Method for press fitting of a press fitting body and a press fitting apparatus having a linear gauge for the press fitting body

A method and an apparatus for press fitting characterized in permitting the simultaneous measurement of a press fitting body with the press fitting, and characterized in improving the accuracy of the press fitting. The method comprises the steps of: temporarily press fitting a press fitting body (8) from the top of a press fitted part of a press fitted member (20), located at a prespecified height with respect to the press fitted part, such that a ball screw shaft of a ball screw is moved downward by means of a servo motor and, consequently, the body (8) is press fitted to the press fitted part at a prespecified length; executing a zero adjustment of a linear gauge and a load cell, wherein the linear gauge is composed such that a measuring member (36) is in contact with a top end of a measured member (30) which moves together with the body (8), and the load cell is composed so as to measure a press fitting force of the body (8); constant size press fitting executed to the member (20) of the body ( 8) at a prespecified length; differential press fitting, executed in the case where the measured results, the measured results of the linear gauge and the load cell at the time when the constant size press fitting process is terminated, are in prespecified ranges, and wherein the body (8) is press fitted to the member (20) according to the difference between the results and an objective length; and determining, whether or not the press fitted length, set by the differential press fitting step, is equal to the specified press fitting length.

FIELD OF THE INVENTION 
The present invention relates to a method for press fitting of a press 
fitting body and a press fitting apparatus having a linear gauge for the 
press fitting body, especially for that utilized for a press fitting 
apparatus for press fitting an armature shaft to an armature core of a 
motor of an automobile. 
BACKGROUND ART 
Conventionally, an armature core of a motor has been press fitted to an 
armature shaft by means of a presser having a hydraulic cylinder. 
In the case where a portion that is pushed out and projecting from the 
armature core (i.e. an one end of the armature shaft in the press fitting 
direction) is required to have a specific length, a stopper should be 
provided at a position within a prespecified distance from the touching 
surface between the armature core and a jig holding the armature. 
Therefore, the end of the projecting armature shaft is stopped by the 
stopper so that the relative position of the armature core and the 
armature shaft can be set at the desired distance. The above method is 
called a constant size press fitting method. 
However, in the above method, it is difficult to exchange the stopper when 
various relative positions are required for a plurality of armature cores 
and armature shafts, and when various types of products are to be 
manufactured. Furthermore, when the stopper is worn, the press fitted 
length of the armature shaft with respect to the armature core will become 
variable so that the entire armature assembly will be variable and 
consequently the reliability of the product will not be maintained. In 
addition, when the armature shaft is pushed out by the presser and 
collides with the worn stopper, the armature shaft will be chewed by the 
presser and the stopper, and the hydraulic pressure of the driving 
cylinder that is applied. Therefore, the thin shaft of the press fitting 
body may be bent during this process. 
SUMMARY OF THE INVENTION 
Accordingly, it is a primary objective of the present invention to provide 
a method for press fitting of a press fitting body and press fitting 
apparatus having a linear gauge for the press fitting body, wherein the 
press fitted length of the press fitted member (i.e. the armature shaft) 
can be measured at the same time as the press fitting process. 
It is another objective of the present invention to obtain high accuracy in 
the press fitting so as to improve the reliability of the products. 
A more specific objective of the present invention is to prevent the press 
fitting body from bending even when the press fitting body is a 
comparatively thin one. 
In a first aspect of the present invention, there is provided a method for 
press fitting comprising the steps of: 
(a) temporarily press fitting a press fitting body from above a press 
fitted part of a press fitted member, located at a prespecified height to 
the press fitted part, such that a ball screw shaft of a ball screw is 
moved downward by means of a servo motor and such that the press fitting 
body is press fitted to the press fitted part at a prespecified length; 
(b) executing a zero adjustment of a linear gauge and a load cell, wherein 
the linear gauge is composed such that a measuring member is in contact 
with a top end of a measured member which moves together with the press 
fitting body, and the load cell is composed so as to measure a press 
fitting force of the press fitting body; 
(c) constant size press fitting, further executed to the the press fitted 
member, of the press fitting body a prespecified length; 
(d) differential press fitting, executed in the case where the measured 
results, the measured results of the linear gauge and those of the load 
cell at the time when the constant size press fitting process is 
terminated, are within prespecified ranges, wherein the press fitting body 
is press fitted to the press fitted member according to a difference 
between the measured results and a specified press fitting length so that 
consequently the specified press fitting length of the press fitting body 
with respect to the press fitted member can be attained; and 
(e) determining, whether or not the press fitted length, set by the 
differential press fitting step, equals the specified press fitting length 
.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Further objectives and advantages of the present invention will be apparent 
from the following description, with reference to the accompanying 
drawings wherein a preferred embodiment of the present invention is 
clearly shown. 
