Technical Field
[0001] The present invention described herein relate generally to a shot peening device
which performs shot peening (stress shot peening) while a coil spring is being compressed.
Background Art
[0002] In order to increase durability of coil springs used in suspension springs of a suspension
device of a vehicle, shot peening is well-known, which imparts a compressive residual
stress to the coil spring. Patent Literature 1 discloses an example of a conventional
shot peening device. The shot peening device thereof projects shots to the coil spring
from a centrifugal accelerator (impeller) as the coil spring is conveyed. Patent Literature
2 discloses a conventional shot peening device. The shot peening device thereof compresses
the coil spring and performs shot peening while the coil spring is stressed. That
is, the shot peening device of the Patent Literature performs stress shot peening
to impart a greater compressive residual stress to the coil spring. Furthermore, Patent
Literature 3 discloses a shot peening device which performs shot peening on a rotating
turntable in a state where the coil spring is compressed.
Citation List
Patent Literature
Summary of Invention
Technical Problem
[0004] The shot peening device as in Patent Literature 1 simply hits shots to a coil spring,
and thus, there is still a chance to increase the compressive residual stress of the
coil spring. The shot peening device as in Patent Literatures 2 and 3 performs shot
peening while a coil spring is compressed, and therein, the coil spring may be supported
unstably depending on the shape of the coil spring (especially, on the shape of the
end turn portion). Thus, stress shot peening may not be performed suitably because
of the unstable coil spring.
[0005] Accordingly, an object of the present invention is to provide a shot peening device
which can perform shot peening while a desired stress is applied to the coil spring.
Solution to Problem
[0006] According to an embodiment, a shot peening device includes: a turntable mechanism
including a turntable which rotates around a revolution axis; a revolution mechanism
which rotates the turntable mechanism; a holding mechanism which holds a lower end
turn portion and an upper end turn portion of a coil spring while the coil spring
is kept standing and moves around the revolution axis with the turntable; a rotation
mechanism which rotates the holding mechanism around a rotation axis; a pressure mechanism
which compresses the coil spring in a state where the coil spring is held by the holding
mechanism; a load detector such as a load cell which detects a compressive load applied
to the coil spring by the pressure mechanism; a projection mechanism which projects
shots to the compressed coil spring; and a controller (for example, a personal computer)
which detects a change in the load based on a signal output from the load detector.
[0007] For example, the load detector may be a load cell disposed in a load transfer path
between the pressure mechanism and the holding mechanism. Furthermore, the controller
may include means for storing a chronological change of the load. Or, the controller
may include a display which displays a chronological change of the load.
[0008] The controller includes means for notifying that the load becomes out of an acceptable
range while the projection mechanism projects shots to the coil spring. The controller
may include a computer program which controls the pressure mechanism such that the
load becomes a constant value while the projection mechanism projects shots to the
coil spring.
Advantageous Effects of Invention
[0009] The present invention can perform shot peening (stress shot peening) in a state where
a desired stress is applied to a coil spring in order to impart the compressive residual
stress to the coil spring, and thus, the coil spring of stable quality can be obtained.
Brief Description of Drawings
[0010]
FIG. 1 is a perspective view of an example of a coil spring.
FIG. 2 is a flowchart of an example of the manufacturing process of the coil spring.
FIG. 3 is a schematic perspective view of a first shot peening device.
FIG. 4 is a perspective view of an example of a part of a conveyor and a transfer
mechanism (robot).
FIG. 5 is a front view of a part of a second shot peening device of an embodiment.
FIG. 6 is a vertical cross-sectional view of the shot peening device of FIG. 5.
FIG. 7 is a horizontal cross-sectional view of the shot peening device of FIG. 5.
FIG. 8 is a perspective view of a lower side holder of the shot peening device of
FIG. 5.
FIG. 9 is a front view of the lower side holder of the shot peening device of FIG.
5 and an end turn portion of the coil spring.
FIG. 10 is a flowchart showing an operation of the shot peening device of FIG. 5.
FIG. 11 is a graph showing an example of chronological change in the load during the
warm stress shot peening.
FIG. 12 is a graph showing another example of chronological change in the load during
the warm stress shot peening.
[0011] Mode for Carrying Out the Invention Hereinafter, a coil spring processing device
including a shot peening device 50 of an embodiment will be explained with reference
to FIGS. 1 to 12.
