JP5120488B2 - Linear motion screw device - Google Patents

Description

  The present invention relates to a ball screw device or a roller screw device used for driving or power transmission of a linear moving mechanism such as positioning of a moving table or conveyance of a machine device such as a machine tool, a press machine, an injection molding machine or the like. The present invention relates to a dynamic screw device.

  A ball screw device as a conventional linear motion screw device includes a screw shaft having a spiral shaft raceway groove formed on an outer peripheral surface and a pair of nut portions having a nut raceway groove opposed to the shaft raceway groove on an inner peripheral surface. A nut connected by a spacer is screwed through a plurality of balls, contact seals are attached to both ends of the nut, and both ends of the load path formed by the nut raceway grooves and the shaft raceway grooves arranged opposite to each other are attached. The return tube provided on the nut communicates to form two circulation paths, and the ball shaft is circulated through each circulation path to convert the rotational motion of the screw shaft into the linear motion of the nut. However, pressurize and supply new grease from the grease replenishment hole formed in the flange part provided at one end of the nut, and extrude the deteriorated grease from the contact seal gap provided at the other end of the nut. Degradation grease of being present in the lubricant holding space are replaced with new grease (e.g., see Patent Document 1.).

JP 11-1118017 A (paragraph 0011 of the second page-paragraph 0016 of the third page, FIG. 2)

  In general, when machining shaft raceway grooves and nut raceway grooves, in order to reduce machining allowances, the contact ellipse when subjected to a load is the land (the outer surface of the screw shaft between the shaft raceway grooves or between the nut raceway grooves). The diameter of the land part is small for screw shafts and large for nuts so that the shaft raceway grooves and nut raceway grooves are relatively shallow. The radial clearance between the land portion of the screw shaft and the land portion of the nut is about 20% of the diameter of the ball.

  However, in the above-described conventional technology, the grease existing in the lubricant holding space inside the nut is pushed out from one end to the other, so that the grease is exchanged. Grease also flows into a relatively large radial clearance, which is about 20% of the diameter of the ball, and the grease existing between the land portions is used for lubrication of the ball rolling on the load path. There is a problem that the supplied grease is wasted.

  Accordingly, an object of the present invention is to provide means for supplying new grease supplied to a linear screw device such as a ball screw device mainly to a load path on which a rolling element rolls.

  In order to solve the above problems, the present invention provides a screw shaft in which a spiral shaft raceway groove is formed on an outer peripheral surface, a nut in which a nut raceway groove facing the shaft raceway groove is formed on an inner peripheral surface, and the shaft In a linear motion screw device comprising a load path formed by a raceway groove and a nut raceway groove and a plurality of rolling elements rolling on the load path, the shaft raceway groove is formed in a land portion between the nut raceway grooves. A spiral member along the groove of the nut raceway groove that loosely fits between the land portions is provided. The spiral member is formed of an elastic material, and a hollow hole is formed in the spiral member. The helical member is expanded by pressure applied to the hole.

  As a result, the present invention suppresses the filling of the grease in the radial gap between the nut land portion and the shaft land portion, and supplies new grease supplied to the inside of the nut mainly to the load path. Thus, it is possible to effectively lubricate the balls rolling on the load path with a minimum amount of grease.

Explanatory drawing which shows the cross section of the ball screw apparatus of Example 1. The perspective view which shows the helical spacer of Example 1. FIG. Explanatory drawing which shows the attachment state of the helical spacer of Example 1. Explanatory drawing which shows the cross section of the ball screw apparatus of Example 2. Explanatory drawing which shows the supply state of the lubricant of Example 2. Explanatory drawing which shows the cross section of the ball screw apparatus of Example 3.

  Embodiments of a linear screw device according to the present invention will be described below with reference to the drawings.

FIG. 1 is an explanatory view showing a cross section of the ball screw device of the first embodiment, FIG. 2 is a perspective view showing a helical spacer of the first embodiment, and FIG. 3 is an explanatory view showing a mounting state of the helical spacer of the first embodiment.
In FIG. 1, reference numeral 1 denotes a ball screw device as a linear motion screw device.
Reference numeral 2 denotes a ball as a rolling element of the ball screw device 1, which is a sphere made of a steel material such as alloy steel.

