Sizing apparatus for an internal grinder

Sizing apparatus for an internal grinder having an oscillation motor for oscillating a grinder wheel contacting the inner peripheral surface of an annular work piece, a sizing device to generate sizing signals for measuring the bore of the work piece, a measuring probe connected to the sizing device, a probe position sensor for sensing positions of the measuring probe in an axial direction of the bore of the work piece with reference to a rotation angle of a drive shaft of the oscillation motor, and a sizing signal sampler for sampling sizing signals when positions of the measuring probe are inside the bore of the work piece. The sizing apparatus for an internal grinder is capable of measuring the bore of the work piece during an oscillation machining despite the smallness of the bore and size in the axial direction of the work piece.

BACKGROUND OF THE INVENTION 
This invention relates to a sizing apparatus for an internal grinder 
whereby an oscillation machining of an inner peripheral surface of a work 
piece can be performed and a bore of the work piece can be measured by 
means of a sizing device during the oscillation machining. 
In FIG. 12, a spindle feeding table 10 (work table) is movable in the 
direction of Y and a wheel spindle table 12 is movable in the direction of 
X which is perpendicular to the Y direction. A work piece 14 is supported 
on the spindle feeding table 10 and a grinding wheel 16 is supported on 
the wheel spindle table 12. 
The grinding wheel 16 is fitted on the tip of a drive shaft of a spindle 
motor 18, and the inner peripheral surface of the work piece 14 is ground 
by the grinding wheel 16. 
As shown in FIG.. 13, the spindle feeding table 10 is driven in the Y 
direction by a feeding motor 24 by way of a ball type screw 20 and a speed 
reducer 22 which are disposed under the table 10, thereby actuating the 
grinding wheel 16 to grind the inner peripheral surface of the work piece 
14. 
As shown in FIG. 14, the wheel spindle table 12 is stroked and driven in 
the X direction by means of a traverse motor 26 and a ball type screw 28 
which are disposed under the table 12, and is vibrated by means of an 
eccentric cam 30 and an oscillation motor 32. 
The tips of a pair of forks 36 included in a sizing device 34 arranged on 
the spindle feeding table 10 are inserted into the work piece 14 from a 
side of the sizing device nearer the grinding wheel 16, and are pressed 
toward the inner peripheral surface of the work piece 14, as shown in FIG. 
15, 16, 17, 18 and 19. 
Positions of the tips of the forks 36 are measured by means of a sizing 
device 34, and the bore of the work piece 14 is obtained by virtue of the 
measured positions of the tips. 
As shown in FIG. 17 and 18, when the bore of the work piece 14 is small 
relative to the size of the grinding wheel 16 and, the grinding wheel 16 
and the tips of the forks 36 interfere with each other during an 
oscillation machining, the tips of the forks 36 are inserted into or 
removed from the work piece 14 by means of an interlocking mechanism 38 
relative to an oscillation of the wheel spindle table 12 interlocked 
therewith. 
In an example in FIG. 12, the sizing device 34 is movable in the direction 
of axis of the work piece 14 (X direction), and is driven forward and 
backward on a shaft 40 of the interlocking mechanism 38 relative to the 
work piece 14. 
The center portion of the shaft 40 is supported by a guide 42, and the base 
end of the shaft 40 is fixed on an interlocking member 44. 
The interlocking member 44 is driven by a drive member 46 provided on a 
side of the spindle motor 18 by way of a shaft 48, and is urged in the 
direction where the tips of the forks 36 are inserted into the work piece 
14 by means of a spring 50. The shaft 48 is supported by guides 51 and 53. 
A contactless switch 49 is disposed in proximity to the interlocking member 
44 on the spindle feeding table 10, and is turned on when the tips of the 
forks 36 touch the inner peripheral surface of the work piece 14 during an 
oscillation machining, as shown in FIG. 20. 
A switching signal for the contactless switch 49 is used as a size locking 
signal for sizing signal outputted from the sizing device 34. The sizing 
signal of the sizing device 34 is invalidated when the contactless switch 
49 is off, and is treated as effective only when the contactless switch 49 
is on. 
Therefore, the sizing signal corresponding to the bore of the work piece 14 
is intermittently obtained during an oscillation machining. 
Thus, the size locking signal which removes unnecessary portions of the 
sizing signal and effects only necessary portions thereof is turned on at 
a time t.sub.1 caused by a time of delay .DELTA.t after the tips of the 
forks have reached the end surface of the work piece at a time shown with 
(A) t.sub.0 and, is turned off at a time t.sub.3 before a time t.sub.5 
when the tips of the forks retreat from the end surface of the work piece 
14, in the case that the wheel spindle table 12 moves at a speed whose 
oscillation cycle is extremely low, as shown in FIG. 20. 
