Drive unit

Abstract

To provide a driving machine that makes it easier to replace grease to prevent rust between an inner peripheral surface of a hollow shaft and an outer peripheral surface of a load shaft.SOLUTION: A driving machine 10 that has a hollow shaft 11 into which a load shaft 3 is inserted, and a power transmission mechanism 12 that transmits power from a power source 4 to the hollow shaft 11, is provided with a communication passage 16 that communicates between a relief groove (gap) 15 that is formed inside the hollow shaft 11 and extends between the hollow shaft 11 and the load shaft 3 over the entire circumference in a circumferential direction of the shaft, and the outside. With the relief groove 15 filled with grease from the outside via the communication passage 16, the hollow shaft 11 and the load shaft 3 are rotated by the power transmitted from the power source 4 via the power transmission mechanism 12.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a driving machine, and more particularly to a driving machine having a hollow shaft into which a load shaft is inserted and a power transmission mechanism that transmits power from a power source to this hollow shaft. [Background technology]

[0002] The inventors of the present application have devised a rotating shaft that is inserted into a through hole of a rotating body and fixed to the through hole, the rotating shaft having a plurality of circumferential grooves extending in the circumferential direction of the shaft and recessed toward the inside in the radial direction of the shaft, each having a C-shaped ring with ends or an O-shaped ring with ends, and a communication passage extending inside the shaft and communicating between the circumferential grooves and the outside of the rotating shaft, the plurality of circumferential grooves being arranged at least one on each of both ends in the axial direction of a shielding part that is covered by the through hole and shielded from the outside, and the rotating shaft rotates together with the rotating body in a state in which the area between the circumferential grooves arranged at both ends is sealed from the outside through the communication passage by grease filled in the plurality of circumferential grooves (see Patent Document 1). This rotating shaft has the excellent effect of preventing rusting of the parts shielded by the through hole and suppressing an increase in resistance when the rotating shaft is removed from the through hole.

[0003] Generally, a hollow shaft (corresponding to the above-mentioned rotating body) of a driving machine such as a reducer or a transmission is fixed to a load shaft (corresponding to the above-mentioned rotating shaft) by a method of fixing an end plate, a spacer, or a hole retaining ring to one end of the load shaft with a bolt. In the invention described in Patent Document 1, since one end of the communication passage is structured to open to one end of the load shaft, when replacing the internal grease, it is necessary to loosen the bolt and remove the end plate, the spacer, or the hole retaining ring. Therefore, the process required for replacing the internal grease is troublesome. Thus, there is room for improvement in order to make it easier to replace the internal grease. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 7038465 Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide a driving machine which makes it easier to replace grease that prevents rust on the inner peripheral surface of the hollow shaft and the outer peripheral surface of the load shaft. [Means for solving the problem]

[0006] The driving machine of the present invention, which achieves the above object, has a hollow shaft into which a load shaft is inserted and a power transmission mechanism that transmits power from a power source to the hollow shaft. The hollow shaft and the load shaft are fixed together by fastening a hole retaining ring and a spacer or an end plate to the tip of the load shaft with a bolt. In the driving machine, the hollow shaft is formed inside the hollow shaft. The hollow shaft has a communicating passage, one end of which is open at the tip of the hollow shaft and the other end of which is A gap extending over the entire circumference in the axial circumferential direction between the hollow shaft and the load shaft By communicating with the gap, and the outside And, The present invention is characterized in that, with grease being filled into the gap from the outside through the communicating passage, the hollow shaft and the load shaft rotate due to power transmitted from the power source through the power transmission mechanism. Effect of the Invention

[0007] According to the present invention, by providing the hollow shaft with a communication passage, it is possible to arrange the open end of the communication passage at a location that is not blocked by an end plate for fixing the load shaft to the hollow shaft, or a spacer or a hole retaining ring. This makes it possible to fill the gap between the hollow shaft and the load shaft with grease through the communication passage, and the gap can be sealed with grease. This prevents rust on the inner peripheral surface of the hollow shaft and the outer peripheral surface of the load shaft, and suppresses an increase in resistance when removing the load shaft from the hollow shaft, while making it easier to replace the grease filled to prevent rust. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is an explanatory diagram illustrating a first embodiment of a driving machine. [Diagram 2]2 is an explanatory diagram illustrating a perspective shape of the hollow shaft of FIG. 1; [Diagram 3] 2 is an explanatory view illustrating a cross section of the hollow shaft of FIG. 1. [Figure 4] FIG. 11 is an explanatory view illustrating a cross section of a hollow shaft of a second embodiment of a driving machine. [Diagram 5] FIG. 2 is an explanatory diagram illustrating a cross section of a hollow shaft of a reference example of a driving machine. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment of the driving machine of the present invention will be described with reference to the drawings. In the drawings, the X direction is the axial direction of the hollow shaft 11, the Z direction is the vertical direction, and the Y direction is the direction perpendicular to the X and Z directions. In addition, in the drawings, the left side of the X direction is the tip side, and the right side is the end side. In the following, the inside and outside refer to the inside and outside in the axial radial direction of the hollow shaft 11.