[0012] FIG. 1 shows an example of a coil spring 1. The coil spring 1 is formed of an element
wire 2 wound helically. The coil spring 1 includes an end turn portion 1a at its one
end and an end turn portion 1b at its other end. A relative relationship between end
1c and other end 1d of the coil spring 1 is constant corresponding to the type of
the coil spring 1.
[0013] In the present application, a position of the coil spring 1 from the end 1c around
an axis C1 may be referred to as a position in a circumferential direction of the
coil, or as a position in a winding direction. The coil spring 1 is, for example,
a cylindrical coil spring; however, the coil spring 1 may be of various types such
as a barrel-type coil spring, a hourglass-type coil spring, a tapered coil spring,
an irregularly-pitched coil spring to conform to types of the suspension device. Furthermore,
the end turn portions 1a and 1b may be formed in a negative pitch (negative pitch
angle), or in a positive pitch (positive pitch angle).
[0014] FIG. 2 shows an example of a manufacturing process of the coil spring 1. In a forming
process S1 of FIG. 2, the element wire 2 is formed helically by a coiling machine.
In a heat treatment process S2, tempering and annealing of the wire 2 are performed
to remove a distortion stress produced in the wire 2 by the forming process S1. For
example, the wire 2 is heated to 400 to 450 °C and then is cooled slowly.
[0015] Furthermore, in a first shot peening process S3, first shot peening is performed
in the warm using the remaining heat of the heat treatment process S2. In the first
shot peening process S3, first shots are projected to the entire surface of the coil
spring 1 in a process temperature of 250 to 300 °C by a first shot peening device
10 which is shown in FIG. 3. The first shot is, for example, a cut wire of which grain
diameter is 1.1 mm. Note that a different shot peening device 10 may be used and a
different shot size (for example, 0.87 to 1.2 mm) may be used. Through the first shot
peening process S3, a compressive residual stress is produced to a relatively deep
position from the surface of the coil spring 1. Furthermore, an oxide film (mill scale
formed in the heat treatment) on the surface of the wire 2 is removed in the first
shot peening process S3.
[0016] FIG. 3 shows a schematic example of the first shot peening device 10. The first shot
peening device 10 includes a pair of rollers 11 and 12 and a shot projector (impeller)
13. Coil springs 1 are disposed on the rollers 11 and 12 in series in a position where
the axis C1 is horizontal (laid horizontally). The coil spring 1 on the rollers 11
and 12 is rotated around the axis C1 to continuously move in the direction of arrow
F1 in the figure. The shot projector 13 projects shots SH1 to the moving coil spring
1.
[0017] FIG. 4 shows a conveyor device 20 which is a part of the coil spring processing device
and a robot 21 handling the coil spring 1. The conveyor device 20 continuously conveys
the coil springs 1 in the direction of arrow F2. The robot 21 holds the coil spring
1 at both sides with an openable chuck 23 provided with the tip of an arm 22. The
robot 21 is an example of a transfer mechanism used for moving the coil spring 1.
[0018] The robot 21 includes a function to store the positions of the ends 1c and 1d of
the coil spring 1 held by the chuck 23 in a memory. The coil spring 1 held by the
robot 21 is preliminarily maintained by means for positioning such as a jig such that
the ends 1c and 1d are set to predetermined positions.
[0019] In a second shot peening process S4, second shot peening (warm stress shot peening)
is performed by a shot peening device 50 of FIGS. 5 to 9. The second shot peening
process S4 is performed in a temperature lower than that of the first shot peening
process S3 (for example, warm zone of 200 to 250 °C) while the coil spring 1 is compressed.
In the second shot peening process S4, second shots are projected to the entire surface
of the coil spring 1. The size of second shot is less than that of the first shot
used in the first shot peening process S3. The second shot is, for example, a cut
wire of which grain diameter is 0.4 to 0.7 mm. Through the second shot peening process
S4, the absolute value of the compressive residual stress in the proximity of the
surface of wire 2 can be increased.
[0020] Then, a setting process S5 is performed if necessary. Furthermore, the coil spring
1 is coated in a coating process S6, and lastly, a quality inspection is performed
in an inspection process S7 and the coil spring 1 is completed.
