CN206611294U - A kind of transmission mechanism is built in the external rotor brushless reducing motor of stator - Google Patents

Abstract

A kind of transmission mechanism is built in the external rotor brushless reducing motor of stator, including：Stator group part, stator module includes the iron core outside a bore of stator and the ring gear and bore of stator that are arranged on inside bore of stator；One rotor assembly, the rotor assembly includes having a sun gear at an inner space defined by rotor assembly, the inner space axial centre, and inner space the week side of boss is provided with magnet corresponding with iron core；One gear-driven assembly, the gear-driven assembly includes one and is placed in the planetary gear and planet carrier used cooperatively inside bore of stator and with sun gear.The remaining space at front motor cover center is make use of, planetary gear train transmission component is built in motor.In the case of the volume of motor in itself is not influenceed, parts are reduced, mitigate motor weight, make motor torsion by planetary gear train transmission component conversion increase several times, increase the moment of torsion and load-carrying ability of motor, motor effective rate of utilization is not fully exerted, make that motor center of gravity is more steady, movement inertia is smaller.

Description

A kind of transmission mechanism is built in the external rotor brushless reducing motor of stator

Technical field

The utility model belongs to machine field, and the external rotor brushless that more particularly to a kind of transmission mechanism is built in stator slows down Motor.

Background technology

Reducing motor refers to the conglomerate of decelerator and motor.External rotor brushless reducing motor is by external rotor brushless direct current Machine and gear reduction unit composition.

Traditional external rotor brushless reducing motor structure, is that gear-box is placed in outside motor, by front motor cover mounting surface with Gear-box connecting plate is docked, and be combined into one work.Integrated motor total height and volume are all than larger, and weight compares heavier. Therefore, cause reducing motor center of gravity and the distance of mounting surface to become big, in use, power of motor loss, increase can be increased Motor moves integrally inertia, and to requirements of installation space increase.Due to structural factor, the use of motor is very limited, The motor of same volume size is reached after certain loading capacity, will be unable to increase moment of torsion and own load ability, motor performance again Utilization rate is not fully exerted.

And the front motor cover center of outer rotor brushless DC motor is empty, its inner space is not utilized effectively, single The load of individual motor is relatively small, limited using field.

Utility model content

The utility model aims to solve the problem that prior art defect, it is therefore an objective to provides one kind and makes full use of motor internal space, contracting Small machine volume, the weight that mitigates, strong reduce motor mass motion inertia, load capacity, motor performance effective rate of utilization height, energy-conservation External rotor brushless reducing motor built in environmentally friendly, reliable, long-life travelling gear.

To reach above-mentioned purpose, there is provided following technical scheme：

A kind of transmission mechanism is built in the external rotor brushless reducing motor of stator, including：

Stator group part, the stator module includes a bore of stator and the ring gear being arranged on inside bore of stator and fixed The iron core of sub- lumen outer；

One rotor assembly, the rotor assembly includes an inner space defined by rotor assembly, the inner space axle There is a sun gear to center, inner space the week side of boss is provided with magnet corresponding with iron core；

One gear-driven assembly, the gear-driven assembly, which is placed in inside bore of stator and coordinated with sun gear including one, to be made Planetary gear and planet carrier.

Further, the stator module includes：Front motor cover, ring gear, iron core and clutch shaft bearing, the front motor cover Including a lid and one first ring body, connected between the lid and the first ring body by multiple first beam bodies, in the lid The heart sets one first axis hole, and the clutch shaft bearing is arranged in first axis hole, and the lid side sets a bore of stator, The ring gear is arranged at the bore of stator inwall close to lid side, and the ring gear is fixed on bore of stator with bearing pin Interior, the iron core is arranged at the outer wall of the bore of stator.

Further, the iron core is fixed on the outer wall of the bore of stator using lock-screw.

Further, the rotor assembly includes：Motor rear cover, built-up shaft, casing, magnet, sun gear and second bearing, The motor rear cover includes one second ring body and the 3rd ring body, and the 3rd ring body diameter is more than the second ring body diameter, institute State by the connection of multiple second beam bodies between the second ring body and the 3rd ring body, the 3rd ring body end face circumferentially sets multiple Projection, the casing is connected with the 3rd ring body periphery, and the casing defines an inner space jointly with the motor rear cover, Multiple magnets are arranged at the casing inner wall and are connected with the projection, and sky is left between the magnet and the iron core Gap, centrally disposed one second axis hole of built-up shaft, the second bearing is arranged in second axis hole, the built-up shaft one Hold as flange and be fixed on the second ring body side, the built-up shaft other end is that multi-diameter shaft passes through second ring body, institute State sun gear and be sheathed on the multi-diameter shaft away from described flange one end.