[0010] The first embodiment of the driving machine 10 illustrated in FIG. 1 transmits power from a power source 4 to a load shaft (drive shaft, axle) 3 of a wheel 2 of a traveling device 1 arranged at the lower end of a crane structure. The crane may be any of various known cranes, including a quay crane or a gantry crane that handles containers at a container terminal, and an unloader that handles bulk cargo such as iron ore or coal. The wheel 2 may be any of various known wheels, and is not limited to a wheel having a flange and rolling on a rail 5, but may be a wheel having a rubber tire and rolling on the ground. The power source 4 may be any known power source such as an internal combustion engine or an electric motor. The driving machine 10 is not limited to a traveling device 1 of a crane, and may also be applicable to a trolley of a crane.

[0011] The driving machine 10 may be any of various known orthogonal-shaft type reducers or transmissions having a hollow shaft 11 into which the load shaft 3 is inserted. Depending on the power transmission method of the power transmission mechanism 12, the driving machine 10 may be, for example, a parallel shaft gear reducer, a helical reducer, a worm reducer, a bevel gear reducer, a hypoid reducer, a planetary gear reducer, or a cycloid drive reducer, or a parallel shaft gear type transmission, a planetary gear type transmission, or a continuously variable transmission.

[0012] The hollow shaft 11 is fixed to the load shaft 3 by fastening a bolt 8 to the load shaft 3 via a hole retaining ring 6 and a spacer 7 arranged on the tip side. If the load shaft 3 has a step, an end plate may be used instead of the hole retaining ring 6 and the spacer 7.

[0013] 2 has an axial direction oriented in the X direction, and has a circular cross-sectional shape in the YZ plane, and the load shaft 3 is inserted into the hollow hole 13. The hollow shaft 11 has a key groove 14, a relief groove 15, a communicating passage 16, and a retaining ring groove 17.

[0014] The keyway 14 may be any of various known keyways. The keyway 14 is disposed at a position facing the keyway 9 formed in the load shaft 3 in the axial direction. The keyway 14 extends in the X direction and is recessed from the axial direction inward to the axial direction outward. The keyway 9 of the load shaft 3 extends in the X direction and is recessed from the axial direction outward to the axial direction inward. A key 20 is fitted into the keyway 9 of the load shaft 3 facing the keyway 14. By fitting the key 20, the load shaft 3 and the hollow shaft 11 are fastened, and power is efficiently transmitted between the load shaft 3 and the hollow shaft 11. The key 20 is not limited to a sunken key, and a crescent key or a sliding key is also exemplified, and the groove shapes of the keyway 14 and the keyway 9 of the load shaft 3 may be any shape corresponding to the shape of the key 20. The keyway 14 is not essential, and in the case of a structure not using the key 20, the keyway 14 and the keyway 9 of the load shaft 3 are not formed. Furthermore, the number of key grooves 14 is not limited to one, and a plurality of key grooves may be formed.

[0015] The relief groove 15 may be any of various known relief grooves. The relief groove 15 is disposed in the central portion of the inner peripheral surface of the hollow shaft 11 in the X direction and extends over the entire circumference in the axial circumferential direction. The relief groove 15 is recessed from the inside toward the outside in the axial radial direction. The relief groove 15 is a groove for reducing resistance when the load shaft 3 is inserted into the hollow hole 13 of the hollow shaft 11. The relief groove 15 communicates with the key groove 14 when the key groove 14 is formed. The state in which the relief groove 15 extends over the entire circumference in the axial circumferential direction also includes the case in which the relief groove 15 communicates with the key groove 14. The relief groove 15 corresponds to the gap of the present invention since it extends over the entire circumference in the axial circumferential direction between the hollow shaft 11 and the load shaft 3.

