A motor and planetary reducer integrated device and manufacturing method thereof

Abstract

The present invention discloses an integrated device of a motor and a planetary reducer and a manufacturing method thereof, and the technical scheme thereof includes: a casing, a motor assembly and a planetary reducer assembly, the casing is provided with mounting cavities for the motor assembly and the planetary reducer assembly respectively, the motor assembly and the planetary reducer assembly are matched in transmission, and a cooling structure is provided on the outer circle of the casing. The manufacturing method mainly processes the casing, the stator core is installed on the casing, the rear end cover of the motor is fixed on the casing, the rotor of the motor is first installed on the front end cover inside the motor, and then pressed into the stator, the sun gear of the planetary reducer is installed on the motor shaft, and the gear lubricating oil is added through the planetary gear oil filling port on the casing, and the coolant needs to be introduced into the casing during operation. The entire technical scheme has a compact structure, simple transmission, and convenient maintenance, and the system efficiency, rotation accuracy, position accuracy and service life are greatly improved, and the heat generation and operating noise are greatly reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of mechanical transmission, and in particular to a motor and planetary reducer integrated device and a manufacturing method thereof. Background Art

[0002] At present, the traditional method is to use a motor and a reducer combination to drive the operation. Since the motor and reducer are independent in the traditional combination, the main disadvantages are: 1. The heat is high and each requires an independent cooling system; 2. The transmission connection accessories are prone to mechanical wear during long-term operation and require regular maintenance; 3. The transmission system is large in size and bulky in structure; 4. The transmission positioning accuracy is low; 5. The operation noise is high. The above defects have caused the existing transmission system to be relatively extensive, with low accuracy, large space occupation, high failure rate, and high requirements for equipment installation and maintenance.

[0003] The current patent number CN202022079956.9 discloses a direct connection mechanism for a motor and a reducer, the main function of which is to greatly shorten the distance between the motor and the reducer and reduce the length of the entire mechanism. This also reduces the overall volume and space occupied, and the transmission is more reliable and stable, but the problems of high heat generation, high operating noise and transmission positioning accuracy have not been overcome.

[0004] In order to reduce the volume of the transmission system, improve transmission efficiency, reduce heat generation, reduce operating noise, and significantly increase service life, it is necessary to design an integrated liquid cooling structure for the motor and planetary reducer. Summary of the invention

[0005] In view of the deficiencies in the prior art, the present invention provides a motor and planetary reducer integrated device and a manufacturing method thereof.

[0006] In order to achieve the above-mentioned purpose, the present invention is implemented through the following technical scheme: a motor and planetary reducer integrated device, including a casing, a motor assembly and a planetary reducer assembly, the casing is provided with installation cavities for the motor assembly and the planetary reducer assembly respectively, the motor assembly and the planetary reducer assembly are matched in transmission, and a cooling structure is provided on the outer circle of the casing.

[0007] Preferably, the motor assembly includes a stator, a rotor, a motor shaft, a motor rear end cover and a motor internal front end cover, the motor rear end cover is fixed on the casing, the rotor is installed inside the stator, one end of the rotor is connected to the motor shaft, one end of the stator is connected to the motor rear end cover, the other end of the stator is connected to the motor internal front end cover, the stator core is interference fit inside the casing, and the stator core is provided with a motor winding. The structure is stable for installation and has high connection accuracy.

[0008] Preferably, the planetary reducer assembly includes a planetary reducer assembly housing, a planetary reducer sun gear and a planetary reducer planetary gear, wherein the planetary reducer sun gear is mounted on the motor shaft and directly inserted into the planetary reducer planetary gear, so that the structure is compact, the rotation accuracy is high and the noise is low.

[0009] Preferably: the output end face of the housing is provided with a reducer output end cover and an output flange, and a front cover mounting plate is provided inside the housing, so that the reducer can be installed more stably, and the reducer output end cover is fixed on the housing and directly serves as the output end of the integrated machine.

[0010] The cooling structure comprises a spiral water groove arranged on the outer circle of the casing, a coolant inlet and a coolant outlet connected to the spiral water groove, and a water groove sealing plate is arranged on the upper surface of the spiral water groove on the casing, so as to facilitate the addition and replacement of the coolant.

