Control method for abrasive tool holder, abrasive tool holder, and abrasive tool

Abstract

The grinding tool holder (4) of the grinding tool (1) includes: a handle portion (6), a mounting portion (21) for mounting the grinding tool (3), and an electric motor (35), and further includes: a moving mechanism (22) for moving the mounting portion (21) in the axial direction (X) of the handle portion (6), a load detector (23) for detecting the load applied to the grinding tool (3) mounted on the mounting portion (21), and a control unit (52) for driving and controlling the electric motor (35). The control unit (52) monitors the output from the load detector (23), sequentially calculates the change amount of the load, drives the electric motor (35) based on the load and the change amount, and performs a protrusion control operation for advancing and retracting the grinding tool (3) mounted on the mounting portion (21).

Description

Technical Field

[0001] The present invention relates to an abrasive holder for adjusting the cutting amount of an abrasive by advancing and retracting an abrasive tool having an abrasive along the axial direction of a mechanical mounting portion, and a control method for the abrasive holder. Further, it relates to an abrasive tool composed of the above abrasive holder and the abrasive tool. Background Art

[0002] Patent Document 1 describes an abrasive holder for detachably mounting an abrasive tool having an abrasive. The abrasive holder of this document includes: a shank portion as a mechanical mounting portion, a mounting portion, and a support mechanism capable of supporting the mounting portion so as to be movable along the axial direction of the shank portion. Further, the abrasive holder includes: a moving mechanism having a drive source for moving the mounting portion in the axial direction, a load detector for detecting the load applied to the abrasive tool mounted on the mounting portion, and a control portion for driving the drive source based on the output from the load detector to move the mounting portion in the axial direction.

[0003] When machining a workpiece using the abrasive holder, the abrasive tool is mounted on the mounting portion to form an abrasive tool composed of the abrasive tool and the abrasive holder. Next, the shank portion of the abrasive tool is connected to the spindle of a machine tool, and the machine tool is operated. Then, while the abrasive tool is moved along a predetermined machining path by the machine tool, the abrasive is brought into contact with the surface of the workpiece. The machining path is defined such that the distance between the spindle of the machine tool and the machining target surface is maintained constant when the abrasive tool and the machining target surface of the workpiece face each other.

[0004] If the abrasive wears during the machining operation, the tip of the abrasive retreats in a direction away from the surface of the workpiece. As a result, since the load applied to the abrasive tool from the workpiece side decreases, the output (load) from the load detector becomes smaller. Here, if the output from the load detector becomes smaller than a predetermined load threshold (limit value) range, the control portion drives the drive source to perform a protrusion control operation for advancing the mounting portion toward the workpiece side. As a result, since the abrasive tool advances, the abrasive protrudes toward the workpiece. Thus, even when the abrasive wears during the machining operation, the cutting amount of the abrasive with respect to the workpiece can be ensured.

[0005] In addition, when the grinding tool approaches the machining object surface of the workpiece too closely during the machining operation due to reasons such as dimensional errors of the workpiece, the load applied to the grinding tool from the workpiece side increases, so the output (load) from the load detector becomes larger. Here, if the output from the load detector becomes larger than the specified load threshold range, the control unit drives the drive source to perform a protruding control action that causes the mounting portion to retreat toward the side away from the workpiece. As a result, since the grinding tool retreats, the abrasive retreats in the direction away from the workpiece. Thereby, even when the grinding tool approaches the workpiece too closely during the machining operation, the cutting amount of the abrasive against the workpiece can be maintained constant.

[0006] Prior Art Documents

[0007] Patent Documents

[0008] Patent Document 1: International Publication WO2019 / 138595 Summary of the Invention

[0009] Technical Problem to be Solved by the Invention

[0010] The machining path for the machine tool to move the grinding tool is sometimes set to pass through the workpiece from the front of the workpiece and reach the rear of the workpiece. In this case, during the period when the grinding tool passes through the workpiece, since the abrasive grinds the machining object surface of the workpiece, wear will occur on the abrasive. Therefore, when the output (load) from the load detector decreases, it is necessary to perform a protruding control action to ensure the cutting amount of the abrasive against the workpiece. However, during the period when the grinding tool is in front of the workpiece and after the grinding tool reaches the rear of the workpiece, the abrasive does not contact the machining object surface of the workpiece. Therefore, even when the output from the load detector decreases, it is not necessary to perform a protruding control action.

[0011] Here, the machine tool that moves the grinding tool along the machining path can grasp the position of the grinding tool relative to the workpiece. However, the grinding tool holder connected to the machine tool cannot grasp the position of the grinding tool relative to the workpiece. Therefore, when the grinding tool is in front of the workpiece or behind the workpiece, there is a problem that when the load output from the load detector decreases, the drive source is driven to move the grinding tool holder in the axial direction.

[0012] In view of the above problems, the subject of the present invention is to provide a grinding tool holder and a grinding tool that perform a protruding control action to move the grinding tool only when the grinding tool is in contact with the machining object surface of the workpiece. In addition, a control method for the above grinding tool holder is proposed.

[0013] Technical Solution for Solving the Technical Problem

[0014] In order to solve the above problems, in the control method of the grinding tool holder of the present invention, the grinding tool holder includes a mechanical mounting portion; a mounting portion on which a grinding tool is mounted; a moving mechanism having a drive source and moving the mounting portion in the axial direction of the mechanical mounting portion; and a load detector for detecting the load applied to the grinding tool mounted on the mounting portion. The control method of the grinding tool holder is characterized in that a grinding tool having an abrasive is mounted on the mounting portion, and the mechanical mounting portion is connected to the spindle of a machine tool and the machine tool is operated. During the movement of the grinding tool holder along a pre-specified machining path by the machine tool, the output from the load detector is monitored, and the change amount of the load per unit time is calculated. Based on the load and the change amount, the drive source is driven to move the mounting portion, thereby performing a protrusion control action for advancing and retracting the grinding tool.

[0015] The grinding tool holder of the present invention is used in a state where a grinding tool having an abrasive is mounted on the mounting portion and a grinding tool is constituted by the grinding tool and the grinding tool holder. In addition, the mechanical mounting portion of the grinding tool is connected to the spindle of a machine tool for use. According to the present invention, during the movement of the grinding tool along a pre-specified machining path of the machine tool, the output from the load detector is monitored, and the change amount of the load per unit time is sequentially calculated. Based on the load and the change amount, the drive source is driven to perform a protrusion control action for advancing and retracting the grinding tool. Here, the change amount of the load that changes during the period when the grinding tool grinds the machining object surface of the workpiece in the grinding operation of the workpiece can be grasped in advance through experiments or the like. Therefore, the grinding tool holder can judge whether it is in a state where the grinding tool contacts the machining object surface of the workpiece based on the change amount of the load. Thus, if the protrusion control action is performed based on the load and the change amount of the load, the grinding tool holder can perform the protrusion control action of protruding the grinding tool toward the workpiece side only when the grinding tool contacts the machining object surface of the workpiece.

[0016] In the present invention, preferably, when the load is outside a preset load threshold range and the change amount is smaller than a preset change amount threshold, the protruding control operation is performed. That is, the change amount of the load that changes during the period when the grinding tool grinds the machining object surface of the workpiece in the grinding operation of the workpiece can be grasped in advance through experiments or the like. Therefore, if the change amount threshold is preset based on the change amount obtained through experiments or the like, when the change amount becomes equal to or greater than the change amount threshold, the grinding tool holder determines that the change in the load is not caused by the wear of the abrasive. In other words, when the change amount is smaller than the change amount threshold, the grinding tool holder can determine that it is in a state where the grinding tool is grinding the machining object surface of the workpiece and that the load change is caused by the wear of the abrasive due to grinding. Therefore, if the protruding control operation is performed when the change amount is smaller than the preset change amount threshold and the load is outside the preset load threshold range, the protruding control operation can be performed when the grinding tool contacts the machining object surface of the workpiece and the load changes due to the wear of the abrasive.

[0017] In the present invention, it can be set that when the load is zero, the protruding control operation is stopped, and the state of not performing the protruding control operation is maintained until the change amount is lower than a preset set change amount. The state where the load is zero is a state where the load detector does not detect the load applied to the grinding tool. Therefore, the state where the load is zero is a state where the grinding tool does not contact the workpiece. Thus, if the load is zero, the grinding tool holder can determine that the grinding tool is located outside the machining object surface of the workpiece. Here, when the grinding tool is located outside the machining object surface of the workpiece, no wear occurs on the abrasive. Therefore, the grinding tool holder is set to a state where the protruding control operation is not performed. Thus, unnecessary protruding control operations can be stopped. Here, when the grinding tool feeds from outside the workpiece to the machining object surface of the workpiece, when the grinding tool contacts the workpiece, the change amount of the load increases sharply. Moreover, at the moment when the feed toward the workpiece ends, the change amount of the load exceeds the peak value and then decreases. Therefore, at the moment when the feed toward the workpiece ends, the change amount becomes a value close to zero. Thus, if the set change amount is preset to a value close to zero or the like, when the protruding control operation is stopped when the load is zero and the state of not performing the protruding control operation is maintained until the change amount is lower than the preset set change amount, and then the protruding control operation is started, the protruding control operation can be not performed until the grinding tool feeds onto the workpiece, and the protruding control operation can be performed after the grinding tool feeds onto the workpiece.

