JP2012016803A - Method and device for shot peening, and coil spring - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for shot peening which has a simple device configuration, whose costs for installing and maintenance of devices are reduced, and which can perform shot peening treatment to both radial sides of a coil spring.SOLUTION: The method for shot peening includes: a reflection member arranging step of arranging a reflection member having a reflection surface therein so as to cover the wholly axial length of the coil spring from the radially outer side; and a treatment step of inserting a nozzle into the radially inner side of the coil spring, blasting a shot from the nozzle by an airflow toward the radially outer side while moving the nozzle in the axial direction and also rotating the nozzle about the axis, thereby applying the shot peening treatment to the coil spring by the shot from the radially inner side and also applying the shot peening treatment to the coil spring by the shot reflected on the reflection surface from the radially outer side.

Description

  The present invention relates to a shot peening method for performing shot peening on a coil spring, a shot peening apparatus, and a coil spring subjected to shot peening.

  The coil spring is subjected to shot peening mainly to improve durability. Examples of the shot peening device for the coil spring include a nozzle type shot peening device and an impeller type shot peening device. Of these, in the case of a nozzle-type shot peening apparatus, an air flow (air compressor) is used for shot conveyance. For this reason, the energy cost required to secure the air flow is expensive. Therefore, conventionally, an impeller type shot peening apparatus has been mainstream.

  The impeller-type shot peening apparatus includes an impeller. The impeller is arranged outside the coil spring (outside in the axial direction and radially outside). The shot is fired by the centrifugal force of the rotating impeller.

  However, according to the impeller-type shot peening apparatus, a large impeller is required as compared with the size of the coil spring. For this reason, a shot peening apparatus will enlarge.

  Further, according to the impeller-type shot peening apparatus, the shot firing range is wider than the size of the coil spring. For this reason, the number of shots effective for shot peening of the coil spring is small with respect to the total number of shots. That is, the processing efficiency is low. In addition, the shot collides with a portion other than the coil spring that does not originally need to be shot, specifically, a part of the shot peening apparatus. For this reason, the maintenance cost of a shot peening apparatus becomes high.

  Further, when the coil spring is used, a higher stress is more likely to act on the radially inner portion than on the radially outer portion. However, according to the impeller-type shot peening apparatus, a shot can be fired on the coil spring only from the outside in the radial direction. For this reason, it is difficult to perform shot peening on the radially inner portion of the coil spring for which the compressive residual stress is to be increased.

  In this regard, Patent Document 1 discloses a nozzle-type shot peening apparatus. The shot peening apparatus of the same document includes a pair of nozzles. One nozzle is arrange | positioned at the radial inside of a coil spring. The other nozzle is arranged on the radially outer side of the coil spring. From each of the pair of nozzles, shots are fired by an air flow.

  The nozzle of the shot peening apparatus of the same document is small. For this reason, a shot peening apparatus does not enlarge. Further, according to the shot peening apparatus of the same document, the shot firing range is narrow. For this reason, processing efficiency is high. Further, it is difficult for the shot to collide with the parts of the shot peening apparatus. For this reason, the maintenance cost of the shot peening apparatus is low. Moreover, it is easy to perform shot peening not only on the radially outer part of the coil spring but also on the radially inner part.

Japanese Patent Laid-Open No. 53-60794

  However, according to the shot peening apparatus of the same document, two nozzles are necessary on both sides in the radial direction of the coil spring. For this reason, piping for connecting the air supply device (compressor, etc.) and the nozzle, a device for adjusting the shot firing speed, that is, the speed of the air flow, and its control device, the nozzle drive device and its control device, all need two systems. Become. Therefore, according to the shot peening apparatus of the same document, the apparatus configuration becomes complicated both mechanically and electrically. In addition, the installation cost of the device is increased accordingly.

  Further, when shots are fired from both radial sides of the coil spring using two nozzles, the shots fired from the radially inner nozzle directly collide with the radially outer nozzle. Similarly, a shot fired from a radially outer nozzle directly collides with a radially inner nozzle. For this reason, the nozzle tends to deteriorate. Therefore, in this respect, the maintenance cost of the shot peening apparatus is increased. In particular, when two nozzles on both sides in the radial direction are moved synchronously, the shot is more likely to collide with the nozzles.