[0011] Preferably, the opposite sides of the housing are provided with a planetary gear oil filling port and a planetary gear oil drain port, and are also provided with a plurality of oil level observation ports. The planetary gear oil filling port can be used to add gear lubricating oil for lubrication to reduce friction and noise; the oil level observation port is convenient for observing the oil level and can be added in time.

[0012] A method for manufacturing an integrated motor and a planetary reducer, characterized by the following steps:

[0013] S1. Processing of the casing: First, the round steel is roughly turned to the required dimensions of the inner and outer circles, and then the spiral water tank is milled on the outer circle, and the front cover mounting plate is welded inside it. Then, the coolant inlet, coolant outlet and oil level observation port are welded on the outside, and the two ends of the water tank sealing plate are welded at the same time. All welding is required to be leak-proof. After welding, the whole is heated and annealed. The casing is respectively processed by outer circle fine turning, inner circle fine turning, drilling in the machining center, rust-proof blackening treatment on the surface, and ventilation test and sealing;

[0014] S2. The stator core is installed on the casing. First, the casing is heated to a high temperature to expand the casing, and the stator core is inserted or pressed into the casing. The inserted stator core and casing are placed indoors for cooling. After the temperature drops to room temperature, the next step is performed.

[0015] S3. The rear end cover of the motor is fixed on the casing; the rotor of the motor is first installed on the front end cover inside the motor, and then pressed into the stator. The front end cover inside the motor is fixed on the front end cover mounting plate, and the front end cover inside the motor is made oil-proof and waterproof through a sealing ring.

[0016] S4. The sun gear of the planetary reducer is installed on the motor shaft: the motor shaft adopts the spline method, and the sun gear of the planetary reducer adopts the internal spline plus external spline method. The two are connected and tightened with a gland;

[0017] S5. Apply a circle of high-temperature sealant on the inner side of the reducer output end cover, align the planetary reducer planetary gear with the planetary reducer sun gear on the motor shaft, and install it into the casing. There are two positioning joints in the casing. The inner positioning joint controls the input end accuracy of the reducer, and the outer positioning joint controls the output end accuracy of the reducer. The reducer output end cover is fixed on the casing and directly used as the output end of the integrated machine.

[0018] S6. Add gear lubricating oil through the planetary gear oil filling port on the casing. Stop adding oil when the amount exceeds the oil level observation port. Fix the oil filling port with a vent cap. After all parts are installed, the entire integrated machine can be operated. During operation, coolant needs to be introduced into the casing.

[0019] Optimum: In step S1, the end cover mounting plate needs to be chamfered at a 45° angle before welding and close to the inner circle positioning port of the casing. The welding points are uniform, without pores and welds. To ensure strength, the welding point width is 8-10mm. After welding, the whole is heated to 575-625°C, and the holding time is 1 hour for annealing every 25mm thickness to eliminate the residual stress generated during the welding process; the outer circle of the casing is finely turned, and the accuracy requirement is <0.05mm, the inner circle of the casing is finely turned, and the accuracy requirement is <0.02mm. The machining center punches holes with an accuracy requirement of <0.1mm. Ensure the accuracy of assembly and greatly improve the service life.

[0020] Preferably: in step S2, the housing is heated at 180-220°C for 1-3 hours to allow the housing to expand, and the mounted stator core and housing are placed indoors for natural cooling or cooled by a fan. The advantage of interference fit installation after heating is that the equipment used during installation is simple, the accuracy after mounting is guaranteed to a certain extent, and the deformation can generally be controlled within 0.05mm.

[0021] Preferably, in step S6, the coolant is introduced into the spiral water tank of the casing at a pressure of 3-5 kg ​​and a temperature of less than 40° C. The actual cooling effect is determined by the load size and the temperature and flow rate of the coolant in the casing. The above parameters are used to ensure the cooling effect and cooling efficiency as much as possible.

