JPS6331319B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a load detector that detects a load through the amount of elongation of a frame of a press machine.

Various types of load cells have been proposed in the past as this type of load cell. For example, load cells that use mechanical elongation detectors, such as dial gauge type and tilt type, are relatively inexpensive;
The amount of elongation is easily affected by temperature, and malfunctions are likely to occur due to vibrations during press operation. For this reason, this type of mechanical type has the drawback of not being able to follow rapid load fluctuations such as during punching, and having poor detection accuracy. In addition to the mechanical types mentioned above, elongation (load) detectors include capacitive types, strain gauge types, optical types, differential transformer types, and rotary encoder types. Although the detection accuracy is high, it is expensive and at the same time has the disadvantage of being restricted in the environment in which it can be installed.

The present invention has been made in view of the above, and includes:
The purpose of the present invention is to provide a load detector that has a simple structure, is inexpensive, and can perform highly accurate measurements.

The present invention will be described below with reference to an illustrated embodiment.

In the figure, 1 is a frame of a C-type frame press, and a load detector 4 is installed between the lower end of a detection rod 2 whose upper end is fastened and fixed to the side surface of the frame 1 and a fixed arm 3 fixed to the side surface of the frame 1. It is installed.

The load detector 4 has a Hall element fixing case 6 fixed to the detector body case 5 fixed to the upper end of the fixed arm 3 with screws 7, and a hole element fixed case 6 formed at the center of the upper surface of the fixed case 6. A Hall IC 9 as a Hall element is installed in the recess 8.
10 is an output terminal of a Hall IC provided in the fixed case 6.

A cover 12 that holds the plunger 11 so as to be freely retractable is attached to the upper surface of the detector main body case 5 by screws 13.
It is tightened and fixed. Further, the upper end of the actuating plunger 14 passed through the upper wall of the main body case 5 is brought into contact with the inner end surface (lower end surface) of the plunger 11, and the permanent magnet 15 fixed to the lower end of the actuating plunger 14 is placed in the recess 8. Hall IC facing inside
It is placed close to and opposite to 9. By tensioning a return spring 17 between the spring receiver 16 fixed near the upper end of the operating plunger 14 and the upper wall surface of the main body case 5, both the plungers 11 and 14 are biased to protrude. The upper end surface of the plunger 11 is held in contact with the lower end surface of the detection rod 2, and a permanent magnet 15 is disposed to follow the plunger 14.

In the above configuration, when a load is applied to the slide supported by the frame 1, the frame 1 expands and contracts due to the reaction force of this load. Then, the upper end fixing portion of the detection rod 2 and the fixed arm 3 come into contact with each other and separate from each other, so that the plunger 11, which is held in contact with the lower end surface of the detection rod 2, is moved in and out while being held by the return spring 17. Then, as the operating plunger 14 moves up and down, the permanent magnet 15 fixed to the lower end of the plunger moves into the hole.
Connect to and separate from IC9.

Here, one output terminal connected to the Hall IC 9 outputs a voltage whose magnetic flux density changes depending on the relative distance between the permanent magnet 15 and the Hall IC 9, as shown by characteristic line A in Figure 3. At the same time, the other output terminal outputs a voltage that changes as shown by characteristic line B in the figure. Also, since the rate of change of both voltages is constant, the difference between the voltages output from both output terminals is determined by the relative distance between the permanent magnet 15 and the Hall IC 9, as shown by characteristic line C in FIG.
In other words, as the amount of elongation of the frame that is proportional to the load on the slide increases, it linearly decreases gradually. Therefore, if the output voltage according to this characteristic line C is converted into a load, the load on the slide can be detected.

Here, the output voltage of the detector 4 is converted into a load value by a control device as shown in FIG. 4, for example.

That is, each output terminal 10 of the detector 4 is connected to the input terminal of the differential amplifier 18 to amplify the difference voltage between the terminals, and the temperature correction circuit 19 performs temperature correction on this amplified voltage. The voltage corrected in this way is sampled and held by the sample hold circuit 20 and the peak hold circuit 2.
1, respectively.

