Patent Publication Number: US-2022212270-A1

Title: Built-in type supersonic spindle and excitation method using same

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to a built-in type spindle, and more particularly, to a built-in type supersonic spindle, which includes a housing having a built-in spindle unit therein and a supersonic vibrator pressing the built-in spindle unit in order to enhance machining accuracy and reduce a damage of a bearing by vibrating a spindle and the bearing at the same time, and an excitation method using the built-in type supersonic spindle. 
     Background Art 
     In general, a machine tool has a spindle mounted to rotate the tool, and a built-in type spindle has means for generating rotary power in order to rotate a main shaft of the spindle. 
     Such a built-in type spindle is reduced in the whole volume since having the means for generating rotary power mounted therein, and improves machining accuracy since the rotary power generating means directly rotates the main shaft. 
     Meanwhile, recently, supersonic machining methods for performing machining by vibrating the spindle using an excitation part have been proposed. Such supersonic machining methods reduce machining period and expand the lifespan of tools. 
     As shown in  FIG. 1 , a spindle  13  is rotated by a motor  11 , and is supported by a bearing  14 . In this instance, a supersonic vibrator  16  is disposed at one side of the spindle  13  to generate vibration, and the generated vibration is transmitted to a machining tool holder  4  through a support horn  17 . The machining tool  3  disposed on the machining tool holder  4  receives rotary power and vibration at the same time. (refer to Korean Patent No. 10-1904799) 
     However, such a conventional art has a disadvantage in that vibration is transmitted to the bearing  14 , which is in a stationary state, since only the spindle  13  is vibrated and rotated, thus it causes a damage of the bearing and deteriorates machining accuracy. 
     Meanwhile, because the built-in type spindle and the supersonic spindle have been known widely and are described in the following conventional art literature in detail, descriptions and drawings of them will be omitted. 
     PATENT LITERATURE 
     Patent Documents 
     Korean Patent No. 10-2157402 
     Korean Patent No. 10-2186473 
     Korean Patent No. 10-1904799 
     Korean Utility Model Publication No. 20-1999-003869 
     SUMMARY OF THE INVENTION 
     Accordingly, the present invention has been made to solve the above-mentioned problems occurring in the prior arts, and it is an object of the present invention to provide a built-in type supersonic spindle, which includes a main case in which a built-in spindle unit is embedded, and an interworking bar disposed in the main case to transmit vibration to the built-in spindle unit in order to enhance machining accuracy and reduce a damage of a bearing by vibrating the main case and the built-in spindle at the same time, and an excitation method using the built-in type supersonic spindle. 
     Objects of the present invention are not limited to the objects described above, and other objects that are not described will be clearly understood by a person skilled in the art from the description below. 
     To accomplish the above object, according to the present invention, there is provided a built-in type supersonic spindle including: a housing in which a supersonic vibrator is disposed at one side; and a built-in spindle unit disposed inside the housing, wherein the supersonic vibrator gets in contact with the built-in spindle unit in order to transmit vibration generated from the supersonic vibrator to the built-in spindle unit, and a spindle of the built-in spindle unit is vibrated together with a bearing, and is supported by the bearing to be rotatable. 
     Moreover, the housing includes: a housing body; a first opening part formed at one side of the housing body to expose a portion of the supersonic vibrator to the outside; and a second opening part formed at the other side of the housing body to expose a portion of the spindle so that a machining too is combined with the second opening part, and the built-in spindle unit includes a spindle case in which the spindle and the bearing are accommodated. 
     Furthermore, the built-in type supersonic spindle further includes a magnetic levitation unit disposed between the housing and the built-in spindle unit to make the built-in spindle unit float inside the housing. 
     Additionally, the magnetic levitation unit includes an axially magnetic levitation unit and a radially magnetic levitation unit, the axially magnetic levitation unit is arranged in an axial direction of the spindle between the housing and the built-in spindle unit, and the radially magnetic levitation unit is arranged in a radial direction of the spindle between the housing and the built-in spindle unit. The built-in spindle unit is spaced apart in the axial direction and in the radial direction inside the housing at predetermined intervals. 
     In addition, the axially magnetic levitation unit includes: a first axially magnetic levitation unit arranged between the side of the spindle case, which directs the supersonic vibrator, and the inner surface of the housing opposed to the side; and a second axially magnetic levitation unit arranged between the side of the spindle case, which directs the machining tool, and the inner surface of the housing opposed to the side of the spindle case, which directs the machining tool. 