[0022] The present invention has the beneficial effects of:

[0023] 1. The motor and planetary reducer are integrated, with compact structure, small size and light weight;

[0024] 2. The casing adopts a liquid cooling structure, which directly cools the motor and planetary reducer, making it low in heat generation, good in cooling effect, and simple in structure;

[0025] 3. The sun gear of the planetary reducer is directly mounted on the motor shaft of the rotor and directly inserted into the planetary gear of the planetary reducer, making it compact in structure, high in rotation accuracy and low in noise;

[0026] 4. The motor and planetary reducer have high operating efficiency and low energy consumption;

[0027] 5. The stator is directly cooled by the cooling structure on the casing, and the planetary belt reducer is lubricated by the gear lubricating oil and transmits the temperature to the motor casing, and then cooled by the motor cooling structure, so that the cooling structure is simplified, the cooling is uniform, the temperature drops quickly, the operation efficiency is high and the energy consumption is low;

[0028] 6. The entire technical solution has a compact structure, simple transmission, and convenient maintenance. The system efficiency, rotation accuracy, position accuracy, and service life are greatly improved, and the heat generation and operating noise are greatly reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a schematic diagram of the external structure of the present invention;

[0030] Figure 2 is an internal cross-sectional view of the present invention;

[0031] Figure 3 It is a schematic diagram of the external structure of the casing in the present invention;

[0032] Figure 4 It is a schematic diagram of the internal structure of the casing in the present invention;

[0033] Figure 5 It is a schematic diagram of the present invention;

[0034] Figure 6 This is a schematic diagram of the connection between the housing and the motor in the present invention;

[0035] Figure 7 This is a schematic diagram of the installation of the sun gear of the planetary reducer in the present invention;

[0036] Figure markings: 1- housing; 2- stator; 3- rear end cover of the motor; 4- front end cover inside the motor; 5- rotor; 6- motor shaft; 7- sun gear of planetary reducer; 8- planetary gears of planetary reducer; 9- housing of planetary reducer assembly; 10- output end cover of reducer; 11- output flange; 12- output shaft; 13- oil hole; 14- mounting cavity; 15- front end cover mounting plate; 16- spiral water trough; 17- coolant inlet; 18- coolant outlet; 19- water trough sealing plate; 20- oil filling port of planetary gear; 21- oil drain port of planetary gear; 22- oil level observation port; 23- stator core. DETAILED DESCRIPTION

[0037] Combined with Figure 1-7 , Embodiments 1 to 7 of the present invention are further described in detail.

[0038] Embodiment 1

[0039] A motor and planetary reducer integrated device, including a housing 1, a motor assembly and a planetary reducer assembly, wherein the housing 1 is provided with mounting cavities 14 for the motor assembly and the planetary reducer assembly, respectively, wherein the motor assembly includes a stator 2, a rotor 5, a motor shaft 6, a motor rear end cover 3 and a motor internal front end cover 4, wherein the motor rear end cover 3 is fixed to the housing 1, wherein the rotor 5 is installed in the stator 2, wherein one end of the rotor 5 is connected to the motor shaft 6, one end of the stator 2 is connected to the motor rear end cover 3, and the other end of the stator 2 is connected to the motor internal front end cover 4, wherein the stator core 23 is interference fit inside the housing 1, and the stator core 23 is provided with a motor winding. The structure is stable for installation and has high connection accuracy.

[0040] The motor assembly and the planetary reducer assembly are in driving cooperation, and the planetary reducer assembly includes a planetary reducer assembly housing 91, a planetary reducer sun gear 7 and a planetary reducer planetary gear 8. The planetary reducer sun gear 7 is mounted on the motor shaft 6 and directly inserted into the planetary reducer planetary gear 8. The motor rotor 5 rotates to drive the motor shaft 6 to rotate, and the motor shaft 6 drives the planetary reducer sun gear 7 to rotate, and finally the output shaft 12 rotates. The overall structure is compact, the rotation accuracy is high and the noise is low.

[0041] The output end face of the housing 1 is provided with a reducer output end cover 10 and an output flange 11, and a front cover mounting plate 15 is provided inside the housing 1. This facilitates the installation of the reducer to be more stable, and at the same time, the reducer output end cover is fixed on the housing 1 and directly serves as the output end of the integrated machine.

[0042] A cooling structure is provided on the outer circle of the housing 1, and the cooling structure includes a spiral water groove 16 provided on the outer circle of the housing 1 and a coolant inlet 17 and a coolant outlet 18 connected to the spiral water groove 16, and a water groove sealing plate 19 is provided on the upper surface of the spiral water groove 16 on the housing 1. The coolant is added from the coolant inlet 17 to the spiral water groove 16 for circulation and cooling.