Further, a measurement range is set by a rotary cam limit switch 22 linked to the main shaft of the press machine, etc., and one pulse is applied to the gates 23 and 24 of each of the hold circuits 20 and 21 at the beginning of this measurement range. Then, the sample and hold circuit 20 samples the input voltage when the pulse is input and holds it after the pulse is input, and the peak hold circuit 21 holds the peak value of the input voltage after the pulse is input.

Then, the outputs of the sample hold circuit 20 and the peak hold circuit 21 are subtracted by a differential amplifier 25, and converted into tonnage by a load converter 26.
The signal thus converted is converted into a digital quantity by the A/D converter 27 and digitally displayed on the display 28.

On the other hand, the output of the load converter 26 is sent to the comparator 30 along with the output of the overload setting device 29.
is input. When the output of the load converter 26 becomes larger than the output of the setting device 29, that is, when the amount of elongation of the frame 1 in response to the load of the press machine reaches a permissible value or more, the indicator lamp 31 is activated. , the external output contact 32 is operated to output a stop signal to the press machine.

Furthermore, when the measurement range is outside the measurement range set by the rotary cam switch 20, a signal is applied from the gate 33 to the latch circuit of the A/D converter 27 to hold it, so the display 28 continues to display unless the power is turned off. . Also, within the measurement range, the hold is released and a new peak value is sampled.

Then, in the next measurement, the sample hold circuit 20 and the peak hold circuit 21 are connected to each circuit 2.
Since the same input voltage at the start of measurement is sampled by one pulse from the rotary cam switch 22 inputted to the gates 0 and 21, the output of the differential amplifier 25 automatically becomes zero. For this reason, the displacement amount for each cycle is peak-held and displayed every time. 34 is detector 4
NAND circuit installed to check for disconnection,
35 is an inverter for inputting a check voltage to this NAND circuit 34.

That is, since the output of the detector 4 is an analog voltage responsive to the load, temperature correction and other processing circuits are simplified. For this reason, the control device 17 is simplified and the detection device can be provided at low cost.

Furthermore, since the detector 4 is of a non-contact type and has extremely high responsiveness, it can sufficiently respond to rapid changes in load accompanied by vibrations and the like. For this reason, measurement accuracy and reliability can be sufficiently increased.

Incidentally, when the press machine is a straight side press as shown in FIG. 5, the amount of elongation of the frame 1 is relatively small. Therefore, in such a case,
By lengthening the detection rod 2 and the fixed arm 3 and increasing the fixed interval between them, the amount of elongation of the frame 1, that is, the detection accuracy of the load of the press machine can be increased.

As explained above, according to the present invention, the distance between the tip of the detection rod whose base end is fixed to the frame and the fixed arm, that is, the amount of extension of the frame, is detected as the output voltage of the Hall element. Therefore, it is possible to improve load detection accuracy and reliability while having a cheaper and simpler configuration than conventional ones. In addition, since the output of the Hall element is an analog voltage, a control device that corrects or converts this output voltage can be configured with a simple circuit, and in the near future, a load detection device with high detection accuracy and reliability can be provided at low cost. can.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a C-frame press equipped with the present invention. FIG. 2 is a cross-sectional view of the detector. FIG. 3 is a diagram showing the output characteristics of the detector. FIG. 4 is a circuit diagram showing an example of a control device connected to the detector. FIG. 5 is a perspective view of a straight-sided press equipped with the present invention. 1... Frame, 2... Detection rod, 3... Fixed arm, 4... Load detector, 5... Detector body case, 9
... Hall IC, 10 ... Output terminal, 11 ... Plunger, 14 ... Operating plunger, 15 ... Permanent magnet, 1
7...Return spring.

Claims (1)

[Claims] 1. A plunger is attached to the detector main body case so as to be freely retractable, a permanent magnet is fixed to the tip of the operating plunger that follows the plunger, and a Hall element that closely faces the magnet is attached to the detector main body case, and the A return spring is provided that biases the plunger to protrude and bias the permanent magnet away from the Hall element, and the tip surface is brought into contact with the base end of the fixed arm to which the detector body case is fixed at the tip and the outer end surface of the plunger. A load detector for a press machine, characterized in that a proximal end of a held detection rod is fixed to a frame of the press machine.