JP6238880B2 - Rotor shaft for galvano scanner, method for manufacturing rotor shaft, and galvano scanner using rotor shaft for galvano scanner - Google Patents

Description

  The present invention relates to a rotor shaft such as a galvano scanner used in, for example, a laser processing machine, a manufacturing method thereof, and a galvano scanner using the rotor shaft.

  Along with the high integration of substrates for mobile phones and electronic devices, laser processing machines that drill holes in such substrates are required to have high precision and high speed. Therefore, it is indispensable to increase the speed of the galvano scanner used in such a laser processing machine.

  However, when continuous drilling is performed using a conventional galvano scanner in a laser processing machine, acceleration → deceleration → stationary operation is repeated. For example, when the continuous drilling speed is 4000 (point / sec), the current frequency is 4 kHz. Since the magnetic flux generated by the current reaches the inside of the permanent magnet, the internal magnetic field of the permanent magnet also changes at 4 kHz, an eddy current flows, and the permanent magnet generates heat by Joule heat. Then, if the temperature of the permanent magnet becomes excessively high, thermal demagnetization occurs and the magnet characteristics deteriorate, which hinders the operation of the galvano scanner.

  Therefore, for example, as in Patent Document 1, a temperature increase of the permanent magnet is suppressed by providing a radial groove in the permanent magnet or by providing a heat transfer bypass means for thermally connecting the coil and the housing. Things have been proposed.

JP 2008-43133 A

  However, in Patent Document 1, since it is necessary to provide a groove in a special heat transfer bypass means or a permanent magnet, there is a problem that the configuration becomes complicated.

  The present invention has been made to solve the above-described problems, and can provide a rotor shaft suitable for high-speed operation by suppressing the temperature increase of the permanent magnet with a simple configuration.

The rotor shaft for a galvano scanner according to the present invention includes a shaft made of a ceramic material and a permanent magnet built in the shaft.

  In addition, the method for manufacturing a rotor shaft according to the present invention includes processing from a block of a carbon fiber reinforced carbon composite (hereinafter referred to as C / C) into a shape of a shaft component before silicon carbide (hereinafter referred to as SiC). It is characterized by.

  According to the rotor shaft of the present invention, since the permanent magnet is built in the shaft made of the ceramic material, the temperature rise of the permanent magnet can be suppressed with a simple configuration, and the effect of obtaining a rotor shaft suitable for high-speed operation is obtained. .

  In addition, according to the method for manufacturing a rotor shaft according to the present invention, since the C / C block is processed into the shape of the shaft component before the SiC conversion, the processing time is shortened and the processing cost is reduced as compared with a normal ceramic material. There is an effect that it can be reduced.

It is a schematic diagram which shows the structure of the galvano scanner incorporating the rotor shaft of this invention. It is an external view of the rotor shaft which shows Embodiment 1 of this invention. It is AA sectional drawing of FIG. It is a figure which shows the result of having compared the characteristic at the time of changing the shaft material in Embodiment 1 of this invention. It is a flowchart which shows the manufacturing process of the rotor shaft of this invention. It is an external view of the rotor shaft which shows Embodiment 2 of this invention. It is BB sectional drawing of FIG.

Embodiment 1 FIG.
Hereinafter, the rotor shaft according to the first embodiment of the present invention will be described with reference to FIGS. 1 to 3.

  In the figure, a galvano scanner 100 is provided to face the outer periphery of the rotor shaft 10, the housing 50 that rotatably supports the rotor shaft 10 via a bearing 40, and the outer periphery of the rotor shaft 10. A fixed coil 30, a rectangular flat galvano mirror 60 as an optical member fixed to one end of the rotor shaft 10, and an encoder plate 70 fixed to the other end of the rotor shaft 10 are provided. The encoder plate 70 has a slit on the surface, and forms a rotary encoder for controlling the angular displacement feedback of the galvanometer mirror 60 in cooperation with a sensor head (not shown). Note that the rotational position detecting device for feedback control of the rotational position of the galvanometer mirror 60 is not limited to the rotary encoder, and a resolver may be used.

  The rotor shaft 10 has a shaft 15 made of a ceramic material and a permanent magnet 20 built in the rotor shaft 15. The permanent magnet 20 is a neodymium sintered magnet, for example, and is provided coaxially with the rotor shaft 15.