[0016] The communication passage 16 is formed inside the hollow shaft 11 and is a passage filled with grease. The inside of the hollow shaft 11 does not refer to the hollow hole 13, which is the inner part of the hollow shaft 11, but refers to the inner part of the annular body. The communication passage 16 communicates the clearance groove 15, which is a gap extending over the entire circumference in the axial direction between the hollow shaft 11 and the load shaft 3, with the outside. The outside in this disclosure refers to the outside of the hollow shaft 11, but is not limited to only the space around the hollow shaft 11, and also includes a device connected to the hollow shaft 11 excluding the load shaft 3. For example, it may be the power transmission mechanism 12. It may also be a grease supply device that can supply grease pressurized by a pump to the communication passage 16 and collect grease discharged from the communication passage 16.

[0017] At least one communication passage 16 may be formed in the hollow shaft 11, but it is preferable that a plurality of communication passages 16 are formed in the hollow shaft 11. The plurality of communication passages 16 communicate with each other via a clearance groove (gap) 15. The plurality of communication passages 16 are preferably arranged at a distance from the keyway 14 in the circumferential direction of the shaft, and are preferably arranged at a distance from each other in the circumferential direction of the shaft. The plurality of communication passages 16 are preferably arranged at an angle of 90 degrees or more from the keyway 14 in the circumferential direction of the shaft, and are preferably arranged at an angle of 90 degrees or more from each other in the circumferential direction of the shaft. For example, one keyway 14 and two communication passages 16 may be arranged at equal intervals in the circumferential direction of the shaft. In this way, the plurality of communication passages 16 communicate with each other via the clearance groove 15, so that one communication passage 16 can be used for filling grease and the other communication passage 16 can be used for discharging grease. This is advantageous in terms of ease of replacement of grease. Two or more communication passages 16 may be provided.

[0018] The communication passage 16 extends from the tip opening 18 to the end opening 19. The tip opening 18 opens on the tip surface of the hollow shaft 11. The tip surface of the hollow shaft 11 is preferably a surface that does not have any equipment facing the tip surface. The tip surface of the hollow shaft 11 in this embodiment does not have any equipment facing it, and such equipment does not interfere with the filling of the grease into the communication passage 16. In addition, the tip opening 18 is preferably opened in the X direction (axial direction of the hollow shaft 11). If the tip opening 18 opens in a direction intersecting the X direction, the grease filled in the communication passage 16 may be scattered from the tip opening 18 to the outside due to the action of centrifugal force when the hollow shaft 11 rotates. Therefore, by having the tip opening 18 open in the X direction, it is advantageous to prevent the grease from scattering to the outside due to the action of centrifugal force when the hollow shaft 11 rotates. The end opening 19 opens on the groove bottom surface of the relief groove 15. The position of the end opening 19 is not particularly limited as long as it is on the bottom surface of the clearance groove 15 .

[0019] The retaining ring groove 17 is a groove into which the outer periphery of the hole retaining ring 6 is fitted, and a known retaining ring groove can be used. The retaining ring groove 17 is recessed from the inside to the outside of the hollow hole 13.

[0020] FIG. 3 shows the filling and discharging of grease through the communication passage 16 in the cross section of the hollow shaft 11 and the load shaft 3. In the figure, the filling of new grease is indicated by an outline arrow, and the discharging of old grease is indicated by a filled arrow. In the grease replacement work, the grease filled in the relief groove 15 and the plurality of communication passages 16 is replaced by utilizing the fact that the plurality of communication passages 16 communicate with each other through the relief groove 15. First, new grease is injected from the tip opening 18 of one of the communication passages 16. Next, the injected new grease is supplied to the relief groove 15 through the communication passage 16. When the new grease is supplied, the old grease is pushed out from the relief groove 15 and discharged to the outside through the tip opening 18 of the other communication passage 16 through the other communication passage 16. The discharged old grease is collected. In this way, in the series of grease replacement work, it is not necessary to remove the hole retaining ring 6, the spacer 7, and the bolt 8.

[0021] The removal operation of the load shaft 3 from the hollow shaft 11 includes the following steps. First, the grease filled in the relief groove 15 and the communication passage 16 is washed and removed (first step). Next, a penetrating lubricant is injected from the tip opening 18 of the communication passage 16 (second step). Next, in a state in which the injected penetrating lubricant has permeated the entire area of ​​the hollow hole 13 via the key groove 14, the relief groove 15, and the communication passage 16, the bolt 8 is released and the hole retaining ring 6 and the spacer 7 are removed. Next, the load shaft 3 is removed from the hollow shaft 11 (third step). A penetrating lubricant is a lubricant that has a higher penetrating property than grease and forms a chemical film on the metal surface. An example of a penetrating lubricant is a mixture of a penetrating oil and a rust inhibitor with a water-displacing oil. Another example of a penetrating lubricant is one that is sprayed by an aerosol product. If the load shaft 3 can be removed from the hollow shaft 11 without using a penetrating lubricant, the second step may be omitted.