[0043] The housing 1 is provided with a planetary gear oil filling port 20 and a planetary gear oil discharge port 21 on opposite sides thereof, and is also provided with a plurality of oil level observation ports 22. The planetary gear oil filling port 20 can be used to add gear lubricating oil for lubrication to reduce friction and noise; the oil level observation port 22 is convenient for observing the oil level and can be added in time.

[0044] The planetary reducer is cooled in the front section of the casing 1, and the motor is cooled in the rear section of the casing 1. The outer side is made of round steel with spiral water grooves milled on the surface, and then wrapped with round steel for welding and sealing. A coolant inlet 17 and a coolant outlet 18 are left. The front section of the liquid-cooled casing 1 is sealed with the front end cover 4 inside the motor and the output end cover 10 of the reducer, and gear lubricating oil is added.

[0045] The planetary gear oil filling port 20 is installed on the upper side of the front section of the housing 1, and the planetary gear oil drain port 21 is installed on the lower side. An oil level observation port 22 can be set on each side. This structure can simultaneously complete the internal lubrication and cooling, and perform double-circulation heat exchange with external liquid cooling, which can achieve rapid cooling, low temperature rise, more reliable long-term operation and extended service life.

[0046] A method for manufacturing an integrated motor and a planetary reducer, characterized by the following steps:

[0047] S1, processing of the casing; firstly, the round steel is roughly turned to the required size of the inner and outer circles, and then the spiral water tank 16 is milled on the outer circle, and the front end cover mounting plate 15 is welded inside it, and then the coolant inlet 17, the coolant outlet 18 and the oil level observation port 22 are welded on the outside, and the two ends of the water tank sealing plate 19 are welded at the same time. All the welding is required to be leak-proof. After welding, the whole is heated and annealed. The casing 1 is respectively subjected to outer circle fine turning, inner circle fine turning, drilling in the machining center, surface anti-rust blackening treatment, and ventilation test sealing;

[0048] S2, the stator core 23 is installed on the casing 1; first, the casing 1 is heated to a high temperature to make the casing 1 expand, and the stator core 23 is inserted or pressed into the casing 1, and the sleeved stator core 23 and the casing 1 are placed indoors for cooling, and the next step is performed after the temperature drops to room temperature;

[0049] S3, the rear end cover 3 of the motor is fixed on the casing 1; the rotor 5 of the motor is first installed on the front end cover 4 inside the motor, and then pressed into the stator 2. The front end cover 4 inside the motor is fixed on the front end cover mounting plate 15, and the front end cover 4 inside the motor is made oil-proof and waterproof through a sealing ring.

[0050] S4, the planetary reducer sun gear 7 is installed on the motor shaft 6: the motor shaft 6 adopts a spline method, and the planetary reducer sun gear 7 adopts an internal spline plus an external spline method, and the two are connected and pressed with a gland;

[0051] S5. Apply a circle of high-temperature sealant on the inner side of the reducer output end cover 10, align the planetary reducer planetary gear 8 with the planetary reducer sun gear 7 on the motor shaft 6, and install it into the housing 1. There are two positioning joints in the housing 1. The inner positioning joint controls the input end accuracy of the reducer, and the outer positioning joint controls the output end accuracy of the reducer. The reducer output end cover 10 is fixed on the housing 1 and directly serves as the output end of the integrated machine;

[0052] S6. Add gear lubricating oil through the planetary gear oil filling port 20 on the housing 1, and let it flow in through the oil hole 13. Stop adding oil when the amount of oil exceeds the oil level observation port 22. Fix the oil filling port with a vent cap. After all parts are installed, the entire integrated machine can be operated. During operation, coolant needs to be introduced into the housing 1.

[0053] The above-mentioned motor and planetary reducer integrated device and its manufacturing method have the following practical effects:

[0054] 1. The motor and planetary reducer are integrated, with compact structure, small size and light weight;

[0055] 2. The housing 1 adopts a liquid cooling structure to directly cool the motor and planetary reducer, so that the heat generation is low, the cooling effect is good, and the structure is simple;

[0056] 3. The planetary reducer sun gear 7 is directly mounted on the motor shaft 6 of the rotor 5 and directly inserted into the planetary reducer planetary gear 8, making it compact in structure, high in rotation accuracy and low in noise;

[0057] 4. The motor and planetary reducer have high operating efficiency and low energy consumption;

[0058] 5. The stator 2 is directly cooled by the cooling structure on the housing 1. The planetary belt reducer is lubricated by the gear lubricant and transmits the temperature to the motor housing, and then cooled by the motor cooling structure, so that the cooling structure is simplified, the cooling is uniform, the temperature drops quickly, the operation efficiency is high and the energy consumption is low;

[0059] 6. The entire technical solution has a compact structure, simple transmission, and convenient maintenance. The system efficiency, rotation accuracy, position accuracy, and service life are greatly improved, and the heat generation and operating noise are greatly reduced.

