Shot-peening device and shot-peening method

Abstract

To provide a shot-peening device capable of improving fatigue strength of a workpiece by applying compressive residual stress to the inside of the workpiece.SOLUTION: A shot-peening device comprises: a hollow housing 2; and vibration means 3 for vibrating the housing 2. The housing 2 accommodates a workpiece W and shot SH therein. Due to this configuration, the vibration means 3 vibrates the housing 2 with the workpiece W and the shot SH accommodated therein. Accordingly, the fatigue strength of the workpiece W is improved by applying compressive residual stress to the inside of the workpiece W.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a shot peening apparatus and a shot peening method. [Background technology]

[0002] A conventional shot peening apparatus is disclosed in, for example, Patent Document 1. In the shot peening apparatus disclosed in Patent Document 1, a plurality of spherical particles (hereinafter referred to as shots) are transported upward by a bucket elevator, and then supplied toward a lateral screw. The shots flowing from the lateral screw into a guide line drop downward along the guide line and are guided to an impeller. As a result, the shots are projected toward a workpiece by the impeller.

[0003] To explain this point in detail with reference to Fig. 6, a conventional shot peening apparatus 100 includes an endless belt 101 that is arc-shaped when viewed from the front. This endless belt 101 moves in the direction of an arrow Y100 shown in Fig. 6. Thus, a workpiece W (a compression coil spring is exemplified in Fig. 6) is placed on such an endless belt 101. Shots SH are projected onto this workpiece W by an impeller 102. As a result, compressive residual stress is imparted to the workpiece W, and the fatigue strength of the workpiece W can be improved. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6304957 Summary of the Invention [Problem to be solved by the invention]

[0005] Incidentally, it is known that the stress applied to the inside of the workpiece W, particularly in the case of a compression coil spring, is higher than the stress applied to the outside. For this reason, compression coil springs often break from the inside. Therefore, in order to improve the fatigue strength of compression coil springs, it is possible to impart compressive residual stress to the inside of the compression coil spring. However, in order to impart compressive residual stress to the inside of a compression coil spring, it is necessary to increase the kinetic energy of the shot SH. As is well known, the kinetic energy is 1 / 2 mv 2 Since m is expressed as m: mass, v: velocity, the only way to improve the kinetic energy is to increase the mass and / or velocity of the shot SH. However, if the impeller 102 is used to project the shot SH at high speed, the mass of the shot SH must be reduced. On the other hand, if the mass of the shot SH is increased, the particle size of the shot SH increases. Therefore, if the internal diameter side of the compression coil spring is to be imparted with residual stress, the shot SH must be projected at high speed with a particle size smaller than the pitch between the wires of the compression coil spring. However, if the shot SH with a small particle size is projected at high speed, the surface of the compression coil spring may become rough, which may lead to a decrease in fatigue strength. Therefore, since such problems may occur, the impeller 102 cannot project the shot SH at high speed, and the velocity must be reduced. Therefore, in the conventional shot peening device 100, there is a limit to the mass and velocity of the shot SH, and the kinetic energy cannot be improved, and ultimately, there is a problem that the compressive residual stress cannot be imparted to the inside of the compression coil spring.

[0006] In view of the above problems, an object of the present invention is to provide a shot peening apparatus and a shot peening method capable of improving the fatigue strength of a workpiece by imparting compressive residual stress to the inside of the workpiece. [Means for solving the problem]

[0007] The above object of the present invention can be achieved by the following means. Note that the parentheses indicate reference symbols of the embodiments described below, but the present invention is not limited thereto.

[0008] According to the shot peening apparatus of the present invention, a hollow housing (2) and and a vibration means (3) for vibrating the housing (2), The housing (2) contains a workpiece (W) and shot (SH), The vibration means (3) is characterized by vibrating the case (2) in which the workpiece (W) and the shot (SH) are housed.

[0009] According to the invention of claim 2, in the shot peening apparatus (1) of claim 1, the shot (SH) is disposed inside the workpiece (W).

