JP2010101469A - Frictional driving device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a frictional driving device with extended wear life by avoiding lowering of thrust due to an excessive preload. <P>SOLUTION: This frictional driving device includes a driving roller 3 and a slide bar 2, with which the peripheral surface of the driving roller 3 is brought into contact in the state of giving a required preload, so that the slide bar 2 can be relatively moved by rotation of the driving roller 3. Relation between a slip factor and the generated thrust of the driving roller 3 and the slide bar 2 and relation between the slip factor and the preload are previously obtained, In operation of the frictional driving device, the slip factor of the driving roller 3 and the slide bar 2 is set to a required slip factor in a range not exceeding a value, which takes the peak of the generated thrust, and a preload led from the relation with the preload based on the slip factor is applied between the driving roller 3 and the slide bar 2. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an operation method of a friction drive device including a mechanism for moving a slide bar, which is disposed between a drive roller and a backup roller, by relative rotation of the drive roller.

  In recent years, in precision machines that perform precise positioning such as semiconductor-related manufacturing and inspection, when moving a moving body such as a transfer stage (transfer table) with respect to a fixed part of the machine, For example, it may be required to perform positioning with an accuracy of the order of μm or less.

  Therefore, as a driving device for moving the moving body in the precision machine as described above and accurately positioning the moving body and increasing the stroke, FIGS. 4 and 5 are used. (B) A friction drive device as shown in (b) has been proposed.

  That is, the friction drive device shown in FIG. 4 and FIGS. 5A and 5B includes a slide bar 2 extending in the moving direction of the transfer table 1, and one side surface of the slide bar 2 on the transfer table 1 side. One side roller 3 to be brought into contact with, a plurality of other side rollers 4 to be brought into contact with the other side surface of the slide bar 2 at both front and rear positions in the table moving direction with respect to the one side roller 3, and the one side roller 3 And a displacement mechanism 5 such as a piezo actuator for individually displacing all or any one of the other side surface rollers 4 in a direction perpendicular to the table moving direction, and each of the rollers 3 on the one side surface side and the other side surface side. A driving motor 7 is provided that is connected to any one of the rollers 3 through a flexible joint 6 and rotationally drives the roller 3 as the driving roller 3.

  Further, the displacement mechanism 5 of the drive roller 3 is equipped with a load cell 8 that receives a reaction force when the drive roller 3 is pressed against the slide bar 2 by the displacement mechanism 5. It is possible to detect the value of the pre-pressure when the is pressed against the slide bar 2.

  According to the friction drive apparatus having the above-described configuration, the drive roller 3 is placed on one side of the slide bar 2 by the displacement mechanisms 5, and the other rollers 4 are used as backup rollers 4. The drive roller 3 and the slide bar 2 are brought into contact with each other by rotating the drive roller 3 by forward / reverse drive of the drive motor 7 in a state where each side is pressed with a required pre-pressure. The conveying table 1 as the moving body can be moved in the longitudinal direction of the slide bar 2 by utilizing the friction acting on the surface. Further, the positioning of the conveying table 1 is accurately performed by the friction driving device. In order to perform well, as the position detector for detecting the position of the transport table 1, for example, the above-mentioned scan functioning as a guide mechanism for the transport table 1 A position comprising a detection head 10 attached to the upper surface of the id bar 2 so as to extend in the longitudinal direction of the slide bar 2, and a linear scale 11 attached to a required portion of the transport table 1 in a non-contact manner with the detection head 10 It has also been proposed to provide a detection linear encoder 9 (see, for example, Patent Document 1).

  By the way, in the friction drive device as described above, due to its mechanism, a minute rolling slip occurs at the contact portion between the drive roller 3 and the slide bar 2.

  Therefore, in order to perform stable positioning in the friction drive device, it is advantageous to reduce the slip at the contact portion between the drive roller and the slide bar. Therefore, conventionally, as a measure for suppressing the slip between the drive roller and the slide bar, a method of increasing a pre-pressure when the drive roller is pressed against the slide bar has been employed (for example, Patent Documents). 2).

