JP4374616B2 - Coolant supply method and apparatus for grinding machine - Google Patents

Description

  The present invention relates to a coolant supply method and apparatus for supplying coolant to a grinding point where a grinding wheel grinds a workpiece in a grinding machine.

Conventionally, when grinding a workpiece with a grinding wheel, coolant is supplied to the grinding point where the grinding wheel grinds the workpiece to cool and lubricate it, thereby preventing grinding burn and thermal distortion of the workpiece due to grinding heat. is doing. Patent Document 1 includes a grinding wheel head 14 having a grinding wheel 37, a spindle stock 11 that holds and rotates the workpiece 1, and an inverter motor that supplies coolant 6 stored in a coolant tank 7 to a coolant nozzle 43. In a grinding machine equipped with a pump 42 and a coolant nozzle 43 disposed in the grinding part, the amount of coolant 6 discharged by the pump 42 is determined by, for example, the outer diameter value of the workpiece 1, the rotational speed of the spindle 21, and the grinding wheel base 14 It is described that the workpiece 1 is changed according to the machining amount per unit time determined by the feed speed. According to this, the amount of coolant supplied to the grinding point is increased during rough grinding with a large amount of processing to prevent grinding burn, and the amount supplied is reduced during precise grinding with a small amount of processing, and the coolant is generated at the grinding point. It is possible to reduce the coolant dynamic pressure and improve the machining accuracy of the workpiece.
JP 2002-59335 A (3rd and 4th pages, FIGS. 1 and 4)

  In the above-described conventional grinding fluid supply method and apparatus in a grinding machine, the coolant amount is changed according to the machining amount, but the coolant amount is not changed based on the workpiece surface shape at the grinding point. . When the workpiece is a non-circular cam, the space formed by the grinding surface of the grinding wheel and the cam surface at the grinding point when the cam is ground by the grinding wheel while supplying a constant amount of coolant to the grinding point. Therefore, the coolant dynamic pressure generated in the coolant at the grinding point varies with each rotation phase during one rotation of the cam. When the coolant dynamic pressure fluctuates, the amount of relief that the workpiece escapes from the grinding wheel and the amount of deflection of the grinding wheel shaft on which the grinding wheel is mounted fluctuate, and the distance between the center of rotation of the cam and grinding wheel fluctuates. The shape accuracy of the cam is reduced. Even if the workpiece has a perfect circle shape, if the workpiece has holes or grooves, the coolant dynamic pressure fluctuates due to the holes or grooves, so that the shape accuracy of the workpiece decreases. If the coolant flow rate is reduced uniformly in order to suppress the shape error due to the fluctuation of the coolant dynamic pressure, the surface quality of the ground workpiece is deteriorated.

  The present invention has been made to solve the above-mentioned conventional problems, and by changing the coolant flow rate so that the coolant dynamic pressure generated in the coolant at the grinding point does not fluctuate during one rotation of the workpiece, The purpose of this is to grind with high shape accuracy.

  In order to solve the above-mentioned problem, the structural feature of the invention described in claim 1 is that a grinding wheel supported by a grinding wheel base and driven to rotate is supported by a workpiece support device and rotated. In the grinding machine that grinds and feeds the workpiece relatively to the grinding point and grinds the workpiece by the grinding wheel, the coolant dynamic pressure generated in the coolant at the grinding point is one of the workpieces. The coolant flow rate supplied to the grinding point is changed in synchronism with the rotation of the workpiece so that a constant pressure is obtained at any rotation phase during rotation.

  The structural feature of the invention according to claim 2 is the measurement according to claim 1, wherein the coolant dynamic pressure in each rotational phase of the workpiece is measured in a state where a constant flow rate of coolant is supplied to the grinding point. The coolant flow rate is changed in synchronism with the rotation of the workpiece so as to cancel the fluctuation associated with the change in the rotation phase of the coolant dynamic pressure.

