JP2009190097A - Superfinishing method and grinding machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a superfinishing method for shortening machining time and also to provide a grinding machine for superfinishing. <P>SOLUTION: In this superfinishing method by use of a superfinishing grinding wheel 11, a workpiece W having a surface 12 to be machined being a peripheral face of a truncated cone or a circular cone is rotated around an axis of the truncated cone or the circular cone, the superfinishing grinding wheel having a polygonal grinding surface 46 is vibrated and rotated and is pressed against the rotating surface to be machined, and the superfinishing grinding wheel is reciprocatingly moved between a travel end set on a rotation center side of the surface to be machined and a travel end set on an outward side while the superfinishing grinding wheel is pressed against the surface to be machined. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a superfinishing method and a grinding apparatus that performs superfinishing.

Super-finishing (machining) that grinds a workpiece while applying vibration to the grinding wheel can maintain the grindability of the grinding wheel for a long time and is relatively easy to mirror finish. Has been adopted.
Superfinishing is intended to make mirror surface processing easy because the abrasive grains that fall off when the surface to be ground (surface to be ground) becomes smooth clogs the grindstone and makes the surface of the grindstone finer to facilitate mirror finishing. Those having low bond strength are used. Therefore, at the time of grinding, falling abrasive grains unnecessary for clogging of the grindstone are removed by grinding oil or cooling water poured on the processed surface.

In super-finishing, if the grinding surface area of the grinding stone is large, the inner falling abrasive grains are difficult to remove, and the remaining unnecessary abrasive grains grind the grinding surface, so that proper mirror finishing cannot be performed. . Therefore, in a grindstone having a large apparent area of the grinding surface, a recess or the like is usually provided on the grinding surface to reduce the actual grinding area and suppress the generation of abrasive grains that fall off. Thus, in superfinishing, even if the grindstone is large, there is a problem that the grinding surface cannot be made as large as it appears, and if the surface to be ground of the workpiece becomes large, the machining time becomes longer accordingly.
To solve this problem, for example, in order to shorten the processing time in the superfinishing of the outer peripheral surface of the spherical roller, an attempt is made to swing the grindstone in a direction intersecting the axis of the spherical roller (Patent Document 1).

Also, there is a processing method for preparing a plurality of grindstones (grinding grindstones and superfinishing grindstones) for a workpiece having a plurality of grinding target surfaces, and repeatedly waiting and grinding the plural grindstones to improve the efficiency of grinding. It has been proposed (Patent Document 2).
JP 2007-168055 A JP 2003-94303 A

The method attempted in Patent Document 1 cannot swing the grindstone while rotating the workpiece unless the surface to be ground is spherical, and is difficult to apply to workpieces of other shapes. The method proposed in Patent Document 2 requires that a plurality of grinding target surfaces exist in a predetermined positional relationship, and a positional relationship between a workpiece having a single grinding symmetry surface and a plurality of grinding target surfaces. Is difficult to apply to workpieces that do not meet the prescribed requirements.
The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a superfinishing method and a grinding apparatus for performing superfinishing that can shorten the grinding time.

In order to achieve the above object, the present invention takes the following technical means.
That is, the superfinishing method according to the present invention rotates a workpiece whose grinding surface is a circumferential surface of a truncated cone or a circumferential surface of a cone around the axis of the truncated cone or the cone, and the grinding surface is polygonal. A moving end set on the rotation center side of the surface to be ground in a state where the surface to be ground is pressed while vibrating and rotating a superfinishing wheel and the surface to be ground is pressed against the surface to be ground. Grinding is performed by reciprocating between the moving end set on the outer side and the moving end.
Preferably, grinding is performed by increasing the rotational speed of the workpiece so that the position of the superfinishing wheel in the reciprocating movement is closer to the center of rotation of the surface to be ground.

More preferably, the number of rotations of the workpiece, the number of vibrations of the superfinishing grindstone, the number of rotations, the speed of movement during the reciprocating movement, and the number of times of reciprocating movement are combined in combination. To grind.
When the shape of the grinding surface of the superfinishing grindstone is square, it is effective for shortening the grinding time.
A grinding apparatus according to the present invention holds a workpiece whose surface to be ground is a circumferential surface of a truncated cone or a circumferential surface of a cone, and rotates the workpiece around the axis of the truncated cone or the cone, A grindstone rotating device for holding and rotating a superfinishing grindstone having a polygonal grinding surface, a vibration applying device for vibrating the superfinishing grindstone, and the superfinishing grindstone on the surface to be ground of the workpiece And a lateral movement device for moving between an inner moving end and an outer moving end of the surface to be ground.

The workpiece rotating device is formed such that the number of rotations thereof can be increased or decreased in conjunction with the movement of the superfinishing grindstone along the surface to be ground.
When the shape of the grinding surface of the superfinishing grindstone is square, it is effective for shortening the grinding time.
Preferably, the rotational speed of the workpiece rotating device, the rotational speed of the grindstone rotating device, the vibration frequency of the vibration applying device, and the moving speed and the number of times of movement of the superfinishing grindstone by the lateral moving device A storage unit for storing each set value, and the workpiece rotating device, the grindstone rotating device, the grindstone rotating device, so as to continuously perform grinding under a plurality of grinding conditions in which any one or all of these set values are different And a control unit that controls the vibration applying device and the lateral movement device.