  In addition, in the previous application (Japanese Patent Application No. 2008-145321), the present inventor can precisely measure the traction coefficient between two members that perform rolling and sliding in a friction drive device or the like, and also performs a durability verification test. As a test apparatus capable of doing so, a traction measurement test apparatus as shown in FIG. 6 has been proposed.

  In the traction measurement test apparatus shown in FIG. 6, the output side of the AC servo motor 14 is connected to a drive side rotary shaft 13 to which a cylindrical drive side test piece 12 is detachably attached. Further, a torque meter 17 and a load torque variable brake device 18 are connected to a load side rotating shaft 16 to which a cylindrical load side test piece 15 disposed on the side of the driving side test piece 12 is detachably attached. At the same time, a rotary encoder 19 is provided at a required portion of the load side rotating shaft 16. Further, the preload corresponding to the mass of the weight 21 to be used is applied to the outer peripheral surface of the driving side test piece 12 attached to the driving side rotating shaft 13 on the outer peripheral surface of the load side test piece 15 attached to the load side rotating shaft 16. It is set as the structure provided with the pre-pressure provision means 20 for pressing and making a surface contact in the state which attached | subjected.

  According to the traction measurement test apparatus having the above-described configuration, the drive-side test piece 12 and the load-side test piece 15 are adjusted by adjusting the mass of the weight 21 used in the preload applying means 20 to a required mass. After the required pre-pressure is applied and pressed, the AC servomotor 14 rotates the driving-side test piece 12 integrally with the driving-side rotating shaft 13 at a constant rotational speed, and the driving-side test is performed. A rotational driving force is transmitted to the load side test piece 15 that is in surface contact with the piece 12, and the load side test piece 15 is rotated integrally with the load side rotating shaft 16.

In this state, when measuring the traction coefficient between the test pieces 12 and 15 on the load side that is the driving side and the driven side, a load torque variable type connected to the load side rotating shaft 16 is used. The load of the brake device 18 is gradually increased, and at this time, the traction coefficient μ and the slip rate λ are measured by the following equations based on the obtained data.
μ = T _b / (P · R _b )
λ = {(N _m −N _b ) / N _m } × 100
here,
T _b : Load side torque [N · m]
P: Pressure [N]
R _b : Load-side roller diameter [m]
N _m : Drive side rotational speed [rpm]
N _b : Load side rotational speed [rpm]
It is.

  Thereafter, by plotting the traction coefficient μ on the vertical axis and the slip ratio λ on the horizontal axis, a traction curve as shown in FIG. 7 can be obtained. As a value reaching the linear limit point X in the traction curve, The value of the traction coefficient that enables transmission of power with almost no slip can be obtained.

On the other hand, when the durability verification test of each of the test pieces 12 and 15 is performed, the drive side test piece 12 is rotated at a constant rotational speed integrally with the drive side rotary shaft 13 by the AC servo motor 14 in the same manner as described above. After driving, the rotational driving force is transmitted to the load side test piece 15 in surface contact with the drive side test piece 12 so that the load side test piece 15 rotates together with the load side rotation shaft 16. The load side torque is constantly monitored by the torque meter 17, and the load torque variable brake device 18 is feedback controlled so that the load side torque measured by the torque meter 17 is constant at a required value. Thus, the constant load operation is performed, and the constant load operation is continued for a required period, for example, about two weeks. Then, for each of the test pieces 12 and 15 on the drive side and the load side, the wear volume showing wear characteristics from the wear volume V [m ³ ] and the rolling distance L [m] obtained from the load side rotational speed, respectively. The ratio α [m ³ / m] can be obtained by the following equation.
α = V / L

JP 2008-103663 A Japanese Patent Publication No. 2-15742

  However, as shown in Patent Document 2, the technique of increasing the preload when pressing the drive roller against the slide bar in order to reduce the sliding between the drive roller and the slide bar is caused by wear of the roller. The actual situation is that no consideration is given to the reduction of the device life.

  That is, in Patent Document 2, it is said that the slip rate is reduced when the preload is increased, but an increase in the preload leads to an increase in the amount of wear. For this reason, if it is a friction drive that can only be driven for a short period of time, it is considered possible to adopt a technique to reduce slip by ignoring the amount of wear and increasing the preload as described above. In a friction drive device that is expected to be used for a long time, it is difficult to take the above-described method.