To the contrary, in the case that the wheel spindle table 12 moves at a 
speed whose oscillation cycle is extremely high, a delay time .DELTA.t is 
substantially increased to an non-negligible degree relative to the 
oscillation cycle, thereby resulting in a delay in a time t.sub.4 for 
turning off the size locking signal. 
Namely, a hysteresis always exists in the switching of the contactless 
switch 49, as shown in FIG. 20 (A), and a shut-off time t.sub.4 of the 
size locking signal moves toward a shut-off time t.sub.5 of the sizing 
signal by means of the sizing device 34. 
Therefore, when a length d of the work piece in the axial direction is 
extremely short, as shown in FIG. 20, a shut-off time t.sub.4 of the 
contactless switch 49 is delayed compared to a time t.sub.5 when the tips 
of the forks 36 retreat from the end surface of the work piece 14, whereby 
the bore of the work piece 14 cannot be measured. 
SUMMARY OF THE INVENTION 
This invention aims to overcome the above mentioned problems. It is an 
object of the invention to provide a sizing apparatus for an internal 
grinder which is capable of measuring a bore of a work 14 during an 
oscillation machining despite the smallness of the bore and size in the 
axial direction of the work piece 14. 
In order to achieve the objects described above, a sizing apparatus for an 
internal grinder according to the present invention comprises: a work 
table for supporting a work piece to be machined; a wheel spindle table 
movable in the axial direction of a bore of the work piece; an oscillation 
motor for oscillating by way of the wheel spindle table a grinding wheel 
contacting the inner peripheral surface of the work piece; a sizing device 
to generate sizing signals for measuring the bore of the work piece; a 
measuring probe connected to the sizing device, and contacting the inner 
peripheral surface of the work piece; an interlocking mechanism for 
inserting or removing the measuring probe of the sizing device into or 
from the work piece by interlocking the wheel spindle table relative to 
oscillations of the wheel spindle table; a probe position sensing means 
for sensing positions of the measuring probe of the sizing device in an 
axial direction of the bore of the work piece with reference to a rotation 
angle of a drive shaft of the oscillation motor; and a sizing signal 
sampling means for sampling sizing signals when position of the measuring 
probe sensed by the probe position sensing means are inside the bore of 
the work piece. 
In an internal grinder according to the present invention, positions of the 
measuring probe of the sizing device are detected with reference to a 
rotation angle of the drive shaft of the oscillation motor for vibrating 
the grinding wheel by way of the wheel spindle table. Then, a sizing 
signal is treated as effective only during a period of time the measuring 
probe is confirmed to be contacting the inner peripheral surface of the 
work piece in the detected position.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
A preferred embodiment of a sizing apparatus for an internal grinder 
according to the present invention will now be described with reference to 
the accompanying drawings. 
FIG. 1 shows a block diagram of an internal grinder according to one 
embodiment of the present invention. FIG. 2 shows a plan view of the 
internal grinder according to the embodiment, wherein explanations of 
identically referenced members as those in a conventional internal grinder 
shown in FIG. 12 are eliminated. 
In place of the contactless switch 49, a sensor 52 for sensing a rotation 
angle of the drive shaft of the oscillation motor 32 is employed in this 
embodiment as shown in FIG. 4. 
Similar to the oscillation motor 32, a feeding motor 24 and a traverse 
motor 26 are provided with sensors 54 and 56 for sensing a rotation angle 
of these drive shafts, respectively as shown in FIG. 3. Sensing pulses of 
the sensor 54, 56 and 52 are fed to a feeding control; circuit 58, a 
traverse control circuit 60 and an oscillation control circuit 62 for 
controlling the feeding motor 24, traverse motor 26 and oscillation motor 
32, respectively. 
A sizing signal obtained with the sizing device 34 is fed to a size 
measuring circuit 64, and a value showing a size of the bore of the work 
piece 14 is fed to a sizing signal input circuit 66 from the size 
measuring circuit 64 all the time. 
The size signal input circuit 66, feeding control circuit 58, traverse 
control circuit 60 and oscillation control circuit 62 are connected to a 
bus 68, and the bus 68 is connected to an MPU 70, a ROM 72 and a RAM 74. 
An I/O interface 76 and a console interface 78 are also connected to the 
bus 68. A sequencer and external switches are connected to the I/O 
interface 76, and a console 80 is connected to the console interface 78. 
An interrupt signal is fed to the MPU 70 from the oscillation circuit 62 
and the traverse control circuit 60, and a size locking command is given 
to the sizing signal input circuit 66 from the MPU 70 in correspondence 
with the size locking signal previously described. 
