JP2016083745A - Method of correcting process tolerance of gear grinder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To correct a pressure angle of a workpiece by using a simple method without correcting a shape of a dresser.SOLUTION: An error of a pressure angle of a workpiece tooth surface is detected, and a pressure angle amount to be corrected, when an angle between a vertical axis of a work table and a grindstone central axis viewed from an X direction is shifted from the time of ordinary grinding, is predicted, and then a correction angle is calculated in accordance with the detected error of the pressure angle, and a screw-like grindstone is rotated in a direction A only by the calculated correction angle, and a workpiece is ground by using the screw-like grindstone in this corrected posture.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a processing accuracy correction method for a gear grinding machine having a threaded grindstone and a dresser, and more particularly to a method for correcting a pressure angle of a workpiece.

  2. Description of the Related Art Conventionally, a gear grinding machine that grinds tooth surfaces (spur gears, helical gears, etc.) of a workpiece using a screw-shaped grindstone having a helical thread on the outer peripheral surface is known (for example, Patent Document 1). reference). Such a gear grinding machine grinds a gear into a desired shape by NC controlling the positions and rotation speeds of the X-axis, Y-axis, and Z-axis of the thread-like grindstone and the rotation speed of the work table. Moreover, it has a dressing device, and after grinding a predetermined amount of gears, the threaded grindstone can be regenerated.

  In this type of gear grinding machine, if the processed gear does not have the original target shape, some correction work is required. Although the dresser shape of the dressing apparatus can be modified, in that case, a great amount of cost and man-hours are required.

Japanese Patent No. 4824947

  However, correcting the grinding wheel pressure angle by dressing as in the prior art has problems in terms of cost and man-hours.

  The present invention has been made in view of the above points, and an object of the present invention is to make it possible to correct the pressure angle of the workpiece by a simple method without correcting the shape of the dresser.

  In order to achieve the above object, in the present invention, the correction angle of the pressure angle is predicted by simulation, and the feed angle of the threaded grindstone is appropriately corrected.

Specifically, in the first invention,
A work table that supports the work so as to be rotatable about a vertical axis;
It can move in the X direction that is the horizontal direction, the Z direction that is the vertical direction, the Y direction that is orthogonal to the X direction and the Z direction with respect to the work table, and can be swung in the A direction on the YZ plane. A threaded grindstone that can rotate in the B direction around
It is premised on a method of correcting the processing accuracy of a gear grinder provided with a disk-shaped dresser that performs dressing of the thread of the thread-shaped grindstone by rotating around a dresser rotating shaft.

And the above method
A specification input process for inputting the specifications of the gear and dresser,
A theoretical tooth profile calculation step for calculating a theoretical tooth profile based on the specifications of the gear,
A dresser shape calculation step for determining the shape of the dresser by mathematical expression based on the specifications of the dresser;
A grinding wheel molding condition calculation step for calculating a grinding wheel molding condition based on the theoretical tooth shape and the dresser shape,
A grinding wheel shape calculation step for calculating a grinding wheel shape by formulating based on the grinding wheel molding conditions,
A gear creation condition calculation step for calculating a gear creation condition based on the shape of the grinding wheel;
Tooth profile calculation step for calculating the tooth profile based on the creation conditions of the gear,
An error detection step of calculating an error between the calculated value of the pressure angle of the tooth profile and the theoretical value of the pressure angle of the theoretical tooth profile;
A correction angle setting step for setting a correction angle for shifting the angle between the vertical axis of the work table and the grindstone center axis viewed from the X direction from a value before correction from the error of the pressure angle;
And a tooth profile shape recalculation step for recalculating the creation conditions of the gear so as to rotate the screw-shaped grindstone in the A direction in accordance with the correction angle.

  That is, in the simulation, the operation of the threaded grinding wheel cannot be directly calculated from the target machining surface shape. However, according to the above configuration, the gear shape to be ground from the virtual threaded grinding wheel can be predicted. It can be confirmed whether the error of the pressure angle is reduced in the shape. The workpiece grinding posture required to eliminate the error in the detected pressure angle of the gear can be predicted by simulation, and grinding can be performed based on the prediction result. There is no need to change the shape. For this reason, it is not necessary to confirm by actually grinding.

