TW201537068A - Ball screw - Google Patents

Abstract

The present invention provides a ball screw used with pre-compression applied to a ball. The ball screw has a structure that achieves a balance of cooling efficiency and ease of assembly/disassembly. Thus, the ball screw comprises a screw rod and a plurality of nuts capable of moving with respect to the screw rod in an axial direction. Each nut has a flow channel and the flow channel is a cooling mechanism serving as an independent passage for allowing a cooling medium to pass through. These flow channels are arranged symmetrically with respect to a reference between the nuts so as to allow the cooling medium to circulate independently in each of the nuts.

Description

Ball screw

The present invention relates to a ball screw, and more particularly to a screw having a function of cooling a nut.

A conventionally known ball screw has a threaded shaft and a nut that is screwed to the threaded shaft through a plurality of rotating bodies (for example, balls), and the threaded shaft and the nut are rotatable relative to each other. In the ball screw, frictional heat is generated between the screw shaft and the nut by point contact or surface contact during rotation, and thus a cooling portion for cooling the friction portion is provided.

Examples of the installation type of the cooling portion of the conventional ball screw include an axial cooling method and a nut cooling method. In the above-described axial cooling method, the screw shaft is used as a cooling target, and the cooling portion is provided in the screw shaft. An example of the axial cooling method is a structure in which the screw shaft is hollow and a cooling medium flows through the screw shaft. Further, in the above-described nut cooling method, the nut is set as a cooling target, and the cooling unit is provided in the nut shape.

Here, the above-mentioned axial cooling method is adopted in a large scale. In the case of a long ball screw device, since the cost required to dig a hollow hole in the above-mentioned screw shaft becomes a problem, a nut cooling method is often employed.

As a ball screw using such a nut cooling method, the technique disclosed in Patent Document 1 is exemplified. Patent Document 1 specifically discloses a technique in which a cooling medium is circulated through a flow path provided in a nut along an axial direction to cool the nut.

[Previous Technical Literature] [Patent Document]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2010-133556

In recent years, the mainstream of large and long ball screws has been a double-nut preloaded ball screw. In this type of ball screw, it is important to efficiently cool a plurality of nuts and suppress the cooling medium from decomposing. Leakage during assembly, maintenance, and maintenance.

However, even if the ball screw disclosed in Patent Document 1 is applied to a ball screw that is pre-compressed with a double nut, the balance of the ball screw can be achieved by efficiently cooling the plurality of nuts and suppressing leakage of the cooling medium. There is still room for improvement.

The present invention has been made to solve the above problems, and an object of the invention is to provide a ball screw which is excellent in cooling efficiency and can suppress leakage of a cooling medium during disassembly, assembly, and even maintenance, and can achieve these balances.

In order to achieve the above object, a ball screw according to an embodiment of the present invention has a threaded shaft formed with a spiral groove on an outer circumferential surface, and two nuts having a spiral groove on the inner circumferential surface opposite to the spiral groove. And a plurality of balls disposed between the spiral groove and the spiral groove of the threaded shaft are screwed into the threaded shaft; and a preloading applying member is preloaded on the ball, and the two nuts are respectively The cooling unit is independently provided, and the cooling unit is disposed on the nut so as to be symmetrical with respect to the two nuts.

That is, the ball screw of the embodiment of the present invention has a threaded shaft formed with a spiral groove on the outer circumferential surface, and two nuts having a spiral groove on the inner circumferential surface facing the spiral groove, and a plurality of balls disposed between the spiral groove and the spiral groove of the threaded shaft are screwed into the threaded shaft; and a preloading applying member is applied to the ball, and the two nuts are independently A cooling unit (cooling mechanism) is provided, and the cooling unit is disposed on the nut so as to be symmetrical with respect to the two nuts. Moreover, the above two nuts are assembled or connected or adjacently assembled.

