JP2001162400A - Screw press - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a screw press capable of securing ram position precision when a rotation quantity of a motor is not directly turned to a ram position resulting from that a mechanical system of a speed reducer, etc., exists between a motor (servo motor) and a screw mechanism. SOLUTION: A position detection sensor to detect a ram position is arranged, a ram position is controlled by the output from the sensor.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a screw press. The screw press refers to a press machine that uses a servo motor as a drive source and raises and lowers a ram (slide) with a screw mechanism.

[0002]

2. Description of the Related Art As a conventional example, there is Japanese Patent No. 2533486. In the patent publication of the related art, the motor is used as a drive source, and the ram is raised and lowered via a screw mechanism. Position control, speed control, etc. of the ram are performed by using pulses of an encoder provided in the motor. Is controlled using

FIG. 5 illustrates this. A screw shaft 7 a is connected to an output shaft of the electric motor (servo motor) 2, and an end of the screw shaft 7 a is screwed into a nut 8 a of the ram 8. When the servo motor 2 rotates in the direction indicated by arrow B, the ram 8 moves up and down in the direction indicated by arrow A by the action of the screw mechanism 7. That is, when the servo motor 2 rotates forward and backward, the ram 8 reciprocates by the action of the screw mechanism. In this case, the ram 8 moves up and down because the screw shaft is provided vertically.

An upper die (not shown) is fixed to the ram 8, and a lower die is fixed to the bolster in opposition to the upper die. The material supplied between the upper and lower dies is pressed.

The servo motor 2 is provided with the encoder 3 as described above. The pulse signal of the encoder 3 is fed back to the position control circuit and the speed control circuit,
Position control and speed control are performed.

The amount of rotation of the servo motor 2 is detected by the encoder 3, so that the amount of up / down movement of the ram 8, that is, the position of the ram 8, can be controlled by the number of pulses of the encoder 3. Furthermore,
The speed of the ram 8 can be controlled by the number of pulses per unit time of the encoder 3.

In the figure, the information processing control circuit performs processing such as inputting, setting, and changing data such as the position and speed of a ram. Here, a preset position of the ram 8,
The position and speed of the ram 8 can be controlled by matching the speed with the pulse of the encoder 3.

The above-mentioned control system is a so-called semi-closed loop system, in which the control of the ram is entirely performed by the pulse of the encoder, and there is no means for feeding back the actual ram movement state. Therefore, in the conventional example, in order to control the ram position with high accuracy, the electric motor serving as the driving source and the screw mechanism are directly connected, and the positional accuracy of the ram is changed between the two due to deformation and play. There is no intervening device that inhibits.

In other words, in the semi-closed loop system as in the conventional example, since there is no configuration for feeding back the actual position information of the ram, if a mechanical system is interposed between the electric motor and the screw mechanism, the electric motor is not driven. Does not directly correspond to the position of the ram, and the desired positional accuracy of the ram cannot be obtained.

[0010]

SUMMARY OF THE INVENTION An object of the present invention is to reduce the amount of rotation of the electric motor immediately by the presence of a mechanical system such as a speed reducer between the electric motor (servo motor) and the screw mechanism. The object of the present invention is to provide a screw press that can secure the positioning accuracy of the ram when it does not reach the position.

[0011]

According to the present invention, a position detecting sensor for detecting the position of the ram is provided, and the position of the ram is controlled by an output from the sensor. More specifically, the invention according to claim 1 is a screw press that drives a ram with a servomotor via a screw mechanism, wherein a position detection sensor for detecting the position of the ram is interposed between the frame or the bolster and the ram. The output of the position detection sensor is used for position control of the ram, and the position of the position sensor in the height direction is set near the lower surface of the ram. According to a second aspect of the present invention, in addition to the configuration of the first aspect of the present invention, an allowable value for the ram to be considered to have reached the bottom dead center is provided for a preset value of the bottom dead center. , The permissible value was adjustable. According to the third aspect of the present invention, in addition to the configuration of the first or second aspect of the present invention, the magnitude of the deviation can be adjusted for each of the plurality of points by a timer in the vicinity of a plurality of points for specifying a preset ram position. And Claim 4
The invention according to claim 1, in addition to the configuration of the invention according to claim 1, in each of the plurality of preset points excluding the bottom dead center, the ram is used for the data of the preset position. Is provided, and the allowable value is made freely adjustable.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1, a servomotor 2 is fixed to a frame 1, a pulley 4 is fixed to an output shaft of the servomotor 2, and an encoder 3 is provided at an end of the servomotor 2. On the other hand, a screw mechanism is provided on the frame 1, and a pulley 6 is fixed to the upper end of the screw shaft. A belt is hung on the pulley 4 and the pulley 6. The diameter of the pulley 4 is smaller than the diameter of the pulley 6,
The pulley 6 and the belt 5 form a reduction gear.

