Patent Publication Number: US-10760578-B2

Title: Vacuum pump with heat generation element in relation to housing

Description:
BACKGROUND OF THE INVENTION 
     1. Technical Field 
     The present invention relates to an integrated vacuum pump configured such that a pump device and a control device are integrated. 
     2. Background Art 
     A turbo-molecular pump has been used as a vacuum pump used for a semiconductor manufacturing device, an analysis device, etc. The turbo-molecular pump includes a pump device and a control device having a drive circuit, a control circuit, etc. for driving and controlling a motor etc. in the pump device. 
     In the turbo-molecular pump, a rotor provided with multiple stages of rotor blades is rotated at high speed for air discharging, and therefore, a bearing configured to rotatably support a shaft as a rotary shaft of the rotor in the vicinity of each end of the shaft is provided. A grease lubrication type ball bearing or a magnetic bearing utilizing attractive repulsion of a permanent magnet or an electromagnet is used as the bearing. The magnetic bearing has an advantage that is contactless, but is larger and needs a higher cost as compared to the ball bearing. For this reason, in a compact pump, the magnetic bearing is used at one suction port side (high vacuum side) end portion of the shaft, but the compact low-cost grease lubrication type ball bearing is generally used at the other exhaust port side (low vacuum side) end portion. 
     For reducing the size of the turbo-molecular pump, integration of a pump device and a control device as described in Patent Literature 1 (JP-A-2014-105695) has been known. In a turbo-molecular pump described in Patent Literature 1, a recessed portion is formed at a side surface of a base of the pump device configured to perform vacuum pumping, and the control device including a board on which an electronic component is mounted is housed in the recessed portion. In this manner, the size is reduced. 
     In the turbo-molecular pump, driving with high power is necessary for rotating the rotor at high speed, and for this reason, the drive circuit in the control device is specifically a great heat generation source. In the case of integrating the pump device and the control device for size reduction, heat generated at a heat generation element such as the drive circuit in the control device is transmitted to the pump device. This leads to a problem that when such heat is transmitted to the ball bearing supporting the rotor, a lubricant of the ball bearing such as grease is heated and evaporated and the life of the ball bearing is shortened. 
     SUMMARY OF THE INVENTION 
     A vacuum pump comprises: a pump device configured to rotate a rotor about a rotation axis supported by a ball bearing, thereby discharging gas sucked through a pump suction port from a pump exhaust port; and a control device attached to a side surface along a direction of the rotation axis of the pump device, including an electronic circuit having a heat generation element and a housing configured to house the electronic circuit, and configured to control operation of the pump device. The heat generation element directly contacts an outer plate of the housing not contacting the pump device, and does not contact an outer plate of the housing contacting the pump device. 
     The housing is a substantially rectangular parallelepiped body having a longitudinal direction along the direction of the rotation axis, and the outer plate of the housing contacting the heat generation element is an outer plate extending along the direction of the rotation axis. 
     The housing contacts the pump device via a heat insulating member. 
     The vacuum pump further comprises: a cooling fan placed on an outer surface of the pump device and configured to cool the pump device. 
     The control device is placed on a cooling path of cooling wind from the cooling fan. 
     The cooling fan is placed on a side of the pump device opposite to the control device with respect to the rotation axis. 
     The heat generation element is connected to the outer plate of the housing via a heat transfer member. 
     a portion of a side surface of the pump device facing the control device is a flat surface, and a clearance between the flat surface and the control device is provided. 
     The outer plate of the housing which the heat generation element directly contacts is made of metal. 
     The outer plates are joined with each other via a high thermal resistive seal material. 
     According to the present invention, heat generated from a heat generation element in a control device is released from a housing of the control device to the outside. Consequently, an increase in the temperature of a ball bearing can be prevented. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a sectional view of a turbo-molecular pump  1  of a first embodiment; 
         FIG. 2  is a sectional view of a control device  100 ; 
         FIG. 3  is a sectional view of a turbo-molecular pump  1 A of a second embodiment; 
         FIG. 4  is a perspective view of a turbo-molecular pump  1 B of a third embodiment; 
         FIG. 5  is a bottom view of the turbo-molecular pump  1 B of the third embodiment; and 
         FIG. 6  is a perspective view of a turbo-molecular pump  1 C of a fourth embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS 
     First Embodiment 
     Hereinafter, a first embodiment of the present invention will be described with reference to the drawings.  FIG. 1  is a sectional view of a vacuum pump of the first embodiment of the present invention. 