     Moreover, the radially magnetic levitation unit is arranged between the inner face of the housing in the radial direction and the outer surface of the spindle case in the radial direction. 
     Furthermore, the magnetic levitation units are disposed in a pair, and the housing and the spindle case keep an interval therebetween by a mutually exclusive force using electromagnets having the same polarity. 
     Additionally, the built-in spindle unit includes a preload adjusting part disposed between the spindle and the spindle case to adjust preload of the bearing, and the preload adjusting part includes: a support part mounted on the inner surface of the spindle case; a contact part disposed between the bearing and the support part and getting in contact with an outer wheel of the bearing; and an elastic pressurizing part disposed at one side of the support part to pressurize the contact part. 
     In addition, the support part includes: a support part body, which is fixed on the inner surface of the spindle case, and of which one end is bent at a specific angle; and an insertion groove recessed at the bent portion of the support part body so that one end of the elastic pressurizing part is inserted into the insertion groove. 
     Moreover, the contact part includes: a bar-shaped first contact part body; and a second contact part body extending in the direction of the support part from the first contact part, and the second contact part body increases in thickness in the central direction of the spindle case so as to be thicker than the first contact part body. The side of the second contact part body in the direction of the support part gets in contact with the bent portion of the support part body, and the contact part includes an insertion groove formed at a recessed portion thereof so that the other end of the elastic pressurizing part is inserted thereinto, and a protrusion part protrudes on the side of the second contact part body in the opposite direction of the support part to pressurize the outer wheel of the bearing. 
     In another aspect of the present invention, the present invention provides an excitation method using the supersonic spindle includes the steps of: vibrating the built-in spindle unit by the supersonic vibrator, so that the spindle and the bearing of the built-in spindle unit are vibrated at the same time; rotating the spindle by the driving part of the built-in spindle unit; and vibrating and rotating the machining tool disposed on the spindle at the same time, so that a workpiece is machined. 
     Furthermore, the built-in spindle unit floats inside the housing by the magnetic levitation unit. 
     The above and other objects, features and advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings. 
     The terms and words used in the specification and claims must not be limited to typical or dictionary meanings, but must be regarded as concepts selected by the inventor as concepts which best illustrate the present invention, and must be interpreted as having meanings and concepts adapted to the scope and spirit of the present invention to aid in understanding the technology of the present invention. 
     The built-in type supersonic spindle and the excitation method using the same according to the present invention can prevent a damage of the bearing caused by excitation and enhance machining accuracy. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other objects, features and advantages of the present invention will be apparent from the following detailed description of the preferred embodiments of the invention in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a schematic diagram of a general supersonic spindle; 
         FIG. 2  is a schematic diagram of a supersonic spindle according to an embodiment of the present invention; 
         FIG. 3  is a schematic diagram and a partially enlarged view showing a housing and a magnetic levitation unit except a built-in spindle unit as the supersonic spindle according to the embodiment of the present invention; 
         FIGS. 4 and 5  are a partially enlarged view and an exploded view of a preload control part of the supersonic spindle according to the embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings. In the drawings, thicknesses of lines and sizes of constituent elements may be exaggerated for clarity and convenience in explanation. 
     Further, wordings to be described later are defined in consideration of the functions of the present invention, and may differ depending on the intentions of a user or an operator or custom. Accordingly, such wordings should be defined on the basis of the contents of the overall specification. 
     In addition, the embodiment disclosed hereinafter does not limit the scope of the present invention, but corresponds to merely exemplary terms of constituent elements presented in claims of the present invention, and the embodiments that include replaceable constituent elements as equivalents of the constituent elements defined in the overall specification and claims may be included in the scope of the present invention. 
     As shown in  FIGS. 2 to 5 , the built-in type supersonic spindle according to an embodiment of the present invention includes: a housing  100  in which a supersonic vibrator  300  is disposed at one side; and a built-in spindle unit  200  disposed inside the housing  100 . In this instance, the supersonic vibrator  300  gets in contact with the built-in spindle unit  200  in order to transmit vibration generated from the supersonic vibrator  300  to the built-in spindle unit  200 . That is, because the built-in spindle unit  200  is vibrated, a spindle  210  of the built-in spindle unit  200  is also vibrated together with a bearing  240 . In the above state, the spindle  210  is supported by the bearing  240  to be rotatable. 