[0010] According to the invention of claim 3, in the shot peening apparatus (1) of claim 2, the workpiece (W) is a compression coil spring, The shot (SH) is characterized in that its diameter (H1) is larger than the pitch (H2) of the compression coil spring.

[0011] According to a fourth aspect of the present invention, in the shot peening apparatus (1) according to the first aspect, the shot peening apparatus (1) further comprises a rotating means for rotating the housing (2).

[0012] According to the invention of claim 5, in the shot peening apparatus (1) of claim 1, the workpiece (W) is a compression coil spring, The shot (SH) and the compression coil spring are stored in a compressed state in the housing (2), The vibration means (3) is characterized by vibrating the compression coil spring in the compressed state and the housing (2) in which the shot (SH) is housed.

[0013] The shot peening method according to the invention of claim 6 is characterized in that after a compressive residual stress is imparted to the workpiece (W) by using the shot peening apparatus (1) according to claim 1, a compressive residual stress is again imparted to the workpiece (W) to which the compressive residual stress has been imparted by using an existing shot peening apparatus (conventional shot peening apparatus (100)).

[0014] The shot peening method according to the invention of claim 7 is characterized in that, after compressive residual stress is imparted to a workpiece (W) by using an existing shot peening apparatus (conventional shot peening apparatus (100)), the surface roughness of the workpiece (W) is improved by using the shot peening apparatus (1) according to claim 1. Effect of the Invention

[0015] Next, the effects of the present invention will be described with reference to the drawings. Note that the reference symbols in the parentheses are those of the embodiments described below, but the present invention is not limited thereto.

[0016] According to the invention of claim 1, the vibration means (3) vibrates the workpiece (W) and the housing (2) containing the shots (SH), so there is no limit to the mass or speed of the shots (SH) as in the conventional shot peening device (100). Therefore, the kinetic energy can be improved and compressive residual stress can be imparted to the inside of the workpiece (W). Therefore, according to the present invention, the fatigue strength of the workpiece (W) can be improved by imparting compressive residual stress to the inside of the workpiece (W).

[0017] According to the invention of claim 2, since the shots (SH) are arranged inside the workpiece (W), compressive residual stress can be reliably imparted to the inside of the workpiece (W).

[0018] According to the invention of claim 3, the diameter (H1) of the shot (SH) is formed to be larger than the pitch (H2) of the compression coil spring, so that it is possible to prevent the shot (SH) from not coming into contact with the inside of the workpiece (W) and going outside the workpiece (W).

[0019] According to the invention of claim 4, since there is provided a rotating means for rotating the housing (2), it is possible to rotate the workpiece (W) when the workpiece (W) does not rotate freely.

[0020] According to the invention of claim 5, the compression coil spring in a compressed state and the housing (2) containing the shot (SH) are vibrated, so that optimal stress peening can be performed.

[0021] According to the invention of claim 6, after compressive residual stress is imparted to the workpiece (W), a compressive residual stress is imparted again to the workpiece (W) to which the compressive residual stress has been imparted, using an existing shot peening device (conventional shot peening device (100)). This makes it possible to impart compressive residual stress accurately to the inside and outside of the workpiece (W).

[0022] According to the invention of claim 7, a compressive residual stress is imparted to the workpiece (W) using an existing shot peening device (conventional shot peening device (100)), and then the surface roughness of the workpiece (W) is improved using the shot peening device (1). This makes it possible to effectively improve the surface roughness of the workpiece (W). [Brief description of the drawings]

