JPH01316145A - Friction feed mechanism - Google Patents

Abstract

PURPOSE:To accurately and simply perform the switching of a plurality of feed pitches by providing a rotating driving shaft at one of two members capable of relative moving and providing a plurality of friction rollers slantly arranged on the circumference of the respective above driving shafts, rotatably and at different lead angles each other. CONSTITUTION:Voltage is added to a piezoelectric element by an operating device to lower a holding body 21 by its displacement so as to press a friction roller 23 on the circumference of a driving shaft. The driving shaft is rotated, the roller 23 follows the rotation of the driving shaft to roll on the circumference to move in the axial direction of the driving shaft by a feed pitch according to a lead angle A1 for transferring a table 20 to a bed 10 at a high speed. In the meantime, when the table 20 is reached close to an aimed position, the motor 15 is stopped, the added voltage is switched from the piezoelectric element 25 to 26 to separate the roller 23 from the drive shaft and the holding body 22 is lowered to press a friction roller 24 to the driving shaft. Hereupon, the driving shaft is rerotated to accurately move the roller 24 in the axial direction of the driving shaft by a feed pitch according to a lead angle A2.

Description

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

[Conventional technology]

BACKGROUND ART Conventionally, in three-dimensional measuring instruments, machine tools, and the like, a feeding mechanism is provided for each movable direction to adjust the relative position of a table on which a work is placed, a probe, or a head that supports a tool.

Since such a feeding mechanism requires high precision, a method is often used in which a spiral 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 thread shape formed on the drive shaft needs to be finished with high precision, which increases manufacturing costs, and there are problems in that the feed pitch 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 rolled on the circumferential surface of the drive shaft, and feeding is performed by the component force in the direction of the drive shaft that is generated 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. The feed pitch can be arbitrarily set or changed depending on the angle (angle formed).

[What the invention tries to solve! 1ull) Toko, Lode,
In the above-mentioned friction feed mechanism, the Fj friction crawler lead angle and feed pitch can be adjusted steplessly even during operation, and it is possible to switch between high-speed feed and precision feed with a simple operation. .

However, when the friction roller is movable, a highly precisely controlled angle adjustment means is required to accurately set the friction roller to the desired glide angle. 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 and easily switch between a plurality of feed pitches and has a simplified structure.

(Means for Solving the Problems) In the present invention, the feeding operation of the friction feeding mechanism depends on frictional rolling between the friction roller and the circumferential surface of the drive shaft, and the friction roller is separated from the drive shaft even slightly. This method was developed by focusing on the fact that the feeding operation by the friction roller becomes ineffective. That is, one of two relatively movable members is provided with a rotating drive shaft, and the other member is provided with a plurality of friction rollers that can roll on the circumferential surface of the drive shaft and are arranged at inclinations at mutually different lead angles. , these friction rollers are each supported by independent supports, and each support is provided with a separating means that can press each of the 11j friction rollers against the circumferential surface of the drive shaft by displacement of a piezoelectric element. It has a rubbing R structure.

As the piezoelectric element of the present invention, one in which a piezoelectric material such as Pb(Zr-Ti)Oi-based ceramics or crystals such as quartz or LiNb0+ is sandwiched between a pair of electrodes 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.

In addition, the detachment means may have a structure in which a piezoelectric element is interposed in a part of a support body that can move forward and backward toward the drive shaft, and the support body can advance toward the drive shaft by displacement due to energization, or a support that can freely swing. A structure can be used in which a piezoelectric element is provided at one end of the body and a friction roller supported at the other end is rotated toward the drive shaft.

On the other hand, when arranging the plurality of friction rollers, supports, and piezoelectric elements, they 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.

In addition, in cases where it is desired to avoid a single grudge on the drive shaft, a pair of friction rollers having the same lead angle may be arranged opposite to each other with the drive shaft in between, and tangentially applied from both sides at the same time with approximately the same strength. Alternatively, a guide bearing for preventing deflection may be disposed on the opposite side of the drive shaft.

