JP2012000733A - Workpiece cutting method and wire saw - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrain sudden displacement of a tension applying member when switching the wire driving direction.SOLUTION: A workpiece cutting method repeatedly performs an advance driving cutting step of winding on a second reel 9B by reducing tension of this wire W to winding side tension lower than this tension while increasing the tension of the wire W to delivery side tension while delivering the wire W from a first reel 9A and a retreat driving cutting step of winding on the first reel 9A by reducing the tension of this wire W up to the winding side tension while increasing the tension of the wire W up to the delivery side tension while delivering the wire from the second reel 9B. In its case, on the wire delivery side, the first reel is driven at a first rotating speed at which its peripheral velocity becomes lower than peripheral velocity of a guide roller 24, and on the winding side, the second reel is driven at a second rotating speed at which its peripheral velocity becomes lower than peripheral velocity of the first reel driven at the first rotating speed.

Description

  The present invention relates to a workpiece cutting method and a wire saw for cutting a semiconductor ingot or the like using a wire saw.

  For example, a wire saw is known as means for cutting out a large number of thin pieces (for example, wafers) from a workpiece such as a semiconductor ingot at a time. In this wire saw, the wire for cutting fed from the reel of the wire feeding / winding device is wound around a plurality of guide rollers and then wound on the reel of another wire feeding / winding device. The wire is moved in the forward direction (direction from the one-side wire feeding / winding device toward the other-side wire feeding / winding device) and the backward direction (the other-side wire feeding / winding) by switching the driving state of each wire feeding / winding device. The direction of movement is alternately switched between the take-up device and the one-side wire take-up device. Then, both the reels on the feeding side and the winding side and the respective guide rollers are rotationally driven at the same peripheral speed, so that the cutting wire is driven at a high speed in the longitudinal direction, and between the specific guide rollers. When a workpiece made of the semiconductor ingot or the like is cut and fed in a direction substantially orthogonal to a plurality of wires arranged in parallel, a large number of thin pieces are cut out simultaneously from the workpiece.

  In the wire saw, it is necessary to adjust the wire tension to an appropriate value in order to ensure stable processing accuracy. Therefore, Patent Document 1 below discloses a device provided with a tension adjusting device for adjusting the wire tension in each region from each wire feeding and winding device to the guide roller. Each tension adjusting device includes a load cell that detects the tension of the wire and a tension arm that is swingably supported within a predetermined range and is pressed against the wire to change the tension, and is detected by the load cell. The pressing force of the tension arm to the wire is adjusted so as to keep the wire tension constant. The wire saw also includes a speed adjusting device for adjusting the rotational speed of each reel. The speed adjusting device includes a position detector that detects the position of each tension arm, and is detected by the position detector so as to place the tension arm at an intermediate position within the moving range while maintaining the wire tension. The drive speed of each reel is finely adjusted based on the position of the tension arm. In this way, by keeping each tension arm at an intermediate position, it is possible to secure the allowance for movement and always allow proper tension adjustment.

Japanese Patent Laid-Open No. 9-94755

  In the wire saw, it is necessary to apply a certain tension or higher to the wire in order to stably cut the workpiece. On the other hand, there is a situation that the higher the tension, the greater the load on the reel. That is, the higher the tension of the wire wound by the reel, the more easily the wire will bite into the outer peripheral surface of the reel, and the risk of shortening the life of the reel increases.

  As a means for solving such inconvenience, it is conceivable to use the tension adjusting device described above and to lower the wire tension at the time of winding than the wire tension at the time of feeding. However, when operating a reciprocating drive type wire saw that reciprocates the wire, unnecessary swinging (displacement) occurs in the tension arm when the wire driving direction is switched due to the difference in wire tension.

  That is, on the wire feeding side, the wire is stretched by adjusting the tension of the wire fed from the reel to a tension higher than the tension at the time of winding. As a result, the wire length in the section from the reel on the feeding side to the guide roller is increased and the detected tension of the wire is lowered. As a result, the tension arm swings slightly from the intermediate position in the direction of pulling the wire. On the other hand, on the wire take-up side, the wire tension decreases, and the wire stretched by the tension applied during feeding and the pressing of the work contracts, so that the wire length in the section from the guide roller to the reel on the take-up side is reduced. As a result of shortening and increasing the detected tension of the wire, the tension arm is displaced slightly from the intermediate position in the direction of being pulled by the wire. The tension arm swings every time the wire is moved forward / backward.

  Such swinging of the tension arm is temporary, and then the tension arm is returned to the intermediate position by adjusting the rotation speed of the reel by the speed adjusting device. If such tension arm swinging occurs every time, it is desirable that it can be suppressed because the running stability of the wire may be impaired.

  In view of these circumstances, the present invention relates to a reciprocating drive type wire saw, and changes the wire driving direction while adjusting the wire tension so that the wire tension on the wire winding side is lower than the wire tension on the wire feeding side. It is an object of the present invention to provide a technique for suppressing unnecessary displacement of a tension applying member such as a tension arm that sometimes occurs.