  The shot peening method, the shot peening apparatus and the coil spring of the present invention have been completed in view of the above problems. It is an object of the present invention to provide a shot peening method and a shot peening apparatus that have a simple apparatus configuration, low apparatus installation costs and low maintenance costs, and can perform shot peening on both radial side portions of a coil spring. . In addition, an object of the present invention is to provide a coil spring in which shot peening is applied to both side portions in the radial direction.

  (1) In order to solve the above problem, the shot peening method of the present invention includes a reflecting member arranging step of arranging a reflecting member having a reflecting surface on the inside so as to cover the entire axial length of the coil spring from the radially outer side, A nozzle is inserted inside the coil spring in the radial direction, and while moving the nozzle in the axial direction and rotating around the axis, a shot is shot from the nozzle toward the outside in the radial direction by an air flow. And a process step of performing shot peening on the coil spring from the outside in the radial direction by the shot reflected by the reflecting surface from the inside. Correspondence).

  Here, “moving the nozzle in the axial direction” includes not only moving the nozzle linearly but also moving the nozzle spirally.

  According to the shot peening method of the present invention, the nozzle is disposed on the radially inner side of the coil spring, and the reflecting surface of the reflecting member is disposed on the radially outer side. A part of the shot fired from the nozzle collides with the coil spring from the radially inner side. For this reason, shot peening can be applied to the radially inner portion of the coil spring. That is, it is possible to impart plastic deformation to the radially inner portion of the coil spring and improve the compressive residual stress.

  On the other hand, the other part of the shot fired from the nozzle passes through the gap between the wire rods of the coil spring, collides with the reflecting surface and bounces back. The bounced shot collides with the coil spring from the outside in the radial direction. For this reason, shot peening can be applied to the radially outer portion of the coil spring. That is, it is possible to give plastic deformation to the radially outer portion of the coil spring and improve the compressive residual stress. Thus, according to the shot peening method of the present invention, it is possible to improve the compressive residual stress at both side portions in the radial direction. For this reason, the durability of the coil spring can be improved.

  Moreover, according to the shot peening method of the present invention, the nozzle is smaller as it enters the radial inside of the coil spring. Therefore, the shot peening apparatus does not increase in size. In addition, the shot firing range can be narrowed compared to the case where an impeller-type shot peening apparatus is used. For this reason, the number of shots effective for shot peening of the coil spring is large with respect to the total number of shots. That is, the processing efficiency is high. Further, it is difficult for the shot to collide with the parts of the shot peening apparatus. For this reason, the maintenance cost of the shot peening apparatus is low.

  Further, according to the shot peening method of the present invention, the nozzle is disposed only on the radially inner side of the coil spring. For this reason, the piping connecting the gas supply device and the nozzle, the device for adjusting the shot firing speed, that is, the air velocity, and its control device, the nozzle drive device and its control device, all need only one system. Therefore, the apparatus configuration is simplified both mechanically and electrically. In addition, the installation cost of the apparatus is reduced accordingly.

  Further, according to the shot peening method of the present invention, the collision with the coil spring from the outside in the radial direction is a shot that has bounced back to the reflecting surface at least once. For this reason, the speed, that is, the kinetic energy of the shot that collides with the coil spring from the radially inner side is inevitably higher than the shot that collides with the coil spring from the radially outer side. Therefore, the compressive residual stress in the radially inner portion of the coil spring tends to be larger than the compressive residual stress in the radially outer portion of the coil spring. As described above, according to the shot peening method of the present invention, it is easy to generate a larger compressive residual stress in the radially inner portion of the coil spring where high stress is likely to be applied during use compared to the radially outer portion. When the compressive residual stress at the radially inner portion of the coil spring is saturated, the compressive residual stress at both radial portions may be equal.

  Further, according to the shot peening method of the present invention, even if the shot collides with the nozzle, it is fired from the radially inner nozzle and bounced off by the reflecting surface of the reflecting member or the coil spring. It is a shot. In other words, it is a shot in which the kinetic energy is attenuated by reflection. For this reason, the nozzle is unlikely to deteriorate. Therefore, the maintenance cost of the shot peening apparatus is low.