     A turbo-molecular pump  1  has a pump device  10  configured to perform vacuum pumping, and a control device  100  configured to drive the pump device  10 . An attachment surface  23  is formed at a side surface of a base  2  of the pump device  10 , and the control device  100  is attached to the attachment surface  23  with bolts. 
     A structure of the pump device  10  will be described. The pump device  10  includes, as exhaust functional portions, a turbo pump portion having turbine blades, and a Holweck pump portion having a spiral groove. 
     The turbo pump portion includes multiple stages of rotor blades  30  formed at a rotor  3 , and multiple stages of stationary blades  20  arranged on a pump case  12  side. On the other hand, the Holweck pump portion provided on a downstream side of the turbo pump portion includes a pair of cylindrical portions  31   a ,  31   b  formed at the rotor  3 , and a pair of stators  21   a ,  21   b  arranged on a base  2  side. Of inner and outer peripheral surfaces of the cylindrical stators  21   a ,  21   b , peripheral surfaces facing the cylindrical portions  31   a ,  31   b  are provided with the spiral groove. Note that instead of providing the spiral groove on a stator side, the spiral groove may be provided on a rotor side. 
     The rotor  3  is fastened to a shaft  5 , and the rotor  3  and the shaft  5  form an integrated rotary body. The shaft  5  is rotatably driven by a motor  4 . A motor rotor  4   a  is provided at the shaft  5 , and a motor stator  4   b  is fixed to the base  2 . A lower end side of the shaft  5  is held by a ball bearing  8  in which grease is sealed. On the other hand, an upper end side of the shaft  5  is non-contact supported by a permanent magnet magnetic bearing  6  using permanent magnets  6   a ,  6   b . By these upper and lower bearings, the shaft  5  and the rotor are rotatably supported about a rotation axis AX of the rotor. 
     The vacuum pump of the present example has a touchdown bearing configured to limit runout of a shaft upper portion in a radial direction, such as a ball bearing  9 . The ball bearing  9  is housed in a magnet holder  11 . That is, in a steady rotation state of the rotor  3 , the shaft  5  and the ball bearing  9  do not contact each other. Note that in the case of applying great disturbance or great whirling of the rotor  3  upon acceleration or deceleration of rotation, the shaft  5  comes into contact with an inner ring of the ball bearing  9 . For example, deep groove ball bearings are used as the ball bearings  8 ,  9 . 
     A base cover  27  configured to seal an opening  24  upon attachment/detachment of the ball bearing  8  is bolted to a bottom surface of the base  2 . At a pump case  12 , a suction port flange  12   a  configured to fix the pump device  10  to, e.g., a chamber is formed. Moreover, an exhaust port  22  is provided at a side surface of the base  2 . Gas molecules having flowed in through the suction port flange  12   a  are transferred to the pump downstream side by the turbo pump portion and the Holweck pump portion, and then, are discharged through the exhaust port  22 . 
     Next, the control device  100  will be described with reference to  FIGS. 1 and 2 . 
       FIG. 2  is an enlarged sectional view of the control device  100  illustrated in the sectional view of  FIG. 1 . The control device  100  includes an electronic circuit having a power semiconductor element configured to drive the motor  4  in the pump device  10 , a circuit board  102 , etc., and a housing  101  configured to house the electronic circuit. The outer shape of the housing  101  is a substantially rectangular parallelepiped shape, but is not limited to such a shape. The outer shape of the housing  101  may be any shape. Of six outer plates forming such a rectangular parallelepiped shape, the sections of four outer plates  101   a ,  101   b ,  101   c ,  101   d  are illustrated in  FIGS. 1 and 2  as the sectional views. The housing  101  indicates the entirety of these six outer plates  101   a  to  101   d  and a not-shown member coupling these plates. 
