JP5425570B2 - Processing method and apparatus for trunnion of tripod type constant velocity joint - Google Patents

Description

  The present invention relates to a method for processing an outer peripheral surface of a work having an elliptical cross section or other non-circular shape by grinding.

  Patent Document 1 describes an apparatus that performs non-circular machining by synchronously rotating a swing shaft having a cam and a workpiece spindle.

JP 58-181558 A

  When machining an elliptic cylinder using a machine tool equipped with NC on the workpiece spindle and grinding wheel cutting table, the grinding wheel cutting table can be controlled synchronously according to the rotation phase of the workpiece spindle. The oscillating shaft and the cam mechanism device are not required. However, in order to perform the cutting operation while swinging the grindstone cutting table at high speed, the grindstone cutting table is required to have excellent response to commands. In order to obtain an elliptical shape with high accuracy and stability, it is necessary to machine the grinding wheel cutting table at a low speed (lowering the spindle speed), the machining efficiency is deteriorated, and the machining cycle time is increased.

  An object of the present invention is to stabilize machining accuracy and improve machining efficiency in non-round grinding.

This invention uses an NC machine tool to control the relative position of the workpiece and the grindstone in accordance with the rotational phase of the workpiece spindle when grinding the outer peripheral surface of a workpiece whose cross section perpendicular to the rotational axis is non-circular. However, the problem is solved by creep feed grinding. Here, creep feed grinding refers to an operation in which a predetermined contour is formed on a grindstone, a workpiece is sent at a low speed, and finish grinding is performed with a single cut (JISB0106).
That is, the present invention is a processing method for grinding an outer peripheral surface of the leg shaft in a trunnion including a boss formed with a serration hole in an axial center portion and a plurality of leg shafts arranged at equal intervals in the circumferential direction of the boss. The outer peripheral surface has a non-circular outline in a cross section perpendicular to the rotation axis of the leg shaft, and an unprocessed portion facing the axial direction of the boss and an elliptical shape facing the circumferential direction of the boss. NC machine tool comprising a workpiece spindle having a chucking device for holding a workpiece and a rotary drive device, and a grindstone spindle that holds the grindstone and is fixed to a grindstone cutting table that can be reciprocated by the drive device. The chucking device grasps the inner diameter of the serration hole and fixes it with a clamper, and positions the leg shaft to be machined so as to be coaxial with the workpiece spindle. Characterized by creep feed grinding while controlling the relative position of the workpiece and the grinding wheel in accordance with the.

This invention is applied to the processing of leg shafts in a trunnion of a tripod constant velocity joint . In the conventional tripod type constant velocity joint that adopts an ellipse (major axis + minor axis) in the cross-sectional shape of the trunnion leg shaft, the ratio of major axis to minor axis was 1.01, but the newly developed tripod type The constant-velocity joint is a super-elliptical type with a major axis / minor axis ratio of about 1.17, so the swing stroke during elliptical grinding is longer, and the conventional tripod type constant velocity joint grinder cannot process it. It was. For this reason, paying attention to the fact that the grindstone cutting base of the NC cylindrical grinder is NC, in addition, the leg of the tripod type constant velocity joint is determined based on the judgment that elliptical machining is possible if the spindle is made NC. Development of a shaft machining method was started. In the case of ordinary plunge cut grinding, the creep feed is employed, focusing on the problems that the control of the grindstone cutting base becomes complicated and the followability at high speed swinging is difficult. In order to improve the followability when the grindstone cutting table swings at high speed, it is conceivable to use a linear motor with a low resistance for the slide, but there are problems to be solved in terms of cost and the like.

The invention of claim 2 is the machining method according to claim 1, it is characterized in that moving the grindstone depth cutting board with respect to the workpiece spindle. Conventional non-circular cylindrical machining grinders are provided with a rocking shaft in the main shaft, and the rocking shaft and the main shaft are synchronized by a cam to make an elliptical shape. The main axis is the NC axis, and the two axes are synchronously controlled to create an elliptical shape. According to this, there is an advantage that the conventional swing shaft and the cam mechanism device can be omitted. Further, in the case of a normal NC cylindrical grinder, the grindstone cutting table is made NC to improve the cutting position accuracy. Therefore, if it is shared, it is not necessary to add a new NC shaft. However, since the normal NC cylindrical grinder is non-NC with respect to the main shaft, it needs to be NC. In addition, the conventional mechanism had an adverse effect on the shape accuracy due to wear of the cam contact parts, whereas the NC drive system does not require a cam, and a stable shape accuracy can be obtained. It is done.

A third aspect of the present invention, the machining method according to claim 1 or 2, characterized in that it is angular feed. Angular feed refers to cutting a grindstone in a direction that forms an angle other than a right angle with respect to the work spindle. For example, in the case of a straight feed in which a grindstone is cut in a direction perpendicular to the work spindle, when the work or chucking device and the grindstone interfere with each other, an angular feed can be employed to avoid such interference.