  In order to solve the above problems, the present invention uses a wire saw in which a wire for cutting fed from a first reel is wound around a plurality of guide rollers and wound around a second reel, In a method of cutting and feeding a plurality of wires arranged between them by cutting and feeding by moving the workpiece relative to these wires while driving in the axial direction at a predetermined speed by rotational driving of the guide roller, The wire is fed out from the first reel, and the wire is wound up by the second reel, and the detected tension is predetermined while detecting the tension of the wire fed out from the first reel by the first tension detecting means. The first tension applying member is pressed against the wire so as to approach the feeding side tension of the wire to adjust the tension of the wire, and is wound around the second reel. The tension of the wire is adjusted by pressing the second tension applying member against the wire so that the detected tension approaches the winding side tension lower than the feeding side tension while detecting the tension of the wire to be detected by the second tension detecting means. However, the forward drive cutting process that advances the cutting of the workpiece, the wire wound by the second reel is reversed from the second reel, and the wire is wound by the first reel, While detecting the tension of the wire fed from the second reel by the second tension detecting means, the second tension applying member is pressed against the wire so that the detected tension approaches the feeding side tension, thereby adjusting the tension of the wire. In addition, the detected tension approaches the winding side tension while detecting the tension of the wire wound around the first reel by the first tension detecting means. While the first tension applying member is pressed against the wire and the tension of the wire is adjusted, the reverse drive cutting step of cutting the workpiece is repeated, and in the forward drive cutting step, the peripheral speed of the first reel is While driving at a first rotational speed that is lower than the peripheral speed of the guide roller, the wire is fed from the first reel, and the second reel is driven at the first rotational speed. The wire is wound around the second reel while being driven at a second rotational speed that is lower than the peripheral speed of the reel, and the second reel is driven at the first rotational speed in the reverse drive cutting step. The wire is fed out from the second reel while the first reel is driven at the second rotational speed, and the wire is wound up by the first reel.

  According to this method, the wire fed out from the reel is adjusted to a predetermined feeding side tension on the wire feeding side while the wire is advanced and retracted repeatedly, while the wire wound up on the reel is adjusted on the wire winding side. Since the tension is adjusted to a predetermined winding side tension lower than the feeding side tension, only the wire tension on the winding side is reduced while securing the wire tension required for stable cutting, and the strength burden of the reel on the winding side is reduced. Can be reduced. Moreover, on the wire feeding side, the reel is fed at a first rotational speed at which the circumferential speed is lower than the circumferential speed of the guide roller, and the wire is fed from the reel. Since the wire is wound by the reel while being driven at the second rotational speed that is lower than the peripheral speed of the reel driven at the first rotational speed, the wire feeding side and the wire winding side as described above are used. While making a difference in wire tension, it is possible to suppress unnecessary displacement of the tension applying member that occurs at the time of wire advance / reverse switching. That is, for example, when the cutting process shifts from the forward drive cutting process to the backward drive cutting process, on the wire feeding side, the wire tension (winding side tension) is increased to the feeding side tension while feeding the wire from the second reel. The wire will stretch. However, by driving the wire from the second reel while driving the second reel at the first rotational speed at which the peripheral speed is lower than the peripheral speed of the guide roller as in the above method, The change in the wire length in the section from the second reel to the guide roller due to the elongation of the wire is suppressed, whereby the rapid displacement of the second tension applying member is suppressed. On the other hand, on the wire winding side, since the wire tension is lowered to the winding side tension, the wire stretched due to the tension application by the second tension applying member and the pressing of the work is caused to be significantly contracted. However, as in the above method, the wire is connected to the first reel while driving the first reel at the second rotational speed at which the peripheral speed is lower than the peripheral speed of the second reel driven at the first rotational speed. Thus, the change in wire length due to the contraction of the wire in the section from the guide roller to the first reel is suppressed, whereby the rapid displacement of the first tension applying member is suppressed.

  Note that the optimum rotation speed (first and second rotation speeds) of each reel changes over time due to various factors such as wire deterioration and the operating state of the reel drive mechanism. Accordingly, in the above method, the position of the first tension applying member is detected by the first position detecting means, the position of the second tension applying member is detected by the second position detecting means, and each of the tension applying members is detected. The workpiece is cut while adjusting the rotational speed of each reel so that the position approaches each predetermined reference position, and the first tension applying member is positioned substantially at the reference position in a specific cutting step. The rotation speed of the first reel is detected by the first speed detection means, and the rotation speed of the second reel is detected by the second speed detection means when the second tension applying member is substantially at the reference position. Then, the first and second rotation speeds are set to the detection speed so that the rotation speed of each reel in the cutting process performed after the specific cutting process approaches the detection speed. It is preferable to correct based.

  In this way, the rotational speeds (first and second rotational speeds) when driving the first and second reels are based on the actual rotational speeds when the respective tension applying members are located substantially at the reference position. According to the correction method, it is possible to eliminate the rotational speed error caused by the deterioration of the wire, the operating state of the reel, etc., and the reliability of the rotational speed when driving each reel is improved. Therefore, the displacement of each tension applying member at the time of forward / backward switching of the wire can be more reliably suppressed.

  The present invention also provides a wire saw for simultaneously cutting a workpiece at a plurality of locations using a cutting wire, wherein the rotation center axes are arranged in parallel to each other, and the wire is wound around the wire saw. A plurality of guide rollers, guide roller driving means for driving the guide rollers, first and second reels for respectively feeding and winding the wire around the guide rollers, and driving the reels, respectively. A plurality of wires stretched between the first and second reel driving means and a specific guide roller of the guide rollers and the workpiece are moved relative to each other to cut and feed the workpiece to the wire. Cutting and feeding means for cutting the workpiece, and feeding out the wire from the first reel, and winding the wire with the second reel, A forward drive cutting process for advancing cutting of the workpiece, and a reverse drive cutting process for feeding the wire from the second reel and advancing the cutting of the workpiece while winding the wire with the first reel. Wire driving control means for repeatedly performing the guide roller driving means and the first and second reel driving means so that the wire wound around the guide roller is driven at a predetermined speed suitable for workpiece cutting; A first tension detecting means for detecting a wire tension in a section between the first reel and each of the guide rollers, a first tension applying member pressed against the wire in the section, and the first tension applying member. First tension operating means for changing the tension of the wire by changing the position of the first tension applying member, including first position operating means for changing the position. , Second tension detecting means for detecting wire tension in a section between the second reel and each guide roller, a second tension applying member pressed against the wire in the section, and the second tension applying member A second position operating means for changing the position, a second tension operating means for changing the tension of the wire by changing the position of the second tension applying member, and the first and second tension detecting means. Based on the detected tension, the tension of the wire fed from one of the first and second reels is adjusted to a predetermined feeding tension, and the tension of the wire wound by the reel on the other side is adjusted. Tension control means for actuating each tension operating means to adjust to a predetermined winding side tension lower than the feeding side tension. The first reel is driven at a first rotational speed at which the peripheral speed is lower than the peripheral speed of the guide roller, so that the wire is fed from the first reel, and the second reel is rotated at the peripheral speed. Is driven at a second rotational speed that is lower than the peripheral speed of the first reel driven at the first rotational speed, so that the wire is wound by the second reel, and the reverse drive cutting step On the other hand, by driving the second reel at the first rotational speed, the wire is fed out from the second reel, and the first reel is driven at the second rotational speed. The wire is wound up by the first reel.