[0060] Embodiment 2

[0061] The second embodiment is roughly the same as the first embodiment, except that in step S1, the end cover mounting plate needs to be chamfered at a 45° angle before welding and close to the inner circle positioning port of the housing 1. The welding points are uniform, without pores and welds. To ensure strength, the width of the welding points is 8-10mm. After welding, the whole is heated to 575-625°C. The heating temperature of this embodiment can be 600°C, and the holding time is 1 hour for annealing every 25mm thickness to eliminate the residual stress generated by the welding process; the outer circle of the housing 1 is finely turned, and the accuracy requirement is <0.05mm, the inner circle of the housing 1 is finely turned, and the accuracy requirement is <0.02mm. The machining center punches holes with an accuracy requirement of <0.1mm. The assembly accuracy is guaranteed and the service life is greatly improved.

[0062] Embodiment 3

[0063] The third embodiment is substantially the same as the first embodiment, except that in step S2, the housing 1 is heated at 180-220°C for 1-3 hours to allow the housing 1 to expand, and the sleeved stator core 23 and the housing 1 are placed indoors for natural cooling or cooling with a fan. The advantage of the interference fit installation after heating is that the equipment used during installation is simple, the accuracy after sleeved is guaranteed to a certain extent, and the general deformation can be controlled within 0.05 mm.

[0064] Embodiment 4:

[0065] In step S2, the casing 1 is heated at 200°C for 2 hours to allow the casing 1 to expand by heat, and the mounted stator core 23 and the casing 1 are cooled by a fan.

[0066] Embodiment 5

[0067] In step S2, the casing 1 is heated at 180°C for 1.5 hours to allow the casing 1 to expand. The mounted stator core 23 and the casing 1 are placed indoors for natural cooling, and then the front and rear stoppers are fine-turned. After fine-turning, the accuracy of the casing is better guaranteed, and the deformation can be controlled within 0.01 mm.

[0068] Embodiment 6

[0069] During operation, the coolant needs to be introduced into the casing 1. The coolant is introduced into the spiral water tank 16 of the casing 1 at a pressure of 3-5kg and a temperature of less than 40°C. The actual cooling effect is determined by the load size and the temperature and flow rate of the coolant in the casing 1. The above parameters are used to ensure the cooling effect and cooling efficiency as much as possible. During normal use, the surface temperature of the casing 1 is controlled within 60°C, the internal temperature of the motor is less than 100 degrees (the F-grade temperature of the motor enameled wire is 155 degrees), and the internal oil temperature of the reducer is less than 70 degrees, which is a better state.

[0070] Embodiment 7

[0071] The motor shaft 6 adopts a spline method. If mass production is required, in order to further improve reliability, the motor spline shaft can be directly made into a sun gear. However, in order to improve accuracy and reduce noise during processing, the gears need to be finely ground, and the gear accuracy must reach level 6 or above.

[0072] The above embodiments are only used to explain the inventive concept of the present invention, rather than to limit the protection of the rights of the present invention. Any non-substantial changes to the present invention using this concept shall fall within the protection scope of the present invention.