[0021] Now, the structure and operation of the second shot peening device 50 will be explained
with reference to FIGS. 5 to 9. The second shot peening device 50 is a part of the
coil spring processing device. The second shot peening device 50 performs shot peening
in a warm zone between 200 and 250 °C, for example while the coil spring 1 is kept
standing. "The position where the coil spring 1 is kept standing" means that the axis
C1 of the coil spring 1 is substantially vertical.
[0022] FIG. 5 is a front view showing a part of the second shot peening device 50. FIG.
6 is a vertical cross-sectional view of the second shot peening device 50. FIG. 7
is a horizontal cross-sectional view of the second shot peening device 50. The second
shot peening device 50 includes a housing 51, turntable mechanism 52, projection mechanism
57 (shown in FIG. 6), first elevator mechanism 58, and second elevator mechanism 59.
The projection mechanism 57 includes a first projection unit 55 and a second projection
unit 56. The first elevator mechanism 58 and the second elevator mechanism 59 move
the projection units 55 and 56 vertically.
[0023] The first elevator mechanism 58 and the second elevator mechanism 59 include, for
example, servo motors 58a and 59a (shown in FIG. 6) of which rotation is controlled
by a controller and ball screws 58b and 59b. The elevator mechanisms 58 and 59 move
the projection units 55 and 56 independently and vertically at constant strokes Y1
and Y2 based on the direction and amount of rotation of the servo motors 58a and 59a.
[0024] As shown in FIGS. 6 and 7, a first chamber 61, a second chamber 62, and middle chambers
63 and 64 which are disposed between the chambers 61 and 62 are formed inside the
housing 51. A coil spring inlet/outlet port 65 is formed in the first chamber 61.
The coil spring inlet/outlet port 65 is an opening through which the coil spring 1
is put in and out the first chamber 61 from the outside the housing 51. The second
chamber 62 is provide with a projection port 55a of the first projection unit 55 and
a projection port 56a of the second projection unit 56. Shots SH2 are projected to
the coil spring 1 from the projection ports 55a and 56a.
[0025] As shown in FIG. 7, partition walls 70 and 71 are provided between the first chamber
61 and the middle chambers 63 and 64. Partition walls 72 and 73 are provided between
the second chamber 62 and the middle chambers 63 and 64. Seal walls 74 and 75 are
formed in the middle chambers 63 and 64. The seal walls 74 and 75 keep the shots SH2
projected in the second chamber 62 from going to the first chamber 61.
[0026] As shown in FIG. 5, the turntable mechanism 52 includes a turntable 79, revolution
mechanism 80 (shown in FIG. 5), first holding mechanism 81, and second holding mechanism
82. The turntable 79 rotates around a revolution axis X1 extending in the vertical
direction. The revolution mechanism 80 is provided with a motor. The motor intermittently
rotates the turntable 79, 180° at a time around the revolution axis X1 in either first
direction R1 or second direction R2 (shown in FIG. 7). The holding mechanisms 81 and
82 rotate around the revolution axis X1 together with the turntable 79. The first
holding mechanism 81 includes a lower side holder 81a and an upper side holder 81b.
The lower side holder 81a is disposed on the turntable 79. The upper side holder 81b
is disposed above the lower side holder 81a to be opposed thereto. The second holding
mechanism 82 also includes a lower side holder 82a and an upper side holder 82b. The
lower side holder 82a is disposed on the turntable 79. The upper holder 82b is disposed
above the lower side holder 82a to be opposed thereto.
[0027] The first and second holding mechanism 81 and 82 are positioned 180° symmetrically
about the revolution axis X1. In the rear side of the first and second holding mechanisms
81 and 82 on the turntable 79, a pair of backup plates 83 and 84 (shown in FIG. 7)
are disposed.
[0028] A shifting prevention jig 85 is provided with each of the lower side holder 81a of
the first holding mechanism 81 and the lower side holder 82a of the second holding
mechanism 82. A lower end turn portion 1a of the coil spring 1 can engage the shifting
prevention jig 85. FIGS. 8 and 9 show the lower side holder 81a of the first holding
mechanism 81. The structure of the lower side holder 82a of the second holding mechanism
82 is similar to that of the lower side holder 81a of the first holding mechanism
81. Thus, the lower side holder 81a of the first holding mechanism 81 will be explained
with reference to FIGS. 8 and 9.
