JP3572842B2 - NC control type work rest device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a rest device that supports a cylindrical workpiece rotating on a predetermined axis against machining resistance during machining, and in particular, an upper rest arm and an upper rest arm corresponding to a relatively large workpiece to a small workpiece. The present invention relates to an NC control type work rest device suitable for use in a grinding machine capable of numerically controlling the movement of a lower rest arm.
[0002]
[Prior art]
Generally, an NC control type work rest device used for a grinding machine has an upper rest arm which abuts against the outer periphery of a cylindrical work on the opposite side of the grinding wheel to oppose a grinding resistance in a normal direction, and has a lower outer periphery of the cylindrical work. A lower rest arm that abuts against tangential grinding resistance. The feed mechanisms of these rest arms are constituted by feed screw mechanisms driven by individual servomotors, and are of a wide-area type capable of dealing with relatively large-diameter work to small-diameter work.
[0003]
The upper rest arm is configured to be moved by the same amount as the momentum of the feed screw mechanism driven by the servo motor, but the lower rest arm is pivotally supported at its base by the apparatus main body, so that the lower rest arm is pivotally supported. The momentum of the tip of the rest arm which comes into contact with the outer peripheral lower surface of the work is moved while enlarging the momentum of the feed screw mechanism driven by the servomotor. A so-called electronic gear that multiplies a movement command value to be applied to a servomotor for the upper rest arm by a predetermined deceleration coefficient in order to harmonize the momentum of the tip of the upper rest arm that comes into contact with the work and the momentum of the tip of the lower rest arm. The numerical controller is programmed to deliver a movement command value decelerated by the ratio to the servomotor for the lower rest arm. The electronic gear ratio, that is, the ratio between the command value given to the upper rest arm servomotor and the value given to the lower rest arm servomotor is determined by the pivot point of the lower rest arm to the apparatus body and the tip of the lower rest arm. It is fixedly set by the ratio of the distance b between the pivot point and the turning moment acting point set below the base of the lower rest arm to the distance a to the contact point.
[0004]
[Problems to be solved by the invention]
However, between the case where the small-diameter work W1 is supported as shown in FIG. 1A and the case where the large-diameter work W2 is supported as shown in FIG. 1B, the work supporting point at the tip of the lower rest arm 14 is SP1. , The distance a changes from a1 to a2 (a1> a2). When a conventional rest device with a constant electronic gear ratio is used as a wide-range type for a relatively small-diameter work to a large-diameter work, there is an error in the following accuracy of the lower rest arm 14 with respect to the upper rest arm 12. Therefore, in the final finishing stage of the grinding process, the workpiece is processed while being held at a position deviated vertically from the axis where it should originally exist, and this is a factor that reduces the final finishing dimensional accuracy of the workpiece. Was.
[0005]
Therefore, an object of the present invention is to provide a wide-range work rest device applicable to a small-diameter work to a large-diameter work, in which the tip of the lower rest arm extends over the moving range of the upper rest arm and the lower rest arm. The object is to be able to faithfully follow the movement of the tip of the arm.
[0006]
[Means for Solving the Problems]
The above-mentioned problems and objects of the conventional rest device are solved and achieved by the following means according to the present invention.
An NC control type work rest device according to the invention of claim 1 is characterized in that an upper rest arm guided to an apparatus main body so as to be able to advance and retreat toward the work so as to support the outer periphery of the cylindrical work on the opposite side of the processing tool; A lower rest arm whose base is pivotally supported by the apparatus main body so as to advance and retreat from substantially below the work toward the work, a feed mechanism including a first servomotor for moving the upper rest arm back and forth, An NC control type work rest device comprising a feed mechanism including a second servo motor for rotating a rest arm and a numerical control device for controlling the first and second servo motors, wherein the numerical control device includes: First command value setting means for setting a first command value which is determined according to a finish diameter of the work and controls a feed motion of one of the upper rest arm and the lower rest arm Setting a second command value which is obtained by multiplying the first command value by a predetermined coefficient or is determined according to the finishing diameter of the workpiece, and controls the other feed motion of the upper and lower rest arms. Second command value setting means for performing correction, a correction feed amount setting means for setting a correction feed amount in accordance with a feed movement amount of the other rest arm, and a second correction value by adding the correction feed amount to the second command value. Adding means for obtaining a command value, and further, one of the first and second servomotors corresponding to the one rest arm and the other rest arm based on the first command value and the corrected second command value. And control means for controlling the other of the corresponding first and second servomotors.