     The outer plates  101   a ,  101   b  of the housing  101  are members extending in a longitudinal direction, and extend in an upper-to-lower direction in  FIGS. 1 and 2 . In other words, the control device  100  is attached to the side surface (the attachment surface  23 ) of the base  2  of the vacuum pump  1  such that the longitudinal direction of the outer plate  101   b  is coincident with a rotation axis of the motor  4 , i.e., the rotation axis AX of the shaft  5 . Thus, the outer plate  101   a  facing to the outer plate  101   b  faces the outside of the vacuum pump, and extends in the direction of the rotation axis AX. 
     The control device  100  is attached to the pump device  10  in such a manner that a lower portion of the outer plate  101   b  of the housing  101  is attached to the attachment surface  23  of the base  2  with bolts. A not-shown power application connector is placed at part of a portion between the outer plate  101   b  and the attachment surface  23 , and therefore, a control signal or drive power from the control device  100  is transmitted to, e.g., the motor  4  in the pump device  10 . 
     The circuit board  102  is, by screwing etc., fixed to the outer plate  101   a  on the opposite side of the outer plate  101   b  via a support rod  104 . On each surface of the circuit board  102 , printed wiring is formed, and various types of electronic components are mounted. Note that elements (these elements will be hereinafter also collectively referred to as “heat generation elements  103 ”) with a great heat generation amount upon operation, such as an inverter element  103   a  configured to output a PWM drive signal to the motor  4 , a driver element  103   b  configured to drive the inverter element  103   a , and a backflow prevention diode element  103   c , are arranged on a surface of the circuit board  102  opposite to the outer plate  101   b . These heat generation elements directly contact the metal outer plate  101   a  opposite to the outer plate  101   b  of the housing  101 . The phrasing “directly contact” means that the heat generation elements  103  are connected to the outer plate  101   a  without the circuit board  102 . Preferably, the heat generation elements  103  directly contact the outer plate  101   a  via a high thermal conductive heat transfer sheet  106 . 
     The heat generation elements  103  are connected to the outer plate  101   a  of the housing  101  with low thermal resistance. Accordingly, heat generated at the heat generation elements  103  is transmitted to the metal outer plate  101   a  with a high efficiency, and is released from the outer plate  101   a . On the other hand, neither of the circuit board  102  nor the heat generation elements  103  is connected to the outer plate  101   b  connected to the base  2 . This can prevent or suppress the heat from the heat generation elements  103  from transmitting to the base  2  via the outer plate  101   b . Thus, an increase in the temperature of the ball bearing  8  in the pump device  10  can be prevented, and evaporation of the grease can be prevented or reduced. 
     On the other hand, elements with a relatively small heat generation amount upon operation, such as a CPU  105   a , a control IC  105   b , and a storage element  105   c , do not need to be cooled much with a high efficiency. Thus, as in  FIG. 2 , these elements may be arranged on an outer plate  101   b  side of the circuit board  102 . Heat generated at these elements is transmitted to the outer plate  101   a  by way of the circuit board  102  and the support rod  104 , and then, is released from the outer plate  101   a.    
     Note that for promoting heat release via the circuit board  102 , the circuit board  102  may contact, with low thermal resistance, the upper outer plate  101   c , the lower outer plate  101   d , or a not-shown near-side or far-side outer plate of the control device  100  via a low thermal resistor (a high thermal conductor) such as a graphite sheet. 
     Connection among the heat generation elements  103  and the outer plate  101   a  is not limited to contact via the heat transfer sheet  106 , and can be also low thermal resistance connection via a low thermal resistor (a high thermal conductor) such as a graphite sheet. 
     The outer plates for contact of the heat generation elements with low thermal resistance are not limited to above, and contact with any outer plate of the housing  101  may be made as long as the outer plate is other outer plates than the outer plate  101   b  contacting the base  2 . Note that contact with the outer plate far from the outer plate  101   b  as much as possible is preferable considering thermal conductivity by the housing  101  itself. 