  The structural feature of the invention according to claim 3 is that in claim 1, when a coolant having a constant flow rate is supplied to the grinding point, the coolant dynamic pressure in each rotational phase of the workpiece is determined in each rotational phase. Calculated based on the workpiece surface shape at the grinding point, and the coolant flow rate is changed in synchronism with the rotation of the workpiece so as to cancel the fluctuations accompanying the change in the rotation phase of the calculated coolant dynamic pressure. It is to let you.

  The structural features of the invention according to claim 4 are: a grinding wheel base that supports and rotates the grinding wheel, a workpiece support device that supports and rotates the workpiece, the grinding wheel base, and the workpiece support A bed on which an apparatus is mounted, a feed device for relatively grinding and feeding the grinding wheel base toward the workpiece support device, and a coolant to a grinding point at which the grinding wheel grinds the workpiece. In a grinding machine equipped with a coolant delivery device, the dynamic pressure generated in the coolant at the grinding point is supplied to the grinding point so as to be constant at any rotational phase during one rotation of the workpiece. And a control device for controlling the coolant delivery device so as to change the coolant flow rate in synchronization with the rotation of the workpiece.

  A structural feature of the invention according to claim 5 is that, in claim 4, the coolant delivery device includes a coolant nozzle that is attached to the grindstone table and supplies coolant from above toward the grinding point, and the coolant nozzle. It has flow control means provided in the vicinity of the outlet for controlling the coolant flow rate delivered from the coolant nozzle, and the control device controls the flow control means in synchronization with the rotation of the workpiece.

  In the invention according to claim 1 configured as described above, the coolant flow rate is set so that the coolant dynamic pressure generated in the coolant at the grinding point becomes a constant pressure at any rotation phase during one rotation of the workpiece. It is changed in synchronization with the rotation. Thereby, the fluctuation | variation of the distance between rotation centers by the fluctuation | variation of the coolant dynamic pressure of the cam and grinding wheel during one rotation of a workpiece can be suppressed, and the shape precision of the ground workpiece can be improved.

  In the invention which concerns on Claim 2, in the state which supplied the coolant of the fixed flow volume to the grinding point, the coolant dynamic pressure in each rotation phase of a workpiece is measured, and the change in the rotation phase of the measured coolant dynamic pressure is measured. Because the coolant flow is changed in synchronization with the rotation of the workpiece so as to cancel the fluctuations involved, fluctuations in the distance between the rotation center of the cam and the grinding wheel during one rotation of the workpiece can be accurately suppressed. The shape accuracy of the workpiece can be improved.

  In the invention according to claim 3 configured as described above, when a constant flow rate of coolant is supplied to the grinding point, the coolant dynamic pressure at the grinding point in each rotational phase of the workpiece is based on the surface shape of the workpiece. Since the coolant flow rate is changed in synchronism with the rotation of the workpiece so as to cancel out the fluctuation accompanying the change in the rotation phase of the calculated coolant dynamic pressure, the cam and the grinding wheel during one rotation of the workpiece are calculated. Variation of the distance between the rotation centers can be suppressed by a simple method, and the shape accuracy of the ground workpiece can be improved.

  In the invention according to claim 4 configured as described above, the coolant supply device is configured so that the coolant dynamic pressure generated in the coolant at the grinding point becomes a constant pressure in any rotation phase during one rotation of the workpiece. The flow rate is changed in synchronization with the rotation of the workpiece. Thereby, the fluctuation | variation of the distance between the rotation centers of the cam and grinding wheel during one rotation of a workpiece can be suppressed, and the coolant supply apparatus which can grind a workpiece with high shape accuracy can be provided.

  In the invention according to claim 5 configured as described above, the flow rate control means for controlling the coolant flow rate is provided in the vicinity of the outlet of the coolant nozzle that supplies the coolant from above toward the grinding point. It can be accurately controlled in synchronization with the rotational phase of the workpiece.

