grinding machine is applied to grinding of the thread groove, grinding burn may occur in the effective thread portion, and the grinding accuracy of the effective thread portion may be adversely affected.

  The present invention has been made in view of such circumstances, and it is an object of the present invention to provide a screw grinding machine and a screw grinding method capable of obtaining high grinding accuracy without causing grinding burn especially in an effective screw portion. And

  Hereinafter, each means suitable for solving the above-described problems will be described with additional effects and the like as necessary.

(Means 1) The thread grinder according to means 1 is:
For a long workpiece having a thread groove including an effective screw portion and a non-effective screw portion on both ends of the effective screw portion, by traversing a grindstone relatively in the axial direction of the long workpiece, A screw grinder that continuously grinds an ineffective thread portion and the effective thread portion,
A grinding resistance detection unit for detecting a grinding resistance when grinding the ineffective screw part according to set grinding conditions;
A determination unit that determines whether the grinding resistance detected by the grinding resistance detection unit is greater than a preset threshold;
When the determination unit determines that the grinding resistance is greater than the threshold, the set grinding condition is changed so that the grinding resistance is equal to or less than the threshold, and the effective thread portion is ground. A grinding condition determination unit for determining grinding conditions;
With
The effective threaded portion is ground under the determined constant grinding condition.

  According to the means 1, it is determined whether or not the grinding resistance is larger than the threshold value in the ineffective threaded portion, and the effective threaded portion is ground under the grinding condition determined according to the result. That is, in the effective thread portion, the grinding process is performed under the grinding conditions determined that the grinding resistance does not exceed the threshold value. Therefore, it is possible to prevent grinding burn from occurring in the effective screw portion. Furthermore, since the effective threaded portion is ground under stable grinding conditions, high-accuracy grinding is performed without causing adverse effects due to changes in grinding conditions as in the prior art. On the other hand, in the non-effective thread portion, grinding burn may occur due to the grinding resistance exceeding the threshold value, and grinding accuracy may be adversely affected by changing the grinding conditions. However, what is required of a product having a thread groove is not high grinding accuracy including an ineffective threaded portion but high grinding accuracy only in the effective threaded portion. Therefore, the grinding accuracy at the ineffective thread portion is not affected as a product.

  (Means 2) In the screw grinder of means 1, the threshold value is set to a different value according to the remaining cut amount when grinding is performed.

  The remaining cut amount means the remaining cut amount up to the final finished shape. That is, the remaining depth of cut is determined by the radial position of the outermost surface of the grinding wheel at the time of final grinding (final finishing) and the grinding wheel at the time of current grinding when the thread groove is ground by a grinding wheel. It means the difference from the radial position of the outermost surface. In other words, when it is assumed that the grinding wheel does not wear, the remaining cut amount corresponds to the difference between the rotation center of the grinding wheel at the time of the final grinding and the rotation center of the grinding wheel at the time of the current grinding. . According to the means 2, by setting the threshold value to be different according to the remaining cut amount, it is possible to prevent grinding burn in the state of grinding until the final finish. As a result, the grinding accuracy is improved.

(Means 3) In the screw grinder of means 2, the threshold value is set so as to become smaller as the remaining cut amount becomes smaller.
According to the means 3, by reducing the threshold value as the remaining cut amount approaches 0, it is possible to ensure that grinding burn does not occur in the ground state until the final finish. As a result, the grinding accuracy is reliably improved.

  (Means 4) In the thread grinder according to any one of the means 1 to 3, the grinding condition changed by the grinding condition determination unit is at least a relative traverse feed speed and a cutting amount of the long workpiece and the grindstone. On the other hand.

  According to the means 4, the grinding resistance can be changed reliably. However, changing the relative traverse feed speed between the long workpiece and the grindstone is better than changing the cutting depth. If the cutting amount is changed, the grinding allowance in the next step (the grinding process of the next remaining cutting amount) is different before and after the changed portion. On the other hand, when the traverse feed speed is changed, there is no influence on the next step. In addition, when changing traverse feed speed, it is natural that it is necessary to change also the rotation speed of the spindle which hold | maintains a workpiece | work synchronously.

(Means 5) In the thread grinder according to any one of means 1 to 4,
When the determination unit determines that the grinding resistance is greater than the threshold, the grinding condition determination unit grinds the ineffective screw portion while changing the set grinding condition, and the grinding resistance is Grinding conditions that are below the threshold are determined.

  According to the means 5, since the grinding condition determining unit determines the grinding condition in which the grinding resistance is equal to or less than the threshold value while actually grinding, it is possible to reliably prevent the grinding resistance in the effective screw portion from exceeding the threshold value. As a result, the grinding accuracy in the effective thread portion is improved.

(Means 6) In the thread grinder according to any one of means 1 to 4,
The thread grinder includes a changed grinding condition storage unit that stores a changed grinding condition according to a difference between the grinding resistance and the threshold value.
The grinding condition determination unit changes to the changed grinding condition stored in the changed grinding condition storage unit corresponding to the difference between the grinding resistance and the threshold value in the result determined by the determination unit. .

  According to the means 6, instead of determining a grinding condition in which the actual grinding resistance is less than or equal to the threshold value in the ineffective thread portion, a grinding condition that is less than or equal to the threshold value is determined based on a relation map stored in advance. In general, the ineffective threaded portion is not so long, and it is necessary to determine the grinding conditions at a short distance. Therefore, by storing in advance a relationship map between “difference between grinding resistance and threshold value” and “grinding condition after change”, “grinding condition after change” can be determined in a short time.

