JPH0215900A - Device for prevention of overload in press machine - Google Patents

Abstract

PURPOSE:To improve the safety of operation and to prevent a defective from occurring by comparing an allowable pressure value with an operating pressure detected by a pressure detecting means at each stage and supplying a stop signal when the operating pressure over the allowable pressure value acts. CONSTITUTION:At the first working time, the operating pressure of a press machine 1 is detected by a pressure detecting means 2 at each stage and the maximum value of the operating pressure at each stage is stored by a storage means 3. On and after the 2nd working time, an allowable pressure value at each stage obtained by multiplying a fixed allowance rate to the maximum value of the operating pressures at each stage in the 1st work stored in a storage means 3 is set by a setting means 4 for the allowable pressure value. The allowable pressure value and the operating presure detected by the pressure detecting means 2 are compared by a comparison means 5 at each stage. When an operating pressure over the allowable pressure value is generated in a pressing machine 1, a stop signal S is supplied from the comparison means 5 to a stop means 6 to break the power source of the pressing machine 1 and at once to halt pressing operation.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to an overload prevention device for a press machine, and is suitable for use in a press machine that performs continuous processing using, for example, numerical control. Related to load protection devices.

``Prior art'' Preventing overload from occurring in press processing machines is an important issue from the viewpoints of work safety, protection of molds and press processing machines, and prevention of defective products. Various methods have been implemented in the past.

For example, there is a method called the Sharp plate method. This consists of a pair of punches and dies located between the pressurizing mechanism section and the mold mounting section, and is called a shear plate, which is selected so that the punch can be punched out at the same pressure as the maximum allowable press force of the press processing machine. It consists of an inserted steel material, and when the overload exceeds the maximum allowable pressure, this steel material is punched out by the punch and die.
The punch penetrates into the gouging hole to shorten the distance between the pressure mechanism and the mold attachment, reducing the pressure from the processing mechanism to the mold attachment and preventing overload. .

In addition, in place of the punch, gouge, and shear plate, a set of hydraulic cylinders and pistons are provided between the pressurizing mechanism and the mold mounting section, and when the maximum allowable pressurizing force is applied, the pressure inside the hydraulic cylinder is Some attempts were made to achieve a similar effect by installing a relief valve to release pressure oil.

``Problems to be Solved by the Invention'' However, the set pressure of the overload protection device in the above two examples is generally close to the allowable maximum pressure of the press machine body, and therefore When a mold is used, there is a problem in that it is not effective in protecting the mold.

In addition, even if the relief valve mechanism is variable in the hydraulic cylinder and piston system, it must be adjusted each time the mold is replaced, and the reproducibility of the set pressure may be affected by changes in oil temperature or the spring mechanism of the relief valve. This poses a problem due to instability, and although it can be used for mass production with few mold setup changes, it is suitable for work where the pressurizing force changes for each process, such as with a press machine that uses numerical control. is all (could not be used.

In other words, when bending a workpiece 1 having a long piece a and a short piece as shown in FIG. Since pressure is applied, the operating pressure at that time is different, so if you can only set the maximum allowable pressure as mentioned above, the mold is likely to be destroyed and there are issues with safety, the possibility of defective products, etc. There was a problem that they could not be hired because of this.

The present invention was proposed in view of the above circumstances, and its purpose is to provide an overload prevention device for a press machine that can be applied to continuous processing by setting a pressure value that matches the operating pressure force. It's about doing.

"Means for Solving the Problems" The overload prevention device according to the present invention includes a pressure detection means for detecting the operating pressure of a press machine, and a pressure detection means for detecting pressure detected by the pressure detection means during press processing in each initial step. a storage means for storing the maximum value of the working pressurizing force for each process, and an allowable pressure value for each process by multiplying the maximum value of the working pressurizing force for each process stored by the storing means by a predetermined margin rate. and after setting an allowable pressure value by the allowable pressure value setting means, comparing the allowable pressure value and the operating pressure detected by the pressure detecting means for each process, The press includes a comparison means for outputting a stop signal when the latter pressure value exceeds the former pressure value, and a stop means for stopping the press operation based on the stop signal from the comparison means.

"Operation" According to the overload prevention device of the present invention, the operating pressure of the press machine is detected by the pressure detection means during the initial processing of each process, and the maximum value of the operating pressure for each process is stored. After the next machining, the allowable pressure value for each process is set by multiplying the maximum value for each process of the initial operating pressure stored in the storage means by a certain margin rate. The comparison means compares the allowable pressure value and the operating pressure detected by the pressure detection means for each process, and when an operating pressure greater than the allowable pressure value is applied, the comparison means sets the allowable pressure value. A stop signal can be supplied to the stop means to immediately stop the press.

“Example” An example of the overload prevention device according to the present invention is shown in FIGS. 1 to 5.
This will be explained based on the diagram.

First, the general structure of the overload prevention device of this embodiment will be briefly explained using the block diagram shown in FIG. a pressure detection means 2 such as a press machine, a storage means 3 for storing the maximum value of the operating pressure for each process of the press processing machine 1 detected by the pressure detection means 2 during the first press working, and the 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 pressure stored by by a predetermined margin rate.
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 exceeds the former pressure value, It consists of a comparison means 5 which outputs a stop signal, and a stop means 6 which turns off the power and stops the pressing operation based on the stop signal S of the comparison means 5.