  “Continuous grinding under a plurality of grinding conditions” here means that a series of grinding processes under a plurality of different grinding conditions are performed continuously without interruption, for example, by replacing a superfinishing wheel. Say.

  ADVANTAGE OF THE INVENTION According to this invention, the grinding | polishing apparatus which performs the superfinishing method and superfinishing which can shorten grinding time can be provided.

1 is a front view of a main part of a grinding apparatus 1 for performing superfinishing, FIG. 2 is a side view of the grinding apparatus 1, FIG. 3 is a perspective view of the vicinity of a superfinishing grindstone 11 in the grinding apparatus 1, and FIG. (Workpiece) W is a perspective view, FIG. 5 is a view showing the configuration of the control device 2, and FIG. 6 is a view showing the movement of the superfinishing grindstone 11 as seen from the direction of arrows AA in FIG.
“Superfinishing” performed by the grinding apparatus 1 means that the workpiece W or the superfinishing grindstone 11 is vibrated while pressing the superfinishing grindstone 11 against the workpiece W to finish the ground surface 12 of the workpiece W. In the following description, “lateral direction” refers to the horizontal direction (left-right direction) in FIG. 1, and “vertical direction” refers to the vertical direction in FIG. The “vertical direction” is a vertical direction in the grinding apparatus 1.

The grinding device 1 includes a grindstone rotating device 3, a grindstone pressing device, a grindstone position moving device 4, a workpiece rotating device 5, and a control device 2.
The grindstone rotating device 3 is for holding and rotating the superfinishing grindstone 11.
The grindstone rotating device 3 includes a grindstone holding unit 13 that holds the superfinishing grindstone 11, a grindstone rotating motor 14 for rotating the grindstone holding unit 13, and the like.
A servo motor is used as the grinding wheel rotating motor 14, and the rotation thereof is controlled by the control device 2.

  The grindstone pressing device is a device for pressing the superfinishing grindstone 11 held by the grindstone holding unit 13 against the workpiece W. The grindstone pressing device is for pressing the superfinishing grindstone 11 toward the workpiece W side. In the grindstone pressing device, a plurality of air pressure adjusting valves, each having a different adjusting pressure, are connected in parallel to an air flow path to an air-hydro device that generates a hydraulic pressure for pressing. Each air pressure adjusting valve is connected to an air pressure source, and an automatic valve 15 is connected between each air pressure adjusting valve and the air-hydro apparatus. The force with which the superfinishing grindstone 11 presses the workpiece W is selected by opening one of the automatic valves 15. The automatic valve 15 is opened and closed by the control device 2.

The grindstone position moving device 4 includes a lateral moving device 6, a vibration applying device 7, a tilting device, and a vertical moving device 8.
The lateral movement device 6 is for moving (traversing) the superfinishing grindstone 11 along the surface to be ground (surface to be ground) 12 of the workpiece W. The lateral movement device 6 includes a lateral movement ball screw, a lateral movement slider that reciprocates in the axial direction of the lateral movement ball screw by the rotation of the lateral movement ball screw, and a lateral movement motor 16 that rotates the lateral movement ball screw. The laterally moving ball screw is arranged such that its axial center extends substantially in the lateral direction. The lateral movement device 6 is integrated with the tilting device, and tilts as the tilting device tilts.

The lateral movement slider is fixedly integrated with the frame 17 in the vibration applying device 7 and reciprocates according to the rotation of the ball screw for horizontal movement, thereby moving the vibration applying device 7 integrated with the grindstone rotating device 3 laterally. Move back and forth in the direction.
A servo motor is used as the lateral movement motor 16, and its rotation is controlled by the control device 2.
The vibration applying device 7 includes a support body 18, a balance body 19, two support shafts 20, 21, a frame 17, an oscillation ring 22, a vibration motor 23 (see FIG. 5), and the like.

The support body 18 supports the grindstone rotating device 3 in a fixed manner. The support body portion 18 is provided with two holes having a circle in the vertical direction and penetrating in the same direction as the axis of the ball screw for lateral movement and having the same cross section. In addition, the axial center direction of the ball screw for lateral movement is also a direction orthogonal to the rotating shaft 24 of the grindstone rotating device 3. The support body portion 18 includes a vibration transmission portion 25 formed of a thick plate and fixed between two holes on one side surface in the lateral direction.
The balance body 19 is disposed beside the support body 18 with a space from the support body 18. The balance body 19 has substantially the same shape as the support body 18 in a front view (FIG. 1). The balance barrel 19 has the same cross-sectional shape as the two holes of the support barrel 18 and has the same gap as the two holes of the support barrel 18 and penetrates in the axial direction of the ball screw for lateral movement. With two holes. The balance drum portion 19 is formed to have substantially the same weight as the support drum portion 18 including the grindstone rotating device 3. The balance body portion 19 includes a vibration transmission portion 26 formed of a thick plate between two holes on the side surface on the support body portion 18 side. In addition, the vibration transmission part 25 in the support trunk | drum 18 demonstrated previously is provided in the side which faces the balance trunk | drum 19 so that the vibration transmission part 26 of the balance trunk | drum 19 may be opposed.