[Effect]

In the present invention configured as described above, the lead angle of each friction roller is set accurately to give a desired feed pinch, and an arbitrary friction roller is selected by the contact/separation means to move around the drive shaft. By pressing against the surface, the feed pinch can be easily switched, and the feed pitch of each friction roller can be accurately maintained without changing the lead angle at the time of switching. Further, by employing a piezoelectric element to press the friction roller, ease of operation and simplification of the structure are realized, thereby achieving the above object.

〔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 bed IO 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 bed 10. Along with being
It is driven by a friction feed mechanism 1 based on the present invention and is capable of reciprocating movement.

A drive shaft 11 is provided along the guide mechanism 2 in the head IO. This drive shaft 11 has a smooth peripheral surface, and bearings 12.1 are provided near both ends.
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 cambling 14.

The table 20 has a substantially gate-shaped cross section, and on the back side of its upper surface, two supports 21.
22 are provided, each of which is attached so as to be movable forward and backward toward the drive shaft 11. Friction rollers 23 and 24 are rotatably attached to the tips of these supports 21 and 22, respectively.
3.24 U rotation axis is lead angle AI and lead angle A2 (A2<A
I).

Between these supports 2L 22 and the table 20 are laminated piezoelectric elements 25°26 having electrodes on the front and back sides, respectively.
are interposed, and each piezoelectric element 25 , 26 is displaced in response to a voltage applied from an operating device 27 connected to the electrode, and moves the support 21 , 22 and the friction roller 23 , 24 to the drive shaft 11 . It is possible to advance and retreat toward the target.

Here, each piezoelectric element 25.26 normally lifts up each friction roller 23.24 and holds it with a space between it and the circumferential surface of the drive shaft 11, but when the friction roller 23.24 is at maximum displacement due to energization, the friction roller 23.24 is set so as to be brought into pressure contact with the circumferential surface of the drive shaft 11 with sufficient contact pressure.

Note that the operating device 27 applies a voltage to each piezoelectric element 2s, 26.

Only one of the piezoelectric elements 25, 26 can be selected when applying the pressure, and a plurality of friction rollers 23, 24 are prevented from coming into pressure contact with the drive shaft 11 at the same time, and these piezoelectric elements 25, 26 and The actuating device 27 constitutes a contacting and separating means 28,29 for each friction roller 23,24.

In this embodiment configured as described above, high-speed feeding and precision feeding are continuously performed by the following procedure.

First, in order to move the table 20 to the vicinity of the target position, the moving/separating means 28 is selected to perform high-speed feeding.

That is, a voltage is applied to the piezoelectric element 25 by the operating device 27, and the support body 21 is lowered by the displacement thereof, and the friction roller 23 is brought into pressure contact with the circumferential surface of the drive shaft 11. Here, when the drive shaft 11 is rotated by the motor 15, the grinding roller 23 follows the rotation of the drive shaft 11 and rolls on the circumferential surface, and the feed pitch Pi = πd according to the lead angle AI.
tan(Al) (d is the diameter of the drive shaft 11) to move in the axial direction of the drive shaft 1, and feed the table 20 with respect to the head 10 at high speed at a feed pitch P1.

On the other hand, if the table 20 reaches near the target position,
The motor 15 is stopped to stop the rotation of the drive shaft 11, and the contact/separation means 29 is selected instead of the contact/separation means 28 to perform a 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, the friction roller 23 is separated from the drive shaft 11, and the support body 2 is moved instead.
2 is lowered to press the friction roller 24 against the drive shaft 11. Here, when the rotation of the drive shaft 11 by the motor 15 is restarted, the friction roller 24 has a feed pitch P2=rt d tan (A2) (P2<PI
) in the axial direction of the drive shaft 11 to precisely feed the table 20 to the bed IO at a feed pitch P2.

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

That is, dedicated friction rollers 23 and 24 are provided for high-speed feed and precision feed, respectively, and the respective lead angles AI are set.

By changing the pitch 82, it is possible to feed the table 20 with respect to the bed 10 at different feed pitches PI and P2 even if the rotational speed of the drive shaft 11 is the same.

Therefore, there is no need for a speed change mechanism or the like that changes the rotational speed of the drive shaft 11 in order to switch the feed speed, and the structure can be significantly simplified compared to conventional feed mechanisms that use a speed change mechanism or the like.