  Moreover, as will be described later, according to the knowledge obtained by the present inventor, if the preload when pressing the drive roller against the slide bar is excessively increased, the slip ratio will increase. Therefore, there is also a problem that there is a concern that even if the preload when pressing the drive roller against the slide bar is increased, the slip rate may not necessarily be reduced.

  Therefore, the present invention intends to provide a method for operating the friction drive device so that the wear life of the friction drive device can be improved and thrust reduction due to excessive pressurization can be avoided.

  In order to solve the above-mentioned problems, the present invention, corresponding to claim 1, contacts the slide bar with the outer peripheral surface of the drive roller with a required pre-pressure, and the slide is driven by the rotation of the drive roller. In the operation method of the friction drive device that allows the bar to move relative to the drive roller, the correlation between the slip rate of the drive roller and the slide bar and the generated thrust, and the slip rate and the above Obtain the required slip rate so that the slip rate of the drive roller and the slide bar is within the range that does not exceed the peak value of the generated thrust. For this reason, a friction driving device operating method in which a pre-pressure for this purpose is derived from the correlation between the slip ratio and the pre-pressure and is applied between the driving roller and the slide bar.

According to the operation method of the friction drive device of the present invention, the following excellent effects are exhibited.
(1) The outer peripheral surface of the drive roller is brought into contact with the slide bar with a required preload, and the slide bar can be moved relative to the drive roller by the rotational drive of the drive roller. In the operation method of the friction drive device, the correlation between the slip rate of the drive roller and the slide bar and the generated thrust, and the correlation between the slip rate and the preload are obtained in advance, and the drive roller and the slide bar are obtained. The preload for obtaining the required slip rate is a correlation between the slip rate and the preload so that the slip rate is a required slip rate in a range not exceeding the peak value of the generated thrust. Since it is more guided and applied between the drive roller and the slide bar, the slip rate between the drive roller and the slide bar is reduced when the friction drive device is operated. And vision, can always be set to slip rate reduction of thrust generated by the excessive preload force can be prevented. Therefore, it is possible to avoid a reduction in thrust due to excessive pressurization.
(2) Moreover, since it is possible to prevent a possibility that the amount of wear increases due to excessive preload, it is possible to improve the wear life.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

  1 (a) (b) to FIG. 3 show an embodiment of the operation method of the friction drive device of the present invention, which is as follows.

  That is, as shown in FIGS. 1 (a) and (b), the apparatus used for carrying out the operation method of the friction drive device of the present invention is a slide bar as shown in FIGS. 2 for accurately detecting the amount of rotation of the outer peripheral surface of the drive roller 3 in a friction drive apparatus including a position detection linear encoder 9 as a position detection mechanism for detecting the position of the transport table 1 in the longitudinal direction of 2. As a rotation amount detection mechanism, for example, a rotary encoder 23 provided on the output shaft side of the drive motor 7 and a signal from the rotary encoder 23 are input, and the rotation angle (rotation) of the drive roller 3 by the rotary encoder 23 is input. The rotation amount detection mechanism 22 is provided which includes a calculator 24 that calculates the product of the number of the drive roller 3 and the circumferential dimension of the drive roller 3.

  Further, a signal from the position detection linear encoder 9 and a signal from the rotation amount detection mechanism 22 are input, and based on each signal, a slip ratio between the driving roller 3 and the slide bar 2 is obtained. The sliding rate is monitored, and a control device 25 is provided for controlling the pre-pressure that presses the drive roller 3 against the slide bar 2.

  Other configurations are the same as those shown in FIGS. 4 and 5 (a) and 5 (b), and the same components are denoted by the same reference numerals.

  Here, the derivation | leading-out of the operating method of the friction drive device of this invention is explained in full detail.