One of the support shafts 20, 21 passes through the hole above the support body 18 and the hole above the balance body 19, and the other one is the hole below the support body 18 and the balance body 19. It penetrates the lower hole. Both of the support shafts 20 and 21 are fixed to the frame 17 at both ends thereof, and can be moved relative to each other via air bearings provided in the holes of the support drum portion 18 and the balance drum portion 19. The balance body 19 is supported. The axial center direction of the support shafts 20 and 21 coincides with the axial center direction of the lateral movement ball screw.
The frame 17 is a horizontally long rectangular frame when viewed from the front (FIG. 1), and is fixed to the horizontal movement slider and moves in a substantially horizontal direction along with the movement of the horizontal movement slider.

The oscillation ring 22 has a substantially cylindrical shape, and is rotated around a rotation axis Rc deviated from the cylindrical axis by the vibration motor 23. The oscillation ring 22 has its rotation axis Rc in a direction orthogonal to both the axial direction of the support shafts 20 and 21 and the rotation axis 24 of the grindstone rotating device 3, so that the support barrel 18 and the balance ring 22 are balanced. It is disposed between the two support shafts 20, 21 between the body portion 19.
Both the support body 18 and the balance body 19 are urged toward the oscillation ring 22 so that the vibration transmitting portions 25 and 26 abut against the oscillation ring 22. This biasing is performed by a spring.

A servo motor is used as the vibration motor 23, and its rotation is controlled by the control device 2.
The tilting device is integrated with the lateral movement device 6 and tilts the lateral movement device 6 by an angle set (input) with respect to its horizontal position (two-dot chain line by a thin line in FIG. 1). The tilting device holds the lateral movement device 6 so as to tilt the lateral movement device 6 while maintaining the state where the two support shafts 20 and 21 are vertically moved up and down. The degree of tilting of the lateral movement device 6 by the tilting device is controlled by the control device 2. The lateral movement slider of the lateral movement device 6 is integrated with the frame 17 of the vibration applying device 7, and the support drum portion 18 of the vibration applying device 7 is integrated with the grindstone rotating device 3. Thus, the rotating shaft 24 of the grindstone is inclined. The tilting angle of the tilting device is adjusted by the tilting motor 27 controlled by the control device 2. A servo motor is used for the tilting motor 27.

  The vertical movement device 8 is for moving the tilting device integrated with the horizontal movement device 6 up and down (reciprocating in the vertical direction). The vertical movement device 8 includes a vertical movement ball screw 28, a vertical movement slider that reciprocates in the axial direction of the vertical movement ball screw 28 by the rotation of the vertical movement ball screw 28, and a vertical movement motor that rotates the vertical movement ball screw 28. 29. The ball screw 28 for vertical movement is arranged so that its axis is in the vertical direction in FIGS. 1 and 2. A servo motor is used as the vertical movement motor 29, and its rotation is controlled by the control device 2.

The workpiece rotating device 5 is for holding and rotating the workpiece W to be ground. The workpiece rotating device 5 includes a workpiece holding unit 30, a workpiece rotating motor 31, and the like. The workpiece holding part 30 fixes the workpiece W integrally. The work rotation device 5 is arranged so that the rotation axis thereof intersects with the extension line of the locus of the rotation center point on the grinding surface of the superfinishing grindstone 11 when the grindstone rotation device 3 moves in the lateral direction.
In addition, when the inclination angle of the lateral movement device 6 is zero, the control device 2 includes a lateral movement slider (grinding wheel rotation device 3) when the rotation shaft of the workpiece rotation device 5 overlaps with the rotation shaft 24 of the superfinishing grindstone 11. ) In the horizontal direction (hereinafter referred to as “reference position”) is stored in advance as “coordinates” described after the standard position.

1 to 4, the workpiece W fixed by the workpiece holder 30 includes a truncated cone portion 32 having a truncated cone shape, and a substantially cylindrical bush portion protruding from the lower bottom surface of the truncated cone portion 32. 33. The workpiece W has an opening in the upper bottom surface of the truncated cone portion 32 and includes a hole that extends from the opening portion to the hollow portion of the bush portion 33 and penetrates in the axial direction. The peripheral surface of the truncated cone in the truncated cone part 32 is the surface 12 to be ground.
The workpiece holding unit 30 fixes the workpiece W with the surface to be ground 12 facing upward.
The workpiece rotation motor 31 rotates the workpiece holding unit 30 about its axis. A servomotor is used as the workpiece rotation motor 31, and the rotation is controlled by the control device 2.

The control device 2 includes a control unit 34, a grindstone rotation management unit 35, a lateral movement management unit 36, a vibration management unit 37, an inclination management unit 38, a vertical movement management unit 39, a workpiece rotation management unit 40, a press management unit 41, and an input. The unit 42, the storage unit 43, a clock 44, an interface 45, and the like.
The control unit 34 controls the overall operation of the control device 2.
In the grindstone rotation management unit 35, the vibration management unit 37, and the workpiece rotation management unit 40, the grindstone rotation motor 14, the vibration motor 23, and the workpiece rotation motor 31 rotate at the rotation speeds indicated by the control unit 34, respectively. To control. Instructions by the grindstone rotation management unit 35, vibration management unit 37, and workpiece rotation management unit 40 are converted into respective rotation operations of the grindstone rotation motor 14, the vibration motor 23, and the workpiece rotation motor 31 via the interface 45. Is done. The encoder outputs related to the rotational speeds from the grinding wheel rotating motor 14, the vibration motor 23, and the workpiece rotating motor 31 are used for feedback control of these rotational speeds.