[0023] [Figure 1] 1 is a perspective view of a shot peening apparatus according to an embodiment of the present invention, as viewed from above; [Diagram 2] 1A is a vertical cross-sectional view of a housing according to the embodiment, and FIG. 1B is a partial vertical cross-sectional front view of a part of the shot peening apparatus according to the embodiment as viewed from the front. [Diagram 3]FIG. 2 is a perspective view of a jig used when compressing a compression coil spring, which is the workpiece. [Figure 4] 4(a) to 4(c) are side views of the jig illustrating a method for compressing a compression coil spring, which is an object to be treated, using the jig shown in FIG. [Diagram 5] 1A is a longitudinal sectional view of a case according to the embodiment in which a compression coil spring, which is an object to be treated, is compressed together with a jig and shots are stored in the case, and FIG. 1B is a partial longitudinal sectional front view of a part of the shot peening apparatus according to the embodiment as viewed from the front. [Figure 6] FIG. 1 is a schematic diagram illustrating a conventional shot peening device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] Hereinafter, an embodiment of a shot peening apparatus according to the present invention will be specifically described with reference to the drawings. In the following description, when directions such as up, down, left, and right are indicated, they refer to up, down, left, and right when viewed from the front in the drawings.

[0025] <Outline of shot peening equipment> The shot peening apparatus according to this embodiment can improve the fatigue strength of a workpiece by imparting compressive residual stress to the inside of the workpiece. Specifically, as shown in Fig. 1 and Fig. 2(b), the shot peening apparatus 1 is composed of a housing 2 and a vibration means 3. Each component will be described in detail below.

[0026] <Explanation of the case> The housing 2 is formed, for example, from an acrylic case etc. As shown in Fig. 2, the housing 2 is formed in a horizontally elongated rectangular shape in cross section and is formed in a cylindrical shape with a hollow interior.

[0027] On the other hand, as shown in FIG. 1, the housing 2 formed as described above has rod-shaped supports 2a attached and fixed to the left and right side surfaces.

[0028] 1 and 2, a single workpiece W (a compression coil spring is illustrated in the drawings) is stored in the housing 2 configured as described above. As shown in FIG. 2, the left and right ends of the workpiece W are rotatably supported by supports 2a that protrude inwardly into the housing 2. As a result, the workpiece W is maintained in a stored position in the housing 2 at a predetermined distance (e.g., distance D1) from the upper inner wall surface 2b and the lower inner wall surface 2c of the housing 2, as shown in FIG. 2(a).

[0029] 2, a plurality of shots SH are disposed on the inside, i.e., the inner diameter side, of the workpiece W. As the shots SH, for example, steel balls for bearings having excellent wear resistance are used.

[0030] <Explanation of excitation method> The vibration means 3 includes a circular base 30 as shown in Fig. 1. A pair of mounting bases 31 are attached and fixed to the left and right sides of an upper surface 30a of the base 30 using bolts B as shown in Fig. 1. The mounting bases 31 are disposed opposite each other as shown in Fig. 1, and are formed in a substantially semicircular shape. The support parts 2a of the housing 2 are attached and fixed to the pair of mounting bases 31, respectively.

[0031] On the other hand, as shown in Fig. 2(b), a rod-shaped piston rod 32 is attached and fixed to the center of the lower surface 30b of the base 30. This piston rod 32 is movable in the vertical direction (the direction of the arrow Y1 shown in Fig. 2(b)) by hydraulic pressure or the like (not shown).

[0032] Thus, the shot peening apparatus 1 is configured as described above.

[0033] <Explanation of shot peening equipment usage examples> Next, an example of use of the shot peening apparatus 1 configured as above will be described.

[0034] First, before moving the piston rod 32 shown in FIG. 2(b) in the vertical direction, the workpiece W (illustrated as a compression coil spring) is stored in the housing 2 as shown in FIGS. 1 and 2(a), and further, a plurality of shots SH are arranged inside the workpiece W, i.e., on the inner diameter side.

[0035] In this state, when the piston rod 32 shown in Fig. 2(b) is moved up and down, the base 30 also moves up and down, and further, the pair of mounting bases 31 also move up and down. This causes the housing 2 to move up and down. Therefore, this causes the housing 2 to vibrate.

