JP3608777B2 - Method for forming inner circumferential groove of sintered bearing - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method of forming an inner peripheral groove such as an oil groove or a middle escape portion on the inner peripheral surface of a cylindrical sintered bearing.
[0002]
[Prior art]
Conventionally, various methods for forming a dynamic pressure groove, a middle relief portion, and the like on the inner peripheral surface of a sintered bearing have been proposed. One of the methods that can be efficiently formed among them is as follows. There are many ways. That is, a core rod having a pattern corresponding to the groove to be formed (dynamic pressure groove or center escape portion) is inserted into the bearing material, the bearing material is compressed, and the inner circumferential surface thereof is the outer circumference of the core rod. The surface of the core rod is transferred to the inner peripheral surface of the bearing material by being in close contact with the surface, and then the bearing material is released from the compressed state. Pull out. Japanese Patent Application Laid-Open No. 2-107705 describes a method for forming a middle relief portion using such a method.
[0003]
[Problems to be solved by the invention]
In the above conventional method, in order to extract the bearing material having the inner circumferential groove from the core rod, the inner diameter of the bearing material is sufficiently expanded by the spring back, and the irregularities on both the outer circumferential surface of the core rod and the inner circumferential surface of the bearing material are uneven. It is required not to interfere with each other without meshing. For this reason, it is desirable that the material generates as much springback as possible. However, the spring back of a sintered alloy for general sliding bearings (the ratio of the inner diameter expansion amount of the bearing material when the compression to the outer diameter of the core rod is released) is about 0.2% at most. The uneven unevenness that can be formed on the inner peripheral surface of the plate is equal to the spring back amount at the maximum. In addition, some sintered bearings made of sintered alloys with relatively low density and sintered alloys that are relatively soft and easily plastically deformed, such as copper-based sintered alloys, have almost no springback. It is difficult to form an inner circumferential groove in a simple bearing material. Further, in the case of a bearing material mounted on the housing by means such as press fitting, naturally the spring back cannot be expected, and therefore the inner circumferential groove cannot be formed.
[0004]
Therefore, the present invention provides a method for forming an inner peripheral groove of a sintered bearing capable of reliably forming an inner peripheral groove even if the bearing material is one in which spring back does not occur or spring back cannot be expected. It is intended to provide.
[0005]
[Means for Solving the Problems]
The present invention inserts a core rod having a small diameter portion and a large diameter portion into a shaft hole of a cylindrical bearing material made of a sintered body, and vibrates the core rod or the bearing material in the radial direction while the large diameter portion of the core rod. The operation of striking the large-diameter portion of the core rod against the inner peripheral surface of the bearing material is caused to rotate over the entire peripheral area of the inner peripheral surface by pressing the inner peripheral surface of the bearing material.
[0006]
According to the present invention, when the above operation is performed, a part of the inner peripheral surface of the bearing material is hit and compressed by the large diameter portion of the core rod, and a part of the inner peripheral groove is formed. And an inner peripheral groove | channel is formed by performing this operation over the perimeter area of an inner peripheral surface. Since the bearing material is always partly compressed in the radial direction, the core rod has an outer diameter of the large diameter portion and an inner diameter of the small diameter portion (bearing surface) other than the inner circumferential groove on the inner peripheral surface of the bearing material. Equivalent or smaller diameters may be used. Thereby, a core rod can be extracted from a bearing raw material, without the large diameter part of a core rod interfering with a bearing surface. Therefore, the core rod can be reliably pulled out even if the bearing material does not cause spring back or cannot be expected to have spring back. That is, the inner circumferential groove can be reliably formed in such a bearing material, and the inner circumferential groove to be formed can be made deeper. In addition, for example, when the bearing material is inserted into the core rod in an interference fit state, and the bearing material has a slight spring back, the large diameter portion of the core rod may interfere with the bearing surface, The degree is very small, and the core rod can be extracted from the bearing material.
[0007]
In the present invention, while the core rod or the bearing material is vibrated in the radial direction, the large diameter portion of the core rod is pressed against the inner peripheral surface of the bearing material, and the frequency is from 50 Hz by an AC solenoid that can be easily obtained industrially. It is appropriately selected from about 60 kHz by the high frequency transmitter.