The lateral movement management unit 36 and the vertical movement management unit 39 are respectively based on instructions from the control unit 34, the rotational direction (forward rotation, reverse rotation), rotational speed, and integrated rotation of the lateral movement motor 16 and the vertical movement motor 29. Control the number. Instructions from the lateral movement management unit 36 and the vertical movement management unit 39 are converted into respective rotational operations of the lateral movement motor 16 and the vertical movement motor 29 via the interface 45. Encoder outputs related to rotation from the lateral movement motor 16 and the vertical movement motor 29 are used for feedback control of these rotations.
The inclination management unit 38 rotates the inclination motor 27 in the normal direction or the reverse direction by the total number of rotations corresponding to the inclination angle indicated by the control unit 34. The rotation of the tilting motor 27 is used for feedback control by the encoder.

The press management unit 41 controls the opening and closing of the automatic valves 15 individually connected to the plurality of air pressure adjustment valves.
The input unit 42 inputs the operating conditions of the grinding apparatus 1, for example, the rotational speed (number of rotations) of the superfinishing grindstone 11, the lateral movement speed of the superfinishing grindstone 11, the vibration frequency of the superfinishing grindstone 11, and the like. belongs to. Each input operating condition is stored in the storage unit 43 via the interface 45 and the control unit 34.
The storage unit 43 stores each operation condition of the grinding apparatus 1, and also includes a control unit 34, a grindstone rotation management unit 35, a lateral movement management unit 36, a vibration management unit 37, an inclination management unit 38, a vertical movement management unit 39, and a workpiece. The rotation management unit 40 stores temporary data.

The clock 44 transmits a reference time for performing time management of operations performed by the control device 2.
The interface 45 converts the data output from the grinding wheel rotation management unit 35 and the like into a frequency of a current for driving the grinding wheel rotation motor 14 and the like. The input data from the input device is digitized and output to the control unit 34.
The control unit 34, the grindstone rotation management unit 35, the lateral movement management unit 36, the vibration management unit 37, the tilt management unit 38, the vertical movement management unit 39, and the workpiece rotation management unit 40 are RAMs in which a CPU and an operation program are stored. Realized. The input unit 42 is realized by a keyboard or a touch panel, and the storage unit 43 is realized by an external storage device such as a RAM and a hard disk. The clock 44 uses an internal clock for operating a CPU or the like, and the interface 45 is realized by a servo amplifier, an A / D converter, a digital relay, or the like for driving a servo motor.

Next, a superfinishing method for the workpiece W by the grinding apparatus 1 will be described.
The superfinishing process is composed of three processes: a rough grinding process, a medium grinding process, and a finish grinding process.
The rotational speed of the superfinishing wheel 11 (determined by the rotational speed of the grinding wheel rotation motor 14 in the rough grinding process, intermediate grinding process, and finish grinding process, hereinafter referred to as “grinding wheel rotational speed”), the frequency of the superfinishing grindstone 11 ( It is determined by the number of rotations of the vibration motor 23. Hereinafter referred to as “frequency”, the lateral movement speed of the superfinishing grindstone 11 (hereinafter referred to as “traverse speed”), and the number of lateral movements of the superfinishing grindstone 11 (one-way (Hereinafter referred to as “the number of traverses”), the retention (movement stop) time of the superfinishing grindstone 11 at both moving ends in the lateral direction (hereinafter referred to as “inner tally time” for the inner moving end, At the moving end on the other side is referred to as “outer tally time”), determined by the basic rotational speed of the workpiece W (determined by the rotational speed of the workpiece rotating motor 31; hereinafter referred to as “basic rotational speed”) and super finishing. Force lower grindstone 11 to press the workpiece W (hereinafter referred to as "pressing force"), before superfinished, that number separately in each step is input through the input unit 42 to the controller 2.

In the superfinishing by the grinding device 1, the rotational speed of the workpiece W is continuously changed in accordance with the lateral movement of the superfinishing grindstone 11 in all three grinding steps. The “basic rotation speed” is the rotation speed when the superfinishing grindstone 11 is positioned at the outer moving end.
Further, the pressing force in each step is determined by selecting the automatic valve 15 connected to the air pressure regulating valve set so as to obtain the pressing force to be adopted and inputting it to the control device 2. For example, the number of the selected automatic valve 15 is stored in the storage unit 43 for each process.
The lateral movement distance (hereinafter referred to as “traverse distance”) of the superfinishing grindstone 11 and the inclination angle (hereinafter referred to as “inclination angle”) of the lateral movement device 6 inclined by the inclination device are determined by the surface of the workpiece W to be ground 12. A value determined based on the shape (mainly the degree of inclination of the generatrix in the truncated cone) is input to the control device 2 before superfinishing. For example, in the workpiece W shown in FIG. 4, the traverse distance is determined in consideration of the shape of the grinding surface of the superfinishing grindstone 11 in the length of the generatrix GE of the surface 12 to be ground. The angle formed by the lower bottom surface is the inclination angle.