Using the traction measurement test apparatus as shown in FIG. 6 proposed by the present applicant in the previous application, the drive side test piece 12 and the load simulating the drive roller 3 and the slide bar 2 in the friction drive apparatus, respectively. As a side test piece 15, for example, to simulate the case where the outer peripheral surface of the driving roller 3 in the friction drive device and the driving roller contact surface of the slide bar 2 are both coated with chromium nitride (CrN), the outer peripheral surface is CrN. Using the coated drive side test piece 12 and the load side test piece 15 whose outer peripheral surface is CrN coated, the traction coefficient μ and the slip ratio λ are calculated, and the durability of the drive side test piece 12 and the load side test piece 15 is calculated. A wear verification (amount of wear) V is obtained by conducting a property verification test, and a thrust F [N] represented by the following equation is obtained in advance.
F = μ · P
here,
μ: Traction coefficient P: Preload [N]
It is.

  Further, when the driving side test piece 12 and the load side test piece 15 coated with CrN are used under the same surface pressure, for example, the load is applied by the brake device 18 in a state where the surface pressure is constant at a required pressure. Fig. 2 shows a test with varying slip ratio λ by changing the torque, the change in thrust F and wear volume V using this slip ratio as parameters, and the horizontal axis plotted as slip ratio λ. A graph like this was obtained.

  From the results shown in FIG. 2, when the surface pressure preload P is constant, the wear volume V indicated by the line a obtained by linearly approximating the points plotted with ◇ in FIG. 2 is almost linear as the slip ratio λ increases. 2, the thrust F indicated by the approximate curve b of the point plotted by □ in FIG. 2 takes a peak when the slip rate λ reaches a certain value λx, and when the slip rate λ increases further, It became clear that the thrust F gradually decreased.

  Further, the graph shown in FIG. 3 was obtained by plotting the correlation between the preload P and the slip ratio λ obtained in the above test with the preload P as the horizontal axis and the slip ratio λ as the vertical axis.

  From the results shown in FIG. 3, it is clear that the preload P and the slip ratio λ have a correlation indicated by a monotonic increase in the linear line.

  In view of the above points, in the operation method of the friction drive device of the present invention, the driving roller 3 and the slide bar 2 used in the friction drive device are simulated in advance using a traction measurement test device as shown in FIG. Using the drive-side test piece 12 and the load-side test piece 15, the graph of the change in the generated thrust F having the slip ratio λ as the parameter shown in FIG. 2 as a parameter, and the same preload as shown in FIG. A graph representing the correlation between P and the slip rate λ is stored in the database of the control device 25.

  Further, the control device 25 obtains the slip ratio λ when the friction drive device is operated based on the input signal from the position detection linear encoder 9 and the input signal from the rotation amount detection mechanism 22. The slip rate λ is the same as that shown in FIG. 2 stored in the above-mentioned database, but the value of the slip rate when the generated thrust F reaches a peak in the graph of the change in the generated thrust F using the slip rate λ as a parameter. The slip ratio λ is set within a range of λx or less.

  Specifically, when generation of a large thrust F is desired, the slip rate λ is set to the slip rate value λx when the generated thrust F takes a peak value in FIG. Further, when a required wear amount considering the life is desired, the slip rate λ when the slip rate λ is not more than λx in FIG. 2 and the wear volume V corresponding to the required wear amount is taken. It is set to.

  Further, when the desired slip rate λ is set as described above, the control device 25 is based on a graph representing the correlation between the preload P and the slip rate λ similar to that shown in FIG. The pre-pressure P required to obtain the set slip rate λ is obtained, and the obtained pre-pressure P and the pre-pressure when the drive roller 3 is pressed against the slide bar 2, that is, the drive roller The expansion / contraction operation of the displacement mechanism 5 provided in each of the drive roller 3 and the backup roller 4 is controlled so that the pre-pressures detected by the load cell 8 provided in the displacement mechanism 5 installed on the 3 side coincide with each other. It is like that.

  Therefore, when operating the friction drive device having the above configuration, if the control device 25 requires a large thrust F or a wear amount considering the device life is desired, During the operation of the friction drive device, the slip rate λ obtained by the control device 25 based on the input signal from the position detection linear encoder 9 and the input signal from the rotation amount detection mechanism 22 is an appropriate value considering wear. The slip rate λ is always set to the slip rate λ that prevents the generated thrust F from being lowered due to the excessive preload P.