[0036] Thus, when the housing 2 is vibrated in this manner, the workpiece W and shots SH housed in the housing 2 are also vibrated. As a result, the shots SH move irregularly in the vertical direction inside the workpiece W, i.e., on the inner diameter side, as shown in the direction of the arrow in FIG. 2(b). Furthermore, since the workpiece W in this embodiment is a compression coil spring and is formed in a spiral shape, it moves in the vertical direction, i.e., it freely rotates with the support part 2a as a base point with vibration. Therefore, the shots SH come into contact with the entire inner diameter of the workpiece W. This makes it possible to impart compressive residual stress to the inside of the workpiece W, i.e., the inner diameter. Therefore, the fatigue strength of the workpiece W can be improved.

[0037] To explain this in more detail, as explained above, kinetic energy is 1 / 2mv 2 (m: mass, v: velocity). In this case, unlike the conventional shot peening apparatus 100, the shot peening apparatus 1 according to this embodiment does not need to project the shots SH at high speed, and a plurality of shots SH are arranged in advance inside the workpiece W, that is, on the inner diameter side. Therefore, the size (diameter) of the shot SH can be made larger (e.g., 6 mm) than that used in the conventional shot peening apparatus 100 (e.g., 3 mm). Also, the vibration speed can be increased by increasing the speed of movement in the vertical direction.

[0038] Therefore, the shot peening apparatus 1 according to this embodiment can improve the kinetic energy because there is no limit to the mass or speed of the shot SH, unlike the conventional shot peening apparatus 100. Therefore, the shot peening apparatus 1 according to this embodiment can impart compressive residual stress to the inside of the workpiece W. Therefore, according to this embodiment, by imparting compressive residual stress to the inside of the workpiece W, the fatigue strength of the workpiece W can be improved.

[0039] In this embodiment, the diameter H1 (for example, 6 mm) of the shot SH shown in FIG. 2(b) is formed to be larger than the pitch H2 (for example, 4.5 mm) of the workpiece W. This makes it possible to prevent the shot SH from coming into contact with the inner diameter side (inside) of the workpiece W and going outside the workpiece W. In other words, if the shot SH goes outside the workpiece W, there is a possibility that the shot SH will be caught between the pitch H2 of the workpiece W. If such a situation occurs, the workpiece W will not rotate freely, and there is a possibility that compressive residual stress cannot be imparted to the inside of the workpiece W. Therefore, in this embodiment, the diameter H1 (for example, 6 mm) of the shot SH shown in FIG. 2(b) is formed to be larger than the pitch H2 (for example, 4.5 mm) of the workpiece W.

[0040] <Description of Modifications> It should be noted that the shapes and the like shown in this embodiment are merely examples, and various modifications and changes are possible within the scope of the gist of the present invention described in the claims. For example, the housing 2 and the vibration means 3 described in this embodiment may have any shape and configuration as long as they have the same functions as those described above.

[0041] In addition, in this embodiment, no compressive residual stress is imparted to the outside of the compression coil spring as the workpiece W, but if it is not necessary, it is not necessary to impart it. As described above, compression coil springs often break from the inside, so if compressive residual stress is imparted to the inside of the compression coil spring, the fatigue strength of the compression coil spring can be improved and breakage from the inside can be prevented.

[0042] On the other hand, when compressive residual stress is applied to the outside of a compression coil spring as the workpiece W, a plurality of shots SH may be disposed outside the workpiece W housed in the housing 2.

[0043] On the other hand, it is also possible to use the shot peening apparatus 1 according to this embodiment to impart compressive residual stress to the inside of the workpiece W, and then use a conventional shot peening apparatus 100 to impart compressive residual stress to the outside of the workpiece W. In this way, when manufacturing the shot peening apparatus 1, it is possible to reduce the manufacturing cost since the shot peening apparatus 1 can be a minimum shot peening apparatus 1 that only imparts compressive residual stress to the inside of the workpiece W. Furthermore, it is possible to impart compressive residual stress accurately to the inside and outside of the workpiece W.