In addition, the lead angle Al of each friction roller 23, 24, A2
The selection is arbitrary, and settings such as the feed pinch Pi for high speed and the feed pitch P2 for precision can be freely set. If you set it.

It is also possible to use the rotating direction of the motor 15 to change the forward and reverse directions of the table 20 while keeping it constant.

Furthermore, the lead angles AI and A2 of each friction roller 23 and 24 can be set independently, and changes do not affect the angles of other friction rollers, making adjustment work easier when setting and changing. It can be done.

On the other hand, since the selection and cancellation of each feed speed in the friction feed mechanism 1 is performed by moving the friction rollers 23 and 24 toward and away from the drive shaft 11, switching between each feed operation can be made extremely smoothly.

In addition, since the contact and separation operations of each FJ friction roller 3.24 are performed by the corresponding piezoelectric elements 25.26, switching of the feed speed is performed by the piezoelectric element 2, which is energized from the operating device 27.
By selecting 5.26, it can be performed extremely easily, and since the operation itself is a simple winching, it can be easily automated.

Furthermore, since the distance between the friction rollers 23, 24 and the drive shaft 11 to release them only needs to be small, the displacement of each support 21, 22 does not need to be very large. Sufficient switching operation is possible by displacement of each laminated piezoelectric element 25°26 in the thickness direction.

In addition, by utilizing the rigidity of the piezoelectric elements 25, 26 themselves and interposing each piezoelectric element 25, 26 between the support body 21, 22 and the table 20 to have a function as a structural member, F! J! The structure that supports the rubbing roller 234 can be further simplified.

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

In other words, the number of friction rollers provided in the friction feed mechanism l is 2.
The lead angle is not limited to 1, but may be increased or decreased as appropriate depending on the number of steps of the required feed speed, etc., and the lead angles set for each may be adjusted as appropriate, not only for high-speed feed or precision feed.

Further, the arrangement of the friction rollers is similar to that of the previous embodiment, with the drive shaft 1
The arrangement is not limited to the arrangement according to No. 1, and may be changed as appropriate in implementation.

For example, in the embodiment shown in FIG.
Friction rollers 23 and 24 are arranged facing each other on both sides of the drive shaft 11, and each is configured to alternately come into pressure contact with the drive shaft 11 by piezoelectric elements 25 and 26. In addition, in this example,
Components similar to those in the embodiment shown in FIG. 1 are designated by the same reference numerals, and their explanation will be omitted for the sake of brevity.

According to such an arrangement, the height of the top surface of the table 20 can be lowered, and the axial dimension of the drive shaft 11 can be shortened, so that the table 20 can be made more compact.

The arrangement of the friction rollers is not limited to two opposing positions, but may be at any angular position, or three or more friction rollers may be arranged in the circumferential direction around a predetermined position of the drive shaft. Even when using a friction roller, the axial dimension of the drive shaft can be shortened.

Further, the axial arrangement and the circumferential arrangement may be combined, for example, by adopting an arrangement of three rows of two friction rollers in the circumferential direction along the drive shaft,
In addition to being more compact, it is possible to increase the degree of freedom in design.

Furthermore, in the embodiment shown in FIG. 3, a plurality of sets of friction rollers are arranged opposite to each other with the drive shaft in between, and the lead angles of the friction rollers of each opposing month are made to be different from each other. They may be pressed together at the same time.

In such a case, the deflection of the drive shaft due to the pressure contact of the friction rollers can be mutually canceled out, which is effective when a pressure contact force of the friction rollers against the drive shaft is required, such as in a feeding operation under a high load.

On the other hand, the structure of the support body may be selected as appropriate in implementation, but it is preferable that it has appropriate strength so that it can operate smoothly according to the displacement of the piezoelectric element and does not buckle or cause unnecessary deformation. It is desirable that the structure is such that at least the lead angle of the friction roller can be maintained accurately.

Furthermore, the support body is not limited to a structure that is attached via a piezoelectric element and can move forward and backward, but may also be a swing arm-like structure or a lever-type structure that is supported rotatably at the negative point.