[0018] In the present invention, it can be set that when the load is outside the load threshold range and the change amount is within the specified change amount threshold range, the state is set such that the protruding control action is not performed. When the load is outside the load threshold range and the change amount is outside the change amount threshold range, the protruding control action can be performed. When the grinding tool retracts from the machining target surface of the workpiece, during the period when the grinding tool moves away from the workpiece, the load applied to the grinding tool from the workpiece side decreases sharply. Therefore, the change amount of the load will increase sharply. Here, the change amount of the load that decreases sharply when the grinding tool retracts from the workpiece can be grasped in advance through experiments or the like. Therefore, if a specified range including the change amount of the load grasped through tests or the like is set in advance as the change amount threshold range, when the change amount of the load is within the change amount threshold range, the grinding tool holder can determine that the grinding tool is in the middle of retracting from the machining target surface of the workpiece. Therefore, even when the load is outside the load threshold range, if the protruding control action is not performed when the change amount is within the change amount threshold range, unnecessary protruding control actions can be stopped in the middle of the grinding tool retracting from the machining target surface of the workpiece. On the other hand, when the load is outside the load threshold range and the change amount is outside the change amount threshold range, the protruding control action is performed. The situation of being in this state is for grinding the edge of the workpiece. When the machine tool makes the grinding tool retract from the workpiece, in the case of the machine tool side performing movement control to reduce the movement speed of the moving grinding tool. In this case, if the protruding control action is performed, the grinding tool can be advanced and the abrasive can reliably contact the edge of the workpiece. Here, if the grinding tool completely retracts from the workpiece, the load becomes zero. Therefore, at the moment when the load becomes zero, the protruding control action stops.

[0019] In the present invention, it can be set that if the load is outside the load threshold range and the change amount is above the change amount threshold, while setting the state such that the protruding control action is not performed, the duration during which the state where the load is outside the load threshold range and the change amount is above the change amount threshold continues is counted until the duration reaches a preset set time, maintaining the state where the protruding control action is not performed. When the duration exceeds the set time, the protruding control action is restarted. Thus, when there is a notch or a depression in the machining path, the grinding tool can be made not to perform the protruding control action when passing through the notch or the depression.

[0020] In the present invention, it can be set that: a plurality of the load threshold ranges corresponding to the length dimension of the abrasive in the axial direction are pre-held as the load threshold ranges. Before the grinding tool holder is moved by the machine tool, the mounting portion on which the grinding tool is mounted is arranged at an initial position capable of advancing and retreating in the axial direction. Each time the mounting portion is moved during the protrusion control operation, the moving amount of the mounting portion moving from the initial position toward the side opposite to the mechanical mounting portion is calculated based on the driving amount of the drive source and the moving direction of the mounting portion, and one of the load threshold ranges is selected from the plurality of load threshold ranges based on the moving amount. Thus, the moving amount of the mounting portion moving from the initial position toward the side opposite to the mechanical mounting portion corresponds to the wear amount of the abrasive. Therefore, if one of the load threshold ranges is selected from the plurality of load threshold ranges based on the moving amount (wear amount of the abrasive), it becomes easy to maintain the cutting ability of the abrasive fixed.

[0021] In the present invention, it can be set that: the first load threshold range and the second load threshold range different from the first load threshold range are pre-held as the load threshold ranges. The first load threshold range is set as the load threshold range, the number of times when the load becomes zero is counted, and when the number reaches a specified set number, the load threshold range is set as the second load threshold range. Thus, in the case where the grinding tool moving along the machining path repeatedly advances and retreats with respect to the machining object surface of the workpiece, the load threshold range can be set as the first load threshold range until the number of times the grinding tool retreats from the machining object surface reaches the set number, and thereafter, the load threshold range is set as the second load threshold range. Thus, in the middle of the machining path, the cutting amount of the abrasive with respect to the workpiece can be adjusted.

[0022] In the present invention, a storage portion is included in advance. The grinding tool holder is moved by the machine tool along a pre-specified learning path, the output from the load detector is monitored, and the change amount of the load per unit time is sequentially calculated. The load threshold range is set based on the load, and the change amount threshold is set based on the change amount and they are stored and held in the storage portion. When the machine tool moves the grinding tool holder along the machining path, the load threshold range and the change amount threshold are acquired by referring to the storage portion. Thus, it becomes easy to set the load threshold range and the change amount threshold.

[0023] In the present invention, it can be set that: the grinding tool includes: an abrasive, the length direction of which faces the axial direction; and an abrasive holder for holding one end of the abrasive in the axial direction, and the abrasive holder is mounted on the mounting portion.

[0024] Next, the abrasive tool holder of the present invention is characterized by including: a mechanical mounting portion; a mounting portion on which an abrasive tool having an abrasive is mounted; a moving mechanism having a drive source and moving the mounting portion in the axial direction of the mechanical mounting portion; a load detector for detecting the load applied to the abrasive tool mounted on the mounting portion; and a control portion that monitors the output from the load detector and sequentially calculates the change amount of the load per unit time, and drives the drive source based on the load and the change amount to move the mounting portion, thereby performing a protrusion control action for advancing and retracting the abrasive tool.

[0025] The abrasive tool holder of the present invention is used in a state where an abrasive tool having an abrasive is mounted on the mounting portion and a grinding tool is constituted by the abrasive tool and the abrasive tool holder. According to the present invention, during the movement of the grinding tool along a machining path preset by a machine tool, the output from the load detector is monitored, and the change amount of the load per unit time is sequentially calculated, and the drive source is driven based on the load and the change amount to perform a protrusion control action for advancing and retracting the abrasive tool. Therefore, based on the change amount of the load, the abrasive tool holder can determine whether it is in a state where the abrasive tool is in contact with the machining object surface of the workpiece. Thus, if the protrusion control action is performed based on the load and the change amount of the load, the abrasive tool holder can perform the protrusion control action of protruding the abrasive tool toward the workpiece side only when the abrasive tool is in contact with the machining object surface of the workpiece.

[0026] In the present invention, it can be set that: when the load is outside a preset load threshold range and the change amount is smaller than a preset change amount threshold, the control portion can perform the protrusion control action. Thus, the abrasive tool holder can perform the protrusion control action when the abrasive tool is in a state of grinding the machining object surface of the workpiece and in a state where the load changes due to the wear of the abrasive caused by grinding.

[0027] In the present invention, it can be set that: the control portion stops the protrusion control action when the load is zero, and maintains a state of not performing the protrusion control action until the change amount is lower than a preset set change amount. Thus, the abrasive tool holder can be in a state of not performing the protrusion control action during the period when the grinding tool is outside the machining object surface of the workpiece and until the grinding tool feeds from outside the workpiece to the workpiece.

[0028] In the present invention, it can be set that when the load is outside the load threshold range and the change amount is within the specified change amount threshold range, the protruding control action is not performed, and when the load is outside the load threshold range and the change amount is outside the change amount threshold range, the protruding control action is performed. Thus, when the grinding tool holder retracts the grinding tool from the machining target surface of the workpiece, the state where the protruding control action is not performed can be set. In addition, when the grinding tool retracts from the machining target surface of the workpiece, when the machine tool reduces the moving speed of the moving grinding tool holder, etc., the grinding tool holder performs the protruding control action, and the edge of the workpiece can be reliably ground by the abrasive.

[0029] In the present invention, it can be set that there is a timer. In the control unit, if the load is outside the load threshold range and the change amount is equal to or more than the change amount threshold, while setting the state where the protruding control action is not performed, the timer is driven to count the duration during which the load is outside the load threshold range and the change amount is equal to or more than the change amount threshold. Until the duration reaches a preset set time, the state where the protruding control action is not performed is maintained, and when the duration exceeds the set time, the protruding control action is restarted. Thus, in the workpiece, when there are a plurality of small notch portions or a plurality of small depressions provided on the machining path through which the grinding tool passes, the protruding control action can be not performed in the section passing through these notch portions or depressions.

[0030] In the present invention, it can be set that there is a load threshold storage unit that stores a plurality of load threshold ranges corresponding to the length dimension of the abrasive in the axial direction as the load threshold ranges. The control unit includes: an initial action control unit for arranging the mounting portion at an initial position capable of advancing and retreating in the axial direction; and a load threshold range resetting unit that, each time the mounting portion is moved during the protruding control action, calculates the moving amount of the mounting portion moving from the initial position toward the side opposite to the mechanical mounting portion based on the driving amount of the drive source and the moving direction of the mounting portion, and based on the moving amount and referring to the load threshold storage unit, selects one of the plurality of load threshold ranges. Thus, it becomes easy to maintain the cutting ability of the abrasive fixed.

[0031] In the present invention, it can be set that there is a load threshold storage unit which stores and holds a first load threshold range and a second load threshold range different from the first load threshold range as the load threshold range. The control unit has: a counting unit which counts the number of times when the load becomes zero; and a load threshold range resetting unit which sets the first load threshold range as the load threshold range until the number of times reaches a specified set number of times, and when the number of times reaches the set number of times, sets the load threshold range as the second load threshold range. Thus, in the case where a grinding tool moving along a machining path repeatedly advances and retracts with respect to a machining target surface of a workpiece, the load threshold range can be set as the first load threshold range until the number of times the grinding tool retracts from the machining target surface reaches the set number of times, and thereafter, the load threshold range is set as the second load threshold range. Thereby, in the middle of the machining path, the cutting amount of the abrasive against the workpiece can be adjusted.