FIG. 4 shows a shaft processing and press fitting apparatus of the armature 
core according to a preferred embodiment of the present invention. The 
apparatus consists mainly of a base plate 1, a shaft stocker 2, a sub 
index 3, a length measuring part 4, a knurller 5, a main index 6, an 
armature core supplier 21, a temporary shaft inserter 22, a final press 
fitter 7 of the shaft, and an armature core discharger 81. 
The shaft stocker 2, is box-like in shape, disposed above the base plate 1 
as shown in FIG. 4, and stores a lot of round-bar shaped armature shafts 8 
(i.e. the press fitting body, see FIG. 1) which are arranged horizontally. 
Similar to the conventional technique, a shaft supplying hole (not shown) 
in the bottom of the shaft stocker 2, is provided so shown) in the bottom 
of the shaft stocker 2, is provided so as to intermittently supply the 
armature shaft 8 stocked in the shaft stocker 2, to the subindex 3. 
The subindex 3 provided on the turn table 11 is shaped such as the 
character "#" consists of two pair of parallel arms 12 which overhang from 
four orthogonal sides of the regular octagonal-shaped turn table 11. At 
every "90" degrees, the subindex 3 is rotatable around the shaft 13 and is 
vertically movable along the base plate 1. The arms 12, which have the 
same shape, are formed with "V"-shaped recesses at the ends so as to allow 
the armature shaft 8 to be inlayed therein. The subindex 3, adjoining the 
shaft stocker 2, receives the armature shaft 8 from the shaft stocker 2 at 
the recesses of arm 12 so as to inlay the shaft 8 in the recesses. 
The length measuring part 4 is provided adjacent to a specific end of a 
central axis B, which orthogonally intersects a central axis A that 
connects the center of the shaft stocker 2 and the shaft 13 of the 
subindex 3. The length measuring part 4 receives the armature shaft 8 from 
the arm 12 of the subindex 3 by means of a feeding mechanism (not shown), 
and measures the length of the armature shaft 8 by means of a measuring 
means (not shown) provided in the length measuring part 4. Then, the 
measured armature shaft 8 is carried again to the subindex 3 by means of 
the feeding mechanism and inlayed into the recess on the arm 12. Needless 
to say, the length measuring part 4 which can be embodied by various 
conventional techniques is not included in the present invention. The 
subindex 3 is stopped when the arm 12 positions are either parallel or 
orthogonal to the central axis A. 
In the opposite area of the shaft stocker 2, a knurller 5 is located 
proximity to the subindex 3. The knurller 5 contains a cylinder mechanism 
15 and a stopper 16 which is separated from and faces to the cylinder 
mechanism 15. The cylinder mechanism 15 and stopper 16 are parallel to the 
central axis B. More specifically, when the arm 12 is parallel to the 
central axis A, the cylinder mechanism 15 will be adjacent to the length 
measuring part 4, while the stopper 16 will be on the opposite side. 
Though they are not shown, the knurller 5 also contains a hydraulic 
cylinder assembly and a presser having lower and upper dies. The presser 
presses, by means of the upper and lower dies, and knurls the armature 
shaft 8 when the shaft 8 is lightly fixed between the cylinder mechanism 
15 and the stopper 16, and is set in the lower die such that one end of 
the shaft 8 is in contact with the stopper 16, and another end of the 
shaft 8 is lightly pushed by the cylinder mechanism 15 wherein the pushing 
force of the cylinder mechanism 15 is only sufficient for supporting the 
shaft 8. 
At the opposite side of the length measuring part 4 of the subindex 3, the 
main index 6 is rotatable around the shaft 18. The main index 6 contains a 
turn table 19 which has four core installers 19a which are shaped to fit 
the the armature core 20 (press fitted member) therein, and are located at 
four positions dividing the table 19 into quarters. The main index 6 will 
be stopped when the armature core 20, fitted on the index 6, is carried to 
either of four stations. Two of those stations, the final press fitter 7 
of the shaft and the armature core discharger 81, are located on a central 
axis C that passes the shaft 18 and is parallel to the central axis A. The 
other two stations, the armature core supplier 21 and the temporary shaft 
inserter 22, are located on a central axis D that orthogonally cross the 
axis C at the shaft 18. Towards the final press fitter 7, the shaft 18 is 
separated at a prespecified distance from the central axis B of the 
subindex 3. 