Further, the gear-driven assembly includes：Planet carrier, wheel shaft, planetary gear, needle roller and retainer component and row Carrier flange, the planet carrier is discoid, and a round boss is set on the planet carrier end face, and the round boss is set Coordinate in the clutch shaft bearing and with the clutch shaft bearing, the centrally disposed output shaft in planet carrier other end is described Output shaft sets a step away from described planet carrier one end, and the output shaft is extended outside motor through the second bearing, described Second bearing and the step of the output shaft coordinate, the multiple mounting holes of annular array centered on the output shaft, the wheel shaft One end is arranged in the mounting hole, and the planetary gear is sheathed on the wheel shaft, the wheel shaft other end and the planet carrier Flange end face is connected, and the planetary gear outer ring is engaged with the ring gear, and the planetary gear inner ring is with being sheathed on the ladder Sun gear engagement on axle.

Further, the needle roller and retainer component are set between the planetary gear and the wheel shaft.

Further, the gear-driven assembly also includes axle card and pad, and the axle card and pad are set on the circle On shape boss, the pad is located remotely from planet carrier side.

Further, the reducing motor also includes the first seal assembly, and first seal assembly includes baffle plate and close Capping, the baffle plate is fixed on the one end of the round boss in contrast to the planet carrier, the closure using screw and set Put circular groove and accommodate the baffle plate, closure side wall is provided with screw thread, and first axis hole is away from the bore of stator one The screw thread cooperation that end is threaded with the closure is screwed.

Further, the reducing motor also includes the second seal assembly, and second seal assembly includes bearing block, the Three bearings and the first oil sealing, the bearing block are arranged at the carrier flange other end, the bearing block centrally disposed one Shoulder hole, first oil sealing is arranged in the shoulder hole is relatively large in diameter side, the described 3rd close to the carrier flange Bearing is arranged in the shoulder hole away from the smaller side of carrier flange diameter, and the multi-diameter shaft passes through the 3rd axle Hold and coordinate with the 3rd bearing.

Further, the reducing motor also includes the 3rd seal assembly, and the 3rd seal assembly includes back-up ring and the Two oil sealings, the shield ring sleeve is passed at second axis hole located at the output shaft, and second oil-sealing sleeve is located at the output On axle on the outside of back-up ring, the second oil sealing outer ring and second shaft hole matching.

The beneficial effects of the utility model：

1st, small volume, power effective rate of utilization that is lightweight, improving motor；

Planetary gear train transmission component is arranged in front motor cover in the utility model, made full use of empty inside front motor cover Between；Gear box structure is saved simultaneously, motor height is substantially reduced, reduces motor volume；Amount of parts is reduced, weight is alleviated Amount.Due to the reduction of weight and volume so that motor effective power is fully used.

2nd, compact conformation, mobile inertia are small, and load is big, improves the operational reliability of motor；

Sun gear is pressed together on motor rear cover in the utility model, and ring gear is fixed on bore of stator inwall, and planet carrier is defeated Shaft is connected with motor rear cover by bearing precision, the output shaft of planet carrier output shaft not only as planetary gear train transmission component, Rotor axis of electric is functioned simultaneously as to use.This structure design reduces parts, and space availability ratio is high, compact conformation；It is more important Be weight saving, steadily of centre of gravity, motor is moved integrally inertia and diminish, power is strengthened, the characteristics of due to gear drive so that Load capacity increases, and power of motor utilization rate is improved.

3rd, increase functional reliability, extend the life-span；

Install needle roller and retainer component between planetary gear and wheel shaft additional, improve machine driving precision, strengthen planetary gear Transmission accuracy, makes that the transmission of gear is more smooth, and reliability of operation is higher, and the life-span is longer.

4th, using the connection of lock-screw fixed stator iron core and front motor cover, using more reliable；Traditional structure：Use glue Stator core and front motor cover are bonded together by water, and because motor is under long term high temperature operation, glue can fail, and cause stator Release, influence operational reliability and the life-span of motor.The utility model mainly solves this technological deficiency.