(Means 7) In any one of the thread grinders of means 1 to 6,
The set grinding conditions are set for each remaining cutting amount of the thread groove,
The screw grinder further includes the screw in the next step when the determination unit determines that the grinding resistance is greater than the threshold value during grinding in the remaining cut amount of the thread groove in the previous step. A next process grinding condition determination unit that determines the grinding condition after the change by changing the set grinding condition in the remaining cutting depth of the groove,
The grinding resistance detection unit detects a grinding resistance when the ineffective thread portion is ground according to the changed grinding condition in the next step.

  When it is determined that the grinding resistance is greater than the threshold in the grinding process with a certain remaining cut amount, it is highly likely that the grinding resistance is determined to be greater than the threshold even in the remaining cut amount in the next process. Therefore, according to the means 7, when it is determined that the grinding resistance is larger than the threshold value in a certain process, the grinding is performed with the changed grinding condition in the remaining cutting amount in the next process. Thereby, determination of suitable grinding conditions can be performed in a short time.

(Means 8) In the thread grinder according to any one of the means 1 to 7,
The grinding condition determination unit is configured to determine a relative traverse between the long workpiece and the grindstone among the grinding conditions for grinding the effective thread when the determination unit determines that the grinding resistance is smaller than the threshold value. Increase the feed rate.

  According to the means 8, when the grinding resistance has not reached the threshold value, the traverse feed speed is increased. Thereby, shortening of grinding time can be aimed at. In addition, the determination to increase the traverse feed speed is based on the result of grinding the ineffective threaded portion. Therefore, the traverse feed speed is not changed during the grinding of the effective thread portion. That is, according to this means, it is possible to shorten the grinding time while maintaining high grinding accuracy of the effective screw portion.

(Means 9) The thread grinding method according to means 9 is:
For a long workpiece having a thread groove including an effective screw portion and a non-effective screw portion on both ends of the effective screw portion, by traversing a grindstone relatively in the axial direction of the long workpiece, A thread grinding method for continuously grinding an ineffective thread portion and the effective thread portion,
Detecting the grinding resistance when grinding the ineffective screw part according to the set grinding conditions,
Determining whether the detected grinding resistance is greater than a preset threshold;
When it is determined that the grinding resistance is greater than the threshold, the set grinding condition is changed so that the grinding resistance is less than or equal to the threshold, and a fixed grinding condition for grinding the effective screw portion is determined. And
The effective threaded portion is ground under the determined constant grinding condition.

  According to the thread grinding method of means 9, the same effect as that of the thread grinder of means 1 can be obtained. Further, other characteristic portions as the screw grinding machine can be similarly applied to the screw grinding method. In these cases, the same effects as the corresponding effects are obtained.

  Hereinafter, an embodiment embodying a screw grinding machine of the present invention will be described with reference to the drawings.

<First embodiment>
(1) Description of Work 100 First, a long work 100 that is a grinding object by the screw grinder of the present invention will be described with reference to FIG. FIG. 1 is a side view of the workpiece 100. As shown in FIG. 1, the workpiece 100 is a ball screw in which a screw groove 101 in which a ball (not shown) can roll is formed in a spiral shape. That is, the workpiece 100 has a cylindrical shape or a columnar shape, and the thread groove 101 is formed on the outer peripheral surface thereof.

  The thread groove 101 is composed of the most effective screw portion 101a at the center and non-effective screw portions 101b and 101c located at both ends of the effective screw portion 101a. The effective screw portion 101a is a portion having an effective screw length defined by a ball screw or the like. The grinding accuracy of the effective screw portion 101a is required to be very high, but the non-effective screw portions 101b and 101c are not required to have a higher grinding accuracy than the effective screw portion 101a.

  The grinding of the thread groove 101 is performed as follows. First, the grinding wheel and the workpiece 100 are relatively traversed in the axial direction of the workpiece 100 in a state where the initial cutting amount is given. That is, at the initial depth of cut, grinding is started from the ineffective threaded portion 101b, the effective threaded portion 101a is continuously ground, and the ineffective threaded portion 101c is continuously ground. Subsequently, the grinding wheel and the workpiece 100 are relatively traversed in the axial direction of the workpiece 100 in a state where a further cutting amount is given. At this time, grinding is started from the ineffective threaded portion 101c, the effective threaded portion 101a is continuously ground, and the ineffective threaded portion 101b is continuously ground. This operation is repeated many times to bring the thread groove 101 into a final finished state.

  As will be described later, in grinding of the thread groove 101 at a certain remaining cut amount, the first grinding side of the ineffective screw portions 101b and 101c is a portion where the grinding resistance detection unit 61 detects the grinding resistance. is there. And the fixed grinding conditions of the effective thread part 101a are determined according to the grinding resistance at the time of grinding the said ineffective thread part 101b or the ineffective thread part 101c.

(2) Configuration of Screw Grinding Machine 1 Next, a mechanical configuration of the screw grinding machine 1 according to the present embodiment will be described with reference to FIG. FIG. 2 is a plan view of the screw grinding machine 1. As shown in FIG. 2, the grinding machine 1 includes a bed 10, a headstock 20, a tailstock 30, a grindstone support device 40, and a control device 60.

  The bed 10 has a substantially rectangular shape and is disposed on the floor. On the upper surface of the bed 10, the grindstone table guide rails 11 and 12 on which the grindstone table traverse base 41 constituting the grindstone support device 40 can slide extend in the left-right direction (Z-axis direction) in FIG. And they are formed parallel to each other. Further, on the lower surface of the bed 10 below the grinding wheel base guide rails 11 and 12, the first guide rails 13 and 14 on which the head stock 20 can slide are arranged in the left-right direction (Z (Axial direction) and are formed in parallel to each other. Further, on the right side of FIG. 2 from the first guide rails 13 and 14 on the upper surface of the bed 10, second guide rails 15 and 16 on which the tailstock 30 can slide are arranged in the left-right direction (Z-axis) in FIG. Direction) and parallel to each other.

