JPH01316146A - Friction feed mechanism - Google Patents

Abstract

PURPOSE:To change a feed pitch accurately and simply and to keep it by holding a friction roller at a holding body capable of turning in a direction where a load angle is changed with respect to a driving angle and providing an angle adjusting means, at the holding body, for turning said holding body according to the displacement of a piezoeletric element. CONSTITUTION:The lead angle of a friction roller is changed by an angle adjusting means 26 to make a feed motion. Namely, the voltage of negative polarity is added to piezoelectric elements 22, 23 from an operating device 25 to contract the element 22, meantime, to extend the element 23 to turn a holding body 21 for inclining the lead angle of the roller 24 at a state of A1 and also maintaining added voltage from the device 25 constant so as to keep the lead angle A1. Accordingly, the roller 24 is followed by the rotation of a driving shaft 11 to be turned its circumference to be moved in an axial direction by a feed pitch according to the lead angle and a table 20 is fed to a bed 10 at a high speed. Meantime, when the table is reached near an aimed position, the lead angle of the roller 24 is to be small A2 by the angle adjusting means 26 to perform a minute feed motion.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a friction feed mechanism using friction rollers, and can be used for tables or hand feed mechanisms of measuring instruments, machine tools, etc.

[Prior art] Conventionally, coordinate measuring instruments, machine tools, etc. have been provided with a feed mechanism for each movable direction, and the relative positions of the table on which the work is placed, the probe, or the hend that supports the tool are adjusted. There is.

Since such a feeding mechanism requires high precision, a method is often used in which a helical engagement structure such as a ball screw is used to convert the rotational motion of the drive shaft into reciprocating motion in the axial direction. However, the threaded shape formed on the drive shaft must be finished with high precision, which increases manufacturing costs, and there is a problem that the feed pinch is fixed. Therefore, in order to meet the conflicting demands of high-speed feed during rough adjustment and precision feed when approaching a workpiece, a speed change mechanism or clutch mechanism is installed between the drive shaft and the motor, or a high-speed feed mechanism is installed. Structural complications such as the addition of a fine movement unit were unavoidable.

In contrast, a friction roller that is in contact with the drive shaft at a predetermined lead angle is transferred to the circular surface of the drive shaft, and the feed operation is performed by the force generated in the drive shaft direction on the friction roller as the drive shaft rotates. A friction feed mechanism has been developed to do this. In such a friction feed mechanism, there is no need to form a spiral thread on the drive shaft, which reduces manufacturing costs. [Problem to be solved by the invention] By the way, in the above-mentioned I'9 rubbing mechanism,
Even during operation, the lead angle and feed pitch of the friction roller can be adjusted steplessly, and it is possible to switch between high-speed feed and precision feed with a simple operation.

However, if the FIX friction roller is movable, a highly precisely controlled angle adjustment means is required to accurately set the friction roller to the desired lead angle, and in addition, it is necessary to adjust the angle of the friction roller after adjustment. A means for accurately fixing the lead angle is required, which again complicates the structure.

An object of the present invention is to provide a friction feed mechanism that can accurately change the feed pitch to a node rli, maintain the changed feed pitch accurately, and have a simplified structure.

(Means for Solving the Problems) According to the present invention, the lead angle adjustment range of the friction roller required for a variable feed pitch friction feed mechanism is relatively small, and the displacement of the piezoelectric element is sufficient. This was done by focusing on the fact that the shaft itself has rigidity.In other words, one of the two relatively movable members is provided with a rotating drive shaft, and the other member is provided with a rotating drive shaft that rotates on the circumferential surface of the drive shaft. A friction roller is provided, and this friction roller is supported on a support that can rotate in a direction in which the lead angle with respect to the drive shaft changes, and the support has an angle adjustment means that rotates the support by displacement of a piezoelectric element. is provided, thereby configuring a friction feed mechanism.

As the piezoelectric element of the present invention, Pb(Zr-Ti)O, l
A piezoelectric material such as ceramics or crystals such as quartz or 1.1NbOi sandwiched between a pair of electric rods can be used. Further, the mechanical motion amount may be expanded by stacking these piezoelectric elements, or a lever-type motion amount enlarging mechanism using a rotating arm or the like may be used. Furthermore, it is also possible to use a combination of several piezoelectric elements and shift each phase to increase the amount of motion.

