Patent Publication Number: US-2020284310-A1

Title: Speed reducer, rotary drive system, and hydraulic shovel

Description:
TECHNICAL FIELD 
     The present invention relates to a speed reducer, a rotary drive system, and a hydraulic shovel. 
     Priority is claimed on Japanese Patent Application No. 2018-035843, filed on Feb. 28, 2018, the content of which is incorporated herein by reference. 
     BACKGROUND ART 
     PTL 1 describes a rotary drive system in which an electric motor and a speed reducer decelerating the rotation of the electric motor are integrally provided. The speed reducer has multi-stage planetary gear mechanisms vertically disposed as a transmission unit. The planetary gear mechanisms are immersed in lubricating oil. 
     CITATION LIST 
     Patent Literature 
     [PTL 1] Japanese Unexamined Patent Application, First Publication No. 2016-172965 
     DISCLOSURE OF INVENTION 
     Technical Problem 
     By the way, for a reduction in stirring loss during rotary drive, at least part of the transmission unit of the speed reducer may be, for example, exposed from the lubricating oil without being immersed in the lubricating oil. Even in such a case, it is required to smoothly supply lubricating oil to a sliding portion of the speed reducer that requires lubrication. 
     The present invention has been made in view of such problems, and an object of the present invention is to provide a speed reducer, a rotary drive system, and a hydraulic shovel allowing lubricating oil to be smoothly supplied to a sliding portion. 
     Solution to Problem 
     A speed reducer according to an aspect of the present invention includes: an output shaft provided below a rotary shaft that has an axis extending vertically and rotates around the axis, and provided to be rotatable around the axis; a transmission unit interconnecting a lower portion of the rotary shaft and the output shaft, decelerating a rotation of the rotary shaft, and transmitting a decelerated rotation of the rotary shaft to the output shaft; an annular member having a cylindrical shape surrounding the axis and rotating around the axis together with the transmission unit, the annular member including an oil sump having a recessed groove recessed in an inner peripheral surface of the annular member and a lubricating oil supply hole extending radially outward from the recessed groove and being opened; and a sliding portion provided on an outer side of the lubricating oil supply hole of the annular member in a radial direction of the axis. 
     According to the speed reducer configured as described above, the lubricating oil that has reached the inner peripheral surface of the annular member by being supplied from above is temporarily collected in the oil sump and then flows through the lubricating oil supply hole radially outward and in accordance with a centrifugal force. Then, the lubricating oil discharged from the lubricating oil supply hole is supplied to the sliding portion on the radially outer side of the lubricating oil supply hole. As a result, lubricity can be ensured for the sliding portion. 
     Advantageous Effects of Invention 
     According to the speed reducer, the rotary drive system, and the hydraulic shovel of the above aspect, it is possible to smoothly supply lubricating oil to a sliding portion. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a side view of a hydraulic shovel including a rotary drive system according to a first embodiment of the present invention. 
         FIG. 2  is a plan view of the hydraulic shovel including the rotary drive system according to the first embodiment of the present invention. 
         FIG. 3  is a schematic diagram showing the outline of the rotary drive system according to the first embodiment of the present invention. 
         FIG. 4  is a longitudinal cross-sectional view of a rotary drive device in the rotary drive system according to the first embodiment of the present invention. 
         FIG. 5  is a partially enlarged view of  FIG. 4 . 
         FIG. 6  is an enlarged view of a longitudinal cross section of the rotary drive system according to the embodiment of the present invention that is at a position different from  FIG. 5 . 
         FIG. 7  is an enlarged view of the vicinity of a brake disk and a brake plate of  FIG. 4 . 
     
    
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
     First Embodiment 
     Hereinafter, a first embodiment of the present invention will be described in detail with reference to  FIGS. 1 to 7 . 
     Work Machine 
     As shown in  FIGS. 1 and 2 , a hydraulic shovel  200  as a work machine includes an undercarriage  210 , a swing circle  220 , and an upper swing body  230 . In the following description, the direction in which gravity acts in a state where the work machine is installed on a horizontal surface will be referred to as “vertical direction”. 
     In addition, the front of the driver&#39;s seat in a cab  231  (described later) will be simply referred to as “front” and the rear of the driver&#39;s seat will be simply referred to as “rear”. 
     The undercarriage  210  includes a pair of left and right crawlers  211  and  211  and the hydraulic shovel  200  travels by the crawlers  211  and  211  being driven by a traveling hydraulic motor (not shown). 
     The swing circle  220  is a member interconnecting the undercarriage  210  and the upper swing body  230  and includes an outer race  221 , an inner race  222 , and a swing pinion  223 . The outer race  221  is supported by the undercarriage  210  and has an annular shape about a swing axis L extending so as to match the vertical direction. The inner race  222  is an annular member coaxial with the outer race  221  and is disposed inside the outer race  221 . The inner race  222  is supported so as to be rotatable relative to the outer race  221  around the swing axis L. The swing pinion  223  meshes with the internal teeth of the inner race  222  and the inner race  222  rotates relative to the outer race  221  by the swing pinion  223  rotating. 
     The upper swing body  230  is disposed so as to be capable of swinging around the swing axis L with respect to the undercarriage  210  by being supported by the inner race  222 . The upper swing body  230  includes the cab  231 , a work equipment  232 , an engine  236  provided behind the cab  231  and the work equipment  232 , a generator motor  237 , a hydraulic pump  238 , an inverter  239 , a capacitor  240 , and a rotary drive system  1 . 
     The cab  231  is disposed on the front left side of the upper swing body  230  and is provided with the driver&#39;s seat for a worker. The work equipment  232  is provided so as to extend in front of the upper swing body  230  and includes a boom  233 , an arm  234 , and a bucket  235 . The work equipment  232  performs various works such as excavation by the boom  233 , the arm  234 , and the bucket  235  being respectively driven by hydraulic cylinders (not shown). 
     The shafts of the engine  236  and the generator motor  237  are spline-coupled. The generator motor  237  generates electric power by being driven by the engine  236 . The rotary shafts of the generator motor  237  and the hydraulic pump  238  are spline-coupled. The hydraulic pump  238  is driven by the engine  236 . Each of the hydraulic cylinders and the traveling hydraulic motor described above are driven by the hydraulic pressure that is generated by the hydraulic pump  238  being driven. 
     The generator motor  237 , the capacitor  240 , and the rotary drive system  1  are electrically interconnected via the inverter  239 . Another electric power storage device such as a lithium-ion battery may be used instead of the capacitor  240 . The output of the rotary drive system  1  is transmitted to the swing pinion  223  meshing with the internal teeth of the inner race  222 . 
     The rotary drive system  1  is disposed such that an axis O as a rotation center extends in the vertical direction. Here, “extends in the vertical direction” means that the direction of the axis O extends in a direction including an upward and downward directions, that is, includes a case where the axis O is inclined with respect to the direction that matches the vertical direction. 
     The hydraulic shovel  200  drives the rotary drive system  1  with the electric power generated by the generator motor  237  or the electric power from the capacitor  240 . The drive force of the rotary drive system  1  is transmitted to the inner race  222  via the swing pinion  223 . As a result, the upper swing body  230  swings by the inner race  222  rotating relative to the outer race  221 . 
     When the swinging of the upper swing body  230  is decelerated, the rotary drive system  1  generates electric power as regenerative energy by functioning as a generator. This electric power is accumulated in the capacitor  240  via the inverter  239 . The electric power accumulated in the capacitor  240  is supplied to the generator motor  237  when the engine  236  is accelerated. The generator motor  237  assists the output of the engine  236  by the generator motor  237  being driven by the electric power of the capacitor. 