  Further, the bed 10 is provided with a Z-axis ball screw (not shown) for the grindstone table for driving the grindstone traverse base 41 in the left-right direction of FIG. 2 between the guide rails 11 and 12 for the grindstone table. A grinding wheel base Z-axis motor 17 for rotating the grinding wheel base Z-axis ball screw is disposed. Further, a first Z-axis ball screw (not shown) for driving the headstock 20 in the left-right direction in FIG. 2 is disposed between the first guide rails 13 and 14 on the bed 10. A first Z-axis motor 18 that rotationally drives one Z-axis ball screw is disposed. The bed 10 is provided with a second Z-axis ball screw (not shown) between the second guide rails 15 and 16 for driving the tailstock 30 in the left-right direction in FIG. A second Z-axis motor 19 that rotates the Z-axis ball screw is disposed.

  The head stock 20 includes a head stock main body 21, a main shaft 22, and a main shaft center 23. The headstock body 21 is slidably disposed on the first guide rails 13 and 14 in the upper surface of the bed 10. The headstock body 21 is connected to the nut member of the first ball screw, and moves along the first guide rails 13 and 14 by driving the first Z-axis motor 18. Inside the headstock main body 21, a main shaft 22 is inserted and supported so as to be rotatable around the main shaft axis (around the Z axis in FIG. 2). A spindle center 23 that supports one end of the long workpiece 100 in the axial direction is attached to the right end of the spindle 22.

  The tailstock 30 includes a tailstock body 31 and a tailstock center 32. The tailstock body 31 is slidably disposed on the second guide rails 15 and 16 in the upper surface of the bed 10. The tailstock body 31 is connected to the nut member of the second ball screw, and moves along the second guide rails 15 and 16 by the drive of the second Z-axis motor 19. The tailstock main body 31 has a hole penetrating in the left-right direction in FIG. A tailstock center 32 is rotatably inserted and supported in the through hole of the tailstock main body 31. The rotating shaft of the tailstock center 32 is located coaxially with the main shaft of the main shaft 22. The tailstock center 32 supports the other axial end of the long workpiece 100. That is, the tailstock center 32 is disposed so as to face the spindle center 23. The spindle center 23 and the tailstock center 32 support both ends of the long workpiece 100. As described above, the long workpiece 100 is held by the spindle center 23 and the tailstock center 32 so as to be rotatable around the spindle axis (around the Z axis).

  The grinding wheel support device 40 includes a grinding wheel base traverse base 41, a grinding wheel base 42, a grinding wheel 43, and a grinding wheel rotation motor 44. The grinding wheel base traverse base 41 is formed in a rectangular flat plate shape, and is slidably disposed on the grinding wheel head guide rails 11 and 12 on the upper surface of the bed 10. The grinding wheel base traverse base 41 is connected to the nut member of the grinding wheel head ball screw, and moves along the grinding wheel head guide rails 11 and 12 by driving the grinding wheel head Z-axis motor 17. X-axis guide rails 41a and 41b on which the grinding wheel base 42 can slide are formed on the upper surface of the grinding wheel base traverse base 41 so as to extend in the vertical direction (X-axis direction) in FIG. 2 and to be parallel to each other. Has been. Furthermore, an X-axis ball screw (not shown) for driving the grinding wheel base 42 in the vertical direction of FIG. 2 is disposed between the X-axis guide rails 41a and 41b on the grinding wheel base traverse base 41. An X-axis motor 41c that rotates the X-axis ball screw is disposed.

  The grinding wheel base 42 is slidably disposed on the X-axis guide rails 41 a and 41 b in the upper surface of the grinding wheel base traverse base 41. And the grindstone base 42 is connected to the nut member of the X-axis ball screw, and moves along the X-axis guide rails 41a and 41b by the drive of the X-axis motor 41c. That is, the grindstone base 42 can move relative to the bed 10, the spindle stock 20, and the tailstock 30 in the X-axis direction and the Z-axis direction.

  A hole penetrating in the left-right direction in FIG. 2 is formed in the lower portion of FIG. A grinding wheel rotating shaft member is supported in the through hole of the grinding wheel base 42 so as to be rotatable around the central axis of the grinding wheel (around the Z axis). A grinding wheel 43 is coaxially attached to one end (left end in FIG. 2) of the grinding wheel rotating shaft member. A grinding wheel rotating motor 44 is fixed on the upper surface of the grinding wheel base 42. A pulley is suspended between the other end of the grinding wheel rotating shaft member (the right end in FIG. 2) and the rotating shaft of the grinding wheel rotating motor 44, so that the grinding wheel 43 is driven by the driving of the grinding wheel rotating motor 44. Rotate around.

  The control device 60 performs NC control of the rotation of the main shaft 22 and the X-axis position and the Z-axis position of the grindstone table 42. That is, by controlling the X-axis position and the Z-axis position of the grinding wheel 43 with respect to the long workpiece 100 while the grinding wheel 43 is rotated by the control device 60, the thread groove 101 is ground on the outer peripheral surface of the long workpiece 100. Process.

  That is, the Z-axis position of the grinding wheel 43 with respect to the long work 100 is moved (traverse feed) in a state where the X-axis position of the grinding wheel 43 with respect to the long work 100 is constant (a state in which the remaining cutting amount is an initial value). By doing so, the thread groove 101 is ground. Then, by repeating the operation of changing the remaining cut amount (X-axis position) and performing traverse feed again, the thread groove 101 is brought into the final finished state.