[0032] In the present invention, it can be set that the control unit includes: an operation mode switching unit which switches the operation mode of the control unit between a normal operation mode and a learning operation mode; and a learning data setting unit which, in the learning operation mode, monitors the output from the load detector, and sequentially calculates the change amount of the load per unit time, sets the load threshold range based on the load, and sets a change amount threshold based on the change amount and stores and holds it in the storage unit. In the normal operation mode, the control unit refers to the storage unit and obtains the load threshold range and the change amount threshold from the storage unit. Thus, it becomes easy to set the load threshold range and the change amount threshold.

[0033] Next, the grinding tool of the present invention includes: the above-mentioned grinding tool holder; and a grinding tool which is detachably mounted on the mounting portion of the grinding tool holder. The grinding tool has: an abrasive whose longitudinal direction faces the axial direction; and an abrasive holder which holds one end of the abrasive in the axial direction, and the abrasive holder is mounted on the mounting portion.

[0034] Advantages of the Invention

[0035] The grinding tool holder of the present invention performs a protrusion control action based on the load and the change amount of the load. Thus, the grinding tool can perform the protrusion control action of moving the grinding tool only when the grinding tool contacts the machining target surface of the workpiece. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 is a perspective view of the grinding tool.

[0037] Figure 2 It is a perspective view of the grinding tool.

[0038] Figure 3 It is an explanatory diagram of the brief structure of the grinding tool.

[0039] Figure 4 It is an explanatory diagram of the load applied to the grinding tool when the grinding tool moves on the machining path.

[0040] Figure 5 It is a brief block diagram showing the control system of the grinding tool holder.

[0041] Figure 6 It is a flowchart of the protrusion control action when the grinding tool passes through the workpiece.

[0042] Figure 7 It is a graph showing the load and the amount of change when the grinding tool performs the protrusion control action.

[0043] Figure 8 It is a flowchart of the protrusion control action when the grinding tool feeds into the workpiece.

[0044] Figure 9 It is a flowchart of the protrusion control action when the grinding tool retracts from the workpiece.

[0045] Figure 10 It is a flowchart of the protrusion control action when there is a notch in the machining path.

[0046] Figure 11 It is an explanatory diagram of the load and the amount of change when there is a notch in the machining path.

[0047] Figure 12 It is a flowchart of the protrusion control action of the grinding tool of the modified example.

[0048] Figure 13 It is an explanatory diagram of the load threshold range in the case of changing the load threshold range based on the length dimension of the abrasive bundle.

[0049] Figure 14 It is an explanatory diagram of the case of changing the load threshold range when the grinding tool feeds into or retracts from the workpiece.

[0050] Figure 15 It is a flowchart of the protrusion control action when the grinding tool feeds into or retracts from the workpiece.

[0051] Figure 16 It is a perspective view of the grinding tool including an elastic grinding stone as the abrasive.

[0052] Figure 17It is a perspective view of an abrasive tool including a rigid grinding stone as an abrasive. Detailed implementation mode

[0053] Hereinafter, with reference to the accompanying drawings, an abrasive tool holder as an embodiment of the present invention will be described. Figure 1 It is a perspective view of the appearance of an abrasive tool to which the present invention is applied. Figure 2 It is a perspective view of an abrasive tool. Figure 3 It shows Figure 1 An explanatory diagram of the brief structure of the abrasive tool. Figure 3 In [the figure], the abrasive tool is shown cut along the axis of the mechanical mounting portion. Figure 4 It is an explanatory diagram of the load applied to the abrasive tool during the movement of the abrasive tool along the machining path. Figure 4 The upper part of [the figure] shows the positional relationship between the abrasive tool and the workpiece. Figure 4 The lower part of [the figure] is a graph of the load applied to the abrasive tool from the workpiece side.

[0054] (Abrasive tool)

[0055] As Figure 1 shown, the abrasive tool 1 includes: an abrasive tool 3, and an abrasive tool holder 4 for holding the abrasive tool 3. The abrasive tool holder 4 includes: a shank portion 6 (mechanical mounting portion), and a sleeve 7 coaxial with the shank portion 6. Between the shank portion 6 and the sleeve 7, a large-diameter portion 8 having a larger diameter than the shank portion 6 and the sleeve 7 is provided. The abrasive tool 3 holds the end portion of the linear abrasive 2 (abrasive) in a state protruding from the sleeve 7 on the abrasive tool holder 4. In the following description, the direction along the axis L of the shank portion 6 is taken as the axis direction X. Further, in the axis direction X, the side of the shank portion 6 is taken as the rear X1 of the abrasive tool holder 4, and the side opposite to the shank portion 6 is taken as the front X2 of the abrasive tool holder 4.

[0056] (Abrasive tool)

[0057] As Figure 2 shown, the abrasive tool 3 has: a plurality of linear abrasives 2 arranged side by side, and an abrasive holder 11 for holding one end portion of the plurality of linear abrasives 2. Each linear abrasive 2 includes: a collective wire of inorganic long fibers such as alumina long fibers, and a resin impregnated in the collective wire and hardened. The linear abrasive 2 has elasticity bent in a direction crossing the axis L. The plurality of linear abrasives 2 are bundled into a bundle.

[0058] The abrasive holder 11 is an annular member, and includes a holder through hole 12 extending in the axis direction X at the center. Further, the abrasive holder 11 has a plurality of abrasive holding holes 13 on its front end face. Each abrasive holding hole 13 is circular. The plurality of abrasive holding holes 13 are provided at equal angular intervals around the axis L and surround the holder through hole 12. Further, the abrasive holder 11 is asFigure 3 As shown, it includes a recess on its rear end face that surrounds the through-hole 12 of the holding seat. The recess is a grinding tool side connecting portion 15 for detachably mounting the grinding tool 3 to the grinding tool holding seat 4.

[0059] When a plurality of linear abrasives 2 are held in the abrasive holding holes 13, they are bundled as an abrasive bundle 14. The rear end portion of the abrasive bundle 14 is inserted into the abrasive holding holes 13. Each abrasive bundle 14 is fixed to the abrasive holding seat 11 by an adhesive filled in the abrasive holding holes 13.

[0060] (Grinding tool holding seat)

[0061] As Figure 3 shown, the grinding tool holding seat 4 has: a shank portion 6; a mounting portion 21 for detachably mounting the grinding tool 3; a moving mechanism 22 for moving the mounting portion 21 in the axial direction X; and a load detector 23 for detecting the load applied to the grinding tool 3 mounted on the mounting portion 21. The shank portion 6 projects rearward X1 from the large-diameter portion 8.

[0062] The mounting portion 21 is an annular member. The mounting portion 21 is disposed in the sleeve 7 in a state of being movable along the axial direction X. The mounting portion 21 includes: a disk portion 25 having an annular opposing surface 25a that is spaced apart from the inner peripheral surface 7b of the sleeve 7 by a small gap, and a protrusion 26 that projects forward X2 from the center of the disk portion 25. The protrusion 26 has a shape that engages with the grinding tool side connecting portion 15 of the grinding tool 3. The grinding tool 3 is detachably mounted to the grinding tool holding seat 4 by engaging the grinding tool side connecting portion 15 with the protrusion 26 of the mounting portion 21. In a state where the grinding tool 3 is connected to the mounting portion 21, the grinding tool 3 and the mounting portion 21 are integrated in a state where they cannot rotate relative to each other about the axis L. An internal thread 29 is provided on the inner peripheral surface of the central hole 28 of the mounting portion 21.

[0063] The moving mechanism 22 includes: a shaft member 36 extending in the axial direction X; a support member 37 that supports the shaft member 36 so as to be movable along the axial direction X and rotatable about the axis L; a motor 35 as a drive source; and a driving force transmission mechanism 38 that transmits the rotation of the motor 35 to the shaft member 36. In addition, the moving mechanism 22 includes a rotation restricting mechanism 40 that restricts the rotation of the mounting portion 21 together with the shaft member 36.

[0064] The shaft member 36 is arranged on the axis L. The shaft member 36 includes an external thread 39 on its outer peripheral surface that is screwed with the internal thread 29 of the mounting portion 21. The support member 37 is an annular member that extends in a direction orthogonal to the axis L and has a through hole 41 extending in the direction of the axis L at its center. In front of the support member 37, a flange 7a that extends from the rear end portion of the sleeve 7 toward the outer peripheral side is fixed. The support member 37 and the flange of the sleeve 7 constitute the end wall of the front X2 of the large-diameter portion 8. In the through hole 41 of the support member 37, the shaft member 36 passes through. The rear end portion of the shaft member 36 that has passed through the through hole 41 protrudes toward the inside of the large-diameter portion 8. The front side portion of the shaft member 36 that has passed through the through hole 41 extends inside the sleeve 7 coaxially with the sleeve 7.

[0065] The motor 35 and the driving force transmission mechanism 38 are arranged inside the large-diameter portion 8 and are arranged behind the support member 37 in the X1 direction. The motor 35 is a stepping motor. The driving force transmission mechanism 38 includes: a final gear 45 that transmits the driving force of the motor 35, an output gear 46 that is coaxially fixed to the shaft member 36 and meshes with the final gear 45, and a biasing member 47 that biases the output gear 46 toward the support member 37. The final gear 45 is rotatably supported by a support shaft 48 that extends from the support member 37 toward the rear X1. The support shaft 48 is parallel to the shaft member 36. Therefore, the final gear 45 and the output gear 46 fixed to the shaft member 36 rotate around parallel rotation axes. The output gear 46 abuts against the support member 37 from the rear X1 by the acting force of the biasing member 47.