     Rotary Drive System 
     As shown in  FIG. 3 , the rotary drive system  1  includes a rotary drive device  10  and a lubricating oil circulation unit  150 . 
     Rotary Drive Device 
     As shown in  FIGS. 3 and 4 , the rotary drive device  10  includes an electric motor  20  and a speed reducer  60  provided integrally with the electric motor  20 . The speed reducer  60  is installed below the electric motor  20 . 
     Electric Motor 
     As shown in  FIGS. 3 and 4 , the electric motor  20  includes an electric motor casing  21 , a stator  30 , and a rotor  38 . 
     Electric Motor Casing 
     As shown in  FIG. 4 , the electric motor casing  21  is a member forming the outer shape of the electric motor  20 . The electric motor casing  21  includes an upper casing  22  and a lower casing  25 . 
     The upper casing  22  has a bottomed cylindrical shape having an upper cylindrical portion  23  having a cylindrical shape and extending in the vertical direction and an upper bottom portion  24  blocking the upper part of the upper cylindrical portion  23 . 
     The lower casing  25  has a bottomed cylindrical shape having a lower cylindrical portion  26  having a cylindrical shape and extending in the vertical direction and a lower bottom portion  27  blocking the lower part of the lower cylindrical portion  26 . 
     The lower bottom portion  27  serves as the bottom portion of the electric motor casing  21 . Specifically, as shown in  FIGS. 5 and 6 , the lower bottom portion  27  has a lower through hole  27   a  penetrating the lower bottom portion  27  about the axis O. The part that is around the lower through hole  27   a  on the surface of the lower bottom portion  27  facing upward is an annular first bottom surface  27   b  having a flat shape orthogonal to the axis O. On the outer peripheral side of the first bottom surface  27   b  of the lower bottom portion  27 , a plurality of second bottom surfaces  27   c  (see  FIG. 5 ) formed one step higher than the first bottom surface  27   b  arc formed at intervals in the circumferential direction. Part of the first bottom surface  27   b  is disposed between the second bottom surfaces  27   c  that are adjacent to each other in the circumferential direction. The first bottom surface  27   b  and the second bottom surface  27   c  are interconnected by a stepped portion  27   d  extending in the vertical direction. The outer peripheral side end portion of the second bottom surface  27   c  is connected to the inner peripheral surface of the lower cylindrical portion  26 . 
     As shown in  FIG. 4 , the outer peripheral surface of the lower cylindrical portion  26  is fitted to the inner peripheral surface of the upper cylindrical portion  23  in such a manner that the lower cylindrical portion  26  is inserted into the upper cylindrical portion  23  from below. As a result, the lower cylindrical portion  26  and the upper cylindrical portion  23  are integrally fixed to each other. The space inside the electric motor casing  21  that is formed by the lower cylindrical portion  26  and the upper cylindrical portion  23  is an upper accommodation space R 1 . 
     Communication Hole 
     Here, as shown in  FIGS. 5 and 6 , the electric motor casing  21  has a communication hole  50  allowing the upper accommodation space R 1  in the electric motor casing  21  to communicate downward. In the present embodiment, the communication hole  50  includes an inner peripheral-side communication hole  51  and an outer peripheral-side communication hole  52 . 
     The inner peripheral-side communication hole  51  is formed so as to open in the first bottom surface  27   b  in the lower bottom portion  27  of the lower casing  25  and vertically penetrates the lower bottom portion  27 . A plurality of the communication holes  50  arc formed at intervals in the circumferential direction. 
     As shown in  FIG. 6 , the outer peripheral-side communication hole  52  is formed so as to vertically penetrate the lower cylindrical portion  26  of the lower casing  25 . The opening of the lower surface of the lower casing  25  of the outer peripheral-side communication hole  52 , that is, the opening of a lower surface  21   a  of the electric motor casing  21  is formed so as to expand radially inward. 
     Stator 
     As shown in  FIG. 4 , the stator  30  includes a stator core  31  and a coil  32 . 
     The stator core  31  is configured by a plurality of electromagnetic steel plates being stacked in the vertical direction and has a cylindrical shape about the axis O. The stator core  31  includes a yoke and a plurality of teeth formed at intervals in the circumferential direction of the yoke so as to protrude from the inner peripheral surface of the yoke. The stator core is fixed to the electric motor casing  21 . 
     A plurality of the coils  32  are provided so as to correspond to the respective teeth and wound around the respective teeth. As a result, the plurality of coils  32  are provided at intervals in the circumferential direction. 
     Rotor 
     As shown in  FIG. 4 , the rotor  38  includes a rotary shaft  40 , a rotor core  42 , a lower end plate  45 , and an upper end plate  46 . 
     Rotary Shaft 
     The rotary shaft  40  is a rod-shaped member extending along the axis O. The rotary shaft  40  is disposed in the electric motor casing  21  so as to penetrate the inside of the stator  30  in the vertical direction. The upper end of the rotary shaft  40  protrudes above the upper bottom portion  24  in the upper casing  22 . In addition, the upper end of the rotary shaft  40  may be accommodated in the electric motor casing  21 . 
     The upper bottom portion  24  is provided with an upper seal  35  for sealing between the upper bottom portion  24  and the outer peripheral surface of the rotary shaft  40 . As a result, liquid tightness is ensured at the upper end inside the electric motor casing  21 . 
     Rotor Core 
     The rotor core  42  has a cylindrical shape about the axis O and an inner peripheral surface  42   a  is externally fitted on the outer peripheral surface of the rotary shaft  40 . The rotor core  42  is configured by a plurality of electromagnetic steel plates being stacked in the vertical direction. In the rotor core  42 , a plurality of permanent magnets (not shown) are embedded at intervals in the circumferential direction. 
     Lower End Plate 
     The lower end plate  45  is fixed so as to be stacked on the rotor core  42  from below the rotor core  42 . 
     Upper End Plate 
     The upper end plate  46  is fixed so as to be stacked on the rotor core  42  from above the rotor core  42 . 
     Intra-rotor Flow Path F 
     The rotor  38  has an intra-rotor flow path F extending downward from the upper end of the rotary shaft  40  and passing between the rotary shaft  40  and the rotor core  42 , through the lower end plate  45 , through the rotor core  42 , and through the upper end plate  46 . The intra-rotor flow path F is open from the upper surface of the upper end plate  46  into the upper accommodation space RI. 
     Upper Bearing 
     The upper bottom portion  24  is provided with an upper bearing  36  having an annular shape about the axis O. The rotary shaft  40  is vertically inserted through the upper bearing  36  and the upper portion of the rotary shaft  40  is supported by the upper bearing  36  so as to be rotatable around the axis O. 
     Lower Bearing 
     As shown in  FIGS. 5 and 6 , the lower through hole  27   a  in the lower bottom portion  27  is provided with a lower bearing  37  having an annular shape about the axis O. The rotary shaft  40  is vertically inserted through the lower bearing  37  and the lower portion of the rotary shaft  40  is supported by the lower bearing  37  so as to be rotatable around the axis O. The upper surface of the lower bearing  37  has the same height as the first bottom surface  27   b.  Lubricating oil introduced into the lower bearing  37  passes through the lower bearing  37  and falls downward. 
     Speed Reducer 
     Next, the speed reducer  60  will be described with reference to  FIG. 4 . The speed reducer  60  includes a speed reducer casing  61 , an output shaft  70 , a transmission unit  80 , an annular member  170 , and a brake mechanism  120 . 