[0007]
In the NC control type work rest device according to the second aspect of the present invention, the one and the other rest arms are the upper and lower rest arms, respectively, and the correction feed amount setting means sets a correction value for each movement amount of the lower rest arm. And a means for reading a correction value corresponding to the amount of exercise of the lower rest arm from the correction value table, and the control means sets the first command value and the correction second command value to The first and second servomotors are respectively controlled based on the first and second servomotors.
[0008]
The NC control type work rest device according to the invention of claim 3, wherein the one and other rest arms are the upper and lower rest arms, respectively, and the correction feed amount setting means increases the unit movement amount of the lower rest arm. And a correction value table in which each incremental correction feed amount is stored in advance, and each incremental correction feed amount within a movement range in which the lower rest arm moves from a current position to a target position is read out and cumulatively added to obtain the correction feed amount. , And the control means controls the first and second servo motors based on the first command value and the corrected second command value, respectively.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
In FIG. 2, reference numeral 10 denotes a rest device main body, which is preferably fixedly provided on a table or bed 11 of a grinding machine. The upper rest arm 12 is guided to the apparatus main body 10 at the front side of the grindstone G rotatably supported on the grindstone table 13 and on the opposite side of the grindstone G so as to be able to advance and retreat with respect to the cylindrical work W. The lower rest arm 14 is pivotally connected to the apparatus main body 10 via a pin 15 at an upper end thereof so as to be pivotable in a vertical plane, and the lower end of the lower end is pivotally connected to one end of a link 16 via a pin 17a. I have. The pin 17a functions as a point of action for receiving a turning moment by a driving arm 18 described later. The other end of the link 16 is pivotally connected to a front end of the drive arm 18 via a pin 17b. The drive arm 18 is guided below the upper rest arm 12 so as to be able to advance and retreat to the apparatus main body 10 while maintaining a parallel relationship with the lower arm.
[0010]
The upper rest arm 12 and the drive arm 18 have nuts 21 and 22 fitted in holes opened at the rear ends thereof, and the nuts 21 and 22 are respectively fixed to servo motors 23 and 24 fixed to the rear surface of the apparatus main body 10. And screwed with the screw shafts 25 and 26 rotated by. Therefore, when the servomotors 23 and 24 are operated, the upper rest arm 12 and the drive arm 18 which are prevented from rotating with respect to the apparatus main body 10 by the key members 19 and 20, respectively, are advanced and retracted. Are detected by the encoders 23a and 24a attached to. In this case, the forward / backward movement of the drive arm 18 drives the lower rest arm 14 to turn via the link member 16.
[0011]
The work W is rotatably driven while being center-supported at both ends by a headstock and tailstock (not shown) installed on a table or bed 11, and while the workpiece W is being ground by the grindstone G, the upper and lower rest arms 12 and the lower rest arm 14 are supported by shoes 12a and 14a provided at the front end. The upper rest arm 12 and the lower rest arm 14 support the work W to rotate on its ideal rotation axis against normal resistance and tangential resistance generated at a grinding point which is a contact point between the work W and the grindstone G. I do.
[0012]
A computer-controlled numerical controller (hereinafter, CNC device) 30 includes a CPU 31 and a memory 32. When operating in the data input / output mode, the CPU 31 receives a numerical control program and various control data input by the operator using the keyboard 33 and the CRT 34 in an interactive manner via the interface 35 and inputs the numerical control program into the reception memory 32. The data in the memory 32 designated by the operator is displayed on the CRT 34. When operating in the setting change mode and the grinding cycle mode, the CPU 31 executes a numerical control program and outputs a command value to the servo motor drive units DUX, DUY, and DUV via the interface 36.
[0013]
The drive unit DUX controls a servomotor 41 that drives a screw shaft of a feed screw mechanism 40 that moves the grindstone table 13 forward and backward with respect to the workpiece W. The drive units DOY and DUV drive the upper and lower rest arms 12 and 14. Are controlled respectively. Feedback outputs from the encoders 41a, 23a, and 24a attached to the servomotors 41, 23, and 24 are input to the corresponding drive units DUX, DUI, and DUV, respectively, and are also input to the interface 36.