Moreover, as a support, F'2! ! 10 - Extend a member that supports the roller in the direction of the drive shaft, support both ends of the member through a pair of piezoelectric elements, and rotate the member by applying voltages in opposite directions to each piezoelectric element, which is the angle adjustment means. You can use the following items. Alternatively, the support can be a member supported rotatably around a rotation axis that intersects the central axis of the drive shaft, and the support can be provided with a rotation arm of a predetermined length from the rotation axis. The angle adjusting means may be formed by connecting piezoelectric elements.

Furthermore, if it is desired to avoid deflection of the drive shaft, etc., a pair of friction rollers that are linked so that they always have the same lead angle are arranged opposite to each other across the drive shaft, and are pressed against each other with approximately the same strength from both sides. Alternatively, a guide bearing for preventing deflection may be disposed on the opposite side of the drive shaft.

[Operation] In the present invention configured as described above, each time a predetermined voltage is applied to the piezoelectric element of the angle adjustment means, the piezoelectric element is displaced, and the support body is rotated to adjust the lead angle of the friction roller with respect to the drive shaft. to change to the desired feed pitch. Here, the lead angle of the friction roller is maintained accurately as long as there is no change in the applied voltage due to the rigidity of the piezoelectric element, and the pitch is maintained accurately so as not to change due to the load associated with the feeding operation.

Furthermore, by using electrically operated piezoelectric elements to change and maintain the lead angle of the friction roller,
Ease of operation and simplification of structure are achieved, thereby achieving the above objectives.

〔Example〕

Hereinafter, one embodiment of the present invention will be described based on the drawings.

1 and 2, the table feeding device of this embodiment includes a head 10 and a table 20, which are two members that move relative to each other, and this table 20 is guided by a guide mechanism 2 formed on the upper surface of the head 10. Along with being
It is capable of reciprocating movement driven by a friction feed mechanism 1 based on the present invention.

A drive shaft 11 is provided in the head 10 along the guide mechanism 2. This drive shaft 11 has a smooth circular surface, and bearings 12.1 are provided near both ends of the drive shaft 11.
3, which is supported rotatably and immovably in the axial direction,
It is configured to be rotationally driven by a motor 15 connected via a coupling 14.

The tail 20 has a substantially gate-shaped cross section, and is provided with a plate-shaped support 21 extending along the longitudinal direction of the drive shaft 11 on the back side of its upper surface. It is supported on the table 20 via piezoelectric elements 22,23. Further, a friction roller 24 is rotatably supported on the lower surface of the support body 21 at approximately the center thereof.
4 is pressed against the circumferential surface of the drive shaft 11 with a predetermined pressure, and can be moved as the drive shaft 11 rotates. Note that the friction roller 24 is normally held parallel to the drive shaft 11 and has a lead angle of 0.

Here, each piezoelectric element 22, 23 is constructed by providing electrodes on the front and back sides of a plate-shaped piezoelectric material, and responds to a voltage of opposite polarity applied from the operating device 25 connected to each electrode. For example, when the piezoelectric element 22 is contracted, the piezoelectric element 23 is expanded, thereby rotating the support body 21 and changing the lead angle of the friction roller 24 from A1 to A2 in the figure.
The angle adjusting means 26 is configured here.

In this embodiment configured as described above, the feeding operation is performed in the following procedure.

First, the drive shaft 11 is rotated by the motor 15 at a constant rotation speed, and the friction roller 24 pressed against the circumferential surface of the drive shaft 11 is caused to roll. Normally, the lead angle of the friction roller 24 is maintained at 0, the +1X friction feed mechanism 1 does not perform a feeding operation, and the table 20 remains stopped at its current position.

Here, the angle adjusting means 26 allows Il! The feed operation is started by changing the angle of the J-rubbing roller 24. That is, by applying a voltage of opposite polarity to the piezoelectric elements 22 and 23 from the operating device 25, the piezoelectric elements 22 and 23 are contracted, while the piezoelectric elements 22 and 23 are contracted.
3 and rotate the support body 21 to release the friction roller 24.
The lead angle is tilted to the state shown by AI in the figure. In this state, if the voltage applied from the operating device 25 is maintained constant, each piezoelectric element 22, 23 maintains the lead angle At of the friction roller 24 due to its rigidity regardless of external force. Therefore, the friction roller 24 follows the rotation of the drive shaft 11 and moves around the circumference, and the feed pinch P1 corresponding to the lead angle A1 = πdtan (^1) (d is the diameter of the drive shaft 11)
The table 20 is moved in the axial direction of the drive shaft 11, and the table 20 is sent to the head 10 at a high speed at a feed pitch PI.

