JPH0686039B2 - Overload prevention device in press machine - Google Patents

Description

TECHNICAL FIELD The present invention relates to an overload prevention device in a press working machine, and for example, it is suitable for use in a press working machine that performs continuous working using numerical control or the like. Load prevention device.

"Prior art" In a press machine, preventing overload is an important point from the viewpoint of work safety, protection of molds and press machines, prevention of defective products, etc. Various methods have been implemented conventionally.

For example, there is a so-called shear plate method. This is called a sharp plate that is configured so that a pair of punch and die are formed between the pressurizing mechanism part and the die mounting part, and the maximum allowable pressure of the press machine can be punched at the same pressure between them. It consists of a steel insert,
When the overload exceeds the allowable maximum pressure, the steel material is punched out by the punch and the die, so that the punch penetrates into the die hole and the distance between the pressure mechanism section and the die mounting section. Was applied to reduce the pressure applied from the processing mechanism to the die mounting portion to prevent overload.

Also, instead of the punch, die, and sharp plate,
A pair of hydraulic cylinder and piston are provided between the pressurizing mechanism section and the die mounting section, and a relief valve for escaping the pressure oil in the hydraulic cylinder when the maximum allowable pressure is applied is provided.
It was intended to have a similar effect.

[Problems to be Solved by the Invention] However, since the set pressurizing force of the overload protection device in the above two examples is generally close to the maximum allowable pressurizing force of the press machine body, a metal having a smaller yield strength than that. When using a mold, there is a problem that it is not effective for protecting the mold.

Further, in the system using the hydraulic cylinder and the piston, even if the relief valve mechanism is variable, adjustment is required each time the mold is replaced, and the reproducibility of the set pressurizing force changes the oil temperature and the spring mechanism of the relief valve. It becomes a problem due to instability, and even if it can be used for mass production with few die setup changes, it can be used for work in which the pressing force changes for each process like a press machine using numerical control. Was not usable at all.

That is, as shown in FIG. 6, when continuously bending the processed material 1 having the long piece a and the short piece b, the distance between the molds was changed by numerical control so that the long piece a and the short piece b were matched. Since the pressure is applied, the operating pressure at that time is different, so if only the maximum allowable pressure can be set as described above, it is easy to break the mold, the safety, the likelihood of defective products, etc. There was a problem that it could not be adopted from the point.

The present invention has been proposed in view of the above circumstances, and an object thereof is to provide an overload prevention device in a press machine that can be applied to continuous processing by setting a pressure value that matches the working pressure. To provide.

“Means for Solving the Problem” The overload prevention device according to the present invention is characterized in that when the press working including the first to n-th steps (n is an arbitrary integer of 2 or more) is performed by the same press working machine, An overload prevention device for stopping the press operation when the pressing force in each process becomes excessive, and a pressure detecting means for detecting the operating pressing force of the press working machine, and the first to nth storage areas. A storage unit that stores the maximum value of the pressing force detected by the pressure detection unit during the first to nth steps of the first press working in these n storage areas; When the progress is detected and the press machine performs the i-th step (i = 1, 2, ..., N), the step-progress switching means for selecting the i-th storage area and the step-progress switching means are selected. Of the pressing force stored in the i-th storage area An allowable pressure value setting means for setting an allowable pressure value in the i-th step by multiplying a large value by a predetermined margin rate; an allowable pressure value in the i-th step set by the allowable pressure value setting means; Comparing the operating pressure detected by the detecting means, comparing means for outputting a stop signal when the pressure value of the latter becomes equal to or higher than the pressure value of the former, and the press operation based on the stop signal of the comparing means. It is characterized by comprising stop means for stopping.