     As widely known, the built-in spindle unit  200  adopts the method that the spindle  210  buried therein is driven by a driving part  220 . The driving part  220  includes a stator  221  and a rotor  222 , and the rotor  222  is rotated by an action with the stator  221 . In this instance, because the rotor  222  interworks with the spindle  210 , the spindle  210  is rotated in interworking with rotation of the rotor  222 . Moreover, the spindle  210  and the driving part  220  are accommodated in the spindle case  230 , and such a built-in spindle unit has been known widely. Especially, because such a built-in spindle unit is described in Korean Utility Model Registration No. 20-0215503 in detail, detailed description and drawings thereof will be omitted. 
     As described above, the vibration generated from the supersonic vibrator  300  is transmitted to the built-in spindle unit  200 , so the built-in spindle unit  200  is vibrated. That is, the spindle  210  of the built-in spindle unit  200  is vibrated together with the bearing  240 . Therefore, the spindle  210  and the bearing  240  do not generated relative motion in an excitation direction. For instance, as shown in  FIG. 2 , if the built-in spindle unit  100  is vibrated in a direction  1 , the spindle  210  and the bearing  240  are all vibrated in the direction  1 . Therefore, the spindle  210  and the bearing  240  do not generate relative motion in the direction  1 . In the above state, the spindle  210  gets in contact with the bearing  240  and is rotated. 
     According to the conventional arts, because only the spindle  13  is vibrated and the bearing  14  keeps the stationary state, vibration transmitted to the spindle  13  is transmitted to the bearing  14  and it causes a damage of the bearing  14  (see  FIG. 1 ). 
     In order to solve the above problem of the conventional arts, because the entire built-in spindle unit  200  is vibrated by the supersonic rotator, the spindle  210  and the bearing  240  are vibrated together. Therefore, differently from the conventional arts, the present invention can prevent a damage of the bearing since vibration is not transmitted from the spindle  210  to the bearing  240 . 
     In the meantime, the housing  100  of the present invention accommodates the supersonic vibrator  300  and the built-in spindle unit  200  therein. For this, the housing  100  includes: a housing body  110 ; a first opening part  120  formed at one side of the housing body  110  to expose a portion of the supersonic vibrator  300  to the outside; and a second opening part  130  formed at the other side of the housing body  110  to expose a portion of the spindle  210  so that a machining too T is combined with the second opening part  130 . 
     Referring to  FIG. 3 , the housing body  110  is formed in a cylindrical shape, and is empty. In the right direction of the drawing, the housing body  110  has the first opening part  120 . Furthermore, in the left direction of the drawing, the housing body  110  has the second opening part  130 . The supersonic vibrator  300  may be mounted through the first opening part  120 . As shown in  FIG. 1 , the supersonic vibrator  300  includes: a supersonic vibrator body  310  for generating vibration; and a supply terminal  320  disposed on the supersonic vibrator body  310  to receive electric power from the outside. Such a supply terminal  320  is exposed to the outside through the first opening part  120  to receive electric power. The supersonic vibrator body  310  repeats expansion and contraction according to power supply using a piezo element, and the detailed description and drawing thereof will be omitted since the above-mentioned technology has been known widely. The supersonic vibrator body  310  gets in contact with the built-in spindle unit  200  to transmit vibration. 
     As described above, because the built-in spindle unit  200  receives vibration from the supersonic vibrator  300 , it is necessary to maintain an interval between the built-in spindle unit  200  and the housing  100 . For this, a magnetic levitation unit  500  is disposed between the housing  100  and the built-in spindle unit  200 . 
     Additionally, the built-in spindle unit  200  includes a spindle case  230  in which the spindle  210  and the bearing  240  are disposed. 
     The magnetic levitation unit  500  includes an axially magnetic levitation unit AX and a radially magnetic levitation unit  510 . The axially magnetic levitation unit AX is arranged in an axial direction of the spindle  210  between the housing  100  and the built-in spindle unit  200 , and the radially magnetic levitation unit  510  is arranged in a radial direction of the spindle  210  between the housing  100  and the built-in spindle unit  200 . That is, the built-in spindle unit  200  can keep a state where it is spaced apart in the axial direction inside the housing  100  at a predetermined interval by the axially magnetic levitation unit AX. Moreover, the built-in spindle unit  200  is spaced apart in the radial direction inside the housing  100  at a predetermined interval by the radially magnetic levitation unit  510 . In other words, the built-in spindle unit  200  floats inside the housing  100  and is spaced apart in the axial and radial directions at the predetermined intervals by the magnetic levitation unit  500  so as to prevent mutual collision and to realize stable machining. 