Reference numeral 3 denotes a screw shaft of the ball screw device 1, which is a rod-shaped member made of a steel material such as alloy steel, and a gothic arc formed by arranging two arc concave surfaces in a substantially V shape on the outer peripheral surface thereof. A shaft raceway groove 4 which is a groove having a shape is formed in a spiral shape with a predetermined lead, and a spiral land portion (referred to as a shaft land portion 3 a) which is an outer peripheral surface of the screw shaft 3 is formed between the shaft raceway grooves 4. Is formed.
Reference numeral 5 denotes a nut of the ball screw device 1, which is a cylindrical member made of a steel material such as an alloy steel, and has an inner peripheral surface formed by arranging two arc concave surfaces in a substantially V shape. A nut raceway groove 6, which is a gothic arc-shaped groove, is formed with the same lead as the shaft raceway groove 4 so as to face the shaft raceway groove 4, and between the nut raceway groove 6, a spiral shape that is the inner peripheral surface of the nut 5. A land portion (referred to as a nut land portion 5a) is formed.

The radial gap S between the nut land portion 5a and the shaft land portion 3a of the present embodiment is set to about S = 0.2 Dw when the diameter of the ball 2 is Dw.
Reference numeral 7 denotes a grinding clearance groove, which is a clearance groove provided at the bottom of the shaft raceway groove 4 and the nut raceway groove 6 in order to form the shaft raceway groove 4 and the nut raceway groove 6 having a gothic arc shape by grinding. Thus, the spiral shaft raceway groove 4 and the nut raceway groove 6 are provided over the entire length.

A flange portion 8 is provided at one end of the outer peripheral portion of the nut 5, and is fixed to a moving table of a mechanical device (not shown) with a mounting bolt or the like by a mounting bolt hole 8 a provided in the flange portion 8.
Reference numeral 9 denotes a return tube as a communicating member of the ball screw device 1, which is a tube made of a steel material or a resin material and bent into a substantially U shape having an inner diameter through which the ball 2 can pass. Are fitted in holes that reach the nut raceway groove 6 provided in the flat surface 5b cut out in parallel to the axial direction and communicated with the nut raceway groove 6 by a tube fixture or the like (not shown). It is fixed to the nut 5.

As a result, both ends of the load path formed by the shaft raceway groove 4 and the nut raceway groove 6 are communicated by the communication path formed as the inner diameter of the return tube 9, thereby forming a circulation path through which the ball 2 circulates.
Two circulation paths in the present embodiment are formed in the axial direction of the screw shaft 3.
Reference numeral 10 denotes a highly hermetic seal as a seal member, which is made of a core metal made of a plate material such as alloy steel and elasticity of synthetic rubber or synthetic resin joined to the core metal by a joining means such as baking or adhesion. An annular member formed by a sealing body made of an elastic material having an annular member, and is attached to both end portions of the nut 5 in the axial direction. When attached to the part, a predetermined seal allowance is given to the shape of the cross section perpendicular to the axis of the screw shaft 3 where the inner peripheral edge is in sliding contact (the cross section in which the axis of the screw shaft 3 is a vertical line). The inner periphery of the screw shaft 3 is formed in a similar shape and slidably contacts with the outer surface of the screw shaft 3 formed by the outer peripheral surface 3a of the screw shaft 3 and / or the arc concave surface of the shaft raceway groove 4 and functions as a contact seal.

Reference numeral 13 denotes a lubricant supply hole, which is a hole that opens from the outer peripheral surface of the nut 5 in the radial direction to the bottom surface of the grinding clearance groove 7 at the bottom of the nut raceway groove 6 constituting the load path. An injection adapter 14 in which a female thread for piping or the like is formed is screwed on the outer peripheral surface side, and is used for injecting grease as a lubricant into each circulation path.
Reference numeral 16 denotes a lubricant discharge hole, which is formed by penetrating the nut 5 in the radial direction between the highly sealed seal 10 provided at the end of the nut 5 opposite to the flange portion 8 and the circulation path in the vicinity thereof. When the screw shaft 3 is rotated, the grease existing inside the nut 5 is guided in the radial direction of the nut 5 and discharged to the outside.