     Speed Reducer Casing 
     The speed reducer casing  61  has a cylindrical shape extending along the axis O and open upward and downward. The upper end of the speed reducer casing  61  abuts the electric motor casing  21  from below. The upper opening of the speed reducer casing  61  is blocked by the lower casing  25  of the electric motor casing  21 . 
     Output Shaft 
     The output shaft  70  has a rod shape extending along the axis O. The rotation of the output shaft  70  becomes the output of the rotary drive system  1 . The upper portion of the output shaft  70  is disposed in the speed reducer casing  61  and the lower portion of the output shaft  70  protrudes downward from the speed reducer casing  61 . An output shaft bearing  71  supporting the output shaft  70  so as to be rotatable around the axis O is provided below the inner peripheral surface of the speed reducer casing  61 . The lower portion of the output shaft  70  that protrudes downward from the speed reducer casing  61  is connected to the swing pinion  223 . 
     A lower seal  72  sealing the annular space between the inner peripheral surface of the speed reducer casing  61  and the outer peripheral surface of the output shaft  70  is provided further below the output shaft bearing  71  on the inner peripheral surface of the speed reducer casing  61 . The space in the speed reducer casing  61  that is blocked from below by the lower seal  72  is a lower accommodation space R 2 . The lower portion of the rotary shaft  40  that protrudes downward from the electric motor casing  21  is positioned above the lower accommodation space R 2 . Lubricating oil is stored up to a predetermined height position in the lower accommodation space R 2 . In other words, the lower accommodation space R 2  functions as a lubricating oil storage tank. 
     Transmission Unit 
     The transmission unit  80  is provided in the lower accommodation space R 2  in the speed reducer casing  61 . The transmission unit  80  has a role of reducing the rotational speed of the rotary shaft  40  and transmitting the reduced rotational speed to the output shaft  70 . 
     The transmission unit  80  includes multi-stage planetary gear mechanisms sequentially reducing the rotational speed from the rotary shaft  40  to the output shaft  70 . In the present embodiment, the three planetary gear mechanisms of a first stage planetary gear mechanism  90 , a second stage planetary gear mechanism  100 , and a third stage planetary gear mechanism  110  are provided as the plurality of planetary gear mechanisms. 
     First Stage Planetary Gear Mechanism 
     The first stage planetary gear mechanism  90  is a planetary gear mechanism disposed at a first stage. The first stage planetary gear mechanism  90  includes a first stage transmission shaft (transmission shaft)  91 , a first stage planetary gear (planetary gear)  92 , and a first stage carrier (carrier)  93 . 
     The first stage transmission shaft  91  is externally fitted from the lower end to the lower portion of the rotary shaft  40 . The first stage transmission shaft  91  is rotatable around the axis O integrally with the rotary shaft  40 . 
     More specifically, as shown in  FIGS. 5 and 6 , the first stage transmission shaft  91  includes a cylindrical portion  91   a  and a flange portion  91   c.  The cylindrical portion  91   a  has a bottomed cylindrical shape extending about the axis and blocked at the lower end. The inner peripheral surface of the cylindrical portion  91   a  is spline-coupled to the outer peripheral surface of the lower portion of the rotary shaft  40 . In addition, the inner peripheral surface of the cylindrical portion  91   a  and the outer peripheral surface of the lower portion of the rotary shaft  40  may form another connection structure. An upper end  91   b  of the cylindrical portion  91   a  has a reverse taper shape inclined downward from the radially outer side to the inner side. In other words, the upper end  91   b  of the cylindrical portion  91   a  decreases in diameter downward. 
     The flange portion  91   c  is formed so as to overhang radially outward from the lower end of the cylindrical portion  91   a.  Sun gear teeth  91   d  as outer gear teeth are formed on the outer peripheral surface of the flange portion  91   c.    
     The first stage planetary gear  92  has planetary gear teeth  92   a  on the outer peripheral surface. A plurality of the first stage planetary gears  92  are provided at intervals in the circumferential direction around the first stage transmission shaft  91  such that the planetary gear teeth  92   a  mesh with the sun gear teeth  91   d  of the first stage transmission shaft  91 . The planetary gear teeth  92   a  of the first stage planetary gear  92  mesh with first stage inner gear teeth  62   a  formed on the inner peripheral surface of the speed reducer casing  61 . 
     The first stage carrier  93  supports the first stage planetary gear  92  so as to be capable of rotating and revolving around the axis O. The first stage carrier  93  includes a carrier shaft  161  and a carrier main body  167 . 
     The carrier shaft  161  is a vertically extending rod-shaped member and a plurality of the carrier shafts  161  arc provided so as to correspond to the respective first stage planetary gears  92 . The carrier shaft  161  penetrates the center of each first stage planetary gear  92  in the vertical direction and rotatably supports the first stage planetary gear  92 . The intermediate portion of the carrier shaft  161  in the vertical direction slides with the inner peripheral surface of the first stage planetary gear  92 . In other words, the outer peripheral surface of the intermediate portion of the carrier shaft  161  and the inner peripheral surface of the first stage planetary gear  92  are a sliding surface (sliding portion) S 1 . 
     An intra-shaft flow path  162  is formed in the carrier shaft  161 . The intra-shaft flow path  162  includes an upper radial flow path  163 , an intermediate radial flow path  164 , and an axial flow path  165 . 
     The upper radial flow path  163  is a flow path extending along the radial direction of the axis O of the rotary shaft  40  in the upper portion of the carrier shaft  161 . The upper radial flow path  163  passes through the carrier shaft  161  in the radial direction of the axis O. The opening in the upper radial flow path  163  that is on the inner side of the radial direction of the axis O of the rotary shaft  40  is a first opening portion  162   a  of the intra-shaft flow path  162 . 
     The intermediate radial flow path  164  is a flow path extending along the radial direction of the axis O of the rotary shaft  40  in the middle portion of the carrier shaft  161 . The upper radial flow path  163  passes through the carrier shaft  161  in the radial direction of the axis O. Both ends of the intermediate radial flow path  164  are open in the sliding surface S 1  with respect to the first stage planetary gear  92 . The opening in the intermediate radial flow path  164  that is on the radially outer side with respect to the axis O with respect to the axis O of the rotary shaft  40  is a second opening portion  162   b  of the intra-shaft flow path  162 . 
     The axial flow path  165  is a flow path extending in the vertical direction at the center of the carrier shaft  161 . The upper end of the axial flow path  165  communicates with the upper radial flow path  163 . The lower end of the axial flow path  165  is blocked without opening on the lower surface of the carrier shaft  161 . The intermediate portion of the axial flow path  165  in the vertical direction communicates with the intermediate radial flow path  164 . 
     The carrier main body  167  has a disk shape about the axis O. The carrier main body  167  is disposed below each first stage planetary gear  92  so as to face the first stage planetary gear  92 . The carrier main body  167  has a lower fitting hole  167   a  into which the outer peripheral surface of the lower portion of the carrier shaft  161  is fitted. 
     Second Stage Planetary Gear Mechanism 
     As shown in  FIGS. 4 and 5 , the second stage planetary gear mechanism  100  includes a second stage transmission shaft  101 , a second stage planetary gear  102 , and a second stage carrier  103 . The second stage transmission shaft  101  is provided below the first stage transmission shaft  91  so as to be rotatable around the axis O and is connected to the carrier main body  167  in the first stage carrier  93 . The second stage planetary gear  102  meshes with sun gear teeth  101   a  formed on the second stage transmission shaft  101  and second stage inner gear teeth  62   b  formed on the inner peripheral surface of the speed reducer casing  61 . The second stage planetary gear  102  is supported by the second stage carrier  103  so as to be capable of rotating and revolving around the axis O. 