  The shaft 15 has a cylindrical portion 15 a that covers the outer peripheral surface of the permanent magnet 20 and a pair of columnar portions 15 b and 15 c that cover both end surfaces of the permanent magnet 20 as shown in the figure. And the shaft 15 is divided | segmented in the axial direction center part of the cylindrical part 15a, and forms shaft components 15A and 15B. The permanent magnet 20 is tightly fixed by an adhesive in the holes formed in the shaft parts 15A and 15B. Further, the joint portions of the shaft components 15A and 15B are also bonded with an adhesive.

As the ceramic material constituting the shaft 15, a carbon fiber-containing silicon carbide composite material (hereinafter referred to as C / SiC) is used, but sintered SiC (hereinafter referred to as SiC), silicon nitride (hereinafter referred to as Si ₃ N ₄ ), It may be boron carbide (hereinafter referred to as B ₄ C) or alumina (hereinafter referred to as Al ₂ O ₃ ).

  Next, laser processing using the galvano scanner 100 will be described. The galvano scanner 100 is arranged such that the galvanometer mirror 60 is positioned in the path of the laser beam of a laser processing machine (not shown). Then, based on the rotational position information of the rotary encoder using the encoder plate 70, the rotational position of the galvano mirror 60 is controlled by a control circuit (not shown). Thereby, the reflection direction of the laser beam is changed, and the irradiation position of the laser beam on the workpiece is controlled.

  First, before the operation, the position of the rotor shaft 10 is initialized and adjusted so that the rotational position of the rotor shaft 10 is located at the reference position. When a current is passed through the coil 30 in this state, the rotor shaft 10 rotates in a direction in accordance with Fleming's left-hand rule due to the interaction with the magnetic flux of the permanent magnet 20. The direction of rotation of the rotor shaft 10 can be changed depending on the direction of current flowing through the coil 30. Therefore, the current direction is determined by position information from the rotary encoder, and the rotor shaft 10 is accelerated and rotated. When approaching the stop position, the rotor shaft 10 is decelerated with the current direction being the reverse direction, and stopped at the target position.

  The galvano scanner 100 repeats the operations of acceleration → deceleration → stop as described above to open holes one by one in order while changing the irradiation position of the laser beam.

  In the above operation, since the magnetic flux generated by the current flowing through the coil 30 reaches the inside of the permanent magnet 20, when the frequency of the current flowing through the coil 30 is increased by increasing the continuous opening speed, the internal magnetic field of the permanent magnet 20 is also increased. It changes in synchronization with the operation speed. For this reason, an eddy current flows through the permanent magnet 20 to cause eddy loss, and the permanent magnet 20 generates heat due to this eddy loss. At this time, the heat generated by the permanent magnet 20 flows to the housing 50 through the shaft 15 and is exhausted to the outside.

  Here, for comparison, the rotor shaft 10 is manufactured using the shaft 15 made of SUS304, and when this rotor shaft 10 is incorporated in the galvano scanner 100 and operated at high speed, SUS304 has low thermal conductivity. The heat generated in the permanent magnet 20 was not sufficiently exhausted, and the temperature of the permanent magnet 20 increased.

  On the other hand, when the shaft 15 is made of C / SiC as described above, the thermal conductivity of C / SiC is 125 W / m · K, and the thermal conductivity of SUS304 is 17.2 W / m · K. Since it was about 7 times, it was confirmed that the heat generated in the permanent magnet 20 was efficiently exhausted from the shaft 15 and the temperature increase of the permanent magnet 20 was suppressed.

  Furthermore, since the volume resistivity of C / SiC is 6100 μΩcm, which is about 85 times the volume resistivity of 72 μΩcm of SUS304, eddy current hardly flows through the shaft 15 and heat generation due to eddy loss is small. This also contributes to suppressing the temperature increase of the permanent magnet 20.

  As described above, according to the present embodiment, since the permanent magnet is built in the shaft made of the ceramic material, the temperature rise of the permanent magnet is suppressed even when the frequency of the current flowing through the coil increases due to high speed operation. And a rotor shaft suitable for high-speed operation can be obtained.

  In addition, since the cylindrical portion of the shaft is divided at the central portion in the axial direction, drilling for incorporating a permanent magnet is facilitated, which is suitable for mass production. In addition, the position which divides | segments a shaft is not restricted to the axial direction center part of a cylindrical part. A similar effect can be obtained by dividing the cylindrical portion of the shaft into a plurality of portions in the axial direction.