  Also in this wire saw, the tension control means adjusts the wire fed from the reel to the feeding side tension on the wire feeding side, while the wire wound on the reel is lower than the feeding side tension on the wire winding side. Since the tension is adjusted to the winding side tension, it is possible to reduce only the wire tension on the winding side while ensuring the wire tension required for stable cutting, and to reduce the strength burden of the wire feeding and winding device on the winding side. it can. Further, the wire drive control means causes the reel to be fed out from the reel by driving the reel at a first rotational speed whose peripheral speed is lower than the peripheral speed of the guide roller on the wire payout side, On the wire winding side, the reel is driven at a second rotational speed whose peripheral speed is lower than the peripheral speed of the reel driven at the first rotational speed, thereby winding the wire by the reel. Therefore, as described above, it is possible to suppress unnecessary displacement of the tension applying member that occurs at the time of wire advance / reverse switching while providing a difference in wire tension between the wire feeding side and the wire winding side.

  In this wire saw, first and second position detecting means for detecting the positions of the first and second tension applying members, respectively, and first and second for detecting the rotation speeds of the first and second reels, respectively. Second speed detection means, and the wire drive control means includes a position of the first tension applying member detected by the first position detection means and a second tension detected by the second position detection means. The rotation speed of each reel is controlled so that the position of the applying member approaches the reference position, and the first tension applying member is a speed detected by the first speed detecting means in a specific cutting step. On the basis of the detection speed when the second tension detecting member is substantially at the reference position and the detection speed when the second tension applying member is substantially at the reference position. The first of the reel so that the rotational speed of each reel approaches the detection rate in the cutting step performed after the cutting step of, it is preferred that corrects the second rotational speed.

  According to this configuration, the reliability of the first and second drive speeds when driving the reels by the wire drive control device is improved, thereby eliminating the need for each tension applying member at the time of forward / backward switching of the wires. It becomes possible to suppress a certain displacement more reliably.

  As described above, according to the present invention, while the wire is repeatedly advanced and retracted, the wire tension on the winding side is reduced by reducing only the wire tension on the winding side while ensuring the wire tension required for stable cutting. Strength burden can be reduced. In addition, it is possible to suppress unnecessary displacement of the tension applying member that occurs at the time of wire advance / reverse switching while providing a difference in wire tension between the wire feeding side and the wire winding side. The running stability of the wire can be improved.

1 is an overall configuration diagram of a wire saw according to an embodiment of the present invention. It is a front view of the tension operation device provided in the wire saw. It is a top view of the tension operation device. It is a block diagram which shows the function structure of the controller with which the said wire saw is equipped. It is a graph which shows the time change of the rotational speed (circumferential speed) of the guide roller in the said wire saw, and the rotational speed (circumferential speed) of a reel. It is a block diagram (modification) which shows the function structure of the controller with which the said wire saw is equipped. It is a flowchart which shows the process sequence which correct | amends the target speed of a reel (update).

  A preferred embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 shows the overall configuration of a wire saw according to the present invention. The wire saw shown in this figure includes a pair of wire feeding and winding devices 10A and 10B (referred to as the first wire feeding and winding device 10A and the second wire feeding and winding device 10B as appropriate), and four guide rollers disposed therebetween. 24A, 24B, 26A, and 26B. Among these guide rollers, the guide rollers 24A and 24B are arranged at the same height position, and the guide rollers 26A and 26B are arranged at positions below the guide rollers 24A and 24B, respectively.

  Fixed pulleys 12A, 14A, 16A, a first tension operating device are arranged between the first wire pay-out winding device 10A and the guide rollers 24A, 24B, 26A, 26B in order from the side closer to the wire pay-out winding device 10A. 18A (corresponding to first tension operating means) and a fixed pulley 22A are provided, and the first tension operating device 18A includes a tension arm 19A. Similarly, the fixed pulleys 12B, 14B, 16B, and the second between the second wire feeding and winding device 10B and the guide rollers 24A, 24B, 26A, and 26B, in order from the side closer to the wire feeding and winding device 10B. A tension operating device 18B (corresponding to the second tension operating means) and a fixed pulley 22B are provided, and the second tension operating device 18B includes a tension arm 19B.

  Each of the wire take-up devices 10A and 10B includes reels 9A and 9B (corresponding to a first reel and a second reel) around which a wire W for cutting is wound, and reel drive motors 11A and 11B (first reels) that rotate the reels 9A and 9B. 1 reel driving means and second reel driving means). Then, the wire W fed from the reel 9A of the first wire feeding / winding device 10A is hung in the order of the fixed pulleys 12A, 14A, 16A, the tension arm 19A of the first tension operating device 18A, and the fixed pulley 22A. After being wound many times outside the guide rollers 24A, 24B, 26B, 26A, the fixed pulley 22B, the tension arm 19B of the second tension operating device 18B, and the fixed pulleys 16B, 14B, 12B are hung in this order, and the second wire The wire W is wound around the reel 9B of the feeding / winding device 10B, and an appropriate tension is applied to the wire W by both the tension operating devices 18A and 18B. Further, a roller driving motor 25 (corresponding to guide roller driving means) for rotating the rotation shafts is connected to the rotation shafts of the respective guide rollers 24A, 24B, 26B, and 26A (in FIG. 1, guide rollers). Only 26A is shown).