     Third Stage Planetary Gear Mechanism 
     The third stage planetary gear mechanism  110  includes a third stage transmission shaft  111 , a third stage planetary gear  112 , and a third stage carrier  113 . The third stage transmission shaft  111  is provided below the second stage transmission shaft  101  so as to be rotatable around the axis O and is connected to the second stage carrier  103 . The third stage planetary gear  112  meshes with sun gear teeth  111   a  formed on the third stage transmission shaft  111  and third stage inner gear teeth  62   c  formed on the inner peripheral surface of the speed reducer casing  61 . The third stage planetary gear  112  is supported by the third stage carrier  113  so as to be capable of rotating and revolving around the axis O. The third stage carrier  113  is connected to the output shaft  70 . 
     The transmission unit  80  transmits the rotation of the rotary shaft  40  to the output shaft  70  after decelerating the rotation of the rotary shaft  40  a plurality of times by means of the multi-stage planetary gear mechanisms. 
     Annular Member 
     As shown in  FIG. 5 , the annular member  170  has an annular shape about the axis O and is provided integrally with the first stage carrier  93  in the present embodiment. The annular member  170  includes an annular plate portion  171  and an annular cylindrical portion  172 . 
     The annular plate portion  171  has a disk shape about the axis O. The annular plate portion  171  is disposed above each first stage planetary gear  92  so as to face the first stage planetary gear  92 . The annular plate portion  171  has an upper fitting hole (fitting hole)  171   a  into which the outer peripheral surface of the upper portion of the carrier shaft  161  is fitted. By the carrier shaft  161  being fitted into the upper fitting hole  171   a,  the annular member  170  can be rotated around the axis O integrally with the first stage carrier  93 . 
     The annular cylindrical portion  172  is a cylindrical member about the axis O and has a lower end integrally fixed to the annular plate portion  171 . The annular cylindrical portion  172  has a shape in which the inner peripheral surface and the outer peripheral surface increase in diameter in stages upward. 
     The uppermost part of the outer peripheral surface of the annular cylindrical portion  172  is a disk support surface  172   a  forming a cylindrical surface about the axis O. 
     Oil Sump 
     An upper oil sump  175  and a lower oil sump  176  as oil sumps temporarily storing lubricating oil are formed in the inner peripheral surface of the annular cylindrical portion  172 . The upper oil sump  175  and the lower oil sump  176  are disposed at an interval in the vertical direction. The upper oil sump  175  is positioned above the lower oil sump  176 . 
     The upper oil sump  175  and the lower oil sump  176  have recessed grooves  175   a  and  176   a  and receiving surfaces  175   b  and  176   b.    
     The recessed grooves  175   a  and  176   a  are annular grooves recessed radially outward from the inner peripheral surface of the annular cylindrical portion  172  and extending over the entire circumferential direction. The receiving surfaces  175   b  and  176   b  are annular surfaces extending radially inward from the lower ends of the recessed grooves  175   a  and  176   a  and extending in the circumferential direction. The receiving surfaces  175   b  and  176   b  have a flat shape orthogonal to the axis O and have an annular shape extending over the entire circumferential direction. The receiving surfaces  175   b  and  176   b  protrude radially inward beyond the upper ends of the recessed grooves  175   a  and  176   a  to which the receiving surfaces  175   b  and  176   b  are connected. 
     The upper oil sump  175  is positioned radially outward of the lower oil sump  176 . The radially inner end portion of the receiving surface  175   b  of the upper oil sump  175  is connected to the upper end of the recessed groove  176   a  of the lower oil sump  176  via a connecting inner peripheral surface  177  forming an inner peripheral cylindrical surface about the axis O. In other words, the upper oil sump  175  and the lower oil sump  176  have a stepped shape in which the lower oil sump  176  positioned below is disposed on the radially inner side. 
     Here, the volume of the recessed groove  175   a  of the upper oil sump  175  is larger than the volume of the recessed groove  176   a  of the lower oil sump  176 . Further, the radial dimension of the receiving surface  175   b  of the upper oil sump  175  is larger than the radial dimension of the receiving surface  176   b  of the lower oil sump  176 . In a cross-sectional shape including the axis O, the area in the upper oil sump  175  surrounded by a line segment interconnecting the upper end of the recessed groove  175   a  of the upper oil sump  175  and the radially inner end portion of the receiving surface  175   b  is larger than the area in the lower oil sump  176  surrounded by a line segment interconnecting the upper end of the recessed groove  176   a  of the lower oil sump  176  and the radially inner end portion of the receiving surface  176   b.  As a result, in a case where the annular cylindrical portion  172  rotates around the axis O, the volume by which the upper oil sump  175  is capable of accommodating lubricating oil is larger than the volume by which the lower oil sump  176  is capable of accommodating lubricating oil. 
     Lubricating Oil Supply Hole 
     The annular member  170  has an upper lubricating oil supply hole  180  as a lubricating oil supply hole allowing the bottom portion of the recessed groove  175   a  of the upper oil sump  175  and the disk support surface  172   a  to communicate with each other in the radial direction. The upper lubricating oil supply hole  180  extends along a direction orthogonal to the axis O. A plurality of the upper lubricating oil supply holes  180  are formed at intervals in the circumferential direction. 
     The annular member  170  has a lower lubricating oil supply hole  181  as a lubricating oil supply hole allowing the bottom portion of the recessed groove  176   a  of the lower oil sump  176  and the inner peripheral surface of the upper fitting hole  171   a  to communicate with each other. The lower lubricating oil supply hole  181  extends radially outward and downward from the bottom portion of the recessed groove  176   a  and is open in the inner peripheral surface of the upper fitting hole  171   a.  The radially outer end portion of the lower lubricating oil supply hole  181  is connected to the first opening portion  162   a  of the carrier shaft  161 . As a result, the lower lubricating oil supply hole  181  communicates with the intra-shaft flow path  162 . A plurality of the lower lubricating oil supply holes  181  are formed in accordance with the number of the carrier shafts  161 . 
     In addition, the configuration of the lubricating oil supply hole is not limited to the above and another configuration may be adopted insofar as the lubricating oil supply hole extends in the radial direction. In addition, insofar as the upper oil sump  175  and the lower oil sump  176  arc respectively provided at positions corresponding to the upper lubricating oil supply hole  180  and the lower lubricating oil supply hole  181 , the upper oil sump  175  and the lower oil sump  176  may not have the annular shape extending over the entire circumferential direction. 
     Brake Mechanism 
     Next, the brake mechanism  120  will be described with reference to  FIGS. 5 and 6 . 
     The brake mechanism  120  is disposed above the first stage planetary gear mechanism  90  in the lower accommodation space R 2  of the speed reducer casing  61 . 
     The brake mechanism  120  includes a brake disk  122 , a brake plate  123 , a brake piston  130 , and a brake spring  140 . The brake mechanism  120  further includes a gutter portion  136 . 
     Brake Disk 
     As shown in  FIGS. 5 to 7 , the brake disk  122  is an annular member and is used as a “wet disk”. A plurality of the brake disks  122  (two brake disks  122  in the present embodiment) are disposed at intervals in the vertical direction so as to overhang from the disk support surface  172   a  of the annular member  170 . The brake disk  122  has a plate shape and the vertical direction is the plate thickness direction of the plate shape. 