     In arrangement of each heat generation element  103  on the circuit board  102 , the element with the greatest heat generation amount preferably contacts the outer plate at a position far from a contact portion between the outer plate  101   b  and the base  2  as much as possible. Thus, in the present example, the inverter element  103   a  as the element with the greatest heat generation amount among the heat generation elements  103  contacts an upper portion of the outer plate  101   a  at a position farthest from the lower portion of the outer plate  101   b  contacting the base  2  among the outer plates of the housing  101 . 
     A portion of a side surface of the pump case  12  of the pump device  10  facing the control device  100  is a flat surface  25 . With a clearance between the flat surface  25  and the control device  100 , thermal conduction from the inverter element  103   a  to the pump device  10  is further reduced. 
     In description above, the control device  100  includes the single circuit board  102 , but may include two or more circuit boards  102 . In this case, the heat generation elements  103  are arranged on the opposite side of the outer plate  101   b  on the circuit board  102  far from the outer plate  101   b  contacting the base  2 , and are connected to other outer plates (e.g., the outer plate  101   a ) than the outer plate  101   b  with low thermal resistance. 
     Note that the housing  101  may be configured such that the outer plates  101   a  to  101   d  are directly joined to each other, but may be configured such that the outer plates  101   a  to  101   d  may be joined via a high thermal resistive seal material such as rubber or a resin material. In the latter case, thermal conduction from the outer plate contacting the heat generation element to the outer plate  101   b  contacting the base  2  can be further reduced. 
     In  FIG. 1 , the control device  100  is arranged on the opposite side of a pump main body from the exhaust port  22 , but a positional relationship between the control device  100  and the exhaust port  22  is not limited to above. For example, the control device  100  and the exhaust port  22  may be at positions apart from each other at 90 degrees about the axial center (the rotation axis AX) of the pump device  10 , or may be arranged at other optional positions as long as the control device  100  and the exhaust port  22  do not mechanically overlap with each other. 
     Moreover, the present invention is not limited to the vacuum pump including, as the exhaust functional portions, the turbo pump portion and the Holweck pump portion, and may be also applied to a vacuum pump including only turbine blades, a vacuum pump including only a drag pump such as a Siegbahn pump or a Holweck pump, or a vacuum pump with a combination thereof. 
     Advantageous Effects of First Embodiment 
     The vacuum pump  1  of the first embodiment of the present invention includes the pump device  10  configured to rotate the rotor  3  at high speed about the rotation axis AX supported by the ball bearing  8 , and the control device  100  configured to control operation of the pump device  10 . The heat generation elements  103  in the control device  100  directly contact the outer plate  101   a  of the housing  101  of the control device  100  not contacting the pump device  10 . The heat generation elements  103  do not contact the outer plate  101   b  contacting the pump device  10 . 
     With this configuration, the heat generated at the heat generation elements  103  is transmitted to the outer plate  101   a  with a high efficiency, and then, is released from the outer plate  101   a . This provides the effect of preventing or suppressing the heat from the heat generation elements from transmitting to the base  2  via the outer plate  101   b  and preventing or suppressing an increase in the temperature of the ball bearing  8  in the pump device  10 . As a result, lowering of the degree of vacuum of a vacuum device due to heating and evaporation of the grease of the ball bearing can be prevented or suppressed. Further, a decrease in the grease can be prevented or suppressed. Consequently, the life of the ball bearing and therefore the life (the maintenance cycle) of the vacuum pump can be extended. 
     Note that in the above-described first embodiment, the longitudinal direction of the outer plates  101   a ,  101   b  of the housing  101  extends in the direction of the rotation axis AX of the shaft  5 , i.e., the upper-to-lower direction in  FIGS. 1 and 2 , but the shape of the housing  101  is not limited to above. 
     Note that the shape of the vacuum pump  1  is generally elongated in the direction along the rotation axis AX. Thus, when the housing  101  extends in the direction of the rotation axis AX, the effect of expanding the area of the outer plate  101   a  without an increase in the size of the entirety of the vacuum pump  1  and releasing the heat from the heat generation elements  103  with a higher efficiency can be provided. 
     (First Variation) 
     Although not described above in the first embodiment, a heat insulating member  107  made of, e.g., rubber or a resin material can be also provided between the outer plate  101   b  of the housing  101  and the attachment surface  23  of the base  2  as illustrated in  FIG. 2 . 
