JPH0673791B2 - Friction feed mechanism - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a friction feed mechanism using a friction roller, and can be used in a table or a head feed mechanism of a measuring instrument or machine tool.

[Conventional technology]

Conventionally, in a coordinate measuring machine, a machine tool, etc., a feed mechanism is provided in each movable direction to adjust the relative position of a table on which a work is placed, a probe, or a head supporting a tool.

Since such a feed mechanism is required to have high accuracy, a method of converting the rotational movement of the drive shaft into a reciprocating movement in the axial direction by using a spiral engagement structure such as a ball screw is often used. However, it is necessary to finish the screw shape formed on the drive shaft with high accuracy, which increases the manufacturing cost and causes the feed pitch to be fixed. Therefore, in order to meet the contradictory requirements such as high-speed feed for rough adjustment and precision feed for approaching a workpiece, etc., a speed change mechanism or clutch mechanism should be installed between the drive shaft and motor, or Structural complications such as the addition of fine movement units were unavoidable.

On the other hand, the friction roller, which is in contact with the drive shaft at a predetermined lead angle, rolls on the peripheral surface of the drive shaft and is fed by the component force in the drive shaft direction generated on the friction roller as the drive shaft rotates. A friction feeding mechanism has been developed for performing. In such a friction feed mechanism, it is not necessary to form a spiral screw on the drive shaft, the manufacturing cost can be reduced, and the lead angle of the friction roller (the rotation axis of the friction roller and the rotation axis of the drive shaft is formed). The feed pitch can be arbitrarily set or changed according to the angle.

[Problems to be Solved by the Invention]

By the way, in the above-mentioned friction feed mechanism, the lead angle and feed pitch of the friction roller can be adjusted steplessly even during operation, and it is possible to switch between high-speed feed and precision feed with a simple operation. Is.

However, when the friction roller is made movable, an angle adjusting means controlled with high precision is required in order to accurately set the friction roller to a desired lead angle, and the adjusted friction roller is adjusted to the lead angle. There was a problem that the structure became complicated again because a means for accurately fixing to the corner was required.

An object of the present invention is to provide a friction feed mechanism capable of accurately and easily switching a plurality of feed pitches and simplifying the structure.

[Means for Solving the Problems]

According to the present invention, the feeding operation of the friction feed mechanism depends on the friction rolling between the friction roller and the peripheral surface of the drive shaft, and even if the friction roller is separated from the drive shaft, the feeding operation by the friction roller becomes invalid. It was made paying attention to becoming.
That is, one of the two relatively movable members is provided with a rotating drive shaft, and the other member is provided with a plurality of friction rollers that are rollable around the peripheral surface of the drive shaft and that are inclined and arranged at different lead angles. The friction rollers are supported by independent supports, and each support is provided with a contacting / disconnecting means capable of press-contacting each friction roller with the peripheral surface of the drive shaft by displacement of the piezoelectric element. Is configured.

As the piezoelectric element of the present invention, a Pb (Zr-Ti) O ₃ -based ceramics, or a piezoelectric material such as crystal or crystal such as LiNbO ₃ sandwiched between a pair of electrodes can be used. Also,
These piezoelectric elements may be laminated to expand the mechanical movement amount, or a lever type movement amount expanding mechanism using a rotating arm or the like may be used.

Further, the separating / connecting means has a structure in which a piezoelectric element is provided in a part of a support body that can move back and forth toward the drive shaft, and the support body advances toward the drive shaft due to displacement caused by energization, or a swingable support. A structure in which a piezoelectric element is provided at one end of a body and a friction roller supported at the other end is rotated toward a drive shaft can be used.

On the other hand, when arranging the plurality of friction rollers, the support and the piezoelectric element, these may be arranged along the drive shaft, or may be arranged in the circumferential direction so as to surround a predetermined position of the drive shaft.

Further, when it is desired to avoid bending of the drive shaft or the like, a pair of friction rollers having the same lead angle may be arranged so as to face each other with the drive shaft interposed therebetween, and pressure may be applied simultaneously from both sides with substantially the same strength.
Alternatively, a guide bearing for preventing bending may be arranged opposite to the opposite side of the drive shaft.

[Action]

In the present invention thus constituted, the lead angle of each friction roller is accurately set so as to give a desired feed pitch, and any friction roller is selected by the contact / separation means to rotate the circumference of the drive shaft. The feed pitch is easily switched by pressing it against the surface, and the feed pitch of each friction roller is accurately maintained by not changing the lead angle during the switching. Further, by adopting the piezoelectric element for pressing the friction roller, the ease of operation and the simplification of the structure are realized, thereby achieving the above object.