The armature core supplier 21 carries the armature core 20 to the core 
fitting position of the turn table 19 and fits the core 20 at the position 
by means of a core supplier 25, which is adjacent to the supplier 21 and 
consists of conventional feeding mechanisms. 
FIG. 5 shows the column-shaped armature core 20 having a shaft hole through 
the center line of the column so as to be inserted into the armature shaft 
8, and a plurality ("8" in this embodiment) of grooves 8a that are 
equidistant from and parallel to the center axis of the column. 
The temporary shaft inserter 22 is provided with a temporary shaft 
insertion mechanism (not shown) so that the inserter 22 receives the 
armature shaft 8 from the arm 12 which is stopped adjacent to the inserter 
22 in a horizontal position. Then, the inserter 22 turns the armature 
shaft 8 to a vertical position, and temporarily inserts a prespecified 
length of the shaft into the center shaft hole of the armature core 20 on 
the turn table 19 at the inserter 22. 
The final press fitter 7 is composed as follows. 
The support plate 23 is suspended from the lower surface of the base plate 
1 and a board-shaped guide element 24 is attached to the center of the 
support plate 23. The cylinder mechanism 26 is attached to a lower part of 
support plate 23 via a bracket 125 and the position rod 23 is located in 
the upper portion of the cylinder mechanism. The piston rod 27 is 
connected to the cylinder mechanism by means of a joint 28, and a load 
receiving member 29, which moves vertically along the guide element 24. 
The base plate 29a of the load receiving member 29 is provided with a 
slider 38 which can slide horizontally. Both ends of the slider 38 have 
the same length and are fitted with two measured members 30 protruding 
upward from the slider 38. The top faces of the members 30 are flat and 
have the same altitude. The members 30 are connected with a cylinder 
mechanism 31 located along the horizontal axis on the load receiving 
member 29, so that the members 30 are horizontally movable. 
The measured members 30 are exchangeable with other pairs of rod-shaped 
measured members (not shown), referred to as exchange measured members 
which have a projection with a length that is different from the load 
receiving member 29. In place of the measured members 30, the exchange 
measured members may be fitted with the load receiving member 29. 
Furthermore, the bottom face of the load receiving member 29 is fitted 
with a stopper 33 which contacts a shock absorber 32 provided on the top 
face of the bracket 125. 
The support 23 is horizontally fastened to a bracket-shaped outer guide 34 
in a manner such that when the load receiving member 29 is raised, the 
bottom face of the outer guide 34 will touch the top faces of the measured 
members 30. Furthermore, because the outer guide 34 has a bracket-shape, 
the vertical movement of a connection board 29b of the load receiving 
member 29 will be possible. As shown in FIG. 1, the right side of the 
upper portion of the guide 34 is fitted with a linear gauge 35. The linear 
gauge 35 is provided with a measuring member 36 which is loosely inserted 
to a hole (not shown) which passes through the outer guide 34. In the 
playing condition, the measuring member 36 contacts the top face of one of 
the measured members 30 with an appropriate pressure. Therefore, the 
gravitating length of the measured member 30 is measured by the linear 
gauge 35. 
Meanwhile, the top face of the base plate 1 is provided with a 
cylinder-shaped pedestal 37 located on the same axis of the piston rod 27 
of the cylinder mechanism 26. Both the top and lower end of the pedestal 
37 is referred to as a minor diameter portion 37a and a larger diameter 
portion 37b, respectively. The minor diameter portion 37a is penetrated by 
a shaft catching rod 40 (i.e. stopper) made of a carbide punching 
material. On the top end of the shaft catching rod 40, is a flat shaft 
catching surface 40a (i.e. press fitting body catching surface). The 
bottom end of the shaft catching rod 40 is connected coaxially with an 
exclusive shaft 42 via a coupling 42a. 
The exclusive shaft 42, loosely penetrates a through hole formed in the 
base plate 1, and is fitted to a rod joint 41 which is fastened to the top 
end of the connection board 29b such that the piston rod 27 of the 
cylinder mechanism 26, the exclusive shaft 42, and the shaft catching rod 
40 are coaxial. In FIG. 1, the numeral 43 designates a proximity switch, 
and the numeral 44 designates a shock absorber. 