     (Advantageous Effects of First Variation) 
     In this case, the housing  101  contacts the pump device  10  via the heat insulating member, and therefore, the effect of further reducing thermal conduction from the heat generation elements in the control device  100  to the pump device  10  is provided. 
     Second Embodiment 
     Hereinafter, a second embodiment of the present invention will be described with reference to  FIG. 3 .  FIG. 3  is a sectional view of a vacuum pump of the second embodiment of the present invention. Note that elements with the same reference numerals as those of  FIG. 1  are common to those of the first embodiment, and therefore, description thereof will be omitted. 
     In the second embodiment, a control device  100 A is arranged in a recessed portion  26  formed in such a manner that part of the periphery of a lower portion of a base  2 A at a side surface of a pump device  10 A along the direction of a rotation axis AX is cut out. That is, the arrangement position of the control device  100 A is the same as that in a vacuum pump disclosed in JP-A-2014-105695. 
     A boundary of the recessed portion  26  includes a recessed portion bottom surface  26   a  parallel with a pump bottom surface and a suction port flange surface, and a recessed portion side surface  26   b  perpendicular to the recessed portion bottom surface  26   a.    
     In the present embodiment, the outer shape of the control device  100 A, i.e., the outer shape of a housing  1012 , is a substantially rectangular parallelepiped shape. Of six outer plates forming such a rectangular parallelepiped shape, the sections of four outer plates  101   e ,  101   f ,  101   g ,  101   h  are illustrated in  FIG. 3  as the sectional view. The housing  1012  indicates the entirety of these six outer plates  101   e  to  101   h  and a not-shown member coupling these plates. 
     The control device  100 A is attached to the pump device  10 A in such a manner that an upper portion of the outer plate  101   g  and an outer portion of the outer plate  101   f  in the housing  1012  are each attached to the recessed portion bottom surface  26   a  and the recessed portion side surface  26   b  of the recessed portion  26  of the base  2 A with bolts. Moreover, a not-shown power application connector is placed at part of a portion between the outer plate  101   f  and the recessed portion side surface  26   b , and therefore, a control signal or drive power from the control device  100 A is transmitted to, e.g., a motor  4  in the pump device  10 A. 
     A circuit board  102 A is fixed to the outer plate  101   e  not contacting the pump device  10 A by screwing etc. via a support rod  104 A, the outer plate  101   e  being different from the outer plate  101   g  and the outer plate  101   f  contacting the base  2 A. In the present example, heat generation elements  103  such as an inverter element  103   a  and a driver element  103   b  are also arranged on an outer plate  101   e  side of the circuit board  102 A. Moreover, these heat generation elements  103  contacts the metal outer plate  101   e  via a not-shown high thermal conductive heat transfer sheet. 
     On the other hand, elements with relatively small heat generation upon operation, such as a CPU  105   a  and a control IC  105   b , do not need to be cooled much with a high efficiency, and for this reason, may be arranged on an outer plate  101   g  side of the circuit board  102 A. Heat generated at these elements is transmitted to the outer plate  101   e  by way of the circuit board  102 A and the support rod  104 A, and then, is released from the outer plate  101   e.    
     As in the above-described first embodiment, for further promoting heat release, the circuit board  102 A may contact, with low thermal resistance, the left outer plate  101   h  of the control device  100 A as viewed in the figure or a not-shown near-side or far-side outer plate of the control device  100 A via a low thermal resistor. 
     Moreover, the heat generation elements  103  may contact the outer plate  101   h  with low thermal resistance via a low thermal resistor (a high thermal conductor) such as a graphite sheet. 
     In the present example, the inverter element  103   a  as the element with the greatest heat generation amount contacts a left (a side far from the base  2 A) portion of the outer plate  101   e  as viewed in  FIG. 3  at a position farthest from a portion contacting the base  2 A among the outer plates of the housing  101 Z. 
