JPH0537403U - Rotating center for cylindrical grinder - Google Patents

Abstract

(57) [Abstract] [Purpose] As a spindle center or tailstock axis center of a cylindrical grinder, wear of the tip is less likely to occur during grinding,
(EN) Provided is a rotation center which can maintain high centering accuracy and exhibits excellent durability even when a heavy workpiece is to be machined. [Structure] A center main body 2 in which a head portion 5 having a pointed end is continuously provided at a front end of a shaft portion 4, and a holding cylinder 3 having a central hole 8 into which the shaft portion 4 is rotatably fitted in a circumferential direction. Central hole 8
A taper hole 8a is formed on the front side of the
For a cylindrical grinding machine in which a tapered peripheral surface portion 4a that fits into the tapered hole portion 8a is formed on the base side of the shaft portion 4, and lubricating oil is sealed in an interface gap 12 between the tapered hole portion 8a and the tapered outer peripheral portion 4a. Rotation center 1.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a rotary center that is preferably used as a spindle center and a tailstock shaft center of a cylindrical grinder that grinds the outer circumference of a work having a rotary body shape such as a round shaft shape or a cylindrical shape.

[0002]

[Prior Art]

 When grinding a workpiece with this type of grinder, each tip of the spindle center and tailstock shaft center is fitted into the center holes on both ends of the workpiece to hold the workpiece rotatably in the circumferential direction and to rotate the spindle side. The work is rotated by the drive plate, and the outer peripheral surface of the work is usually brought into contact with the rotating grindstone while being fed in the axial direction.

However, in this type of conventional grinding machine, generally, the rotation of the work during grinding is a maximum of about 200 rpm, which is a low speed. Therefore, from the viewpoint of immobilizing the shaft center and improving the grinding accuracy, Both of the above-mentioned centers are normally fixed to the headstock and tailstock and do not rotate.The tips of both centers and the center hole of the workpiece slide relative to each other during grinding. In order to reduce the above, lubricating oil is applied or supplied to the fitting part.

[0004]

[Problems to be solved by the device]

 However, in the above-mentioned conventional cylindrical grinder, as the centers and the workpiece slide relative to each other during the grinding process, it is inevitable that the wear of both the centers will progress as the machining is repeated. The unevenness is caused by the constant downward force, which gradually reduces the centering accuracy and thus the grinding accuracy. Especially when a heavy workpiece such as 10 kg or more is to be machined, the above wear will be severe and both centers will be damaged early. There was a problem that it was forced to replace it with a new one, leading to an increase in processing cost.

In a lathe or the like that requires high-speed rotation of a work, a rotary center that is rotatable via a bearing is also used as a spindle center or tailstock center to avoid frictional heat generation. However, in such a rotating center structure such as a lathe, since the bearing is interposed between the center outer circumference and the inner circumference of the mounting hole, there is a limit to the rotation accuracy, and even if the manufacturing accuracy is increased, it is 2-3 μm. It was inadequate for a cylindrical grinder that requires a high degree of roundness in finish grinding, inevitably causing a slight runout. As a special example, there is also known a structure in which the spindle center of a cylindrical grinder is integrally rotated together with the spindle. In this case, however, the runout of the spindle is transmitted to the workpiece as it is, so machining with high grinding accuracy is also required. Is not suitable for.

In view of the above situation, the present invention, as a spindle center or tailstock shaft center of a cylindrical grinder, is less likely to cause wear of a tip portion that supports a workpiece during grinding and has high centering accuracy. It is an object of the present invention to provide a rotary center that can be maintained permanently and exhibits excellent durability even when processing a heavy workpiece.