In FIG. 2, a gate-shaped bracket 53, consists mainly of two support boards 
51 and a top board 52 fitted on the support boards 51, which, in turn, is 
fitted on the upper surface of base plate 1. The top board 52 is 
perforated at a top hole on which a bearing 55 is fixed by a flange 54 
which is located near the upper surface of the top board 52. The bearing 
55 supports a ball screw 56. As shown in FIG. 2, the ball screw 56 is 
provided with a shaft 59 which moves vertically along the shaft axis in 
response to the rotation of a cylinder 58 (i.e. the rotation means). 
Cylinder 58 is supported at a flange 57 by the bearing 55 and can rotate 
horizontally but not vertically, with respect to the shaft axis. The 
bottom face of the flange 57 is fixed with a pulley 60 which is coaxial 
with the ball screw shaft 59. The top end outer surface of the ball screw 
shaft 59 is connected with a proximity switch 61. 
FIG. 3 shows the details of the upper portion of the bracket 53 fitted with 
a servo motor 62 which is adjacent to the bearing 55 such that the 
rotation axis 63 of the motor 62 is projecting downward into the base 
plate 1. The rotation axis 63 is fitted with a pulley 64. The pulley 64 
and the pulley 60 in the lower portion of the bearing 55 are turned with a 
belt 65 so as to transfer the revolution of the rotation axis 63 of the 
servo motor 62 to the ball screw 56. 
The support boards 51 of the bracket 53 are provided with guide rails 66. 
The bottom portion of the ball screw shaft 59 is fitted with a connection 
member 67 which is fitted with a vertical slider 68 (i.e. movable body). 
The sides of the vertical slider 68 are provided with fitting members 69 
that are slidable, and with the guide rails 66 that are vertically 
movable. The fitting member 69 face towards the support boards 51 to 
prevent the rotation of the ball screw shaft 59. The vertical slider 68 is 
hollow and a load cell 70 is set at a prespecified position in the 
vertical slider 68. The vertical slider 68 is connected with a pressing 
shaft 72 via a downward guide pipe 71 having a flange. The pressing shaft 
72 is coaxial with the exclusive shaft 42. The guide pipe 71 has a 
shoulder 71a on which an upper flange 72a of the pressing shaft 72 is 
engaged, so that the load cell 70 can be pressed by the top end of the 
pressing shaft 72. 
Furthermore, the bottom of the pressing shaft 72 is fitted with a shaft 
guide 73 that is perforated with a guide hole 73a and runs along the axis 
of the shaft guide 73. The armature shaft 8 can be inserted into the guide 
hole 73a. 
Four separate rods 74 are vertically inserted into the outer round portion 
of the vertical slider 68. The bottom ends of the rods 74 are connected 
with other rods in a connection board 75. The rods 74 loosely penetrate 
coil springs 76 laid between the flange of the guide pipe 71 and the 
connection board 75. The connection board 75 can be move down to contact 
the armature core 20 fitted on the core installer 19a of the turn table 
19. 
The armature core 20, fitted to the core installer 19a of the turn table 
19, is discharged by the core discharger 82 adjoining the armature core 
discharger 81 and consists of conventional feeding mechanisms. 
The armature core supplier 21, the subindex 3, the main index 6, the 
temporary shaft inserter 22, the final press fitter 7 of the shaft, and 
the armature core discharger 81 contain drivers which are appropriately 
controlled by a sequence controller (not shown). 
Next, a description will be made of a press fitting method of the press 
fitting body and an operation of the press fitting apparatus which has the 
linear gauge and is based on the above-described apparatus according to 
the preferred embodiment of the present invention. 
First, in preparation for the press fitting of the armature shaft 8 to the 
armature core 20, a plurality of the armature shaft 8 are arranged 
horizontally and stocked in the shaft stocker 2. Next, the press fitting 
apparatus with the linear gauge is provided with the final press fitter 7 
of the shaft, and the cylinder mechanism 26 is shortened so that the shaft 
catching rod 40 is carried downward from the top face of the pedestal 37 
via the joint 28, the load receiving member 29, the connection board 29b, 
the exclusive shaft 42, and the coupling 42a. Therefore, the measuring 
member 36 of the linear gauge 35 is also carried downward. The pressing 
shaft 72 is then raised by driving the servo motor 62 via the ball screw 
56 so that when the armature core 20 reaches the final press fitter 7 of 
the shaft, the armature shaft 8, temporarily fitted on the armature core 
20, is prevented from contacting the connection board 25 and the rods 74. 