(3) Functional Block of Control Device 60 The functional block of the control device 60 will be described with reference to FIG. 3 and FIG. FIG. 3 is a block diagram of the control device 60. FIG. 4 is a diagram showing the relationship between the remaining cut amount of the thread groove 101 and the first threshold value Th1 of the grinding resistance.

  As shown in FIG. 3, the control device 60 includes a grinding resistance detection unit 61, a determination unit 62, a set grinding condition storage unit 63, a grinding condition determination unit 64, and a constant condition grinding unit 65. The grinding resistance detector 61 detects a grinding resistance generated when the thread groove 101 of the long workpiece 100 is ground by the grinding wheel 43. However, in the present embodiment, the grinding resistance detector 61 detects a grinding resistance when grinding the ineffective thread portion 101b or the ineffective thread portion 101c in the thread groove 101. Specifically, the grinding resistance detector 61 detects the grinding resistance of the non-effective threaded portions 101b and 101c on the side to be ground first in the grinding of the thread groove 101 at a certain remaining cut amount. This grinding resistance can be calculated by, for example, a grinding load received by the grinding wheel rotating motor 44.

  The determination unit 62 determines whether the grinding resistance detected by the grinding resistance detection unit 61 is greater than a preset first threshold Th1. Here, the first threshold value Th1 will be described with reference to FIG. As shown in FIG. 4, the first threshold value Th <b> 1 is set to a different value depending on the remaining cut amount when performing the grinding process. Specifically, the first threshold Th1 is set to have a relationship that decreases as the remaining cut amount decreases. That is, as the remaining cut amount approaches 0, the first threshold value Th1 of the grinding resistance decreases. For example, the first threshold Th1 has a linear relationship with the remaining cut amount. In this way, it can be set easily. Of course, the first threshold Th1 may be a polynomial relationship. By using a polynomial relationship, detailed determination is possible.

The reason for setting in this way is to satisfy that the grinding burn does not remain in the final finished state, because the grinding burn is less likely to occur as the grinding resistance is smaller. And this 1st threshold value Th1 of this grinding resistance is preset by experiment, the processing performance, analysis, etc.
The setting grinding condition storage unit 63 stores setting grinding conditions in advance. This set grinding condition is a grinding condition that enables efficient grinding so that the grinding resistance is equal to or less than the first threshold Th1 and in the vicinity of the first threshold Th1 according to the remaining cut amount. Is set. The grinding conditions here are a relative traverse feed speed and a cutting depth between the long workpiece 100 and the grinding wheel 43. Note that the rotational speed (rotational speed per unit time) of the main shaft 22 is uniquely determined when the traverse feed speed of the grinding wheel 43 is determined by the pitch of the thread groove 101.

  The grinding condition determination unit 64 grinds the grinding conditions for the effective screw portion 101a that is continuously ground to the non-effective screw portion 101b or the non-effective screw portion 101c when the non-effective screw portion 101b or the non-effective screw portion 101c is ground. To decide. Details will be described later. The constant condition grinding unit 65 controls each motor so as to grind the effective screw portion 101a according to the constant grinding condition determined by the grinding condition determination unit 64.

(4) Processing by Control Device 60 Next, a processing flowchart by the control device 60 configured as described above will be described with reference to FIGS. FIG. 5 is a flowchart showing the main processing of the grinding process. FIG. 6 is a flowchart showing a grinding condition determination grinding process.

  In the main processing of the grinding process, first, each motor is driven so that the grinding wheel 43 is positioned at the end portion of the non-effective screw portion 101b or the non-effective screw portion 101c of the long workpiece 100. Subsequently, the grinding wheel 43 is moved in the X-axis direction by the set cutting amount (step S1). Subsequently, grinding for determining grinding conditions is performed (step S2). This grinding condition determination grinding is a process of determining a traverse feed speed among appropriate grinding conditions while grinding the ineffective thread portion 101b or the ineffective thread portion 101c. This grinding condition determination grinding is shown in FIG.

  As shown in FIG. 6, first, the grinding process is started with the traverse feed speed V set to the set feed speed V0 stored in the set condition storage unit 63 (step S11). That is, first, grinding is performed at a preset feed speed V0. Subsequently, the grinding resistance in this grinding process is detected by the grinding resistance detector 61 (step S12). Subsequently, the determination unit 62 determines whether or not the grinding resistance detected by the grinding resistance detection unit 61 is greater than a first threshold Th1 stored in advance (step S13). If it is determined that the grinding resistance is greater than the first threshold Th1, the set feed speed V0 is delayed by a predetermined amount ΔV, the process returns to step S12 again, and the grinding resistance is detected (step S14). That is, when it is determined that the grinding resistance is greater than the first threshold Th1, the non-effective threaded portion 101b or the non-effective threaded portion 101c while changing the traverse feed speed V until the grinding resistance becomes equal to or less than the first threshold Th1. Continue to grind.

  When the determination unit 62 determines that the grinding resistance is equal to or less than the first threshold Th1, the current traverse feed speed V is stored as the determined feed speed Vd (step S15). That is, when the ineffective threaded portion 101b or the ineffective threaded portion 101c is ground at the set feed rate V0 and the grinding resistance is equal to or less than the first threshold Th1, the current traverse feed rate V is Set feed speed V0. On the other hand, when the ineffective threaded portion 101b or the ineffective threaded portion 101c is ground at the set feed speed V0, if the grinding resistance is greater than the first threshold Th1, the setting feed speed V0 is gradually changed to be slower. The changed traverse feed speed is the current traverse feed speed V. Thus, the determined feed speed Vd is a traverse feed speed at which the grinding resistance when grinding the ineffective thread portion 101b or the ineffective thread portion 101c is equal to or less than the first threshold Th1. In this way, the grinding condition determination grinding process is completed.