  As described above, according to the present invention, the pressure angle of the workpiece tooth surface that is corrected when the angle between the vertical axis of the work table viewed from the X direction and the central axis of the grindstone is shifted from the value before correction. By calculating the correction angle by predicting the amount of rotation and rotating the screw-shaped grindstone in the A direction by the correction angle to grind the workpiece with the screw-shaped grindstone, it is easy without correcting the dresser shape The pressure angle of the workpiece can be corrected in a simple manner.

It is a flowchart which shows the processing accuracy correction method of a gear grinding machine. It is a perspective view which shows the outline | summary of a gear grinding machine. It is a perspective view which shows the positional relationship of a work table and a screw-shaped grindstone. It is a perspective view which shows the positional relationship of a dresser and a screw-shaped grindstone. It is a schematic diagram for demonstrating the conditional expression of a contact. It is a graph which shows the A-axis change amount and pressure angle error which show a simulation result.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  2 to 4 show a tooth surface grinder 1 according to an embodiment of the present invention. The tooth surface grinder 1 is a machine for grinding a workpiece 20 such as a helical gear or a spur gear. Yes, it has a trapezoidal bed 2. An X slider 3 that can move in the radial direction of the gear (X direction) is placed on the bed 2. A column 4 is placed on the X slider 3, and an axial slider 5 that is movable in the axial direction (Z direction) of the gear is attached to the column 4. A Y slider 8 that is movable in the (Y direction) is attached. The Y slider 8 is provided with a swivel slider 6 that can swivel in the A direction (both forward and reverse torsional angles). It is attached so that it can rotate in both forward and reverse directions. The threaded grindstone 7 is formed with, for example, three threads 7b having a twist angle γ on the outer periphery of a ring-shaped main body, and a total of three grooves 7c between the threads 7b.

  A counter column 9 is provided at a position facing the column 4 on the bed 2. The counter column 9 has a tailstock 10 for pressing the workpiece 20 from the vertical direction (W direction), and a work table 11 for holding the workpiece 20 is provided below the tailstock 10. The work table 11 is turnable in the C direction (both forward and reverse directions) about the table vertical axis 11a.

  The counter column 9 is provided with a dresser 12 for dressing the threaded grindstone 7. The dresser 12 has a disk-shaped dressing tool 12b that rotates about a dresser rotating shaft 12a. When the sharpness of the threaded grindstone 7 is lowered, the dresser 12 is brought into contact with the flank of the thread 7b to be regenerated. is there. In the present embodiment, there is one dressing tool 12b, but a pair of dressing tools 12b may be used.

  The position and rotation of the threaded grindstone 7 and the rotation of the workpiece 20 are precisely controlled by NC control.

  With such a tooth surface grinding machine 1, the gear as the workpiece 20 was ground by NC controlling the positions and rotation speeds of the X-axis, Y-axis, and Z-axis of the screw-like grindstone 7 and the rotation speed of the work table 11. In some cases, the shape of the gear after processing may not be as designed. In such a case, some correction work is required.

  A plurality of types of gear shape errors are conceivable, and one of them may be a shape error in the tooth profile pressure angle. Conventionally, the dresser 12 is used to dress the threaded grindstone 7 and the grindstone pressure angle is corrected.

  However, in the present embodiment, instead of correcting the dresser 12, when the posture of the screw-like grindstone 7 is changed, how the gear shape changes is predicted using simulation, and then the posture is actually changed. Grinding is done.

  The operation of the method for correcting the machining accuracy of the gear grinding machine 1 according to this embodiment will be specifically described.

  As shown in FIG. 1, first, in step S10, the specifications of the gear and the specifications of the dresser are input.

  Next, in step S11, the pressure angle correction amount is set to zero.