The lower end of the screw shaft is screwed into a nut of the ram 8. The ram 8 is guided by a guide mechanism 10 and is movable up and down. The guide mechanism 10 includes a cylindrical guide fixed to the bed 1a and a solid rod fixed to the ram 8 and fitted to the cylindrical guide, and guides the ram 8 in the vertical direction. A bolster 9 is fixed to the bed 1a.

In FIG. 1, the frame 1 or the bolster 9
And a ram 8 with a linear scale 11 interposed therebetween. The linear scale 11 measures the vertical position of the ram 8, and the output of the linear scale 11 is used to control the position of the ram 8, that is, the vertical position of the ram 8. The linear scale 11 is the frame 1
It is located in a place that is not easily affected by the deformation of That is,
The position in the height direction is near the lower surface of the ram 8, the distance from the upper surface of the bed 1a is made as small as possible, and the amount of deformation of the frame 1 during that is reduced. As the distance from the upper surface of the bed 1a to the linear scale 11 increases, the amount of deformation of the frame 1 therebetween increases, and the output error of the linear scale 11 increases, which is inconvenient.

Although not shown in FIG. 1, an upper die is fixed to the lower surface of the ram 8 and a lower die is fixed to the upper surface of the bolster 9. These upper and lower molds are provided with in-mold position sensors, which are high-precision sensors that can accurately measure the distance between the upper and lower molds near the bottom dead center. The raw material supplied between the upper die and the lower die is subjected to press working as the ram 8 moves up and down, and becomes a product.

When the servo motor 2 rotates, the rotation of the servo motor 2 is transmitted to the screw shaft of the screw mechanism 7 via the pulley 4, the belt 5, and the pulley 6. In this case, the rotational torque of the servo motor 2 is increased and transmitted to the screw shaft.

When the screw shaft rotates, the ram 8 descends at a set speed by the action of the screw mechanism 7, and the material supplied between the upper die and the lower die is pressed. When the ram 8 reaches the bottom dead center and press working is completed, the servo motor 2 rotates in the reverse direction, the ram 8 rises at the set speed, and stops at the top dead center.

In FIG. 2, when the servo motor 2 rotates, the screw shaft 7a rotates in the direction of arrow B as described above, and the ram 8 moves up and down in the direction of arrow A. Linear scale 1
1 is fed back to the position control circuit, and the pulse signal of the encoder 3 is fed back to the speed control circuit. That is, the position of the ram 8 is controlled by the output of the linear scale 11, and the speed of the ram 8 is controlled by the pulse signal of the encoder 3.

In FIG. 2, the information processing control circuit performs processing such as inputting, setting, and changing data such as the position and speed of the ram. The information processing control circuit includes an in-position setting circuit and a timer setting circuit described later.

FIG. 3 shows a molding pattern, that is, a movement pattern of the ram 8 required for various press workings.
3, (b) three positions, (c) four positions, and (d) five positions. In this figure, the vertical axis indicates the vertical distance, and the horizontal axis is the time axis.
In the case of the first (a) two positions, the ram 8 only descends and ascends, and only reciprocates between the top dead center and the bottom dead center at a constant speed. The vertical distance from the top dead center to the bottom dead center is the stroke length of the ram 8, and the slope of the line segment indicates the speed of the ram 8. These line segments show the trajectory of the movement of the ram 8.

In the case of the second (b) 3 position, the ram 8 is decelerating while descending. In drawing and punching, it is advantageous in terms of formability, noise, vibration, etc., to perform press working at a reduced speed.

One of the patterns shown in FIG. 3 is selected according to the press working. After that, the position and speed of each position are input and set.

Referring to FIG. 4, the procedure for setting the position and speed of the ram 8 when five positions are selected will be described. First you must determine the bottom dead center. In this example, the fourth position is the bottom dead center. Next, the stroke length,
That is, the vertical distance between the first position and the fourth position is set. Hereinafter, the position of each position, that is, the height above the bottom dead center is set. Subsequently, the speed between each position is set. Thus, the exercise pattern of the ram 8 is set. The above setting is performed by keying in a numerical value at a place determined for each item on the control panel.

The position of the ram 8 is controlled by matching the set position data with the output of the linear scale 11, and the speed of the ram 8 is controlled by matching the set speed data with the output of the encoder 3. Is done.

Hereinafter, a series of operations of the ram will be described. FIG.
In the state where the press machine is not operating, the servomotor 2 is stopped, and the ram 8 is also in the first dead center, which is the top dead center.
Stopped in position. When the operation of the press machine is started and the servo motor 2 rotates forward, the ram 8 moves down from the first position to the second position at the set speed.
When the ram 8 reaches the second position, it descends at a set speed toward the third position.