  Incidentally, the ratio of the compressive residual stress in the radially inner portion of the coil spring to the compressive residual stress in the radially outer portion (hereinafter referred to as “stress ratio” as appropriate) is the entire coil spring (axial and circumferential). (Direction) is preferably constant. In this regard, according to the shot peening method of the present invention, what hits the radially outer portion of the coil spring is a shot fired from the radially inner nozzle and bounced off the reflecting surface of the reflecting member. Moreover, the reflection member is arrange | positioned so that the axial direction full length of a coil spring may be covered from a radial direction outer side. For this reason, the stress ratio is unlikely to vary over the entire coil spring regardless of the movement of the nozzle, the number of shots, the speed, and the like.

  (1-1) Preferably, in the configuration of the above (1), in the processing step, the nozzle may be rotated about the axis while moving linearly in the axial direction. This configuration is effective when the inner diameter of the coil spring is smaller than the outer diameter of the nozzle.

  (1-2) Preferably, in the configuration of (1) above, in the processing step, the nozzle is rotated around the axis while being screwed. This configuration is effective when the inner diameter of the coil spring is larger than the outer diameter of the nozzle.

  (1-3) Preferably, in the configuration of (1) above, in the processing step, the airflow is preferably supplied by a blower. According to this configuration, the energy cost required to secure the airflow is lower than when the airflow is supplied by an air compressor. For this reason, energy efficiency becomes high.

  (2) Moreover, in order to solve the said subject, the shot peening apparatus of this invention is arrange | positioned so that the axial direction full length of a coil spring may be covered from a radial direction outer side, a reflection member which has a reflective surface inside, and this coil spring A nozzle that fires a shot toward the outside in the radial direction by an air flow while moving in the axial direction and rotating around the axis, and is applied to the coil spring from the inside in the radial direction by the shot. In addition to performing shot peening, shot peening is performed on the coil spring from outside in the radial direction by the shot reflected by the reflecting surface (corresponding to claim 2).

  As described in (1) above, according to the shot peening apparatus of the present invention, plastic deformation can be applied to both side portions in the radial direction of the coil spring to improve the compressive residual stress. For this reason, the durability of the coil spring can be improved.

  Moreover, according to the shot peening apparatus of the present invention, since the nozzle is small, the shot peening apparatus does not increase in size. Further, since the shot firing range can be narrowed, the processing efficiency is high. In addition, since shots hardly collide with parts of the shot peening apparatus, the maintenance cost of the shot peening apparatus is low.

  Moreover, according to the shot peening apparatus of the present invention, the nozzle is disposed only on the radially inner side of the coil spring. This simplifies the apparatus configuration both mechanically and electrically. In addition, the installation cost of the apparatus is reduced accordingly.

  In addition, according to the shot peening apparatus of the present invention, it is easy to generate a larger compressive residual stress in the radially inner portion of the coil spring where high stress is likely to be applied during use than in the radially outer portion. Further, according to the shot peening apparatus of the present invention, the stress ratio is less likely to vary over the entire coil spring regardless of the movement of the nozzle, the number of shots, the speed, and the like. Further, according to the shot peening apparatus of the present invention, the nozzle is not easily deteriorated. Therefore, the maintenance cost of the shot peening apparatus is low.

  (2-1) Preferably, in the configuration of the above (2), when the shot is fired, the nozzle moves linearly in the axial direction and rotates around the axis. This configuration is effective when the inner diameter of the coil spring is smaller than the outer diameter of the nozzle.

  (2-2) Preferably, in the configuration of the above (2), the nozzle is configured to be screwed and rotated around an axis when firing the shot. This configuration is effective when the inner diameter of the coil spring is larger than the outer diameter of the nozzle.

  (2-3) Preferably, in the configuration of (2) above, in the processing step, the airflow is preferably supplied by a blower. According to this configuration, the energy cost required to secure the airflow is lower than when the airflow is supplied by an air compressor. For this reason, energy efficiency becomes high.

  (3) Preferably, in the configuration of the above (2), the reflection member has a nozzle insertion hole into which the nozzle is inserted from the outside, and the inner surface of the reflection member is accommodated radially inside. It is better to have a structure including a table on which the coil spring is disposed, and a cover disposed on the inner surface of the table so that the entire axial length of the coil spring is accommodated radially inside ( Corresponding to claim 3).

  According to this configuration, the coil spring can be taken in and out of the reflecting member by detaching the cover from the table. For this reason, taking in and out of the coil spring is easy. Further, when the coil spring is set on the table, the coil spring can be arranged with the nozzle insertion hole as a guide. For this reason, positioning of a coil spring is easy.