〔Example〕

 An embodiment of the present invention will be described below with reference to the drawings.

1 and 2, the table feeding device of this embodiment includes a bed 10 and a table 20, which are two members that move relative to each other, and the table 20 is guided by a guide mechanism 2 formed on the upper surface of the bed 10. At the same time, it can be reciprocated by being driven by the friction feed mechanism 1 according to the present invention.

The bed 10 is provided with a drive shaft 11 along the guide mechanism 2. The drive shaft 11 has a smooth peripheral surface, is supported by bearings 12 and 13 in the vicinity of both ends thereof so as to be rotatable and immovable in the axial direction, and is connected to a motor 15 via a coupling 14. Is configured to be rotationally driven by.

The table 20 is formed in a substantially gate-shaped cross section, and on the back side of the upper surface thereof, two support bodies 21 and 22 are provided along the longitudinal direction of the drive shaft 11, and each of them is attached to the drive shaft 11 so as to be movable back and forth. ing. Friction rollers 23 and 24 are rotatably attached to the tips of the supports 21 and 22, respectively.
22 is the rotation axis of each friction roller 23, 24 is the drive shaft 11
Lead angle A1 and lead angle with respect to the rotation axis of
It is inclined to form A2 (A2 <A1).

Laminated piezoelectric elements 25 and 26 having electrodes on the front and back are respectively interposed between the supports 21 and 22 and the table 20, and the piezoelectric elements 25 and 26 are operating devices connected to the electrodes. 2
The support 21 and 22 and the friction rollers 23 and 24 can be moved toward and away from the drive shaft 11 by being displaced according to the voltage applied from 7. Here, the respective piezoelectric elements 25, 26 normally hold the friction rollers 23, 24 by holding them at a distance from the peripheral surface of the drive shaft 11, but at the time of maximum displacement due to energization, the friction rollers 23, 24 Is set to be brought into pressure contact with the peripheral surface of the drive shaft 11 with a sufficient contact pressure.

The operating device 27 is capable of selecting only one of the piezoelectric elements 25, 26 when applying a voltage to each of the piezoelectric elements 25, 26, and the plurality of friction rollers 23, 24 are pressed against the drive shaft 11 at the same time. These piezoelectric elements 25,26
Also, the operating device 27 constitutes separating / contacting means 28, 29 for each of the friction rollers 23, 24.

In this embodiment having such a configuration, high-speed feed and precision feed are continuously executed by the following procedure.

First, in order to move the table 20 to the vicinity of the target position, the separating / connecting means 28 is selected and high speed feeding is performed. That is,
A voltage is applied to the piezoelectric element 25 by the operating device 27, the displacement of the piezoelectric element 25 lowers the support 21, and the friction roller 23 is pressed against the peripheral surface of the drive shaft 11. Here, when the drive shaft 11 is rotated by the motor 15, the friction roller 23 rolls on the peripheral surface following the rotation of the drive shaft 11, and the feed pitch P1 = πdtan (A1) ( d is the diameter of the drive shaft 11) and is the drive shaft
It moves in the axial direction of 11 and feeds the table 20 to the bed 10 at a feed pitch P1 at high speed.

On the other hand, when the table 20 reaches near the target position, the motor 15 is stopped to stop the rotation of the drive shaft 11, and the separating / connecting means 28
Instead, the separating / connecting means 29 is selected to perform the precision feeding operation. That is, the voltage application from the operating device 27 is switched from the piezoelectric element 25 to the piezoelectric element 26 to separate the friction roller 23 from the drive shaft 11, and instead the support 22 is lowered to press the friction roller 24 against the drive shaft 11. Let Here, when the rotation of the drive shaft 11 by the motor 15 is restarted, the friction roller 24 moves in the axial direction of the drive shaft 11 at the feed pitch P2 = πdtan (A2) (P2 <P1) according to the lead angle A2, Table against bed 10
Precisely feed 20 at feed pitch P2.

According to the present embodiment configured as described above, the following effects can be obtained.

That is, by providing dedicated friction rollers 23 and 24 for high-speed feed and precision feed, respectively, and changing the respective lead angles A1 and A2, the table 20 differs from the bed 10 even if the rotation speed of the drive shaft 11 is the same. It can be fed at feed pitches P1 and P2.

Therefore, there is no need for a speed change mechanism or the like for changing the rotation speed of the drive shaft 11 in order to switch the feed speed, and the structure can be greatly simplified as compared with a conventional feed mechanism that uses a speed change mechanism or the like.