Here, regarding the ball screw, the cooling unit is The flow path through which the cooling medium passes is preferably at least one of an axial flow path along the axial direction and a circumferential flow path perpendicular to the axial direction. That is, the cooling portion has a flow path through which the cooling medium passes as independent paths. These flow paths include at least one of an axial flow path and a circumferential flow path. The axial direction flow path is a flow path provided in the axial direction between the inner circumference of the nut and the outer circumference of the nut. Further, the circumferential flow path is a flow path provided between the inner circumference of the nut and the outer circumference of the nut so as to be orthogonal to the axis of the nut. In this manner, the cooling unit is configured such that the cooling medium is circulated independently of the nut.

Further, the ball screw is preferably provided with an inflow hole that is connected to the flow path and allows a cooling medium to flow, and a discharge hole that is connected to the flow path and discharges the cooling medium. That is, it is preferable that each of the nuts has a shape in which at least one or more of the inflow holes as the inflow portion of the cooling medium and the discharge holes as the outflow portion are provided.

Further, in the above-described ball screw, the preload applying member is preferably a gasket that is disposed coaxially with the two nuts between the two nuts.

Further, as the preload applying member, a configuration may be employed in which a positioning preload by positional adjustment between the nuts and a constant pressure preload by an elastic body such as a spring, and a fluid pressure or piezoelectric element are used. The actuator is used to set a variable control preload of a predetermined preload load, and the like. More specifically, a configuration may be employed in which the above-described pre-compressed structure is disposed between the nuts, and the plurality of nuts are pressed against each other or pulled to each other.

According to the present invention, it is possible to provide a ball screw which is excellent in cooling efficiency and which can suppress leakage of a cooling medium during disassembly, assembly, and even maintenance, and can achieve these balances.

1‧‧‧Ball screw

100‧‧‧ first nut

150‧‧‧The Ministry of Cooling

200‧‧‧second nut

250‧‧‧The Ministry of Cooling

300‧‧‧Threaded shaft

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a side view showing the structure of an embodiment of a ball screw of the present invention.

Fig. 2 is a partial cross-sectional view showing the structure of an embodiment of the ball screw of the present invention.

Fig. 3 is a side view showing the structure of an embodiment of the ball screw of the present invention.

Hereinafter, an embodiment of the ball screw will be described with reference to the drawings.

Fig. 1 is a side view showing the configuration of an embodiment of a ball screw. 2 is a partial cross-sectional view showing the configuration of the embodiment of the ball screw. 3 is a side view showing the structure of the embodiment of the ball screw, and the flow path is enlarged and highlighted.

As shown in FIG. 1, the ball screw 1 of the present embodiment has two nuts (a first nut 100, a second nut 200), and a threaded shaft 300, and is disposed between the two nuts. A preloading preloading member is applied to the aforementioned balls.

<nut>

The first nut 100 has a main body portion 100A formed in a cylindrical shape having an inner diameter larger than the outer diameter of the screw shaft 300, and a cover 110 and tubes 120 and 121. The cover 110 is attached to the one end portion of the main body portion 100A through a sealing material 111 by a screw or the like (not shown). Further, the tubes 120 and 121 are provided in the rotating body circulation member of the sealing material 115 among the outer peripheral surfaces of the main body portion 100A, and are fixed by the pressing plates 122 connected to the first nut 100 by the screws 123 to 125. The first nut 100, that is, a nut of a flangeless type.

The second nut 200 has a main body portion 200A formed in a cylindrical shape having an inner diameter larger than the outer diameter of the screw shaft 300, a flange portion 201 provided at one end portion thereof, and a cover 210 and a tube 220, 221. The cover 210 is attached to the end portion of the main body portion 200A through a sealing material 211 by a screw or the like (not shown). Further, the tubes 220 and 221 are members of the rotating body that are provided in the planar portion 215 among the outer peripheral surfaces of the main body portion 200A, and are fixed by the pressing plates 222 that are coupled to the second nut 200 by screws 223 to 225.