[0022] As described above, according to this embodiment, by connecting the escape groove 15 to the outside through the communication passage 16, it is possible to inject grease into the escape groove 15 from the outside and fill the escape groove 15 with grease. This is therefore advantageous in preventing the intrusion of moisture such as rainwater or humidity from the outside into the escape groove 15, and it is possible to suppress the occurrence of rust due to the intruded moisture. Accordingly, it is possible to suppress an increase in resistance when removing the load shaft 3 from the hollow shaft 11.

[0023] In addition, according to this embodiment, since the hollow shaft 11 has the communication passage 16, it is possible to arrange the tip opening 18 of the communication passage 16 at a location that is not blocked by the spacer 7 or the hole retaining ring 6 for fixing the load shaft 3 and the hollow shaft 11. Therefore, the grease can be replaced without removing the spacer 7 or the hole retaining ring 6. This can significantly reduce the effort required for the grease replacement work compared to a configuration in which a communication passage is formed in the load shaft 3. As a result, this embodiment is configured to prevent rusting of the inner circumferential surface of the hollow shaft 11 and the outer circumferential surface of the load shaft 3 and suppress an increase in resistance when removing the load shaft 3 from the hollow shaft 11, while making it easier to replace the grease filled to prevent rusting.

[0024] According to this embodiment, the hollow shaft 11 has a plurality of communication passages 16, and the communication passages 16 communicate with each other via the relief grooves 15, so that one communication passage 16 can be used as a supply passage for new grease and the other communication passage 16 can be used as a discharge passage for old grease. Therefore, it is possible to periodically replace grease that deteriorates over time without removing the load shaft 3 from the hollow shaft 11, and it is possible to avoid a decrease in the rust prevention effect due to the deterioration of the grease over time. In addition, the time required for the grease replacement work can be significantly reduced.

[0025] According to this embodiment, by filling the escape groove 15 with grease, it is possible to prevent condensation from occurring in the escape groove 15. This is advantageous in preventing rust caused by condensation occurring in the escape groove 15. It is also possible to reduce galling and seizure on the inner peripheral surface of the hollow shaft 11 and the outer peripheral surface of the load shaft 3. This is advantageous in avoiding adhesion between the hollow shaft 11 and the load shaft 3 due to galling and seizure.

[0026] Moreover, according to this embodiment, by filling the keyway 14 with grease, it is possible to prevent rusting between the keyways 9, 14 and the key 20. Furthermore, by filling the keyway 9, 14 and the key 20 with grease, it is possible to suppress fretting wear.

[0027] 4 is different from the first embodiment in that the hollow shaft 11 has a circumferential groove 21. The second embodiment is also different in that the communication passage 16 is composed of a branch passage that communicates between the relief groove 15 and the circumferential groove 21 and the outside.

[0028] The circumferential groove 21 extends in the axial circumferential direction and is recessed outward from the inner peripheral surface of the hollow hole 13 of the hollow shaft 11. The circumferential groove 21 is preferably disposed at the end of the hollow hole 13 in the X direction, and more preferably disposed at the end portion where the hole retaining ring 6 and spacer 7 are not disposed, rather than at the tip portion where the hole retaining ring 6 and spacer 7 are disposed. It is further preferable that the circumferential groove 21 is disposed at both the tip portion and the end portion of the hollow hole 13. When the circumferential grooves 21 are disposed at both the tip portion and the end portion of the hollow hole 13, it is preferable that each of the circumferential grooves 21 is disposed as close as possible to the tip portion or the end portion, and that the distance between the circumferential grooves 21 in the X direction is close to the length of the hollow hole 13 in the X direction.