[Operation] In the overload prevention device according to the present invention, the pressing force of the press working machine is detected by the pressure detecting means at the first to n-th steps of the first press working, and each maximum value of the pressing force for each step is detected. Are sequentially stored in the first to nth storage areas of the storage means. When performing the press work after the next time, the process progress switching means detects the process progress by the press working machine, and when the press working machine performs the i-th process (i = 1, 2, ..., N), the i-th process is performed. While the storage area is selected, the allowable pressure value setting means calculates the allowable pressure value in the i-th step by multiplying the pressing force maximum value stored in the selected i-th storage area by a predetermined margin rate. Further, the comparing means compares the allowable pressure value in the i-th step with the operating pressure force detected by the pressure detecting means during the actual i-th step, and the latter pressure value becomes equal to or higher than the former pressure value. Sometimes a stop signal is output, and the stop means immediately stops the press operation based on the stop signal. Therefore, even if the press working consists of multiple steps and the allowable pressure value differs for each step, it is possible to judge whether the applied pressure is excessive or not based on the allowable pressure value that matches each step. Prevent the mold from breaking,
It is possible to reduce the occurrence of defective products.

"Embodiment" An embodiment of an overload prevention device according to the present invention is shown in Figs.
It will be described with reference to the drawings.

First, the schematic configuration of the overload prevention device of this embodiment will be briefly described with reference to the block diagram of FIG. 1. This overload prevention device detects pressure applied to the press machine 1 as an electric signal. Pressure detection means 2 such as a container, storage means 3 for storing the maximum value of the operating pressure force of each step of the press machine 1 detected by the pressure detection means 2 at the time of the first press working, and each storage means 3 Allowable pressure value setting means 4 for setting the allowable pressure value for each process against overload by multiplying the maximum value of the operating pressurizing force stored by
And the allowable pressure value of the allowable pressure value setting means 4 and the operating pressure detected by the pressure detecting means are compared for each process, and when the latter pressure value becomes equal to or higher than the former pressure value. It comprises a comparison means 5 for outputting a stop signal, and a stop means 6 for stopping the press operation by turning off the power supply based on the stop signal S of the comparison means 5. More specifically, the storage means 3 has first to nth storage areas, and these n storage areas are detected by the pressure detection means 2 during the first to nth steps of the first press working. The maximum value of the pressing force is stored respectively. Also,
Although not shown in the drawing, when the press machine detects the process progress and performs the i-th process (i = 1, 2, ..., N), the process progress switching is performed to select the i-th storage area. Means is provided, and the allowable pressure value setting means 4 multiplies the maximum value of the pressing force stored in the i-th storage area selected by the process progress switching means by a predetermined margin rate to perform the i-th step. The allowable pressure value at is set. Further, the comparison means 5 compares the allowable pressure value of the i-th step set by the allowable pressure value setting means 4 with the operating pressure applied by the pressure detection means 2, and the latter pressure value is the former pressure value. The stop signal is output when the pressure value is exceeded.

That is, the overload prevention device having such a configuration detects the operating pressure of the press machine 1 for each step by the pressure detection means 2 at the time of the first processing, and also determines the maximum value of the operating pressure for each step. Is stored in the storage means 3, and at the time of the second and subsequent machining, the maximum value of the operating pressure force for each step stored in the storage means 3 for the first time is multiplied by a certain margin rate to allow each step. The pressure value is set by the permissible pressure value setting means 4, and the permissible pressure value is compared with the operating pressure applied by the pressure detecting means 2 for each step by the comparing means 5 to operate at the permissible pressure value or more. Pressing machine is press machine 1
When it occurs at 1, the stop signal S can be supplied to the comparison means 5 or the stop means 6 so that the stop means 6 turns off the power of the press machine 1 to immediately stop the press operation.

Next, a specific example of the case where the above overload preventing device is used for a press brake will be described in detail with reference to FIGS. 2 to 5. First, in FIG. 2, the press brake main body 11
Is composed of an upper frame 12, a lower frame 13, two to four tie rods 15 penetrating the base 14, and an equal number of spacer tubes 16 placed on the outer periphery of the tie rods 15.

Both ends of the tie rod 15 are firmly tightened with nuts 17 so as to withstand the stress of press working, and the outer circumference of the spacer tube 16 also serves as a slide guide surface of the lower frame 13.