  Then, the rotation drive direction of the reels 9A and 9B by the reel drive motors 11A and 11B and the rotation drive direction of the guide roller 26A by the roller drive motor 25 are switched between forward and reverse, whereby the wire W is fed out from the reel 9A and reels. The state can be switched between a state where the wire W is wound up (a state where the wire W is driven forward) and a state where the wire W is unwound from the reel 9B and wound around the reel 9A (a state where the wire W is driven backward). Yes.

  That is, in the wire saw according to this embodiment, a large number of wires W are stretched between the guide rollers 24A and 24B among the four guide rollers, and reciprocate in the longitudinal direction (axial direction). Driven. However, in the present invention, the number of the guide rollers can be freely set in a range of two or more regardless of the specific number.

  Above the wire W stretched between the guide rollers 24A and 24B, a workpiece feeding device 30 (corresponding to a cutting feeding means) for moving a cylindrical workpiece (for example, a semiconductor ingot) 28 is provided. The workpiece feeding device 30 includes a workpiece holding unit 32 and a workpiece feeding motor 34. The workpiece holding unit 32 holds the workpiece 28 in a direction in which a target crystal orientation can be obtained based on the crystal axis. The workpiece feeding motor 34 is combined with a ball screw (not shown), 32 and the workpiece 28 are moved up and down integrally (that is, cut and fed).

  Above the wire W stretched between the guide rollers 24A and 24B, slurry supply devices 36A and 36B are provided at positions on the left and right sides of the work 28. These slurry supply devices 36 </ b> A and 36 </ b> B simultaneously supply a processing liquid (slurry) in which abrasive grains are mixed to each wire W that is driven at high speed, and attach this to the surface of the wire W.

  Therefore, in this wire saw, a large number of wires W stretched between the guide rollers 24A and 24B are simultaneously driven in the longitudinal direction at a high speed, and the machining fluid is supplied to the wires W from the slurry supply devices 36A and 36B. The workpiece 28 is cut and fed downward with respect to these wires W, whereby a large number of wafers are simultaneously cut out from the workpiece 28.

  Next, the configuration of the tension operation devices 18A and 18B will be described with reference to FIGS. In addition, since the structure of both tension | tensile_strength operating devices 18A and 18B is equivalent, it demonstrates taking the 1st tension | tensile_strength operating device 18A as an example here.

  The first tension operating device 18A includes the tension arm 19A (corresponding to the first tension applying member) as described above. The tension arm 19A includes a pulley 20 (referred to as a movable pulley 20) and a lever 21 that supports the pulley 20, and a wire W is stretched around the movable pulley 20. The movable pulley 20 is disposed between the fixed pulleys 16A and 22A, and the wire length is changed by the vertical movement of the movable pulley 20 accompanying the swing of the tension arm 19A (specifically, the movable pulley 20 is lowered). Then, the pulleys 16A, 20, and 22A are arranged so that the wire length increases and the wire length decreases when the movable pulley 21A rises.

  A tension detector 40 (corresponding to the first tension detecting means) is attached to the support member 38 of the fixed pulley 22A. The tension detector 40 detects the load applied to the support member 38 and, consequently, the tension of the wire W. As the tension detector 40, a load cell or a combination of a differential transformer and a spring can be used.

  The movable pulley 20 is attached to the tip of the lever 21 so as to be rotatable about a rotation shaft 42 orthogonal to the axial direction of the wire W. A rotation center shaft 46 is fixed to the base end of the lever 21, and the rotation center shaft 46 is connected to a swing cylinder 50 (corresponding to a first position operation means) fixed to a fixed side plate 48. Yes. The swing cylinder 50 rotates the lever 21 and the movable pulley 20 (that is, the tension arm 19A) around the rotation center axis 46 and presses the movable pulley 20 against the wire W. The tension is changed by increasing or decreasing the pressing force.

  An encoder 52 (corresponding to first position detecting means) is connected to the rotation center shaft 46. The encoder 52 detects the rotational angle position of the tension arm 19A.

  This wire saw is provided with a controller 60 as shown in FIG. The controller 60 has functions as a wire drive control unit and a tension control unit, and includes a tension adjustment unit 62, a speed adjustment unit 64, and a target speed setting unit 66.

  The tension adjusting means 62 is a pneumatic servo circuit 54 for driving the swing cylinder 50 so as to keep the wire tension detected by the tension detector 40 on each of the wire feeding side and the wire winding side at a preset tension T. An electric signal is output to adjust the driving force of the oscillating cylinder 50 and the wire tension. Specifically, for example, when the detected tension on the first wire feeding / winding device 10A side is higher than the tension T, the driving force of the swing cylinder 50 is reduced and the tension arm connected to the swing cylinder 50 is reduced. The force with which the movable pulley 20 is pressed against the wire W is lowered by moving 19A upward (by turning clockwise in FIG. 2). Conversely, when the detected tension is lower than the tension T, the driving force of the swing cylinder 50 is increased to move the tension arm 19A downward (rotate counterclockwise in FIG. 2). The movable pulley 20 increases the force with which the wire W is pressed against the wire W.