[0066] If the shaft member 36 moves toward the rear X1, the output gear 46 fixed to the shaft member 36 moves toward the rear X1 against the acting force of the biasing member 47. Therefore, when the shaft member 36 moves toward the rear X1, the shaft member 36 moves against the acting force of the biasing member 47. If the shaft member 36 moves toward the rear X1, the output gear 46 moves away from the support member 37 toward the rear X1.

[0067] Here, the shaft member 36 to which the output gear 46 is fixed is parallel to the rotation axis of the final gear 45. Therefore, even when the output gear 46 has moved in the axial direction X, the meshing state between the output gear 46 and the final gear 45 is maintained. Thus, the rotation of the motor 35 is always transmitted to the output gear 46 via the driving force transmission mechanism 38. If the driving force of the motor 35 is transmitted to the output gear 46, the shaft member 36 rotates around the axis L.

[0068] The rotation restricting mechanism 40 includes: a groove portion 31 provided on the inner peripheral surface 7b of the sleeve 7; and a protrusion 32 provided on a part of the circumferential direction of the opposing surface 25a of the mounting portion 21. The groove portion 31 extends in the axial direction X along the inner peripheral surface 7b of the sleeve 7. The protrusion 32 extends in the axial direction X with a certain width. Here, the mounting portion 21 is disposed within the sleeve 7 in a state where the protrusion 32 is inserted into the groove portion 31 of the sleeve 7. Therefore, when the shaft member 36 rotates, rotation of the mounting portion 21 can be prevented.

[0069] The load detector 23 is a pressure sensor. Inside the large-diameter portion 8, the load detector 23 is disposed behind the support member 37 in the X1 direction. The load detector 23 contacts the shaft member 36 from the rear X1 to detect the pressure applied to the shaft member 36 in the axial direction X.

[0070] When machining the workpiece W, the shank portion 6 of the grinding tool 1 is connected to the spindle N of the machine tool M, and the machine tool M is operated. Thereby, the machine tool M moves the grinding tool 1 along a machining path programmed in advance.

[0071] As Figure 4 shown, the machining path E along which the machine tool M moves the grinding tool 1 is set to start from the front of the workpiece W, pass through the workpiece W, and reach the rear of the workpiece W. Further, the machining path E is set such that the distance D between the spindle N and the machining target surface S of the workpiece W is maintained constant when the grinding tool 1 passes through the workpiece W. When the grinding tool 1 passes through the workpiece W, the front end portion of the abrasive bundle 14 contacts the machining target surface S.

[0072] (Control system)

[0073] Figure 5 is a schematic block diagram showing the control system of the grinding tool holder 4. Figure 6 is a flowchart of the protrusion control operation when the grinding tool 1 passes through the workpiece W. Figure 7 is a graph showing the load and the change amount during the protrusion control operation. Figure 8 is a flowchart of the protrusion control operation when the grinding tool 1 feeds into the workpiece W. Figure 9 is a flowchart of the protrusion control operation when the grinding tool 1 retracts from the workpiece W. Figure 10 is a flowchart of the protrusion control operation when there is a notch on the machining path. Figure 11 is an explanatory diagram of the load when there is a notch on the machining path. Figure 11 The upper part of [] shows the positional relationship between the grinding tool and the workpiece as viewed from the direction of the axis L. Figure 11 The lower part of [] is a graph of the load applied to the grinding tool from the workpiece side.

[0074] As Figure 5As shown, the control system of the grinding tool holder 4 includes: a control unit 51 having a CPU, a storage unit 52 connected to the control unit 51, and a timer 53. A load detector 23 is connected to the input side of the control unit 51. A motor 35 is connected to the output side of the control unit 51. In addition, as Figure 3 shown, the grinding tool holder 4 includes: a motor battery 57 that supplies power to the motor 35, a control unit 51, and a control battery 58 that supplies power to the timer 53. The motor battery 57 and the control battery 58 are connected from an external connection cable so that they can be charged.

[0075] Here, during the movement of the grinding tool 1 along the machining path E, the control unit 51 monitors the output (load) from the load detector 23 and sequentially calculates the change amount of the load per unit time specified in advance.

[0076] More specifically, the control unit 51 acquires the load output from the load detector 23 at a certain cycle, and obtains the change amount of the load per unit time from three loads obtained sequentially along the time series. Here, the load can be acquired at intervals of 0.001 seconds to 1 second. The unit time for calculating the change amount of the load is three times the interval for acquiring the load. The calculation of the change amount of the load is performed at the same interval as the interval for acquiring the load. The change amount is the absolute value of the amplitude of increase or decrease of the load (P) per unit time. When the unit time is set as dt and the amplitude of increase or decrease of the load is set as dP, it can be expressed by the following formula.

[0077] |dP / dt|

[0078] In addition, the control unit 51 performs a protrusion control action based on the sequentially acquired load and the change amount, and this protrusion control action is used to adjust the cutting amount of the abrasive bundle 14 with respect to the workpiece W.

[0079] More specifically, as Figure 6 shown, the control unit 51 monitors the load and sequentially calculates the change amount (step ST1). When the change amount is smaller than a preset change amount threshold Q (step ST2: Yes), if the load is outside a preset load threshold range R (step ST3: Yes), the control motor 35 is driven to move the mounting portion 21, and a protrusion control action for advancing and retracting the grinding tool 3 is performed (step ST4). On the other hand, if the change amount is equal to or greater than the change amount threshold Q (step ST2: No), the control unit 51 does not perform the protrusion control action (step ST5). In addition, even when the change amount is smaller than the change amount threshold Q (step ST2: Yes), and when the load is within the load threshold range R (step ST3: No), the control unit 51 does not perform the protrusion control action (step ST5). In the section K1 where the grinding tool 1 passes through the machining object surface S of the workpiece W (please refer to Figure 4)Perform the above control within

[0080] Here, it is possible to preliminarily grasp, through experiments or the like, the standard change amount of the load that changes during the period when the grinding tool 3 grinds the machining target surface S of the workpiece W in the grinding operation of the workpiece W. Therefore, as long as a change amount threshold Q is preset in advance based on the change amount obtained through experiments or the like and stored in the storage unit 52, the control unit 51 refers to the storage unit 52 and, when the change amount is equal to or greater than the change amount threshold Q, determines that the change in the load is not caused by the wear of the abrasive bundle 14 but by other factors. In other words, as long as the change amount threshold Q is preset in advance based on experiments or the like, when the change amount is smaller than the change amount threshold Q, the control unit 51 can determine that the grinding tool 3 is in the state of grinding the machining target surface S of the workpiece W, and the load changes due to the wear of the abrasive bundle 14 caused by grinding.

[0081] In addition, it is possible to preliminarily grasp, through experiments or the like, the range of the load when the grinding tool 3 grinds the machining target surface S of the workpiece W with a desired cutting amount in the state where the grinding tool 3 grinds the machining target surface S of the workpiece W. Therefore, based on the experimental results, the lower limit of the load suitable for grinding the workpiece W, that is, the first threshold R1, and the upper limit of the load suitable for grinding, that is, the second threshold R2, are grasped. If the range between the first threshold R1 and the second threshold R2 is set as the load threshold range R and stored in the storage unit 52, the control unit 51 refers to the storage unit 52 and, when the load deviates from the load threshold range R due to the wear of the abrasive bundle 14 or the like, determines that the cutting amount of the abrasive bundle 14 with respect to the workpiece W is lower than the appropriate range. In addition, when the load deviates from the load threshold range R, the control unit 51 can determine that the cutting amount of the abrasive bundle 14 with respect to the workpiece W exceeds the appropriate range. In addition, both the first threshold R1 and the second threshold R2 are values greater than zero.

[0082] Here, refer to Figure 7 Describe the protrusion control operation. Figure 7 It is a graph showing the relationship between the output from the load detector 23 and the protrusion control operation. Figure 7 The moment G of the graph is the moment when the change amount (|dP / dt|) is smaller than the change amount threshold Q (|dP’ / dt|) and the output from the motor 35 drops below the preset first threshold R1. At moment G, the control unit 51 drives the motor 35 in the specified rotation direction to move the mounting portion 21 forward in the X2 direction. And, when the control unit 51 drives the motor 35 and moves the mounting portion 21, it monitors the output from the motor 35. If the output reaches the second threshold R2, it stops driving the motor 35 and stops the movement of the mounting portion 21 based on the monitored output.

[0083] Next, Figure 7The moment H of the curve graph is the moment when the change amount (|dP / dt|) is smaller than the change amount threshold Q and the output from the motor 35 rises above a preset second threshold R2. At moment H, the control unit 51 drives the motor 35 in the direction opposite to the specified rotation direction to move the mounting unit 21 toward the rear X1. Further, when driving the motor 35 to move the mounting unit 21, the control unit 51 monitors the output from the motor 35, and if the output is lower than the second threshold R2, it stops driving the motor 35 and stops the movement of the mounting unit 21 based on the monitored output. Thereby, when the grinding tool 3 is in a state of grinding the machining object surface S of the workpiece W and in a state where the load changes due to the wear of the abrasive bundle 14 caused by grinding, the grinding tool 1 performs a protrusion control operation to maintain the cutting amount of the abrasive bundle 14 with respect to the workpiece W within an appropriate range.