     As shown in  FIGS. 2 and 3 , the radially magnetic levitation unit  510  is arranged between the inner surface of the housing  100  in the radial direction and the outer surface of the spindle case  230  in the radial direction. That is, the radial direction distance between the housing  100  and the built-in spindle unit  200  is kept constantly by the radially magnetic levitation unit  510 , and so, it prevent crash between the built-in spindle unit  200  and the housing  100 . The radially magnetic levitation unit  510  includes a first-first magnetic levitation unit  511  attached to the outer surface of the spindle case  230  in the radial direction; and a first-second magnetic levitation unit  512  attached to the inner surface of the housing  100 . The first-first magnetic levitation unit  511  and the first-second magnetic levitation unit  512  keep an interval between the housing  100  and the spindle case  230  by a mutually exclusive force using electromagnets having the same polarity. Because the same applies to a second axially magnetic levitation unit  520 , which will be described later, hereinafter, repeated description will be omitted. Meanwhile, as shown in the drawings, a plurality of the radially magnetic levitation units  510  are disposed in a lateral direction in the drawings. 
     The axially magnetic levitation unit AX includes: a first axially magnetic levitation unit  520  arranged between the side of the spindle case  230 , which directs the supersonic vibrator  300 , and the inner surface of the housing  100  opposed to the side; and a second axially magnetic levitation unit  530  arranged between the side of the spindle case  230 , which directs the machining tool T, and the inner surface of the housing  100  opposed to the side of the spindle case  230 , which directs the machining tool T. The built-in spindle unit  200  can keep the state where it is spaced apart in the axial direction inside the housing  100 . 
     In the meantime, a pair of the first axially magnetic levitation units  520  are arranged between the side of the spindle case  230 , which directs the supersonic vibrator  300 , and the inner surface of the housing  100  opposed to the side. As shown in  FIGS. 2 and 3 , a pair of the first axially magnetic levitation units  520  are arranged between the direction of the supersonic vibrator  300 , namely, the right side of the spindle case  230  of the built-in spindle unit  200  in the drawings, and the inner surface of the housing  100  opposed to the right side. The first axially magnetic levitation unit  520  includes: a second-first magnetic levitation unit  521  arranged on the right side of the spindle case  230  in the drawings; and a second-second magnetic levitation unit  522  attached to the inner surface of the housing  100 . Therefore, the spindle case  230  and the housing  100  can be spaced apart from each other by a repulsive force generated between the second-first magnetic levitation unit  521  and the second-second magnetic levitation unit  522 . 
     a pair of the second axially magnetic levitation units  530  are arranged between the side of the spindle case  230 , which directs the machining tool T, and the inner surface of the housing  100  opposed to the side. As shown in  FIGS. 2 and 3 , a pair of the second axially magnetic levitation units  530  are arranged between the direction of the machining tool T, namely, the left side of the spindle case  230  of the built-in spindle unit  200  in the drawings, and the inner surface of the housing  100  opposed to the left side. The second axially magnetic levitation unit  530  includes: a third-first magnetic levitation unit  531  arranged on the left side of the spindle case  230  in the drawings; and a third-second magnetic levitation unit  532  attached to the inner surface of the housing  100 . Therefore, the spindle case  230  and the housing  100  can be spaced apart from each other by a repulsive force generated between the third-first magnetic levitation unit  531  and the third-second magnetic levitation unit  532 . 
     As described above, the magnetic levitation units  500  according to the present invention are disposed in the radial directions and the right and left sides of the housing  100  and the spindle case  230 , so that the spindle case  230  maintains an interval from the housing  100 . 