[0044] On the other hand, after compressive residual stress is imparted to the workpiece W using the conventional shot peening apparatus 100, the shot peening apparatus 1 according to this embodiment may be used to improve the surface roughness inside the workpiece W. In this way, the surface roughness inside the workpiece W can be effectively improved.

[0045] In this embodiment, the storage position of the workpiece W in the housing 2 is a predetermined distance away from the upper inner wall surface 2b and the lower inner wall surface 2c of the housing 2 (for example, distance D1), but it is not necessary to store the workpiece W at a predetermined distance away (for example, distance D1). However, if the workpiece W is not stored at a predetermined distance away (for example, distance D1), the workpiece W may not move in the vertical direction, that is, may not rotate freely around the support portion 2a due to vibration, by contacting the upper inner wall surface 2b and the lower inner wall surface 2c of the housing 2. Therefore, it is preferable to store the workpiece W in the housing 2 at a predetermined distance away from the upper inner wall surface 2b and the lower inner wall surface 2c of the housing 2 (for example, distance D1). However, if the workpiece W does not rotate freely, the workpiece W may be rotated by rotating the support portion 2a by a motor or the like and rotating the housing 2 itself.

[0046] Furthermore, in this embodiment, an example has been shown in which a single (one) workpiece W is stored in the housing 2, but the housing 2 itself may be elongated, for example, so that a plurality of workpieces W can be stored therein.

[0047] In addition, in this embodiment, a compression coil spring is used as an example of the workpiece W, but the present invention is not limited to this and can be applied to any part that needs to be imparted with compressive residual stress, such as a welded pipe.

[0048] In addition, in the present embodiment, an example in which the compression coil spring, which is the workpiece W, is simply stored has been shown, but the present invention is not limited to this, and the compression coil spring may be stored in a compressed state and subjected to so-called stress peening. This point will be described in detail below.

[0049] First, to compress the compression coil spring, which is the workpiece W, a jig 4 as shown in Fig. 3 is used. As shown in Fig. 3, this jig 4 has a thick circular first support plate 40 and a second support plate 41 having the same shape as the first support plate 40, which are provided at a fixed interval in the vertical direction. As shown in Fig. 3, this first support plate 40 has a U-shaped left cutout 40b on the left side toward the center, and further has a U-shaped right cutout 40c on the right side toward the center.

[0050] On the other hand, as shown in Fig. 3, the first support plate 40 has a circular front through-hole 40d penetrating in the up-down direction on the front end surface side. Furthermore, as shown in Fig. 3, the first support plate 40 has a circular rear through-hole 40e penetrating in the up-down direction on the rear end surface side.

[0051] Thus, the first support plate 40 and the second support plate 41 thus formed are formed to have the same shape. Specifically, as shown in Fig. 3, the second support plate 41 has a U-shaped left cutout 41b on the left side surface toward the center, and a U-shaped right cutout 41c on the right side surface toward the center. Furthermore, as shown in Fig. 3, the second support plate 41 has a circular front through hole 41d penetrating in the up-down direction on the front end surface side, and a circular rear through hole 41e penetrating in the up-down direction on the rear end surface side.

[0052] Thus, as shown in Fig. 3, a compression coil spring, which is the workpiece W, is placed between the first support plate 40 and the second support plate 41 formed in this manner. As a result, the compression coil spring, which is the workpiece W, is sandwiched between the first support plate 40 and the second support plate 41. Therefore, if the distance between the first support plate 40 and the second support plate 41 is reduced, the compression coil spring, which is the workpiece W, is compressed by the first support plate 40 and the second support plate 41. Note that the state shown in Fig. 3 shows a state in which the compression coil spring, which is the workpiece W, is compressed by reducing the distance between the first support plate 40 and the second support plate 41. In Fig. 3, in order to maintain the distance between the first support plate 40 and the second support plate 41, a first support rod 42 is inserted into the left notch 40b of the first support plate 40 and the left notch 41b of the second support plate 41, and its position is fixed by a pair of first support nuts 42a (see also Fig. 4(c)). Furthermore, as shown in Fig. 3, a second support rod 43 is inserted into the right notch 40c of the first support plate 40 and the right notch 41c of the second support plate 41, and its position is fixed by a pair of second support nuts 43a (see also Fig. 4(c)). This maintains the distance between the first support plate 40 and the second support plate 41.