[0084] In addition, as Figure 8 shown, the control unit 51 monitors the load and sequentially calculates the change amount (step ST11), stops the protrusion control operation when the load is zero (steps ST12 and ST13), and maintains a state where the protrusion control operation is not performed until the change amount is lower than a preset set change amount U (step ST14: No, step ST13). As Figure 4 shown, the above control is performed in an interval K2 from when the grinding tool 1 outside the workpiece W advances to the machining object surface S of the workpiece W.

[0085] That is, as Figure 4 shown, when the grinding tool 1 is outside the machining object surface S of the workpiece W, the grinding tool 3 does not contact the workpiece W. Therefore, the load applied to the grinding tool 3 is zero. Thus, if the load is zero, the control unit 51 can determine that the grinding tool 1 is outside the machining object surface S of the workpiece W. Here, when the grinding tool 1 is outside the machining object surface S of the workpiece W, wear does not occur on the abrasive bundle 14. Therefore, the control unit 51 is set to a state where the protrusion control operation is not performed.

[0086] Thereafter, as Figure 4As shown, when the grinding tool 1 feeds from outside the workpiece W to the machining target surface S of the workpiece W, when the grinding tool 1 (abrasive bundle 14) contacts the workpiece W, the change amount of the load suddenly becomes large. Moreover, at the moment J when the feeding to the workpiece W ends, the change amount of the load exceeds the peak value and then decreases. Therefore, at the moment when the feeding of the grinding tool 1 to the workpiece W ends, the change amount becomes a value close to zero. Thus, by presetting the set change amount U to a value close to zero, etc., as long as the control unit 51 stops the protrusion control operation when the load is zero and maintains the state of not performing the protrusion control operation until the change amount is lower than the preset set change amount U, the protrusion control operation can be not performed until the grinding tool 1 feeds onto the workpiece W, and after the grinding tool 1 feeds onto the workpiece W, the protrusion control operation can be performed.

[0087] In addition, in the control unit 51, as Figure 9 shown, the control unit 51 monitors the load and sequentially calculates the change amount (step ST21). When the load is outside the load threshold range R (step ST22) and the change amount is within the specified change amount threshold range V (step ST23: YES), the protrusion control operation is not performed (step ST23). On the other hand, when the load is outside the load threshold range R (step ST22: NO) and the change amount is outside the change amount threshold range V, the control unit 51 performs the protrusion control operation (step ST24). As Figure 4 shown, the above control is performed from the state where the grinding tool 1 contacts the machining target surface S of the workpiece W until it moves away from the workpiece W.

[0088] That is, when the grinding tool 1 retracts from the machining target surface S of the workpiece W, as Figure 4 shown, when the abrasive bundle 14 passes through the edge of the workpiece W, the load applied to the grinding tool 3 from the workpiece W side suddenly decreases. Therefore, when the abrasive bundle 14 passes through the edge of the workpiece W, the change amount of the load will suddenly become large. Here, the change amount of the load that suddenly decreases when the grinding tool 1 retracts from the workpiece W can be grasped in advance through experiments, etc. Therefore, if a specified range including the change amount grasped through experiments, etc. is preset as the change amount threshold range V and stored in the storage unit 52, the control unit 51 can determine that the grinding tool 1 is in the middle of retracting from the machining target surface S of the workpiece W when the change amount of the load is within the change amount threshold range V. Thus, even when the load is outside the load threshold range R, when the change amount is within the change amount threshold range V (step ST22, step ST23: YES), if it is set that the control unit 51 does not perform the protrusion control operation (step ST25), unnecessary protrusion control operations can be not performed when the grinding tool 1 retracts from the machining target surface S of the workpiece W.

[0089] On the other hand, when the load is outside the load threshold range R and the variation is outside the variation threshold range V (step ST22, step ST23: No), the control unit 51 performs a protrusion control action. When the load is outside the load threshold range R, the variation is outside the variation threshold range V, for example, when the machine tool M retracts the grinding tool 1 from the workpiece W, the machine tool M side performs a movement control to reduce the moving speed of the moving grinding tool 1. In this case, if the protrusion control action is performed, the grinding tool 3 can be advanced and the abrasive beam 14 can reliably contact the end edge of the workpiece W. When the load is outside the load threshold range R, the variation is outside the variation threshold range V, for example, when the machine tool M retracts the grinding tool 1 from the workpiece W, the machine tool M side performs a movement control to slowly move the grinding tool 1 in a direction away from the processing target surface S. In this case, if the protrusion control action is performed, the grinding tool 3 can be advanced and the abrasive beam 14 can reliably contact the end edge of the workpiece W. In any case, when the grinding tool 1 is retracted from the workpiece W, the load becomes zero. Therefore, at the moment when the load becomes zero, the protrusion control action stops.

[0090] In addition, if Figure 10 As shown, the control unit 51 monitors the load and calculates the change in sequence (step ST31). If the load is outside the load threshold range R and the change is greater than the change threshold Q (step ST32), the protrusion control action is not performed, and the duration of the state in which the load is outside the threshold range and the change is greater than the change threshold Q is counted by the timer 53 (step ST33). Moreover, the control unit 51 maintains the state in which the protrusion control action is not performed from the time when the load is outside the load threshold range R and the duration from the moment when the change becomes greater than the change threshold Q reaches a predetermined set time, and restarts the protrusion control action when the duration exceeds the set time (step ST34: yes, step ST35). On the other hand, the control unit 51 does not perform the protrusion control action when the duration does not exceed the set time (step ST34: no, step ST36). As shown Figure 11 As shown in the upper section of , the above control is used to prevent unnecessary protrusion control actions from being performed when there is a section K4 with a notch L or a depression on the processing path E of the grinding tool 1 passing through the workpiece W while the grinding tool 1 passes through these notches L or depressions.

[0091] That is, when there is a notch L or a depression on the processing target surface S of the workpiece W, when the grinding tool 1 passes through the notch L or the depression, the contact area of ​​the grinding tool 3 (abrasive beam 14) contacting the workpiece W is sharply reduced. Figure 11As shown in the lower part, the load applied from the workpiece W side to the abrasive tool 3 side drops sharply and is outside the load threshold range R. In addition, along with the sharp drop in the load, the change amount of the load becomes much larger compared with the change amount of the load caused by the wear of the abrasive bundle 14. Therefore, when the load is outside the load threshold range R and the change amount is equal to or greater than the change amount threshold Q (|dP’ / dt|), the control unit 51 can determine that a notch L or a depression is provided on the machining target surface S of the workpiece W. In other words, when the load is outside the load threshold range R and the change amount is equal to or greater than the change amount threshold Q, the control unit 51 can determine that the load being outside the load threshold range R is not caused by the wear of the abrasive bundle 14 but by the shape of the machining target surface S. Therefore, if the load is outside the load threshold range R and the change amount is equal to or greater than the change amount threshold Q, the control unit 51 sets it to a state where the protrusion control operation is not performed. Thereby, it is prevented that the abrasive bundle 14 protrudes when the grinding tool 1 faces the notch L or the depression.

[0092] In addition, after stopping the protrusion control operation, the control unit 51 counts the duration during which the load is outside the threshold range and the change amount is equal to or greater than the change amount threshold Q by means of the timer 53 until the duration reaches a preset set duration, and maintains the state where the protrusion control operation is not performed. Therefore, by presetting the set time to an appropriate value, it can be set that the protrusion control operation is not performed during the period when the grinding tool 1 passes through the notch L or the depression. Thereby, it is prevented that the abrasive bundle 14 protrudes during the period when the grinding tool 1 passes through the notch L or the depression.

[0093] (Protrusion control operation during the movement of the grinding tool along the machining path)

[0094] As Figure 4 shown, the machining path E along which the machine tool M moves the grinding tool 1 is set to pass from the front of the workpiece W through the workpiece W and then reach the rear of the workpiece W. The abrasive tool holder 4 monitors the output from the load detector 23 during the movement of the grinding tool 1 along the machining path E, and sequentially calculates the change amount of the load, and drives and controls the drive source (motor 35) based on the load and the change amount to perform the protrusion control operation for advancing and retracting the abrasive tool 3.

[0095] As Figure 4As shown, the grinding tool 1 is located in the section K2 in front of the workpiece W. Until the grinding tool 3 contacts the workpiece W, the output from the load detector 23 is zero. Therefore, the control unit 51 stops the protrusion control operation. In addition, after stopping the protrusion control operation until the change amount is lower than the set change amount U, the control unit 51 maintains the state of not performing the protrusion control operation. After the change amount is lower than the set change amount U, the control unit 51 sets it to a state where the protrusion control operation can be performed. Thus, when the grinding tool 1 advances toward the workpiece W, until it advances onto the workpiece W, it is in a state of not performing the protrusion control operation, and after advancing onto the workpiece W, it is in a state where the protrusion control operation can be performed.

[0096] Next, in the section K1 where the grinding tool 1 passes through the grinding target surface S of the workpiece W, as Figure 7 shown, when the load of the grinding tool 1 is outside the load threshold range R and the change amount is smaller than the change amount threshold Q, the protrusion control operation is performed. That is, the grinding tool 1 performs the protrusion control operation when it is determined that it is in a state where the grinding tool 3 grinds the processing target surface S of the workpiece W and is in a state where the load changes due to the wear of the abrasive bundle 14 caused by grinding.