Further, a lower surface of the upper frame 12 is usually provided with a convex V-shaped upper die 18 via a mounting jig (not shown), and an upper surface of the lower frame 13 is also provided with a concave V-shaped lower die 19 via a mounting jig. Is attached, the processing material 20 is placed between the upper mold 18 and the lower mold 19, and the lower frame 13 is raised to perform processing.
Then, the processing position of the processing material 20 is determined by II in FIG.
As shown in FIG. 3 which shows a cross section taken along the line I-III, a ball screw 22 and a ball nut directly connected to the back gauge positioning motor 21.
The back gauge 24 is moved via 23. This back gauge 24 is a linear guide (not shown)
Guided by, it is designed to move linearly. A series of mechanisms from the back gauge positioning motor 21 to the ball screw 22, ball nut 23, and linear guide are
Only one set is shown in the figure, but normally one for each side
Back gauge positioning motor 21
Is rotated by the back gauge positioning motor drive circuit 26 in synchronization with right and left.

Further, the drive system for driving the lower frame 13 up and down,
As shown in the lower part of FIG. 2, the hydraulic pump 32 directly connected to the hydraulic drive motor 31 sucks up the hydraulic oil 34 stored in the hydraulic oil tank 33, and the hydraulic cylinder on the base 14 through the solenoid valve 41. When the hydraulic oil 34 is led to 51 and hydraulic oil 34 is supplied to the hydraulic cylinder 51, the hydraulic piston 52 and the lower frame 13 are pushed up for processing. Further, in this drive system, since the ball 38 inside the operation valve 37 is lowered until the foot pedal 36 suspended by the tension spring 35 is depressed, the hydraulic oil 34 pressurized by the hydraulic pump 32 is hydraulically operated. Route A → B → C without going to cylinder 51
The lower frame 13 is constructed so as to return to the hydraulic oil tank 33 via the above. Then, by gradually stepping on the foot pedal 36, the ball 38 is pushed up via the rod 39 and the path between B and C is gradually narrowed, but since the rotational speed of the hydraulic pump 32 is constant, it is discharged. Since the amount of oil remaining is constant, the hydraulic cylinder 51
The hydraulic piston 52 starts to rise gradually, and when the pedal 36 is depressed, the ball 38 completely closes the hydraulic path B → C,
The maximum pressure and flow rate reach the hydraulic cylinder 51 via the solenoid valve 41 so that machining is performed.

The solenoid coil 42 of the solenoid valve 41 is always energized during normal operation, so that the state shown in FIG. 2 is reached, and the pressurized oil reaches the hydraulic cylinder 51.

Also, due to the pressurized oil, the hydraulic piston 52 is
It rises inside, but when it rises to a certain position, it is attached to the hydraulic piston 52 and rises integrally with the hydraulic piston 52 It is built in the sleeve 53 and pushed up by the spring 54 and closely adheres to the valve seat surface 55 of the sleeve 53. Ball 56
But needle 57 that also penetrates the center of sleeve 53
It is pushed down by the valve seat surface 55 to widen the space, and the pressurized oil passes between the ball 56 and the valve seat surface 55, passes through the passage 58 provided on the side surface of the sleeve 53, and passes through the path D → E → F. Then, it is returned to the hydraulic oil tank 33. Then, as the hydraulic piston 52 rises, the amount of pressurized oil flowing from D to E increases, and the hydraulic piston 52 stops at a position that is in balance with the discharge amount of the hydraulic pump 32, and neither rises nor descends. Has become.

In this case, hydraulic piston positioning motor 61, feed screw 6
2. By controlling the position of the needle 57 via the nut 63 and the bell crank 64, the stop position of the hydraulic piston 52 can be controlled. That is, the lower frame 13
The stop position of the can be controlled. As a result, the stop position of the lower frame 13 is controlled so that the desired shape can be processed.

