JPS63308264A - Pre-load adjusting device for rectilinear motion guide mechanism - Google Patents

Abstract

PURPOSE:To avoid horizontal and axial looseness by providing a piezoelectric actuator between a bolt tightening a movable member and the movable member on a slider movably held on a track table through balls. CONSTITUTION:A rectilinear motion guide mechanism includes a slider 21 movably held on a track table 18 through balls 20 and a work table 16 tightened by a bolt 22 through a piezoelectric actuator 23 at a designed space L above the slider. When electric field is applied to the piezoelectric actuator 23 at need, the actuator is elongated in the longitudinal direction of the bolt and the recess portion of the slider 21 sags inward to be deformed, so that pre-load is given to the balls 20 between the slider 21 and the track table 18. Thus, the axial looseness of the track table and the lateral looseness intersecting perpendicularly thereto with respect to the work table can be avoided to increase rigidity. Furthermore, when pre-load is cancelled at the time of no-load feeding, the occurrence of disadvantages such as lowering of life and generation of heat can be restrained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a preload adjustment device for a linear motion guide mechanism, which allows the amount of preload to be changed without permission depending on usage conditions.

(Prior Art) This type of linear motion guide mechanism is constructed by fitting and holding a slider movably in a track base through a hole, and is applied to a sliding part of a work table of a machine tool, etc.

By the way, if there is play in the axial direction of the track or in the lateral direction orthogonal to the track in the linear motion guide mechanism provided in the 48 moving parts such as the work table of a machine tool, highly accurate machining cannot be expected. Therefore, in order to eliminate the axial and/or lateral backlash of the linear motion guide mechanism and realize highly accurate machining, a preload is applied to the linear motion guide mechanism. A common method for applying this preload is to insert a hole of a larger size between the track and the slider.

(Problems to be Solved by the Invention) However, according to the conventional method of applying preload (constant pressure preload) described above, changes in load during cutting, etc., and table movement during and after cutting Since the amount of preload can be changed arbitrarily depending on the change in time, on the other hand, due to insufficient amount of preload, cutting reaction force and vibration from the tool side act on the work table during cutting, resulting in chatter on the cutting surface. etc., resulting in a problem that high-precision machining cannot be performed. On the other hand, if an excessive amount of preload is applied, sliding resistance will abnormally increase when the table moves after cutting, which will not only make it impossible to move the work table quickly or easily, but also cause problems such as heat generation and shortened service life. was occurring.

Therefore, the present invention was made in view of the above circumstances, and its purpose is to enable preload to be adjusted arbitrarily depending on the usage conditions, thereby improving machining accuracy on the one hand, and on the other hand, making it easy to use. To provide a linear motion guide mechanism capable of performing rapid forwarding.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides a linear motion guide mechanism in which a slider is fitted to a track via a steel ball so as to be capable of linear movement. A movable member is connected with a bolt to a slider having a directional groove formed therein so that a slight gap is formed at the center of the longitudinal groove of the slider, and the head of the bolt and the movable member to be tightened are connected. A piezoelectric actuator was interposed between the seat and the seat.

(Function) In the present invention having the above configuration, if a unidirectional electric field is applied to the piezoelectric actuator interposed between the fastened seat surface of the movable member and the bolt head, the piezoelectric actuator will expand due to piezoelectric reverse effect. Therefore, the necessary amount of preload can be applied to the ball interposed between the track base and the slider. In this case, since there is a proportional relationship between the voltage applied to the electrodes of the piezoelectric actuator and the amount of displacement of the piezoelectric element, the amount of preload can be adjusted steplessly by controlling the amount of applied voltage as necessary. .

(Example) An example of the present invention will be described below based on the accompanying drawings.

In FIG. 3 showing a state in which the linear motion guide mechanism according to the present invention is applied to a one-way table of a machine tool, reference numeral 1 denotes a screw shaft installed horizontally between side walls 2a and 2b of the housing body 2; The screw shaft 1 is rotatably supported by the side walls 2a, 2b by ball bearings 3.3. and,
A gear 4 is connected to one end of the screw shaft 1, and the gear 4 meshes with a gear 6 connected to the end of the output shaft of a motor 5.

By the way, as shown in FIG. 2, the screw shaft 1 has a continuous spiral groove 7 formed therein, and the screw shaft 1 has a plurality of balls 8 that engage with the spiral groove 7. Two nuts 9 and 10 are movably screwed together at a predetermined interval. A single or split annular piezoelectric element 11 is interposed between both double nuts 9 and 10. Since this piezoelectric element has a characteristic that it expands and contracts when a voltage is applied, the present invention is configured as a piezoelectric actuator (displacement element) that utilizes the characteristic of the piezoelectric element. Note that the piezoelectric actuator may be formed by a plurality of rod-shaped piezoelectric elements arranged parallel to the screw shaft 1, but an annular actuator has a more uniform extension width than a rod-shaped actuator, so it is necessary to adjust the preload. There is little error in quantity. A ball screw mechanism A is formed by the screw shaft 1, double nuts 9 and 10, and piezoelectric actuator 11 described above.