  Returning to FIG. After the grinding condition determination grinding, the grinding condition determination unit 64 determines whether or not the current grinding position has reached the effective screw portion 101a (step S3). If the current grinding position does not reach the effective thread portion 101a, the grinding condition determination grinding process is repeated. That is, the grinding condition determination grinding process is performed only while the ineffective threaded portion 101b or the ineffective threaded portion 101c is being ground.

  Subsequently, when the current grinding position reaches the ineffective screw portion 101b or the effective screw portion 101a continuous to the ineffective screw portion 101c, grinding is performed under a constant grinding condition (step S4). The grinding process under a constant grinding condition is to grind the effective screw portion 101a at the determined feed speed Vd (determined grinding condition) determined by the grinding condition determining unit 64. That is, if the grinding resistance when grinding the ineffective thread portion 101b or the ineffective thread portion 101c is equal to or less than the first threshold Th1, the effective thread portion 101a continuous to the ineffective thread portions 101b and 101c is ground. The determined feed speed Vd is the set feed speed V0 stored in the set condition storage unit 63. On the other hand, when the grinding resistance at the time of grinding the non-effective screw portion 101b or the non-effective screw portion 101c is larger than the first threshold Th1, the traverse feed speed slower than the set feed speed V0 stored in the setting condition storage unit 63. Changed to

  Then, until the threaded portion (including the effective threaded portion 101a and the ineffective threaded portions 101b and 101c) is finished (Step S5: No), the grinding process under the constant grinding condition is continued. That is, the traverse feed speed V is not changed until the next remaining cutting amount process is performed at least while the effective threaded portion 101a is ground in the same remaining cutting amount process.

  When the grinding of the screw portions 101a, 101b, and 101c in the process of the remaining cut amount is completed, it is determined whether or not the remaining cut amount is 0 (step S6). If the remaining cut amount is not 0, the process is repeated from step S1 until the remaining cut amount reaches 0, that is, until the final finished state is reached.

  That is, in the next remaining cutting amount step, the non-effective threaded portion 101b or the non-effective threaded portion 101c is ground at the traverse feed speed corresponding to the remaining cutting amount, and is detected at that time. The traverse feed speed for grinding the effective screw portion 101a is determined in accordance with the grinding resistance.

  From the above, in the non-effective screw portion 101b or the non-effective screw portion 101c, it is determined whether or not the grinding resistance is greater than the first threshold Th1, and the grinding condition determined according to the result (in the above, the traverse feed speed) The effective screw portion 101a is ground. That is, in the effective screw portion 101a, the grinding process is performed under the grinding conditions determined that the grinding resistance does not exceed the first threshold Th1. Therefore, it is possible to prevent grinding burn from occurring in the effective screw portion 101a. Furthermore, since the effective threaded portion 101a is ground under stable grinding conditions, high-accuracy grinding is performed without adverse effects caused by changes in the grinding conditions as in the prior art. On the other hand, in the non-effective threaded portion 101b or the non-effective threaded portion 101c, there is a possibility that grinding burn may occur when the grinding resistance exceeds the first threshold Th1, and the grinding accuracy is adversely affected by changing the grinding conditions. There is a risk of receiving. However, what is required of a product having the thread groove 101 is not a high grinding accuracy including the non-effective threaded portions 101b and 101c but a high grinding accuracy only in the effective threaded portion 101a. Therefore, the grinding accuracy in the ineffective thread portion 101b or the ineffective thread portion 101c is not affected as a product.

<Second embodiment>
The operation of the control device 160 of the thread grinding machine of the second embodiment will be described with reference to FIGS. FIG. 7 is a block diagram of the control device 160. FIG. 8 is a flowchart showing a grinding condition determination grinding process in the second embodiment. In addition, about the same structure as 1st embodiment, the same code | symbol is attached | subjected and description is abbreviate | omitted.

  As shown in FIG. 7, the control device 160 includes a grinding resistance detection unit 61, a determination unit 62, a set grinding condition storage unit 63, and a relationship map storage unit 161 (corresponding to the changed grinding condition storage unit of the present invention). And a grinding condition determination unit 164 and a constant condition grinding unit 65.

  The relation map storage unit 161 stores a relation map of the traverse feed speed V after the change to be changed from the set feed speed V0 according to the difference ΔR between the grinding resistance and the first threshold Th1 and the set feed speed V0. . That is, the relationship map is a map showing the relationship between the difference ΔR, the set feed speed V0, and the traverse feed speed V after the change. Specifically, the traverse feed speed V after the change is set to be smaller than the set feed speed V0. The changed traverse feed speed V is set to be smaller as the difference ΔR is larger, and the changed traverse feed speed V is set to be larger as the difference ΔR is smaller. The traverse feed speed V after the change is a traverse feed speed that can be ensured not to exceed the first threshold value Th1 when grinding is performed at the traverse feed speed V after the change by experiment or analysis in advance.

  The grinding condition determination unit 164 is based on the determination result of the determination unit 62 and information on the setting condition storage unit 63 and the relationship map storage unit 161 when grinding the ineffective thread portion 101b or the ineffective thread portion 101c. Then, the grinding condition of the effective screw portion 101a is determined. Details will be described later.