The movement start position of the superfinishing grindstone 11 with respect to the workpiece W is set in a state in which the amplitude by the vibration device is zero (a state where the axis of the oscillation ring 22 and the rotation axis Rc are aligned in the vertical direction). 6 is tilted to an inclination angle, and the operator manually operates the lateral movement device 6 and the vertical movement device 8 to move the superfinishing grindstone 11 to the movement start position (that is, the outer moving end of the workpiece W on the ground surface 12). And the position (in the lateral movement device 6 and the vertical movement device 8) is stored in the control device 2.
The position of the superfinishing grindstone 11 (strictly speaking, “the position of the rotation center point of the grinding surface of the superfinishing grindstone 11”) is stored in the direction in which the ball screw for lateral movement extends in the control device 2 (the lateral movement device 6 This is performed as a coordinate in a two-dimensional plane including the “horizontal direction” even when tilted, and the direction of the axis of the ball screw 28 for vertical movement (hereinafter, “vertical direction”). Therefore, the horizontal coordinate axis is horizontal when the horizontal movement device 6 is not inclined and the inclination angle is zero, and when the horizontal movement device 6 is inclined, the horizontal coordinate axis is inclined by an inclination angle with respect to the horizontal direction. (See FIG. 4). Since the lateral movement management unit 36 manages the movement distance and the like of the lateral movement slider (such as the cumulative number of rotations of the ball screw for lateral movement), it is easier to manage by linking the direction of the horizontal coordinate axis to the inclination angle in this way. It is.

The position of the inner moving end is determined as follows. That is, the distance D in the vertical direction from the center of swinging by the tilting device when the tilt angle is zero (in FIG. 1, the case where it coincides with the rotation center Rc of the oscillation ring 22) to the grinding surface of the superfinishing grindstone 11. _{Based on 1} and the inclination angle when grinding is actually performed, a distance D ₂ where the rotation center of the grinding surface of the superfinishing grindstone 11 deviates from the rotation center of the workpiece rotation device 5 when the lateral movement device 6 is inclined. Ask. This distance D ₂ is
D ₂ = D ₁ × tan (inclination angle) (1)
It is requested from. From this distance D ₂ between the reference position stored in the storage unit 43, to correct the position where the rotational center of the grinding surface to overlap the rotational center of the workpiece rotating device 5 when the transverse movement device 6 is inclined (coordinates), The position of the inner moving end is calculated from this position and the stored traverse distance and the position of the outer moving end. Note that the position when the rotation center of the grinding surface of the superfinishing grindstone 11 coincides with the rotation center of the workpiece rotating device 5 is calculated in advance, and the position of the outer moving end is set inward. The position of the moving end can be calculated.

  Table 1 shows an example of superfinishing conditions.

The superfinishing conditions shown in Table 1 relate to the grinding of the workpiece W shown in FIG. The ground surface 12 of the workpiece W has an outer diameter of 175 mm, an inner diameter of 52 mm, and an inclination angle of the ground surface 12 with respect to the lower bottom surface of the generating line is 11 degrees. The superfinished grindstone 11 used is a square having a grinding surface of 25 mm × 25 mm. This superfinishing grindstone 11 is a DD4000K-VES manufactured by Mizuho Corporation, and coolant oil is also used during grinding.
The “amplitude” in Table 1 is determined by the distance between the geometric center of the section of the oscillation ring 22 and the center of rotation, and if the oscillation ring 22 having a large distance is used, the amplitude increases and vice versa. If so, the amplitude decreases. The pressing force is calculated from the adjustment pressure of each air pressure adjustment valve and the area of the grinding surface of the superfinishing grindstone 11.

Traverse distance (mm) is
Traverse distance = (175−52) ÷ 2 ÷ cos (11 degrees) −25 + α (2)
Determined from. Here, α is a value for determining the superfinishing grindstone 11 even when the center of the grinding surface is erroneously set to the outside of the outer edge of the surface 12 to be ground when manually determining the outer moving end. This is an increment (2.35 mm) added to the geometrically calculated moving distance so that the surface to be ground 12 can be moved to the inner end edge.
In the grinding apparatus 1, the lateral movement device 6 is inclined from the horizontal state to the inclination angle by the tilting device before the superfinishing process, and the superfinishing grindstone 11 is moved to the outer moving end by the lateral movement device 6. At this time, the superfinishing grindstone 11 is not in contact with the workpiece W and is positioned above it with a gap.

The rough grinding process, the intermediate grinding process, and the finish grinding process differ in the conditions shown in Table 1, but the operation of the grinding apparatus 1 is performed in the same manner in all processes.
Rough grinding is performed as follows.
When the start of machining is instructed to the control device 2 by a machining start switch or the like, the workpiece rotating device 5 starts to rotate the workpiece W at the basic rotation speed (300 rpm). The grindstone rotating device 3 also starts to rotate the superfinishing grindstone 11 at the set grindstone rotation speed (3000 rpm). The rotation direction of the workpiece W and the rotation direction of the superfinishing grindstone 11 are the same as shown in FIG.

The vibration applying device 7 vibrates the grindstone rotating device 3 at a set frequency (1500 fpm).
The vibration (oscillation) of the grindstone rotating device 3 by the vibration applying device 7 is such that the peripheral surface of the oscillation ring 22 in contact with the vibration transmitting portion 25 of the support barrel 18 that fixes the grindstone rotating device 3 has a rotational axis Rc geometrically. This occurs when the distance from the rotation axis Rc changes periodically because of deviation from the geometric center. Since the support drum portion 18 is always urged toward the balance drum portion 19 side, the movement of the support drum portion 18 in the direction away from the balance drum portion 19 due to vibration is caused by the oscillation ring 22 to support the support drum portion. The movement in the direction in which 18 approaches the balance body 19 is performed by an urging force, and vibration of the grinding surface of the superfinishing grindstone 11 occurs.