  Reference numeral 18 denotes a helical spacer as a helical member, which is formed by forming a thin rectangular plate made of a resin material or a metal material into a spiral shape along the groove of the nut raceway groove 6 as shown in FIG. The outer diameter is formed to be equal to the inner diameter of the nut land portion 5a of the nut 5 so that the inner diameter of the nut land portion 5a of the screw shaft 3 is loosely fitted. The width in the direction orthogonal to the groove line (referred to as the groove orthogonal direction) is formed to be narrower than the distance in the groove orthogonal direction between the balls 2 rolling the nut raceway groove 6 forming the load path.

Further, the helical spacer 18 is inserted in the radial direction in the radial direction, as shown in FIG. 3, in the screw hole 19 (see FIG. 2) provided in the central part in the winding direction at the central part in the width direction. The bolts 20 are screwed and fastened to be attached to the nut land portion 5a in a state in which the degrees of freedom in the rotational direction and the axial direction are restricted.
The helical spacer 18 is attached in such a manner that the tip of a mounting rod inserted in the radial direction from the outer peripheral surface of the nut 5 is fitted into a fitting hole provided at the same position as the screw hole 19, and the rotational direction and the axial direction. You may make it attach to the nut land part 5a in the state which restrained the freedom degree.

  A plurality of balls 2 are loaded in the circulation path, and a predetermined amount of grease is injected into the load path from the lubricant supply hole 13, and the ball 2 moves through the circulation path by rotating the screw shaft 3. The ball 2 that circulates and rolls on the load path is reciprocally supported along the axial direction of the screw shaft 3 by supporting the load applied to the nut 5 while being lubricated with grease. Thus, the rotational motion of the screw shaft 3 is converted into the linear motion of the nut 5, and the ball screw device 1 functions as a linear motion screw device.

During the operation of the ball screw device 1, grease supplied from an automatic greasing device (not shown) is intermittently automatically supplied to the load path from the lubricant supply hole 13, and the deteriorated grease causes rotation of the screw shaft 3. Along with this, the lubricant is discharged to the outside of the nut 5 through the lubricant discharge hole 16 disposed at a position away from the lubricant supply hole 13.
At this time, the nut land portion 5a of the nut 5 of this embodiment is provided with a helical spacer 18 that closes the radial gap S between the shaft land portion 3a and the nut land portion 5a and the shaft land portion 3a. It is possible to suppress the inflow of grease into the radial gap S between the two and the new grease supplied from the lubricant supply hole 13 mainly to the load path, and cannot be used for lubricating the ball 2. It is possible to effectively lubricate the balls 2 that roll on the load path with the minimum necessary amount of replenishment by eliminating unnecessary replenishment of grease.

Further, since the grease is directly supplied to the load path from the lubricant supply hole 13, the grease can directly act on the ball 2 supporting the load applied to the nut 5, and the ball 2 rolling on the load path. The lubrication efficiency can be increased.
Further, since the high-sealing seal 10 having the lip portion 11 slidably contacting the outer surface of the screw shaft 3 is attached to both ends of the nut 5, foreign matter such as dust from the outside of the nut 5 is prevented from entering. In addition, the leakage of grease from the end face of the nut 5 can be prevented.

  Thus, in the ball screw device 1 of the present embodiment, the deteriorated grease is discharged from the lubricant discharge hole 16 while suppressing the inflow of grease into the radial gap S by the helical spacer 18, so that the load path New grease can always be present, and the replenishment of the minimum amount of grease can extend the life of the ball screw device 1 and reduce wear.

  As described above, in this embodiment, the nut land portion of the nut of the ball screw device is provided with the helical spacer along the groove of the nut raceway groove that is loosely fitted to the shaft land portion. It is possible to suppress the inflow of grease into the radial clearance S between the shaft land and the shaft land, so that new grease supplied to the inside of the nut can be supplied mainly to the load path. By replenishment, the balls rolling on the load path can be effectively lubricated.

  In this embodiment, it has been described that grease as a lubricant is supplied to the lubricant supply hole, but lubricating oil or the like as a lubricant may be supplied.

FIG. 4 is an explanatory view showing a cross section of the ball screw device of the second embodiment, and FIG. 5 is an explanatory view showing a supply state of the lubricant of the second embodiment.
In addition, the same part as the said Example 1 attaches | subjects the same code | symbol, and abbreviate | omits the description.
As shown in FIG. 4, the ball screw device 1 of the present embodiment is provided with a helical tube 25 as a spiral member instead of the helical spacer 18 of the first embodiment.