  In this wire saw, the tension adjusting means 62 keeps the wire tension at the feeding side tension T1 (25N), which is a tension necessary for cutting the workpiece 28, on the wire feeding side, and on the winding side from the feeding side tension T1. The driving force of the swing cylinder 50 is adjusted so as to maintain a predetermined winding-side tension T2 (5N) suitable for winding the reels 9A and 9B. As a result, in this wire saw, the wire tension necessary for good cutting of the work 28 is ensured between the guide rollers 24A and 24B, while the reels 9A and 9B are used for the reels 9A and 9B on the winding side. The biting of the wire W is alleviated.

  The speed adjusting unit 64 advances the cutting of the workpiece 28 while driving the wire W forward (forward drive cutting step), and advances the cutting of the workpiece 28 while driving the wire W backward (reverse driving cutting step). Is adjusted so that the reel drive motors 11A and 11B are driven in a repetitive manner, and the reel drive in each cutting step is performed based on the target speed V of the reels 9A and 9B input by the target speed setting means 66. The driving speeds of the motors 11A and 11B, in other words, the wire feeding speed and the wire winding speed are adjusted.

  The speed adjusting means 64 is configured so that the rotation angle positions of the tension arms 19A and 19B detected by the encoder 52 are set in advance as reference positions (here, the tension arms 19A and 19B are horizontal as shown by the solid line in FIG. 2). And a function of finely adjusting the rotational speeds of the reels 9A and 9B by outputting control signals to the reel drive motors 11A and 11B, respectively. For example, when it is detected that the tension arm 19A on the feeding side is at a position below the reference position in a state in which the wire W is fed from the reel 9A and wound forward on the reel 9B. In order to move the tension arm 19A upward (clockwise), the rotation speed of the reel 9A on the wire feeding side is decreased, and conversely, it is detected that the tension arm 19A is located above the reference position. In this case, the rotational speed of the reel 9A on the wire feeding side is increased in order to move the tension arm 19A downward (counterclockwise). On the other hand, when it is detected that the tension arm 19B on the wire winding side is at a position below the reference position, the wire winding side tension arm 19B is moved upward (counterclockwise). When the rotational speed of the reel 9B is increased and it is detected that the tension arm 19B is located above the reference position, the wire winding is performed to move the tension arm 19B downward (clockwise). The rotational speed of the take-up reel 9B is decreased.

  The target speed setting means 66 sets the target speed V (that is, the rotational speed V) of the reels 9A and 9B as described above and inputs it to the speed adjusting means 64. The speed adjusting means 64 is the target speed. Based on V, the drive speeds of the reel drive motors 11A and 11B are adjusted.

  The target speed setting means 66 changes the target speed V depending on whether the reels 9A and 9B are on the wire feeding side or the wire winding side. Specifically, when the wire W is driven forward (in a state where the wire W is fed from the reel 9A and wound on the reel 9B), the target speed V of the reel 9A on the wire feeding side is set to the first target speed. While setting to V1, the target speed V of the reel 9B on the wire winding side is set to a second target speed V2 that is slower than the first target speed V1. Conversely, when the wire W is driven backward (in a state where the wire W is fed from the reel 9B and wound on the reel 9A), the target speed V of the reel 9B on the wire feeding side is set to the first target speed V1. Then, the target speed of the reel 9A on the wire winding side is set to the second target speed V2.

These target speeds V1 and V2 are set based on the driving speed (traveling speed) of the wire W necessary for cutting the workpiece 28, that is, the rotational speed of the guide roller 24A and the like. This point will be described with reference to FIG. FIG. 5 shows the relationship between the rotational speed V _W (peripheral speed) of the wire saw guide roller 24A and the like and the rotational speed V (circumferential speed) of the reel 9A on the first wire take-up device 10A side. As shown in this figure, when the wire W is driven forward, the target speed setting means 66 lowers the target speed V of the reel 9A on the wire feeding side by a fixed speed from the peripheral speed of the guide roller 24 and the like. Is set to the first target speed V1. Further, when the wire W is driven backward, the target speed V of the reel 9A on the wire winding side is set to the second target whose peripheral speed is lower than the peripheral speed of the reel 9A driven at the first target speed V1. Set to speed V2. Although the target speed (rotational speed) of the reel 9A on one side has been described here, the same applies to the reel 9B on the other side except that the driving direction of the wire W is reversed.

  Next, the effect of this wire saw will be described.

<Forward drive cutting process>
The reel 9A of the first wire feeding / winding device 10A is rotationally driven in the feeding direction, and the reel 9B of the second wire feeding / winding device 10B is driven in the winding direction, whereby the wire W is fed from the reel 9A. And wound on the reel 9B. Then, the workpiece 28 is cut and fed to the wire W (wire group) at a predetermined driving speed of the wire W, so that the workpiece 28 is cut.

  At this time, the tension of the swing cylinder 50 is adjusted by the tension adjusting means 62 based on the wire tension detected by the tension detector 40, so that the tension of the wire W on the wire feeding / winding device 10A side becomes the feeding side. The tension T1 (= 25N) and the tension of the wire W of the wire feeding and winding device 10B are adjusted to the winding side tension T2 (= 5N), respectively.

  On the other hand, after starting to feed out the wire from the reel 9A, the detection signal of the encoder 52 (that is, the position detection signal of the tension arms 19A and 19B) provided in the tension operation devices 18A and 18B is taken into the speed adjusting means 64. The speed adjusting means 64 compares the detection positions of the tension arms 19A and 19B with a preset reference position, and when the former is higher than the latter, the tension arms 19A and 19B are moved downward. Finely adjust the rotation speed of the reels 9A and 9B. On the contrary, when the former is lower than the latter, the rotational speeds of the reels 9A and 9B are finely adjusted so that the tension arms 19A and 19B move upward. As a result, in a steady state, the tension arms 19A and 19B are held substantially at the reference position, and a margin for movement of the tension arms 19A and 19B is ensured appropriately.