Next, when the apparatus is driven in the configuration shown in FIG. 4, 
the armature shafts 8 are sequentially supplied one by one, at an 
appropriate interval, from the bottom of the shaft stocker 2 to the 
subindex 3. The armature shafts 8 are then placed into the "V"-shaped 
recess of the arm 12 and are supported by the arm 12. The subindex 3, 
viewed from top, then rotates 90 degrees clockwise, and the arm 12 
supporting the armature shaft 8 is carried to the length measuring part 4 
and stopped. 
Then, the arm 12, adjoining the length measuring part 4, passes the 
armature shaft 8 to the the part 4. Then, the length of the armature shaft 
8 is measured by the length measuring part 4. 
In the case where the measured results of the armature shaft 8 is 
acceptable, the armature shaft 8 is returned from the length measuring 
part 4 to the subindex 3 which further rotates 90 degrees and stops at the 
knurller 5. However, when the armature shaft 8 is determined to be 
inferior in the length measuring part 4, the armature shaft 8 is not 
passed from the length measuring part 4 to subindex 3. In this case, the 
subindex 3 further rotates 90 degrees, the arm 12 supporting the inferior 
armature shaft 8 is carried to the length measuring part 4, and the 
subindex 3 is stopped. 
When the arm 12 supporting the armature shaft 8 is stopped at the knurller 
5, the armature shaft 8 is passed from the arm 12 to the knurller 5 
wherein one end of the armature shaft 8 is contacted by the stopper 16, 
between the cylinder mechanism 15 and the stopper 16, while another end is 
pushed by the cylinder mechanism 15. The armature shaft 8 set in the lower 
press die. The armature shaft 8 which is fixed between the cylinder 
mechanism 15 and the stopper 16 is then pressed by the upper and lower 
dies so that the knurlling process is executed for the armature shaft 8. 
Then, the processed armature shaft 8 is returned to the arm 12 adjoining 
the knurller 5. 
Then, the subindex 3 further rotates 90 degrees in a clockwise direction, 
and the arm 12 supporting the knurlled and processed armature shaft 8 is 
stopped at a temporary shaft inserter which is adjacent to the part 
adjoining the temporary shaft inserter 22 of the main index 6. Meanwhile, 
the armature core 20 is fitted on the core fitting portion on the turn 
table 19 by the the core supplier 25, such that the central shaft hole of 
the core 20 is laid vertically in the armature core supplier 21. When the 
armature core 20 is fitted on the turn table 19, the main index 6, viewed 
from the upward of the turn table 19, rotates 90 degrees in a 
counter-clockwise direction (i.e. rotates in reverse with respect to the 
subindex 3). Then, the main index 6 is stopped when the armature core 20 
fitted therewith reaches the temporary shaft inserter 22. 
When the armature core 20, fitted with the turn table 19, reaches the 
temporary shaft inserter 22 so that the turn table 19 is stopped, the 
temporary shaft insertion mechanism (not shown) receives the armature 
shaft 8 in a horizontal position from the arm 12 of the subindex 3 and 
stops adjacent to the temporary shaft inserter 22. Then, the temporary 
shaft insertion mechanism maintains the armature shaft 8 in a vertical 
position, and temporarily inserts a prespecified length of the armature 
shaft 8 in a vertical position, into the center shaft hole of the armature 
core 20 at the temporary shaft inserter 22 on the turn table 19. 
Then, the subindex 3 rotates 90 degrees in the same direction, the main 
index 6 rotates 90 degrees counter-clockwise, the armature core 20 which 
is temporarily inserted with the armature shaft 8 reaches the final press 
fitter 7 of the shaft, and the turn table 19 is stopped. 
Then, utilizing the press fitting apparatus having the linear gauge, the 
armature shaft 8 is finally press fitted with the armature core 20. In 
this case, when the armature core 20, temporarily press fitted with the 
armature shaft 8, reaches the final press fitter 7 so that the turn table 
19 is stopped, the cylinder mechanism 26 is extended and the shaft 
catching rod 40 is raised to a prespecified position. Simultaneously, the 
measured members 30 are raised so that the top faces of the measured 
members 30 contact the bottom face of the outer guide 34 so that the 
measured members 30 are stopped. In this case, the measuring member 36 of 
the linear gauge 35, the bottom face of which touches the top face of 
measured members 30, also rises. Meanwhile, the armature shaft 8 is fed 
from the shaft stocker 2 to the arm 12 of the subindex 3 adjoining the 
shaft stocker 2. 