After the hydraulic piston 52 stops as described above, the needle 57 is gradually pulled up by the mechanism from the hydraulic piston positioning motor 61 to the bell crank 64 described above, so that the movement of the hydraulic piston 52 is moved. You can follow the. That is, the hydraulic piston positioning motor 61 controls the hydraulic piston.
Not only the stop position of 52, but also its rising speed, that is, the processing speed can be adjusted. When lowering the lower frame 13, release the foot pedal 36 to move B → C.
Hydraulic path is opened and the pressurized oil returns to the hydraulic oil tank 33 via the path B → C, while the hydraulic piston 52 is connected to the lower frame.
The pressure oil in the hydraulic cylinder 51 is returned to the hydraulic oil tank 33 through the route of D → B → C by being lowered by the weight of 13 and the hydraulic piston 52 itself.

On the other hand, the pressure transducer shown in FIG. 4 via the route A → B → G.
Since the pressurized oil reaching 71 is normally equivalent to the pressure inside the hydraulic cylinder 51, the pressure transducer 71 multiplies the pressurized area of the hydraulic cylinder 51 by the pressure of the pressurized oil to apply the pressure to the hydraulic piston 52. You can know it. That is, the pressure converter 71 can take out the applied pressure of the hydraulic piston 52 as a digital electric signal, and constitutes the pressure detecting means 2 in the schematic configuration of FIG. Strictly speaking, from the pressing force obtained above, the lower frame 1
3, the net processing pressure is obtained by subtracting the weight of the lower die 19 and the processing material 20, but the total of these weights is usually sufficiently smaller than the processing pressure that it can be ignored, but it is not necessary. If there is, it can be converted by adding a correction circuit to the pressure converter 71.

As shown in FIG. 4, the numerical control system for controlling each drive unit includes a pressure storage unit 81, a pressure comparison unit 91, a back gauge position storage unit 101, a hydraulic piston position storage unit 111, a keyboard 121, and a process progress. Conversion circuit 131, setting pressure elimination circuit 14
1, a pressing force coefficient setting circuit 151, an overload signal amplifier 161, a reset circuit 191, and the like.

In this numerical control unit, the pressure storage unit 81, the pressure comparison unit 9
1, the back gauge position storage unit 101 and the hydraulic piston position storage unit 111 each have 1 to n storage areas (n indicates the maximum number of steps required, the same applies below), and the pressure storage unit 81
Is the area 1a where each storage area stores the maximum value of the operating pressure.
~ Na and area 1b that temporarily stores the operating pressure for each process ~
It is divided into two areas, nb. The areas 1a to na correspond to the storage means 3 in the above-mentioned general structure. The pressure comparison unit 91 has areas 1c to nc, compares the numerical values of the respective areas 1a to na, 1b to nb corresponding to the respective input terminals of the pressure storage unit 81, and determines the pressure coefficient setting circuit 151 (allowable pressure setting). When the numerical values in the areas 1b to nb become larger than the value obtained by multiplying the coefficient β (for example 1.20) designated by the means) by the numerical values in the areas 1a to na, the overload signal (corresponding to the stop signal S) is immediately generated. ) Is sent to the overload signal amplifier 161. That is, the multiplying function of the pressing force coefficient setting circuit 151 and the pressure comparing section 91 corresponds to the allowable pressure setting means 4, and the comparing function and the signal output function of the pressure comparing section 91 correspond to the comparing means 5. is there. Note that the coefficient β is normally set to an arbitrary value and is always constant, and can be changed by the keyboard 121 only when necessary.

The back gauge position storage unit 101 has areas 1 to nl, and the hydraulic piston position storage unit 111 has areas 1d to nd.
The back gauge positioning motor 21 is controlled by the back gauge positioning motor drive circuit 26 based on the respective stored values of, and the position is fed back by the back gauge position detector 25 which is directly connected to the back gauge positioning motor 21. Is stopped at a predetermined position. Also, the hydraulic piston positioning motor 61
Also, the hydraulic piston position storage unit 111, the hydraulic piston positioning motor drive circuit 66, and the hydraulic piston position detector 65 similarly stop at a predetermined position.