     The inner peripheral edge portion of the brake disk  122  may have an uneven shape in which a recessed portion and a projecting portion are continuous in the circumferential direction. The disk support surface  172   a  may have an uneven shape corresponding to the inner peripheral edge portion of the brake disk  122 . And the brake disk  122  may be fixed to the disk support surface  172   a  by the uneven shapes of the inner peripheral edge portion of the brake disk  122  and the disk support surface  172   a  fitting together. 
     The opening position of the upper lubricating oil supply hole  180  in the disk support surface  172   a  is the height position between the pair of brake disks  122 . 
     Brake Plate 
     The brake plate  123  is an annular member and a plurality of the brake plates  123  (three brake plates  123  in the present embodiment) are disposed at intervals in the vertical direction so as to overhang from the inner peripheral surface of the speed reducer casing  61 . The brake plate  123  has a plate shape and the vertical direction is the plate thickness direction of the plate shape. The brake plate  123  is provided so as to overhang from a first sliding contact inner peripheral surface  64   a  on the inner peripheral surface of the speed reducer casing  61 . The first sliding contact inner peripheral surface  64   a  has an inner peripheral cylindrical surface shape about the axis O. 
     On the outer peripheral edge portion of the brake plate  123 , a plurality of projecting portions protruding radially outward may be formed at intervals in the circumferential direction. In the first sliding contact inner peripheral surface  64   a,  recessed portions corresponding to the projecting portions of the brake plate  123  may be formed at intervals in the circumferential direction. The brake plate  123  may be provided so as to be immovable in the circumferential direction and movable in the vertical direction by the projecting portion fitting into the recessed portion of the first sliding contact inner peripheral surface  64   a.    
     The plurality of brake plates  123  and the plurality of brake disks  122  are alternately disposed in the order of the brake plates  123  and the brake disks  122  downward from above. The brake plate  123  and the brake disk  122  are capable of abutting each other in the vertical direction. The abutting surface between the brake plate  123  and the brake disk  122  is a sliding contact surface (sliding portion) S 2 . The outer peripheral edge portion of the brake disk  122  faces the first sliding contact inner peripheral surface  64   a  at intervals from the radially inner side. The inner peripheral edge portion of the brake plate  123  faces the outer peripheral surface of the disk support surface  172   a  of the annular member  170  at an interval from the radially outer side. 
     Here, as shown in  FIG. 7 , a through hole  123   a  penetrating the brake plate  123  in the vertical direction is formed in the outer peripheral edge portion of each brake plate  123 . A plurality of the through holes  123   a  are formed at intervals in the circumferential direction. The through holes  123   a  of the plurality of brake plates  123  are at the same circumferential position. In addition, the through hole  123   a  may be, for example, a gap formed between the top portion of the projecting portion of the brake plate  123  and the bottom portion of the recessed portion of the first sliding contact inner peripheral surface. 
     Further, an overhanging portion  65  overhanging radially inward is formed on the inner peripheral surface of the speed reducer casing  61 . The overhanging portion  65  has an annular shape about the axis O and a plate shape and the vertical direction is the plate thickness direction of the plate shape. The upper surface of the overhanging portion  65  faces the lowermost brake plate  123  from below. Formed in the upper surface of the overhanging portion  65  is a guiding recessed portion  65   a  recessed downward and extending in the radial direction at the same circumferential position as the through hole  123   a.  A plurality of the guiding recessed portions  65   a  are formed at intervals in the circumferential direction. The guiding recessed portion  65   a  extends from a first sliding contact outer peripheral surface to the inner peripheral end portion of the overhanging portion  65  and is open radially inward in the inner peripheral end portion. 
     Brake Piston 
     As shown in  FIGS. 5 to 7 , the brake piston  130  is an annular member about the axis O and is disposed between the upper surface of the brake plate  123  and the lower surface  21   a  of the electric motor casing  21  in the lower accommodation space R 2 . The brake piston  130  is capable of reciprocating in the vertical direction. 
     An upper surface  130   a  of the brake piston  130  faces the lower surface  21   a  of the electric motor casing  21  from below. The lower portion of the outer peripheral surface of the brake piston  130  is a first sliding contact outer peripheral surface  131  having a circular cross-sectional shape orthogonal to the axis O. The first sliding contact outer peripheral surface  131  of the brake piston  130  is slidable in the vertical direction with respect to the first sliding contact inner peripheral surface  64   a  of the speed reducer casing  61 . 
     The upper portion of the outer peripheral surface of the brake piston  130  is a second sliding contact outer peripheral surface  132  having a circular cross-sectional shape orthogonal to the axis O. The second sliding contact outer peripheral surface  132  is larger in outer diameter than the first sliding contact outer peripheral surface  131 . The second sliding contact outer peripheral surface  132  of the brake piston  130  is slidable in the vertical direction with respect to a second sliding contact inner peripheral surface  64   b  of the speed reducer casing  61 . The second sliding contact inner peripheral surface  64   b  of the speed reducer casing  61  is larger in inner diameter than the first sliding contact inner peripheral surface  64   a.    
     The step portion in the brake piston  130  that is between the first sliding contact outer peripheral surface  131  and the second sliding contact outer peripheral surface  132  is a pressure receiving surface  133  forming a flat shape orthogonal to the axis O, facing downward, and forming an annular shape. 
     The step portion in the speed reducer casing  61  that is between the first sliding contact inner peripheral surface  64   a  and the second sliding contact inner peripheral surface  64   b  is a stepped surface  64   c  forming a flat shape orthogonal to the axis O, facing upward, and forming an annular shape. 
     The pressure receiving surface  133  and the stepped surface  64   c  face each other in the vertical direction and approach and separate from each other as the brake piston  130  moves in the vertical direction. The annular space between the pressure receiving surface  133  and the stepped surface  64   c  is a hydraulic pressure supply space R 4 . 
     The speed reducer casing  61  has a hydraulic pressure supply hole  61   a  interconnecting the stepped surface  64   c  and the outside of the speed reducer casing  61 . The hydraulic pressure supply space R 4  communicates with the outside via the hydraulic pressure supply hole  61   a.  The hydraulic pressure that is generated by the hydraulic pump  238  is introduced into the hydraulic pressure supply hole  61   a  in a case where, for example, the swinging lock lever of the hydraulic shovel  200  is released. 
     On an annular lower surface  130   b  of the brake piston  130 , a plate abutting surface  134  having an annular shape about axis O is formed so as to protrude from the lower surface  130   b.  The plate abutting surface  134  faces the brake plate  123  from above over the entire circumferential direction. 
     The upper surface  130   a  of the brake piston  130  has a piston-side accommodation recessed portion  135  recessed downward from above. A plurality of the piston-side accommodation recessed portions  135  are disposed at intervals in the circumferential direction. 
     The lower surface  21   a  of the electric motor casing  21  has a casing-side accommodation recessed portion  28  recessed upward from below. A plurality of the casing-side accommodation recessed portions  28  are disposed at intervals in the circumferential direction. The casing-side accommodation recessed portion  28  is disposed at the circumferential position that corresponds to the second bottom surface  27   c.  Each casing-side accommodation recessed portion  28  and each piston-side accommodation recessed portion  135  are provided at the same circumferential position so as to correspond to each other in a one-to-one relationship. The electric motor casing  21  has a hole portion  29  allowing the casing-side accommodation recessed portion  28  and the second bottom surface  27   c  to communicate with each other. 
     A space defined by the casing-side accommodation recessed portion  28  and the piston-side accommodation recessed portion  135  is defined as a spring accommodation space R 3 . 