5th, motor gearing structure, using oil lubrication, reduces mechanical wear, improves motor service life and reliable Property.Traditional structure is to use grease lubrication, because motor after running after a while, lubricating grease deterioration failure, each machine Lubrication, mechanical wear aggravation are lost between tool structure.The utility model mainly solves this technological deficiency, using oil sealing sealing, Using oil lubrication, because lubricant movement ratio of viscosities lubricating grease is low, mechanical loss is greatly reduced, motor Effective power is improved Rate utilization rate.

6th, front motor cover and motor rear cover vents design, improve the effective power utilization rate of motor.

Drive mechanism is designed using closed front motor bonnet, and the design uses vents design, is primarily due to improve The heat-sinking capability of motor, under high-speed cruising, fully contacts extraneous medium, improves motor heat and expands thermal velocity, reduction motor Heating loss.

7th, rotor electric machine bonnet and built-up shaft carry out split design, can be used unlike material, ingenious sharp different materials it is excellent More characteristic, it is ensured that the weight and intensity of motor are in optimum state.Drive mechanism uses aluminium using axle and end cap integrated design Alloy or steel alloy, due to the influence of the strength of materials.Often there is off-axis phenomenon in motor.The utility model is in order to solve this Technological deficiency, axle is designed with steel alloy, using split type, makes full use of the characteristic and aluminium alloy of steel alloy high intensity lightweight Advantage, solves the phenomenon of break motor bearing so that running reliability of motor is improved.

Brief description of the drawings

Fig. 1 is the utility model Structure explosion diagram；

Fig. 2 is the utility model stator member structure explosive view；

Fig. 3 is the utility model rotor component construction explosive view；

Fig. 4 is the utility model gear-driven assembly Structure explosion diagram.

Element corresponding to each sequence number is as follows：

Stator module 1；

Front motor cover 11；

Lid 111；

First axis hole 1111；

Bore of stator 1112；

First ring body 112；

First beam body 113；

Ring gear 12；

Iron core 13；

Clutch shaft bearing 14；

Rotor assembly 2；

Motor rear cover 21；

Second ring body 211；

3rd ring body 212；

Projection 2121；

Second beam body 213

Built-up shaft 22；

Second axis hole 221

Casing 23；

Magnet 24；

Sun gear 25

Second bearing 26；

Gear-driven assembly 3；

Planet carrier 31；

Round boss 311；

Output shaft 312；

Step 3121；

Mounting hole 313；

Wheel shaft 32；

Planetary gear 33；

Needle roller and retainer component 34；

Carrier flange 35；

Axle card 36；

Pad 37；

First seal assembly 4；

Baffle plate 41；

Closure 42；

Sealing ring 43；

Second seal assembly 5；

Bearing block 51；

3rd bearing 52；

First oil sealing 53；

3rd seal assembly 6；

Back-up ring 61；

Second oil sealing 62.

Embodiment

In order that the purpose of this utility model, technical scheme and advantage are more clearly understood, below in conjunction with accompanying drawing and implementation Example, the utility model is explained in further detail.It should be appreciated that it is described herein with shaft hole matching is combined into, retouched The specific embodiment stated is only used for explaining the utility model, is not used to limit the utility model.

On the contrary, the utility model cover it is any be defined by the claims do in spirit and scope of the present utility model Replacement, modification, equivalent method and scheme.Further, it is right below in order that the public has a better understanding to the utility model It is detailed to describe some specific detail sections in detailed description of the present utility model.

As Figure 1-4, a kind of transmission mechanism is built in the external rotor brushless reducing motor of stator, including：Stator group Part 1, the stator module 1 is included in a bore of stator 1112 and the ring gear 12 and stator that are arranged on inside bore of stator 1112 Iron core 13 outside chamber 1112, the bore of stator 1112 is sleeve-like configuration；

One rotor assembly 2, the rotor assembly 2 includes an inner space defined by rotor assembly 2, the inner space There is a sun gear 25, inner space the week side of boss is provided with magnet 24 corresponding with iron core 13 at axial centre；

One gear-driven assembly 3, the gear-driven assembly 3 is placed in inside bore of stator 1112 and and the sun including one Planetary gear 33 and planet carrier 31 that wheel 25 is used cooperatively.