[0029] As shown in FIGS. 8 and 9, the shifting prevention jig 85 is provided with the lower
side holder 81a. The shifting prevention jig 85 includes a plurality of pawls (for
example, three pawls) 85a, 85b, and 85c. The pawls 85a, 85b, and 85c are arranged
to conform to the shape, pitch angle, and the like of the end turn portion 1a such
that the end turn portion 1a of the coil spring 1 can be stably supported. For example,
the pawls 85a, 85b, and 85c are disposed on the lower side holder 81a in its peripheral
direction at regular intervals (for example, 90°). Note that the number of pawls of
the lower shifting prevention jig 85 and the number of pawls of an upper shifting
prevention jig 91 may be other than three. Furthermore, the pawls may be disposed
at intervals at an angle other than 90°.
[0030] Guide grooves 86a and 86b are formed in a base member 86 of circular plate shape.
The pawls 85a, 85b, and 85c are movable along the guide grooves 86a and 86b. The pawls
85a, 85b, and 85c are adjusted to a position corresponding to the end turn portion
1a and the pawls 85a, 85b, and 85c are fixed to the base member 86 by blots 87 (shown
in FIG. 9). Height adjustment members 88 and 89 are provided between the base member
86 and the pawls 85b and 85c. The height adjustment members 88 and 89 have thicknesses
T1 and T2 which correspond to the pitch angles of the end turn portions of the coil
spring. Thus, even an end turn portion of negative pitch can be stably mounted on
the pawls 85a, 85b, and 85c. The pawls 85a, 85b, and 85c each include a V-shaped groove
90 into which the end turn portion 1a is inserted.
[0031] With the upper side holders 81b and 82b, a shifting prevention jig 91 corresponding
to the upper end turn portion 1b is provided. As in the lower shifting prevention
jig 85, the upper shifting prevention jig 91 includes a plurality of pawls (for example,
three pawls) conforming to the shape, pitch angle, and the like of the end turn portion
1b. The upper end turn portion 1b is held stably by the pawls. The upper shifting
prevention jig 91 may be formed different from the lower shifting prevention jig 85
depending on the shape of the end turn portion 1b.
[0032] The revolution mechanism 80 (shown in FIG. 5) rotates the turntable 79 around the
revolution axis X1. That is, the revolution mechanism 80 intermittently rotates the
turntable 79, 180° at a time around the revolution axis X1 in either first direction
R1 or second direction R2 (shown in FIG. 7). When the first holding mechanism 81 is
positioned in the first chamber 61, the second holding mechanism 82 is positioned
in the second chamber 62. When the second holding mechanism 82 is positioned in the
first chamber 61, the first holding mechanism 81 is positioned in the second chamber
62.
[0033] Furthermore, the shot peening device 50 includes, as shown in FIG. 5, a pressure
mechanism 93 which compresses the coil spring 1. The pressure mechanism 93 includes
presser units 94 and 95 which move the upper side holders 81b and 82b vertically.
The presser units 94 and 95 include, for example, ball screws and servo motors. The
presser units 94 and 95 can change a compression load (stress) applied to the coil
spring 1 depending on the vertical movement amount of the upper side holders 81b and
82b. The presser units 94 and 95 may use fluid pressure as their drive source such
as a hydraulic cylinder.
[0034] First and second presser units 94 and 95 include load cells 96 and 97, respectively.
The load cells 96 and 97 are examples of load detectors. The load cells (load detectors)
96 and 97 detect a compression load applied to the coil spring 1 during the shot peening,
and input an electrical signal related to the detected compression load to a controller
98. The first load cell 96 is disposed in a load transfer path between the first presser
unit 94 and the upper side holder 81b. The second load cell 97 is disposed in a load
transfer path between the second presser unit 95 and the upper side holder 82b.
[0035] The controller 98 includes a function (computer program) to detect a change of the
load based on the outputs from the load cells 96 and 97. Furthermore, the controller
98 includes a function to notify that the load becomes out of an acceptable range
during the shot peening. Furthermore, the controller 98 compares the load value output
from the load cells 96 and 97 to a certain load value preset in the controller 98.
Furthermore, the controller 98 includes a function to feedback the signals to the
first and second presser units 94 and 95 such that a different between the output
load value and the certain load value reaches zero, that is, a certain load can be
applied to the coil spring 1.