Here, as shown in FIG. 2, a spiral groove 101 is formed in the inner circumferential surface 100a of the first nut 100, and the spiral groove 101 is formed into a spiral groove 301 which is formed in a spiral shape on the outer circumferential surface 300a of the screw shaft 300. Relative. Further, a spiral groove 201 is formed on the inner circumferential surface 200a of the second nut 200, and the spiral groove 201 faces the spiral groove 301 of the screw shaft 300. Then, the plurality of rotating bodies B disposed between the spiral groove 101 and the spiral groove 201 are coaxial with each other in the axial direction of the threaded shaft 300 and the threaded shaft 300. The first first nut 100 and the second nut 200 are screwed together. In this way, the rotating body B can be rotated by the turning path formed by the spiral groove 301 and the spiral grooves 101 and 201, and the threaded shaft 300 and the first nut 100 and the second nut 200 can be relatively moved in the axial direction. .

<Preloading application member>

As shown in FIGS. 1 and 2 , the other end of the first nut 100 and the other end of the second nut 200 are coaxial with the first nut 100 and the second nut 200 . A spacer 128 is provided through the sealing material 129, 130. Then, the first nut 100 and the second nut 200 are coupled by the connecting member 127 through the spacer 128 and the sealing materials 129 and 130. Although the connecting member 127 is one in FIGS. 1 and 2, a plurality of positions of the first nut 100 and the second nut 200 may be connected by a plurality of connecting members 127 as necessary.

In this manner, the first nut 100 and the second nut 200 are coupled by the connecting member 127 through the spacer 128, and the spacer 128 and the connecting member 127 function as a preload applying member, that is, the application is fixed. The type of position preloading. Then, the ball screw 1 of the present embodiment offsets the first nut 100 and the second nut by applying a two-point contact preloading force to the first nut 100 and the second nut 200 in the pulling direction. The pre-compression torque caused by the cooling of 200 is increased, and the first nut 100 and the second nut 200 can be efficiently cooled.

The preload applying member is not limited to the positional preload caused by the positional adjustment between the nuts 100 and 200, and the following may be selected. Structure: constant pressure preload by an elastic body such as a spring, and variable control preload such as a fluid pressure or a piezoelectric element to set a predetermined preload load.

<cooling section>

Cooling portions 150, 250 for cooling the respective nuts 100, 200 are separately provided in the first nut 100 and the second nut 200, respectively. Then, the cooling units 150 and 250 are between the two nuts 100 and 200 (for example, the intermediate point in the axial direction of the spacer 128 and the plane A orthogonal to the axial direction (refer to FIG. 2). As a standard, the nuts 100 and 200 are respectively disposed in a symmetrical manner. By providing the cooling units 150 and 250 as described above, the weight balance of the ball screw device can be maintained without impeding smooth driving. Here, the type of the cooling portions 150 and 250 is arranged symmetrically with respect to the relationship between the two nuts 100 and 200, as long as the first nut 100 and the second nut 200 can be independently cooled. Yes, there are no special restrictions, and it can be appropriately selected according to the purpose.

The cooling units 150 and 250 are, for example, as shown in FIGS. 1 and 2, and are a plurality of flow paths 152 to 154 and 252 to 256 through which the first nut 100 and the second nut 200 are perforated to allow the cooling medium to pass. It is preferable that at least one of the flow paths has an axial flow path along the axial direction and a circumferential flow path that is orthogonal to the axial direction. The "axial flow path" includes, for example, axial flow paths 152 and 154 along the axial direction in the first nut 100 and axial flow paths 253 and 255 along the axial direction in the second nut 200. . Flow paths 152, 154, 253, 255 in these axial directions The axial direction flow path 152 and the axial direction flow path 253 are flow paths symmetrically provided between the two nuts 100 and 200. Further, the axial direction flow path 154 and the axial direction flow path 255 are flow paths symmetrically provided between the two nuts 100 and 200.