Meanwhile, the table 20 has reached near the target position.

If so, the lead angle of the friction roller 24 is reduced by the angle adjustment means 26 to perform a precision feeding operation. That is, the voltage value applied from the operating device 25 is reduced, and each piezoelectric element 22.
By reducing the amount of displacement of the roller 23, the rotation of the support body 21 is returned and the lead angle of the friction roller 24 is maintained at the state indicated by A2 in the figure. Along with this angle adjustment, the friction roller 24 changes the feed pitch P2=πd tan according to the lead angle 2.
(^2) Move in the axial direction of the drive shaft 11 with (P2<Pl) and feed the table 2o with respect to the head 10.

Send accurately with Chi P2.

Note that when the table 20 is sent in the opposite direction, the polarity of the voltage applied from the operating device 25 is reversed, and each piezoelectric element 2
By reversing the contraction and expansion of 2.23, the support body 21 can be rotated in the opposite direction to maintain the lead angle of the friction roller 24 in the state shown in the figure.

According to this embodiment configured in this way, the following effects can be obtained.

That is, by rotating the support body 21 by the angle adjustment means 26 and changing the lead angle of the friction roller 24, the table 20 is sent with respect to the head IO at an arbitrary feed pitch while the rotation of the drive shaft 11 is kept constant. be able to.

Therefore, when switching the feed speed and direction, there is no need to change the rotation speed and direction of the drive shaft 11, and it is only necessary to accurately maintain a constant rotation. In addition to eliminating the need for stabilization waiting time, the structure can be significantly simplified compared to conventional feed mechanisms that use a speed change mechanism or the like.

On the other hand, the angle adjustment means 26 causes the piezoelectric elements 22, 23 to contract,
Since the support body 21 is rotated using extension, switching of the feeding operation of the friction feeding mechanism 1 can be easily performed by electrical operation from the operating device 25.

Moreover, each piezoelectric element 22, 23 can continuously change the rotation angle of the support body 21 by adjusting the voltage value applied from the operating device 25, and adjust the lead angle of the friction roller 24 to an arbitrary angle. It is also possible to make subtle adjustments.

Furthermore, each piezoelectric element 22,23 has a stiffness of 1
Since the support body 21 is supported in a constant state as long as the applied voltage from the abuse device 25 is maintained constant, the set lead angle of the friction roller 24 can be maintained accurately, and the lead angle can be adjusted separately. There is no need to provide a mechanism for fixing the support body 21 after adjustment, and the structure can be simplified and the operation when adjusting the angle can be simplified.

Another embodiment of the invention is shown in FIGS. 3 and 4. Note that the basic parts of this embodiment are substantially the same as those of the embodiment shown in FIG.

Here, a plate-shaped support 31 is provided inside the side surface of the table 20.
is rotatably supported via a rotation shaft 32. A friction roller 24 is rotatably supported on this support body 31.
It is pressed against the circumferential surface of the drive shaft 11. Note that the support body 31
The rotating wheel line is arranged to intersect both the rotational axis of the drive shaft 11 and the rotational axis of the friction roller 24. On the other hand, the support body 31 extends upward, and the tip of a prismatic piezoelectric element 33 is rotatably connected to the end thereof.

The base end of this piezoelectric element 33 is rotatably connected to the inside of the upper surface of the table 20, and the lead angle of the friction roller 24 can be adjusted by rotating the support body 31 in accordance with the applied voltage from the operating device 25. , This constitutes the angle adjustment means 30.

According to this embodiment configured in this way, the friction roller 2
4 lead angles are AI, A2. A3, etc. can be changed, and substantially the same effect as the embodiment shown in FIG. 1 can be obtained.

Further, the lead angle of the friction roller 24 can be changed by expanding and contracting the negative piezoelectric elements 33, and the angle can be adjusted more easily by omitting the balance adjustment of the voltage applied from the servo device 25. I can do it.