[0053] Here, a method of compressing the compression coil spring, which is the workpiece W, using the jig 4 will be described in more detail. As shown in FIG. 4(a), the compression coil spring, which is the workpiece W, is placed between the first support plate 40 and the second support plate 41. At this time, as shown in FIG. 4(a), the first set rod 44 is inserted into the front through hole 40d of the first support plate 40 and the front through hole 41d of the second support plate 41, and its position is fixed by the left first set nut 44a located on the first support plate 40 side and the right first set nut 44b located on the second support plate 41 side. Furthermore, as shown in FIG. 4(a), the second set rod 45 is inserted into the rear through hole 40e of the first support plate 40 and the rear through hole 41e of the second support plate 41, and its position is fixed by the left second set nut 45a located on the first support plate 40 side and the right second set nut 45b located on the second support plate 41 side.

[0054] In this state, when the right first set nut 44b and the right second set nut 45b shown in Fig. 4(a) are tightened, the second support plate 41 moves in the illustrated left direction using the first set rod 44 and the second set rod 45 as guides. As a result, as shown in Fig. 4(b), the second support plate 41 approaches the first support plate 40 and the distance between the first support plate 40 and the second support plate 41 decreases, so that the compression coil spring, which is the workpiece W sandwiched between the first support plate 40 and the second support plate 41, is compressed.

[0055] As will be described later, the jig 4 is stored in the housing 2. Therefore, in this state, as shown in FIG. 4(b), there is a possibility that the jig 4 cannot be stored in the housing 2 due to the excess length of the first set rod 44 and the second set rod 45 on the right side in the drawing.

[0056] In this embodiment, after compressing the compression coil spring, which is the workpiece W, the second support rod 43 is inserted into the right notch 40c of the first support plate 40 and the right notch 41c of the second support plate 41, and the position is fixed by a pair of second support nuts 43a, as shown in Fig. 4(b), in order to maintain the distance between the first support plate 40 and the second support plate 41 at that position, as shown in Fig. 4(b). Furthermore, the first support rod 42 is inserted into the left notch 40b of the first support plate 40 and the left notch 41b of the second support plate 41, and the position is fixed by a pair of first support nuts 42a, as shown in Fig. 4(c). In this way, when the distance between the first support plate 40 and the second support plate 41 is maintained at the position shown in FIG. 4(b), the left first set nut 44a and the right first set nut 44b shown in FIG. 4(b) are loosened, and the first set rod 44 is removed from the front through hole 40d of the first support plate 40 and the front through hole 41d of the second support plate 41. Then, the left second set nut 45a and the right second set nut 45b shown in FIG. 4(b) are loosened, and the second set rod 45 is removed from the rear through hole 40e of the first support plate 40 and the rear through hole 41e of the second support plate 41. This results in the state shown in FIG. 4(c). Therefore, by doing this, it is possible to eliminate the possibility that the jig 4 cannot be stored in the housing 2 due to the extra length of the first set rod 44 and the second set rod 45 on the right side of the figure.

[0057] Next, the jig 4 in the state shown in FIG. 4(c) is placed in the housing 2 as shown in FIG. 5(a). At this time, the jig 4 in the state shown in FIG. 4(c) is placed in the housing 2 at a position (for example, distance D1) away from the upper inner wall surface 2b and the lower inner wall surface 2c of the housing 2 by a predetermined distance. At this time, as shown in FIG. 5(a), a plurality of shots SH are placed inside the workpiece W, that is, on the inner diameter side. In this state, as shown in FIG. 5(b), the support parts 2a of the housing 2 are attached and fixed to the pair of mounting bases 31, respectively, and the piston rod 32 shown in FIG. 5(b) is moved in the vertical direction (arrow Y2 direction). As a result, the base 30 also moves in the vertical direction, and further, the pair of mounting bases 31 also move in the vertical direction, so that the housing 2 also moves in the vertical direction. Therefore, the housing 2 is vibrated.

