Press machine stroke operation mechanism and operation control method therefor

The present invention provides a stroke operation mechanism which is incorporated in a single-structure press machine so that various types of stroke operations can easily be generated on the slide side, and a control method for controlling the stroke operation mechanism so as to cause the mechanism to exhibit various types of stroke operations. The press machine stroke operation mechanism has a driving system having a feed screw member disposed on a plane in parallel therewith, at least one pair of nut members screwed on the screw member and moved by rotation of the screw member so as to separate from and approach to each other, and a servomotor for supplying torques for normal and reverse rotations to the screw member; and a slide system having a slide member supported below the screw member at right angles therewith so as to be vertically slidable, and a transmission bar member having an upper end axially connected to the nut members and a lower end axially connected to the slide member. The rotational frequency and the rotational speed of the servomotor are controlled for controlling the position and speed of the slide member between the upper dead center and the lower dead center during the stroke motion of the slide member, which is caused by rotation of the motor.

BACKGROUND OF THE INVENTION 
The present invention relates to a press machine stroke operation mechanism 
comprising a servo motor and a link mechanism, and a method of controlling 
the position and speed of the stroke operation of the mechanism so that 
the press machine is operated in accordance with the working contents of 
the intended press work. 
Press machines using a servo motor as a driving source of a stroke 
operation mechanism are proposed in Japanese Patent Laid-Open Nos. 
62-252700, 62-296999 and 62-297000. A press machine using a link mechanism 
as a stroke operation mechanism is also known as a quick-return press or 
the like. 
However, the previously proposed press machines using a servo motor as a 
driving source are screw presses and are developed as single purpose 
machines for caulking. Thus such press machines are not intended to be 
used considering the pressure applied to a workpiece, the pressure speed 
or a position in a stroke where the pressure and speed are applied. 
Since the link mechanism of the known link press is also incorporated into 
a machine in order to simply quickly return a slide member, the same press 
mechanism cannot be used for press works having different work contents. 
However, if the way of applying the pressure and the pressure speed to a 
workpiece can be changed for working different workpieces by a single 
press machine, press machine makers need not to produce different machines 
according to work contents, and the user also need not to buy and install 
machines respectively required for different work contents. It is thus 
thought that an attempt can be made to significantly rationalize the press 
work from various viewpoints. 
SUMMARY OF THE INVENTION 
In consideration of the above point, an object of the present invention is 
to provide a stroke operation mechanism which is incorporated into a 
single structure press machine so that various types of stroke operations 
can easily be produced on the slide side, and a control method for causing 
the stroke operation mechanism to exhibit various stroke operation speeds. 
In order to achieve the object, a stroke operation mechanism of the present 
invention comprises a driving system comprising a feed screw member 
disposed on a plane in parallel therewith and provided with threads in 
different feed directions, at least one pair of nut members screwed on the 
screw member so as to be forwardly and backwardly moved in directions in 
which the nut members separate from and approach to each other by the 
rotation of the screw member, and a servomotor for selectively supplying 
torques for normal and reverse rotations to the screw member; and a slide 
system comprising a slide member supported below the screw member at right 
angles therewith so as to be vertically slidable, and a transmission bar 
member having an upper end portion axially connected to the nut members 
and a lower end portion axially connected to the slide member. 
The present invention also provides a method of controlling the press 
machine stroke operation mechanism comprising a driving system comprising 
a feed screw member disposed on a plane in parallel therewith, at least 
one pair of nut members screwed on the screw member so as to be forwardly 
and backwardly moved in directions in which the nut members separate from 
and approach to each other by the rotation of the screw member, and a 
servomotor for supplying torques for normal and reverse rotations to the 
screw member; and a slide system comprising a slide member supported below 
the screw member at right angles therewith so as to be vertically 
slidable, and a transmission bar member having an upper end portion 
axially connected to the nut members and a lower end portion axially 
connected to the slide member. In the control method, the rotational 
frequency and the rotational speed of the servomotor are controlled for 
controlling the position and the speed of the slide member between the top 
dead center and the bottom dead center during the stroke motion of the 
slide member, which is caused by rotation of the servomotor.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
A stroke operation mechanism and a control method therefor are described 
with reference to embodiments of the present invention. FIG. 1 is a front 
view showing a stroke operation mechanism according to an embodiment of 
the present invention, FIG. 2 is a side view showing an example of a press 
machine to which the stroke operation mechanism of the present invention 
shown in FIG. 1 is applied, and FIG. 3 is a block diagram showing an 
example of a control system for the stroke operation mechanism of the 
present invention shown in FIG. 1. 
In FIG. 1, reference numeral 1 denotes a feed screw having threads 1L and 
1R which are formed in the left and right sides thereof in opposite 
directions, the screw 1 being horizontally disposed. Reference numerals 
2a, 2b and 2c respectively denote bearings for supporting the both ends 
and an intermediate portion of the screw 1 where no thread is formed. 
