JP2003278873A - Linear motion equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a linear motion equipment wherein a high precision of movement/positioning is obtained when it is used for an operation instrument, etc., realizing the device structure with a high rigidity while making it compact. <P>SOLUTION: This linear motion equipment 1 contains a ball screw shaft 2 and also a ball nut 3 in a cylindrical housing 5 and an outer cylinder 6 is covered to movement free on the housing 5. The ball screw shaft 2 is supported by a ball bearing 10, 11 at the both ends of the housing 5 and is composed so that the outer cylinder 6 can be moved by the rotation of the ball screw shaft 2. In this way, the whole equipment is summarized as a positioning unit and compactization is realized. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a linear motion device using a ball screw or the like, and more particularly to a linear motion device suitable for use in an operating device or the like which requires high positioning accuracy.

[0002]

2. Description of the Related Art Conventionally, a ball screw shaft having a ball screw portion on its outer peripheral surface and a ball nut fitted with the ball screw shaft and screwed into the ball screw portion are provided. A ball screw mechanism is known in which a ball (steel ball) interposed in the ball screw is rolled into contact with the ball screw portion to obtain relative movement between the ball nut and the ball screw shaft. Such a ball screw mechanism is used as a linear guide mechanism. Many linear motion devices having a combined structure have been proposed.

As a conventional linear motion device, for example, a ball screw mechanism of the above construction is housed in a long case, the ball screw shaft is rotatably supported by the case, and a rail is formed along the longitudinal direction of the case. The ball nut slides in the groove, and the connecting member connected to the ball nut is projected from the slit formed on the upper part of the case over the entire length of the case to interlock with the desired operating device outside the case. There are those configured to connect.

[0004]

In such a conventional linear motion device, when the ball screw shaft is rotationally driven, the ball nut can be moved along the axial direction to operate the operating device satisfactorily. Since it has a structure in which the ball screw mechanism is simply accommodated in a case whose entire upper part is open, it cannot be said that the case is large in size, and it cannot be said that it is made compact, and it is resistant to stress, etc. The strength (rigidity) is also lowered due to the slits formed in the entire upper part of the case. Furthermore, since the ball nut is simply slid and guided in the rail groove, there is play during sliding, and it is difficult to use it for an operating device that requires high movement / positioning accuracy.

Therefore, the present invention is constructed so as to have a high rigidity while having a compact device structure, and to obtain a high movement / positioning accuracy when it is used for an operating device or the like. It is an object of the present invention to provide a linear motion device that has been solved.

[0006]

The present invention according to claim 1 (see, for example, FIGS. 1 to 3) discloses a ball screw shaft (2) having a ball screw portion (2a) formed on the outer peripheral surface thereof, and the ball screw shaft (2). A ball nut (3) fitted with the ball screw part (2a) and screwed into the ball screw part (2a); a tubular housing (5) fitted with the ball screw shaft (2) and the ball nut (3); A linear movement device (1) comprising: a cylindrical moving member (6) which is fitted in a cylindrical housing (5) and arranged so as to be movable in the axial direction, wherein the cylindrical housing (5) is , A spline groove (12) formed on the outer peripheral surface (5a) along the axial direction, and an elongated hole (13) penetratingly drilled along the axial direction at a substantially intermediate portion of the outer peripheral surface (5a).
And rotatably supporting the ball screw shaft (2) via bearings (10, 11) fitted to both ends, and the tubular moving member (6) has the elongated hole (13). Through the spline groove (12) and is guided to move along the spline groove (12) while being prevented from rotating relative to the tubular housing (5) through the spline groove (12). The linear motion device (1) is characterized in that

According to a second aspect of the present invention (see, for example, FIG. 3), a concave groove (1) formed on the inner peripheral surface of the cylindrical moving member (6) so as to be opposed to the spline groove (12).
7. The ball spline according to claim 1, further comprising 7), wherein a large number of balls (19 ...) Are interposed between the concave groove (17) and the spline groove (12) facing the concave groove (17). It is in a linear motion device (1).

The reference numerals in parentheses are for the purpose of contrasting with the drawings, but this is for convenience of understanding the invention, and is not limited to the construction of the claims. It has no effect.

[0009]

According to the invention as set forth in claim 1, the ball screw shaft and the ball nut are housed in a tubular housing, and the tubular moving member is movably fitted in the housing.
Since the ball screw shaft is supported by bearings at both ends of the housing and the moving member can be moved by the rotation of the ball screw shaft, the entire apparatus can be integrated as a positioning unit to be compact and a tubular housing. It can be used as a positioning means when it is set in an operating device or the like, and good mountability can be obtained.