Further, as shown in FIG. 3, both nuts 9 and 10 are held by a bracket 15 vertically installed on a work table 16, and this work table 16 is moved parallel to each other in a direction perpendicular to the plane of the paper via a linear motion guide mechanism C. The work table 16 is supported so as to be movable in the axial direction along a pair of front and rear track stands 18.18, and a work W is set on the work table 16. In FIG. 3, reference numeral 19 denotes a cutting tool such as a milling cutter that is rotationally driven by a drive source (not shown) to machine the upper surface of the workpiece W.

As shown in FIG. 1 (only one track is shown), the slide guide mechanism C has linear grooves 18a formed on both slopes of a single track 18 installed in a direction perpendicular to the plane of the paper.
, 18a, and are arranged and circulated endlessly through a plurality of balls 20..., which are arranged and circulated in an endless manner, the slider 21, which has a groove-shaped cross section, is held movably in the direction perpendicular to the plane of the drawing. It consists of Further, a longitudinal groove 21a is formed in the center of the upper surface of the slider 21, and the work table 16 is provided with a predetermined gap ΔL on the upper surface of the slider 21 at the center position of the longitudinal groove 21a. and is fastened by a bolt 22. That is, a plurality of screw holes 21b are bored in the center of the longitudinal groove 21a of the slider at predetermined intervals in the longitudinal direction, and
A stepped loose fitting hole 1 corresponding to the slotted hole 21b of the slider is provided on the side edge of the work table 16 which is brought into contact with the upper surface of the slider with a predetermined gap Δ within the groove width range T of a.
The bolts 22 are screwed into the loose fitting holes 16a and screw holes 21c which are coaxially arranged. In FIG. 1, reference numeral 16b is a large diameter portion that accommodates the Holt head 22a, and 16c is a seat surface to be tightened, which is connected to the slider 2 via a bolt.
It functions as a fulcrum when pulling the center part of 1 upward. The seat surface to be tightened is not limited to the case where it is formed on a stepped portion, and the upper surface of the work table may also be used. And, between the head 22a of the bolt 22 and the seat surface 16c of the work table 16 to be tightened, there is a piezoelectric actuator 23, which is single or divided into two parts and has an annular or rod shape, similar to the piezoelectric actuator 11. (Actually, a total of four locations are installed at the four corners of the work table 16) are interposed.

By the way, in the embodiment shown in FIG. 3, the work table 16 is moved to the track base 18.
The fourth
In the other embodiment shown in the figures, a separate ball mechanism B is provided which allows the work table 16 to be moved not only in the x-x direction but also in the Y-Y direction perpendicular thereto.

To further explain the embodiment shown in FIG. 4, the same components as those in the embodiment shown in FIG. 3 will be described with the same reference numerals. Directly below the first ball screw mechanism A (exactly the same as the ball screw mechanism A in FIG. 3) that moves the ball in the x-X direction along the track 18°18, A second ball screw mechanism B is provided so as to be orthogonal to the work table 16, and is configured to move the work table 16 along the tracks 18', 18' in the YY direction orthogonal to the xX direction. There is. Therefore, like the first ball screw mechanism A, this second ball screw mechanism B is also composed of a screw shaft, a double nut, and a piezoelectric actuator.
By moving the housing body 2 holding the first ball screw mechanism A in the Y-Y direction along the tracks 18', 18', the table is transferred in the Y-Y direction. In short, the screw shaft 1' shown in FIG. 4, a double nut (not shown), and a piezoelectric actuator constitute the ball screw mechanism B, and this ball screw mechanism B moves the work table along the tracks 18', 18' along the Y-axis. Transfer it in the Y direction.

The end of the screw shaft 1' is connected to a motor 5' via a gear (not shown).

Next, the functions of the ball screw mechanisms A and B and the linear motion guide mechanism C will be explained.

For example, when the motor 5 is driven, the rotational force of the motor 5 is transmitted to the screw shaft 1 through the gear 6.4, and the screw shaft 1 is rotated at a fixed position. As the screw shaft l rotates, the nuts h9 and 10 that are screwed thereto move linearly along the screw shaft 1, and this movement causes the work table 16
is transported along the track 18.18 in the xx direction.

The work table 16 can also be moved in the Y-Y direction by a similar operation.

Thus, for example, the nut 9 constituting the ball screw mechanism A.
If an electric field is applied as necessary to the piezoelectric actuator 11 interposed between the nuts 9 and 10, the piezoelectric actuator 11 will expand in the direction of the screw axis due to the piezoelectric reverse effect, and the piezoelectric actuator 11 will expand in the direction of the screw axis due to the piezoelectric reverse effect.
10 in the direction of separating them from each other, and arbitrarily change the preload of the hole screw mechanism A. If the preload of the ball screw mechanism A is increased, the movement (backlash) of the nuts 9 and 10 along the screw shaft 1 is eliminated, thereby eliminating the axial play of the work table 16 along the X-X direction and increasing the rigidity. You can improve your performance. Similarly, by increasing the preload of the Hall screw mechanism B as necessary, not only the axial backlash along the Y-Y direction of the work table 16 can be eliminated, but also the rigidity can be increased.