The pressing management unit 41 opens the automatic valve 15 selected for the rough grinding process, and can press the grinding surface 12 with the pressing force (4.4 kg / cm ² ) by which the grinding surface of the superfinishing grindstone 11 is selected. Put it in a state.
The vertical movement device 8 lowers the horizontal movement device 6 to a position where the grinding surface of the superfinishing grindstone 11 contacts the surface to be ground 12 of the workpiece W. Thereafter, rough grinding is started with the set pressing force, grindstone rotation speed, vibration amplitude (1.5 mm), vibration frequency, and basic rotation speed of the workpiece W.

  The superfinishing wheel 11 stays at the outer moving end during the outer tally time (0.2 sec.), And then moves at the traverse speed (60 mm / sec.) Set toward the inner side of the workpiece W. (FIG. 5). The workpiece rotation management unit 40 increases the number of rotations of the workpiece W according to the position of the moving superfinishing grindstone 11. The rotational speed of the workpiece W is controlled so that the peripheral speed of the workpiece W is substantially constant at a position where the rotation center of the grinding surface of the superfinishing grindstone 11 is located. Specifically, the workpiece rotation speed n is calculated by the control unit 34 according to the following equation (3) and is changed by the workpiece rotation management unit 40 (see FIG. 4).

Workpiece rotation speed n = (L ₀ × N) ÷ (L ₀ −L) (3)
In Equation (3), L ₀ is a lateral component in the coordinates of the outer moving end, N is the basic rotational speed, and L is the traverse distance. The superfinishing grindstone 11 moves toward the inner moving end while rotating at the set grindstone rotation speed. During this time, the workpiece W gradually increases its rotation speed, and the ground surface 12 is gradually ground from the outer edge toward the inner edge. Moreover, it can be said that the superfinishing grindstone 11 moves in the radial direction of the workpiece W rotating at this time.
The superfinishing grindstone 11 stops its movement when it moves the traverse distance and reaches the inner moving end. When the inner tally time (0.3 sec.) Has elapsed at the inner moving end, the superfinishing grindstone 11 starts moving at the traverse speed toward the outer moving end. The rotation speed of the workpiece W rotated by the workpiece rotation device 5 continuously decreases to the workpiece rotation speed n obtained by the equation (3) as the superfinishing grindstone 11 approaches the outer moving end. .

When the superfinishing grindstone 11 reciprocates one way 6 times (3 reciprocations) which is the number of traverses stored in the control device 2, the rough grinding process is completed.
In the coarse grinding process, the lateral movement management unit 36 is controlled by the lateral movement motor 16 in accordance with an instruction from the control unit 34 for staying at the outer moving end, lateral movement (traverse), traverse speed, and staying at the inner moving end. This is done by controlling the rotation of. Further, the rotation speed of the workpiece rotating device 5 is performed when the workpiece rotation managing unit 40 controls the rotation of the workpiece rotating motor 31 in accordance with an instruction from the control unit 34.

  The super-finishing grindstone 11 moves in the last lateral direction, reaches the outer moving end, and at the same time the rough grinding process is finished, the middle grinding process is started. The rotation speed of the workpiece W is changed to the basic rotation speed in the medium grinding by the workpiece rotation management unit 40, and the vibration frequency, the pressing force, and the grindstone rotation speed are also changed to the set values in the middle grinding by the control unit 34 and the like. The superfinishing wheel 11 stays at the outer moving end for the outer tally time (0.2 sec.) And performs grinding, and then moves to the inner moving end at the set traverse speed (60 mm / sec.). Start moving. During this movement, the work speed n is continuously changed to the speed calculated by the equation (3). The stay at the inner moving end of the superfinishing grindstone 11 and the movement toward the outer moving end are performed in the same manner as in the rough grinding process.

The transition from the intermediate grinding process to the finish grinding process is continuously performed in the same manner as the transition from the rough grinding process to the intermediate grinding process. Simultaneously with the transition to the finish grinding step, the basic rotation speed, vibration frequency, pressing force and grindstone rotation speed of the workpiece W are changed by the control device 2. Even in the finish grinding process, the grinding apparatus 1 performs the same operation as the rough grinding process and the intermediate grinding process, except that the grinding conditions are different.
In the finish grinding process, when the superfinishing grindstone 11 finishes the last lateral movement and reaches the inner moving end, the vertical movement device 8 raises the lateral movement device 6 and the superfinishing process is finished.
As described above, the grinding apparatus 1 stores various conditions for performing the grinding process in the control apparatus 2 in advance, and separately stores the three processes of the rough grinding process, the intermediate grinding process, and the finish grinding process. It can be implemented based on various conditions. The grinding apparatus 1 can perform super-finishing processing including a plurality of processes, ie, a rough grinding process, a middle grinding process, and a finish grinding process, with different grinding conditions without replacing the super-finishing grindstone 11. Finishing can be performed automatically. The grinding apparatus 1 can also automate a series of grinding processes even when the superfinishing process is divided into more grinding processes.