[0008]
Examples of the inner circumferential groove of the present invention formed on the inner circumferential surface of the bearing material by the large diameter portion of the core rod include, for example, an oil groove formed on the sliding bearing surface and serving as a lubricating oil reservoir and supply section, and both ends of the bearing. Examples thereof include a middle clearance portion that is sandwiched between sliding bearing surfaces formed on the portion and has a diameter larger than that of the sliding bearing surface and does not contact the rotating shaft.
[0009]
Further, the present invention includes a case where the bearing material is press-fitted into the housing. Naturally, no springback can be expected in the bearing material press-fitted into the housing, but in the present invention, an inner circumferential groove can also be formed on the inner circumferential surface of such a bearing material.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a partial cross-sectional front view of a processing apparatus that can suitably implement the inner circumferential groove forming method of the present invention, and FIG. 3 is a plan view of the apparatus. 1 and 3 is a base table, and guides extending in the front-rear direction (front and back direction in FIG. 1 and from bottom to top in FIG. 3) are provided at the left and right ends of the base table 1 in the figure. A shaft 2 is provided via a shaft support 3. A slide block 4 that is driven by driving means (not shown) is supported on the guide shafts 2 so as to be reciprocally movable along the guide shafts 2.
[0011]
As shown in FIG. 1, the slide block 4 is provided with a long left column 5 and a right short column 6, and a punch plate 7 is fixed horizontally to these columns 5 and 6. A cylindrical lower punch 8 extending vertically is fixed to a predetermined location on the punch plate 7. Above the punch plate 7, a platen 9 is fitted so as to be movable up and down around a long column 5. The platen 9 is moved up and down by a ram 11 provided in a hydraulic or pneumatic actuator 10 provided at the center on the slide block 4 so that the position of the ram 11 is controlled by a control means (not shown). It has become.
[0012]
A die housing 13 and a die plate 14 are arranged above the platen 9 with a spacer 12 mounted on the long column 5 interposed therebetween. The die housing 13 and the die plate 14 are fitted to the column 5 such that the die housing 13 and the die plate 14 can be turned in the horizontal direction about the column 5 and can be moved up and down via the spacer 12 as the platen 9 is moved up and down. . A short column 15 is erected on the right side of the platen 9 in FIG. 1, and the right end portion of the die plate 14 is placed on a cradle 16 fixed on the column 15. When the die plate 14 turns, the mounting portion of the die plate 14 slides on the cradle 16. The die housing 13 and the die plate 14 are turned by driving means (not shown).
[0013]
As shown in FIG. 1, a cylindrical die 17 is fitted in the die housing 13 and the die plate 14 so as to be rotatable about an axis. A die hole 17 a into which a workpiece (bearing material) W made of a cylindrical sintered body is fitted is formed in a portion of the die 17 fitted into the die plate 14. The lower punch 8 is coaxially inserted into the die 17 and its upper end can be inserted into the die hole 17a. In addition, the inner diameter of the portion below the die hole 17 a of the die 17 is sufficiently larger than the inner diameter of the die hole 17 a so as not to interfere with the lower punch 8. On the outer periphery of the lower end of the die 17, an annular gear 18 is fixed coaxially with the die 17.
[0014]
A motor 19 is accommodated on the right side of the die 17 in FIG. The motor 19 is fixed to the die housing 13 or the die plate 14, and a drive shaft 19a extending vertically is disposed at the lower end thereof. A pinion 20 is fixed to the drive shaft 19a. A belt 21 is wound around a gear 18 fixed to the pinion 20 and the die 17, and the drive of the motor 19 is transmitted to the die 17 so that the die 17 is It is designed to rotate.
[0015]
The above-described components mounted on the slide block 4 are reciprocated back and forth on the base table 1 together with the slide block 4. In the slide block 4, the retracted position shown in FIGS. 1 and 3 is the work set position, and the advanced position shown in FIGS. 2 and 4 is the work machining position.
[0016]
As shown in FIG. 1, a cylindrical upper punch 22 is disposed coaxially with the die hole 17a above the die plate 14 with the slide block 4 in the work set position. The upper punch 22 is moved up and down by an upper punch driving machine 23 such as a mechanical type, hydraulic type or pneumatic type shown in FIG. 3, and when lowered, the upper punch 22 fits into the die hole 17a and pushes the workpiece W into the die hole 17a.