   Embodiments of a coolant supply method and apparatus in a grinding machine according to the present invention will be described below with reference to the drawings. In FIG. 1, a table 13 is slidably mounted on a bed 12 of a numerical control cam grinding machine 11 and is moved in the Z-axis direction by a servo motor 15 via a ball screw 14. A headstock 16 is fixed on the table 13. A spindle 18 for gripping one end of the workpiece W by a chuck 17 is rotatably supported on the spindle stock 16, and is rotated by a servo motor 19 to rotate the workpiece W to Z. Rotate around the C axis parallel to the axis. A tailstock 20 is fixed on the table 13 so as to face the headstock 16 so that the position of the tailstock 20 can be adjusted. The tailstock 20 is fitted to the tip of a ram 21 slidably fitted on the spindle 18 on the same axis. The fitted center 22 is fitted into a center hole formed in the other end of the workpiece W to support the other end of the workpiece W. The table 13, the headstock 16, the servo motor 19, and the like constitute a workpiece support device 23 that supports the workpiece W so as to be rotatable around the C axis in a horizontal XZ plane.

   A grindstone table 24 is mounted on the bed 12 so as to be slidable in the X-axis direction orthogonal to the Z-axis, and is moved in the Z-axis direction by a servo motor 26 via a ball screw 25. A grindstone table 27 is attached to the grindstone table 24, and a grindstone shaft 28 is supported on the grindstone table 27 in parallel with the Z axis in the XZ plane, and is rotated by a built-in motor 29. A grinding wheel G in which an abrasive grain layer in which CBN abrasive grains are bonded by vitrified bonding is attached to the outer peripheral surface of the core is mounted on the grinding wheel shaft 28.

  A coolant delivery device 30 that supplies coolant to a grinding point P at which the grinding wheel G grinds the workpiece W is composed of a coolant nozzle 31, a pump 32, a motor 33, a flow control valve 34, a coolant storage tank 35, and the like. The coolant discharged from the pump 32 driven by 33 is controlled in flow rate by a flow rate control valve 34 which is a flow rate control means, and is supplied to the grinding point from the coolant nozzle 31 attached to the grinding wheel guard 36 above the grinding wheel G. Cool and lubricate the machined part. The coolant supplied to the grinding point flows below the bed 11, and after the chips are separated by a magnet separator (not shown), the coolant is returned to the coolant storage tank 35 again.

  The flow rate control valve 34 has a variable throttle valve 37 connected between the pump 32 and the coolant nozzle 31 in the vicinity of the coolant nozzle 31, and a spool valve 39 in which the pressure before and after the variable throttle valve 37 is urged by a compression spring 38. Acts on both end faces. Since the spool valve 39 moves and opens and closes the bypass port 40 so that the force acting on the spool valve 39 is balanced with the spring force of the compression spring 38 based on the pressure difference before and after the variable throttle valve 37, excess coolant is bypassed. It returns to the coolant storage tank 35 through the path 41. Since the pressure difference before and after the variable throttle valve 37 is maintained at a substantially constant pressure P by the spring force of the compression spring 38, the coolant amount Q supplied from the coolant nozzle 31 to the grinding point through the variable throttle valve 37 is constant pressure. It is proportional to the value obtained by dividing P by the throttle resistance R of the variable throttle valve 37. The variable throttle valve 37 is moved by the servo motor 42 to change the opening of the valve hole, and thus the throttle resistance R, and the flow control valve 34 is adjusted by the servo motor 42 to adjust the opening of the variable throttle valve 37. By controlling, the coolant flow rate Q can be controlled.

   The numerical controller 43 rotates the servo motors 19 and 26 by simultaneously controlling the two axes so that the grindstone table 24 moves forward and backward in the X direction according to the rotational phase of the spindle 18 around the C axis in the XZ plane. Cam profile creation NC data for moving the workpiece profile and performing the cam profile creation motion between the workpiece W and the grinding wheel G is stored. Furthermore, the numerical control device 43 feeds the grinding wheel table 24 in the X-axis direction toward the workpiece support device 23 in a superposed manner with the cam profile creation movement, and supplies the coolant to the grinding point A while grinding the grinding wheel. A plunge grinding feed program for grinding the cam C on the workpiece W by G is stored.