In FIG. 5, a flow chart of a general processing performed by the MPU 70 is 
shown. In this flow chart, a serial processing is repeatedly performed 
after an initial processing (step 200) with the MPU 70, which processing 
comprises: a setting input reception routine (step 202) for the console 
80, an external input reception routine (step 204), a size locking routine 
(step 206), a feeding control routine (step 208), a traverse control 
routine (step 210), and an oscillation control routine (step 212). 
In FIG. 6, the external input reception routine (204) is shown, wherein a 
command given from the sequencer and external switches is initially read 
in (step 300). 
When the bore of the work piece 14 is confirmed to be measured during an 
oscillation machining (YES in step 302), a size locking flag is set (step 
304), thereby setting a size locking mode (step 306). When such a 
measuring is not performed (NO in step 302), the size locking flag is 
reset (step 308). 
FIG. 7 shows the size locking routine (step 206), wherein the size locking 
flag is judged whether or not it is set (step 400). When the size locking 
flag is not set (NO in step 400), a size locking interrupt flag is reset 
(step 402). 
When the size locking flag is set (YES in step 400), the size locking mode 
already set is judged if it is an oscillation size locking mode or a 
traverse size locking mode (step 404). In the case of the oscillation size 
locking mode, an oscillation size locking position is set in the 
oscillation control circuit 62, and in the case of the traverse size 
locking mode, a traverse size locking position is set in the traverse 
control circuit 60 (step 406 and 408), whereby the size locking interrupt 
flag is set (step 410). 
FIG. 8 shows the feeding control routine (step 208). In this processing, a 
change in flags for a speed command and a position command are confirmed 
to be set (YES in step 500), processings for controlling the feeding motor 
24 are performed in correspondence with these flags (step 502). 
Next, in setting processings (step 406 and 408) of the size locking 
positions in the size locking routine (step 206), the oscillation size 
locking position is set in the oscillation control circuit 62 and, the 
traverse size locking position is set in the traverse size control circuit 
60. When the drive shafts of the oscillation motor 32 and the traverse 
motor 26 are rotated and brought to the oscillation size locking position 
and traverse size locking position, the interrupt signal is fed to the MPU 
70 from the oscillation control circuit 62 and the traverse control 
circuit 60. 
FIG. 9 shows an interrupt processing which is started by the interrupt 
signal. When the size locking interrupt flag is confirmed to be set (step 
600), the size locking command is output into the sizing signal input 
circuit 66, and a value (the bore of the work piece 14) measured by the 
size measuring circuit 64 is read in (step 602) by way of the sizing 
signal input circuit 66, thereby setting flags for changing commands of 
feeding speed, positioning or the like (step 604). 
FIG. 10 shows functions to measure the bore of the work piece during an 
oscillation machining. As shown in (A) and (B), during a period of time 
the tips of the forks 36 are contacting the inner peripheral surface of 
the work piece 14, the size locking command which is depicted in FIG. 10 
(C) will be generated. 
This size locking command is set with an external input in the size locking 
routine (step 206); therefore, the setting is arbitrarily made. 
The size locking command is generated with reference to a sensing pulse fed 
by the sensor 52 of the oscillation motor 32. As a result, a value of the 
bore of the work piece 14 is sampled without a delay of response at a time 
which is arbitrarily set. 
In FIG. 11, functions when the traverse size locking mode is selected are 
described. In this mode, the inner peripheral surface of the work piece 14 
is ground by stroking of the grinding wheel 16 by means of the traverse 
motor 26, as shown in FIG. 11 (D). 
The size locking command is generated when setting positions a, b and c in 
FIG. 11 (D) during a period of time the tips of the forks are contacting 
the inner peripheral surface of the work piece 14. The positions a, b and 
c are also set arbitrarily with external inputs (step 408). 
As have been described above, in an internal grinder according to the 
present invention, the bore of the work piece 14 can be measured during an 
oscillation machining despite the smallness of the work piece 14 in size 
in the axial direction thereof, since the bore of the work piece 14 can 
measured with reference to the sensing pulse of the sensor 52 for sensing 
a rotation angle of the drive shaft of the oscillation motor 32 and since 
an encoder or the like having an accuracy higher than that of the 
conventional contactless switch 49 by two figures can be employed. 
In a sizing apparatus for an internal grinder according to the present 
invention, quality control over products to be manufactured therewith or 
the like can be performed accurately and simultaneously with a machining 
of the products. 
As have been described above, in a sizing apparatus for an internal grinder 
according to the present invention, the bore of a work piece can be 
measured during an oscillation machining despite the smallness of the work 
piece in size in the axial direction thereof, since a sizing signal can be 
treated as effective when tips of forks are confirmed to be contacting the 
inner peripheral surface of the work piece after positions of the tips 
having been sensed with reference to a rotation angle of the drive shaft 
of an oscillation motor.