JP4150243B2 - Electric press - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electric press.
[0002]
[Prior art]
Electric presses that use an electric motor as a motive power, convert the rotation of the motor into vertical motion with a ball screw, etc., and apply pressure to the workpiece by moving the ram up and down. Widely used.
This electric press can control a pressing force, a stop position, a drive speed, a stop time, and the like by controlling a motor, and realizes precise pressurization as described above.
In the electric press, a load cell for detecting the load of the ram is provided, the load of the ram is detected, and the load signal is used for various controls.
[0003]
[Problems to be solved by the invention]
However, the load cell has a problem that an output when no load is applied, that is, a so-called zero balance, fluctuates due to secular change or the like, and there is a problem that precise control cannot be performed due to this zero balance change.
Also, if the zero balance fluctuation becomes too large, the load cell output will saturate with respect to the operating range of the ram, making it impossible to detect the load value in the full range, or deviating from the linearity range of the load cell output, resulting in an accurate output value. However, there is a problem that the state of such a load cell cannot be known by a conventional electric press.
The object of the present invention is to solve the problems of the prior art.
[0004]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides an electric press comprising a motor, a conversion device that converts the rotational motion of the motor into linear motion, and a ram that performs linear motion by the conversion device. Based on a load detection device for detecting a load, storage means for storing the output of the load detection device when the load of the ram is zero as a calibration amount, and the stored calibration amount of the load detection device, As a result of comparison by calibration means for calibrating the output from the load detection device, means for comparing whether or not the calibration amount is a predetermined value or more, and the comparison means, the calibration amount is a predetermined value or more. when, characterized by comprising means for making a notification to that effect, the.
With the above configuration, since the zero balance of the load detection device can be calibrated based on the calibration amount, an accurate load can be detected and precise control can be performed.
It may become large enough not perform load detection or calibrate the amount of full range, or when the load detection output is or are unable to maintain linearity, it is possible to perform a notification to that effect.
[0005]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
1 is a functional block diagram, FIG. 2 is an external view, and FIG. 3 is a side sectional view.
This electric press uses a motor 21 as a drive source, and is configured to transmit the rotation by the motor 21 to a ball screw 23 as shown in FIG. 3 and to move the ram 22 engaged with the ball screw 23 up and down. Yes.
A pressing body 24 is attached to the tip of the ram 22 so as to press the work W placed on the stage 29.
A load cell 5 is attached to the pressing body 24 to detect a load applied to the ram 22.
[0006]
As shown in FIG. 1, the load cell 5 includes an amplifier 50 and an A / D converter 51, and is configured to transmit the detected load signal to the CPU 1.
A calibration amount storage device 3 is connected to the CPU 1 and is configured to store the output of the load cell 5 when the load of the load cell 5 is zero as a calibration amount.
The calibration device 2 is configured to calibrate the load detection signal from the load cell 5 based on the calibration amount stored in the calibration amount storage device 3.
[0007]
The CPU 1 is further configured to compare the calibration amount with a predetermined value, and to notify the notification device 4 when the calibration amount is equal to or larger than the predetermined value. By this notification, the user can exchange the load cell 5 and the like.
[0008]
The approach sensor 11 is configured to detect a predetermined position of the ram 22 in the vertical direction and send the position signal to the CPU 1. The CPU 1 performs various controls based on the position signal.
The control program storage device 10 stores a program for controlling the entire apparatus, and is configured to perform control according to this program.
[0009]
The calibration amount and its calibration will be described with reference to FIG.
The horizontal axis of FIG. 4 shows the position of the pressurizing operation of the ram 22, and it operates from the zero point where there is no load to the maximum load position Mmax. The vertical axis represents the output of the load cell 5, and outputs from zero to Smax.
Here, as shown in the figure, only the portion where the output of the load cell 5 is linear is used, and accurate load detection is possible if only calibration of the zero point is performed.
[0010]
The output of the load cell 5 when the load is 0 is stored in the calibration amount storage device 3 as a calibration amount. In the case of the characteristic R, the calibration amount is zero, but R ′ is the calibration amount O1, and R ″ is O2. The detection value of the load cell 5 is sequentially calibrated with this calibration amount and used for control. It is configured.