[0007]

[Means for Solving the Problems]

 The structure of the present invention for achieving the above object will be described with reference to the drawings, which correspond to the embodiments. A rotary center 1 for a cylindrical grinding machine according to claim 1 of the present invention comprises a front end of a shaft portion 4. A center body 2 in which a head portion 5 having a pointed end to be fitted into a center hole 21a on the end face of the work 21 is continuously provided, and a center hole 8 into which a shaft portion 4 of the center body 2 is rotatably mounted in the circumferential direction is held. A taper hole 8a is formed on the front side of the center hole 8 and has a diameter that is expanded forward, while a taper that is fitted to the taper hole 8a is formed on the base side of the shaft portion 4. A peripheral surface portion 4a is formed, and a lubricating oil 13 is sealed in an interface gap 12 between the tapered hole portion 8a and the tapered outer peripheral portion 4a.

According to a second aspect of the present invention, in the rotation center 1, the central hole 8 of the holding cylinder 3 has a straight hole portion 8b continuous with the tapered hole portion 8a, while the shaft portion 4 of the center body 2 is It has a straight portion 4b continuously fitted rearward from the tapered peripheral surface portion 4a and fitted into the straight hole portion 8b, and the outer periphery of the shaft portion 4 extending from the tapered peripheral surface portion 4a of the center body 2 to the straight portion 4b and the holding cylinder 3. A configuration is adopted in which a lubricating oil 13 is enclosed in an interface gap 12 with the inner circumference of the center hole 8.

[0009]

[Action]

 In the rotating center 1 according to claim 1, since the center body 2 is rotatably held by the holding cylinder 3, the holding cylinder 3 part is attached to the non-rotating main shaft or the tailing shaft of the cylindrical grinder like the conventional fixed center. The center body 2 is fitted and fitted in the center hole 21a of the work 21 to support the work 21 coaxially between the spindle 23 and the tailstock shaft 24, and the peripheral surface of the work 21 is ground. At this time, the holding cylinder 3 does not rotate, but the center main body 2 can rotate together with the work 21. Therefore, the contact portion between the tip of the center body 2 and the center hole 21a of the work 21 does not slide relative to each other during grinding, and the wear of the tip due to the sliding is avoided. At the sliding contact portion between the center body 2 and the holding cylinder 3, friction is remarkably reduced by the lubricating oil 13 sealed in the interface gap 12, and the work load is distributed to the sliding contact portion having a large area. Therefore, the rotation of the center main body 2 is made smooth and wear is less likely to occur.

Since the center body 2 and the holding cylinder 3 are fitted to each other by the tapered surfaces 4a and 8a that expand in diameter in the axially forward direction, the elastic force applied to the work 21 during grinding is 2 , 3 acts in the direction of deepening the fitting, so that the axes of the two are always kept in the same state during machining, and both 2 and 3 are in contact with each other by a metal surface that enables highly precise finishing. Therefore, the centering precision of both can be set to be extremely high, and a stable oil film can be formed even if the interfacial gap 12 is made extremely small and the amount of the lubricating oil 13 enclosed is extremely small.

According to the second aspect of the invention, the axial sliding contact length between the center body 2 and the holding cylinder 3 can be set to be long, so that the runout of the center body 2 during rotation can be further reduced, and The load of work weight per unit area applied to the contact portion is further reduced, and the smoothness of rotation of the center body 2 is further improved.

[0012]

【Example】

 FIG. 1 shows a rotary center 1 according to an embodiment of the present invention. The rotary center 1 is mainly composed of a center body 2 and a holding cylinder 3 which is fitted on the center body 2, and the front part has a tip. A triangular pyramid-shaped head portion 1a to be fitted into a center hole on the end face of the work is formed, and a rear portion thereof is a taper shank portion 1b to be fitted and fixed to a non-rotating main shaft or a tailstock shaft of a cylindrical grinding machine.

In the center body 2, a head 5 which is a triangular pyramid having a larger maximum diameter and constitutes the front half of the head 1 a is continuously provided at the front end of the shaft portion 4, and the base of the shaft portion 4 is formed. An annular step portion 5a is provided between the portion and the maximum diameter portion of the head portion 5. The shaft part 4 is composed of three parts, a tapered peripheral surface part 4a, a straight part 4b, and a small-diameter part 4c, the diameters of which are successively reduced from the front side, that is, the root side, and the O-ring is provided near the rear part of the straight part 4b. 6a is fitted, and a male screw 7 is engraved on the peripheral surface of the small diameter portion 4c near the rear portion.