The helical tube 25 is formed by forming a tube made of a resin material or a metal material into a spiral shape along the groove of the nut raceway groove 6, and the inner diameter thereof is the outer diameter of the shaft land portion 3 a of the screw shaft 3. The outer diameter of the nut 5 is formed to be equal to the inner diameter of the nut land portion 5a of the nut 5 and is arranged at the center of the nut land portion 5a in the groove orthogonal direction.
Reference numeral 26 denotes a supply port, which is a straight tube formed of the same material as the helical tube 25 and inserted in the insertion hole 27 penetrating the nut land portion 5a in the radial direction from the outer peripheral surface of the nut 5. The helical tube 25 is connected to the helical tube 25 at the center in the winding direction, and grease is supplied to the hollow hole 28 (see FIG. 5) of the helical tube 25, and the helical tube 25 is freely rotated in the rotational direction and the axial direction. It has the function to attach to the nut land part 5a in the state which restrained.

  In FIG. 5, reference numeral 29 denotes a discharge hole, which is a hole penetrating from the outer peripheral surface of the helical tube 25 to the hollow hole 28 in a direction perpendicular to the groove, and its opening is directed toward the nut raceway groove 6. 5 is provided with the function of supplying the grease shown by shading in FIG. 5 in the direction of the load path formed by the groove 6 and the shaft raceway groove 4, and equidistant along the winding direction of the helical tube 25. Are provided in plurality.

In the ball screw device 1 provided with such a helical tube 25, the grease automatically and intermittently replenished to the supply port 26 from an automatic greasing device (not shown) at the time of operation is supplied from the discharge hole 29 to the load path. The deteriorated grease is discharged from the lubricant discharge hole 16 to the outside of the nut 5 as the screw shaft 3 rotates.
At this time, since the helical tube 25 is attached to the nut land portion 5a of the nut 5 of this embodiment, the nut land portion 5a and the shaft land portion 3a are pushed out by the balls 2 rolling on the load path. The grease that has flowed into the radial gap S between them can be pushed back to the nut raceway groove 6 and the shaft raceway groove 4 with new grease ejected from the discharge hole 29, and the inflow of grease into the radial gap S can be suppressed. Thus, the new grease supplied from the supply port 26 can be mainly distributed to the load path, and the balls 2 rolling on the load path can be effectively lubricated with the replenishment of the minimum necessary grease. it can.

Further, since the grease is directly supplied to the load path from the discharge hole 29 of the helical tube 25, the grease can be directly applied to the ball 2 that supports the load applied to the nut 5, and the load path rolls. Lubrication efficiency of the ball 2 can be increased.
Further, since the high-sealing seal 10 having the lip portion 11 slidably contacting the outer surface of the screw shaft 3 is attached to both ends of the nut 5, foreign matter such as dust from the outside of the nut 5 is prevented from entering. In addition, the leakage of grease from the end face of the nut 5 can be prevented.

  As described above, in the ball screw device 1 of the present embodiment, the deteriorated grease is discharged from the lubricant discharge hole 16 while suppressing the inflow of the grease into the radial gap S by the helical tube 25. New grease can always be present, and the replenishment of the minimum amount of grease can extend the life of the ball screw device 1 and reduce wear.

  As described above, in the present embodiment, the load path is formed by providing a helical tube along the groove of the nut raceway groove that is loosely fitted to the shaft land portion in the nut land portion of the nut of the ball screw device. The grease pushed into the radial clearance S between the nut land and shaft land by the rolling ball can be pushed back to the nut raceway and shaft raceway by new grease ejected from the discharge hole. It is possible to suppress the inflow of grease into the radial gap S and supply new grease supplied to the inside of the nut mainly to the load path. Balls that roll can be effectively lubricated.

In the present embodiment, it has been described that a plurality of discharge holes are provided at equal intervals in the winding direction of the helical tube, but it is sufficient to provide them at one or more locations.
In this embodiment, the grease supply port is described as being provided at the central portion in the winding direction of the helical tube. However, the grease supply port may be provided at a plurality of locations or at a location other than the central portion. Alternatively, it may be provided at the end opposite to the lubricant discharge hole.