   When grinding the non-circular cam C by the grinding wheel G while supplying the coolant 44 to the grinding point A as shown in FIG. 2, the curvature radius E of the cam surface Cs at the grinding point A as shown in FIG. Varies with the rotational phase θ of the cam, and the coolant dynamic pressure P generated in the coolant at the grinding point A varies with the rotational phase θ during one rotation of the cam C due to the change in the curvature radius E. The fluctuation of the coolant dynamic pressure P caused by the change in the rotational phase θ of the cam C can be obtained by measurement. That is, a force detection sensor is embedded in the center 22 of the tailstock 20, and the grinding wheel G is brought very close to the cam C ground into a finished shape, and a cam profile creation motion is performed between the workpiece W and the grinding wheel G. In this state, the coolant dynamic pressure P at each rotational phase θ of the cam C can be measured as the output of the force sensor by supplying a coolant having a constant flow rate Qc to the grinding point A. The coolant dynamic pressure Pv at each rotational phase θ of the cam C measured in this way is as shown in FIG. The coolant dynamic pressure Pv at each rotational phase θ can be measured by measuring the power of the built-in motor 29 that rotationally drives the grindstone shaft 28 instead of the force sensor embedded in the center 22.

   The coolant dynamic pressure P increases and decreases as the coolant flow rate Q supplied to the grinding point A, the curvature radius of the grinding wheel G, and the curvature radius E of the cam surface Cs at the grinding point A and the cam width increase and decrease. It can be obtained by calculation by setting a coefficient. In a state where the coolant flow rate is constant Qc, the coolant dynamic pressure P at each rotational phase θ of the cam C is set to the curvature radius E and the cam width of the cam surface Cs at the grinding point A and the curvature of the grinding wheel G at each rotational phase θ. When calculated based on the radius, the horizontal axis represents the rotational phase θ, and the vertical axis represents the coolant dynamic pressure P, the result is almost the same as Pv in FIG.

  In this way, when the coolant dynamic pressure P varies, the amount of escape of the workpiece W from the grinding wheel G, the amount of deflection of the grinding wheel shaft 28 to which the grinding wheel G is mounted, etc. vary, and the cam C and the grinding wheel G The distance between the rotation centers varies, and the shape accuracy of the ground cam C is lowered. Therefore, if the coolant dynamic pressure P is not changed in accordance with the change in the rotational phase θ of the cam C, the cam C with good shape accuracy can be ground. Therefore, as shown in FIG. 5, when the coolant 33 having a constant flow rate Qc is supplied to the grinding point A, the grinding is performed so as to cancel the fluctuation Pv of the coolant dynamic pressure P caused by the change of the rotational phase θ of the cam C. When the coolant flow rate Q supplied to the point A is changed like Qv in synchronization with the rotation of the workpiece W, the coolant dynamic pressure P is approximately proportional to the coolant flow rate Q, so the coolant dynamic pressure P generated at the grinding point A is Becomes a substantially constant pressure Pc.

  An example of obtaining the coolant flow rate Qv that changes with the change in the rotational phase θ of the cam C will be described with reference to FIG. The coolant dynamic pressure Pv generated along with the change in the rotational phase θ of the cam C is measured when the coolant 33 having a minimum constant flow rate Qc that does not cause grinding burn or thermal distortion is supplied to the grinding point A. By reversing the coolant dynamic pressure Pv up and down, a coolant flow rate Qv that changes with a change in the rotational phase is obtained, and the coolant flow rate Qv is increased so that the minimum value of the coolant flow rate Qv matches the minimum constant flow rate Qc. Translate to. When the coolant flow rate Qv thus obtained is supplied to the grinding point A in synchronization with the rotation of the cam C, the coolant dynamic pressure P is equal to the coolant dynamic pressure Pv generated when the coolant with the minimum constant flow rate Qc is supplied. A substantially constant pressure Pc equal to the maximum value is obtained.