Claims

1. A method for manufacturing an integrated motor and a planetary reducer, comprising an integrated device, characterized in that: The integrated device includes a housing, a motor assembly and a planetary reducer assembly. The housing is provided with mounting cavities for the motor assembly and the planetary reducer assembly respectively. The motor assembly and the planetary reducer assembly are in transmission cooperation. A cooling structure is provided on the outer circle of the housing. The cooling structure comprises a spiral water groove arranged on the outer circle of the casing, a coolant inlet and a coolant outlet connected to the spiral water groove, and a water groove sealing plate is arranged on the upper surface of the spiral water groove on the casing; The motor assembly comprises a stator, a rotor, a motor shaft, a motor rear end cover and a motor internal front end cover, the motor rear end cover is fixed to the casing, the rotor is installed in the stator, one end of the rotor is connected to the motor shaft, one end of the stator is connected to the motor rear end cover, and the other end of the stator is connected to the motor internal front end cover, the stator core is interference fit inside the casing, and the stator core is provided with a motor winding; The following production steps are also included: S1. Processing of the casing: First, the round steel is roughly turned to the required dimensions of the inner and outer circles, and then the spiral water tank is milled on the outer circle, and the front cover mounting plate is welded inside it. Then, the coolant inlet, coolant outlet and oil level observation port are welded on the outside, and the two ends of the water tank sealing plate are welded at the same time. All welding is required to be leak-proof. After welding, the whole is heated and annealed. The casing is respectively processed by outer circle fine turning, inner circle fine turning, drilling in the machining center, rust-proof blackening treatment on the surface, and ventilation test and sealing; S2. The stator core is installed on the casing. First, the casing is heated to a high temperature to expand the casing, and the stator core is inserted or pressed into the casing. The inserted stator core and casing are placed indoors for cooling. After the temperature drops to room temperature, the next step is performed. S3, the rear end cover of the motor is fixed on the casing; the rotor of the motor is first installed on the front end cover inside the motor, and then pressed into the stator. The front end cover inside the motor is fixed on the front end cover mounting plate, and the front end cover inside the motor is made oil-proof and waterproof through a sealing ring; S4. The sun gear of the planetary reducer is installed on the motor shaft: the motor shaft adopts the spline method, and the sun gear of the planetary reducer adopts the internal spline plus external spline method. The two are connected and tightened with a gland; S5. Apply a circle of high-temperature sealant on the inner side of the reducer output end cover, align the planetary reducer planetary gear with the planetary reducer sun gear on the motor shaft, and install it into the casing. There are two positioning joints in the casing. The inner positioning joint controls the input end accuracy of the reducer, and the outer positioning joint controls the output end accuracy of the reducer. The reducer output end cover is fixed on the casing and directly used as the output end of the integrated machine. S6. Add gear lubricating oil through the planetary gear oil filling port on the casing. Stop adding oil when the amount exceeds the oil level observation port. Fix the oil filling port with a vent cap. After all parts are installed, the entire integrated machine can be operated. During operation, coolant needs to be introduced into the casing.

2. The method for manufacturing an integrated motor and planetary reducer according to claim 1, characterized in that: In step S1, the end cover mounting plate needs to be chamfered at a 45° angle before welding and close to the inner circle positioning port of the casing. The welding points are uniform and the width of the welding points is 8-10mm. After welding, the whole is heated to 575-625℃ and the holding time is 1 hour for annealing for every 25mm thickness. The outer circle of the casing is fine-turned with an accuracy requirement of <0.05mm, the inner circle of the casing is fine-turned with an accuracy requirement of <0.02mm, and the drilling is performed by the machining center with an accuracy requirement of <0.1mm.

3. The method for manufacturing an integrated motor and planetary reducer according to claim 1, characterized in that: In step S2, the casing is heated at 180-220° C. for 1-3 hours to allow the casing to expand by heat, and the mounted stator core and casing are placed indoors for natural cooling or cooling by a fan.

4. The method for manufacturing an integrated motor and planetary reducer according to claim 1, characterized in that: In step S6, the coolant is introduced into the casing. The coolant is introduced into the spiral water tank of the casing at a pressure of 3-5kg and a temperature of less than 40°C.

5. The method for manufacturing an integrated motor and planetary reducer according to claim 1, characterized in that: The planetary reducer assembly comprises a planetary reducer assembly housing, a planetary reducer sun gear and a planetary reducer planetary gear. The planetary reducer sun gear is mounted on the motor shaft and directly inserted into the planetary reducer planetary gear.

6. The method for manufacturing an integrated motor and planetary reducer according to claim 1, characterized in that: The output end face of the casing is provided with a reducer output end cover and an output flange, and the interior of the casing is provided with a front end cover mounting plate.

7. The method for manufacturing an integrated motor and planetary reducer according to claim 1, characterized in that: The opposite surfaces of the casing are respectively provided with a planetary gear oil filling port and a planetary gear oil drain port, and are also provided with a plurality of oil level observation ports.

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