  Next, in the specification input step of step S12, the theoretical gear shape is calculated based on the specifications of the gear.

  Next, in the dresser shape calculation step in step S13, the dresser shape is formulated based on the dresser specifications.

  Next, in the grinding wheel molding condition calculation step in step S14, the grinding wheel molding conditions are calculated. Specifically, the direction of the grindstone lead, the grindstone and the dresser is calculated.

  Next, in the grindstone shape calculating step in step S15, the grindstone shape is obtained by formulating based on the grindstone molding conditions and the like. For example, a three-dimensional approximate shape of the threaded grindstone 7 is created. The three-dimensional approximate shape is obtained by calculating a tooth perpendicular section of the approximate involute screw.

  Next, in the gear creation condition calculation step in step S16, the gear creation conditions are calculated based on the grindstone shape and the like. Specifically, the direction of the grindstone and the gear and the rotation ratio are calculated.

Next, in the tooth profile calculation step in step S17, the tooth profile is calculated based on the gear creation conditions. A tooth surface contact point is calculated from a contact conditional expression when the created thread-like grindstone 7 is rotated under predetermined grinding conditions (X-axis, Y-axis, Z-axis positions and rotational speeds, etc.). Specifically, as shown in FIG. 5, the tooth surface S ₁ of the threaded grindstone 7 and the tooth surface S _{2 of the} gear are in contact at a point P, and the speed at the point P of both tooth surfaces S ₁ and S _2. was a _V 1, _{V 2,} Ryohamen _S 1, if the unit vector in the common normal direction _{S 2} was _n, V 1, a n direction component of _{V 2} n × _{V 1} over n × _{V 2} Must be equal (n × V ₁ −n × V ₂ = 0). Using this fact, the tooth surface contact point in a predetermined region is calculated. Then, the tooth surface contact point is converted into gear coordinates by using a simultaneous transcendental equation from the vector diagram of the screw-like grindstone 7 to calculate a corrected three-dimensional approximate gear shape.

  Next, a pressure angle error calculation is performed in the error detection step of step S18. Specifically, the difference between the calculated value and the theoretical value is calculated.

  Next, in step S19, a pressure angle error is determined. Specifically, it is determined whether the pressure angle error is equal to or less than the tooth profile correction amount. When the pressure angle error is larger than the tooth profile correction amount, the process proceeds to step S20, and a correction angle setting step is performed. Here, the correction angle that can minimize the error of the pressure angle is determined. Predicting the amount of gear pressure angle to be corrected when the angle between the table vertical axis 11a of the work table 11 and the grindstone center axis 7a as viewed from the X direction is shifted from the grinding angle before correction; The correction angle is set in accordance with the error in the pressure angle of the gear detected in S19.

  In order to reflect this correction angle, the process returns to step S13 to recalculate the dresser shape. Here, there is no change in the dresser shape itself.

  Next, in step S14, a grinding wheel forming condition reflecting the correction angle is calculated.

  Next, steps S15 to S18 are performed. In particular, in step S16, the gear creation conditions are calculated again so that the threaded grindstone is rotated in the direction A in accordance with the correction angle (tooth profile recalculation step).

  In step S19, the pressure angle error is determined again. If the pressure angle error is equal to or less than the tooth profile correction amount, the process proceeds to step S21, where NC data is created. If the pressure angle error is still larger than the tooth profile correction amount, step S20 and subsequent steps are repeated.

  In step S22, the NC control unit starts control using the created NC data. Specifically, the post-correction grinding conditions are input based on the calculated correction amount, and the posture of the threaded grindstone 7 of the tooth surface grinding machine 1 is changed. Specifically, the threaded grindstone 7 is rotated in the A direction from the grinding posture before correction by the calculated angle.

  Subsequently, grinding is performed by the tooth surface grinding machine 1 in step S23.

  Next, in step S24, the pressure angle error determination is performed again. If the pressure angle error is larger than the tooth profile correction amount, the process proceeds to step S25, and an appropriate tooth profile correction amount is manually input, and the process returns to step S13. For example, the correction amount of the pressure angle is manually input. When the pressure angle error is equal to or less than the tooth profile correction amount, the processing by the tooth surface grinder 1 is finished.