  (4) In order to solve the above problem, the coil spring of the present invention is shot peened so that the compressive residual stress in the radially inner portion is equal to or greater than the compressive residual stress in the radially outer portion. (Corresponding to claim 4).

  Here, the “radially inner portion” of the coil spring is a portion that is exposed to light when the coil spring is irradiated with light from the radially inner side perpendicular to the axial direction. Further, the “radially outer portion” is a portion that is exposed to light when the coil spring is irradiated with light from the radially outer side perpendicular to the axial direction. For example, when the cross section of the wire rod of the coil spring is a substantially circular shape, the radially inner portion is the radial direction of the coil spring with respect to an imaginary line parallel to the axial direction drawn through the center of the cross section. The inner part. The radially outer portion is the radially outer portion of the coil spring.

  Higher stress is more likely to act on the radially inner portion of the coil spring during use than on the radially outer portion. In this regard, according to the coil spring of the present invention, the compressive residual stress in the radially inner portion is set to be greater than the compressive residual stress in the radially outer portion. For this reason, durability can be improved. According to the shot peening method (1) and the shot peening apparatus (2) or (3), the coil spring of the present invention can be easily manufactured.

  According to the present invention, the apparatus configuration is simple, the installation cost and the maintenance cost of the apparatus are low, shot peening can be performed on both sides in the radial direction of the coil spring, and the stress ratio is less likely to vary over the entire coil spring. A peening method and a shot peening apparatus can be provided. In addition, according to the present invention, it is possible to provide a coil spring in which shot peening is performed on both radial side portions.

It is a perspective view of the shot peening apparatus of a first embodiment. It is a disassembled transmission perspective view of the same shot peening apparatus. It is an axial sectional view of the same shot peening apparatus. It is a schematic diagram of the compressive residual stress distribution of the axial direction of the coil spring of 1st embodiment. It is a schematic diagram of the compressive residual stress distribution of the circumferential direction of the coil spring. It is a perspective view of the shot peening apparatus of 2nd embodiment. It is radial direction sectional drawing of the shot peening apparatus of 3rd embodiment. It is an axial sectional view of a nozzle of a shot peening apparatus of a fourth embodiment. It is axial direction sectional drawing of the shot peening apparatus of 5th embodiment.

  Hereinafter, embodiments of a shot peening method, a shot peening apparatus, and a coil spring according to the present invention will be described.

<First embodiment>
[Shot peening equipment]
First, the shot peening apparatus of this embodiment will be described. In FIG. 1, the perspective view of the shot peening apparatus of this embodiment is shown. FIG. 2 shows an exploded transparent perspective view of the shot peening apparatus. FIG. 3 shows an axial sectional view of the shot peening apparatus.

  As shown in FIGS. 1 to 3, the shot peening apparatus 1 includes a reflecting member 2 and a nozzle 3. The reflecting member 2 includes a table 20 and a cover 21. The table 20 is made of steel and has a plate shape. The table 20 includes a nozzle insertion hole 200, a number of exhaust holes 201, a reflective surface 202, and a mounting boss 203. The nozzle insertion hole 200 and the exhaust hole 201 penetrate the table 20 in the vertical direction. A large number of exhaust holes 201 are arranged radially around the nozzle insertion hole 200. The mounting boss 203 protrudes from the upper surface (inner surface) of the table 20. The mounting boss 203 is disposed around the nozzle insertion hole 200. The reflective surface 202 is disposed on the upper surface of the table 20. The reflection surface 202 has a planar shape. The reflective surface 202 is disposed around the nozzle insertion hole 200. The reflective surface 202 corresponds to a portion of the upper surface of the table 20 that is covered by the cover 21 described later. The coil spring C is erected on the upper surface of the table 20 so that its axial direction is aligned in the vertical direction. The lower end of the coil spring C is attached to the mounting boss 203 so as to be detachable. That is, the coil spring C is disposed around the nozzle insertion hole 200.

  The nozzle 3 is disposed so as to be able to enter and exit in the radial direction of the coil spring C through the nozzle insertion hole 200. The nozzle 3 can move linearly in the vertical direction (axial direction). The nozzle 3 is rotatable around the axis. The nozzle 3 includes a shot supply passage 30. The shot supply passage 30 is disposed at the radial center of the nozzle 3. The shot supply passage 30 extends in the vertical direction. The upper end of the shot supply passage 30 is bifurcated with a convex portion 301 having a triangular cross section as a boundary. Two shot launch ports 300 are arranged at the branch end (downstream end) of the shot supply passage 30. The two shot launch ports 300 are 180 ° apart and open on the outer peripheral surface of the upper end of the nozzle 3. As schematically shown in FIG. 3, an air supply blower 90 is disposed at the upstream end of the shot supply passage 30. A hopper 92 for feeding shot S is branched and connected to the downstream side of the blower 90 via a loading amount adjusting valve 91.