[0036] The shot peening device 50 includes a rotation mechanism 100. The rotation mechanism
100 rotates the coil spring 1 around the rotation axes X2 and X3. The rotation axes
X2 and X3 each extend in a vertical direction. The rotation mechanism 100 includes
a lower rotator 101 and an upper rotator 102. The lower rotator 101 rotates the lower
side holders 81a and 82a around the rotation axes X2 and X3. The upper rotator 102
rotates the upper side holders 81b and 82b around the rotation axes X2 and X3.
[0037] The lower rotator 101 and the upper rotator 102 each include a drive source of a
timing belt and a servo motor. The controller 98 which controls the drive source rotates
the lower rotator 101 and the upper rotator 102 in the same direction in synchronization
at the same revolution rate. That is, the lower side holders 81a and 82a and the upper
side holders 81b and 82b rotate in the same direction in synchronization at the same
revolution rate. Furthermore, the lower side holders 81a and 82a and the upper side
holders 81b and 82b can stop at a preset first rotation stop position or a preset
second rotation stop position on the basis of the data preliminarily input in the
controller 98. The first rotation stop position is, for example, a position suitable
for the robot 21 to hand the coil spring 1 to the holding mechanisms 81 and 82. The
second rotation stop position is, for example, a position suitable for taking the
coil spring 1 from the holding mechanisms 81 and 82.
[0038] An information processor 110 such as a personal computer is connected to the controller
98. The information processor 110 includes an input device 111 used to input various
data such as serial number of coil spring, display 112, and pointing device 113 such
as a mouse. For example, various data (coil diameter, turn number, length, and wire
diameter) related to the coil spring and data related to a load applied to coil spring
during shot peening and the like can be input through the input device 111 or a storage
medium 114.
[0039] The information processor 110 such as a personal computer functions as means for
storing a chronological change of a load applied to the coil spring 1 during the shot
peening. Furthermore, the display 112 of the information processor 110 functions as
means for displaying the chronological change of the load during the shot peening.
Note that the information processor 110 may include the functions of the controller
98.
[0040] FIG. 7 is a horizontal cross-sectional view of the first projection unit 55 and the
second projection unit 56, viewed from the above. The first projection unit 55 includes
an impeller (wing wheel) 121 and a distributor 122. The impeller 121 is rotated by
a motor 120. The distributor 122 supplies shots SH2 to the impeller 121. The second
projection unit 56 includes an impeller 126 rotated by a motor 125 and a distributor
127 which supplies shots SH2 to the impeller 126.
[0041] The first projection unit 55 is supported by a guide member 130 extending vertically
to be movable in the vertical direction. The guide member 130 is provided with the
side part of the housing 51. The first projection unit 55 reciprocates by the first
elevator mechanism 58 (shown in FIG. 6) from a neutral position N1 to go over an ascend
position A1 and a descend position B1. The second projection unit 56 is supported
by a guide member 131 extending vertically to be movable in the vertical direction.
The guide member 131 is provided with the side part of the housing 51. The second
projection unit 56 reciprocates by the second elevator mechanism 59 from neutral position
N2 to go over an ascend position A2 and a descend position B2.
[0042] FIG. 10 is a flowchart showing the operation of the shot peening device 50 of the
present embodiment.
[0043] In step S10 of FIG. 10, the lower side holder 81a of the first holding mechanism
81 is stopped in the first chamber 61. First coil spring 1 is set to (mounted on)
the lower side holder 81a by the robot 21 (shown in FIG. 4). The end turn portion
1a mounted on the lower side holder 81a is stopped by the shifting prevention jig
91 (shown in FIGS. 8 and 9). When the upper side holder 81b descends, the coil spring
1 is compressed between the lower side holder 81a and the upper side holder 81b. At
that time, the second holding mechanism 82 is positioned in the second chamber 62.
The second holding mechanism 82 is in an empty state where no coil spring is mounted
thereon. The coil spring 1 in the left of FIG. 5 is in a free state where no compression
load is applied thereto. The length of the coil spring 1 in the free state (free length)
is L1. The coil spring 1 in the right of FIG. 5 is in a state where it is compressed
to length L2.
[0044] In step S11 of FIG. 10, the turntable 79 rotates 180° in a first direction. By the
rotation, the coil spring 1 held by the first holding mechanism 81 is sent to the
second chamber 62. At the same time, the second holding mechanism 82 is moved to the
first chamber 61. In step S12, second coil spring 1 is set to the second holding mechanism
82.