  Further, in the high speed operation of the galvano scanner, there is a problem that the rotor shaft resonates at a certain frequency due to the torsional rigidity of the shaft, and the operation cannot be performed at a speed higher than that frequency. The Young's modulus of C / SiC is 350 GPa, which is about 80% larger than the Young's modulus of SUS304, 189 GPa. The specific gravity is 2.95 for C / SiC and 7.9 for SUS304. For this reason, the specific rigidity, which is the ratio between specific gravity and rigidity, is about 5 times that of SUS304 for C / SiC. Therefore, when C / SiC is used for the shaft 15, it is lighter and more rigid than when SUS304 is used, and the torsion of the rotor shaft is reduced, and the resonance frequency is increased, enabling higher speed operation. .

Next, the case where the shaft 15 is made of a material other than SUS304 and C / SiC will be described with reference to FIG. Here, a rotor shaft is manufactured by incorporating a permanent magnet into a shaft made of the material to be compared and having the same shape as the shaft in the present embodiment, and a galvano scanner using these rotor shafts is actually operated at high speed, The characteristics were compared by confirming the temperature rise and the resonance frequency of the rotor shaft. The comparison targets are soft iron (S20C), aluminum (A5052), C / SiC, SiC, Si ₃ N ₄ , B ₄ C, and Al ₂ O ₃ . In FIG. 4, relative evaluation is performed in five stages from 1 to 5, based on the case of using SUS304 that has been generally used conventionally.

As a result of comparison, the resonance frequency of the rotor shaft 10 was increased in the case of SiC, Si ₃ N ₄ , B ₄ C, and Al ₂ O ₃ which are ceramic materials having higher Young's modulus than SUS304. Moreover, since the volume resistivity is large and eddy current does not easily flow through the shaft 15, heat generation due to eddy loss is suppressed, and the effect of suppressing the temperature rise of the permanent magnet 20 can be confirmed. On the other hand, when composed of aluminum (A5052), the resonance frequency decreased and the temperature also increased. In the case of using soft iron (S20C), the resonance frequency was almost the same as that of SUS304, but the temperature rose.

From the above, it was confirmed that the use of the ceramic material for the shaft 15 is suitable for high speed operation. Among them, C / SiC is superior in shape formation and workability compared to SiC, Si ₃ N ₄ , B ₄ C, and Al ₂ O _3, and thus can be quickly and lowly produced in the production of complex microstructures. Production at cost is feasible. For this reason, it is preferable to use C / SiC.

  In FIG. 4, each characteristic is compared in a five-step evaluation. More specifically, in order to set the resonance frequency of the rotor shaft 10 to 7000 Hz or more, the Young's modulus of the shaft material needs to be 300 GPa or more. It was confirmed that there is. Moreover, in order to make shaft temperature 45 degrees C or less, it has confirmed that the volume resistivity of a shaft material needs to be 1 * 10 <-3> ohmcm or more, and heat conductivity must be 100 W / m * K or more. It was.

  Next, the manufacturing method of the rotor shaft in the said Embodiment 1 is demonstrated based on FIG.

  First, as raw material powder, four types of raw materials, PAN-based carbon fiber, pitch-based carbon fiber, graphite powder and powdered phenol resin, are blended at a ratio of 15.3: 40.9: 35.1: 8.7 by weight ratio. And a homogeneous mixture is obtained (mixing step).

  In this mixing step, PAN-based carbon fibers are milled fibers having an average fiber length of 30 μm (MLD-30 milled fibers manufactured by Toray Industries, Inc.), and pitch-based carbon fibers are milled fibers having an average fiber length of 200 μm (Mitsubishi). Chemical K7351M milled fiber), graphite powder manufactured by Wako Pure Chemical Industries, Ltd., and powdered phenol resin PG9400 manufactured by Gunei Chemical Co., Ltd. were used. For mixing, a stirrer with a scraper type rotary blade was used to uniformly disperse and mix.

  Next, the mixture obtained in the mixing step is filled in a molding mold, and then molded by heating and pressing to obtain a carbon fiber reinforced plastic (hereinafter, CFRP) molded body (molding step).

  In this molding step, it is necessary to manage the molding dimensions and weight so that the bulk specific gravity is set in advance. Specifically, the mold having a predetermined weight is flatly filled in a mold for molding, an upper punch is set therein, and the mold is pressurized and compressed to a predetermined dimension, and then up to 150 ° C. The temperature was raised and the mixture was further held for 1 hour to be cured. Then, it cooled and took out from the shaping | molding die. Here, the preset bulk specific gravity, the preset weight, and the preset dimension are values determined at the time of design.

  Further, the molding temperature range in the CFRP molding is in the range of 120 ° C to 170 ° C.