Further, since the outer shape of the device itself is a substantially cylindrical housing itself, the rigidity can be increased and the hollow cylinder can be formed by fitting the bearings to both ends of the cylindrical housing where the long hole is not located. The rigidity of the cylindrical housing can be further increased. Further, since the long hole is formed by penetrating substantially the middle portion of the outer peripheral surface of the cylindrical housing, the rigidity can be improved as compared with the conventional structure in which the slit is formed over the entire outer peripheral surface. It can be further enhanced. Furthermore, by setting the cylindrical housing with the long hole facing downward, it can be used while preventing the intrusion of dust into the inside of the cylindrical housing.

Further, since the tubular moving member is guided along the spline groove while being prevented from rotating relative to the tubular housing through the spline groove, the straightness is extremely good and the circumferential direction is excellent. Moves with high positioning accuracy
The positioning accuracy can be improved. As a result, the movement / positioning accuracy is guaranteed with the spline accuracy, and it is not necessary to separately provide a guide member or the like for the movement guide of the tubular moving member, so that the mounting structure is simplified.

According to the second aspect of the present invention, by combining the ball spline and the ball screw with high accuracy, it is possible to obtain high positioning accuracy without looseness and to roll the cylindrical moving member by the ball spline. By guiding, the friction coefficient is made extremely small compared to sliding guide in which the spline is simply engaged with the spline groove, and a linear motion device with good followability with almost no friction fluctuation due to speed changes etc. is realized. can do. In addition, the centering of the support when the present linear motion device is applied to an actuating device or the like can be easily determined from the outer diameter of the cylindrical housing that is the spline shaft.

[0013]

DETAILED DESCRIPTION OF THE INVENTION A first embodiment of the present invention will be described below with reference to the drawings. 1 is a plan view showing an appearance of a linear motion device according to the present invention in an assembled state, and FIG. 2 is a cross-sectional view of the linear motion device of FIG. 1 taken along the axial direction at a portion passing through an elongated hole, FIG. 3 is a sectional view taken along line III-III in FIG. The linear motion device 1 includes a ball screw shaft 2 having a ball screw portion 2a formed on an outer peripheral surface thereof, a ball nut 3 fitted with the ball screw shaft 2 and screwed into the ball screw portion 2a, the ball screw shaft 2 and the ball nut. 3 is a cylindrical housing 5 to be fitted, and a cylindrical outer cylinder composed of a spline nut arranged to be fitted in the cylindrical housing 5 and movable in the axial direction (left and right directions in FIGS. 1 and 2). (Cylindrical moving member) 6.

The ball screw shaft 2 has a female screw hole 2b for preventing the ball bearing 10 from slipping off by screwing a screw 9 at one end (the left end in FIG. 2) with a slip-off preventing member 7 interposed. A bulging portion 2c for abutting on the ball bearing 11 fitted to the other end portion for positioning thereof, and the screw portion formed at a position away from the bulging portion 2c by a predetermined distance to the outside. It has a screw portion 2d different from 2a. In the ball screw portion 2a, a ball screw groove made of a Gothic arc in which two arcs are combined or a circular arc having a single arc shape is formed by grinding or the like. It goes without saying that the two nuts may be used and assembled without backlash.

The ball nut 3 is formed in one winding direction and has a ball groove (not shown) corresponding to the ball screw portion 2a, and a large number of balls (not shown) are interposed in the ball groove. The ball nut 3 may be of any ball circulation type such as a return plate type, a tube type and a top type.

Further, as shown in FIGS. 1 and 5, the cylindrical housing 5 has a spline groove 12 formed on the outer peripheral surface 5a along the axial direction and one end side of the housing 5 excluding both end portions. It has a long hole 13 penetratingly bored along the axial direction in a substantially intermediate portion of the outer peripheral surface 5a so as to extend to the end side. Further, the cylindrical housing 5 has a structure similar to that shown in FIGS.
As shown in FIG. 5, a small diameter portion 5b formed along the axial direction over substantially the entire inner peripheral surface excluding both end portions, and a large diameter portion 5 formed at both end portions with a diameter larger than that of the small diameter portion 5b.
c and 5d, and a female screw portion 5e formed further outside the large diameter portion 5d on the other end side.