  In the numerical control device 43, the coolant flow rate Qv that changes at each rotational phase is stored for each cam type so that the coolant dynamic pressure P generated at the grinding point A becomes substantially constant. This coolant flow rate Qv is a flow rate suitable for each type of cam, but it is possible to increase or decrease the overall coolant flow rate by maintaining the coolant dynamic pressure P at a substantially constant pressure Pc by applying an override as necessary. it can. In the numerical controller 43, the servo motor 42 is rotated in association with the servo motor 19 so as to be superimposed on the cam profile generating motion, and the throttle resistance R of the variable throttle valve 37 of the flow control valve 34 is set to the rotational phase θ of the main shaft 18. By controlling synchronously, the coolant supplied to the grinding point A so that the coolant dynamic pressure P generated in the coolant 33 at the grinding point A becomes a constant pressure at any rotational phase during one rotation of the workpiece W. A coolant supply program for changing the flow rate Q in synchronization with the rotational phase θ of the workpiece W is stored.

   Next, the operation of the above embodiment will be described. When the workpiece W is gripped by phasing the chuck 17 of the spindle 18 in the rotational direction, the rear end is sandwiched by the center 22 of the tailstock 20 and the start button is pressed, the numerical controller 43 executes the grinding program. To do. The servo motor 15 is rotationally driven by a command from the numerical controller 43, the table 13 is moved in the Z-axis direction via the ball screw 14, and the grinding wheel G is indexed to the grinding start position facing the cam portion of the workpiece W. It is.

   Next, the servomotors 19 and 26 are simultaneously controlled by the cam profile creation NC data to be rotated by two axes, and the grindstone table 24 is rotated in the X direction according to the rotational phase of the spindle 18 around the C axis in the XZ plane. The cam profile creation movement is performed between the workpiece W and the grinding wheel G. At the same time, the servo motor 26 is rotated in conjunction with the rotation of the main shaft 18, and the grindstone table 24 is advanced toward the workpiece support device 23 in the X direction at the rough grinding feed rate to the rough grinding completion position, thereby creating a profile. The grinding wheel G is superposed on the movement and is plunge coarsely fed in the X-axis direction toward the cam portion of the workpiece W. During the coarse grinding feed, the variable throttle valve 37 of the flow control valve 34 is maintained open by the servo motor 42 according to a command from the numerical controller 43, and a large amount of coolant is supplied to the grinding point A.

  When the grindstone table 24 is advanced to the rough grinding completion position at the rough grinding feed speed and the plunge rough grinding is completed, the grinding wheel G is superimposed on the profile generating motion and moved toward the workpiece W with the fine grinding feed speed. Until the plunge is finely ground in the X-axis direction. The grinding wheel base table 24 is temporarily stopped at the precise grinding completion position, and the cam C is sparked out by the grinding wheel G.

   During the fine plunge grinding and spark-out grinding, the numerical controller 43 executes a coolant supply program and rotates the servo motor 42 in association with the servo motor 19. As a result, the opening degree of the variable throttle valve 37 of the flow control valve 34 is changed by the servo motor 42, the throttle resistance R of the variable throttle valve 37 is controlled in synchronization with the rotation of the main shaft 18, and is generated in the coolant at the grinding point A. The coolant flow rate Q supplied to the grinding point A is changed in synchronism with the rotational phase θ of the workpiece W so that the coolant dynamic pressure P becomes constant at any rotational phase during one rotation of the workpiece W. .

  When the spark-out grinding is completed, the grinding wheel G is retracted in the X-axis direction from the workpiece W to the retracted end while being superimposed on the profile creation motion, and the grinding wheel G is separated from the cam C.

  In the above embodiment, the coolant delivery device 30 is constituted by the coolant nozzle 31, the pump 32, the motor 33, the flow rate control valve 34, the coolant storage tank 35, etc., but the coolant delivery device is a coolant nozzle, pump, inverter motor, It is composed of a coolant storage tank, etc., and the pump flow rate is changed in synchronism with the rotation of the workpiece by the inverter motor, so that the coolant flow rate supplied to the grinding point is changed in synchronism with the rotation of the workpiece. Also good.