The stator module 1 includes：Front motor cover 11, ring gear 12, iron core 13 and clutch shaft bearing 14, the front motor cover 11 include passing through multiple first beam bodies between a lid 111 and one first ring body 112, the ring body 112 of lid 111 and first 113 connections, centrally disposed one first axis hole 1111 of lid 111, the clutch shaft bearing 14 is arranged at first axis hole In 1111, the side of lid 111 sets a bore of stator 1112, and the ring gear 12 is arranged in the bore of stator 1112 Wall is fixed in bore of stator 1112 close to the side of lid 111, the ring gear 12 with bearing pin, and the iron core 13 uses locking screw Nail is fixed on the outer wall of the bore of stator 1112.

The rotor assembly 2 includes：Motor rear cover 21, built-up shaft 22, casing 23, magnet 24, the axle of sun gear 25 and second 26 are held, the motor rear cover 21 includes one second ring body 211 and the 3rd ring body 212, the diameter of the 3rd ring body 212 is more than described Connected between the diameter of second ring body 211, the ring body 212 of the second ring body 211 and the 3rd by multiple second beam bodies 213, it is described The end face of 3rd ring body 212 circumferentially sets multiple raised 2121, and the casing 23 is connected with the periphery of the 3rd ring body 212, The casing 23 defines an inner space jointly with the motor rear cover 21, and multiple magnets 24 are arranged in the casing 23 Wall is simultaneously connected with described raised 2121, and space is left between the magnet 24 and the iron core 13, and the center of built-up shaft 22 is set One second axis hole 221 is put, the second bearing 26 is arranged in second axis hole 221, described one end of built-up shaft 22 is flange And the side of the second ring body 211 is fixed on, the other end of built-up shaft 22 is that multi-diameter shaft passes through second ring body 211, institute State sun gear 25 and be sheathed on the multi-diameter shaft away from described flange one end, the sun gear 25 is matched somebody with somebody with the gear-driven assembly 3 Close.

The gear-driven assembly 3 includes：Planet carrier 31, wheel shaft 32, planetary gear 33, needle roller and retainer component 34 and row Carrier flange 35, the planet carrier 31 is discoid, and a round boss 311, the circle are set on the end face of planet carrier 31 Shape boss 311 is arranged in the clutch shaft bearing 14 and coordinated with the clutch shaft bearing 14, in the other end of planet carrier 31 The heart sets an output shaft 312, and the output shaft 312 sets a step 3121, the output shaft away from described one end of planet carrier 31 312 extend outside motor through the second bearing 26, and the second bearing 26 and the step 3121 of the output shaft 312 coordinate, The multiple mounting holes 313 of annular array centered on the output shaft 312, described one end of wheel shaft 32 is arranged at the mounting hole 313 Interior, the planetary gear 33 is sheathed on the wheel shaft 32, set between the planetary gear 33 and the wheel shaft 32 needle roller with Retainer component 34, the other end of wheel shaft 32 is connected with the end face of carrier flange 35, the outer ring of planetary gear 33 with The ring gear 12 is engaged, and the inner ring of planetary gear 33 is engaged with the sun gear 25 being sheathed on the multi-diameter shaft, the planet Take turns on the outside of the virtual gear ring that the planetary gear 33 that 33 outer rings are multiple annular arrays is constituted, the inner ring of planetary gear 33 is multiple annulars On the inside of the virtual gear ring that the planetary gear 33 of array is constituted, the gear-driven assembly 3 also includes axle card 36 and pad 37, the axle Card 36 and pad 37 are set on the round boss 311, and the pad 37 is located remotely from the side of planet carrier 31, and the gear is passed Dynamic component 3 uses oil lubrication.