  As shown in FIG. 8, in the grinding condition determination grinding process in the second embodiment, first, the grinding process is started with the traverse feed speed V set to the set feed speed V0 stored in the set condition storage unit 63 ( Step S21). That is, first, grinding is performed at a preset feed speed V0. Subsequently, the grinding resistance in this grinding process is detected by the grinding resistance detector 61 (step S22). Subsequently, the determination unit 62 determines whether or not the grinding resistance detected by the grinding resistance detection unit 61 is greater than a first threshold Th1 stored in advance (step S23). When it is determined that the grinding resistance is equal to or less than the first threshold Th1, the current traverse feed speed V is stored as the determined feed speed Vd (step S24). Then, the grinding condition determination grinding process is terminated.

  On the other hand, if it is determined that the grinding resistance is greater than the first threshold Th1, a difference ΔR between the detected grinding resistance and the first threshold Th1 in the process of the remaining cut amount is calculated (step S25). Subsequently, based on the relation map stored in the relation map storage unit 161, a traverse feed speed V after change according to the calculated difference ΔR and the set feed speed V0 in the current remaining cutting amount process is obtained. Then, the traverse feed speed V after the change is stored as “determined feed speed Vd” (step S26). Then, the grinding condition determination grinding process is terminated.

  That is, when the ineffective threaded portion 101b or the ineffective threaded portion 101c is ground at the set feed speed V0, if the grinding resistance is equal to or less than the first threshold Th1, the set feed speed V0 is determined feed. The speed becomes Vd. On the other hand, when the ineffective threaded portion 101b or the ineffective threaded portion 101c is ground at the set feed speed V0, if the grinding resistance is greater than the first threshold Th1, the calculated difference ΔR, the current remaining cut In accordance with the set feed speed V0 in the quantity process, the changed traverse feed speed V made slower than the set feed speed V0 becomes the determined feed speed Vd. Then, the greater the calculated difference ΔR, the smaller the determined feed speed Vd. That is, the determined feed speed Vd can be determined in a short time, and is a traverse feed speed at which the grinding resistance when grinding the ineffective thread portion 101b or the ineffective thread portion 101c is equal to or less than the first threshold Th1.

  As described above, the determined feed speed Vd can be determined in a shorter time than in the case of the first embodiment. In general, the ineffective screw portions 101b and 101c are not so long. Therefore, when adopting the second embodiment, it is possible to reliably determine the determined feed speed Vd during grinding of the ineffective screw portion 101b or the ineffective screw portion 101c.

<Third embodiment>
Operation | movement of the control apparatus 60 of the thread grinding machine of 3rd embodiment is demonstrated with reference to FIG. 9 and FIG. FIG. 9 is a flowchart showing a grinding condition determination grinding process in the third embodiment. FIG. 10 is a diagram showing the relationship between the remaining cut amount of the thread groove 101 and the first threshold value Th1 and the second threshold value Th2 of the grinding resistance.

  First, the second threshold Th2 will be described with reference to FIG. The second threshold Th2 is a threshold at which the grinding resistance is set slightly smaller than the first threshold Th1. As described above, the first threshold value Th1 has a meaning as an upper limit value of the grinding resistance in which grinding burn or the like may remain. On the other hand, the second threshold value Th2 has a meaning as a lower limit value that can increase the grinding efficiency by setting the grinding resistance to be equal to or higher than the threshold value. That is, when the grinding resistance is less than or equal to the second threshold Th2, it is possible to increase the grinding efficiency by taking measures such as increasing the traverse feed speed V.

  Next, the grinding condition determination grinding process in the third embodiment will be described with reference to FIG. First, grinding is started with the traverse feed speed V set to the set feed speed V0 stored in the set condition storage unit 63 (step S31). That is, first, grinding is performed at a preset feed speed V0. Subsequently, the grinding resistance in the grinding process is detected by the grinding resistance detector 61 (step S32). Subsequently, the determination unit 62 determines whether or not the grinding resistance detected by the grinding resistance detection unit 61 is greater than a first threshold Th1 stored in advance (step S33). When it is determined that the grinding resistance is greater than the first threshold Th1, the set feed speed V0 is delayed by a predetermined amount ΔV1, and the process returns to step S32 again to detect the grinding resistance (step S34). That is, when it is determined that the grinding resistance is greater than the first threshold Th1, the non-effective threaded portion 101b or the non-effective threaded portion 101c while changing the traverse feed speed V until the grinding resistance becomes equal to or less than the first threshold Th1. Continue to grind.

  On the other hand, when the determination unit 62 determines that the grinding resistance is equal to or less than the first threshold Th1, the grinding resistance detected by the grinding resistance detection unit 61 at the determination unit 62 is the second threshold Th2 stored in advance. It is determined whether it is larger (step S35). If it is determined that the grinding resistance is equal to or less than the second threshold Th2, the set feed speed V0 is increased by a predetermined amount ΔV2, and the process returns to step S32 again to detect the grinding resistance (step S36). That is, when it is determined that the grinding resistance is equal to or less than the second threshold Th2, the traverse feed speed V is changed until the grinding resistance is equal to or less than the first threshold Th1 and is greater than the second threshold Th2. The ineffective threaded portion 101b or the ineffective threaded portion 101c is continuously ground.

  If the determination unit 62 determines that the grinding resistance is equal to or less than the first threshold Th1 and greater than the second threshold Th2, the current traverse feed speed V is stored as the determined feed speed Vd (step S37). ). That is, when the ineffective threaded portion 101b or the ineffective threaded portion 101c is ground at the set feed speed V0, if the grinding resistance is less than the first threshold Th1 and greater than the second threshold Th2, the current traverse The feed speed V becomes the set feed speed V0. On the other hand, when the ineffective threaded portion 101b or the ineffective threaded portion 101c is ground at the set feed speed V0, if the grinding resistance is greater than the first threshold Th1, the setting feed speed V0 is gradually changed to be slower. The changed traverse feed speed is the current traverse feed speed V. Further, when the ineffective threaded portion 101b or the ineffective threaded portion 101c is ground at the set feed speed V0, if the grinding resistance is equal to or less than the second threshold Th2, the set feed speed V0 is gradually increased. The traverse feed speed after the change that has been changed earlier becomes the current traverse feed speed V.