[0097] In the protrusion control operation, when the output from the load detector 23 is lower than the first threshold R1, the grinding tool 1 drives the motor 35 to move the mounting portion 21 forward in the X2 direction. In addition, when the grinding tool 1 drives the motor 35 to move the mounting portion 21, it monitors the output (load) from the motor 35. When the load reaches the second threshold R2, it stops driving the motor 35 to stop the movement of the mounting portion 21. Thus, since the grinding tool 3 advances when the abrasive bundle 14 wears and the cutting amount decreases, the cutting amount can be ensured.

[0098] In addition, in the protrusion control operation, when the output from the load detector 23 exceeds the preset second threshold R2, the control unit 51 drives the motor 35 to move the mounting portion 21 backward in the X1 direction. In addition, when the control unit 51 drives the motor 35 to move the mounting portion 21, it monitors the output (load) from the motor 35. When the load reaches the second threshold R2, it stops driving the motor 35 to stop the movement of the mounting portion 21. Here, the situation where the output from the load detector 23 exceeds the preset second threshold R2 means that due to dimensional errors of the workpiece W or the like, the distance between the spindle N of the machine tool M and the processing target surface S of the workpiece W becomes shorter than the predetermined distance, and the cutting amount of the abrasive bundle 142 into the workpiece W exceeds the appropriate range and increases. In this case, if the control unit 51 drives the motor 35 to move the mounting portion 21 backward in the X1 direction, the grinding tool 3 moves away from the workpiece W. Therefore, the cutting amount of the abrasive bundle 14 is reduced, and the machining accuracy of the grinding tool 1 with respect to the workpiece W can be maintained.

[0099] In addition, as Figure 4 shown, in the section K4 where the grinding tool 1 passes through the grinding target surface S of the workpiece W, if the load is outside the load threshold range R and the change amount is equal to or more than the change amount threshold Q, the control unit 51 sets the state where the protrusion control operation is not performed, and counts the duration during which the load is outside the load threshold range R and the change amount is equal to or more than the change amount threshold Q until the duration reaches a preset set duration, and maintains the state where the protrusion control operation is not performed. Moreover, when the duration exceeds the set duration, the control unit 51 sets the state where the protrusion control operation can be performed. Therefore, on the machining path E, as Figure 11 shown, when there are notch portions L provided, unnecessary protrusion control operations do not need to be performed during the period of passing through these notch portions L.

[0100] Thereafter, as Figure 4 shown, in the section K3 where the grinding tool 1 retracts from the machining target surface S of the workpiece W and reaches the rear of the workpiece W, when the load is outside the load threshold range R and the change amount is within the specified change amount threshold range V, the protrusion control operation is not performed. That is, when the change amount is within the preset change amount threshold range V, the grinding tool 1 determines that the decrease in the load is not caused by the wear of the abrasive bundle 14 but by the retraction of the grinding tool 1 from the workpiece W, and does not perform the protrusion control operation. Thus, when the grinding tool 1 retracts from the workpiece W, unnecessary protrusion control operations can be avoided.

[0101] In addition, in the section K3 where the grinding tool 1 retracts from the machining target surface S of the workpiece W and reaches the rear of the workpiece W, when the load is outside the load threshold range R and the change amount is outside the change amount threshold range V, the protrusion control operation is performed. In such a case, sometimes special movement control of the grinding tool 1 is performed on the machine tool M side. In this case, if the control unit 51 performs the protrusion control operation, the grinding tool 3 can be advanced and the abrasive bundle 14 can be reliably brought into contact with the edge of the workpiece W.

[0102] Here, if the grinding tool 1 completely retracts from the workpiece W, the load becomes zero. Therefore, at the moment when the load becomes zero, the protrusion control operation stops.

[0103] (Function and effect)

[0104] According to this example, the grinding tool holder 4 can determine whether the grinding tool 3 is in a state of contacting the machining target surface S of the workpiece W based on the change amount of the load. Therefore, if the protrusion control operation is performed based on the load and the change amount of the load, the grinding tool 1 can perform the protrusion control operation of protruding the grinding tool 3 toward the workpiece W only when the grinding tool 3 contacts the machining target surface S of the workpiece W.

[0105] (Variant Example 1)

[0106] Figure 12 It is a flowchart of the protrusion control operation of the grinding tool 1 in Variant Example 1. The grinding tool 1 can have: a normal operation mode for performing the machining operation as described above, and a learning operation mode for setting the load threshold range R and the change amount threshold Q, as the operation modes of the control unit 51.

[0107] In this case, as Figure 5 shown by the dashed line in, the control unit 51 includes an operation mode switching unit 60, and the operation mode switching unit 60 switches the operation mode of the control unit 51 between the normal operation mode and the learning operation mode. In addition, in this case, the control unit 51 includes a learning data setting unit 61, and the learning data setting unit 61 sets the load threshold range R, the change amount threshold Q, and the change amount threshold range V according to the learned data in the learning operation mode, and stores and holds them in the storage unit 52.

[0108] In this example, as Figure 12 shown, in order to set the load threshold range R and the change amount threshold Q, first, the operation mode of the control unit 51 is set to the learning operation mode (step ST41). Secondly, the shaft of the grinding tool 1 is connected to the main shaft N of the machine tool M and the machine tool M is operated to move the grinding tool 1 along a preset learning path. The learning path includes: a machining path portion ([[]] Figure 4 interval K1) where the flat machining target surface S of the workpiece W is ground by the grinding tool 1, and a machining exit path portion ([[]] Figure 4 interval K3 in) where the grinding tool 1 is retracted from the machining target surface S to move away from the workpiece W. When the grinding tool 3 faces the machining target surface S of the workpiece W in the machining path portion (interval K1), the distance between the main shaft N of the machine tool M and the machining target surface S is maintained fixed. In addition, in the machining path portion (interval K1), the state where the abrasive bundle 14 contacts the surface of the workpiece W is maintained.

[0109] Here, when the grinding tool 1 passes through the machining path portion (interval K1), the learning data setting unit 61 monitors the output from the load detector 23, sequentially calculates the change amount of the load per unit time specified in advance, sets the load threshold range R based on the load, and sets the change amount threshold Q based on the change amount and stores and holds it in the storage unit 52 (step ST42).

[0110] That is, the learning data setting unit 61 obtains the first threshold R1, which is the lower limit of the load that can ensure the cutting amount suitable for grinding the workpiece W, and the second threshold R2, which is the upper limit of the load, based on the load output from the load detector 23 when the grinding tool 3 grinds the flat machining object surface S, and sets the range between them as the load threshold range R. When setting the load threshold range R based on the load detected in the learning operation mode, data in the form of a table that makes the load correspond to the change amount threshold range V, mathematical expressions representing the relationship between the load and the change amount threshold range V, etc. are stored and held in the storage unit 52 in advance. The learning data setting unit 61 automatically calculates the load threshold range R using the above data or mathematical expressions according to the load. In addition, the learning data setting unit 61 stores and holds the calculated load threshold range R in the storage unit 52.

[0111] In addition, the learning data setting unit 61 sets the lower limit of the change amount that can presume that the change in the load is caused by the wear of the abrasive bundle 14 as the change amount threshold Q based on the change amount of the load output from the load detector 23 when the grinding tool 3 grinds the flat machining object surface S. When setting the change amount threshold Q based on the change amount calculated in the learning operation mode, data in the form of a table that makes the change amount correspond to the change amount threshold Q, mathematical expressions representing the relationship between the change amount and the change amount threshold Q are stored and held in the storage unit 52 in advance, and the learning data setting unit 61 automatically calculates the change amount threshold Q using these data or mathematical expressions according to the change amount. In addition, the learning data setting unit 61 stores and holds the calculated change amount threshold Q in the storage unit 52 (step ST42).

[0112] In addition, when the grinding tool 1 passes through the processing outlet path portion, the learning data setting unit 61 controls the control unit 51 to monitor the output from the load detector 23, and sequentially calculates the change amount of the load per unit time specified in advance, and sets the change amount threshold range V based on the load. That is, the learning data setting unit 61 obtains the change amount of the load when the grinding tool 3 retracts from the flat processing object surface S, and sets the range including this change amount as the change amount threshold range V. When setting the change amount threshold range V based on the obtained change amount, data in the form of a table corresponding the change amount to the change amount threshold range V and a mathematical formula representing the relationship between the change amount and the change amount threshold range V are stored and held in the storage unit 52 in advance. The learning data setting unit 61 automatically calculates the load threshold range R using the above data or mathematical formula according to the change amount. In addition, the learning data setting unit 61 stores and holds the calculated change amount threshold range V in the storage unit 52 (step ST42).

[0113] Moreover, when the grinding tool 1 is moved along the processing path E by the machine tool M, the operation mode of the control unit 51 is switched from the learning operation mode to the normal operation mode (step ST43). In the normal operation mode, the control unit 51 refers to the storage unit 52 to obtain the load threshold range R, the change amount threshold Q, and the change amount threshold range V (step ST44).

[0114] In this example, by setting the operation mode of the control unit 51 as the learning operation mode and processing the workpiece W using the grinding tool 1, the load threshold range R, the change amount threshold Q, and the change amount range required for the protrusion control operation of the control unit 51 can be set.