The one cylindrical ball bearing 10 and the two cylindrical ball bearings 1 are provided at one end and the other end of the cylindrical housing 5, respectively.
Both end portions of the ball screw shaft 2 are rotatably supported via 1 and 11. Further, from the outer side of the ball bearing 11 on the other end (right side in FIG. 2) side, the press nut 15 is
The other end portion of the ball screw shaft 2 is fitted and screwed and fastened to the female screw portion 5e. This press nut 15
It is made of a ring-shaped member having an external thread on its outer peripheral surface, and a collar 18 fitted to the ball screw shaft 2 is rotatably positioned on the inner periphery of the nut 15. Therefore, in the present device 1, the outer race of the ball bearing 11 on one end side (the left side in FIG. 2) is divided into the small-diameter portion 5b and the large-diameter portion 5d by screwing and fastening the holding nut 15 to the female screw portion 5e. The bearings 11 and 11 are axially positioned by pressing the step portions of the two bearings 11, and in this state, the lock nut 16 is screwed and fastened to the threaded portion 2d of the screw shaft 2 so that the bearings 11, The inner race 11 is sandwiched between the inner race 11 and the bulging portion 2c while being pressed by the collar 18 to determine the axial position of the screw shaft 2 and center the same.

The outer cylinder 6 is connected to the ball nut 3 through the elongated hole 13 through the connecting member 14, and is prevented from rotating relative to the cylindrical housing 5 via the spline groove 12 while being connected to the spline groove 12. It is supported so as to be guided along. A motor M configured to rotate in the forward and reverse directions is connected to the other end portion (right end in FIG. 1) of the cylindrical housing 5 via a joint (not shown).

As shown in FIG. 3, the outer cylinder 6 has a concave groove (ball transfer groove) 17 formed so as to face the spline groove 12 on the inner peripheral surface thereof. A large number of balls 19 ... Are rotatably interposed between the spline groove 12 and the opposite spline groove 12, and a ball spline in which the balls 19 are circulated between the concave groove 17 and a return path (not shown) is formed. Configured (the ball moving on the return path is shown in phantom). The spline groove 12 is formed as a groove made of Gothic arc, circular arc, or the like, and is formed on the outer peripheral surface of the cylindrical housing 5 by two sets of two parallel rows at equal angular intervals, that is, as a whole. Six spline grooves 12 are provided extending along the axial direction.

The outer cylinder 6 is connected to an operating device such as a machine tool, a measuring instrument, a medical instrument, an injection molding machine, a semiconductor manufacturing apparatus, or an assembling robot.
As for the shape, as described in the present embodiment, the cylindrical shape is the best from the viewpoint of strength, but not only the cylindrical shape, but also the cross section has a substantially rectangular shape (square shape), for example. Alternatively, it may have a cylindrical shape or a substantially rectangular shape having a flange protruding in the outer diameter direction at any part thereof. In addition, the ball bearing 1 fitted to both ends of the tubular housing 5
When the housing 5 has a cylindrical shape, the outer races 0 and 11 can be mounted on the housing 5 as they are, but when the housing 5 has a shape other than the cylindrical shape, the outer race is inserted into the housing 5 through an end bracket. It is installed.

On the other hand, as shown in FIGS. 1 and 4, the connecting member 14 has a rectangular shape which is long in a plan view, has a width dimension which is sufficiently set within the width of the long hole 13, and has an axial direction. It has two female screw holes 21 and 21 formed at both ends and two fitting holes 22 and 22 formed in the central portion. The maximum movement range of the connecting member 14 is regulated by abutting both ends of the connecting member 14 in the axial direction with the ends 13a and 13b of the elongated hole 13 when the connecting member 14 is moved in the axial direction, and the outer cylinder 6 has a cylindrical housing. Ball spline on 5 (12, 17, 19)
Because of the high accuracy of positioning in the circumferential direction, a predetermined gap is held between the connecting member 14 and the elongated hole 13 on both sides in the width direction.

The connecting member 14 is housed in the elongated hole 13 and faces the ball nut 3 in the fitting hole 2 thereof.
Fixing screws 23, 23 inserted from 2, 22 are fixed to the nut 3 by being screwed into two female screw holes (not shown) of the nut 3, respectively. Also, the outer cylinder 6
Has two fitting holes 25, 25 penetratingly provided so as to be able to face the female screw holes 21, 21 of the connecting member 14, respectively. The fixing screws 26, 26 respectively inserted into the fitting holes 25, 25 are fixed to the connecting member 14 by being screwed into the two female screw holes 21, 21 of the connecting member 14.