  The shot S is supplied from the hopper 92 to the shot supply passage 30. The supplied shot S rides on the air flow supplied from the blower 90, passes through the shot supply passage 30, and is fired radially outward from the shot launch port 300.

  The cover 21 is made of steel and has a bottomed cylindrical shape (cup shape) that opens downward. The cover 21 is laid on the upper surface of the table 20. The cover 21 is detachably fixed to the upper surface of the table 20 by an engagement mechanism (not shown). The cover 21 covers the coil spring C, the nozzle insertion hole 200, and the numerous exhaust holes 201 from above. The cover 21 includes a reflective surface 210. The reflective surface 210 is disposed on the inner peripheral surface and the upper bottom surface of the cover 21. The inner peripheral surface portion of the reflection surface 210 has a curved surface shape (cylindrical back surface shape). The upper bottom surface portion of the reflection surface 210 has a planar shape. Thus, the coil spring C is accommodated in the closed space defined by the reflecting surfaces 202 and 210 by the cover 21 being laid down on the table 20.

[Shot peening method]
Next, the shot peening method of this embodiment will be described. The shot peening method of the present embodiment includes a reflecting member arranging step and a processing step.

  In the reflection member arranging step, first, the coil spring C is attached to the attachment boss 203. Next, the cover 21 is laid on the table 20 from above the coil spring C. Then, the cover 21 is fixed to the table 20 by the engagement mechanism.

  In the processing step, the nozzle 3 is rotated around the axis while moving the nozzle 3 in a vertical direction in a predetermined operation pattern. In addition, the shot S is fired from the shot launch port 300 toward the radially outer side. As schematically shown in FIG. 3, a portion of the shot S that has fired collides with the radially inner portion of the coil spring C. Further, the other part of the shot S that has been fired passes through the gap between the wire rods of the coil spring C, collides with the reflecting surfaces 210 and 202 and bounces back. The bounced shot S collides with the radially outer portion of the coil spring C. The shot S and air fired from the shot launch port 300 flow down to the lower side of the table 20 through the numerous exhaust holes 201. The shot S after use is collected by a shot collection device (not shown).

[Coil spring]
Next, the coil spring of this embodiment will be described. In FIG. 4, the schematic diagram of the compressive residual stress distribution of the axial direction of the coil spring of this embodiment is shown. FIG. 5 shows a schematic diagram of the distribution of compressive residual stress in the circumferential direction of the coil spring.

  As shown in FIGS. 4 and 5, the compressive residual stress distribution of the coil spring C after the shot peening is substantially constant over the entire axial direction and the entire circumferential direction in both the radially inner portion and the radially outer portion. It is. Further, the compressive residual stress is higher in the radially inner portion than in the radially outer portion. The stress ratio is also substantially constant over the entire axial direction and the entire circumferential direction.

[Function and effect]
Next, the effects of the shot peening method, the shot peening apparatus, and the coil spring of this embodiment will be described. According to the shot peening method and the shot peening apparatus 1 of the present embodiment, the nozzle 3 is disposed on the radially inner side of the coil spring C, and the inner peripheral surface portion of the reflecting surface 210 is disposed on the radially outer side. For this reason, shot peening can be applied to both radial side portions of the coil spring C. That is, it is possible to impart plastic deformation to both side portions in the radial direction of the coil spring C and improve the compressive residual stress. Therefore, the durability of the coil spring C can be improved.

  Further, an upper bottom surface portion of the reflecting surface 210 is disposed above the coil spring C, and a reflecting surface 202 is disposed below the coil spring C. Shots S bounced off by these reflecting surfaces 210 and 202 can also be used to improve the compressive residual stress of the coil spring C.