Further, the process progress switching circuit (process progress switching means) 131 is
Foot pedal switch linked to the operation of foot pedal 36
When the output signal of the logical product (AND) circuit 133 of the signal of 132 and the positioning completion signal output from the hydraulic piston positioning drive circuit 66 is input, it is considered that one process is completed, and each storage unit 81, 101, The connection of the input / output circuits of the respective memory areas of 111 and the pressure comparison unit 91 is advanced by one step at a time. Further, the input / output circuits of the respective storage units 81, 101, 111 and the pressure comparison unit 91 can be connected to arbitrary process positions by a command from the keyboard 121.

Further, from the keyboard 121, the back gauge position storage unit 10
1, the same process number of the hydraulic piston position storage unit 111 (for example,
3l, 3d) enter a predetermined numerical value to process the first process. At this time, the processing pressure is converted into a digital electric signal by the pressure converter 71, and is displayed on the digital display 72 for visual confirmation, and at the same time, a for pressure setting memory of the pressure memory 81 is stored.
In the area (3a) and the temporary storage area b (3b), the maximum value of the operating pressure in that process is stored. In this manner, the steps of the processed product are sequentially advanced, and when the final step is completed, the step progress switching circuit 131 causes the first step position (3
l, 3d, 3a, 3b, 3c) each storage unit 81, 101, 111, pressure comparison unit 9
1 I / O circuit is connected. At this time, the pressure comparison unit 91
Compares the numerical values of areas a and b of the pressure storage unit 81 in each process area. In this case, since a = b is always satisfied, the overload signal is output as described above. However, even if an overload occurs, the press brake body 11 and the dies 18, 19 will not be protected, as will be described later, so caution is required in the work. It should be noted that the processing start does not necessarily have to start from 1 in each area, and the processing can be started from any position less than n designated by the keyboard 121.

As described above, the first working of the processed material 20 is completed, and the normal operating pressure is stored in the area a of the pressure storage unit 81. Therefore, in each process of the second and subsequent processes, the signal output from the pressure converter 71 is the pressure storage unit 81.
Since the area a of each step has a numerical value already stored, it is automatically input to the area b, and the already stored numerical value is erased and rewritten to the newly input actuating force. . Therefore, the pressure comparison unit 91 sequentially compares the numerical values of the regions a and b of each process of the pressure storage unit 81, and as described above, the constant coefficient β is multiplied by the numerical value of the region of a to calculate the value of the region of b. When the value becomes large, the overload signal is immediately sent to the overload signal amplifier 161. The amplified overload signal is divided into three parts. One of them is to reach the solenoid valve controller 43 to turn off the power of the solenoid coil 42 of the solenoid valve 41 to lose its excitation. Therefore, the solenoid valve 41 is brought into the state shown in FIG. 5 by the spring 44, and the pressurized oil pressurized by the hydraulic pump 32 returns to the hydraulic oil tank 33 through the route of A → H, and enters the hydraulic cylinder 51. Since the pressurized oil also returns to the hydraulic oil tank 33 through the route of D → I → J, it is possible to prevent overload from occurring in the molds 18 and 19 even when the foot pedal 36 is still depressed. One of the overload signals reaches the hydraulic drive motor controller 171 and the overload alarm controller 181. Immediately turn off the power of the hydraulic drive motor 32 and stop it. At the same time, the overload alarm controller 181 causes the alarm indicator 182.
A buzzer (not shown) is activated to notify the operator of the abnormality. That is, the solenoid valve controller 43 and the hydraulic drive motor controller 171 correspond to the stopping means 6 in the above-mentioned general configuration.

In order to reliably perform the above operation, it is important to employ a solenoid valve 41 having a sufficiently large diameter and a quick switching time, and a hydraulic pipe having a sufficient thickness and a shortest distance. Further, after stopping due to the above-mentioned overload, after confirming that there is no abnormality in each part, it is possible to operate the reset circuit 191 by the keyboard 121 to stop the overload signal output and return to the normal work. . Further, the pressure storage unit 81
When you want to erase or update the value in area a of
In response to the command 121, the set pressurizing force erasing circuit 141 is operated to erase the memory in the areas a and b of the pressure storage unit 81, and it can be updated in the same manner as when the first processed product is processed.