[0029] The circumferential groove 21 may communicate with the key groove 14, but may not communicate with the key groove 14 depending on the extension state of the key groove 14 in the X direction. When the circumferential groove 21 communicates with the key groove 14, it forms an ended C-shaped ring, and when it does not communicate with the key groove 14, it forms an endless O-shaped ring. The depth (depth in the axial radial direction) of the circumferential groove 21 is preferably shallower than the depth of the key groove 14, and the groove width of the circumferential groove 21 is also preferably narrower than the groove width of the key groove 14. If the depth of the circumferential groove 21 is shallower than 0.5% of the diameter of the hollow hole 13 of the hollow shaft 11, the injection resistance increases when supplying grease, and the grease cannot be supplied sufficiently. On the other hand, if the depth of the circumferential groove 21 is deeper than 3.0% of the diameter of the hollow hole 13, the time required for processing is increased, and the circumferential groove 21 acts as a notch, reducing the torque transmission capacity and strength of the hollow shaft 11. Therefore, the depth of the circumferential groove 21 is preferably within a range of 0.5% to 3.0% of the diameter of the hollow hole 13. In the present disclosure, the range of 0.5% to 3.0% includes 0.5% and 3.0%. The circumferential groove 21 extends over the entire circumference in the axial circumferential direction between the hollow shaft 11 and the load shaft 3, and corresponds to the gap of the present invention.

[0030] The communication passage 16 is composed of a branch passage that connects both the relief groove 15 and the circumferential groove 21 with the outside. The communication passage 16 has a plurality of end openings 19, each of which opens into the bottom of the relief groove 15 and the circumferential groove 21.

[0031] In the driving machine 10 of this embodiment, the communication passage 16 allows grease to be injected from the outside into the circumferential groove 21 in addition to the relief groove 15. Therefore, the grease filled in the circumferential groove 21 can prevent moisture from entering. For example, when the circumferential groove 21 is arranged only at the end of the hollow hole 13, it is advantageous to prevent moisture such as rainwater and humidity from entering from the end side of the hollow hole 13. The end of the hollow hole 13 is prevented to some extent by the spacer 7 from the end side of moisture such as rainwater and humidity. In this way, by providing the circumferential groove 21 at the end side, rust caused by moisture that has entered can be suppressed on most of the inner circumferential surface of the hollow shaft 11 and the outer circumferential surface of the load shaft 3, and rusting can be prevented. In addition, when the circumferential groove 21 is arranged at both ends of the hollow hole 13, moisture can be further prevented from entering the portion sandwiched between the multiple circumferential grooves 21. Accordingly, an increase in resistance when removing the load shaft 3 from the hollow shaft 11 can be suppressed.

[0032] Although the embodiments of the present disclosure have been described above, the driving machine of the present disclosure is not limited to the specific embodiments, and various modifications and variations are possible within the scope of the gist of the present disclosure.

[0033] The driving machine 10 may be integrated with the power source 4. As the driving machine 10 integrated with the power source 4, various known motors with reducers or geared motors can be used. Furthermore, the driving machine 10 is not limited to one that transmits power to the wheels 2 of the traveling device 1 of the crane. The driving machine 10 is particularly suitable for use in equipment that is installed outdoors and exposed to rainwater, etc.

[0034] When an end plate is used to fix the hollow shaft 11 and the load shaft 3, it is desirable that the end plate does not cover the entire area of ​​the tip surface of the hollow shaft 11. For example, a hole communicating with the tip opening 18 may be formed in the end plate at a position corresponding to the tip opening 18 of the communication passage 16.

[0035] When the circumferential groove 21 is formed, the communication passage 16 may communicate only with the circumferential groove 21. Since the circumferential groove 21 on the outer side than the relief groove 15 is filled with grease to prevent moisture from entering the relief groove 15, the communication passage 16 does not need to communicate with the relief groove 15.

[0036] The relief groove 15 may be formed in either the hollow shaft 11 or the load shaft 3, and may be formed in the load shaft 3. When the relief groove 15 is formed in the load shaft 3, the relief groove 15 extends around the entire circumference in the axial circumferential direction and is recessed inward from the outer circumferential surface of the load shaft 3. Similarly, the circumferential groove 21 may be formed in the load shaft 3. When the relief groove 15 or the circumferential groove 21 is formed in the load shaft 3, the end opening 19 of the communicating passage 16 opens into the inner circumferential surface of the hollow hole 13 at a position corresponding to the relief groove 15 or the circumferential groove 21 formed in the load shaft 3.

[0037] When the escape groove 15 and the communication passage 16 are filled with grease, the communication passage 16 may have a tip opening 18 open, or the tip opening 18 may be sealed with a plug or the like. Various known grease nipples can be used as the plug.