[0014]
Each drive unit calculates a corresponding encoder output to generate a speed feedback signal, and controls the operation speed of the corresponding servo motor such that the speed feedback signal matches the command speed signal. The interface 36 allows the CPU 31 to refer to the corresponding encoder output at predetermined intervals, thereby enabling the CPU 31 to perform position feedback control on the movement of each servomotor.
[0015]
3 and 4 schematically show a rest control program RCP constituting a part of a system control program stored in an unillustrated read only memory (ROM) area provided in the memory 32, and FIG. FIG. 4 is an explanatory diagram schematically showing the contents of a correction value table TBL stored in an area. The correction value table TBL is, for example, every time the radius increases by 1 mm in a range from a position supporting a work with a diameter of 75 mm (reference position) to a position supporting a work with a diameter of 35 mm (most forward position). Correction amounts (corresponding to tracking errors with respect to the upper rest arm 12) α1 to α20 of the lower rest arm 14 corresponding to the increment are registered and stored in advance at addresses N1 to N20.
[0016]
The rest device according to the present invention is controlled as described below in accordance with the rest control program RCP.
For example, in a mass production line for grinding a crankshaft for an automobile engine, a form in which a certain lot of workpieces are continuously processed and then different lots of workpieces are continuously processed is often adopted. In this case, a setting change operation is performed prior to starting the processing operation of the work of the next lot.
[0017]
When a setting change command is given in the setting change mode, steps 101 and 102 in FIG. 3 are sequentially executed, and the initial positions UPi and LPi of the upper and lower rest arms 12 and 14 are set. The initial position UPi of the upper rest arm 12 is set such that the tip of the upper rest arm 12 is retracted by a predetermined amount (for example, 20 mm) with respect to the finish diameter Dfin of the work W of the next lot to be processed (step). 101), a position obtained by multiplying the initial position UPi of the upper rest arm 12 by a coefficient (for example, 0.4) which is a predetermined electronic gear ratio is set as the initial position LPi of the lower rest arm 14 (step 102).
[0018]
The initial positions UPi and LPi (= 0.4 UPi) thus set are output to the drive units DUY and DUV in step 114. As a result, the tips of the upper and lower rest arms 12, 14 are processed next in the lot. Are positioned at positions retracted by a predetermined distance (for example, 20 mm) from the workpiece finish diameter Dfin.
[0019]
After each of the rest arms 12, 14 is retracted to the initial position, the first work W of the next lot work is loaded onto the grinding machine and is center supported on the headstock and tailstock (not shown). When the completion of loading of the work is properly confirmed by the confirmation means, the operation mode of the CNC device 30 is switched from the setting change mode to the grinding cycle mode, and a grinding cycle start command is given. The CNC device 30 operates according to the numerical control program for the work of the lot, whereby the grindstone table 13 is advanced, and at the same time, the rotation of the work W is started.
[0020]
By the execution of the grinding cycle, the plunge grinding speed of the grindstone table 13 is sequentially reduced to the rapid traverse speed, the coarse grinding feed speed, and the fine grinding feed speed as shown in FIG. 6, and the workpiece W is ground by the grindstone G. After the table 13 reaches the forward end position specified by the numerical control program, the feed is stopped for a predetermined time and spark-out grinding is performed, and after a predetermined time elapses, the grindstone table 13 is quickly moved back to the plunge grinding start position.
[0021]
During the course of the coarse grinding step in which the grinding wheel head 13 is advanced at the coarse grinding feed speed, the rest arms 12, 14 are advanced. Preferably, a rough grinding sparkout is performed prior to the advancement of the rest arms 12,14, and after this sparkout the wheel head 13 is retracted a little distance (back-off) to allow the advancement of the rest arms 12,14. You.
When a command to advance the rest arms 12 and 14 is given, step 111 in FIG. 3 is executed, and the target position UPt and advance speed UFt of the upper rest arm 12 are set according to a numerical control program. The target position UPt of the upper rest arm 12 preferably corresponds to 1/2 of the finished diameter Dfin of the work W. In the following step 112, the target position LPt and the forward speed LFt of the lower rest arm 14 are calculated. More specifically, the target position LPt and the forward speed LFt of the lower rest arm 14 are obtained by multiplying the target position UPt and the forward speed UFt of the upper rest arm 12 by a coefficient (= 0.4) which is an electronic gear ratio. Is calculated.