The reducing motor also includes the first seal assembly 4, the second seal assembly 5 and the 3rd seal assembly 6, described first Seal assembly 4 includes but is not limited to baffle plate 41 and closure 42, and the baffle plate 41 is fixed on the round boss 311 using screw One end in contrast to the planet carrier 31 is accommodated to fix setting circular groove on the clutch shaft bearing 14, the closure 42 The baffle plate 41, the side wall of closure 42 is provided with screw thread, and first axis hole 1111 is away from described one end of bore of stator 1112 The screw thread being threaded with the closure 42, which coordinates, to be screwed, the inner side that the closure 42 is spirally connected with first axis hole 1111 A settable sealing ring 43, the closure 42 compresses the sealing ring 43.Second seal assembly 5 includes but is not limited to Bearing block 51, the oil sealing 53 of 3rd bearing 52 and first, the bearing block 51 are arranged at the other end of carrier flange 35, institute The centrally disposed shoulder hole of bearing block 51 is stated, first oil sealing 53 is arranged in the shoulder hole close to the carrier flange 35 are relatively large in diameter side, and the 3rd bearing 52 is arranged in the shoulder hole smaller by one away from the diameter of carrier flange 35 Side, the multi-diameter shaft coordinates through the 3rd bearing 52 and with the 3rd bearing 52.3rd seal assembly 6 includes gear But the oil sealing 62 of circle 61 and second is not limited to, the back-up ring 61 is sheathed on the output shaft 312 and passed at second axis hole 221, Second oil sealing 62 is sheathed on the outside of back-up ring 61 on the output shaft 312, the outer ring of the second oil sealing 62 and second axle Hole 221 coordinates, and the structure of above-mentioned each seal assembly is only the utility model one of which embodiment, and the sealing ring 43 is set Position is not limited, may be provided at it is any realize sealed position, such as on the outside of axis hole, seal assembly also can be replaced sealing Other have the potted component of sealing function for pad, fluid sealant etc., sealed mode can be screwed for screw thread or pressing plate is compressed etc. its He can realize sealed mode, the deformation of any seal form or seal form all should in the utility model protection domain, Using above-mentioned seal assembly can effective waterproof, it is moistureproof, dust-proof.

The beneficial effects of the utility model are, take full advantage of the remaining space at front motor cover center, by planetary gear train Transmission component is built in motor.This structure design reduces parts in the case of the volume of motor in itself is not influenceed, and mitigates electricity Machine weight, makes motor torsion by planetary gear train transmission component conversion increase several times, increases the moment of torsion and load-carrying ability of motor, electricity Machine effective rate of utilization is not fully exerted, and makes that motor center of gravity is more steady, and movement inertia is smaller.

Claims (10)

1. a kind of transmission mechanism is built in the external rotor brushless reducing motor of stator, it is characterised in that including：

Stator group part (1), the stator module (1) includes a bore of stator (1112) and is arranged in bore of stator (1112) The outside iron core (13) of the ring gear (12) and bore of stator (1112) in portion；

One rotor assembly (2), the rotor assembly (2) includes an inner space defined by rotor assembly (2), described internal empty Between axial center there is a sun gear (25), inner space the week side of boss is provided with magnet (24) corresponding with iron core (13)；

One gear-driven assembly (3), the gear-driven assembly (3) is placed in bore of stator (1112) inside and and the sun including one Planetary gear (33) and planet carrier (31) that wheel (25) is used cooperatively.

2. transmission mechanism according to claim 1 is built in the external rotor brushless reducing motor of stator, it is characterised in that institute Stating stator module (1) includes：Front motor cover (11), ring gear (12), iron core (13) and clutch shaft bearing (14), the front motor cover (11) lid (111) and one first ring body (112) are included, by multiple between the lid (111) and the first ring body (112) First beam body (113) is connected, centrally disposed one first axis hole (1111) of lid (111), and the clutch shaft bearing (14) is set In first axis hole (1111), lid (111) side sets a bore of stator (1112), and the ring gear (12) sets The bore of stator (1112) inwall is placed in close to lid (111) side, the ring gear (12) is fixed in stator with bearing pin In chamber (1112), the iron core is arranged at the outer wall of the bore of stator (1112).

3. transmission mechanism according to claim 2 is built in the external rotor brushless reducing motor of stator, it is characterised in that institute State the outer wall that iron core (13) is fixed on the bore of stator (1112) using lock-screw.