  Further, according to the shot peening method and the shot peening apparatus 1 of the present embodiment, the nozzle 3 is smaller as it enters the radial direction inner side of the coil spring C. Therefore, the shot peening apparatus 1 does not increase in size. Further, the shot S can be fired in a narrower range as compared with the impeller type shot peening apparatus. For this reason, processing efficiency is high. Further, the shot S hardly collides with the parts of the shot peening apparatus 1 (excluding the reflection surfaces 210 and 202). For this reason, the maintenance cost of the shot peening apparatus 1 is low.

  Moreover, according to the shot peening method and the shot peening apparatus 1 of the present embodiment, the nozzle 3 is disposed only on the radially inner side of the coil spring C. For this reason, the shot supply passage 30, the blower 90 and its control device, the input amount adjusting valve 91 and its control device, the hopper 92, the nozzle 3 driving device and its control device, etc. are all in one system. Therefore, the apparatus configuration is simplified both mechanically and electrically. In addition, the installation cost of the apparatus is reduced accordingly.

  Moreover, according to the shot peening method and the shot peening apparatus 1 of the present embodiment, the shot S that rebounds on the reflection surfaces 210 and 202 hits the coil spring C from the outside in the radial direction at least once. For this reason, the shot S that collides with the coil spring C from the radially inner side necessarily has a higher speed, that is, kinetic energy, than the shot S that collides with the coil spring C from the radially outer side. Therefore, the compressive residual stress in the radially inner portion of the coil spring C tends to be larger than the compressive residual stress in the radially outer portion of the coil spring C. Thus, according to the shot peening method and the shot peening apparatus 1 of the present embodiment, a larger compressive residual is provided in the radially inner portion of the coil spring C where high stress is likely to be applied during use than in the radially outer portion. It is easy to generate stress.

  Further, according to the shot peening method and the shot peening apparatus 1 of the present embodiment, the collision with the radially outer portion of the coil spring C is launched from the radially inner nozzle 3 and is reflected by the reflecting surfaces 210 and 202 of the reflecting member. It is a shot S that bounces back. Moreover, the reflection member 2 is arrange | positioned so that the whole coil spring C may be covered. For this reason, the stress ratio is unlikely to vary over the entire coil spring C regardless of the movement of the nozzle 3, the number of shots S, the speed, and the like.

  Further, according to the shot peening method and the shot peening apparatus 1 of the present embodiment, even if the shot S collides with the nozzle 3, the collision is fired from the radially inner nozzle 3 and the reflecting member 2. The shot S is bounced back by the reflecting surfaces 210 and 202 or the coil spring C. In other words, the shot S has kinetic energy attenuated by reflection. For this reason, the nozzle 3 is hard to deteriorate. Therefore, the maintenance cost of the shot peening apparatus 1 is low.

  Further, according to the shot peening method and the shot peening apparatus 1 of the present embodiment, in the processing step, the nozzle 3 is rotated around the axis while moving linearly in the vertical direction. For this reason, it is effective when the inner diameter of the coil spring C is smaller than the outer diameter of the nozzle 3.

  Further, according to the shot peening method and the shot peening apparatus 1 of the present embodiment, the coil spring C can be taken in and out of the reflecting member 2 by detaching the cover 21 from the table 20. For this reason, taking in and out of the coil spring C is easy. Further, when the coil spring C is set on the table 20, the coil spring C can be arranged using the mounting boss 203 as a guide. For this reason, the positioning of the coil spring C is simple. Further, since the coil spring C is fixed to the mounting boss 203, the coil spring C is unlikely to fall down in the processing step.

  Further, according to the shot peening method and the shot peening apparatus 1 of the present embodiment, the blower 90 is used as the gas supply apparatus. For this reason, compared with the case where a compressor is used, the energy cost required for supply of air is low.

  In addition, according to the shot peening method and the shot peening apparatus 1 of the present embodiment, it is easier to fire a shot S having a small diameter (for example, 0.2 mm or less) compared to an impeller type shot peening apparatus. Further, it is easy to increase the speed of the shot S as compared with the impeller type shot peening apparatus. For this reason, sufficient plastic deformation can be given to the coil spring C regardless of whether it is cold or warm.

<Second embodiment>
The difference between the present embodiment and the first embodiment is that the nozzle rotates around the axis while screwing in the processing step. Here, only differences will be described. FIG. 6 is a perspective view of the shot peening apparatus according to the present embodiment. In addition, about the site | part corresponding to FIG. 1, it shows with the same code | symbol.