  Moreover, the processing time in shaping | molding shall be 1 hour or more.

  Further, the molding pressure was adjusted so that the bulk specific gravity after molding was 0.85 to 0.95 in order to ensure voids necessary for the later-described silicon impregnation.

  Since the raw material used for the molded body of CFRP is specified as in the above specific example, the bulk specific gravity and the porosity are in a one-to-one relationship. Further, when the bulk specific gravity is high, the void ratio decreases, and conversely, when the bulk specific gravity is low, the void ratio increases. If the bulk specific gravity is high and the porosity is small, the amount of silicon that can be impregnated decreases, and the amount of silicon that reacts with the substrate is insufficient. Thereby, the SiC ratio of C / SiC becomes low, and sufficient characteristics such as volume resistivity cannot be secured. Further, since volume expansion occurs when carbon and silicon react, cracking is likely to occur due to the reaction during silicon impregnation. On the other hand, when the bulk specific gravity is low and the porosity is large, the carbon of the base material that reacts with silicon is insufficient, so the SiC ratio of C / SiC is lowered, and sufficient characteristics cannot be ensured. Therefore, in order to ensure sufficient characteristics, the bulk specific gravity needs to be in the above range.

  Subsequently, the molded body obtained in the molding step is heat-treated, and the CFRP matrix resin is pyrolyzed and carbonized to obtain a C / C block (carbonization step).

  In this carbonization step, the molded body was heat-treated at a temperature of about 700 ° C. to 1000 ° C. in an inert atmosphere such as nitrogen or argon. The temperature was raised from room temperature to 200 ° C at 20 ° C / h, then up to 700 ° C at 7 ° C / h and up to 900 ° C at 15 ° C / h. And after hold | maintaining for 5 hours, it cooled.

  In addition, in the said heat processing, it is necessary to heat-process at 600 degreeC or more, and if it is 800 degreeC or more, it is preferable. In order for the carbonization reaction to be sufficiently completed and stabilized, the holding time at the maximum temperature requires 2 hours or more.

  Next, the C / C block obtained in the carbonization step is processed into the shape of a shaft component by grinding to obtain a C / C shaft component (primary processing step).

  In this primary processing step, hole processing and outer periphery processing for arranging permanent magnets are performed in a subsequent step. Of these, hole machining must be performed in the primary machining process, but in the primary machining process, only a simple rod shape matching the outermost circumference of the shaft is used in the primary machining process. The processing may be performed in a secondary processing step after conversion to SiC.

  The reason for performing the hole processing in the primary processing step is that, after the formation of SiC performed in the subsequent step, the workability deteriorates like a normal ceramic material, and the shape processing becomes difficult. After using SiC, when using a small jig such as drilling, the influence of workability deterioration is large, and enormous machining time is required. For this reason, the hole processing is performed in the primary processing step.

  On the other hand, since the outer peripheral machining uses a large grinding jig, it is not easily affected by deterioration in workability, so in the primary machining process, only a simple rod shape matching the outermost circumference of the shaft is used, and detailed step machining is performed. May be performed in a secondary processing step.

  Next, the C / C shaft component obtained in the primary processing step is melted and impregnated with metallic silicon to react SiC with carbon and silicon, thereby converting the C / SiC shaft component into a SiC component. Obtain (silicon impregnation step).

  In this silicon impregnation step, the C / C shaft part was heated to 1600 ° C. at 2 ° C./h, and then held for 1 hour for melt impregnation.

  Next, an adhesive is applied to the magnet before magnetization, and is inserted into the hole of one C / SiC shaft part. Then, it inserts in the hole of the other C / SiC shaft part. Thereafter, the C / SiC shaft component and the magnet before magnetization are combined and bonded together to be integrated (bonding step).

  In the bonding between the magnet before magnetization and the C / SiC shaft component, an adhesive is applied so that the entire magnet before magnetization is in close contact with the C / SiC shaft component. To be wide. Also, since the adhesive is not high in thermal conductivity, the adhesive layer should be as thin as possible.

  Next, an outer finishing process is performed on the member obtained in the bonding step to form a shaft (secondary processing step).

  In addition, it finished so that the thickness of the cylindrical part which covers the outer peripheral surface of the magnet before the said magnetization might be set to 0.2 mm.

  Finally, the magnet before magnetization is exposed to a high magnetic field and magnetized to make a permanent magnet (magnetization step). In this way, a rotor shaft in which a permanent magnet is built in a shaft made of C / SiC is completed.