[0017]
As shown in FIG. 2, a core rod 30 is disposed coaxially with the die hole 17a above the die plate 14 with the slide block 4 in the workpiece machining position. As shown in FIG. 3, the core rod 30 is suspended from the tip of a stay 41 that is connected to the vibrator 40 and extends forward and backward. The vibrator 40 receives a signal from a transmitter (not shown) and vibrates the core rod 30 in the front-rear direction. As the frequency, for example, 50 Hz using a solenoid, 40 kHz by ultrasonic vibration, or the like is appropriately selected.
[0018]
As shown in FIG. 6A, the core rod 30 is configured such that a large diameter portion 32 larger in diameter than the small diameter portion 31 is formed coaxially with the small diameter portion 31 on the distal end side of the small diameter portion 31 forming the main body. is there. The large-diameter portion 32 is a portion that forms a middle escape portion on the inner peripheral surface of the workpiece W and is shorter than the length of the workpiece W. By sufficiently pressing the large diameter portion 32 against the inner peripheral surface of the workpiece W, the bearing surfaces on both sides of the middle escape portion are pressed by the small diameter portions 31 on both sides of the large diameter portion 32. Further, a tapered portion 33 is formed at the tip of the core rod 30 for smooth insertion of the core rod 30 itself into the workpiece W. The large-diameter portion 32 of the core rod 30 is slightly smaller than the inner diameter of the workpiece W, and is set such that there is a gap between the large-diameter portion 32 and the large-diameter portion 32 inserted into the workpiece W. As for the size of the large-diameter portion 32, in addition to this, there is almost no gap between the large-diameter portion 32 and the inner peripheral surface of the workpiece W, or the interference fit is almost equal to or larger than the inner diameter of the workpiece W. Any of the dimensions that would result in In any case, a gap exists between the inner peripheral surface of the workpiece W and the small diameter portion 31 of the core rod 30.
[0019]
Next, the operation of the processing apparatus will be described. This operation is an application of the sizing method of the present invention, and can be automatically performed by a control means (not shown). First, as shown in FIGS. 1 and 3, the slide block 4 is stopped at the work set position. Then, as shown in FIG. 1, from the state where the upper end of the lower punch 8 is positioned below the die hole 17a, the workpiece W is pushed into the die hole 17a from above by the upper punch 22 to be fitted. Next, after raising the upper punch 22, the slide block 4 is advanced to the workpiece machining position as shown in FIG.
[0020]
Next, as shown in FIG. 2, the platen 9 is raised by the ram 11, whereby the core rod 30 is inserted into the axial hole W ₁ of the workpiece W, and the large-diameter portion 32 of the core rod 30 is placed in the center in the axial direction of the workpiece W. Position. Next, as shown in FIG. 5, the inner surface of the workpiece W is pressed against the large diameter portion 32 of the core rod 30 by slightly turning the die housing 13 and the die plate 14 forward (downward in FIG. 5). From this state, the vibrator 40 is operated to vibrate the core rod 30, and the work 19 is slowly rotated around the axis together with the die 17 by the motor 19.
[0021]
When the core rod 30 is vibrated in a state where the inner peripheral surface of the work W is in pressure contact with the large diameter portion 32 of the core rod 30, the inner peripheral surface of the work W at the press contact portion is struck by the large diameter portion 32 of the core rod 30, Compressed outward in the direction of plastic deformation. As a result, the inner peripheral surface is enlarged in diameter, and a part of the middle escape portion is formed. Then, as the workpiece W is rotated, the middle escape portion is gradually formed, and when the workpiece W is rotated once, the middle escape portion is formed over the entire circumferential area. Further, the inner peripheral surfaces on both sides of the middle escape portion are used as bearing surfaces when the small diameter portion 31 of the core rod 30 is in pressure contact. FIG. 6B shows a workpiece W machined according to the present embodiment, in which an intermediate escape portion 40 is formed at the axial center of the inner peripheral surface, and bearing surfaces 41 are formed on both sides thereof.
[0022]
In order to maintain the state in which the die housing 13 and the die plate 14 are swung so that the inner peripheral surface of the workpiece W is in pressure contact with the large diameter portion 32 of the core rod 30, a method of applying a constant load with a spring or the like is employed. be able to. In addition, the load that causes pressure contact can be lowered initially and gradually increased thereafter by a drive mechanism that rotates the die housing 13 and the die plate 14. Further, although the number of laps of the die 17 is at least one, it may be circulated a plurality of times, and is appropriately determined according to the material and density of the workpiece W and the depth of the intermediate escape portion to be formed.