     Advantageous Effects of Second Embodiment 
     As in the above-described first embodiment, a vacuum pump  1 A of the second embodiment as described above includes the pump device  10 A configured to rotate a rotor  3  at high speed about the rotation axis AX supported by a ball bearing  8 , and the control device  100 A configured to control operation of the pump device  10 A. The heat generation elements  103  in the control device  100 A is, with low thermal resistance, connected to the outer plate  101   e  of the housing  101 Z of the control device  100 A not contacting the pump device  10 A. 
     With this configuration, the heat generated at the heat generation elements  103  is transmitted to the outer plate  101   e  with a high efficiency, and then, is released from the outer plate  101   e . This provides the effect of preventing the heat from the heat generation elements  103  from transmitting to the base  2 A via the outer plates  101   g ,  101   f  and preventing an increase in the temperature of the ball bearing  8  in the pump device  10 A. 
     Third Embodiment 
     A third embodiment will be described with reference to  FIGS. 4 and 5 .  FIG. 4  is a perspective view of a vacuum pump  1 B of the third embodiment when the vacuum pump  1 B is viewed diagonally from below. 
     A connector  120  provided at a control device  100  is a connector configured to connect, e.g., an electric wire for supplying power to a cooling fan. 
     In the present embodiment, a cooling fan  42  is basically provided on a side surface of a vacuum pump device  10 B opposite to the control device  100  in the vacuum pump  1  of the above-described first embodiment. 
     Note that as illustrated in  FIG. 4 , a flat surface  40  and a flat surface  41  for attachment of the cooling fan  42  are each formed at side surfaces of a base  2 B and a pump case  12 B in the vacuum pump device  10 B of the present embodiment. 
     The cooling fan  42  is, with bolts  43 , fixed to the flat surfaces  40 ,  41  via support rods  44  for forming a clearance allowing passage of wind from the cooling fan  42 . Hereinafter, a cooling path of cooling wind blowing from the cooling fan  42  will be described with reference to  FIG. 5 . 
       FIG. 5  is a plan view when the vacuum pump  1 B of  FIG. 4  is viewed from below. Cooling wind  50  having blown from the cooling fan  42  blows to both sides (the upper and lower sides in  FIG. 5 ) of the base  2 B through the clearance formed between the cooling fan  42  and the base  2 B by the support rods  44 . 
     The cooling wind  50  flows along the side surface of the base  2 B to cool the base  2 B. Then, in association with cooling of the base  2 B, a ball bearing  8  provided in the base  2 B is also cooled. 
     Thereafter, the cooling wind  50  flows along the side surface of the base  2 B, and the cooling wind flowing on the upper side of the base  2 B in  FIG. 5  branches into the far and near sides in the plane of paper of  FIG. 5  to pass through an exhaust port  22 . Then, the cooling wind  50  reaches the control device  100  arranged on the opposite side of the base  2 B from the cooling fan  42 , thereby cooling outer plates  101   i ,  101   j  at side surfaces of a housing  101  of the control device  100 . 
     Thus, in the present embodiment, heat generation elements  103  in the control device  100  are, with low thermal resistance, connected to the outer plate  101   i ,  101   j  at the side surfaces, and therefore, the effect of cooling the heat generation elements  103  can be further enhanced. 
     Note that the cooling wind  50  forms eddies  51  after having passed through the control device  100 , and therefore, an outer plate  101   a  on the side of the housing  101  opposite to the base  2 B is also cooled by the eddies  51 . Thus, the heat generation elements  103  may be, with low thermal resistance, connected to the outer plate  101   a.    
     Note that a radiation fin extending in a circumferential direction, i.e., formed parallel with a flow path of the cooling wind  50 , may be formed on an outer peripheral surface of the base  2 B to further improve a cooling efficiency. 
     Alternatively, radiation fins formed parallel with the flow path of the cooling wind  50  may be also formed on the outer plates  101   i ,  101   j  at the side surfaces of the housing  101  to further improve the cooling efficiency. 
     Note that part of a clearance between the cooling fan  42  and the base  2 B may be covered with, e.g., a metal wind shielding plate. In this manner, a blowing direction of the cooling wind  50  from the cooling fan  42  can be limited, and the base  2 B and the control device  100  can be much more efficiently cooled. 