Next, referring to FIG. 6, a description will be made of the final press 
fitting of the the armature shaft 8 of the armature core 20 which is 
executed by the final press fitter 7. 
In step SP1, when the press fitting process of the servo motor starts, the 
cylinder mechanism 26 operates so that the rod 40 and the measured member 
30 are raised, and the measured member 30 contacts the measuring member 36 
as described above. 
Then, the process moves to step SP2 wherein the servo motor 62 is rotated, 
at prespecified times, at high-speed. As a result, a cylinder 58 of the 
ball screw 56 rotates via the pulleys 60, 64 and the belt 65. The vertical 
slider 68 moves downward, by a prespecified length, together with the ball 
screw shaft 59. The guide hole of the connection board 75 is penetrated 
with the armature shaft 8, and the armature core 20 is pressed against the 
core installer 19a of the turn table 19 via the coil springs 76 by means 
of the connection board 75. Consequently, the vertical slider 68 moves 
further downward, the armature shaft 8 is inserted into the guide hole 73a 
of the shaft guide 73, the bottom face of the pressing shaft 72 contacts 
the armature shaft 8, and the pressing shaft 72 is stopped when the 
armature shaft 8 is press fitted to the armature core 20. In this step and 
the following steps, the force applied to the core installer 19a is 
applied to the support 23 via the load cell pedestal 37. The process then 
moves to step SP3 wherein zero-adjustments of the linear gauge 35 and the 
load cell 70 are executed. 
In step SP4, the servo motor 62 is rotated at prespecified times at a 
low-speed, and the ball screw shaft 59 moves downward by a prespecified 
length. The armature shaft 8 is then press fitted to the armature core 20, 
at a prespecified length, in a low-speed by means of the pressing shaft 
72, and the servo motor 62 is stopped (see the conditions shown in FIGS. 1 
and 2). As a result, the flat shaft catching surface 40a of the shaft 
catching rod 40 is in contact with the bottom of the armature shaft 8, and 
the shaft catching rod 40, resisting the force applied by the cylinder 
mechanism 26, moves downward. Simultaneously, the load receiving member 
29, the measured member 30 and the measuring member 36, contacting the top 
face of the measured member 30, also move downward. 
The process then moves to step SP5 wherein the indicated values of the 
linear gauge 35 and that of the load cell 70 are read by the controller. 
In step SP6, the values of the load cell 70, read in step SP5, is compared 
with a prespecified value and is judged whether or not the value is 
appropriate. If the value is appropriate, the process moves to step SP7. 
However, if the value is not appropriate, the armature core 20 or the 
armature shaft 8 may be defective so that process moves to step SP9. 
In step SP7, a judgement is made as to whether or not the values of the 
linear gauge 35 are appropriate. If the values are appropriate, the 
process moves to step SP8. If the values are not appropriate, the armature 
shaft 8 may be defective and therefore the process moves to step SP9. 
In step SP8, a differential press fitting process is executed. The word 
"differential" means the difference between the press fitted length at 
that time when the constant size press fitting process is terminated, and 
a prespecified press fitting length to which the press fitting of the 
armature shaft 8 should be fitted. Specifically, the difference is 
calculated as the number of pulses to be fed to the servo motor 62. The 
servo motor 62 is operated at low-speed according to the number of the 
pulses, the ball screw shaft 59 is carried downward, and the armature 
shaft 8 is then press fitted to the armature core 20 with respect to the 
differential. According to the process described above, the armature shaft 
8 is press fitted to the armature core 20 that is highly accurate in 
measurement with a length projecting from the bottom face. The process 
then moves to step SP11. 
When the process moves to step SP9, the controller records the data 
indicating that the armature core 20, the armature shaft 8, or the press 
fitting process of the armature shaft 8 to the armature core 20 is 
inferior. Then, process moves to step SP10 wherein a total press fitted 
length from step SP2 to SP4 is calculated in order to return the vertical 
slider 68, the ball screw shaft 59 and the components therewith to their 
original positions. The total press fitted length can be obtained by 
summing the number of pulses generated by an encoder contained in the 
servo motor 62. The, process then moves to step SP14. 