  With the above control, the wire tension on the first wire feeding device 10A side is kept at a predetermined feeding side tension T1, and thereby, the wire tension necessary for good cutting of the workpiece 28 is secured between the guide rollers 24A and 24B. The On the other hand, since the wire tension on the wire winding device 10B side is suppressed to a predetermined winding side tension T2 lower than the feeding side tension T1, the biting of the wire W on the reel 9B of the wire winding device 10B is alleviated. The strength burden on the reel 9B is reduced.

  When the forward drive cutting process reaches a preset wire length, the drive of the wire W is gradually decelerated. Then, when the speed becomes zero, the direction of driving of the wire W is switched, and the process proceeds to the backward drive cutting process.

<Reverse drive cutting process>
In this step, the reel 9B of the second wire feeding / winding device 10B is rotationally driven in the feeding direction, and the reel 9A of the first wire feeding / winding device 10A is driven in the winding direction, so that the wire W becomes the reel. It is fed out from 9B and wound on the reel 9A.

  In this step, the tension adjusting means 62 causes the wire tension on the second wire feeding / winding device 10B side to be a predetermined feeding side tension T1 (= 25N), and the wire tension on the first wire feeding / winding device 10A side is set to a predetermined value. The winding side tension is adjusted to T2 (= 5N). As a result, as in the forward drive cutting step, the wire tension necessary for good cutting of the workpiece 28 is ensured between the guide rollers 24A and 24B, while the wire tension on the wire winding device 10A side is higher than the feeding side tension T1. Since the tension is suppressed to a low predetermined winding-side tension T2, the biting of the wire W on the reel 9A of the wire winding device 10A is alleviated, and the strength burden on the reel 9A is reduced.

  In this way, the cutting process is shifted from the forward drive cutting process to the backward drive cutting process, and the wire W wound around the reel 9B is fed out from the reel 9B and its tension is taken up by the winding side tension T2 (= 5N). ) To the feeding side tension T1 (= 25N), the wire W extends to increase the wire length in the section from the reel 9B to the guide roller 24A and the like, resulting in a decrease in wire tension. As a result, the tension arm 19B is moved from the reference position. It can be considered that it is displaced suddenly. Specifically, it is conceivable that the tension arm 19B is slightly displaced in the direction in which the wire W is pulled (downward). However, in this wire saw, as described above, the reel 9B on the wire feeding side is driven at the first rotational speed V1 at which the peripheral speed is lower than the peripheral speed of the guide roller 24A or the like. However, the change in the wire length in the section from the reel 9B to the guide roller 24A or the like is effectively suppressed. Therefore, the rapid displacement of the tension arm 19B as described above accompanying the transition from the forward drive cutting process to the reverse drive cutting process is suppressed.

  On the contrary, on the wire winding side (first wire feeding and winding device 10A side), the tension of the wire W is lowered to the winding side tension T2 (= 5N), whereby the tension is applied by the second tension manipulating device 18B. The wire stretched by the pressure of the work 28 contracts, and as a result, the wire length in the section from the guide roller 24A and the like to the reel 9A is shortened and the wire tension rises. As a result, the tension arm 19A is suddenly displaced from the reference position. Conceivable. Specifically, it is conceivable that the tension arm 19 </ b> A swings slightly in the direction in which the tension arm 19 </ b> A is pulled by the wire W (upper side). However, in this wire saw, as described above, the reel 9A on the wire winding side is driven at the second rotational speed V2 whose peripheral speed is lower than the peripheral speed of the reel 9B driven at the first rotational speed V1. Therefore, the change in the wire length in the section from the guide roller 24A or the like to the reel 9A is effectively suppressed while the wire W is contracted. In particular, as described above, the wire W from the guide roller 24A or the like to the reel 9A includes elongation due to the application of the tension by the second tension operation device 18B, as well as elongation due to the pressing of the workpiece 28. When driving at a speed (first rotation speed V1), there may be a case where the change in the wire length in the section cannot be suppressed, but as described above, the reel 9A is faster than the rotation speed V1 of the reel 9B on the feeding side. As a result of being driven at the lower second rotation speed V2, the change in the wire length in the section is more reliably suppressed. Therefore, the rapid displacement of the tension arm 19A as described above accompanying the transition from the forward drive cutting process to the reverse drive cutting process is effectively suppressed.

  Thus, when the backward driving cutting process reaches the preset wire length, the driving of the wire W is gradually decelerated, and when the speed becomes zero, the driving direction of the wire W is switched at this time, and the forward movement is performed. The process proceeds to the drive cutting process. At the time of transition from the backward drive cutting step to the forward cutting step, the drive speed of each reel 9A, 9B is adjusted based on the control of the reel drive motors 11A, 11B by the speed adjusting means 64 as described above. Abrupt displacement of the tension arms 19A and 19B accompanying the transition from the backward drive cutting process to the forward drive cutting process is suppressed, and thereby the running stability of the wire W is maintained.

  As described above, according to this wire saw, in the reciprocating drive type wire saw in which the wire W is repeatedly moved forward and backward, the wire on the winding side while securing the wire tension required for stable cutting by the tension operating devices 18A and 18B. By reducing only the tension, it is possible to reduce the strength burden on the reel on the winding side (reel 9B during forward drive and reel 9A during reverse drive). Moreover, while the reel on the wire feeding side is driven at the first rotation speed V1 whose peripheral speed is lower than the peripheral speed of the guide roller 24A or the like, the wire W is fed from the first reel while the reel on the wire winding side is driven. By winding the wire W with the reel while driving the reel at the second rotational speed V2 whose peripheral speed is lower than the peripheral speed of the reel driven at the first rotational speed V1, the tension as described above is obtained. Since the rapid displacement of the tension arms 19A and 19B at the time of wire advance / reverse switching due to the switching is suppressed, the running stability of the wire W can be ensured satisfactorily.