     In addition, the outer peripheral-side communication hole  52  is open in the lower surface  21   a  of the electric motor casing  21  radially inward of the brake piston  130 . 
     Brake Spring 
     The brake spring  140  is provided in the spring accommodation space R 3  and presses the brake piston  130  in a direction away from the electric motor casing  21 . 
     The brake spring  140  of the present embodiment is a coil spring and is disposed in a posture allowing expansion and contraction in the vertical direction in the spring accommodation space R 3 . The brake spring  140  is accommodated in a compressed state in the spring accommodation space R 3 . The upper end of the brake spring  140  abuts against the bottom surface of the casing-side accommodation recessed portion  28  in the electric motor casing  21  and the lower end of the brake spring  140  abuts the bottom surface of the piston-side accommodation recessed portion  135  in the brake piston  130 . 
     Gutter Portion 
     At the lower end of the brake piston  130 , the gutter portion  136  extending radially inward from the inner peripheral surface of the brake piston  130  is provided integrally with the brake piston  130 . A plurality of the gutter portions  136  are provided at intervals in the circumferential direction. For example, in the present embodiment, two gutter portions  136  are provided at an interval of 180° in the circumferential direction. A flow path groove  136   a  extending in the direction of extension of the gutter portion  136  is formed in the upper surface of the gutter portion  136 . The flow path groove  136   a  is open radially inward in the radially inner end portion of the gutter portion  136 . The radially inner end portion of the gutter portion  136  is positioned above the upper end surface of the first stage transmission shaft  91 . In other words, the radially inner end portion of the gutter portion  136  is positioned above the fitting portion between the rotary shaft  40  and the first stage transmission shaft  91 . 
     Lubricating Oil Circulation Unit 
     As shown in  FIG. 3 , the lubricating oil circulation unit  150  supplies lubricating oil into the upper accommodation space R 1  in the electric motor casing  21  and re-supplies the lubricating oil collected from the inside of the lower accommodation space R 2  in the speed reducer casing  61  into the upper accommodation space R 1 . 
     The lubricating oil circulation unit  150  includes a lubricating oil flow path  151 , a lubricating oil pump  152 , a cooling unit  153 , and a strainer  154 . 
     The lubricating oil flow path  151  is a flow path formed by a flow path forming member such as piping provided outside the rotary drive device  10 . A first end of the lubricating oil flow path  151 , which is an upstream side end portion thereof, is connected to the lower accommodation space R 2  in the speed reducer casing  61 . In the present embodiment, the first end of the lubricating oil flow path  151  is connected to the part in the lower accommodation space R 2  that is between the output shaft bearing  71  and the lower seal  72 . 
     A second end of the lubricating oil flow path  151 , which is a downstream side end portion thereof, is connected to the opening of the intra-rotor flow path F at the upper end of the rotary shaft  40 . The second end of the lubricating oil flow path  151  is connected to the upper accommodation space R 1  in the electric motor casing  21  via the intra-rotor flow path F. 
     The lubricating oil pump  152  is provided in the flow path of the lubricating oil flow path  151  and pumps lubricating oil from the first end toward the second end of the lubricating oil flow path  151 , that is, from the lower accommodation space R 2  side toward the upper accommodation space R 1  side. 
     The cooling unit  153  is provided at the part of the lubricating oil flow path  151  that is downstream of the lubricating oil pump  152 . The cooling unit  153  cools the lubricating oil that flows through the lubricating oil flow path  151  by heat exchange with the external atmosphere. 
     The strainer  154  is provided at the part of the lubricating oil flow path  151  that is upstream of the lubricating oil pump  152 . The strainer  154  has a filter removing dust and dirt from the lubricating oil that passes through the lubricating oil flow path  151 . It is preferable that the strainer  154  includes a magnetic filter removing, for example, iron powder generated from the gear teeth of the speed reducer  60 . 
     In the present embodiment, lubricating oil is stored in the second accommodation space R 2  in the speed reducer casing  61 . And, of the planetary gear mechanisms, the second stage planetary gear mechanism  100  and the third stage planetary gear mechanism  110  are immersed in the lubricating oil. In other words, a liquid surface S of the lubricating oil in the lower accommodation space R 2  is positioned between the first stage planetary gear mechanism  90  and the second stage planetary gear mechanism  100 . 
     Action and Effect 
     When the engine  236  of the hydraulic shovel  200  is started, hydraulic pressure is generated by the hydraulic pump  238  being simultaneously driven. Then, by the swinging lock lever being released, the brake of the rotary shaft  40  of the rotary drive system is released and the rotary shaft becomes rotatable. 
     In other words, the brake piston  130  of the brake mechanism  120  is pressed downward by the brake spring  140 . As a result, in a state where no hydraulic pressure is supplied to the hydraulic pressure supply space R 4 , the brake piston  130  moves downward and presses the brake disk  122  via the brake plate  123 . At this time, the rotary shaft  40  is in a non-rotatable brake state by the frictional force between the brake plate  123  and the brake disk  122 . 
     Then, the brake piston  130  that has received the hydraulic pressure on the pressure receiving surface  133  moves upward when the hydraulic pressure is supplied to the hydraulic pressure supply space R 4  via the hydraulic pressure supply hole  61   a  by the swinging lock lever being unlocked. As a result, the pressing of the brake plate  123  and the brake disk  122  by the brake piston  130  is released and the rotary shaft  40  is put into a rotatable brake release state. 
     Then, the rotary drive system  1  is driven and the upper swing body  230  swings by the swinging lever in the cab  231  being operated. 
     In other words, when the swinging lever is operated, alternating current electric power is supplied to each coil  32  of the stator  30  of the electric motor  20  via the inverter  239  and the rotor  38  rotates with respect to the stator  30  by each permanent magnet following the rotating magnetic field that is generated by the coils  32 . The rotation of the rotary shaft  40  of the rotor  38  is decelerated via the transmission unit  80  in the speed reducer  60  and transmitted to the output shaft  70 . In the present embodiment, the deceleration is sequentially performed via the three-stage planetary gear mechanisms. The swinging operation of the upper swing body  230  is performed by the rotation of the output shaft  70 . 
     The electric motor  20  is driven with high torque when the upper swing body  230  swings. Accordingly, the temperatures of the rotor core  42  and the permanent magnet rise due to the iron loss in the rotor core  42  and the eddy current loss in the permanent magnet. At the same time, the temperature of the stator  30  rises due to the copper loss in the coil  32  and the iron loss in the stator core  31 . When the temperature of the stator  30  is high, the temperature of the rotor core  42  becomes higher due to the radiant heat of the stator  30 . Accordingly, cooling oil is supplied into the electric motor  20  by the lubricating oil circulation unit  150 . 
     When the swinging lever is operated, the lubricating oil pump  152  of the lubricating oil circulation unit  150  is driven together with the drive of the electric motor  20 . As a result, the lubricating oil stored by the lower accommodation space R 2  being used as a tank is partially introduced into the intra-rotor flow path F of the electric motor  20  via the lubricating oil flow path  151 . The lubricating oil cools the rotor core  42  and the permanent magnets in the course of flowing through the intra-rotor flow path F. Then, the lubricating oil discharged from the rotor  38  to the upper accommodation space R 1  in the electric motor casing  21  is sprayed radially outward by the centrifugal force resulting from the rotation of the rotor  38  and cools the coil  32  and the stator core  31 . 