Further, the "circumferential flow path" is exemplified by a circumferential flow path 153 which is orthogonal to the axial direction in the first nut 100 and which is provided along the circumferential direction, and is orthogonal to the axial direction in the second nut 200. And circumferential flow paths 252, 254, 256 are provided along the circumferential direction. Among the circumferential flow paths 153, 252, 254, and 256, the circumferential flow path 153 and the axial direction flow path 254 are flow paths symmetrically provided between the two nuts 100 and 200. As described above, the cooling units 150 and 250 are configured such that the cooling medium can be independently circulated in the nuts 100 and 200.

Further, in the ball screw 1 of the present embodiment, the first nut 100 is preferably provided with an inflow hole 151 that is connected to the flow paths 152 to 154, in which the cooling medium flows, and a discharge hole 155 that discharges the cooling medium. Further, in the ball screw 1 of the present embodiment, the second nut 200 is preferably provided with an inflow hole 251 that is connected to the flow paths 252 to 256, in which the cooling medium flows, and a discharge hole 257 that discharges the cooling medium. In other words, it is preferable that each of the nuts 100 and 200 has at least one of the inflow holes 151 and 251 of the inflow portion of the cooling medium and the discharge holes 155 and 257 of the discharge portion.

As a result, as shown in FIGS. 1 to 3, the cooling portion 150 of the first nut 100 is configured such that the inflow portion 151 provided in the axial direction at the end portion of the cover 110 and the axial direction flow path 152 are formed. And the circumferential flow path 153, the axial direction flow path 154, and the discharge portion 155 provided at the end of the cover 110 in the axial direction. That is, a flow path of a separate system is formed for the first nut 100. Further, the flow paths may be two or more systems as long as the nuts 100 and 200 are independent.

As shown in FIG. 1 to FIG. 3, the cooling unit 250 of the second nut 200 is configured such that an inflow portion 251 is provided on the outer circumference of the flange portion 201 in a direction orthogonal to the axis, and The circumferential direction flow path 252, the axial direction flow path 253, the circumferential direction flow path 254, the axial direction flow path 255, and the circumferential direction flow path 256, and the outer circumference of the flange portion 201 are disposed in the direction orthogonal to the axis Discharge portion 257. That is, a flow path of a separate system is formed for the second nut 200. Further, the flow paths may be two or more systems as long as the nuts 100 and 200 are independent.

Here, the inflow portions 151 and 251 and the discharge portions 155 and 257 are provided with tapered threads for piping for connecting pipes, and these pipes can be connected to supply and discharge the cooling medium.

<cooling media>

As the cooling medium, various gases and liquids as a fluid can be used. As the gas, in addition to air or compressed air, nitrogen gas, an inert gas (argon gas or the like), a hydrocarbon (butane, isobutane, etc.), helium, ammonia, carbon dioxide, or the like, or even a mixture of these may be used. As the liquid, in addition to water, a coolant in which a rust inhibitor is added to water, a coolant in which various additives are added to water, or various oils as a cooling medium oil can be used. Specifically, mineral oil, animal and vegetable oils, and synthetic oils can be used. These can be used as appropriate The environment and the like can be appropriately selected. Further, the cooling medium is preferably subjected to temperature management and flow management. In particular, it is preferred to use the cooling medium in a turbulent state.

Further, in the present embodiment, temperature management is performed independently for each nut, and for example, preload control may be performed.

Further, the position and size of the inflow portion and the discharge portion, the cross-sectional shape of each flow path, and the sectional area may be appropriately adjusted depending on the use conditions.

According to the ball screw of the present embodiment, since the preload can be increased, it can be smoothly applied to a ball screw called a large one (the outer diameter of the threaded shaft 300 is approximately 80 mm or more).

According to the ball screw of the present embodiment, since the cooling medium can be circulated independently on the respective nuts, the cooling efficiency is good. With this good cooling efficiency, the nut is first cooled, and the cooling effect is transmitted from the spiral groove in the inner circumference of the nut to the ball of the rotating body, and further transmitted to the spiral groove of the threaded shaft to cool the threaded shaft. It is considered that deterioration of the pre-pressure due to heat generation or deterioration of lubrication can be suppressed. This cooling effect can exert a further effect when the preload is high to some extent and the spiral groove and the rotor and the spiral groove are in contact with the rotor. Therefore, the ball screw of the present invention is suitable for a larger type of ball screw.