[0038] In the driving machine 10, the power transmission method between the hollow shaft 11 and the load shaft 3 is not limited to the key method using the key groove 14 and the key 20, but may be a friction fastening method. Examples of the friction fastening method include a wedge method such as a shrink disk, a clamping sleeve method, and a hydro method. The friction fastening method is less susceptible to fretting wear than the key method. Therefore, the friction fastening method is advantageous in avoiding adhesion caused by wear powder due to fretting wear.

[0039] The reference example of the driving machine 10 illustrated in FIG. 5 is different from the first embodiment in that grease is not filled. In the relief groove extending in the axial circumferential direction between the hollow shaft and the load shaft in the conventional technology, water caused by rainwater or humidity that has entered from the end side or condensation that has occurred in the relief groove continues to accumulate, causing rust on the inner peripheral surface of the hollow shaft and the outer peripheral surface of the load shaft. In the course of the invention, the inventors of the present invention have found that rust caused by water accumulated in the relief groove can be suppressed by ensuring the breathability of the relief groove. The reference example is based on that finding.

[0040] The escape groove 15 and the communication passage 16 of the drive unit 10 of the reference example are not filled with grease, so that rainwater or moisture may enter the escape groove 15 from the outside, or condensation may occur in the escape groove 15. The moisture present in the escape groove 15 evaporates over time and is released to the outside because the escape groove 15 is connected to the outside by the communication passage 16. In this way, even if the escape groove 15 and the communication passage 16 are not filled with grease, the escape groove 15 and the communication passage 16 communicate with the outside, improving ventilation, which is advantageous in preventing rust caused by moisture remaining in the escape groove 15 for a long period of time. To ensure ventilation, it is desirable to provide multiple communication passages 16. In addition, since the escape groove 15 and the communication passage 16 are not filled with grease, the opening that serves as an entrance and exit for the communication passage 16 to the outside may be disposed on the end surface of the hollow shaft 11 or on the outer circumferential surface of the hollow shaft 11.

[0041] It has been found that wear particles due to fretting wear are small and oxidation progresses rapidly at high temperatures. Therefore, in the reference example, wear particles due to fretting wear of the hollow shaft 11 and the load shaft 3, or the keyway 14 and the key 20, act as a medium, and the hollow shaft 11 and the load shaft 3 are likely to stick together. In contrast, the above-mentioned embodiment is more preferable because the grease filled in prevents sticking caused by wear particles due to fretting wear. However, when the power transmission method between the hollow shaft 11 and the load shaft 3 is a friction fastening method, wear particles due to fretting wear are unlikely to be generated, and there are cases where it is possible to sufficiently prevent sticking of the hollow shaft 11 and the load shaft 3 even in the reference example. [Explanation of symbols]

[0042] 3 Load axis 4 Power source 10 Drive unit 11 Hollow shaft 12 Power transmission mechanism 13 Hollow hole 14 Keyway 15 Undercut 16 Communication path 20 Keys 21 Circumferential groove

Claims

1. A driving machine having a hollow shaft into which a load shaft is inserted and a power transmission mechanism for transmitting power from a power source to the hollow shaft, in which the hollow shaft and the load shaft are fixed by fastening a hole retaining ring and a spacer or an end plate to the tip of the load shaft with a bolt, wherein the hollow shaft has a communicating passage formed inside the hollow shaft, one end of the communicating passage opens at the tip of the hollow shaft and the other end communicates with a gap extending around the entire circumference of the shaft between the hollow shaft and the load shaft, thereby connecting the gap with the outside, and the hollow shaft and the load shaft rotate by power transmitted from the power source via the power transmission mechanism with the gap filled with grease from the outside via the communicating passage.

2. The driving machine according to claim 1 , further comprising a plurality of said communication passages, each of said communication passages communicating with each other via said gap.

3. 3. The driving machine according to claim 1, wherein the gap is formed as a relief groove for reducing resistance when the load shaft is inserted into the hollow hole of the hollow shaft.

4. 3. The driving machine according to claim 1 or 2, wherein the gap is composed of an escape groove for reducing resistance when the load shaft is inserted into the hollow hole of the hollow shaft, and a circumferential groove that is disposed axially outward of the escape groove and recessed in the radial direction of the shaft.

5. 3. The driving machine according to claim 1, wherein the gap is formed by a circumferential groove disposed at an axial end of the hollow hole of the hollow shaft and recessed in a radial direction of the shaft.

6. 3. The driving machine according to claim 1, wherein the gap communicates with keyways formed in the load shaft and the hollow shaft.

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