[0022]
In the following step 113, the correction feed amount setting program COMP shown in FIG. 4 is executed, and the position correction amount of the lower rest arm 14 is determined according to this program. More specifically, reading of the initial position LPi and target position LPt of the lower rest arm 14 calculated in steps 102 and 112, setting of an initial value Ni of an address counter AC for designating an initial read address of the correction value table TBL, and The zeroing of the correction amount register Σα and the calculation of the distance by which the lower rest arm 14 moves from the initial position LPi to the work finish diameter position (Dfin / 2 = LPt) are executed in steps 201 to 203, respectively.
[0023]
The initial value Ni set in the address counter AC in step 202 is set corresponding to the initial position LPi of the lower rest arm 14. In calculating the moving distance of the lower rest arm 14 in step 203, the target position LPt is subtracted from the initial position LPi of the lower rest arm 14, and the radius difference is obtained as an integer n. This integer value n indicates the number of steps of the read address of the correction value table TBL shown in FIG.
[0024]
In steps 204 to 208, the initial read address Ni of the correction value table TBL set in step 202 is stepped by the number of times corresponding to the integer value n, and the correction amount α read for each step is set in the correction amount register Σα Is sequentially accumulated. Then, in step 209, the correction amount in the correction amount register Σα is added to the target position LPt of the lower rest arm 14 calculated in step 112 to obtain a correction target position LPt ′ of the lower rest arm 14.
[0025]
Therefore, in step 114 of FIG. 3, the target position UPt and the command speed UFt of the upper rest arm 12 are output to the drive unit DUY, and the corrected target position LPt ′ and the speed command LFt of the lower rest arm 14 are output to the drive unit DUV. Output to Therefore, the forward movement of the distal end of the lower rest arm 14 accurately follows the forward movement of the distal end of the upper rest arm 12, and the rest arms 12, 14 abut on the outer periphery of the workpiece W being processed during the forward movement. This is supported against the grinding resistance. When the rest arms 12, 14 have reached the target position UPt and the correction target position LPt ', the tip of the upper rest arm 12 and the tip of the lower rest arm 14, when the workpiece W has been machined to the finishing diameter Dfin. The finished outer periphery of the work W is held so that the axis of the work W is positioned at the ideal rotation center.
[0026]
FIG. 7A shows a tracking error of the lower rest arm 14 with respect to a movement amount (displayed as a workpiece diameter) of the tip of the upper rest arm 12 when the same command value is given to the servo motors 23 and 24. FIG. 7B shows a tracking error of the tip of the lower rest arm 14 with respect to a movement amount of the tip of the upper rest arm 12 when the command value of the upper rest arm 12 is multiplied by a predetermined coefficient to obtain a command value of the lower rest arm 14. Is shown. As described above, when the target position LPt of the lower rest arm 14 is set to a value obtained by multiplying the target position UPt of the upper rest arm 12 by the electronic gear ratio, the tracking error of the lower rest arm 14 with respect to the upper rest arm 12 is large. Is reduced to However, a tracking error still remains between the two rest arms 12, 14 at the center of the range of use of the rest device.
[0027]
FIG. 7C shows that the target position LPt of the lower rest arm 14 decelerated by the electronic gear ratio is subjected to error correction according to the present invention as described above, and the corrected target position LPt ′ is transmitted to the servo motor 24 of the lower rest arm 14. This shows a tracking error of the tip of the lower rest arm 14 with respect to the tip position of the upper rest arm 12 when giving. As is clear from FIG. 7 (C), when error correction is performed according to the present invention, it is possible to eliminate the following error at the tips of both the rest arms 12, 14.