  The above-described embodiment is based on the premise that the driving speed of the reels 9A and 9B is adjusted using a fixed value as the target speed V of the reels 9A and 9B. In order to more reliably suppress the displacement of the tension arms 19A and 19B, the target speed V (rotational speed V) of each reel 9A and 9B is corrected (updated) based on the actual driving state of the reels 9A and 9B. It may be.

  FIG. 6 shows a functional configuration of the controller 60 in that case. As shown in the figure, the target speed setting means 66 receives a detection signal of the encoder 52 (position detection signals of the tension arms 19A and 19B) provided in the tension operating devices 18A and 18B, and a reel drive motor. Detection signals (revolution speed detection signals of the reel drive motors 11A and 11B) of an encoder 13 (corresponding to first and second speed detection means) incorporated in 11A and 11B are input.

  In this configuration, the target speed setting means 66 sets the target speed V according to the flowchart of FIG. In the following description, correction (updating) of the target speed V of the reel 9A of the first wire feeding / winding device 10A will be described.

  First, the target speed setting means 66 sets a target speed V (V1 or V2) stored in advance according to the driving direction of the wire W, and inputs the target speed V to the speed adjustment means 64 (step S1). ).

  When the drive of the wire W is started (YES in step S3), the target speed setting means 66 determines whether the tension arm 19A is substantially at the reference position based on the detection signal input from the encoder 52 of the tension operating device 18A. It is determined whether it is within a certain range including the reference position (for example, within plus or minus 1 °) (step S5). If YES is determined here, the target speed setting means 66 detects the rotational speed of the reel drive motor 11A based on the detection signal input from the encoder 13 of the reel drive motor 11A (step S7). Thereby, the rotation speed of the reel drive motor 11A is sampled until the current cutting process is completed.

  Next, the target speed setting means 66 determines whether or not the cutting process has been completed (step S9). If YES is determined here, it is further determined whether or not the wire W is driven forward (step S9). Step S11). That is, it is determined whether or not the rotation speed sampled in step S7 is the one during forward driving of the wire W. If YES is determined here, the target speed setting means 66 corrects the target speed V1 of the reel 9A at the time of wire feeding based on the detected speed of the reel drive motor 11A sampled in step S7 (step S13). Specifically, an average value of the detected speeds of the reel drive motor 11A is obtained, and the average value is converted into the rotation speed of the reel 9A at the time of wire feeding, and the converted value is updated as the target speed V1. Thus, at the time of forward driving of the next wire W (forward driving cutting step), the updated target speed V1 is input to the speed adjusting means 64 by the target speed setting means 66.

  If NO is determined in step S11, that is, if it is determined that the wire W is driven backward, the target speed setting unit 66 similarly sets the detected speed of the reel drive motor 11A sampled in step S7. Based on this, the target speed V2 of the reel 9A at the time of wire feeding is corrected (step S14). As a result, at the time of the backward drive of the next wire W (reverse drive cutting step), the updated target speed V2 is input to the speed adjusting means 64 by the target speed setting means 66.

  Next, the target speed setting means 66 determines whether or not the cutting of the workpiece 28 has been completed (step S15). If NO is determined here, the process returns to step S1, while if YES is determined. The processing according to this flowchart is terminated.

  Here, the correction (updating) of the target speed V of the reel 9A of the first wire feeding / winding device 10A by the target speed setting means 66 has been described, but the target speed of the reel 9B of the second wire feeding / winding device 10B has been described. The correction (update) of V is performed in the same manner.

  As described above, the reels are moved based on the actual rotation speed of the reels 9A and 9B (reel drive motors 11A and 11B) when the tension arms 19A and 19B are positioned at the reference position for each cycle of the forward and backward movements of the wire W. According to the configuration for correcting the target speed V (rotational speed V) of 9A and 9B, the reliability of the rotational speed when driving the reels 9A and 9B is improved, whereby the tension at the time of forward / backward switching of the wire is improved. It is possible to more reliably suppress the displacement of the arms 19A and 19B.

  In this example, the target speed V of the reels 9A and 9B is corrected for each cycle of the forward and backward movement of the wire W. However, the timing for correcting the target speed V of the reels 9A and 9B is the forward and backward movement of the wire W. May be carried out for each of a plurality of cycles, or may be carried out based on other conditions such as the cutting feed amount of the work 28 and the accumulated work time.

  By the way, the wire saw mentioned above is an illustration of preferable embodiment of the wire saw which concerns on this invention, Comprising: The specific structure of a wire saw can be suitably changed in the range which does not deviate from the summary of this invention. For example, the specific structures of the tension operating devices 18A and 18B can be changed as appropriate. Specifically, a servo motor or the like can be used instead of the swing cylinder 50 as means for swinging the tension arms 19A and 19B. It may be used.