4. transmission mechanism according to claim 3 is built in the external rotor brushless reducing motor of stator, it is characterised in that institute Stating rotor assembly (2) includes：Motor rear cover (21), built-up shaft (22), casing (23), magnet (24), sun gear (25) and second Bearing (26), the motor rear cover (21) includes one second ring body (211) and the 3rd ring body (212), the 3rd ring body (212) Diameter is more than the second ring body (211) diameter, passes through multiple the between second ring body (211) and the 3rd ring body (212) Two beam bodies (213) are connected, and the 3rd ring body (212) end face circumferentially sets multiple raised (2121), the casing (23) It is connected with the 3rd ring body (212) periphery, the casing (23) defines an inner space jointly with the motor rear cover (21), Multiple magnets (24) are arranged at the casing (23) inwall and are connected with raised (2121), the magnet (24) and institute State and leave space, centrally disposed one second axis hole (221) of built-up shaft (22), the second bearing (26) between iron core (13) It is arranged in second axis hole (221), described built-up shaft (22) one end is flange and is fixed on second ring body (211) one Side, built-up shaft (22) other end is that multi-diameter shaft passes through second ring body (211), and the sun gear (25) is sheathed on described Multi-diameter shaft is away from described flange one end.

5. transmission mechanism according to claim 4 is built in the external rotor brushless reducing motor of stator, it is characterised in that institute Stating gear-driven assembly (3) includes：Planet carrier (31), wheel shaft (32), planetary gear (33), needle roller and retainer component (34) and row Carrier flange (35), the planet carrier (31) is discoid, and a round boss is set on planet carrier (31) end face (311), the round boss (311) is arranged in the clutch shaft bearing (14) and coordinated with the clutch shaft bearing (14), described The centrally disposed output shaft (312) in planet carrier (31) other end, the output shaft (312) is away from the planet carrier (31) one end One step (3121) is set, and the output shaft (312) is extended outside motor through the second bearing (26), the second bearing (26) step (3121) with the output shaft (312) coordinates, and annular array is multiple centered on the output shaft (312) installs Hole (313), described wheel shaft (32) one end is arranged in the mounting hole (313), and the planetary gear (33) is sheathed on the wheel shaft (32) on, wheel shaft (32) other end is connected with the carrier flange (35) end face, planetary gear (33) outer ring with Ring gear (12) engagement, planetary gear (33) inner ring is engaged with the sun gear (25) being sheathed on the multi-diameter shaft.

6. transmission mechanism according to claim 5 is built in the external rotor brushless reducing motor of stator, it is characterised in that institute State and the needle roller and retainer component (34) are set between planetary gear (33) and the wheel shaft (32).

7. transmission mechanism according to claim 5 is built in the external rotor brushless reducing motor of stator, it is characterised in that institute Stating gear-driven assembly (3) also includes axle card (36) and pad (37), and the axle card (36) and pad (37) are set on the circle On shape boss (311), the pad (37) is located remotely from planet carrier (31) side.

8. transmission mechanism according to claim 5 is built in the external rotor brushless reducing motor of stator, it is characterised in that institute Stating reducing motor also includes the first seal assembly (4), and first seal assembly (4) includes baffle plate (41) and closure (42), The baffle plate (41) is fixed on the one end of the round boss (311) in contrast to the planet carrier (31) using screw, described close Cover and set circular groove to accommodate the baffle plate (41) on (42), closure (42) side wall is provided with screw thread, the first axle Hole (1111) is screwed away from the screw thread cooperation that the bore of stator (1112) one end is threaded with the closure (42).

9. transmission mechanism according to claim 5 is built in the external rotor brushless reducing motor of stator, it is characterised in that institute Stating reducing motor also includes the second seal assembly (5), and second seal assembly (5) includes bearing block (51), 3rd bearing (52) and the first oil sealing (53), the bearing block (51) is arranged at the carrier flange (35) other end, the bearing block (51) a centrally disposed shoulder hole, first oil sealing (53) is arranged in the shoulder hole close to the carrier flange (35) Side is relatively large in diameter, the 3rd bearing (52) is arranged in the shoulder hole smaller away from the carrier flange (35) diameter Side, the multi-diameter shaft coordinates through the 3rd bearing (52) and with the 3rd bearing (52).

10. transmission mechanism according to claim 5 is built in the external rotor brushless reducing motor of stator, it is characterised in that The reducing motor also includes the 3rd seal assembly (6), and the 3rd seal assembly (6) includes back-up ring (61) and the second oil sealing (62), the back-up ring (61) is sheathed on the output shaft (312) and passes the second axis hole (221) place, second oil sealing (62) it is sheathed on the output shaft (312) on the outside of back-up ring (61), the second oil sealing (62) outer ring and second axis hole (221) coordinate.