Since the linear motion device 1 has the above-described structure, when the motor M is driven to rotate by turning on the power source from the power-off state, the ball screw shaft 2 to which the driving force is transmitted is transmitted in one direction or the other direction. The ball nut 3 moves in one direction or the other direction along the axial direction according to the rotation. Along with this, the outer cylinder 6 connected to the ball nut 3 moves on the outer peripheral surface of the cylindrical housing 5 along the axial direction. At this time, the outer cylinder 6 is the cylindrical housing 5
A large number of balls 19 provided opposite to the spline groove 12 of
By rolling the ... into the spline groove 12, smooth and accurate positioning is performed, and movement is performed until the power is turned off again.

In the linear motion device 1 as described above, the ball screw shaft 2 and the ball nut 3 are housed in the cylindrical housing 5, and the outer cylinder 6 is movably fitted in the housing 5 so that the housing 5 can Ball bearings 1 on both ends
Since the ball screw shaft 2 is supported by 0 and 11, and the outer cylinder 6 can be moved by the rotation of the ball screw shaft 2,
The entire device can be integrated as a positioning unit to realize compactness, and the cylindrical housing 5 itself can be used as a positioning means when setting it in an operating device or the like, so that the mountability is improved.

Further, since the outer shape of the device itself is substantially the cylindrical housing 5 itself, the strength against stress can be increased, and the cylindrical ball bearings 10 are provided at both ends of the cylindrical housing 5 where the elongated holes 13 are not located. By fitting 11 in, the rigidity of the hollow cylindrical housing 5 can be further improved. Further, since the elongated hole 13 is formed by penetrating substantially the middle portion of the outer peripheral surface of the cylindrical housing 5, the rigidity is higher than that of the conventional structure in which slits are formed over the entire outer peripheral surface. It is further enhanced. The cylindrical ball bearings 10 and 11 are provided at both ends of the cylindrical shape of the housing 5 where the long holes 13 are not located.
Since the ball screw shaft 2 is supported via the, the concentricity can be favorably maintained. Also, by setting the cylindrical housing 5 with the long hole 13 facing downward,
It can be used favorably while preventing dust from entering the inside of the cylindrical housing 5.

Further, the outer cylinder 6 has a ball spline (12,
Since it is guided along the spline groove 12 while being prevented from rotating relative to the cylindrical housing 5 via the (17, 19), the linearity becomes extremely good and the positioning accuracy in the circumferential direction is high, and the movement is possible. / Positioning accuracy can be improved. As a result, the movement / positioning accuracy is guaranteed with the spline accuracy, and it is not necessary to separately provide a guide member or the like for the movement guide of the outer cylinder 6, and therefore the mounting structure is simplified. Further, since the accurate positioning of the outer cylinder 6 during movement is performed by the large number of balls 19 ... And the spline groove 12, the widthwise dimension of the elongated hole 13 can be formed relatively rough, and therefore, The manufacturing process can be simplified.

Further, in the present linear motion device 1, the combination of the ball spline and the ball screw with high accuracy allows
High positioning accuracy can be achieved without play and the outer cylinder 6 is rolled and guided by the ball splines (12, 17, 19), so the slide guide in which the spline is simply engaged with the spline groove 12 is provided. The friction coefficient is extremely smaller than that of the above, and therefore, there is almost no change in friction due to speed changes and the like, and a device structure with good followability can be obtained. Further, the centering of the support when the present linear motion device 1 is applied to an actuating device or the like can be easily made by judging from the outer diameter of the cylindrical housing 5 which is the spline shaft.

The arrangement structure of the spline groove 12 is not limited to the above, and as shown in, for example, FIG. 7 (a cross section at a position not passing through the elongated hole 13 in the figure), the circumference of the cylindrical housing 5 is shown. Two spline grooves 12 may be arranged in parallel at four locations at equal angular intervals in the direction, and in this case also, the same effect as described above can be obtained.

Next, the second and third embodiments in which the configuration is partially modified will be described with reference to FIGS. 8 and 9. Since these embodiments are the same as the above-described first embodiment except for the characteristic parts, the same reference numerals are given to the common configurations and elements, and the description thereof will be omitted.