  As shown in FIG. 6, the inner diameter of the coil spring C is larger than the outer diameter of the nozzle 3. If the nozzle 3 is moved linearly in the vertical direction at the radial center of the coil spring C, the distance between the nozzle 3 and the coil spring C is increased. For this reason, the shot is decelerated before colliding with the coil spring C. Therefore, it is difficult to obtain a sufficient shot peening effect.

  In this regard, the nozzle 3 of the shot peening apparatus 1 according to the present embodiment spirals in a position spaced apart from the radially inner end of the coil spring C by a predetermined distance from the radially inner end, as indicated by a thick arrow in the figure. Move up and down. For this reason, the distance between the nozzle 3 and the coil spring C is difficult to be separated. Therefore, it is difficult for the shot to decelerate before colliding with the coil spring C. Therefore, although the coil spring C has a large diameter, a sufficient shot peening effect can be obtained.

<Third embodiment>
The difference between the present embodiment and the first embodiment is that the nozzle rotates around the axis by utilizing a reaction to fire a shot. Here, only differences will be described. In FIG. 7, the radial direction sectional drawing of the shot peening apparatus of this embodiment is shown. In addition, about the site | part corresponding to FIG. 3, it shows with the same code | symbol.

  As shown in FIG. 7, the shot launch port 300 is inclined at a predetermined angle with respect to the radial direction as if it were a blade of a windmill. When an air flow and shot S are fired from shot launch port 300, a couple is generated. For this reason, the nozzle 3 rotates around the axis as shown by the white arrow in the figure. Therefore, the shot launch port 300 can be rotated around the axis. According to the shot peening apparatus 1 of the present embodiment, a drive mechanism for rotating the nozzle 3 around the axis is unnecessary. This simplifies the apparatus configuration both mechanically and electrically.

<Fourth embodiment>
The difference between the present embodiment and the first embodiment is that only one shot launcher is arranged in the nozzle. Here, only differences will be described. FIG. 8 is a sectional view in the axial direction of the nozzle of the shot peening apparatus of the present embodiment. In addition, about the site | part corresponding to FIG. 3, it shows with the same code | symbol.

  As shown in FIG. 8, the nozzle 3 includes a shot supply passage 30. The shot supply passage 30 is disposed at the radial center of the nozzle 3. The shot supply passage 30 extends in the vertical direction. The upper end of the shot supply passage 30 is curved outward in the radial direction. A single shot launch port 300 is disposed at the downstream end of the shot supply passage 30.

  According to the shot peening apparatus 1 of the present embodiment, the shape of the shot supply passage 30 is simple. In addition, it is easier to secure a flow rate necessary for firing a shot than when a plurality of shot launch ports 300 are arranged.

<Fifth embodiment>
The difference between this embodiment and the first embodiment is that a compressed state reflecting member arranging step and a compressed state processing step are set after the shot peening method of the first embodiment. Here, only differences will be described.

  FIG. 9 is a cross-sectional view in the axial direction of a shot peening apparatus used in the compressed state reflecting member arranging step and the compressed state processing step of the shot peening method of the present embodiment. In addition, about the site | part corresponding to FIG. 3, it shows with the same code | symbol. As shown in FIG. 9, an annular compression rib 211 projects downward from the upper bottom surface of the cover 21.

  The shot peening method of the present embodiment includes a reflecting member arranging step, a processing step, a compressed state reflecting member arranging step, and a compressed state treating step.

  In the reflection member arranging step and the processing step, shot peening is applied to the coil spring as in the first embodiment. In the compressed state reflecting member arranging step, first, the coil spring C is attached to the attachment boss 203. Next, the cover 21 is laid on the table 20 from above the coil spring C. At this time, the upper end of the coil spring C is pressed downward by the compression rib 211 of the cover 21. For this reason, the coil spring C is accommodated in the cover 21 in a compressed state in which the coil spring C is compressed in the axial direction with respect to the natural length state (no load state). Then, the cover 21 is fixed to the table 20 by the engagement mechanism. In the compressed state processing step, predetermined shot peening is performed on the coil spring C in the compressed state.

  According to the shot peening method of the present embodiment, the shot spring peening can be performed twice on the coil spring C in the processing step and the compression state processing step. For this reason, the compressive residual stress of the coil spring C can be further improved.

  In the compressed state processing step, shot peening is performed on the coil spring C in a compressed state, not in a natural length state. Also in this respect, the compressive residual stress of the coil spring C can be improved.