When the process moves to step SP11 via SP8, the indicated value of the 
linear gauge 35 is reread. Then, utilizing the linear gauge 35, it is 
determined whether or not the press fitted length of the armature shaft 8 
with respect to the armature core 20 in the differential press fitting 
process, in step SP8, is equal to the specified press fitting length. If 
the press fitted length of the armature shaft 8 with respect to the 
armature core 20 does not equal to the objective press fitting length, the 
process them moves to step SP13 via, step SP12, wherein the controller 
records that the press fitted length of the armature shaft 8 to the 
armature core 20 is inferior; otherwise, the process directly moves to 
step SP13. 
In step SP13, the total press fitted length of the temporary press fitting 
process SP2, the constant-size press fitting process SP4, and the 
differential press fitting process SP8 is determined in order to return 
the vertical slider 68, the ball screw shift 59, and the components 
therewith to their original positions. As in step SP10, the total length 
is obtained by summing the number of the pulses generated by the servo 
motor 62 in the corresponding processes. The process then moves to step 
SP14. 
In step SP14, the cylinder mechanism 26 is shortened so that the measured 
members 30 are lowered and the measuring member 36 of the linear gauge 35 
is simultaneously lowered. 
Then, the process moves to step SP15 wherein the servo motor 62 is rotated 
in reverse, the number of the rotations that are equivalent to the number 
of the pulses determined in the steps SP10 and SP13. Then, the principal 
part of the press fitting operation is terminated and the apparatus is 
reset to the original starting position. 
Then, subindex 3 rotates an additional 90 degrees in the same direction and 
the main index 6 rotates 90 degrees counter-clockwise. The armature core 
20, press fitted with the armature shaft 8, reaches the armature core 
discharger 81, the turn table 19 stops, and the armature core 20 is 
discharged by means of the core discharger 82 from the turn table 19. The 
discharged armature core 20 is then fed to an inferior item selecting 
apparatus (not shown) so that the armature cores 20, which have been 
determined to be inferior in the steps SP9 and SP12, are picked up. 
Thereafter, the subindex 3 rotates 90 degrees in the same direction, the 
main index 6 rotates 90 degrees counter-clockwise, the turn table 19 is 
stopped, and the condition of the apparatus is initialized such that a new 
armature core 20 is fed to the turn table 19 by means of the armature core 
supplier 21. Hereafter, if required, the operation described above is 
repeated. 
The consecutive operation of the apparatus as described heretofore, 
according to the preferred embodiment of the present invention, which 
comprise feeding of the armature core 20 and the armature shaft 8, 
knurlling the armature shaft 8, press fitting of the armature shaft 8 to 
the armature core 20, and discharging the armature core 20 press fitted 
with the armature shaft 8, and are consecutively executed in one machine. 
Therefore, there is no need to manually determine the type of armature 
shaft, or to manually determine the press fitting direction. Consequently, 
the manual labor can be greatly reduced, and the misidentification of the 
type of armature shaft 8 or the press fitting direction can be eliminated. 
Furthermore, because the press fitted length can be measured 
simultaneously with the press fitting of the armature shaft 8 with respect 
to the armature core 20, the accuracy of press fitting can be improved by 
the cooperative operation of the servo motor 62 and the ball screw 56. 
More specifically, in most cases, the required accuracy of dimensions of 
the armature core 20 with respect to the armature shaft 8 is more 
stringent than those of the individual components, the armature core 20 
and the armature shaft 8. The preferred embodiment can guarantee the more 
stringent requirements and improve the reliability of the product. 
Furthermore, although the armature shaft 8 is worn by the ball screw 56 
and the cylinder mechanism 26, the force applied to the armature shaft 8 
is only sufficient for supporting the shaft 8. Consequently, the force is 
so weak that the possibility of bending the armature shaft 8 is 
eliminated. 
This invention may be practiced or embodied in still other ways without 
departing from the spirit or essential character thereof. For example, in 
the above embodiment, four arms are provided with the subindex 3 and the 
armature cores 20 are fitted at a plurality of positions on the outer 
surface of the main index 6 so as to divide the surface into quarters such 
that the subindex 3 and the main index 6 are stopped respectively at the 
four stations. However, if necessary, the number of the stations can be 
increased. 
Therefore, the preferred embodiment described herein is illustrative and 
not restrictive, the scope of the invention is indicated by the appended 
claims, and all the variations which fall within the scope of the claims 
are intended to be embraced therein.