[0028]
As described above with reference to FIG. 6, the rest arms 12, 14 are advanced during the grinding process, and support the workpiece W at the advanced position until the workpiece W is processed to the finish diameter Dfin. In this forward position, the contact points of the tip shoes 12a, 14a of the two rest arms 12, 14 with the work W are equidistant from the ideal rotation axis of the work W, so that the final spark just before the grinding wheel head 13 retreats. At the time of out-grinding, the work W is in a state of rotating on the ideal rotation axis, and in this state, the grinding wheel head 13 is retracted. Then, the rotation of the work W is stopped slightly after the retreat of the grindstone table 13, and the two rest arms 12, 14 are retreated to the initial positions UPi, LPi set in steps 101 and 102 in FIG. The processing of the second workpiece W ends.
[0029]
In processing the second work W of the same lot, the above-described setting change operation is not performed. When the second work W is loaded and set on the grinding machine, the above-described grinding cycle is immediately started. You.
In the embodiment described above, the correction amounts α0 to α20 each time the lower rest arm 14 advances by a unit distance (for example, 1 mm) are registered in the correction value table TBL shown in FIG. The correction amount αn is sequentially read from the correction value table TBL and is cumulatively added. However, such a registration form of the correction amount in the correction value table TBL is based on a large number of correction values registered in the correction value table TBL. There is no influence on other correction values when one of the correction values is corrected, and the advantage of this point is that the number of correction values to be registered is determined when an interpolation correction value between two correction values is determined and fine correction is performed. This has an effect that can be reduced.
[0030]
However, the registration form of the correction amount in the correction value table TBL is not limited to this. For example, in a case where a control mode in which the rest arms 12, 14 are advanced from the most retracted reference position to the target position in each grinding cycle is employed, the correction amount registered at each read address of the correction value table TBL is: It is also possible to register as a total correction amount according to the movement amount from the reference position to the target position. In such a modified example, the correction feed amount setting program COMP of FIG. 4 reads out the total correction amount registered at the address corresponding to the work finishing diameter Dfin, and lowers the total correction amount by the electronic gear ratio. It is changed to be added to the target position LPt of the rest arm 14.
[0031]
When the correction amount registered in the correction value table TBL can be calculated by a functional expression relating to the moving position (or moving amount) of the rest arm 12 or 14, this functional expression is used instead of using the correction value table TBL. Is registered, it is also possible to directly calculate the correction amount from this functional expression.
In the above-described embodiment, the target position LPt of the lower rest arm 14 is calculated by multiplying the target position UPt of the upper rest arm 12 by the electronic gear ratio. It can also be specified directly as a parameter in the program.
[0032]
Further, in the above-described embodiment, the target position UPt of the lower rest arm 14 is calculated by multiplying the target position UPt of the upper arm 12 by the electronic gear ratio in the deceleration direction based on the upper rest arm 12. However, on the contrary, the electronic gear ratio coefficient (for example, 2.5) in a predetermined speed increasing direction is set at a target position LPt set in correspondence with the workpiece finishing diameter of the lower rest arm 14 with reference to the lower rest arm 14. May be calculated to calculate the target position UPt of the upper rest arm 12. In such a case, a tracking error of the tip of the upper rest arm 12 with respect to the movement of the tip of the lower rest arm 14 is registered in the correction value table TBL of FIG.
[0033]
Further, in the present embodiment, the target position UPt and the correction target position LPt ′ of the both rest arms 12 and 14 are set so as to coincide with the finishing diameter position of the work W. However, if necessary, these positions UPt are set. And LPt 'may be set at a position on the smaller diameter side by a predetermined amount (for example, several micrometers) from the work finish diameter position.
[0034]
【The invention's effect】
As described in detail above, according to the first aspect of the present invention, the lower rest arm is swiveled to follow the movement of the tip of the upper rest arm that moves linearly toward the cylindrical workpiece. In the NC control type work rest device, a target position for instructing a servo motor for driving one of the upper rest arm and the lower rest arm is set in accordance with the finishing diameter of the work, and a servo motor for driving the other of the two rest arms is set. The target position to be commanded is obtained by multiplying the target position of the one rest arm by a predetermined ratio, or determined according to the finished diameter of the work, and the target position is corrected by the correction amount according to the amount of movement of the other rest arm. Is added to the correction target position, so that the movement of the tip of the other rest arm can accurately follow the movement of the tip of the other rest arm. It can, thereby improving the machining accuracy of the workpiece.