[0011]
In this embodiment, when the upper limit value and the lower limit value shown in the figure are set and the output of the load cell 5 may exceed the upper limit value or the lower limit value while the ram 22 is displaced from 0 to Mmax, the notification device 4 Is configured to make a notification to that effect.
For example, in the characteristic R ′, the output of the load cell 5 is within the upper limit value. However, in the characteristic R ′ ″, the output of the load cell 5 exceeds the upper limit value when the displacement M1 of the ram 22 is greater than the upper limit value. It has become so.
The calibration amount when the output of the load cell 5 exceeds the upper limit value or the lower limit value is set as the predetermined values C1 and C2, and the predetermined value C1 and C2 is compared with the calibration amount to notify the notification device 4 , Is supposed to determine non-notification.
[0012]
As the upper limit value and the lower limit value, the output limit value of the load cell 5 or the range in which the output of the load cell 5 maintains linearity can be used.
In the case of the output limit value, as described above, when the calibration amount exceeds the predetermined value C1 in FIG. 4, the output of the load cell 5 is saturated with respect to the displacement of the ram 22 equal to or greater than M1.
When the linearity is maintained, the output of the load cell 5 does not become linear with respect to the displacement of M1 or more.
[0013]
The operation will be described with reference to FIG.
When the power supply device 20 is turned on (step S1), initialization is performed first (step S2), and the output of the load cell 5 when the load of the ram 22 is zero is read and the calibration amount storage device 3 performs calibration. It is recorded as a quantity (step S3). This calibration amount is compared with the predetermined values C1 and C2 in the CPU 1, and if it is larger than the predetermined value, a notification to that effect is made (step S5). This notice can be displayed, sounded, etc. Further, a notification that prompts replacement of the load cell 5 may be used.
When a work start operation is performed (step S6), the work is started (step S7). At this time, the detected value from the load cell 5 is calibrated based on the calibration amount stored in the calibration amount storage device 3. The apparatus 2 is used after being calibrated (step S8), and the operation is continued until the work is completed (step S9).
[0014]
In the embodiment described above, since the control can be performed by properly calibrating the calibration amount of the load cell 5, a precise press is possible. Further, when the amount of calibration of the load cell 5 exceeds a predetermined amount, a notification to that effect is made, so that it is possible to know the time for replacement of the load cell 5 and the like.
[0015]
【The invention's effect】
As described above, according to the electric press of the present invention, the linear characteristic portion of the load cell can be limited and utilized, so that precise press control can be performed only by performing calibration at 0 point. Ri, and when become large enough calibration weight is unable to load detection in full range, or the load detection output is or are unable to maintain linearity, it can be ing effect it is possible to notice to that effect .
[Brief description of the drawings]
FIG. 1 is a block diagram showing an embodiment of the present invention.
FIG. 2 is a perspective view showing an embodiment of the present invention.
FIG. 3 is a side sectional view showing an embodiment of the present invention.
FIG. 4 is an operation explanatory diagram of one embodiment of the present invention.
FIG. 5 is a flowchart showing the operation of one embodiment of the present invention.
[Explanation of symbols]
1: CPU, 2: calibration device, 3: calibration amount storage device, 4: notification device, 5: load cell, 10: control program storage device, 11: ingress sensor, 20: power supply device, 21: motor, 22: Ram, 23: Ball screw, 24: Pressing body, 29: Stage, 50: Amplifier, 51: A / D converter.

Claims (3)

In an electric press comprising a motor, a conversion device that converts the rotational motion of the motor into linear motion, and a ram that performs linear motion by the conversion device,
A load detection device for detecting the load of the ram;
Storage means for storing the output of the load detection device when the load of the ram is zero as a calibration amount;
Calibration means for calibrating the output from the load detection device based on the stored calibration amount of the load detection device;
Means for comparing whether the calibration amount is a predetermined value or more;
If the result of comparison by the means for comparing is that the calibration amount is greater than or equal to a predetermined value, means for notifying that effect;
An electric press comprising: The predetermined value is a calibration amount in which the output of the load detection device exceeds the output limit in the loadable range of the ram.
The electric press according to claim 1 . The predetermined value is a calibration amount in which the output of the load detection device loses linearity in the loadable range of the ram.
The electric press according to claim 1 .

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