On the other hand, the holding tube 3 has the same outer diameter as the maximum diameter of the head portion 5 of the center body 2 and the latter half of the head portion 1a at the front end of the taper tube portion 3a forming the outside of the taper shank portion 1b. A large outer diameter portion 3b forming a portion is formed, a central hole 8 extending over the entire length thereof is formed, and the front end face is recessed in two steps. The central hole 8 has a taper hole portion 8a, which gradually expands in the forward direction at the same inclination as the taper peripheral surface portion 4a, a straight hole portion 8b having substantially the same diameter as the straight portion 4b, and the thin shaft portion. 4c has a small diameter hole 8c which is slightly larger than 4c, and a rear end hole 8d which is even larger than 4c. The tapered hole 8a and the straight hole 8b are formed on the shaft 4 of the center body 2. Precisely dimensioned to ensure a proper fit with a very small interface gap of less than μm.

When assembling the rotation center 1, the shaft portion 4 of the center body 2 is inserted into the center hole 8 of the holding cylinder 3 from the front side. At the time of this insertion, the annular step portion of the center body 2 is inserted. Of the annular spaces 9a and 9b formed between the 5a and the front end surface of the holding cylinder 3 which is recessed in two steps, a seal ring 10 is provided in the outer annular space 9a and a needle roller type thrust is provided in the inner annular space 9b. Bearings 11 are respectively loaded, and lubricating oil 13 as shown in FIG. 2 is sealed in an interface gap 12 between the shaft portion 4 and the central hole 8 extending from the seal ring 10 to the O ring 6a. Next, the pressing ring 16 is fitted to the shaft portion 4 inserted in the center hole 8 from the rear end side through the ball-type thrust bearing 15, and the nut 16 is screwed into the male screw 7 for tightening. Further, the rotary center 1 is completed by fitting the plug body 17 fitted with the O-ring 6b to the rear end side of the central hole 8. Reference numeral 18 denotes an annular oil reservoir formed at the boundary between the tapered portion and the straight portion of the interface gap 12.

In the rotation center 1 having the above-mentioned configuration, the center body 2 is held by the holding ring 15 and the nut 16 in the holding cylinder 3 so as not to be pulled out, and in this state, the center body 2 is sealed in the interface gap 12 with respect to the holding cylinder 3. The relative rotation can be smoothly performed via the lubricating oil 13 and the thrust bearings 11 and 14. A needle type thrust bearing 11 suitable for a high load is used for the thrust portion on the front side of the center body 2 and the holding cylinder 3 because the work is clamped in a repulsive pressure state during grinding with a cylindrical grinder. This is because the elastic body receives a load in the direction to push the center body 2 toward the holding cylinder 3 side.

In FIG. 3, the rotary center 1 having the above-mentioned configuration is used for both the center of the headstock 19 and tailstock 20 of the cylindrical grinder, and the peripheral surface of the work 21 having a round shaft is ground by the rotary grindstone 22. Indicates the state. Then, the rotary center 1 is attached to the non-rotating main shaft 23 and tailstock shaft 24 by inserting and fixing the shank portion 1b into the respective mounting holes 23a and 24a, like the conventional fixed center. By fitting the pointed end of the head portion 1a into the center hole 21a of the end face of the work 21, the work 21 is supported coaxially between the main shaft 23 and the tailstock shaft 24 at both end axes.

A rotary drive plate 25 is rotatably fitted to a front end portion of a main shaft 23 of a main shaft stock 19 via a bearing 26, and is rotated by a drive shaft 27 externally fitted to the main shaft 23. A drive pin 28 is projectingly provided on the outer peripheral portion of the front surface. Then, a ring-shaped break 29 is fitted on the main shaft side of the work 21, and the work 21 is integrally gripped from three directions by two bolts 29a and a pressing lever (not shown) attached to the work 29 and attached. It is connected to the drive pin 28 by a rod 29b. The tailstock shaft 24 is always elastically urged forward by a spring member (not shown).