The superfinishing process described above is divided into three steps of a rough grinding step, a middle grinding step, and a finish grinding step. In any of these steps, (a) the superfinishing grindstone 11 whose grinding surface is square ( b) Vibrating while rotating; (c) Grinding is performed by changing the rotational speed of the workpiece W according to the position of the grinding surface.
Next, by these means (a) to (c), grinding with the average roughness Ra of the surface to be ground 12 of the workpiece W (pulley in a continuously variable transmission of an automobile) shown in FIG. The effect of shortening the processing time will be described.

  In order to examine the effect of the shape of the grinding surface of the superfinishing wheel, a superfinishing stone having a substantially the same area and a round grinding surface is used instead of the square superfinishing stone 11 having a grinding surface of 25 mm × 25 mm. The superfinishing was performed by changing the number of traverses in Table 1 in various ways. As a result, the grinding time required for setting the average roughness Ra of the ground surface 12 to be equal to that of the superfinished grinding stone 11 having a square grinding surface to 0.01 (including the superfinishing wheel including the outer tally time) It has been found that the grinding time of the surface 12 is about 1.5 to 2 times longer for the superfinishing wheel having a round grinding surface than the grinding time of the square superfinishing wheel 11. Even when grinding using a superfinishing wheel with a regular pentagonal or regular hexagonal grinding surface, it is possible to perform grinding with the same surface roughness in a shorter time than when using a superfinishing wheel with a round grinding surface. It was. The grinding time required to set the average roughness Ra of the surface 12 to be ground to 0.01 was shorter for the regular pentagon than for the regular hexagon, and shorter for the square than for the regular pentagon. From this, when the area of a grinding surface is the same, it is estimated that grinding is completed in a shorter time as the total length of the edge is longer. Grinding can be completed in a shorter grinding time when the shape of the grinding surface of the super-finished grindstone is polygonal than circular.

  FIG. 7 is a diagram showing the relationship between the surface to be ground and the ground surface. Referring to FIGS. 6 and 7, the grinding surface of the super-finished grindstone has a higher grinding efficiency than the circular shape. Is a circular truncated cone or a circumferential surface of the cone, the grinding by the ground grinding surface 47 is performed on the bus GE or a part of the bus GE of the surface 12 to be ground in a very short time. Since the super-finishing grindstone 11 is rotating, the grinding surface 46 which is a polygon has a contact length with the bus GE of the surface to be ground 12 (a length which contributes to grinding), for example, 1 when the grinding surface 46 is square. Changes from side length to diagonal length by rotation. Further, the angle at which the contour line of the grinding surface 46 intersects the generatrix GE of the surface to be ground 12 changes as the superfinishing grindstone 11 rotates.

As the superfinishing grindstone 11 rotates, the contact length between the grinding surface 46 and the surface 12 to be ground changes, and the angle at which the contour line of the grinding surface 46 intersects the generatrix GE of the surface 12 to be ground changes. It is speculated that either or both of these contribute to shortening the grinding time. This is consistent with the fact that the grinding surface 46 has a regular hexagonal shape rather than a circular shape, a regular pentagonal shape rather than a regular hexagonal shape, and a square shape shorter than a regular pentagonal shape.
Further, since the grinding by the grinding surface 47 which is a flat surface is performed on the bus GE or a part of the bus GE of the surface 12 to be ground, unnecessary falling abrasive grains that adversely affect the smoothness of the grinding surface are removed by grinding oil or The ease of removal with cooling water also contributes to shortening the search time.

Regarding the influence of the presence or absence of rotation of the superfinishing grindstone 11 on the grinding time, when the superfinishing grindstone 11 is rotated by stopping the rotation of the superfinishing grindstone 11 among the conditions shown in Table 1 Compared with. As a result, the grinding time required to set the average roughness Ra to 0.01 is 50 to 50 times longer when the superfinishing grindstone 11 is rotated than when the superfinishing grindstone 11 is not rotated. It was shortened to 30%.
Changing the rotational speed of the workpiece W according to the position of the grinding surface of the superfinishing grindstone 11 moving in the radial direction of the rotating workpiece W is not only shortening the grinding time but also the surface of the surface 12 to be ground. It is also effective for homogenizing roughness. The radius of rotation of the grinding surface of the superfinishing grindstone 11 on the surface to be ground 12 is changed by the movement of the superfinishing grindstone 11 when the grinding surface of the superfinishing grindstone 11 is moved. 11 moves, the relative speed (circumferential speed) between the grinding surface and the surface 12 to be ground also changes. For example, when the rotation speed of the workpiece W that is optimum for the surface roughness after grinding is set when the superfinishing grindstone 11 is at the outer moving end, the superfinishing grindstone 11 moves toward the inner moving end. As a result, it becomes deviated from grinding conditions (workpiece rotation speed) appropriate for the surface roughness after grinding. Therefore, in order to make the degree of grinding in the radial direction of the rotating workpiece W constant or higher, it is necessary to increase the overall grinding time.

  In addition, the superfinishing process utilizes the removal of the abrasive grains from the superfinishing grindstone 11 and the crushing of the abrasive grains, while the relative speed between the grinding surface and the surface to be ground 12 in the radial direction changes. As a result, the degree of removal and crushing of the abrasive grains changes. Therefore, in the mirror surface processing in which the surface roughness must be reduced as much as possible, the degree of the surface roughness after grinding may be different in the radial direction. Such a concern increases as the grinding surface 12 of the workpiece W increases. Therefore, when grinding a workpiece W having a large ground surface 12 for mirror finishing, the work is performed in accordance with the position of the superfinishing grindstone so that the peripheral speed of the portion to be ground of the ground surface 12 is not greatly changed. Changing the rotation of the object W is extremely effective for ensuring the quality of grinding and homogenizing the finished surface 12 to be ground.