W wire 9A reel (first reel)
9B reel (second reel)
11A reel drive motor (first reel drive means)
11B reel drive motor (second reel drive means)
13 Encoder (first and second speed detection means)
18A First tension operating device (first tension operating means)
18B 2nd tension operation device (2nd tension operation means)
19A Tension arm (first tensioning member)
19B Tension arm (second tension applying member)
25 Roller drive motor (guide roller drive means)
30 Work feeding device (cutting feeding means)
40 Tension detector (first and second tension detecting means)
50 Swing cylinder (first and second position operating means)
52 Encoder (first and second position detecting means)
54 Pneumatic servo circuit (first and second position operation means)
60 controller (wire drive control means and tension control means)
62 Tension adjusting means 64 Speed adjusting means 66 Target speed setting means

Claims (4)

A wire saw in which a cutting wire fed out from a first reel is wound around a plurality of guide rollers and wound around a second reel is used, and a plurality of wires arranged between the guide rollers are connected to the guide rollers. In the method of cutting and feeding the workpiece by moving the workpiece relative to these wires while driving in the axial direction at a predetermined speed by rotational driving,
The wire is fed out from the first reel, and the wire is wound up by the second reel, and the detected tension is predetermined while detecting the tension of the wire fed out from the first reel by the first tension detecting means. The first tension applying member is pressed against the wire so as to approach the feeding side tension of the wire to adjust the tension of the wire, and the tension of the wire wound around the second reel is detected by the second tension detecting means. A forward drive cutting step of cutting the workpiece while pressing the second tension applying member against the wire so that the detected tension approaches a winding side tension lower than the feeding side tension, and adjusting the tension of the wire;
Conversely, the wire wound up by the second reel is fed out from the second reel, and the wire is wound up by the first reel, and the tension of the wire fed out from the second reel is set to the second tension. The tension of the wire wound around the first reel is adjusted by pressing the second tension applying member against the wire so that the detected tension approaches the feeding side tension while being detected by the detecting means. Retracting drive that advances the cutting of the workpiece while adjusting the tension of the wire by pressing the first tension applying member against the wire so that the detected tension approaches the winding side tension while detecting by the first tension detecting means Repeat the cutting process,
In the forward drive cutting step, the wire is fed from the first reel while driving the first reel at a first rotational speed whose peripheral speed is lower than the peripheral speed of the guide roller, and the second reel is Winding the wire with the second reel while driving at a second rotational speed whose peripheral speed is lower than the peripheral speed of the first reel driven at the first rotational speed;
In the reverse drive cutting step, the wire is fed from the second reel while driving the second reel at the first rotational speed, and the first reel is driven at the second rotational speed while driving the first reel. A method for cutting a workpiece, wherein the wire is wound by the first reel. The work cutting method according to claim 1,
The position of the first tension applying member is detected by the first position detecting means, the position of the second tension applying member is detected by the second position detecting means, and the position of each tension applying member is determined in advance as a predetermined reference. The workpiece is cut while adjusting the rotation speed of each reel so as to be close to the position, and the rotation of the first reel when the first tension applying member is substantially at the reference position in a specific cutting step. The speed is detected by the first speed detecting means, and the second speed detecting means detects the rotational speed of the second reel when the second tension applying member is substantially at the reference position, and after the specific cutting step. The first and second rotational speeds are corrected based on the detected speed so that the rotational speed of each reel in the cutting process to be performed approaches the detected speed. That work cutting method. A wire saw for simultaneously cutting a workpiece at a plurality of locations using a cutting wire,
A plurality of guide rollers which are arranged so that rotation center axes thereof are parallel to each other and around which the wire is wound;
Guide roller driving means for driving the guide roller;
First and second reels for respectively feeding and winding the wire to the guide roller;
First and second reel driving means for respectively driving these reels;
Cutting feed means for cutting and feeding the workpiece to the wire by relatively moving a plurality of wires stretched between specific guide rollers of the guide rollers and the workpiece; ,
A forward drive cutting step of feeding the wire from the first reel and advancing the cutting of the workpiece while winding the wire by the second reel; feeding the wire from the second reel; and The rewind drive cutting step of advancing the cutting of the workpiece while winding the wire with the first reel is repeated, and the wire wound around the guide roller is driven at a predetermined speed suitable for cutting the workpiece. Wire drive control means for controlling the guide roller drive means and the first and second reel drive means,
First tension detecting means for detecting a wire tension in a section between the first reel and each guide roller, a first tension applying member pressed against the wire in the section, and a position of the first tension applying member First tension operating means for changing the tension of the wire by changing the position of the first tension applying member;
Second tension detecting means for detecting wire tension in a section between the second reel and each guide roller, a second tension applying member pressed against the wire in the section, and a position of the second tension applying member Second tension operating means for changing the tension of the wire by changing the position of the second tension applying member;
Based on the detected tensions of the first and second tension detecting means, the tension of the wire fed from one of the first and second reels is adjusted to a predetermined feeding side tension, and the other side Tension control means for operating each tension operating means to adjust the tension of the wire wound by the reel of the reel to a predetermined winding-side tension lower than the feeding-side tension,
In the forward drive cutting step, the wire drive control means drives the first reel from the first reel by driving the first reel at a first rotational speed whose peripheral speed is lower than the peripheral speed of the guide roller. By feeding the second reel and driving the second reel at a second rotational speed whose peripheral speed is lower than the peripheral speed of the first reel driven at the first rotational speed, In the reverse drive cutting step, the wire is wound from the second reel by driving the second reel at the first rotational speed, and the first reel is driven. A wire saw, wherein the wire is wound up by the first reel by driving the reel at the second rotational speed. The wire saw according to claim 3,
First and second position detecting means for detecting the positions of the first and second tension applying members, respectively.
First and second speed detecting means for detecting the rotation speeds of the first and second reels, respectively;
The wire drive control unit is configured such that the position of the first tension applying member detected by the first position detecting unit and the position of the second tension applying member detected by the second position detecting unit are respectively set to the reference position. The rotation speed of each reel is controlled so as to approach, and the speed is detected by the first speed detecting means in a specific cutting step, and the detection is made when the first tension applying member is substantially at the reference position. Each of the cutting steps performed after the specific cutting step based on the velocity and the velocity detected by the second velocity detecting means and the detection velocity when the second tension applying member is substantially located at the reference position. A wire saw characterized in that the first and second rotation speeds of the reel are corrected so that the rotation speed of the reel approaches the detection speed.

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