A fourth aspect of the present invention, the machining method of claim 1, 2 or 3, the outer peripheral surface shape of the cross section including the rotation axis of the workpiece is characterized in that it is straight. The straight line becomes one straight line when the outer peripheral surface of the workpiece has a straight cylindrical surface shape, but becomes two or more straight lines when it has a stepped cylindrical surface shape. Further, not only a straight line parallel to the rotation axis of the workpiece but also a straight line that forms an angle with respect to the rotation axis is included. In the latter case, the outer peripheral surface shape of the workpiece is a taper.

The invention of claim 5 is the machining method according to claim 1, 2 or 3, characterized in that the outer peripheral surface shape of the cross section including the rotation axis of the workpiece is curved. Specific examples of the curve include a convex arc and a concave arc.

According to a sixth aspect of the invention, the machining method of claim 1, 2 or 3, in which the outer peripheral surface shape of the cross section including the rotation axis of the workpiece characterized in that it is a combination of straight lines and curves. Again, examples of curves include convex arcs and concave arcs.

According to a seventh aspect of the invention, the machining method of any one of claims 1 to 6, the outer peripheral surface in a cross section perpendicular to the axis of rotation of the workpiece is characterized in that an elliptical shape. Here, the ellipse is not limited to the literal ellipse but includes a shape called a so-called oval or oval.

The invention of claim 8 is the machining method of any one of claims 1-6, which is characterized in that the outer peripheral surface shape in a cross-section perpendicular to the axis of rotation of the workpiece is a combination of true circles and ellipses It is.

The invention according to claim 9 is a process of grinding an outer peripheral surface of the leg shaft in a trunnion for a constant velocity joint comprising a boss having a serration hole formed in an axial center portion and a plurality of leg shafts protruding in the radial direction of the boss. The outer peripheral surface has a non-circular outline in cross section perpendicular to the rotation axis of the leg shaft,
A grindstone that holds a work spindle provided with a chucking device and a rotation driving device for holding the trunnion as a workpiece, and a grindstone that is rotationally driven by the rotation driving device, and is fixed to a grindstone cutting table that can be reciprocated by the driving device. An NC machine tool with a shaft,
By grasping the inner diameter of the serration hole by the chucking device and fixing with a clamper, the workpiece is positioned so that one of the leg shafts is coaxial with the workpiece spindle, and the rotational phase of the workpiece spindle is adjusted. In addition, creep feed grinding is performed while controlling the relative position of the workpiece and the grindstone .

  According to the present invention, by adopting creep feed grinding, machining is completed with one rotation of the workpiece, so that high-speed rocking of the incision table is unnecessary, and non-circular shape accuracy can be obtained stably and easily. It is done. In addition, the cycle time is shortened and the machining efficiency is improved.

It is explanatory drawing of a straight feed, Comprising: (A) is a top view, (B) is a front view, (C) is a side view. It is explanatory drawing of an angular feed, Comprising: (A) is a top view, (B) is a front view, (C) is a side view. (A) is a partially broken front view of the trunnion, (B) is a side view, (C) is a plan view of the leg shaft, and (D) is an enlarged view of the leg shaft root portion of FIG. 3 (B). (A) is a partially broken front view of a trunnion with a shaft end protrusion, (B) is a side view, (C) is an enlarged view of the tip of the leg shaft of FIG. 4 (B), and (D) is a plan view of the leg shaft. , (E) is an enlarged view of the base part of the leg shaft of FIG. 4 (B).

  Hereinafter, an embodiment of the present invention will be described by taking as an example a case where a leg shaft of a trunnion that is a constituent element of a tripod type constant velocity joint is ground.

  First, an example of a workpiece will be described. FIG. 3 shows a trunnion 10 of a tripod constant velocity joint. The trunnion 10 includes a boss 12 in which a serration (or spline, hereinafter the same) hole 14 is formed in an axial center portion, and three leg shafts 16 arranged at equal intervals in the circumferential direction of the boss 12. As can be seen from B), each leg shaft 16 protrudes from the boss 12 in the radial direction.

  As can be seen from FIG. 3C, the section 18b of the cross section perpendicular to the axis of the leg shaft 16, that is, the cross section, is elliptical. 18a part is a non-processed part (pre-process remaining part), and only the part of the outer peripheral surface has processed the elliptical shape. As shown in FIG. 3D, the base portion 18d of the leg shaft 16 has a concave arc shape at the grinding round-up relief R portion. As can be seen from FIGS. 3A, 3B, and 3D, the outer peripheral surface of the cross section including the axis of the leg shaft 16, that is, the vertical cross section, is a straight line and a curve parallel to the axis.