As shown in FIG. 8, the linear motion device 1A according to the second embodiment has the following structure.
A ball screw portion having opposite winding directions is formed from the center of the shaft in the left-right direction, and a ball nut having a ball groove having a corresponding winding direction is formed in each ball screw portion in the reverse winding direction. 3 and 3 are screwed together, and a large number of balls (not shown) in the ball groove.
Is intervening. Further, the pair of ball nuts 3 supported on the cylindrical housing 5 so as not to be rotatable relative to the cylindrical housing 5 and to be movable in the axial direction is used as an operating device, that is, an operating device such as an electronic component holding device or an open / close table. Be connected.

In the linear motion device 1A having such a structure,
When the power is turned on and the motor is rotationally driven in one direction to rotate the ball screw shaft 2 in one direction, the pair of ball nuts 3 and 3 having mutually opposite leads move in the direction away from each other. The actuating devices attached to the ball nuts 3, 3 move in the opening direction away from each other. On the other hand, when the motor is driven to rotate in the opposite direction, the pair of ball nuts 3 and 3 move in this direction so as to approach each other, whereby the operating devices attached to the ball nuts 3 and 3 mutually move. Move in the closing direction to approach. A predetermined operation can be performed by appropriately performing these opening / closing operations.

Further, as shown in FIG. 9, the linear motion device 1B according to the third embodiment has the same structure as that of the first embodiment described above, and additionally has a ball on the outer peripheral surface of the cylindrical housing 5. An outer cylinder (not shown) in which a large number of balls are interposed between the concave groove provided on the inner peripheral surface and the spline groove 12 (see FIG. 12) is fitted at a position opposite to the nut 3 (wavy line D). Are prepared. Then, the outer cylinder is configured to be moved along the axial direction of the cylindrical housing 5 by a driving means (not shown).

Therefore, for example, while the ball nut 3 is axially moved in one direction by rotationally driving the motor in one direction,
By driving the outer cylinder (not shown) in the wavy line D in the other direction by driving the driving means (not shown), the same opening / closing operation as in the second embodiment can be obtained.

[Brief description of drawings]

FIG. 1 is a plan view showing a linear motion device according to a first embodiment of the present invention in an assembled state.

FIG. 2 is a cross-sectional view of the linear motion device of FIG. 1 taken along the axial direction at a portion passing through a long hole.

FIG. 3 is a sectional view taken along line III-III in FIG.

FIG. 4 is a plan view showing a single connecting member.

FIG. 5 is a plan view showing a single cylindrical housing.

6 is a cross-sectional view of the tubular housing of FIG. 5 taken along the axial direction at a portion passing through an elongated hole.

FIG. 7 is a cross-sectional view showing another arrangement example of spline grooves.

FIG. 8 is a sectional view showing a linear motion device of a second embodiment according to the present invention.

FIG. 9 is a sectional view showing a linear motion device of a third embodiment according to the present invention.

[Explanation of symbols]

1 linear motion device 1A, 1B linear motion device 2 ball screw shaft 2a Ball screw part 3 ball nuts 5 Cylindrical housing (cylindrical housing) 5a outer peripheral surface 6 Cylindrical moving member (cylindrical outer cylinder) 10,11 Bearing (ball bearing) 12 ball spline (spline groove) 13 long hole 17 ball spline (concave groove) 19 ball spline (ball)

Claims (2)

[Claims] 1. A ball screw shaft having a ball screw portion formed on an outer peripheral surface thereof, a ball nut fitted with the ball screw shaft and screwed into the ball screw portion, and a cylindrical housing fitted with the ball screw shaft and the ball nut. And a tubular moving member fitted to the tubular housing and arranged so as to be movable in the axial direction, wherein the tubular housing has an outer peripheral surface in the axial direction. The ball screw shaft includes a spline groove formed along the outer peripheral surface, and a long hole penetrating along the axial direction at a substantially intermediate portion of the outer peripheral surface, and the ball screw shaft is rotatable through bearings fitted to both end portions. The tubular moving member is coupled to the ball nut through the elongated hole, and is prevented from rotating relative to the tubular housing through the spline groove, and along the spline groove. It is moved guided comprising, linear motion device, characterized in that. 2. The inner peripheral surface of the tubular moving member is provided with a concave groove formed so as to face the spline groove, and a large number of balls are provided between the concave groove and the facing spline groove. The linear motion device according to claim 1, wherein the linear motion device is formed by being interposed therebetween.