In the above-described embodiment, the rotational speed of the workpiece W is changed so that the peripheral speed of the surface to be ground 12 that is in contact with the center of rotation of the grinding surface of the superfinishing grindstone 11 is constant. Even if the rotational speed of the workpiece W is arbitrarily reduced or increased in accordance with the increase or decrease in the rotational radius of the surface 12 to be ground, the same effect as changing the rotational speed based on the peripheral speed can be obtained. Instead of continuously changing the rotation speed of the workpiece W, the rotation speed may be changed stepwise every time the superfinishing grindstone 11 moves a certain distance.
Moreover, in the above-mentioned embodiment, although the rotation speed of the workpiece W was changed with the movement of the superfinishing grindstone 11, the rotation speed of the workpiece W was changed during the rough grinding process, the intermediate grinding process, and the finish grinding process. The value set for each may be constant. Even if it does so, the said effect by using the super finishing grindstone 11 with a polygonal grinding surface (a), and the said effect by grinding (b) rotating the super finishing whetstone 11 which vibrates are these. In both the cases where these are used alone and the cases where they are used in combination, the shortening of the grinding time is remarkable as compared with the case where these are not adopted.

In addition, the shape of the grinding surface of the superfinishing grindstone 11 does not need to be a regular polygon, and may be various rectangles or pentagons.
In superfinishing using the grinding apparatus 1, grinding may be performed without rotating the superfinishing grindstone 11 in the final finish grinding step. This is because, in consideration of the material and the like of the superfinishing grindstone 11 and the material of the workpiece W, the finish quality may be improved in the finish grinding process if the superfinishing grindstone 11 is not rotated.
In addition, each structure of the grinding apparatus 1 and the grinding apparatus 1 or the overall structure, shape, dimensions, number, material, and the like can be appropriately changed in accordance with the spirit of the present invention.

  The present invention can be used for a superfinishing method and a grinding apparatus for performing superfinishing.

FIG. 1 is a front view of a main part of a grinding apparatus for performing superfinishing. FIG. 2 is a side view of the grinding apparatus. FIG. 3 is a perspective view of the vicinity of the superfinishing grindstone in the grinding apparatus. FIG. 4 is a perspective view of the workpiece. FIG. 5 is a diagram showing the configuration of the control device. FIG. 6 is a diagram showing the movement of the superfinishing grindstone as viewed from the direction of arrows AA in FIG. FIG. 7 is a diagram showing the relationship between the surface to be ground and the ground surface.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Grinding device 2 Control device 3 Grinding wheel rotating device 5 Workpiece rotating device 6 Lateral movement device 7 Vibration imparting device 11 Superfinishing wheel 12 Surface to be ground 34 Control unit 43 Storage unit 46 Grinding surface W Workpiece

Claims (8)

Rotate a workpiece whose grinding surface is a frustoconical surface or a conical surface around the frustum or the cone axis;
Pressing the surface to be ground rotating while vibrating and rotating the superfinishing grindstone having a polygonal grinding surface,
Grinding is performed by reciprocating between the moving end set on the rotation center side of the surface to be ground and the moving end set on the outside side while the superfinishing grindstone is pressed against the surface to be ground. A superfinishing method characterized by that. The superfinishing method according to claim 1, wherein grinding is performed by increasing the rotational speed of the workpiece so that the position in the reciprocating movement of the superfinishing wheel is closer to the center of rotation of the surface to be ground. Grinding is performed by combining a plurality of grinding processes, each of which is different in the number of rotations of the workpiece, the frequency and the number of rotations of the superfinishing grindstone, the speed of reciprocating movement, and the number of reciprocating movements. The superfinishing method according to claim 1 or 2. The superfinishing processing method according to any one of claims 1 to 3, wherein a shape of a grinding surface of the superfinishing grindstone is a square. A workpiece rotating device for holding a workpiece whose grinding surface is a circumferential surface of a truncated cone or a circumferential surface of a cone and rotating the workpiece around an axis of the truncated cone or the cone;
A grindstone rotating device for holding and rotating a superfinishing grindstone having a polygonal grinding surface;
A vibration applying device for vibrating the superfinishing wheel;
A lateral movement device for moving the superfinishing wheel along the surface to be ground of the workpiece between the inner moving end and the outer moving end of the surface to be ground. To grind. The workpiece rotating device includes:
The grinding apparatus according to claim 5, wherein the number of rotations is configured to be increased or decreased in conjunction with movement of the superfinishing grindstone along the surface to be ground. The grinding device according to claim 5 or 6, wherein a shape of a grinding surface of the superfinishing grindstone is a square. Each setting of the rotational speed of the workpiece rotating device, the rotational speed of the grindstone rotating device, the vibration frequency of the vibration applying device, and the moving speed and the number of times of movement of the superfinishing grindstone by the lateral movement device A storage unit for storing values;
The workpiece rotating device, the grindstone rotating device, the vibration applying device, and the lateral movement device are controlled so as to continuously perform grinding under a plurality of grinding conditions in which any one or all of these set values are varied. A grinding device according to any one of claims 5 to 7, further comprising a control device having a control unit.