Further, the selection of the lead angles A1 and A2 of the friction rollers 23 and 24 is arbitrary, and the feed pitch P1 for high speed and the feed pitch P2 for precision can be freely set,
Not only the pitch can be adjusted, but the friction rollers 23 and 24 can be set in the opposite directions to each other, and the rotation direction of the motor 15 can be fixed and used for the forward / reverse switching of the feed direction of the table 20.

Further, each friction roller 23, 24 has a lead angle A1, A2
Can be set independently, and the angle of other friction rollers is not affected by the change, so that adjustment work at the time of setting and changing can be facilitated.

On the other hand, since selection and cancellation of each feed speed in the friction feed mechanism 1 are performed by separating and contacting the friction rollers 23 and 24 with respect to the drive shaft 11, switching of each feed operation can be made extremely smooth.

Further, since the separating / contacting operation of each friction roller 23, 24 is performed by the corresponding piezoelectric element 25, 26, the switching of the feed speed is extremely simple by selecting the piezoelectric element 25, 26 energized from the operating device 27. In addition, the operation itself is simple switching, so automation is easy.

Further, since the distance between the friction rollers 23 and 24 and the drive shaft 11 for releasing the friction rollers 23 and 24 may be small, the displacement of the supports 21 and 22 need not be so large. A sufficient switching operation is possible by the displacement of the laminated piezoelectric elements 25 and 26 in the thickness direction.

In addition, by utilizing the rigidity of the piezoelectric elements 25 and 26 themselves, each piezoelectric element 2
By interposing 5, 26 between the supports 21 and 22 and the table 20 to have a function as a structural material, the friction roller 2
The structure for supporting 3,24 can be further simplified.

The present invention is not limited to the above embodiment,
It also includes the following modifications.

That is, the number of friction rollers provided in the friction feed mechanism 1 is two.
The number of lead angles is not limited to one, and may be increased / decreased in accordance with the required number of feed speeds. The lead angle set for each is not limited to high speed feed or precision feed, and may be adjusted appropriately.

Further, the arrangement of the friction roller is the same as that of the drive shaft 11 as in the above embodiment.
The arrangement is not limited to the above, and may be appropriately changed in implementation.

For example, in the embodiment shown in FIG. 3, friction rollers 23 and 24 are arranged on both sides of the drive shaft 11 so as to face each other, and piezoelectric elements 25 and
The drive shaft 11 is alternately pressure-contacted by 26. In this embodiment, the same parts as those in the embodiment of FIG. 1 are designated by the same reference numerals and the description thereof will be omitted for simplification.

According to such an arrangement, the height of the upper surface of the table 20 can be reduced and the dimension of the drive shaft 11 in the axial direction can be shortened.
The table 20 can be made compact.

The arrangement of the friction rollers is not limited to two positions facing each other, but may be an arbitrary angular position, or three or more friction rollers may be arranged in the circumferential direction around a predetermined position of the drive shaft, and a large number of them may be arranged. Even in the case of using the friction roller, the dimension of the drive shaft in the axial direction can be shortened.

Further, the arrangement in the axial direction and the arrangement in the circumferential direction may be combined, and for example, by adopting the arrangement in which two friction rollers are arranged along the drive shaft in three rows in the circumferential direction,
In addition to being compact, the degree of freedom in design can be increased.

Further, in the embodiment of FIG. 3, a plurality of sets of friction rollers arranged opposite to each other with the drive shaft interposed therebetween are arranged, and lead angles of the friction rollers of each pair opposed to each other are made to coincide with each other, and both sides of the drive shaft are arranged. You may press-contact simultaneously.

In such a case, the bending of the drive shaft due to the pressure contact of the friction roller can be canceled by each other, and it is effective in the case where a pressure contact force of the friction roller against the drive shaft is required such as a feeding operation under a high load.

On the other hand, the structure of the support may be appropriately selected for implementation, but it is preferable to provide appropriate strength so that it can operate smoothly in accordance with the displacement of the piezoelectric element and that buckling or unnecessary deformation does not occur. It is desirable that at least the lead angle of the friction roller be maintained accurately.

Further, the support body is not limited to a structure that is attached via a piezoelectric element and is movable back and forth, and may be a swing arm shape or a lever type structure that is rotatably supported at one point.