[0115] (Modification Example 2)

[0116] Next, the grinding tool holder 4 can change the load threshold range R for performing the protrusion control operation during the processing operation. In Modification Example 2, the load threshold range R is changed based on the length dimension of the abrasive bundle 14. Figure 13 It is an explanatory diagram of the load threshold range R in the case where the load threshold range R is changed based on the length dimension of the abrasive bundle 14.

[0117] In this case, the grinding tool 1 stores and holds a plurality of load threshold ranges R corresponding to the length dimension of the abrasive bundle 14 in the axial direction L of the axis as the load threshold range R in the storage unit 52 (load threshold storage unit). In this example, as Figure 13As shown, a first mathematical formula for calculating the lower limit, i.e., the first threshold value R1, of the load threshold range R based on the length dimension of the abrasive bundle 14 and a second mathematical formula for calculating the upper limit, i.e., the second threshold value R2, of the load threshold range R based on the length dimension of the abrasive bundle 14 are stored and held in the storage unit 52 as a plurality of load threshold ranges R. In the first mathematical formula F1, as the length dimension of the abrasive bundle 14 becomes shorter, the first threshold value R1 becomes larger. In the second mathematical formula F2, as the length dimension of the abrasive bundle 14 becomes shorter, the second threshold value R2 becomes larger.

[0118] In addition, as Figure 5 shown by the dashed line, the control unit 51 includes an initial movement control unit 63 that configures the mounting unit 21 at an initial position where it can move forward and backward in the direction of the axis L. In addition, the control unit 51 includes a load threshold range re-setting unit 64 that, each time the mounting unit 21 is moved during the protrusion control operation, calculates the movement amount of the mounting unit 21 that moves from the initial position toward the side opposite to the handle portion 6 based on the driving amount of the motor 35 and the movement direction of the mounting unit 21, and selects one load threshold range R from the plurality of load threshold ranges R based on the movement amount and with reference to the load threshold storage unit 52.

[0119] In this example, before the grinding tool holder 4 is moved along the machining path E by the machine tool M, the mounting unit 21 on which the grinding tool 3 is mounted is configured at an initial position where it can move forward and backward in the direction of the axis L. In addition, during the movement of the grinding tool holder 4 along the machining path E by the machine tool M, the control unit 51 calculates the movement amount of the mounting unit 21 from the initial position, and selects one load threshold range R from the plurality of load threshold ranges R based on the movement amount. That is, the calculated movement amounts are respectively substituted into the first mathematical formula F1 and the second mathematical formula F2 to calculate the first threshold value R1 and the second threshold value R2 corresponding to the length dimension of the abrasive bundle 14.

[0120] Here, the longer the dimension in the axial direction L of the bundle of the elastic abrasive bundle 14 is, the more flexible it is, and thus the cutting ability is lower. However, if the wear amount increases and the length dimension in the axial direction L becomes shorter, the rigidity of the bundle of the abrasive bundle 14 increases and the cutting ability improves. In addition, the movement amount of the mounting unit 21 after moving from the initial position toward the side opposite to the handle portion 6 corresponds to the wear amount of the abrasive bundle 14. Therefore, it is easy to grasp the length dimension of the abrasive bundle 14 based on the movement amount. Therefore, if the movement amount (wear amount of the abrasive bundle 14) is substituted into the first mathematical formula F1 and the second mathematical formula F2 to obtain the load threshold range R, when the abrasive bundle 14 becomes shorter, the load threshold range R is advanced to a higher value, and the cutting ability of the bundle of the abrasive bundle 14 can be maintained constant. Thus, according to this example, regardless of the length dimension of the bundle of the abrasive bundle 14, the cutting ability of the bundle of the abrasive bundle 14 can be maintained constant.

[0121] (Modification Example 3)

[0122] As another example of changing the load threshold range R for performing the protrusion control operation during the machining operation, the abrasive tool holder 4 may also change the load threshold range R for performing the protrusion control operation before and after the load output from the load detector 23 becomes zero. Here, the moment when the load becomes zero refers to the moment when the grinding tool 1 retracts from the workpiece W in the middle of the machining path E.

[0123] Figure 14 It is an explanatory diagram of the case where the load threshold range R is changed when the grinding tool 1 advances into the workpiece W and retracts from the workpiece W. Figure 14 The upper part of [Figure] shows the positional relationship between the grinding tool 1 and the workpiece W. Figure 14 The lower part of [Figure] is a graph of the load applied to the abrasive tool 3 from the workpiece W side and the load threshold range. Figure 15 It is a flowchart of the protrusion control operation when the grinding tool advances into or retracts from the workpiece.

[0124] As shown in Figure 14 the upper part of [Figure], in this example, during the period from when the grinding tool 1 advances into the workpiece W to when it first retracts from the workpiece W, the workpiece W is machined in a state where 80% of the abrasive bundle 4 is in contact with the machining target surface S. Then, during the period from when the grinding tool 1 advances into the workpiece W to when it retracts from the workpiece W, the workpiece W is machined in a state where 20% of the abrasive bundle 4 is in contact with the machining target surface S.

[0125] In this case, in the storage unit 52, the first load threshold range R(1) and the second load threshold range R(2) different from the first load threshold range R(1) are held as the load threshold range R. In this example, the range of the second load threshold range R(2) is a value smaller than the first load threshold range R(1). Further, as shown by the dotted line in Figure 5 , the control unit 51 includes: a counting unit 65 that counts the number of times when the load becomes zero; and a load threshold range resetting unit 64 that sets the first load threshold range R as the load threshold range R until the number of times reaches a specified set number of times, and sets the load threshold range R as the second load threshold range R when the number of times reaches the set number of times.

[0126] Accordingly, in the protrusion control operation performed at the start of machining, the control unit 51 drives and controls the motor 35 based on whether the load is within the first load threshold range R(1) (step ST51). Further, the number of times the load becomes zero is counted (step ST52), and after the number of times the load becomes zero reaches the set number (one time in this example) (step ST53), the control unit 51 drives and controls the motor 35 based on whether the load is within the second load threshold range R (step ST54). Therefore, when the grinding tool 1 moving along the machining path E repeatedly advances and retracts with respect to the machining surface S of the workpiece W, after performing the set number of advances and retractions, and at the moment of advancing into the workpiece W, the cutting amount of the abrasive bundle 14 with respect to the workpiece W can be adjusted.

[0127] (Other Embodiments)

[0128] The abrasive tool 3 included in the grinding tool 1 may also have an elastic grinding stone as the abrasive. Figure 16 It is a perspective view of another abrasive tool included in the grinding tool. Figure 16 The illustrated abrasive tool 3A includes a cylindrical elastic grinding stone 2A extending in the axial direction X as the abrasive. Further, the abrasive tool 3A includes an abrasive holding seat for holding the elastic grinding stone 2A. Further, the shape of the elastic grinding stone 2A may also be set to a prismatic shape.

[0129] The elastic grinding stone 2A contains: an elastic foam, a polymer, and abrasive grains. The elastic foam is, for example, a melamine resin foam. Further, the elastic foam may be an anisotropic elastic foam that imparts anisotropy to the elastic force by being compressed in one direction. The polymer is any one of an epoxy resin, a polyurethane resin, a polyester resin, or a polyrotaxane. The abrasive grains can be appropriately selected according to the type of the workpiece W. As the abrasive grains, diamond, alumina, silica, silicon carbide, silicon nitride, boron carbide, titanium dioxide, cerium oxide, or zirconia can be used. The base material of the above-mentioned elastic grinding stone is obtained by impregnating a dispersion liquid containing a polymer and abrasive grains into the anisotropic elastic foam and firing it. In the anisotropic elastic foam, the direction in which the elastic force is maximum is the compression direction.

[0130] The abrasive holding seat 11 is an annular member and includes a holding seat through-hole 12 extending in the axial direction X at the center. Further, the abrasive holding seat 11 has a circular abrasive holding hole 13A on its front end face. The abrasive holding seat 11 holds one end in the axial direction X of the elastic grinding stone 2A. Further, the abrasive holding seat 11 has a recess surrounding the holding seat through-hole 12 on its rear end face. The recess is a grinding tool side connecting portion 15 for detachably mounting the grinding tool 3 to the grinding tool holding seat 4. The grinding tool 3A is held by the grinding tool holding seat 4 to constitute the grinding tool 1.

[0131] Here, when the abrasive is the elastic grinding stone 2A, since the longer the dimension in the axial direction X is, the more flexible it is, the cutting ability is lower. However, if the amount of wear increases and the length dimension of the abrasive in the axial direction becomes shorter, the rigidity increases and the cutting ability improves. In addition, when the abrasive is the elastic grinding stone 2A, the load output from the load detector 23 is the reaction force when the front end surface of the elastic grinding stone 2A is vertically pressed against the machining target surface S of the workpiece W during grinding. This reaction force is proportional to the contact area between the front end surface of the elastic grinding stone 2A and the machining target surface S of the workpiece W. Therefore, if the contact area is small, the load is small, and if the contact area is large, the load is large. Thus, even when the abrasive is the elastic grinding stone 2A, the present invention can be applied in the same manner as in the case of a bundle of linear abrasives 2.

[0132] Next, the abrasive tool 3 included in the grinding tool 1 may also include a rigid grinding stone as the abrasive. Figure 17 It is a perspective view of another abrasive tool included in the grinding tool. Figure 17 The illustrated abrasive tool 3B includes a rigid grinding stone 2B extending in the axial direction X as the abrasive. In addition, the abrasive tool 3B includes an abrasive holding seat 11 for holding the grinding stone 2B. The abrasive holding seat 11 is the same as the abrasive holding seat 11 of the illustrated abrasive tool 3A. Figure 16 The abrasive holding seat 11 of the illustrated abrasive tool 3A.