Reference numeral 3 denotes a servo motor connected to the right end of 
the screw 1 shown in FIG. 1 through a joint 4. Reference numerals 5L and 
5R respectively denote left and right nut members which are screwed on the 
external threads 1L and 1R formed on the left and right sides of the screw 
1. Reference numeral 6 denotes a slide guide used for locking the nut 
members 5L and 5R, the projections 51 and 52 of the nut members 5L and 5R 
being supported by the guide 6. 
When the feed screw 1 is rotated by the servomotor 3 in a normal or reverse 
direction, the left and right nut members 5L and 5R screwed thereon are 
thus moved so as to separate from or approach to each other. 
Reference numeral 7 denotes a vertical slide member disposed at right 
angles with the feed screw 1, and reference numeral 8 a guide holder for 
the slide member. When the mechanism is applied to a press machine, a 
working die is provided below the lower end of the slide member 7. 
In the present invention, the vertical sliding motion of the slide member 
7, i.e., the stroke motion thereof, is caused by connecting the nut 
members 5L and 5R to the slide member 7 through connecting members 9L and 
9R, respectively. The stroke operation mechanism which is applied to a 
press machine is arranged as described above. 
Namely, the upper ends of the connecting members 9L an 9R are connected to 
the nut members 5L and 5R by shafts 10L and 10R, respectively. On the 
other hand, the lower ends of both members 9L and 9R are connected to the 
upper end of the slide member 7 by a shaft 10c. When the nut members 5L 
and 5R are moved on the screw 1 so as to separate from and approach to 
each other, the slide member 7 thus makes a vertical stroke motion within 
the guide holder 8. 
The stroke operation mechanism shown in FIG. 1 is designed so that the 
slide member 7 makes stroke motions for press works having various work 
contents. However, the stroke operation mechanism of the present invention 
is not limited to the mechanism shown in FIG. 1. For example, two feed 
screws respectively having a right-hand thread and a left-hand thread are 
arranged parallel, and the nut members 5L and 5R may be screwed on the two 
screws and connected to the stroke member 7 through the connecting members 
9L and 9R, respectively. 
The stroke operation mechanism of the present invention shown in FIG. 1 can 
be applied to a press machine, for example, as shown in FIG. 2. An example 
of press machines provided with the stroke operation mechanisms of the 
present invention is described with reference to FIG. 2. In FIG. 2, the 
same reference numerals as those in FIG. 1 denote the same members. 
In FIG. 2, the stroke operation mechanism of the present invention shown in 
FIG. 1 is mounted on the upper portion of a C-shaped frame 11. In the 
frame 11, a table or bolster 13 for holding a mold 12 such as a lower mold 
or the like is formed on a surface opposite to the slide member 7. 
Reference numeral 14 denotes a slide motion detection bar provided on the 
slide member 7, and reference numeral 15 denotes a position detector 
provided opposite to the detection bar 14. In this arrangement, a 
workpiece (not shown) placed between the slide member 7 and the mold 12 is 
worked on in various manners by the stroke motion of the slide member 7 
caused by normal and reverse rotation of the servomotor 3 and the mold 12. 
The servomotor 3 of the stroke operation mechanism in the press machine 
shown in FIG. 2 is controlled by, for example, the control system shown in 
FIG. 3. In FIG. 3, reference numeral 16 denotes a setting section for 
setting predetermined data such as the stroke speed at a stroke position, 
pressure and the like on the slide member 7; reference numeral 17, a 
present data forming section for collecting data from the position 
detector 15 and forming present data such as the position of the slide 
member 7 during a stroke motion, the speed, the pressure applied and the 
like; reference numeral 18, a reference clock of the data forming section 
17; reference numeral 19, a processing section for comparing the 
predetermined data of the setting section 16 and the present data of the 
present data forming section 17; and reference numeral 20, a motor control 
section for outputting a control signal for the servomotor 3 on the basis 
of the output from the processing section 19. In FIG. 3, although the same 
reference numerals as those in FIGS. 1 and 2 denote the same members, the 
stroke operation mechanism except the servomotor 3 is denoted by reference 
character MC. A pressure sensor 21 is also provided on the slide member 7 
so that the data of the pressure sensor 21 is input to the present data 
forming section 17. 
As described above, during the stroke operation of the slide member 7, the 
stroke speed of the slide member 7 can be controlled only by controlling 
the servomotor 3 at any desired stroke position. The stroke operation 
mechanism of the present invention thus permits various press works such 
as shearing, coining, free bending, cold extrusion, deep drawing, swaging 
and the like to be realized by a single stroke operation mechanism. 
When the press machine shown in FIG. 3 is used as a multipurpose punch 
press, and various set dies such as a trimming die, a notch die and the 
like, all of which are standardized and commercially available, may be set 
between the slide member 7 and the table 13. 
As described above, the present invention provides a stroke operation 
mechanism comprising a combination of a feed screw mechanism and a link 
mechanism, and driven by the driving force obtained from a servomotor 
which can be servo-controlled. The present invention thus has the 
significant effect of enabling all press works having various types of 
stroke operations or press works in a wider range than a conventional 
general purpose press using a single press machine provided with the 
mechanism of the present invention.