When the rotary drive plate 25 is rotationally driven by the drive shaft 27, the work 21 also integrally rotates via the break 29, so that the rotary grindstone 22 is brought into contact with the peripheral surface of the work 21. The required grinding process can be performed.

During this grinding process, the holding cylinder 3 of each rotary center 1 does not rotate, but the center body 2 rotates integrally with the work 21, so that the tip of the head portion 1 a contacts the center hole 21 a of the work 21. The parts do not slide relative to each other, and wear of the contact part due to the relative sliding does not occur. Further, as described above, the center body 2 and the holding cylinder 3 are fitted with each other by the tapered surface that expands in the axially forward direction, so that the spring force of the tailstock shaft 24 causes the elastic force to be applied to the front side. The center body 2 is constantly pressed in a direction to deepen the fitting with the holding cylinder 3, and the metal surfaces 2 and 3 that are highly precision finished are in sliding contact with each other over a long axial distance. The mutual axis centers are always exactly aligned and the runout is maintained, and the sliding contact areas of both 2 and 3 have a small friction resistance due to the strong lubricating oil film, and the load due to the work weight per unit area. The small size makes it less likely to wear. Therefore, the centering accuracy of the workpiece 21 becomes extremely high, the rotation center 1 has a long life, and even if the workpiece 21 to be machined has a large weight of, for example, 10 kg or more, highly accurate grinding can be performed repeatedly over a long period of time.

[0021]

[Effect of the device]

 As described above, according to the rotation center of claim 1 of the present invention, wear of the tip supporting the work is less likely to occur during the grinding process with the cylindrical grinder, and high centering accuracy is maintained. It has the advantages that it can be maintained and can perform highly accurate grinding over a long period of time, especially when targeting heavy workpieces, and it can be used as it is by replacing it with the fixed center of an existing cylindrical grinder.

According to the rotation center of the second aspect, since the sliding contact length in the axial direction between the center body and the holding cylinder can be set to be long, it is possible to further reduce the runout of the center body during rotation, and at the sliding contact portion. The load of the work weight per unit area can be further reduced, and the smoothness of rotation of the center main body 2 and the durability of the center as a whole can be further improved.

[Brief description of drawings]

FIG. 1 is a half sectional side view of a rotation center according to an embodiment of the present invention.

FIG. 2 is an enlarged view of a virtual circle A in FIG.

FIG. 3 is a vertical cross-sectional view of a main part showing a grinding processing state by a cylindrical grinding machine using the same rotation center.

[Explanation of symbols]

 1 Rotation Center 2 Center Body 3 Holding Cylinder 4 Shaft Part 4a Tapered Peripheral Surface Part 4b Straight Part 5 Head Part 8 Center Hole 8a Tapered Hole Part 8b Straight Hole Part 12 Interface Gap 13 Lubricating Oil 21 Workpiece 21a Center Hole

Claims (2)

[Scope of utility model registration request] 1. A center body in which a head having a pointed end to be fitted into a center hole of a work end face is connected to the front end of the shaft portion, and a center hole into which the shaft portion of the center body is rotatably fitted in the circumferential direction. And a tapered peripheral surface portion that fits properly into the tapered hole portion is formed on the root side of the shaft portion. ,
A rotary center for a cylindrical grinder in which lubricating oil is filled in an interface gap between the tapered hole portion and the tapered peripheral surface portion. 2. A straight portion, in which a central hole of a holding cylinder has a straight hole portion continuous with a tapered hole portion, and a shaft portion of a center body is continuously fitted rearward from a tapered peripheral surface portion into the straight hole portion. 2. The rotary center for a cylindrical grinding machine according to claim 1, further comprising a lubricating oil filled in an interface gap between an outer circumference of the shaft portion extending from the tapered peripheral surface portion of the center body to a straight portion and an inner circumference of the center hole of the holding cylinder.