[0133] Here, it is considered that since the Young's modulus of the rigid grinding stone 2B is large, the grinding stone 2B itself does not bend. In addition, it is considered that when the abrasive is the grinding stone 2B, there is no change in the cutting ability due to the dimension in the axial direction X. However, in the grinding tool 1, it is necessary to bring the front end surface of the grinding stone 2B into contact with the machining target surface S of the workpiece W. Therefore, the grinding stone 2B is held by the abrasive holding seat 11 in a cantilever state. Similarly, the grinding stone 2B is held by the abrasive tool holding seat 4 in a cantilever state via the abrasive holding seat 11. As a result, bending of the concentrated load at the front end of the cantilever beam occurs in the grinding stone 2B.

[0134] The amount of bending caused by the concentrated load at the front end of the cantilever beam is proportional to the cube of the length dimension in the axial direction X. Therefore, the longer the dimension in the axial direction X, the greater the amount of bending, and the cutting ability is likely to decrease. On the other hand, if the wear amount increases and the length dimension of the abrasive in the axial direction becomes shorter, the bending amount becomes smaller, so the rigidity increases and the cutting ability improves. In addition, when the abrasive is the grinding stone 2B, the load output from the load detector 23 is the reaction force when the front end surface of the grinding stone 2B is vertically pressed against the machining target surface S of the workpiece W during grinding. This reaction force is proportional to the contact area between the front end surface of the grinding stone 2B and the machining target surface S of the workpiece W. Therefore, if the contact area is small, the load is small, and if the contact area is large, the load is large. Thus, even when the abrasive is the rigid grinding stone 2B, the present invention can be applied in the same manner as in the case of the bundle of the linear abrasives 2.

[0135] In addition, compared with the abrasive having elasticity, there is a problem that the longer the length dimension in the axial direction X of the rigid grinding stone 2B, the easier it is to generate cracks. Regarding this problem, based on the length dimension in the axial direction X of the grinding stone 2B, if the load threshold range is changed, the generation of cracks on the grinding stone 2B can be suppressed.

Claims

1. A control method for a grinding tool holder, the grinding tool holder including a mechanical mounting portion; a mounting portion on which a grinding tool is mounted; a moving mechanism having a drive source and moving the mounting portion in the axial direction of the mechanical mounting portion; and a load detector for detecting a load applied to the grinding tool mounted on the mounting portion, the control method for the grinding tool holder being characterized in that, mount a grinding tool having abrasive on the mounting portion, connect the mechanical mounting portion to the spindle of a machine tool and operate the machine tool, during the machine tool moving the grinding tool holder along a pre-specified machining path, monitor the output from the load detector, and calculate the change amount of the load per unit time, judge whether the change of the load is caused by the wear of the abrasive based on the change amount, and drive the drive source based on the load and the change amount to move the mounting portion, thereby performing a protrusion control action for advancing and retracting the grinding tool. When the load is outside a pre-set load threshold range and the change amount is less than a pre-set change amount threshold, the protrusion control action can be performed.

2. The control method for a grinding tool holder according to claim 1, characterized in that, stop the protrusion control action when the load is zero, and maintain a state where the protrusion control action is not performed until the change amount is lower than a pre-set set change amount.

3. The control method for a grinding tool holder according to claim 2, characterized in that, when the load is outside the load threshold range and the change amount is within a specified change amount threshold range, set it to a state where the protrusion control action is not performed, and when the load is outside the load threshold range and the change amount is outside the change amount threshold range, the protrusion control action can be performed.

4. The control method for a grinding tool holder according to claim 1, characterized in that, if the load is outside the load threshold range and the change amount is above the change amount threshold, while setting it to a state where the protrusion control action is not performed, count the duration for which the state where the load is outside the load threshold range and the change amount is above the change amount threshold lasts, maintain the state where the protrusion control action is not performed until the duration reaches a pre-specified set time, and when the duration exceeds the set time, restart the protrusion control action.

5. The control method for a grinding tool holder according to claim 1, characterized in that, pre-hold a plurality of the load threshold ranges corresponding to the length dimension of the abrasive in the axial direction as the load threshold range, before moving the grinding tool holder by the machine tool, configure the mounting portion on which the grinding tool is mounted at an initial position capable of advancing and retracting in the axial direction. Each time the mounting part is moved during the protrusion control operation, the amount of movement of the mounting part moving from the initial position toward the side opposite to the mechanical mounting part is calculated based on the driving amount of the drive source and the moving direction of the mounting part, and one load threshold range is selected from the plurality of load threshold ranges based on the amount of movement.

6. The control method of the grinding tool holder according to claim 1, characterized in that, A first load threshold range and a second load threshold range different from the first load threshold range are pre-held as the load threshold ranges, The first load threshold range is set as the load threshold range, the number of times when the load becomes zero is counted, and when the number reaches a specified set number, the load threshold range is set as the second load threshold range.

7. The control method of the grinding tool holder according to claim 1, characterized in that, A storage part is included in advance. The grinding tool holder is moved along a pre-specified learning path by the machine tool, the output from the load detector is monitored, and the change amount of the load per unit time is calculated in sequence. The load threshold range is set based on the load, and the change amount threshold is set based on the change amount and they are stored and held in the storage part, When the machine tool moves the grinding tool holder along the processing path, the load threshold range and the change amount threshold are obtained by referring to the storage part.

8. The control method of the grinding tool holder according to claim 1, characterized in that, The grinding tool includes: an abrasive, the longitudinal direction of which faces the axial direction; and an abrasive holder for holding one end of the abrasive in the axial direction, The abrasive holder is mounted on the mounting part.

9. A grinding tool holder, characterized in that, comprising: A mechanical mounting part; A mounting part on which a grinding tool having an abrasive is mounted; A moving mechanism having a drive source and moving the mounting part along the axial direction of the mechanical mounting part; A load detector for detecting the load applied to the grinding tool mounted on the mounting part; and A control part that monitors the output from the load detector, calculates the change amount of the load per unit time, determines whether the change of the load is caused by the wear of the abrasive based on the change amount, and drives the drive source based on the load and the change amount to move the mounting part, thereby performing a protrusion control operation for advancing and retracting the grinding tool, The control part can perform the protrusion control operation when the load is outside a pre-set load threshold range and the change amount is less than a pre-set change amount threshold.

10. The grinding tool holder according to claim 9, characterized in that, The control part stops the protrusion control operation when the load is zero, and maintains the state of not performing the protrusion control operation until the change amount is lower than a pre-set set change amount.

11. The abrasive holding base according to claim 10, wherein, when the load is outside the load threshold range and the change amount is within a specified change amount threshold range, the control unit is set to a state where the protruding control action is not performed; when the load is outside the load threshold range and the change amount is outside the change amount threshold range, the protruding control action can be performed.

12. The abrasive holding base according to claim 9, wherein, it has a timer, in the control unit, when the load is outside the load threshold range and the change amount is equal to or more than the change amount threshold, while setting it to a state where the protruding control action is not performed, the timer is driven to count the duration during which the load is outside the load threshold range and the change amount is equal to or more than the change amount threshold until the duration reaches a preset set time, maintaining the state where the protruding control action is not performed, and when the duration exceeds the set time, the protruding control action is restarted.

13. The abrasive holding base according to claim 9, wherein, it has a load threshold storage unit that stores and holds a plurality of load threshold ranges corresponding to the length dimension of the abrasive in the axial direction as the load threshold range, the control unit includes: an initial action control unit for arranging the mounting part at an initial position capable of advancing and retreating in the axial direction; and a load threshold range resetting unit that, each time the mounting part is moved during the protruding control action, calculates the moving amount of the mounting part moving from the initial position toward the side opposite to the mechanical mounting part based on the driving amount of the driving source and the moving direction of the mounting part, and selects one load threshold range from the plurality of load threshold ranges based on the moving amount with reference to the load threshold storage unit.

14. The abrasive holding base according to claim 9, wherein, it has a load threshold storage unit that stores and holds a first load threshold range and a second load threshold range different from the first load threshold range as the load threshold range, the control unit includes: a counting unit that counts the number of times when the load becomes zero; and a load threshold range resetting unit that sets the first load threshold range as the load threshold range until the number of times reaches a specified set number of times, and sets the load threshold range as the second load threshold range when the number of times reaches the set number of times.

15. The abrasive holding base according to claim 9, wherein, it has a storage unit, The control unit includes: an operation mode switching unit that switches the operation mode of the control unit between a normal operation mode and a learning operation mode; and a learning data setting unit that, in the learning operation mode, monitors the output from the load detector, sequentially calculates the change amount of the load per unit time, sets the load threshold range based on the load, and sets the change amount threshold based on the change amount and stores and holds them in the storage unit. In the normal operation mode, the control unit refers to the storage unit and obtains the load threshold range and the change amount threshold from the storage unit.

16. A grinding tool characterized in that it includes: a grinding tool holder as described in claim 9; and a grinding tool that is detachably mounted on the mounting portion of the grinding tool holder, the grinding tool includes: an abrasive, the longitudinal direction of which faces the axial direction; and an abrasive holder that holds one end of the abrasive in the axial direction, the abrasive holder is mounted on the mounting portion.

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