     For example, a clearance (a lower clearance in  FIG. 4 ) near a lower portion of the base  2 B is covered so that the cooling wind  50  can be concentrated toward a peripheral surface of the base  2 B, the control device  100 , and the flat surface  41  of the pump case  12 B. Further, an upper clearance in  FIG. 4  is also covered so that the cooling wind can be concentrated toward the peripheral surface of the base  2 B and the control device  100 . 
     Advantageous Effects of Third Embodiment 
     As described above, the vacuum pump of the third embodiment is placed on an outer surface of the pump device  10 B, and has the cooling fan  42  configured to cool the vacuum pump device  10 B. 
     With such a configuration, the effect of efficiently cooling the vacuum pump device  10 B and preventing an increase in the temperature of the ball bearing  8  in the vacuum pump device  10 B is provided. 
     Moreover, it is configured such that the control device  100  is placed on the cooling path of the cooling wind  50  from the cooling fan  42 , and therefore, the effect of cooling the control device  100  by the cooling fan  42  is provided. 
     Further, it is configured such that the cooling fan  42  is placed on the side of the vacuum pump device  10 B opposite to the control device  100  with respect to the axial center of the vacuum pump device  10 B, i.e., a rotation axis AX of a rotor  3 . This provides the effect of cooling the control device  100  by means of both of the cooling paths of the cooling wind  50  divided in half by the vacuum pump device  10 B. 
     Fourth Embodiment 
     A fourth embodiment will be described with reference to  FIG. 6 .  FIG. 6  is a perspective view of a vacuum pump  1 C of the fourth embodiment when the vacuum pump  1 C is viewed diagonally from below. 
     As in the above-described third embodiment illustrated in  FIG. 4 , a cooling fan  42  is basically provided at the vacuum pump  1  of the first embodiment in the present embodiment. Thus, the same reference numerals are used to represent common elements, and description thereof will be omitted. 
     Unlike the third embodiment, the cooling fan  42  is placed on a lower side of a base  2 C of the vacuum pump  1 C. 
     As described above, a base cover  27  configured to seal an opening  24  for attachment/detachment of a ball bearing  8  is present on the lower side (a bottom surface) of the base  2 C, and for this reason, it is difficult to directly attach the cooling fan  42  to such a portion. Thus, the cooling fan  42  is, with bolts  43  and nuts  45 , attached to an attachment seat  46  formed by deformation of a metal plate into a substantially L-shape, and the attachment seat  46  is attached to a flat surface  40  of a side surface of the base  2 C with bolts  47 . 
     Advantageous Effects of Fourth Embodiment 
     As described above, the vacuum pump of the fourth embodiment is placed on an outer surface of a pump device  10 C, and has the cooling fan  42  configured to cool the pump device  10 C. 
     With this configuration, the effect of efficiently cooling the pump device  10 C and preventing an increase in the temperature of the ball bearing  8  in the pump device  10 C is provided. 
     (Second Variation) 
     In the above-described third and fourth embodiments, the air cooling type cooling fan  42  is used for cooling the pump device  10  and the control device  100  of the first embodiment, but instead or in addition, a liquid cooling type cooling mechanism is provided. That is, a pipe is placed inside or at the periphery of the base  2  or the pump case  12  of the pump device  10 , and cooling is performed by a coolant flow. 
     Further, a cooling pipe may be also provided at the periphery of the control device  100 . In this case, the cooling pipe is preferably intensively placed on other outer plates than the outer plate connected to the heat generation elements  103  with low thermal resistance, i.e., the outer plate contacting the pump device  10 , among the outer plates of the control device  100 , and in this manner, the heat generation elements  103  are efficiently cooled. 
     (Advantageous Effects of Second Variation) 
     In the present variation, the liquid cooling type cooling mechanism configured to cool the pump device  10  is provided, and therefore, the effect of cooling the pump device  10  and the ball bearing  8  with higher cooling performance is provided. 
     Various embodiments and the variations have been described above, but the present invention is not limited to these contents. Moreover, the embodiments and the variations may be applied alone or in combination. Other aspects conceivable within the scope of the technical idea of the present invention are also included in the scope of the present invention.