  Next, FIG. 6 shows the result of actual simulation.

  For example, as specifications of the simulation, the gear module is 2, the fraction is 56, the pressure angle is 14.5 °, and the torsion angle is 35 °. The shape of the grindstone is 298 mm in diameter and 5 strips.

  Using these specifications, the method of the above embodiment was actually performed by simulation. As shown in FIG. 6, when the A-axis change amount is -0.4 to 0.4 deg, the pressure angle error can be adjusted. I know that there is.

  As described above, in the present embodiment, the grinding posture of the workpiece 20 necessary for eliminating the detected error in the pressure angle of the gear is predicted by simulation, and grinding is performed based on the prediction result, so the shape of the dresser 12 is changed. Or changing the shape of the threaded grindstone 7 by dressing. Further, by improving the prediction accuracy in the simulation, the correction work becomes accurate and simple.

  Further, in the normal simulation, it is not possible to directly calculate the operation of the threaded grindstone 7 from the target machining surface shape, but in the present embodiment, the gear shape ground from the virtual threaded grindstone 7 can be predicted, It can be confirmed whether the error of the pressure angle is reduced in the predicted shape. For this reason, it is not necessary to confirm by actually grinding.

  Therefore, according to the gear grinding machine processing accuracy correction method according to the present embodiment, the pressure angle of the workpiece 20 can be corrected by a simple method without correcting the shape of the dresser 12.

  In addition, the above embodiment is an essentially preferable illustration, Comprising: It does not intend restrict | limiting the range of this invention, its application thing, or a use.

  As described above, the present invention is useful for a processing accuracy correction method for a gear grinder that grinds spur gears, helical gears, and the like using a screw-shaped grindstone.

1 Tooth surface grinding machine
2 beds
3 X slider
4 columns
5-axis slider
6 Y slider
7 Threaded grinding wheel
7a Wheel center axis
7b thread
7c groove
8 Rotating slider
9 Counter column
10 Tailstock
11 Worktable
11a Table vertical axis
12 Dresser
12a Dresser rotary shaft
12b Dressing tool
20 work pieces

Claims (1)

A work table that supports the work so as to be rotatable about a vertical axis;
It can move in the X direction that is the horizontal direction, the Z direction that is the vertical direction, the Y direction that is orthogonal to the X direction and the Z direction with respect to the work table, and can be swung in the A direction on the YZ plane. A threaded grindstone that can rotate in the B direction around
In a method of correcting the processing accuracy of a gear grinder provided with a disk-shaped dresser that rotates around a dresser rotation axis and performs dressing of the thread of the thread-shaped grindstone using simulation,
A specification input process for inputting the specifications of the gear and dresser,
A theoretical tooth profile calculation step for calculating a theoretical tooth profile based on the specifications of the gear,
A dresser shape calculation step for determining the shape of the dresser by mathematical expression based on the specifications of the dresser;
A grinding wheel molding condition calculation step for calculating a grinding wheel molding condition based on the theoretical tooth shape and the dresser shape,
A grinding wheel shape calculation step for calculating a grinding wheel shape by formulating based on the grinding wheel molding conditions,
A gear creation condition calculation step for calculating a gear creation condition based on the shape of the grinding wheel;
Tooth profile calculation step for calculating the tooth profile based on the creation conditions of the gear,
An error detection step of calculating an error between the calculated value of the pressure angle of the tooth profile and the theoretical value of the pressure angle of the theoretical tooth profile;
A correction angle setting step for setting a correction angle for shifting the angle between the vertical axis of the work table and the grindstone center axis viewed from the X direction from a value before correction from the error of the pressure angle;
A gear grinding machine machining accuracy correction method comprising: a tooth profile shape recalculation step that recalculates a gear generation condition so that the screw-shaped grindstone is rotated in the A direction in accordance with the correction angle.