For example, in the embodiment shown in FIG. 4, a rod-shaped support
Around the middle of 31,32 is rotatably supported on the inner side surface of the table 20, and friction rollers 33, 34, which are opposed to each other with the drive shaft 11 interposed therebetween, are supported at equal lower end angles on the lower ends of the tables.
The upper ends of the supports 31, 32 are pivotally connected to both ends of a piezoelectric element 35 which is formed in a substantially columnar shape and is displaceable in the longitudinal direction, and a pair of separating / connecting means 30 is formed by these. Although not shown, a plurality of sets of the separating / connecting means 30 are arranged along the drive shaft 11, and the lead angles of the friction rollers 33, 34 of each set are set to different angles. Further, in other parts of this embodiment, the same parts as those in the embodiment of FIG. 1 are designated by the same reference numerals, and the description thereof will be omitted for simplification.

According to such an arrangement, the displacement of the piezoelectric element 35 causes each of the supports 31 and 32 to rotate, and the pair of friction rollers 33 and 34 causes the drive shaft to rotate.
It is possible to press the drive shaft 11 by sandwiching 11 and perform the feeding operation based on each lead angle. Further, since the pressure contact force generated by the piezoelectric element 35 is evenly distributed to both friction rollers 33, 34, it is possible to reliably cancel the bending of the drive shaft 11 and the like due to the pressure contact force of each other.

By the way, the drive shaft 11 of the friction feed mechanism 1 is not limited to one driven at a constant rotation speed, but may be one driven to rotate by a motor 15 having a variable rotation speed. The speed change can be obtained.

As an example, a case where a four-phase hybrid type step motor is used as the motor 15 in the above embodiment will be described.

This motor 15 has a maximum speed of 20 when driven by a constant current chopper.
High-speed rotation of about revolutions / second is achieved, and precision rotation with a minimum resolution of 10,000 pulses / revolution speed can be realized during constant voltage mini-step driving. If the lead angles A1 and A2 of the friction rollers 23 and 24 are adjusted so that the feed pitch P1 per rotation of the drive shaft 11 is 5 mm and the feed pitch P2 is 1 mm, the motor 15 Friction rollers 23,24 during high speed rotation of
By selecting, the maximum speed is 100 mm / sec or 20 mm /
It is possible to switch to any of sec and the minimum resolution can be switched to either 0.5 μm / pulse or 0.1 μm / pulse when the motor 15 is rotating precisely. Therefore, by selecting the friction rollers 23 and 24 in addition to switching the motor 15 itself, two types of precision positioning operations, high-speed and medium-speed coarse adjustment operations, medium-precision feeding, and high-precision feeding, can be performed, depending on the situation. Various settings are possible.

Further, in the above-described embodiment, the drive shaft 11 is stopped every time the feed speed is switched, but the feed operation of the table 20 is canceled when neither of the friction rollers 23, 24 is pressed against the drive shaft 11. The drive shaft 11 does not have to be stopped at the time of switching. In this case, since the motor 15 is continuously rotated, it is only necessary to accurately maintain a constant rotation, the rotation speed can be easily controlled, and a rotation stabilization wait time such as when restarting the rotation is unnecessary, so that the feeding operation can be switched. It can be done speedily. Further, since the friction rollers 23, 24 are in frictional contact with the drive shaft 11, the drive shafts that are rotating at a constant speed.
When it comes into contact with 11, it is possible to appropriately slip to alleviate the shocking motion, and it is possible to suppress the shock given to the table 20 and the unreasonable force applied to each structural portion to a low level.

Further, the two members that move relative to each other to which the frictional feed mechanism 1 is applied are not limited to the bed 10 and the table 20, but may be, for example, a column and a head of a machine tool, and the present invention can be applied to various feeding operation parts. It is a thing.

〔The invention's effect〕

As described above, according to the friction feed mechanism of the present invention, it is possible to accurately and easily switch a plurality of feed pitches and to simplify the structure.

[Brief description of drawings]

FIG. 1 is a side view showing an embodiment of the present invention, FIG. 2 is a top view of the embodiment, and FIGS. 3 and 4 are sectional views showing different embodiments of the present invention. DESCRIPTION OF SYMBOLS 1 ... Friction feed mechanism, 2 ... Guide mechanism, 10, 20 ... Bed and table which are two members that move relative to each other, 11 ... Drive shaft, 21, 22, 31, 32 ... Support, 23, 24 , 33,34 …… Friction roller, 25,26,35 …… Piezoelectric element, 27 …… Operating device, 28,29,
30 ... connection / disconnection means

Claims (1)

[Claims] 1. A rotating drive shaft is provided on one of two relatively movable members, and the other member has a plurality of friction members which are rollable on the peripheral surface of the drive shaft and are inclined with different lead angles. A roller is provided, and each of these friction rollers is supported by an independent support body, and each support body is provided with a contact / separation means capable of press-contacting each friction roller with the peripheral surface of the drive shaft by displacement of the piezoelectric element. Characteristic friction feed mechanism.