     Subsequently, the lubricating oil that has fallen in the upper accommodation space R 1  passes through the communication hole  50  penetrating the lower bottom portion  27  of the electric motor casing  21  or passes through the lower bearing  37 . Then, the lubricating oil is introduced into the lower accommodation space R 2  in the speed reducer casing  61 . The lubricating oil passes through the lower bearing  37  and thus lubricity is ensured in the lower bearing  37 . 
     The lubricating oil introduced into the lower accommodation space R 2  merges with the lubricating oil stored by the lower accommodation space R 2  being used as a tank. In the lower accommodation space R 2 , each planetary gear mechanism is lubricated by the lubricating oil falling from the electric motor casing  21  or by the stored lubricating oil. 
     Here, in the present embodiment, the first stage planetary gear mechanism  90 , which is one of the plurality of planetary gear mechanisms in the transmission unit  80 , is not immersed in the lubricating oil stored in the lower accommodation space R 2 . In addition, the brake mechanism  120  is not immersed in the lubricating oil. The first stage planetary gear  92  of the first stage planetary gear mechanism  90  and the brake disk  122  of the brake mechanism  120  rotate at a speed higher than the rotation speeds of the planetary gears of the other planetary gear mechanisms. Accordingly, since the first stage planetary gear  92  and the brake disk  122  are not immersed in the lubricating oil, the stirring loss of the lubricating oil as the entire transmission unit  80  can be reduced. 
     It is necessary to ensure the lubricity of the first stage planetary gear  92  and the brake disk  122  that are not immersed in the lubricating oil as described above. In the present embodiment, lubricating oil is supplied to the sliding surface S 1  between the first stage planetary gear  92  and the first stage carrier  93  and the sliding contact surface S 2  between the brake disk  122  and the brake plate  123  via the annular member  170 . 
     In other words, as shown in  FIGS. 5 and 6 , the lubricating oil introduced into the lower accommodation space R 2  via the inner peripheral-side communication hole  51  and the outer peripheral-side communication hole  52 , which are the communication holes  50  of the electric motor casing  21 , partially reaches the inner peripheral side of the annular member  170 . The lubricating oil is accommodated in each of the upper oil sump  175  and the lower oil sump  176  in the inner peripheral surface of the annular member  170  in accordance with the centrifugal force. 
     The lubricating oil accommodated in the upper oil sump  175  flows through the upper lubricating oil supply hole  180  in accordance with the centrifugal force and is discharged from the disk support surface  172   a.  As a result, the lubricating oil is supplied to the sliding contact surface S 2  between the brake disk  122  and the brake plate  123  and lubricity is ensured on the sliding contact surface S 2 . The lubricating oil guided to the brake disk  122  and the brake plate  123  passes through the through hole  123   a  of the brake plate  123  and flows downward. Then, the lubricating oil passes through the guiding recessed portion  65   a  of the overhanging portion  65  and further flows downward from the radially inner end portion of the guiding recessed portion  65   a.    
     The lubricating oil accommodated in the lower oil sump  176  flows through the lower lubricating oil supply hole  181  in accordance with the centrifugal force and is introduced into the intra-shaft flow path  162  of the carrier shaft  161  from the first opening portion  162   a.  The lubricating oil that has flowed through the intra-shaft flow path  162  is discharged from the second opening portion  162   b  of the intra-shaft flow path  162  and is supplied to the sliding surface S 1  between the carrier shaft  161  and the first stage planetary gear  92 . As a result, the lubricity of the sliding surface SI is ensured. 
     As described above, in the present embodiment, the lubricating oil that has reached the inner peripheral surface of the annular member  170  by being supplied into the speed reducer casing  61  from above is temporarily collected in the oil sump and then flows through the lubricating oil supply hole toward the outer peripheral side in accordance with the centrifugal force. Then, the lubricating oil discharged from the lubricating oil supply hole is supplied to the sliding portion on the radially outer side of the lubricating oil supply hole. As a result, lubricity can be ensured for the sliding portion. 
     In addition, the lower oil sump  176  positioned below is positioned radially inward of the upper oil sump  175  positioned above. Accordingly, the lubricating oil that the upper oil sump  175  has failed to accommodate drips down from the upper oil sump  175  and is introduced into the lower oil sump  176 . As a result, it is possible to smoothly supply the lubricating oil to both the upper oil sump  175  and the lower oil sump  176 . 
     Further, the upper oil sump  175  and the lower oil sump  176  have the receiving surfaces  175   b  and  176   b,  respectively. Since there are no other structures other than the annular member  170  above the receiving surfaces  175   b  and  176   b,  the lubricating oil falling from the communication hole  50  of the electric motor casing  21  can be received by the receiving surfaces  175   b  and  176   b.  The lubricating oil received by the receiving surfaces  175   b  and  176   b  is accommodated in the recessed grooves  175   a  and  176   a  in accordance with the centrifugal force of the rotating annular member  170 . In addition, the lubricating oil that has received the centrifugal force is capable of remaining on the receiving surfaces  175   b  and  176   b.  In other words, it is possible for the receiving surfaces  175   b  and  176   b  themselves to be functioned as lubricating oil storage portions. As a result, the upper oil sump  175  and the lower oil sump  176  are capable of accommodating more lubricating oil than in a case where only the receiving surfaces  175   b  and  176   b  are formed. 
     In addition, in the present embodiment, a configuration in which lubricating oil is supplied from the upper oil sump  175  and the lower oil sump  176  is adopted, and thus it is possible to reliably lubricate the sliding portions of the first stage planetary gear mechanism  90  and the brake mechanism  120 . 
     In particular, even in a case where the hydraulic shovel  200  is on a slope, it is possible to more reliably lubricate the first stage planetary gear mechanism  90  and the brake mechanism  120  by guiding lubricating oil radially outward from the upper oil sump  175  and the lower oil sump  176  by means of the centrifugal force. 
     Here, the brake mechanism  120  needs to ensure more lubricity than the first stage planetary gear mechanism  90 . In other words, the brake disk  122  and the brake plate  123  may be in contact with each other at all times, and thus it is preferable that a large amount of lubricating oil is supplied to the sliding contact surface S 2  between the brake disk  122  and the brake plate  123 . In this regard, in the present embodiment, the volume by which lubricating oil can be accommodated in the upper oil sump  175  is larger than the volume by which lubricating oil can be accommodated in the lower oil sump  176 . As a result, lubricity can be sufficiently ensured for the brake disk  122  to which lubricating oil is guided via the upper oil sump  175 . It is possible to supply an appropriate amount of lubricating oil to the first stage planetary gear mechanism  90  via the lower oil sump  176 . 
     Here, the fitting portion between the lower end of the rotary shaft  40  and the first stage transmission shaft  91  rotates at a high speed. Accordingly, fretting wear may occur in the fitting portion. 
     In the present embodiment, the gutter portion  136  is provided integrally with the brake piston  130 . The lubricating oil introduced into the lower accommodation space R 2  via the communication hole  50  of the electric motor casing  21  partially reaches the gutter portion  136 , flows through the flow path groove  136   a,  and falls from above the fitting portion. Lubricity is ensured for the fitting portion by the lubricating oil being supplied to the fitting portion. The fretting wear can be suppressed as a result. 
     Another Embodiment 
     Although the embodiment of the present invention has been described above, the present invention is not limited thereto and can be appropriately changed without departing from the technical idea of the present invention. 
     Described in the embodiment is an example in which the annular member  170  is provided integrally with the first stage carrier  93  of the first stage planetary gear mechanism  90 . However, the present invention is not limited thereto. For example, the annular member  170  may be provided integrally with another component of the transmission unit  80  or may be provided integrally with the rotary shaft  40 . 