  Thus, the determined feed speed Vd is a traverse feed speed at which the grinding resistance when grinding the ineffective thread portion 101b or the ineffective thread portion 101c is equal to or less than the first threshold Th1 and greater than the second threshold Th2. In this way, the grinding condition determination grinding process is completed.

  From the above, when the grinding resistance has not reached the second threshold Th2, the traverse feed speed V is increased. Thereby, shortening of grinding time can be aimed at. The determination to increase the traverse feed speed V is based on the result of grinding the non-effective screw portion 101b or the non-effective screw portion 101c. Therefore, the traverse feed speed V is not changed during the grinding of the effective screw portion 101a. That is, it is possible to shorten the grinding time while maintaining high grinding accuracy of the effective screw portion 101a.

<Fourth embodiment>
Operation | movement of the control apparatus 260 of the thread grinding machine of 4th embodiment is demonstrated with reference to FIG. 11 and FIG. FIG. 11 is a block diagram of the control device 260. FIG. 12 is a flowchart showing a main process of grinding in the fourth embodiment.

  As shown in FIG. 11, the control device 260 includes a grinding resistance detection unit 61, a determination unit 62, a set grinding condition storage unit 63, a next process grinding condition determination unit 261, a grinding condition determination unit 64, and a constant condition. And a grinding part 65.

  The next process grinding condition determining unit 261 determines that the next process grinding condition is determined when the determination unit 62 determines that the grinding resistance is greater than the first threshold Th1 during the grinding process with the remaining depth of the thread groove 101 in the previous process. The set feed speed V0 in the remaining cut amount of the thread groove 101 is changed to determine the traverse feed speed V after the change. That is, when it is determined in the previous step that the grinding resistance in the ineffective thread portion 101b or the ineffective thread portion 101c is greater than the first threshold Th1, the ineffective thread portion 101b or the ineffective thread portion 101c in the next step is determined. The traverse feed speed for starting grinding is changed in advance.

  Details will be described with reference to FIG. In the main processing of grinding, first, the next process grinding condition determination unit 261 determines whether or not the grinding resistance at the set feed speed V0 of the previous process is larger than the first threshold Th1 (step S41). Here, each process means a process for each remaining cut amount. That is, the previous process is a process at the last remaining cutting amount than the current process.

  When the grinding resistance in the previous process is larger than the first threshold Th1, the setting feed speed V0 in the remaining cutting amount in the current process is changed to be slow (step S42). On the other hand, when the grinding resistance in the previous process is equal to or less than the first threshold Th1, the process proceeds to the next step without changing the set feed speed V0.

  Subsequently, each motor is driven so that the grinding wheel 43 is positioned at the end of the non-effective screw portion 101b or the non-effective screw portion 101c of the long workpiece 100. Subsequently, the grinding wheel 43 is moved in the X-axis direction by the set cutting amount (step S43). Subsequently, grinding for determining grinding conditions is performed (step S44). This grinding condition determination grinding is a process of determining a traverse feed speed among appropriate grinding conditions while grinding the ineffective thread portion 101b or the ineffective thread portion 101c. That is, in this grinding condition determination grinding, if it is determined in step S41 that the grinding resistance in the previous process is greater than the first threshold value Th1, the grinding process is started at the changed set feed speed V. On the other hand, in the grinding condition determination grinding, when it is determined in step S41 that the grinding resistance in the previous process is equal to or less than the first threshold Th1, the grinding process is started at a preset set feed speed V0.

  Subsequently, after the grinding condition determination grinding, the grinding condition determination unit 64 determines whether or not the current grinding position has reached the effective thread portion 101a (step S45). If the current grinding position does not reach the effective thread portion 101a, the grinding condition determination grinding process is repeated. That is, the grinding condition determination grinding process is performed only while the ineffective threaded portion 101b or the ineffective threaded portion 101c is being ground.

  Subsequently, when the current grinding position reaches the effective screw portion 101a, grinding is performed under a certain grinding condition (step S46). The constant condition grinding means that the effective screw portion 101a is ground at the determined feed speed Vd (determined grinding condition) determined by the grinding condition determining unit 64. That is, when the grinding resistance when grinding the non-effective screw portion 101b or the non-effective screw portion 101c is equal to or less than the first threshold Th1, the determined feed speed Vd for grinding the effective screw portion 101a is the set condition storage unit 63. Or the traverse feed speed V changed by the next-step grinding condition determination unit 261. On the other hand, when the grinding resistance at the time of grinding the ineffective thread portion 101b or the ineffective thread portion 101c is larger than the first threshold Th1, the feed speed is slower than the set feed speed V0 stored in the set condition storage section 63. Be changed.

  Then, until the threaded portion (including the effective threaded portion 101a and the ineffective threaded portions 101b and 101c) is finished (step S47: No), the grinding process under the constant grinding condition is continued. That is, the traverse feed speed V is not changed until the next remaining cutting amount process is performed at least while the effective threaded portion 101a is ground in the same remaining cutting amount process.

  When the grinding of the screw portions 101a, 101b, and 101c in the remaining cut amount process is completed, it is determined whether or not the remaining cut amount is 0 (step S48). If the remaining cut amount is not 0, the process is repeated from step S41 until the remaining cut amount reaches 0, that is, the final finished state is reached.