  By the way, in the compressed state, the gap between the wire rods adjacent to each other in the axial direction of the coil spring C becomes smaller than in the natural length state. For this reason, it becomes difficult to perform shot peening on the radially outer portion of the coil spring C in the compression state processing step. However, sufficient shot peening has already been applied to the radially outer portion of the coil spring C in the processing step. For this reason, the compressive residual stress of a radially outer portion can be improved. On the other hand, in the compressed state processing step, the compressive residual stress of the radially inner portion of the coil spring C can be further improved.

<Others>
The embodiments of the shot peening method, the shot peening apparatus, and the coil spring of the present invention have been described above. However, the embodiment is not particularly limited to the above embodiment. Various modifications and improvements that can be made by those skilled in the art are also possible.

  The material, diameter, pitch, etc. of the coil spring C are not particularly limited. The material of the reflecting member 2 is not particularly limited. A material that is not easily damaged by the shot S is preferred. Further, the arrangement direction of the coil spring C in the shot peening apparatus 1 is not particularly limited. For example, the coil spring C may be arranged so that the axial direction is aligned in the horizontal direction. Further, the type of the coil spring C is not particularly limited. For example, it may be a valve spring for an intake / exhaust valve of an automobile, a coil spring for suspension, or the like.

  Further, the shape of the reflection surfaces 210 and 202 is not particularly limited. In order to perform shot peening on the coil spring C, an appropriate reflection angle of the shot S may be obtained. For example, it may be a curved surface (such as a cylindrical back surface, a conical back surface, or a spherical back surface) or a flat surface. Moreover, you may combine a curved surface and a plane suitably. Moreover, you may arrange | position a convex part and a recessed part to the reflective surfaces 210 and 202 suitably.

  There are no particular restrictions on the number of shot launch ports 300 arranged in the nozzle 3, the circumferential position, and the axial position. The smaller the number of arrangements, the easier it is to secure the flow velocity necessary to fire the shot S. Moreover, in the said embodiment, although the blower 90 was used as a gas supply apparatus, you may use a compressor. Moreover, as gas supplied from the blower 90, you may use inert gas etc. other than air.

  In the third embodiment, the nozzle 3 is rotated around the axis only by the couple of the nozzle 3 itself. However, the couple of the nozzle 3 itself and a drive mechanism for rotating the nozzle 3 may be used in combination. In this case, the driving force borne by the driving mechanism is smaller than in the case where the couple of the nozzle 3 itself is not used.

1: shot peening apparatus, 2: reflecting member, 3: nozzle.
20: Table, 21: Cover, 30: Shot supply passage, 90: Blower, 91: Input amount adjusting valve, 92: Hopper.
200: Nozzle insertion hole, 201: Exhaust hole, 202: Reflecting surface, 203: Mounting boss, 210: Reflecting surface, 211: Compression rib, 300: Shot launch port, 301: Convex part.
S: Shot, C: Coil spring.

Claims (4)

A reflecting member disposing step of disposing a reflecting member having a reflecting surface on the inner side so as to cover the entire axial length of the coil spring from the radially outer side;
A nozzle is inserted inside the coil spring in the radial direction, and while moving the nozzle in the axial direction and rotating around the axis, a shot is shot from the nozzle toward the outside in the radial direction by an air flow. A process of performing shot peening on the coil spring from the inside, and performing shot peening on the coil spring from the outside in the radial direction by the shot reflected by the reflecting surface;
A shot peening method comprising: A reflection member disposed so as to cover the entire axial length of the coil spring from the outside in the radial direction, and having a reflection surface on the inside;
A nozzle that is inserted on the radially inner side of the coil spring, moves in the axial direction and rotates around the axis, and fires a shot toward the radially outer side by an air flow;
With
A shot peening apparatus that applies shot peening to the coil spring from the radially inner side by the shot and applies shot peening to the coil spring from the radially outer side by the shot reflected by the reflecting surface. The reflective member is
A table having a nozzle insertion hole into which the nozzle is inserted from the outside, and the coil spring disposed on the inner surface so that the nozzle insertion hole is accommodated radially inside;
A cover disposed on the inner surface of the table such that the entire axial length of the coil spring is accommodated radially inside;
The shot peening apparatus according to claim 2, comprising:   A coil spring subjected to shot peening so that the compressive residual stress in the radially inner portion is equal to or greater than the compressive residual stress in the radially outer portion.

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