     Although an example in which both the upper oil sump  175  and the lower oil sump  176  are formed in the annular member  170  has been described in the embodiment, only one of the upper oil sump  175  and the lower oil sump  176  may be formed. Correspondingly, only one of the upper lubricating oil supply hole  180  and the lower lubricating oil supply hole  181  may be formed. 
     The brake mechanism  120  is not limited to the example of being disposed above the first stage planetary gear mechanism  90 . For example, the brake mechanism  120  may be disposed at another location, examples of which include the location between the first stage planetary gear mechanism  90  and the second stage planetary gear mechanism  100  and the location between the second stage planetary gear mechanism  100  and the third stage planetary gear mechanism  110 . 
     The planetary gear mechanisms are not limited to three stages and may be replaced with a single-stage planetary gear mechanism or those with a plurality of stages such as two stages and four or more stages. In addition, the brake mechanism  120  may be disposed at any position with respect to the planetary gear mechanisms. 
     Another sliding portion may be adopted although the sliding surface S 1  between the first stage planetary gear  92  and the carrier shaft  161  and the sliding contact surface S 2  between the brake disk  122  and the brake plate  123  have been described as examples of the sliding portion in the embodiment. In other words, lubricating oil may be supplied to another sliding portion requiring the lubricating oil via the oil sump of the annular member  170  and the lubricating oil supply hole. 
     Three or more oil sumps may be formed in the annular member with three or more lubricating oil supply holes formed so as to correspond to the oil sumps. In this case, the oil sump disposed lower than another one may be provided radially inward than the other one. In this manner, the lower oil sump also can be appropriately supplied with the lubricating oil that has flowed downward from the upper oil sump. 
     A plurality of lubricating oil supply holes guiding lubricating oil to different sliding portions may be formed with respect to one oil sump. 
     Although the rotary drive system  1  of the present embodiment is configured to use the electric motor  20 , a hydraulic motor or the like may be applied instead of the electric motor  20  or a configuration in which the electric motor  20  and a hydraulic motor are combined may be applied. 
     Although an example in which the present invention is applied to the rotary drive system  1  of the hydraulic shovel  200  as a work machine has been described in the embodiment, the present invention may be applied to the rotary drive system  1  as a mechanism swinging or rotating part of another work machine. The present invention may be applied to a speed reducer alone as well as the rotary drive system  1  including the electric motor  20  and the speed reducer  60 . 
     INDUSTRIAL APPLICABILITY 
     According to the speed reducer, the rotary drive system, and the hydraulic shovel of the above aspect, it is possible to smoothly supply lubricating oil to a sliding portion. 
     REFERENCE SIGNS LIST 
       1 : Rotary drive system 
       10 : Rotary drive device 
       20 : Electric motor 
       21 : Electric motor casing 
       21   a:  Lower surface 
       22 : Upper casing 
       23 : Upper cylindrical portion 
       24 : Upper bottom portion 
       25 : Lower casing 
       26 : Lower cylindrical portion 
       27 : Lower bottom portion 
       27   a:  Lower through hole 
       27   b:  First bottom surface 
       27   c:  Second bottom surface 
       27   d:  Stepped portion 
       28 : Casing-side accommodation recessed portion 
       30 : Stator 
       31 : Stator core 
       32 : Coil 
       35 : Upper seal 
       36 : Upper bearing 
       37 : Lower bearing 
       38 : Rotor 
       40 : Rotary shaft 
       42 : Rotor core 
       45 : Lower end plate 
       46 : Upper end plate 
       50 : Communication hole 
       51 : Inner peripheral-side communication hole 
       52 : Outer peripheral-side communication hole 
       60 : Speed reducer 
       61 : Speed reducer casing 
       61   a:  Hydraulic pressure supply hole 
       62   a:  First stage inner gear teeth 
       62   b:  Second stage inner gear teeth 
       62   c:  Third stage inner gear teeth 
       64   a:  First sliding contact inner peripheral surface 
       64   b:  Second sliding contact inner peripheral surface 
       64   c:  Stepped surface 
       65 : Overhanging portion 
       65   a:  Guiding recessed portion 
       70 : Output shaft 
       71 : Output shaft bearing 
       72 : Lower seal 
       80 : Transmission unit 
       90 : First stage planetary gear mechanism 
       91 : First stage transmission shaft (transmission shaft) 
       91   a:  Cylindrical portion 
       91   b:  Upper end 
       91   c:  Flange portion 
       91   d:  Sun gear teeth 
       92 : First stage planetary gear (planetary gear) 
       92   a:  Planetary gear teeth 
       93 : First stage carrier (carrier) 
       100 : Second stage planetary gear mechanism 
       101 : Second stage transmission shaft 
       101   a:  Sun gear teeth 
       102 : Second stage planetary gear 
       103 : Second stage carrier 
       110 : Third stage planetary gear mechanism 
       111 : Third stage transmission shaft 
       111   a:  Sun gear teeth 
       112 : Third stage planetary gear 
       113 : Third stage carrier 
       120 : Brake mechanism 
       122 : Brake disk 
       123 : Brake plate 
       123   a:  Through hole 
       130 : Brake piston 
       130   a:  Upper surface 
       130   b:  Lower surface 
       131 : First sliding contact outer peripheral surface 
       132 : Second sliding contact outer peripheral surface 
       133 : Pressure receiving surface 
       134 : Plate abutting surface 
       135 : Piston-side accommodation recessed portion (recessed portion) 
       136 : Gutter portion 
       136   a:  Flow path groove 
       140 : Brake spring 
       150 : Lubricating oil circulation unit 
       151 : Lubricating oil flow path 
       152 : Lubricating oil pump 
       153 : Cooling unit 
       154 : Strainer 
       161 : Carrier shaft 
       162 : Intra-shaft flow path 
       162   a:  First opening portion 
       162   b:  Second opening portion 
       163 : Upper radial flow path 
       164 : Intermediate radial flow path 
       165 : Axial flow path 
       167 : Carrier main body 
       167   a:  Lower fitting hole 
       170 : Annular member 
       171 : Annular plate portion 
       171   a:  Upper fitting hole (fitting hole) 
       172 : Annular cylindrical portion 
       172   a:  Disk support surface 
       175 : Upper oil sump (oil sump) 
       175   a:  Recessed groove 
       175   b:  Receiving surface 
       176 : Lower oil sump (oil sump) 
       176   a:  Recessed groove 
       176   b:  Receiving surface 
       177 : Connecting inner peripheral surface 
       180 : Upper lubricating oil supply hole (lubricating oil supply hole) 
       181 : Lower lubricating oil supply hole (lubricating oil supply hole) 
       200 : Hydraulic shovel 
       211 : Crawler 
       210 : Undercarriage 
       220 : Swing circle 
       221 : Outer race 
       222 : Inner race 
       223 : Swing pinion 
       230 : Upper swing body 
       231 : Cab 
       232 : Work equipment 
       233 : Boom 
       234 : Arm 
       235 : Bucket 
       236 : Engine 
       237 : Generator motor 
       238 : Hydraulic pump 
       239 : Inverter 
       240 : Capacitor 
     L: Swing axis 
     O: Axis 
     S: Liquid surface 
     R 1 : Upper accommodation space 
     R 2 : Lower accommodation space 
     R 3 : Spring accommodation space 
     R 4 : Hydraulic pressure supply space 
     F: Intra-rotor flow path 
     S 1 : Sliding surface (sliding portion) 
     S 2 : Sliding contact surface (sliding portion)