  The trunnion 10 ′ shown in FIG. 4 is different from the trunnion 10 of FIG. 3 in that a projection 18c is formed near the end of the leg shaft 16. As can be seen from FIG. 4D, the cross section perpendicular to the axis of the leg shaft 16, that is, the 18b portion of the cross section is elliptical. 18a part is a non-processed part (pre-process remaining part), and is processing the elliptical shape only for a part of outer peripheral surface. The protrusion 18c is provided on the elliptical portion 18b of the outer peripheral surface of the leg shaft 16, is concentric with the elliptical portion, and has a slightly larger diameter. These two straight lines are connected by a straight line formed at an angle with the axis. As can be seen from FIGS. 4A, 4B, and 4E, the outer peripheral surface of the cross section including the axis of the leg shaft 16, that is, the longitudinal cross section, is a straight line and a curve that are parallel to and angled with the axis. In the embodiment of FIG. 4, the bus on the outer peripheral surface is a combination of two long and short straight lines, a taper, and a curved line.

  Next, a processing apparatus having a schematic configuration shown in FIG. 1 will be described. This machining apparatus includes a work spindle 20 and a grindstone shaft 30 that constitute the main part of an NC (numerical control) machine tool. The work spindle 20 is fixed to a stationary member (not shown) such as a base of an NC machine tool, and is provided with a chucking device 22 for holding the work 26 at one end. The chucking device 22 is rotatable about a rotation axis 28 as indicated by an arrow in FIG. A main shaft NC motor 24 is attached to the other end of the work main shaft 20 (upper end in FIG. 1A) as a rotation drive device.

  Although details of the chucking device 22 are omitted in FIG. 1, the workpiece 26 is the trunnion 10, 10 ′ described above with reference to FIGS. 3 and 4, and the inner diameter of the serration hole 14 is set to the collet chuck. This is a type that is grasped and fixed from above with a clamper. Then, the leg shaft 16 to be processed is positioned so as to be coaxial with the work spindle 20.

The grindstone shaft 30 is fixed to a grindstone cutting table 32, and the grindstone cutting table 32 is capable of reciprocating in the X-axis direction indicated by reference numeral 38 by using, for example, a linear slide mechanism and a ball screw mechanism. It is attached to. As a driving device for moving the grindstone cutting table 32, a grindstone cutting table NC motor 34 is also installed on the stationary member. The grindstone shaft 30 has a built-in spindle and is rotationally driven by a motor 35 . The grindstone shaft 30 holds a grindstone 36 on its end surface. As the grindstone 36, a CBN grindstone may be adopted to improve the processing efficiency. The cross-sectional shape of the outer periphery of the grindstone 36 is a shape obtained by transferring the finished shape of the work 26.

  When the selection of the grindstone and the countermeasures are described, when a test was performed using a WA grindstone, which is a general grindstone, abnormal grinding wheel wear due to large grinding resistance resulted in grinding wheel shaft drive power abnormality. Then, when it changed to the CBN grindstone excellent in abrasion resistance, the grindstone shaft drive power became stable and the processing accuracy became good. However, since the CBN grindstone has a high hardness, it is difficult to dress, a good sharpness cannot be obtained, and the processing efficiency is not necessarily improved. As countermeasures, satisfactory processing efficiency can be obtained by reviewing the specifications of the grindstone and diamond roll and reviewing the dressing conditions and processing conditions.

  When the spindle NC motor 24 is started from the state shown in FIG. 1, the workpiece spindle 20 rotates as shown by an arrow in FIG. 1B to rotate the workpiece 26 together with the chucking device 22. Further, the spindle of the grindstone shaft 30 rotates to rotate the grindstone 36. When the grinding wheel cutting table NC motor 34 starts, the grinding wheel cutting table 32 moves in the X-axis direction in FIG. 1A and in the left or right direction in FIG. 1A depending on the rotation direction of the NC motor 34. The moving direction and moving amount of the grindstone cutting base 32 are programmed in advance in the NC controller in synchronization with the rotation axis of the workpiece. That is, in order to obtain a desired non-round shape, the grindstone cutting base 32 is moved in the direction of the movement axis 38 in synchronization with the rotation of the workpiece spindle 20 by NC control, and the phase of the rotation axis 28 of the workpiece spindle 20 and the grinding wheel 36 are moved. Is associated with the position.