Similarly, when the ram 8 reaches the fourth position, which is the bottom dead center, the servo motor 2 rotates in the reverse direction and the ram 8 rotates.
Rises toward the fifth position at the set speed. The ram 8 that has reached the fifth position returns to the top dead center in the same manner, the servomotor 2 stops, and the ram 8 also stops. Hereinafter, the above series of operations is repeated. When the press machine is operated continuously, the servo motor 2 switches to forward rotation at the top dead center, the ram 8 descends after reaching the top dead center, and repeats the same operation as described above.

In the above operation, if the position of the ram 8 is made to approach the set value as much as possible at the fourth position, an enormous amount of time is required for control, and the productivity is reduced.
Therefore, the difference between the set value and the current position of the ram 8 is a constant value (hereinafter referred to as an in-position value; see the in-position setting circuit in FIG. 2) according to the allowable accuracy of the product to be handled.
If it is within the range, it is considered that the ram 8 has reached the set position, and the operation of the ram 8 is shifted to the next step. As an example of the in-position value, each is set to 5 micrometers on the plus side and the minus side with respect to the set value. This in-position value ranges from 1 micrometer to 1000
It is designed to be set in the micrometer range. The in-position value is selected according to the allowable accuracy of the product to be handled as described above. It is also possible to correct the in-position value by measuring the dimensions of the actually pressed product.

During the above series of operations, for example, the actual trajectory of the ram 8 in the second position has a so-called deviation in control, so that the trajectory of the ram 8 does not necessarily pass directly above the second position. , On the curve near the second position. That is, the vicinity of the intersection of the straight line connecting the first position and the second position and the straight line connecting the second position and the third position is a curve having a certain radius.

In the press working, the second position is important, and it is sometimes desired that the radius is as small as possible. Conversely, the second position is not so important, and the radius may be large. is there. Therefore, it is desired that the radius can be set and changed as needed without making the radius uniform.

In the present invention, FIG.
The position passing accuracy is determined by setting and changing the deviation using a timer setting circuit shown in FIG. That is, a stop time is set by a timer for each of the positions, and the trajectory of the ram 8 is controlled so as to achieve a desired position passing accuracy. This set value may be corrected based on the state of the press working, the accuracy of the pressed product, and the like.

As a means for improving the position passing accuracy of each position, the above-described in-position method may be used instead of using the timer as described above. That is, an in-position value is set for each position, and the
When the position becomes within this in-position value, move to the next step.

Next, there is a measurement result of the inventor regarding the position accuracy of the ram, which will be introduced. When using a linear scale with a 400 kN load applied to a machine with a pressurizing capacity of 600 kN, the error at bottom dead center is several micrometers to several tens of micrometers. A few hundred micrometers.

The error is a difference between a preset value and a measured value of the actual bottom dead center position. From this experiment, it is understood that according to the present invention, a ram position accuracy of about 10 times or more as compared with the conventional art can be obtained. That is, it is possible to obtain a pressed product with higher precision.

[0034]

The present invention employs a control system (full closed loop system) in which the position of the ram is directly measured and its output is fed back to the position control device, so that the ram position is controlled with extremely high accuracy. be able to. That is, the ram position is controlled with high precision without being affected by the extension of the frame due to the load, the deformation of each member due to a thermal change, the deformation of the member transmitting the power of the servomotor due to the load, and the play between the members. be able to.

[Brief description of the drawings]

FIG. 1 is a front view of a partial cross section.

FIG. 2 is a block diagram.

FIG. 3 is an explanatory view of a forming pattern.

FIG. 4 is an explanatory diagram of position setting.

FIG. 5 is a block diagram of a conventional example.

[Explanation of symbols]

1 is a frame, 1a is a bed, 2 is a servo motor, 3 is an encoder, 4 is a pulley, 5 is a belt, 6 is a pulley, 7
Is a screw mechanism, 7a is a screw shaft, 8 is a ram, 8a is a nut portion, 9 is a bolster, 10 is a guide mechanism, and 11 is a linear scale.

Claims (4)

[Claims] In a screw press for driving a ram by a servomotor via a screw mechanism, a position detection sensor for detecting a position of the ram is provided between a frame or a bolster and the ram, and the position detection sensor is provided. A screw press, wherein an output of the sensor is used for position control of a ram, and a position in a height direction of the position sensor is set near a lower surface of the ram. 2. A method according to claim 1, wherein a predetermined value of the bottom dead center is provided with an allowable value for the ram to be considered to have reached the bottom dead center, and the allowable value is adjustable. The screw press according to claim 1, wherein 3. The method according to claim 1, wherein the magnitude of the control deviation can be adjusted for each of the plurality of points by a timer in the vicinity of a plurality of points for specifying a preset ram position. Screw press as described. 4. In each of a plurality of preset points except a bottom dead center, data of a preset position is
The screw press according to claim 1, wherein an allowable value is considered to be considered as the ram has reached each of the points, and the allowable value is adjustable.