[0045] In step S13, in the second chamber 62, the first coil spring 1 in the compressed
state is rotated (turns on its axis) by the rotation mechanism 100 and shot peening
is performed. That is, the first projection unit 55 and the second projection unit
56 moving vertically project shots SH2 to the first coil spring 1. The shot peening
is performed while the stress is applied to the coil spring 1, and thus, a compressive
residual stress which is effective to increase the durability of the coil spring 1
can be produced in a surface portion of the coil spring 1.
[0046] In step S14, the turntable 79 rotates 180° in a second direction. Thus, the coil
spring 1 held by the first holding mechanism 81 is returned to the first chamber 61.
Furthermore, the coil spring 1 held by the second holding mechanism 82 is sent to
the second chamber 62.
[0047] In step S15, the upper side holder 81b of the first holding mechanism 81 rises, and
the first coil spring 1 held by the first holding mechanism 81 is taken by the robot
21. The first holding mechanism 81 becomes empty, and the robot 21 sets third coil
spring 1 thereto. The upper side holder 81b descends to compress the coil spring 1.
[0048] In step S16, in the second chamber 62, the second coil spring 1 in the compressed
state is rotated (turns on its axis) by the rotation mechanism 100 and shot peening
is performed. That is, the first projection unit 55 and the second projection unit
56 moving vertically project shots SH2 to the second coil spring 1.
[0049] In step S17, the turntable 79 rotates 180° again in the first direction. Thus, the
coil spring 1 held by the first holding mechanism 81 is sent to the second chamber
62 and the second holding mechanism 82 is returned to the first chamber 61. The upper
side holder 82b of the second holding mechanism 82 rises, and then, the coil spring
1 held by the second holding mechanism 82 is taken by the robot 21. Next coil spring
1 is set by the robot 21 into the second holding mechanism 82 in the empty state.
After that, the upper side holder 82b descends to compress the coil spring 1. A series
of steps S10 to S17 is repeated by the number of coil springs 1 (N times), and the
shot peening of all coil springs 1 is completed.
[0050] FIG. 11 is a graph schematically showing an example of a chronological change of
load (relationship between time and load) in warm stress shot peening performed by
the shot peening device 50. For example, the shot peening device 50 performs the warm
stress shot peening to the coil spring 1 held by the first holding mechanism 81, the
coil spring 1 is compressed by the pressure mechanism 93. Between time t0 and t1 is
an insensible zone of the load cell 96, and thus, the load is not detected. When the
coil spring 1 is further compressed over the insensible zone, the load detected by
the load cell 96 increases from Z1 to Z2. At time t2, the load reaches Z2 which is
a target load, the pressure mechanism 93 is stopped. Then, the warm stress shot peening
(projection of shots SH2) is started at time t3 while the compression (compression
stroke) of the coil spring 1 is kept constant. The warm stress shot peening is performed
until time t4 lapses.
[0051] When the compressive residual stress is produced in the coil spring 1 by the warm
stress shot peening, the load tends to slightly increase by the compressive residual
stress as shown in FIG. 11 with single-dotted line m1. However, a permanent set in
fatigue occurs in the coil spring 1 which is compressed in the warm range, and thus,
the load decreases as shown with dotted line m2 with some exaggeration. Thus, the
load as a whole tends to slightly decrease as shown with solid line m3. The load as
a whole (solid line m3) is determined a balance of the load increased by the occurrence
of the compressive residual stress (line m1) and the load decreased by the permanent
set in fatigue in the coil spring 1 (line m2). Thus, the load as a whole (line m3)
may possibly be increased.
[0052] In the shot peening device 50 of the present embodiment, the load detected by the
load cells 96 and 97 during the warm stress shot peening is constantly monitored by
the controller 98. The information related to the detected load is displayed in the
display 112. At the same time, the information is stored in a memory of the information
processor 110 or in a storage medium 114. The information (a chronological change
of load and the like) stored in the storage medium 114 or the like can be referred
to anytime if necessary. If the detected change of the load is within an acceptable
range, it is determined that the warm stress shot peening is performed properly while
a certain load is applied to the coil spring.
[0053] As explained above, the data related to chronological change of load are stored in
the internal memory of the information processor 110 or the storage medium 114 during
the warm stress shot peening is performed by the shot peening device 50. This process
proves that the warm stress shot peening to the coil spring is performed properly,
that is, the quality of coil spring.