All the numerical values of the numerical control device can be stored in a cassette magnetic tape, a flexible disk device (not shown), or the like for reuse. Also,
In this device, the pressure can be directly converted into an electric signal by a strain gauge or the like that is appropriately mounted between the pressurizing mechanism part and the mold mounting part, and can be input to the pressure converter 71. By using the hydraulic pressure of the overload prevention device, which has a set of hydraulic cylinders and pistons instead of such shear plates, as the input of the pressure converter 71, the mechanical pressurization mechanism such as a crank press is overloaded. It can also be used as a load prevention device.

"Effects of the Invention" In the overload prevention device in the press working machine according to the present invention, the pressing force of the press working machine is detected by the pressure detecting means at the first to nth steps of the first press working, and each step is performed. Each maximum value of the pressing force is sequentially stored in the first to nth storage areas of the storage means. On the other hand, when performing the press work after the next time, the process progress switching means detects the process progress by the press working machine, and the press working machine performs the i-th step (i.
= 1,2, ..., n), the i-th storage area is selected, and the allowable pressure value setting means sets a predetermined margin to the maximum pressing force stored in the selected i-th storage area. The allowable pressure value in the i-th step is calculated by multiplying by. Further, by the comparison means, the allowable pressure value in the i-th step,
The operating pressure applied by the pressure detecting means during the actual i-th step is compared, and a stop signal is output when the pressure value of the latter exceeds the pressure value of the former, and the stop means outputs the stop signal. Immediately stop the press operation based on. Therefore, even if the press working consists of multiple steps and the allowable pressure values are different for each step, it is possible to judge whether or not the applied pressure is excessive based on the allowable pressure value adapted to each step. It is possible to prevent overloading each time, prevent damage to the mold, and reduce the incidence of defective products.

[Brief description of drawings]

FIG. 1 is a block diagram showing the schematic configuration of an embodiment of an overload prevention device according to the present invention, and FIGS. 2 to 5 show respective parts when the embodiment according to the present invention is applied to a press brake. FIG. 2 is a schematic front view of the press brake, FIG. 3 is a vertical cross-sectional view taken along the line III-III of FIG. 2, FIG. 4 is a block diagram showing a control unit, and FIG. FIG. 6 is a view showing another state of the valve, and FIG. 6 is a view for explaining a problem in the conventional example. 1 ... Pressing machine, 2 (71) ... Pressure detector (pressure converter), 3 (81) ... Memory means (pressure memory section), 4 (91, 151) ... Allowable pressure value setting means ( Pressure comparison part,
Pressure coefficient setting circuit), 5 (91) …… Comparison means (pressure comparison section), 6 (43,171) …… Stop means (solenoid valve controller, hydraulic drive motor controller) 131 …… Process progress switching circuit ( Process progress switching means)

Claims (1)

[Claims] 1. When press working consisting of the first to nth steps (n is an arbitrary integer of 2 or more) is carried out by the same press working machine, when the working pressure in each step becomes excessively large. An overload prevention device for stopping the press operation, which has pressure detection means for detecting an operating pressure of the press working machine, and first to n-th storage areas. Storage means for respectively storing the maximum value of the operating pressure detected by the pressure detection means during the first to nth steps of the press working, and the progress of the step by the press working machine is detected, and the press working machine performs the i-th step. When performing (i = 1, 2, ..., N), the process progress switching unit that selects the i-th storage region, and the maximum pressing force stored in the i-th storage region that is selected by the process progress switching unit. The i-th step Allowable pressure value setting means for setting the allowable pressure value in step 1, the allowable pressure value in the i-th step set by the allowable pressure value setting means, and the actuation force detected by the pressure detecting means during the actual i-th step. Comparing with the pressure, it comprises a comparing means for outputting a stop signal when the pressure value of the latter becomes equal to or higher than the pressure value of the former, and a stopping means for stopping the press operation based on the stop signal of the comparing means. An overload prevention device for a press machine.