For example, in the embodiment shown in FIG. 4, the rod-shaped supports 31 and 32 are rotatably supported at their substantially middle portions on the inner surface of the table 20, and the lower ends of the rod-shaped supports 31 and 32 are arranged opposite to each other with the drive shaft 11 interposed therebetween. Ta l ¥! t90-ra 33.34 are supported at equal lead angles, and the upper ends of each support body 31.32 are rotatably connected to both ends of a piezoelectric element 35 which is formed into a substantially columnar shape and is displaceable in the longitudinal direction. A separating means 30 is formed. Although not shown, a plurality of sets of the separating 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.

In addition, in other parts of this embodiment, the same parts as those in the embodiment shown in FIG.

According to such an arrangement, the displacement of the piezoelectric element 35 causes each of the supports 31.32 to rotate, and the pair of friction rollers 33.32 to rotate.
By sandwiching the drive shaft 11 with 34, the drive shaft 11 is pressed against the drive shaft 11, and a feeding operation can be performed based on each lead angle. In addition, the pressure contact force generated by the piezoelectric element 35 is
Since the friction rollers 33 and 34 are evenly distributed, deflection of the drive shaft 11 caused by mutual pressure can be reliably offset.

By the way, the drive shaft 11 of the friction feed mechanism 1 is not limited to one that is driven at a constant rotation speed, but may also be one that is rotationally driven by a -motor 15 of a variable rotation speed type. A wide range of feed rate changes can be obtained.

As an example, a case will be described in which a four-phase high print type 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 chigonpa, and can realize precise rotation with a minimum resolution of about 10,000 pulses/rotation when driven by a constant voltage mini-temperature. Here, the friction roller 23.
24, the lead angles Al and A2 are set such that the feed pitch P1 per revolution of the drive shaft 11 is 5 mm, and the feed pitch P2 is 5 mm.
If the motor 15 is adjusted so that it becomes II,
By selecting the friction rollers 23 and 24 when rotating at high speed, the maximum speed can be set to 100 mm/see or 20 mm/s.
It is possible to switch between ec and ec, and when the motor 15 is precisely rotated, the minimum resolution can be set to 0.5 μm/pulse or 0.5 μm/pulse.
It becomes possible to switch between 1 μm/pulse. Therefore, in addition to switching the motor 15 itself, the friction roller 23.2
By selecting 4, two kinds of precision positioning operations can be performed: high-speed and medium-speed adjustment operations, medium-precision feed, and high-precision feed, and various settings can be made depending on the situation.

Further, in the embodiment described above, the drive shaft 11 was stopped each time the feed speed was changed, but when neither of the friction rollers 23 and 24 is in pressure contact with the drive shaft 11, the table 2
Since the feed operation of 0 is also canceled, the drive shaft 11
In this case, since the motor 15 continues to rotate at all times, it is only necessary to accurately maintain a constant rotation, which makes it easy to control the rotation speed, and reduces the waiting time for rotation stabilization when restarting rotation, etc. This eliminates the need for each friction roller 23, allowing for speedy switching of feeding operations.
．． 24 is in frictional contact with the drive shaft 11, so when it comes into contact with the drive shaft 11, which is rotating at a constant rate, it can slip as appropriate to alleviate the impact movement, thereby reducing the shock given to the table 20 and the various structural parts. This unreasonable force can be suppressed to a low level.

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

〔Effect of the invention〕

As explained above, according to the friction feed mechanism of the present invention, it is possible to accurately and easily switch between a plurality of feed pitches, and the structure jh 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 top view of the embodiment, and FIGS. 3 and 4 are sectional views showing different embodiments of the present invention. 1... Friction feed mechanism, 2... Guide mechanism, to, 2
0... Bed and table which are two members that move relative to each other, 11... Drive shaft, 21.22.31.32...
Support body, 23.24° 33, 34...Friction roller, 2
5.26.35... Piezoelectric element, 27... Operating device,
28.29.30...Detachment means.

Claims (1)

[Claims] (1) One of two relatively movable members is provided with a rotating drive shaft, and the other member is provided with a plurality of friction rollers that can roll on the circumferential surface of the drive shaft and are inclined at different lead angles. The friction rollers are each supported by independent supports, and each support is provided with a contact/separation means that can press each friction roller against the circumferential surface of the drive shaft by displacement of a piezoelectric element. Friction feed mechanism.