  In the manufacturing method of the rotor shaft as described above, in the shape processing of the shaft part obtained from the C / C block, the shape processing is performed before the conversion to SiC, so that accurate processing is possible and the processing time is reduced. Can be shortened.

Embodiment 2. FIG.
Next, the rotor shaft according to the second embodiment will be described with reference to FIGS.

  As shown in the figure, the shaft 151 has a cylindrical portion 151 a that covers the outer peripheral surface of the permanent magnet 201, and a pair of columnar portions 151 b and 151 c that cover both end surfaces of the permanent magnet 201. And the shaft 151 is divided | segmented by the axial direction both ends of the cylindrical part 151a, and forms the shaft components 151A-151C. Permanent magnets 201 are tightly fixed by an adhesive in holes formed in the shaft parts 151A and 151B. Moreover, the joint part of shaft components 151A-151C is also adhere | attached with the adhesive agent.

  In the second embodiment, there is a shaft component 151C consisting of only a cylindrical portion in the middle of the shaft 151. Therefore, the height of the cylindrical portions of the shaft components 151A and 151B at both ends in the axial direction is the shaft component in the first embodiment. It is lower than the height of the cylindrical portions of 15A and 15B. For this reason, in the formation of the shaft parts 151A and 151B, the holes made in the shaft parts 151A and 151B may be shallower than the holes made in the shaft parts 15A and 15B, so that processing is easy. Further, since the intermediate shaft part 151C is configured only from the cylindrical portion, the shape is simple, and thus the manufacture becomes easy. Therefore, the rotor shaft of the second embodiment has an effect that the processing time can be further shortened and the processing cost can be reduced, and the manufacturing can be facilitated. In addition, the position which divides | segments a shaft is not restricted to the axial direction both ends of a cylindrical part. A similar effect can be obtained by dividing the cylindrical portion of the shaft into a plurality of portions in the axial direction.

10 Rotor shaft, 15, 151 Shaft, 15A, 15B, 151A, 151B, 151C Shaft part, 15a, 151a Tubular part, 15b, 15c, 151b, 151c Columnar part, 20, 201 Permanent magnet, 30 Coil, 40 Bearing, 50 housing, 60 galvanometer mirror (optical member), 70 encoder plate, 100 galvanometer scanner.

Claims (9)

A galvano scanner rotor shaft comprising a shaft made of a ceramic material and a permanent magnet built in the shaft ,
The ceramic material has a volume resistivity of 1 × 10 ⁻³ Ωcm or more and a thermal conductivity of 100 W / m · K or more.
A rotor shaft for a galvano scanner . The rotor shaft for a galvano scanner according to claim 1, wherein the permanent magnet is provided coaxially with the shaft. The rotor shaft for a galvano scanner according to claim 1, wherein the shaft includes a cylindrical portion that covers an outer peripheral surface of the permanent magnet, and a columnar portion that covers both end surfaces of the permanent magnet. The rotor shaft for a galvano scanner according to claim 3, wherein the cylindrical portion is divided into a plurality of portions in the axial direction. The rotor shaft for a galvano scanner according to any one of claims 1 to 4, wherein the ceramic material is a carbon fiber-containing silicon carbide composite material. The rotor shaft for a galvano scanner according to any one of claims 1 to 4, wherein the ceramic material is silicon nitride, alumina, silicon carbide, or boron carbide. The rotor shaft for a galvano scanner according to any one of claims 1 to 4, wherein the ceramic material has a Young's modulus of 300 GPa or more. A rotor shaft for a galvano scanner according to any one of claims 1 to 7 ,
A housing for rotatably supporting the rotor shaft for the galvano scanner ;
A coil provided opposite to the outer periphery of the rotor shaft for the galvano scanner and fixed to the inner peripheral surface of the housing;
An galvano scanner comprising: an optical member coupled to one axial end of the rotor shaft for the galvano scanner. A mixing step of mixing PAN-based carbon fiber, pitch-based carbon fiber, graphite powder and resin powder to obtain a mixture;
A molding step of molding and curing the mixture to obtain a molded body; and
Carbonization step of carbonizing the molded body to obtain a carbon fiber reinforced carbon composite block;
A primary processing step of processing the block into the shape of a shaft component;
A silicon impregnation step of melt-impregnating metal silicon into the member obtained in the primary processing step to form silicon carbide;
A bonding step in which the member obtained in the silicon impregnation step and the magnet before magnetization are combined by bonding;
A secondary processing step of finishing the member obtained in the bonding step;
And a magnetizing step of magnetizing the magnet before magnetizing.

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