  That is, in the next remaining cutting amount step, the non-effective threaded portion 101b or the non-effective threaded portion 101c is ground at the traverse feed speed corresponding to the remaining cutting amount, and is detected at that time. The traverse feed speed for grinding the effective screw portion 101a is determined in accordance with the grinding resistance.

  Here, when it is determined that the grinding resistance is greater than the first threshold Th1 in the grinding process of a certain remaining cut amount, the grinding resistance is also greater than the first threshold Th1 in the process of the remaining cut amount of the next process. There is a high possibility of being determined to be large. Therefore, by determining as described above, if it is determined that the grinding resistance is greater than the first threshold Th1 in a certain process, in the process of the remaining cutting amount in the next process, non- Grinding of the effective screw portion 101b or the non-effective screw portion 101c is started. Thereby, determination of suitable grinding conditions can be performed in a short time.

  In each of the above embodiments, the grinding condition to be changed is the relative traverse feed speed of the grinding wheel 43 with respect to the long workpiece 100. In addition to this, as the grinding condition to be changed, the cutting amount can be set, or both the traverse feed speed and the cutting amount can be set. However, the traverse feed speed is optimal.

1 is a side view of a workpiece 100. FIG. 1 is a plan view of a screw grinder 1. FIG. 3 is a block diagram of a control device 60. FIG. It is a figure which shows the relationship between the remaining cut amount of the thread groove, and the 1st threshold value Th1 of grinding resistance. It is a flowchart which shows the main process of a grinding process. It is a flowchart which shows the process of grinding condition determination grinding. 3 is a block diagram of a control device 160. FIG. It is a flowchart which shows the process of the grinding condition determination grinding in 2nd embodiment. It is a flowchart which shows the process of the grinding condition determination grinding in 3rd embodiment. It is a figure which shows the relationship between the residual cutting amount of the thread groove 101, 1st threshold value Th1 of grinding resistance, and 2nd threshold value Th2. 3 is a block diagram of a control device 260. FIG. It is a flowchart which shows the main process of the grinding process in 4th embodiment.

Explanation of symbols

1: grinding machine, 10: bed, 20: spindle stock, 30: tailstock, 40: grinding wheel support device 60, 160, 260: control device 100: long work (ball screw), 101: screw groove 101a: effective Screw part, 101b, 101c: Ineffective screw part

Claims (9)

For a long workpiece having a thread groove including an effective screw portion and a non-effective screw portion on both ends of the effective screw portion, by traversing a grindstone relatively in the axial direction of the long workpiece, A screw grinder that continuously grinds an ineffective thread portion and the effective thread portion,
A grinding resistance detection unit for detecting a grinding resistance when grinding the ineffective screw part according to set grinding conditions;
A determination unit that determines whether the grinding resistance detected by the grinding resistance detection unit is greater than a preset threshold;
When the determination unit determines that the grinding resistance is greater than the threshold, the set grinding condition is changed so that the grinding resistance is equal to or less than the threshold, and the effective thread portion is ground. A grinding condition determination unit for determining grinding conditions;
With
A thread grinding machine characterized in that the effective thread portion is ground under the determined constant grinding condition.   The thread grinder according to claim 1, wherein the threshold value is set to a different value in accordance with a remaining cut amount when grinding is performed.   The thread grinder according to claim 2, wherein the threshold value is set so as to decrease as the remaining cut amount decreases.   The screw according to any one of claims 1 to 3, wherein the grinding condition changed by the grinding condition determining unit is at least one of a relative traverse feed speed and a cutting amount between the long workpiece and the grindstone. Grinder.   When the determination unit determines that the grinding resistance is greater than the threshold, the grinding condition determination unit grinds the ineffective screw portion while changing the set grinding condition, and the grinding resistance is The thread grinder as described in any one of Claims 1-4 which determines the grinding conditions used as the said threshold value or less. The thread grinder includes a changed grinding condition storage unit that stores a changed grinding condition according to a difference between the grinding resistance and the threshold value.
The grinding condition determination unit changes to the changed grinding condition stored in the changed grinding condition storage unit corresponding to the difference between the grinding resistance and the threshold value in the result determined by the determination unit. The thread grinder as described in any one of Claims 1-4. The set grinding conditions are set for each remaining cutting amount of the thread groove,
The screw grinder further includes the screw in the next step when the determination unit determines that the grinding resistance is greater than the threshold value during grinding in the remaining cut amount of the thread groove in the previous step. A next process grinding condition determination unit that determines the grinding condition after the change by changing the set grinding condition in the remaining cutting depth of the groove,
The screw grinding machine according to any one of claims 1 to 6, wherein the grinding resistance detection unit detects a grinding resistance when the non-effective thread part is ground according to the changed grinding condition in the next step. .   The grinding condition determination unit is configured to determine a relative traverse between the long workpiece and the grindstone among the grinding conditions for grinding the effective thread when the determination unit determines that the grinding resistance is smaller than the threshold value. The screw grinding machine according to any one of claims 1 to 7, wherein the feed rate is increased. For a long workpiece having a thread groove including an effective screw portion and a non-effective screw portion on both ends of the effective screw portion, by traversing a grindstone relatively in the axial direction of the long workpiece, A thread grinding method for continuously grinding an ineffective thread portion and the effective thread portion,
Detecting the grinding resistance when grinding the ineffective screw part according to the set grinding conditions,
Determining whether the detected grinding resistance is greater than a preset threshold;
When it is determined that the grinding resistance is greater than the threshold, the set grinding condition is changed so that the grinding resistance is less than or equal to the threshold, and a fixed grinding condition for grinding the effective screw portion is determined. And
A thread grinding method, wherein the effective thread portion is ground under the determined constant grinding condition.

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