Further, according to the ball screw of the present embodiment, even if it is difficult to use a long (about 4 m or more) ball screw called a shaft cooling method, it can be used without cooling in the axial center, but it can be used in combination if necessary. Axis cooling.

Moreover, according to the ball screw of the present embodiment, it is cooled by cooling. However, the flow path of the medium is independently provided to each of the nuts, so that, for example, when it is necessary to exchange maintenance of several of the nuts in a plurality of nuts, as long as the piping for the respective cooling medium flow paths is blocked, The leakage of the cooling medium during maintenance can be effectively suppressed.

Therefore, the ball screw of the present embodiment can be suitably used for a ball screw that is particularly required for machining accuracy, that is, a large-sized working machine that is used for maintenance in a linear operation portion.

Further, since the ball screw of the present embodiment is excellent in cooling efficiency, the change in the preload load and the change in the length of the threaded shaft are small, and since excessive heat generation can be suppressed, the deterioration of the lubricant is also small, so that the ball screw is used. The positioning accuracy of the linear motion portion due to heat generation is less deteriorated, and the stable operation with less torque fluctuation can be maintained for a long period of time. Since the effect can be exhibited even in a long threaded shaft, it is particularly suitable for use. A large-scale precision machining work machine uses a ball screw in a linear motion section. Also, it can be used together with the shaft cooling.

The ball screw of this embodiment is suitable for a ball screw that is used in a linear motion portion for a large-scale precision machining work machine.

Although the embodiments of the present invention have been described above, the present invention is not limited thereto, and various modifications and improvements can be made.

1‧‧‧Ball screw

100‧‧‧ first nut

100A‧‧‧ Body Department

110‧‧‧ Cover

111‧‧‧ Sealing material

115‧‧‧ Sealing material

120, 121‧‧‧ tube

122‧‧‧ Press plate

123~125‧‧‧ screws

127‧‧‧Connected components

128‧‧‧shims

129, 130‧‧‧ Sealing materials

150‧‧‧The Ministry of Cooling

151‧‧‧Inflow hole

152~154‧‧‧Flow

155‧‧‧Exhaust hole

200‧‧‧second nut

200A‧‧‧ Body Department

201‧‧‧Flange

210‧‧‧ Cover

211‧‧‧ Sealing material

215‧‧‧Flat Department

220, 221‧‧ ‧ tube

222‧‧‧ Press plate

223~225‧‧‧ screws

250‧‧‧The Ministry of Cooling

251‧‧‧Inflow hole

252~256‧‧‧flow path

257‧‧‧Exhaust hole

300‧‧‧Threaded shaft

Claims (5)

A ball screw having a threaded shaft formed with a spiral groove on an outer circumferential surface thereof, and two nuts having a spiral groove on an inner circumferential surface facing the spiral groove, and being disposed through the spiral a plurality of balls between the groove and the spiral groove of the threaded shaft are screwed with the threaded shaft; and a preloading member that applies a preload to the ball; and the two nuts are independently provided with a cooling portion, The cooling unit is disposed on the nut so as to be symmetrical with respect to the two nuts. The ball screw according to claim 1, wherein the cooling unit is a flow path through which a cooling medium passes, and the flow path has an axial flow path along the axial direction and a circumferential direction perpendicular to the axial direction At least one of the flow paths. The ball screw according to claim 2, wherein each of the nuts is provided with an inflow hole that is connected to the flow path and that supplies a cooling medium, and a discharge hole that is connected to the flow path and that discharges the cooling medium. The ball screw according to claim 1 or 2, wherein the preload applying member is a gasket disposed coaxially with the two nuts between the two nuts. The ball screw according to claim 3, wherein the preload applying member is a spacer disposed coaxially between the two nuts and the two nuts.