[0023]
When the intermediate escape portion is formed, the vibrator 40 and the motor 19 are stopped, the die housing 13 and the die plate 14 are turned to their original positions, and then the die plate 14 is lowered together with the platen 9 to move the core rod 30 from the workpiece W. Extract. The lowering of the die plate 14 is continued, whereby the lower end surface of the workpiece W comes into contact with the lower punch 8, and further the lowering of the die plate 14 causes the workpiece W to be discharged from the die hole 17a and released. Thereafter, the slide block 4 is moved back to the work set position. The above is one cycle in which the intermediate escape portion is formed in the workpiece W.
[0024]
A method of forming the intermediate relief portion by the above processing apparatus is performed by hitting and compressing a part of the inner peripheral surface of the workpiece W by the large-diameter portion 32 of the core rod 30 having a diameter equal to or smaller than the inner diameter of the workpiece W. By moving while moving in the circumferential direction, the middle escape portion is formed over the entire circumference. For this reason, the core rod 30 can be extracted from the workpiece W without the large diameter portion 32 of the core rod 30 interfering with the bearing surfaces on both sides of the middle escape portion. As a result, the workpiece W is not spring-backed. Alternatively, even if the spring back cannot be expected, the intermediate escape portion can be formed reliably and efficiently.
[0025]
In the above embodiment, the middle relief portion is formed as the inner circumferential groove. However, it is possible to form a narrow annular oil groove or a plurality of such oil grooves by applying the present invention. In addition, the workpiece W can be a sintered body that has not been processed after sintering, or a sintered body that has been sized once, and in the same manner, such a sintered body is pressed into the housing. An inner peripheral groove such as a portion or an oil groove can also be formed. Further, a combination with a commonly used method for processing a sintered bearing, such as sizing after forming the inner peripheral groove by applying the present invention, can be appropriately performed according to the required bearing.
[0026]
【The invention's effect】
As described above, according to the present invention, the inner circumferential groove is formed by rotating the entire diameter of the operation of striking a part of the inner circumferential surface of the bearing material by the large diameter portion of the core rod and expanding the diameter. Even in the case of a bearing material that does not cause spring back or a bearing material that cannot be expected to have spring back, the inner circumferential groove can be formed reliably.
[Brief description of the drawings]
FIG. 1 is a processing apparatus that can suitably implement an inner circumferential groove forming method according to an embodiment of the present invention, and is a view taken along the line I-I of FIG.
FIG. 2 is a view taken along the line II-II in FIG.
FIG. 3 is a plan view of a processing apparatus that can suitably implement an inner circumferential groove forming method according to an embodiment of the present invention, with a slide block in a work set position.
FIG. 4 is a plan view showing a state in which the slide block of the apparatus is in a workpiece machining position.
FIG. 5 is a plan view showing a state in which a middle escape portion is formed by the apparatus.
6A is a side view of a core rod, and FIG. 6B is a longitudinal sectional view of a bearing material in which a middle escape portion is formed.
[Explanation of symbols]
30 ... Core rod 31 ... Small diameter part 32 ... Large diameter part 40 ... Middle escape part (inner peripheral groove)
W ... Workpiece (bearing)
W ₁ ... shaft hole

Claims (4)

A core rod having a small diameter portion and a large diameter portion is inserted into a shaft hole of a cylindrical bearing material made of a sintered body, and the large diameter portion of the core rod is made of the bearing material while vibrating the core rod or the bearing material in the radial direction. An inner circumferential groove of a sintered bearing characterized in that an operation of hitting the large diameter portion of the core rod against the inner circumferential surface of the bearing material by rotating against the inner circumferential surface is made to circulate over the entire circumferential area of the inner circumferential surface. Forming method. 2. The method for forming an inner peripheral groove of a sintered bearing according to claim 1, wherein a frequency at which the core rod or the bearing material is vibrated is selected from a range of 50 Hz to a high frequency region. The method for forming an inner peripheral groove of a sintered bearing according to claim 1, wherein the inner peripheral groove is an oil groove or a middle escape portion. The method for forming an inner peripheral groove of a sintered bearing according to claim 1, wherein the bearing material is press-fitted into a housing.

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