Furthermore, in the present embodiment, it has been described that grease as a lubricant is supplied to the supply port, but lubricating oil as a lubricant, oil mist in which lubricating oil particles are dispersed in pressurized air, and the like are supplied. You may make it do.
Further, in this embodiment, the grease is supplied to the supply port 26 of the helical tube 25. However, the lubricant supply hole 13 described in the first embodiment is provided in the nut 5, and the supply port 26 is provided. The pressurized air is supplied to the ball, and the grease pushed into the radial gap S by the balls 2 rolling on the load path is pushed back to the nut raceway groove 6 and the shaft raceway groove 4 by the air ejected from the discharge hole 29. It may be. Even if it does in this way, the effect similar to the above can be acquired.

  In this case, the helical tube 25 is formed of an elastic material such as a resin material, the openings at both ends of the discharge port 29 and the helical tube 25 are closed, air is supplied to the hollow hole 28, and the air is pressurized. The helical tube 25 is expanded and contracted so that it does not interfere with the shaft land portion 3a, and the grease pushed into the radial clearance S by the balls 2 rolling on the load path is pushed into the nut raceway groove 6 and the shaft raceway groove 4. You may make it return. In this way, the same effect as described above can be obtained by changing the spatial volume of the radial gap S.

FIG. 6 is an explanatory view showing a cross section of the ball screw device according to the third embodiment.
In addition, the same part as the said Example 1 attaches | subjects the same code | symbol, and abbreviate | omits the description.
In the present embodiment, the radial gap S between the shaft land portion 3a and the nut land portion 5a is made narrower than the radial gap S (= about 0.2 Dw) in the first and second embodiments. is there.

  In this case, if the radial clearance S is in the range of 0 <S ≦ 0.1 Dw, the nut land 5a and the shaft land 5a and the axial land can be obtained even if the radial clearance S is not blocked by the helical spacer 18 of the first embodiment. It is possible to suppress the inflow of grease into the radial gap S between the portion 3a and distribute the grease supplied to the inside of the nut 5 mainly to the load path. The balls 2 rolling on the load path can be effectively lubricated.

As described above, in this embodiment, the radial gap S between the nut land portion and the shaft land portion is in the range of 0 <S ≦ 0.1 Dw, so that the same effect as in the first embodiment is obtained. Can be obtained.
In each of the above embodiments, the ball screw device provided with two circulation paths has been described as an example. However, the same applies to a ball screw device having one circulation path.

Further, in each of the above embodiments, it has been described that the supply of grease to the inside of the nut is intermittently performed by the automatic greasing device. However, the grease gun may be supplied continuously by the automatic greasing device. The manual greasing used may be sufficient.
In each of the above embodiments, the case where the present invention is applied to a ball screw device using a tube-type circulation system in which a ball is circulated by a return tube has been described as an example, but an end cap-type or deflector-type circulation is used. The same effect can be obtained even if the present invention is applied to a ball screw device of the type.

  Further, in each of the above-described embodiments, the linear motion screw device has been described as a ball screw device using a rolling element as a ball. A roller screw device may be used.

DESCRIPTION OF SYMBOLS 1 Ball screw apparatus 2 Ball 3 Screw shaft 3a Shaft land part 4 Shaft track groove 5 Nut 5a Nut land part 5b Plane 6 Nut track groove 7 Grinding relief groove 8 Flange part 8a Mounting bolt hole 9 Return tube 10 High sealing seal 11 Lip part 13 Lubricant supply hole 14 Injection adapter 16 Lubricant discharge hole 18 Helical spacer 19 Screw hole 20 Bolt 25 Helical tube 26 Supply port 27 Insertion hole 28 Hollow hole 29 Discharge hole

Claims (2)

A screw shaft formed with a spiral shaft raceway groove on the outer peripheral surface, a nut formed with a nut raceway groove facing the shaft raceway groove on the inner peripheral surface, and a load formed by the shaft raceway groove and the nut raceway groove In a linear screw device including a road and a plurality of rolling elements that roll on the load path,
In the land portion between the nut raceway grooves, a spiral member is provided along the groove of the nut raceway groove, which is loosely fitted in the land portion between the shaft raceway grooves,
Forming the spiral member with an elastic material and forming a hollow hole in the spiral member;
A linear motion screw device, wherein the spiral member is expanded by pressure applied to the hollow hole. In claim 1,
A linear motion screw device, characterized in that seal members having lip portions slidably contacting the outer surface of the screw shaft are provided at both ends of the nut.

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