     As described above, the spindle  230  is supported by the bearing  240 , and it is necessary to adjust preload acting to the bearing  240  for silent driving even though there is a change in rotational speed of the spindle  230 . For this, the built-in spindle unit  200  according to the present invention includes a preload adjusting part  250  disposed between the spindle  210  and the spindle case  230  to adjust preload of the bearing  240 . As shown in  FIGS. 4 and 5 , the preload adjusting part  250  includes: a support part  251  mounted on the inner surface of the spindle case  230 ; a contact part  252  disposed between the bearing  240  and the support part  251  and getting in contact with an outer wheel  241  of the bearing  240 ; and an elastic pressurizing part  253  disposed at one side of the support part  251  to pressurize the contact part  252 . That is, the support part  251  is fixed to the inner surface of the spindle case  230 . The outer wheel  241  of the bearing  240  is pressurized by the contact part  252 , and the contact part  252  is supported by the support part  251 . 
     Such a support part  251  includes: a support part body  251 - 1 , which is fixed on the inner surface of the spindle case  230 , and of which one end is bent at a specific angle; and an insertion groove  251 - 2  recessed at the bent portion of the support part body  251  so that one end of the elastic pressurizing part  253  (left end in the drawing) is inserted into the insertion groove  251 - 2 . As shown in  FIGS. 4 and 5 , the support part body  251 - 1  includes: a horizontal support part  251 - 11  arranged in a horizontal direction and fixed to the inner surface of the spindle case  230 ; and a vertical support part  251 - 12  bent at one end of the horizontal support part  251 - 11  and extending in the direction of the spindle  210 . In this instance, the insertion groove  251 - 2  may be formed on the side of the vertical support part  251 - 12  in the direction of the contact part  252 . 
     The contact part  252  includes: a bar-shaped first contact part body  252 - 1 ; and a second contact part body  252 - 2  extending in the direction of the support part  251  from the first contact part  252 - 1 . That is, the second contact part body  252 - 2  extends in the direction of the support part  251  from the first contact part body  252 - 1 , namely, in the left direction in the drawing. Such a second contact part body  252 - 2  increases in thickness in the central direction of the spindle case  230  so as to be thicker than the first contact part body  252 - 1 , and protrudes in the central direction of the spindle case  230 . In this instance, the side of the second contact part body  252 - 2  in the direction of the support part  251 , namely, the side in the left direction in the drawing, gets in contact with the bent portion, namely, the vertical support part  251 - 12 , of the support part body  251 , and the contact part  252  includes an insertion groove  252 - 3  formed at a recessed portion thereof so that the other end (right end in the drawing) of the elastic pressurizing part  253  is inserted thereinto. Moreover, the contact part  252  further includes a protrusion part  252 - 4  protruding on the side of the second contact part body  252 - 2  in the opposite direction of the support part  251  (right side in the drawing), and the protrusion part  252 - 4  pressurizes the outer wheel  241  of the bearing  240  to adjust preload. 
     That is, the contact part  252  is supported by the support part  251  to be pressurized first, and then, is second pressurized by the elastic pressurizing part  253 . In this instance, the elastic pressurizing part  253  may use a coil spring, which is known widely. The elastic pressurizing part  253  is transformed elastically to adjust pressure of the contact part  252 . Therefore, the contact part  252  can adjust the power to pressurize the outer wheel  241 . In the meantime, the side of the contact part  252  in the opposite direction of the support part  251  may be supported by a support plate  254  and a base  255 . 
     Hereinafter, referring to  FIGS. 2 to 5 , a machining method using the supersonic spindle will be described. 
     First, the supersonic vibrator  300  vibrates the built-in spindle unit  200 , so that the spindle  210  and the bearing  240  of the built-in spindle unit  200  are vibrated at the same time. As described, because the supersonic vibrator  300  pressurizes the spindle case  230  of the built-in spindle unit  200 , the entire built-in spindle unit  200  is vibrated so that the spindle  210  and the bearing  240  are vibrated at the same time. 
     In other words, because the spindle  210  and the bearing  240  are vibrated at the same time, differently from the conventional arts, there is no damage in the bearing. In the above state, the spindle  210  is rotated by the driving part  220  of the built-in spindle unit  200 , so the machining tool T disposed on the spindle  210  is simultaneously vibrated and rotated, so that a workpiece is machined. 
     The built-in type supersonic spindle and the excitation method using the same according to the present invention can prevent a damage of the bearing caused by excitation and enhance machining accuracy. 
     Although exemplary embodiments of the present invention have been disclosed for illustrative purposes, it will be appreciated that the present invention is not limited thereto, and those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention. 
     Accordingly, any and all modifications, variations or equivalent arrangements should be considered to be within the scope of the invention, and the detailed scope of the invention will be disclosed by the accompanying claims.