  Thus, according to the operation method of the friction drive device of the present invention, the slip rate λ of the drive roller 3 and the slide bar 2 is monitored, and an appropriate preload is obtained according to the correlation with the preload P obtained in advance. Since P can be applied, it is possible to avoid an increase in wear life and a reduction in thrust due to excessive pressurization.

  Further, since the correlation between the preload P and the slip rate λ is known, the wear state of the drive roller 3 and the slide bar 2 and the wear life can be predicted without changing the preload P. It can be advantageous.

  Further, according to the friction drive device shown in FIGS. 1A and 1B, when the roller diameter decreases due to wear of the drive roller 3, the rotation amount detection mechanism 22 determines the circumferential dimension of the drive roller 3 and the rotary. Since the value calculated by integrating the rotation angle (number of rotations) of the driving roller 3 by the encoder 23 is small, the slip rate λ obtained by the control device 25 based on this value is apparently increased. become. Therefore, it is possible to estimate the replacement time of the drive roller 3 by monitoring the increase in the slip rate λ.

  The present invention is not limited only to the above-described embodiment, and the drive roller 3 is driven to rotate in a state where the drive roller 3 is brought into contact with the slide bar 2 with a required pre-pressure. Any type of friction drive device that is moved relative to the slide bar 2 can be applied to a friction drive device of a type other than that shown in FIG. 4 and FIGS. May be.

  Further, the drive roller 3 and the slide bar 2 may be applied to a friction drive device of a type provided with the drive roller 3 and the slide bar 2 of any material other than having a coating made of chrome nitride. In this case, the traction performance test apparatus shown in FIG. 6 using the drive side test piece and the load side test piece simulating the drive roller 3 and the slide bar 2 actually used in the friction drive apparatus is shown in FIG. The control device 25 obtains a graph showing the relationship between the thrust F and the wear volume V using the slip rate λ as a parameter, and a graph showing the correlation between the preload P and the slip rate λ as shown in FIG. You can save it in the database.

  As long as the position detection mechanism of the conveyance table 1 can accurately detect the position of the conveyance table 1 in the longitudinal direction of the slide bar 2, any type of position detection mechanism other than the position detection linear encoder 9 is adopted. Also good.

  As long as the rotation amount detection mechanism 22 of the drive roller 3 can accurately detect the rotation amount of the outer peripheral surface of the drive roller 3, any type of rotation amount detection mechanism other than the configuration including the rotary encoder 23 and the calculator 24 is possible. 22 may be adopted.

  Of course, various changes can be made without departing from the scope of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows an embodiment of an operation method for a friction drive device according to the present invention, where (A) is a schematic cut side view of the friction drive device as seen from one side in the longitudinal direction of the slide bar, and (B) is a control block. FIG. It is a graph which shows the relationship between the thrust of a friction drive device, and a wear volume by using a slip ratio as a parameter. It is a graph showing the correlation of the pre-pressure of a friction drive device and a slip ratio. It is a general | schematic cutting top view which shows the friction drive device proposed conventionally. (A) is an AA direction arrow line view of FIG. 4, (b) is a figure which expands and shows the B section of (a). It is a schematic perspective view which shows the test apparatus for traction measurement which the present applicant has proposed by the previous application. FIG. 7 is a diagram showing a traction curve obtained by plotting the traction coefficient μ obtained by the test apparatus of FIG. 6 on the vertical axis and the slip ratio λ on the horizontal axis.

Explanation of symbols

2 Slide bar 3 Drive roller

Claims (1)

  A friction drive device in which the outer peripheral surface of the drive roller is brought into contact with the slide bar with a required pre-pressure, and the slide bar can be moved relative to the drive roller by rotational driving of the drive roller. In this driving method, the correlation between the sliding rate of the driving roller and the slide bar and the generated thrust, and the correlation between the sliding rate and the pre-pressure are obtained in advance, and the sliding rate of the driving roller and the slide bar. Therefore, the prestress for obtaining the required slip rate is derived from the correlation between the slip rate and the preload so that the required slip rate does not exceed the peak value of the generated thrust. An operation method for a friction drive device, wherein the drive roller and the slide bar are applied.

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