Furthermore, since the support body 31 is rotated by the rotation shaft 32, the position of the friction roller 24 can be regulated and pressed against the drive shaft 11 accurately and reliably, and based on the lead angle given to the friction roller 24. This enables more accurate feeding operation.

Note that the present invention is not limited to the above embodiments,
It also includes the following modifications.

That is, the number of friction rollers provided in the friction feed mechanism 1 is 1.
The number of friction rollers 24 is not limited to one, but a pair of friction rollers 24 may be arranged opposite to each other on both sides of the drive shaft 11 and pressed together at the same time (or three or more friction rollers 24 may be arranged around the drive shaft 11). good.

In such a case, the drive shaft 1 due to pressure contact of the friction roller 24
1 can cancel each other out, which is effective when a pressing force of the friction roller 24 against the drive shaft 11 is required, such as in a feeding operation under a high load.

Note that the pair of fall rollers 24 must be set so that their respective lead angles match each other so that accurate feeding operation can be performed.
g! It is possible to adopt means such as linking the support of the rubbing roller 24 to the machine/mounting device, or applying the same voltage value to each angle adjustment mechanism 26 from the operating device 25.

Furthermore, the structure of the support body is not limited to the above embodiments, and may be selected as appropriate in practice, but it should be appropriately selected so that it can operate smoothly in accordance with the displacement of the piezoelectric element and does not cause buckling or unnecessary deformation. It is preferable that the friction roller has sufficient strength, and is desirably configured such that at least the lead angle of the friction roller given by the angle adjustment means can be accurately maintained.

Furthermore, the drive shaft 11 of the friction feed mechanism 1 is not limited to one that is always rotated at a constant rotation speed, but is also driven by a variable rotation speed motor 15.
It may also be rotationally driven by, and a wider range of feed rate changes can be obtained with a simple structure.

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

This motor 15 performs high-speed rotation at a maximum speed of about 20 revolutions/second when driven by a constant current chopper, and can realize precise rotation with a minimum resolution of about 10,000 pulses/rotation when driven by a constant voltage mini-step. Here, the lead angles AI and A2 of the FJ if roller 24 are set such that the feed pitch P1 per rotation of the drive shaft 11 is 5 mm, and the feed pitch P
2 becomes II, the lead angle becomes ^1. when the motor 15 rotates at high speed. By setting ^2, the maximum speed changes from 100mm/sec to 20mm/sec. Also, when the motor 15 is precisely rotated, the lead angle is set to 81.
By setting ゜82, the minimum resolution is 0.5μm/
Pulse, change to 0.1 μm/pulse. in this way,
By adjusting the lead angle of the friction roller 24 in addition to switching the operation of the motor 15 itself, it is possible to adjust the speed of high-speed feed and finely adjust the resolution of precision feed, making it possible to perform a variety of feed operations depending on the situation.

In addition, the two members that move relative to each other to which the friction feed mechanism 1 is applied are not limited to the bed lO and the table 20, but may also be, for example, the column and hen of a machine tool, and the present invention is applicable to various feed operation parts. It is possible.

[Effects of the Invention] As explained above, according to the friction feed mechanism of the present invention, 1. The feed pinch can be changed accurately and easily, the feed pitch after the change can be accurately maintained, and the structure can be simplified. .

[Brief explanation of the drawing]

FIG. 1 is a side view showing one embodiment of the present invention, FIG. 2 is a sectional view taken along the line ■-■ in FIG. 1, and FIG. 3 is a side view showing another embodiment of the present invention. Figure 4 shows IV-IV in Figure 3 above.
It is a sectional view showing a line. 1... Friction feed mechanism, 2... Guide mechanism, to, 2
0... (Bed and table which are two members that move the seal, 11... Drive shaft, 21. 31... Support body, 2
2.23.33... Piezoelectric element, 24... Friction roller, 25... Operating device, 26.30... Angle adjustment means.

Claims (1)

[Claims] (1) One of the two relatively movable members is provided with a rotating drive shaft, and the other member is provided with a friction roller that rolls on the circumferential surface of the drive shaft, and the friction roller is set at a lead angle with respect to the drive shaft. A friction feed mechanism, characterized in that it is supported on a support that is rotatable in changing directions, and that the support is provided with an angle adjustment means that rotates the support by displacement of a piezoelectric element.