[0058] Thus, when the housing 2 is vibrated in this manner, the workpiece W and shots SH housed in the housing 2 are also vibrated. As a result, the shots SH move irregularly in the vertical direction inside the workpiece W, that is, on the inner diameter side, as shown in the arrow direction in FIG. 5(b). Furthermore, as shown in FIG. 5(a), the jig 4 in the state shown in FIG. 4(c) is disposed at a position (for example, distance D1) away from the upper inner wall surface 2b and the lower inner wall surface 2c of the housing 2, and therefore, since there is a difference (for example, distance D1×2) between the circumference of the housing 2 and the circumference of the jig 4 (first support plate 40 and second support plate 41), the difference causes the jig 4 to move in the vertical direction, that is, rotate with the support part 2a as the base point in response to the vibration. Therefore, the shots SH come into contact with the entire inner diameter of the workpiece W. This makes it possible to impart compressive residual stress to the inside, i.e., the inner diameter, of the workpiece W, which is a compressed compression coil spring, and therefore the fatigue strength of the workpiece W can be improved.

[0059] However, as explained in the above problem to be solved by the present invention, the conventional shot peening apparatus 100 has a problem in that it is not possible to impart compressive residual stress to the inside of a compression coil spring. This problem becomes more pronounced when stress peening is performed. That is, when attempting to impart compressive residual stress to the inside of a compressed compression coil spring, the inter-wire gap becomes smaller compared to an uncompressed compression coil spring, making it more difficult for the shots SH to enter the inner diameter side of the compression coil spring. Therefore, this problem becomes more pronounced when stress peening is performed.

[0060] However, by employing the method of the present embodiment described above, such problems can be solved. Therefore, by employing the method of the present embodiment described above, optimal stress peening can be performed.

[0061] In the above explanation, an example has been shown in which the jig 4 is used to compress the compression coil spring, which is the workpiece W, but the present invention is not limited to this. Any method may be used as long as the compression coil spring, which is the workpiece W, can be stored in the housing 2 in a compressed state. [Explanation of symbols]

[0062] 1 Shot peening equipment 2. Chassis 3. Vibration Method 4. Jig W Processing object SH Shot H1 (shot) diameter H2 (compression spring) pitch 100 Conventional shot peening equipment (existing shot peening equipment)

Claims

1. A hollow housing; and a vibration means for vibrating the housing, The housing contains a workpiece and shot, The vibration means is a shot peening device that vibrates the workpiece and the casing in which the shot is stored.

2. 2. The shot peening apparatus according to claim 1, wherein the shots are disposed inside the workpiece.

3. the workpiece is a compression coil spring, 3. The shot peening apparatus according to claim 2, wherein the diameter of the shot is larger than the pitch of the compression coil spring.

4. 2. The shot peening apparatus according to claim 1, further comprising a rotating means for rotating said housing.

5. the workpiece is a compression coil spring, The shot and the compression coil spring are stored in a compressed state in the housing, 2. The shot peening apparatus according to claim 1, wherein the vibration means vibrates the compression coil spring in the compressed state and the casing in a state in which the shot is accommodated.

6. 2. A shot peening method comprising: imparting a compressive residual stress to the workpiece by using the shot peening apparatus according to claim 1; and then imparting a compressive residual stress again to the workpiece to which the compressive residual stress has been imparted by using an existing shot peening apparatus.

7. 13. A shot peening method comprising: applying compressive residual stress to a workpiece using an existing shot peening device; and then improving the surface roughness of the workpiece using the shot peening device according to claim 1.

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