By the way, if an electric field is also applied to the piezoelectric actuator 23 provided in the linear motion guide mechanism C according to the present invention as necessary, the piezoelectric actuator 23 will expand in the longitudinal direction of the bolt, thereby deforming the slider 21, By adjusting the gap between the slider 21 and the ball 20, the preload of the linear motion guide mechanism C can be adjusted as desired. That is, when the piezoelectric actuator 23 is extended in the longitudinal direction of the bolt, an upward tensile force acts on the center portion of the slider 21 via the bolt 22, and this upward tensile force causes the center portion of the slider 21 to close the gap ΔL. As a result, the skirt portion 21c of the slider is bent upward so as to pinch the track base 1.
8 side, the ball 2 between the slider 21 and the track 18
0 is pre-compressed and the track base 18 regarding the work table is
Not only can play in the axial direction and the lateral direction perpendicular to this be eliminated, but also the rigidity can be increased.

Next, preload adjustment in the following cases will be explained.

(A) When applied to a one-way table (see Figure 3) For example, while moving the work table 16 in the direction of arrow a (X-X direction) shown in Figure 3, the work W is moved with the tool 19 in a fixed position. When performing cutting, if the preload of the ball screw mechanism A and the linear motion guide mechanism C is increased by operating the piezoelectric actuator, the work table 16 is fixed in the X-X direction, so that the axial play can be eliminated. At the same time, rigidity can be ensured, thereby eliminating the chatter phenomenon on the cutting surface of the workpiece W, allowing the workpiece W to be machined with high precision.

Note that if the load during cutting changes, the amount of preload can be adjusted accordingly. Then, if the amount of preload is eliminated or reduced by reducing the amount of voltage applied to the piezoelectric actuator after machining is completed,
The work table 16 can be easily fast-forwarded without any sliding resistance, and the ball screw mechanism A and the linear motion guide mechanism C
There are no problems such as heat generation or shortened lifespan.

(B) When applied to an X-Y table (see Fig. 4) For example, while moving the table 16 in the arrow direction (X-X direction) shown in Fig. 4, the workpiece W is
Taking the case of cutting as an example, the work table 16 is fixed or released in the X-X direction by applying or releasing preload to the ball screw mechanism A and the linear motion guide mechanism C, as in the case of FIG. It is done.

By the way, when cutting the work W while moving the work table 16 in the X-X direction, cutting reaction forces and tools are applied to the work table 16 not only in the X-X direction but also in the Y-Y direction. Since side vibrations and the like are acting, unless backlash in the Y-Y direction is eliminated and rigidity is not achieved, the work table 16 will move in the Y-Y direction and machining accuracy will not be achieved.

Therefore, when applied to an X-Y table as shown in Figure 4, it is necessary to double-fix it not only in the X-X direction but also in the Y-Y direction during cutting. Therefore, by adjusting the preload of the ball screw mechanism B and the linear motion guide mechanism C, the looseness in the Y-Y direction can be eliminated and rigidity can be ensured.

In addition, when changing the direction of the work table 16 from the X-X direction to the Y-Y direction and performing cutting, or when moving the table after machining, the ball screw mechanism B and the linear motion guide mechanism C may be adjusted as necessary. Just adjust the amount of preload.

(Effects of the Invention) As is clear from the above description, according to the present invention, a piezoelectric actuator is provided between the bolt that fastens the movable member to the slider movably held on the track via the ball and the movable member. The preload of the linear motion guide mechanism can be arbitrarily changed according to the usage conditions by expanding and contracting the piezoelectric actuator due to the piezoelectric reverse effect. Since the necessary rigidity can be maintained, it is possible to improve the machining accuracy, and also to solve problems such as shortened life and heat generation.

[Brief explanation of the drawing]

FIG. 1 is a detailed view of the linear motion guide mechanism according to the present invention, and FIG.
The figure is a cross-sectional view of the ball screw mechanism, the third figure is a cutaway side view of a Yanagi one-way worktable for a machine tool that uses the same linear motion guide mechanism, and the fourth figure is an X-Y worktable of a linear motion guide machine tool. FIG.
...Slider 22...Bolt 23...Piezoelectric actuator

Claims (1)

[Claims] In a linear motion guide mechanism in which a slider is linearly movably fitted to a track via a steel ball, a longitudinal groove is formed at the center of the top surface of the slider. A linear motion guide characterized in that the movable members are connected by bolts so that a slight gap is formed between them, and a piezoelectric actuator is interposed between the head of the bolt and the seat surface of the movable member to be tightened. Mechanism preload adjustment device.