[0054] A permanent set in fatigue of the coil spring during the shot peening may be a problem.
In that case, as shown in FIG. 11 with two-dotted line m4, the signals output from
the load cells 96 and 97 are sent back to the pressure mechanism 93 such that the
load during the warm stress shot peening can be constant. Then, the presser units
94 and 95 are driven in the real time to change the stroke of compression, and thus,
the warm stress shot peening can be substantially performed in the constant compression
load.
[0055] FIG. 12 is a graph schematically showing another example of a change of load occurring
during the warm stress shot peening. As shown in FIG. 12 with solid line m5, the load
may suddenly drops at time t5 to be out of the acceptable range (threshold value).
In that case, the coil spring 1 may possibly be dismounted from the first holding
mechanism 81 or the second holding mechanism 82 during the shot peening. Thus, if
such a steep drop of load is recognized, it is determined that the warm stress shot
peening is not performed properly, and the coil spring is handled as a defective.
[0056] Furthermore, as shown in FIG. 12 with dotted line m6, if the load changes periodically
during the shot peening, the coil spring 1 may possibly be held unstably. If such
a change in load is recognized, it is determined that the warm stress shot peening
is not performed properly, and the coil spring is handled as a defective.
Industrial Applicability
[0057] When the present invention is achieved, models, structures, and arrangement of the
elements of the shot peening device can be arbitrarily changed. For example, the controller
processing the signals output from the load cells may be a personal computer or may
be an information processor storing computer program developed specifically for the
shot peening device. Furthermore, a load detector other than the load cell may be
used.
Reference Signs List
[0058] 1: Coil spring, 1a, 1b: End turn portion, 2: Wire, 10: First shot peening device,
50: Second shot peening device, 52: Turntable mechanism, 55: First projection unit,
56: Second projection unit, 57: Projection mechanism, 61: First chamber, 62: Second
chamber, 79: Turntable, 80: Revolution mechanism, 81: First holding mechanism, 82:
Second holding mechanism, 93: Pressure mechanism, 94, 95: Pressure unit, 96, 97: Load
cell (load detector), 98: Controller, 100: Rotation mechanism, 110: Information processor,
111: Input device, 112: Display, X1: Revolution axis, X2, X3: Rotation axis
1. A shot peening device
characterized by comprising:
a turntable mechanism (52) including a turntable (79) which rotates around a revolution
axis (X1);
a revolution mechanism (80) which rotates the turntable mechanism (52);
a holding mechanism (81, 82) which holds a lower end turn portion (la) and an upper
end turn portion (1b) of a coil spring (1) while the coil spring (1) is kept standing
and moves around the revolution axis (X1) with the turntable (79);
a rotation mechanism (100) which rotates the holding mechanism (81, 82) around a rotation
axis (X2, X3) ;
a pressure mechanism (93) which compresses the coil spring (1) in a state where the
coil spring (1) is held by the holding mechanism (81, 82);
a load detector which detects a load applied to the coil spring (1) by the pressure
mechanism (93);
a projection mechanism (57) which projects a shot to the compressed coil spring (1);
and
a controller (98) which detects a change in the load based on a signal output from
the load detector.
2. The shot peening device of Claim 1,
characterized in that the load detector is a load cell (96, 97) disposed in a load transfer path between
the pressure mechanism (93) and the holding mechanism (81, 82) .
3. The shot peening device of Claim 1 or 2,
characterized in that the controller (98) includes means for storing a chronological change of the load.
4. The shot peening device of Claim 1,
characterized in that the controller (98) includes a display (112) which displays a chronological change
of the load.
5. The shot peening device of Claim 2,
characterized in that the controller (98) includes a display (112) which displays a chronological change
of the load.
6. The shot peening device of Claim 3 according to any one of Claims 1 to 3, characterized in that the controller (98) includes a display (112) which displays a chronological change
of the load.
7. The shot peening device of Claim 1 or 2,
wherein the controller (98) includes means for notifying that the load becomes out
of an acceptable range while the projection mechanism (57) projects shots to the coil
spring (1).
8. The shot peening device of Claim 1 or 2,
characterized in that the controller (98) controls the pressure mechanism (93) such that the load becomes
a constant value while the projection mechanism (57) projects shots to the coil spring
(1).