  In the above embodiment, the case where the cam is ground has been described. However, when a non-circular workpiece other than the cam is ground, and when a workpiece having a hole or a groove on the cylindrical surface is ground, the workpiece is similarly treated. The coolant flow rate Qv that changes with the change in the rotation phase of the workpiece is obtained, and this coolant flow rate Qv is supplied to the grinding point in synchronism with the rotation of the workpiece. Even in the phase, the pressure can be made substantially constant.

The top view of the cam grinding machine provided with the coolant supply apparatus which concerns on this Embodiment. The side view which shows the relationship between a grinding wheel, a cam, and a coolant nozzle. The figure which shows the state from which the curvature radius of the cam surface in a grinding point changes with the rotational phase of a cam. The figure which shows the coolant dynamic pressure which arises in a grinding | polishing point in each rotation phase of a workpiece | work when coolant flow rate is constant. The figure which shows the coolant flow rate in each rotation phase which cancels the coolant dynamic pressure which arises in a grinding point in each rotation phase of a cam when coolant flow rate is constant.

Explanation of symbols

   DESCRIPTION OF SYMBOLS 11 ... Cam grinder, 12 ... Bed, 15, 19, 26, 42 ... Servo motor, 18 ... Main shaft, 23 ... Workpiece support device, 29 ... Grinding wheel base, 30 ... Coolant supply device, 31 ... Coolant nozzle, 32 ... Pump, 33... Motor, 34... Flow control valve, 45. G: Grinding wheel, W ... Workpiece, C ... Cam.

Claims (5)

A grinding wheel supported by a grinding wheel platform and rotated and driven is relatively ground toward a workpiece supported and rotated by a workpiece support device, and the grinding wheel supplies the coolant to the grinding point while supplying the coolant. In a grinding machine for grinding a workpiece, the coolant dynamic pressure generated in the coolant at the grinding point is supplied to the grinding point so as to be constant at any rotational phase during one rotation of the workpiece. A coolant supply method in a grinding machine, wherein the coolant flow rate is changed in synchronization with the rotation of the workpiece. 2. The coolant dynamic pressure in each rotational phase of the workpiece is measured in a state in which a constant flow rate of coolant is supplied to the grinding point, and a change in the rotational phase of the measured coolant dynamic pressure is accompanied. A coolant supply method in a grinding machine, wherein the coolant flow rate is changed in synchronization with the rotation of the workpiece so as to cancel the fluctuation. 2. The coolant dynamic pressure at each rotational phase of the workpiece is calculated based on the workpiece surface shape at the grinding point at each rotational phase when a constant flow rate of coolant is supplied to the grinding point. A coolant supply method for a grinding machine, wherein the coolant flow rate is changed in synchronism with the rotation of the workpiece so as to cancel the fluctuations associated with the change in the rotation phase of the calculated coolant dynamic pressure. A grinding wheel base that supports and rotates the grinding wheel, a workpiece support device that supports and rotates the workpiece, a bed on which the grinding wheel table and the workpiece support device are placed, and the grinding wheel table In a grinding machine comprising: a feed device that relatively feeds the workpiece toward the workpiece support device; and a coolant delivery device that delivers coolant to a grinding point where the grinding wheel grinds the workpiece. The coolant flow rate supplied to the grinding point is changed in synchronism with the rotation of the workpiece so that the dynamic pressure generated in the coolant at a point becomes a constant pressure at any rotation phase during one rotation of the workpiece. A coolant supply device in a grinding machine, comprising: a control device that controls the coolant delivery device to cause the coolant to flow. 5. The coolant delivery device according to claim 4, wherein the coolant delivery device is a coolant nozzle that is attached to the grindstone table and that supplies coolant from above toward the grinding point, and a coolant flow rate that is provided near the coolant nozzle and delivered from the coolant nozzle. A coolant supply device in a grinding machine, characterized in that said control device controls the flow rate control means in synchronization with the rotation of the workpiece.

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