[0035]
According to the invention of claim 2, in order to obtain the correction amount of the lower rest arm, which is the other rest arm, the correction amount for each exercise amount of the lower rest arm is stored in advance in a correction value table, and the correction value Since the correction amount corresponding to the amount of exercise of the lower rest arm is read from the table to correct the target position of the lower rest arm, it is possible to easily set and change the correction value.
[0036]
Further, according to the invention of claim 3, in order to obtain the correction amount of the lower rest arm, which is the other rest arm, each increment correction value corresponding to the increase in the unit exercise amount of the lower rest arm is previously stored in the correction value table. Since the lower rest arm is moved from the current position to the target position, each incremental correction amount in the movement range is read from the correction value table and cumulatively added to correct the target position of the lower rest arm. When one of a large number of correction values registered in the correction value table TBL is corrected, there is no effect on other correction values. The advantage of this point is that an interpolation correction value between two correction values is determined and fine correction is performed. And the effect of reducing the number of registered correction values.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram for explaining that a work support point at the tip of a lower rest arm changes according to a change in a work diameter.
FIG. 2 is a side view showing the NC control type work rest device according to the present invention, partially cut away, and a block diagram of a CNC device for controlling the work rest device.
FIG. 3 is a flowchart of a rest control program executed by the CNC device according to the present invention.
FIG. 4 is a flowchart of a correction feed amount setting program executed by the CNC device in step 113 of the rest control program.
FIG. 5 is an explanatory diagram showing an outline of a correction value table registered in a memory of the CNC device.
FIG. 6 is an operation cycle diagram showing feed positions of a grindstone and a work rest device in a grinding cycle.
7 (A) and 7 (B) are graphs showing a tracking error of a lower rest arm tip with respect to an upper rest arm tip position in a conventional NC control type work rest device, and FIG. 7 (C) is an NC control type work rest according to the present invention. 6 is a graph showing a tracking error of a lower rest arm tip with respect to an upper rest arm tip position in the device.
[Explanation of symbols]
W: Work 10: Rest device body 12: Upper rest arm 14: Lower rest arm 23, 24 Servo motor 25, 26 ... Feed screw mechanism 30 CNC device DUX, DUX, DUV Servo motor drive unit RCP Rest control program COMP Compensation feed amount setting program TBL Compensation value table

Claims (3)

An apparatus main body, an upper rest arm guided by the apparatus main body so as to be able to advance and retreat toward the work so as to support the outer periphery of the cylindrical work on the opposite side of the processing tool, and a tip directed from substantially below the work toward the work. A lower rest arm pivotally supported by the apparatus main body so as to move forward and backward, a feed mechanism including a first servo motor for moving the upper rest arm forward and backward, and a second servo motor for rotating the lower rest arm And a numerical control device for controlling the first and second servomotors, wherein the numerical control device is determined according to a finish diameter of the work. First command value setting means for setting a first command value for controlling a feed movement of one of the upper and lower rest arms; and multiplying the first command value by a predetermined coefficient. Second command value setting means for setting a second command value that is determined or determined in accordance with the finishing diameter of the work and controls the other feed motion of the upper and lower rest arms; and A correction feed amount setting means for setting a correction feed amount in accordance with a feed movement amount of the rest arm; an addition means for adding the correction feed amount to the second command value to obtain a correction second command value; One of the first and second servomotors corresponding to the one rest arm and the other of the first and second servomotors corresponding to the other rest arm based on one command value and the corrected second command value And a control means for controlling each of the work rest devices. The one and the other rest arms are the upper and lower rest arms, respectively, and the correction feed amount setting means includes a correction value table storing a correction value for each of the lower rest arm's momentums, and a momentum of the lower rest arm. Means for reading a correction value corresponding to the first and second servomotors based on the first command value and the second correction command value. The NC control type work rest device according to claim 1, wherein: The one and the other rest arms are the upper and lower rest arms, respectively, and the correction feed amount setting means includes a correction value in which each incremental correction feed amount is stored in advance in accordance with an increase in the unit movement amount of the lower rest arm. A table, and cumulative addition means for reading out and cumulatively adding each incremental correction feed amount within a movement range in which the lower rest arm moves from a current position to a target position to set the correction feed amount, and the control means The NC control type work rest device according to claim 1, wherein the first and second servomotors are respectively controlled based on the first command value and the corrected second command value.

Images