The processing is performed by a creep feed method, and is completed when the work 26 rotates once. Examples of processing conditions are as follows.
Work material: SCM420H
Cutting speed in workpiece tangential direction: 30mm / s
Whetstone: Vitrified CBN whetstone particle size # 100 Concentration 150
Grinding wheel peripheral speed Processing: 60m / s
Wheel peripheral speed During dress truing: 31 m / s
Grinding fluid: Water-soluble emulsion type Dresser: Traverse rotary diamond Dresser rotation speed: 5000m ^-1

  FIG. 1 shows an example of a so-called straight feed in which a grindstone 36 is cut in a direction orthogonal to the rotation axis 28 of the work spindle 20 (X-axis 38 direction). On the other hand, as shown in FIG. 2, it is possible to employ an angular feed that cuts the grindstone 36 obliquely with respect to the rotating shaft 28 of the work spindle 20. For example, by employing an angular feed, interference between the chucking device 22 of the work spindle 20 and the grindstone 36 can be avoided.

  A post process gauge may be employed for managing the dimensions of the ellipse major axis. An in-process gauge is used as the dimension measurement gauge used in a normal grinder, but here, since a creep feed that completes processing with one rotation of the workpiece is adopted, normal in-process is impossible, and the processed value is The post process is controlled by feedback. However, in this method, the dimensions immediately after dressing and immediately after the machine stops are unstable due to temperature characteristics. As a countermeasure, it is conceivable to adopt a method of performing n-rotating machining until one of the workpieces is processed within the dimensional tolerance. The first rotation is a method in which processing is performed while measuring the positive size from the exact size, and processing is performed by incorporating the value in the second rotation. This is repeated n times until it is within the dimensional tolerance. However, although the dimensional accuracy can be stabilized by doing in this way, the cycle time is increased, and therefore it is preferable that the dimensional accuracy is set only immediately after the stop.

10 trunnion 12 boss 14 serration hole 16 leg shaft 18a ellipse non-machined part 18b ellipse machined part 18c projection 18d leg shaft root part (grinding up relief part R)
18e Protrusion outer taper portion 18f Protrusion inner taper portion 20 Work spindle 22 Chucking device 24 NC motor 26 Work 28 Rotating shaft 30 Grinding wheel shaft 32 Grinding wheel cutting base 34 NC motor 36 Grinding wheel 38 Moving shaft

Claims (9)

A processing method of grinding an outer peripheral surface of the leg shaft in a trunnion comprising a boss having serration holes formed in an axial center portion and a plurality of leg shafts arranged at equal intervals in the circumferential direction of the boss, Is a non-circular outline of the cross section perpendicular to the rotation axis of the leg shaft, and consists of a non-processed portion facing the axial direction of the boss and an elliptical portion facing the circumferential direction of the boss,
A workpiece spindle provided with a chucking device and the rotary drive device for holding a workpiece, holds the grinding wheel, using the NC machine tool and a grinding wheel spindle fixed to the grindstone depth cutting board reciprocally movable by a drive, wherein The chucking device grasps the inner diameter of the serration hole and fixes it with a clamper to position the leg shaft to be machined so that it is coaxial with the workpiece spindle, and the relative position of the workpiece and the grindstone according to the rotation phase of the workpiece spindle Of trunnion of tripod type constant velocity joint that performs creep feed grinding while controlling the pressure. Machining method of claim 1 for moving the grinding wheel cross-slide with respect to the workpiece spindle. Machining method according to claim 1 or 2 by angular feed. How machining according to claim 1, 2 or 3 the outer peripheral surface shape in the cross section including the axial line of the workpiece is linear. How machining according to claim 1, 2 or 3 the outer peripheral surface shape in the cross section including the axial line of the workpiece is curved. How machining according to claim 1, 2 or 3 the outer peripheral surface shape is a combination of straight and curved in a cross section including the axis of the workpiece. Machining method of any one of claims 1 to 6 an outer peripheral surface shape in the vertical cross-section is elliptical to the axis of the workpiece. How machining of any one of claims 1 to 6 an outer peripheral surface shape is a combination of true circles and ellipses in a cross-section perpendicular to the axis of the workpiece. A processing device for grinding an outer peripheral surface of the leg shaft in a trunnion for a constant velocity joint comprising a boss having a serration hole formed in an axial center portion and a plurality of leg shafts protruding in the radial direction of the boss, The surface has a non-circular outline of a cross section perpendicular to the rotation axis of the leg shaft, and is composed of a non-processed portion facing the axial direction of the boss and an elliptical portion facing the circumferential direction of the boss,
A grindstone that holds a work spindle provided with a chucking device and a rotation driving device for holding the trunnion as a workpiece, and a grindstone that is rotationally driven by the rotation driving device, and is fixed to a grindstone cutting table that can be reciprocated by the driving device. An NC machine tool with a shaft,
By grasping the inner diameter of the serration hole by the chucking device and fixing with a clamper, the workpiece is positioned so that one of the leg shafts is coaxial with the workpiece spindle, and the rotational phase of the workpiece spindle is adjusted. A processing apparatus that performs creep feed grinding while controlling the relative position between the workpiece and the grindstone .

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