That is, the overload prevention device having such a configuration detects the operating force of the press machine 1 for each process during the first machining process, and detects the maximum value of the operating force for each process. is memorized by the storage means 3, and for the second and subsequent machining, the allowable value for each process is calculated by multiplying the maximum value of the operating pressure for each process for the first time stored in the storage means 3 by a certain margin rate. A pressure value is set by the permissible pressure value setting means 4, and the permissible pressure value and the operating pressure detected by the pressure detecting means 2 are compared for each process by the comparing means 5, and the operation is determined to be greater than or equal to the permissible pressure value. The pressing force is press processing machine l
When this occurs, the comparison means 5 supplies the stop signal S to the stop means 6, and the stop means 6 can turn off the power to the press processing machine 1 and immediately stop the press operation.

Next, a specific example of the use of the above-mentioned overload prevention device in a press brake will be described in detail with reference to FIGS. 2 to 5. First, in FIG. 2, the press brake body 11
, two to four tie rods 15 passing through the upper frame 12, the lower frame 13, and the base i4, and the tie rods! The same number of spacer tubes 16 are placed over the outer circumference of 5.
It is composed of.

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

In addition, a mounting jig (path shown) is installed on the bottom surface of the upper frame I2.
Usually a convex V-shaped upper mold through the! 8 is the lower frame 13
A concave V-shaped lower mold 19 is attached to the upper surface via a mounting jig, and the upper mold! 8 and the lower mold 19, the workpiece 2
Place 0 and lower frame! 3 is raised to perform processing. The processing position of the workpiece 20 is determined by the back gauge positioning motor 21 via a ball screw 22 and a ball nut 23, which are directly connected to the back gauge positioning motor 21, as shown in FIG. This is done by moving the gauge 24.

This back gauge 24 is guided by a linear guide (path shown) and moves linearly.

A series of mechanisms from the back gauge positioning motors 2, 1 to the pole screws 22, pole nuts 23, and linear guides are shown in only one set in FIG. 3, but normally one set each is provided on the left and right. The back gauge positioning motor 21 is rotated left and right synchronously by a back gauge positioning motor drive circuit 26.

Further, as shown in the lower part of FIG. 2, the drive system for driving the lower frame 13 up and down is connected to a hydraulic oil tank 33 by a hydraulic pump 32 directly connected to a hydraulic drive motor 31.
The hydraulic oil 34 stored in is sucked up and guided to the hydraulic cylinder 51 on the base 14 via the solenoid valve 41. When the hydraulic oil 34 is supplied to the hydraulic cylinder 51, the hydraulic piston 52
, the lower frame 13 is pushed up to perform processing. This drive system also includes a tension spring 35.
Since the ball 38 inside the operating valve 37 is lowered until the foot pedal 36, which is lifted by → C, the lower frame 13 is configured to return to the hydraulic oil tank 33 via
is designed not to rise. By gradually depressing 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 rotation speed of the hydraulic pump 32 is constant, the ball 38 is not discharged. Since the oil pollution caused by the hydraulic cylinder 51 is also constant,
As oil buildup gradually increases, the hydraulic piston 52 gradually begins to rise, and when the pedal 36 is fully depressed, the ball 38 completely closes the B-C hydraulic path and reaches the maximum pressure. The flow reaches the hydraulic cylinder 51 via the electromagnetic valve 41, and processing is performed.

In addition, the solenoid coil 42 of the solenoid valve 41 is always energized during normal operation, so it is in the state shown in FIG.
The pressurized oil has reached the hydraulic cylinder 51.

Also, the hydraulic piston 52 is raised inside the hydraulic cylinder 51 by the pressurized oil, and when it rises to a certain position, it is built in a sleeve 53 that is attached to the hydraulic piston 52 and rises together with the hydraulic piston 52, and is pushed up by a spring 54. The ball 56, which is in close contact with the valve seat surface 55 of the sleeve 53, is pushed down by the needle 57 that also passes through the center of the sleeve 53, increasing the distance between the ball 56 and the valve seat surface 55, and pressurized oil flows into the ball. 56 and valve seat surface 5
A passage 5 provided on the side of the sleeve 53 passing between the passage 5 and the sleeve 53.
8 and is returned to the hydraulic oil tank 33 via the route D→E→F. As the hydraulic piston 52 rises, the amount of pressurized oil flowing D4E increases, and the hydraulic piston 52 stops at a position where it is balanced with the discharge amount of the hydraulic pump 32, and neither rises nor falls.

In this case, the stop position of the hydraulic piston 52 can be controlled by controlling the position of the needle 57 via the hydraulic piston positioning motor 61, feed screw 62, nut 63, and bell crank 64. In other words, the stopping position of the lower frame 13 can be controlled. This makes it possible to control the stopping position of the lower frame 13 and process the desired shape.

Further, after the hydraulic piston 52 has stopped as described above, the movement of the hydraulic piston 52 is controlled by gradually pulling up the needle 57 by the mechanism from the hydraulic piston positioning motor 61 to the bell crank 64.
It is now possible to follow the movements of 7.

That is, by controlling the hydraulic piston positioning motor 61, not only the stopping position of the hydraulic piston 52 but also its rising speed, that is, the machining speed can be adjusted. In addition, when lowering the lower frame 13, the hydraulic path B-C is opened by releasing the foot pedal 36, and the pressurized oil is transferred to the B-C hydraulic path.
→ Return to the hydraulic oil tank 33 via the path C, while the hydraulic piston 52 is connected to the lower frame 13 and the hydraulic piston 52.
It descends due to its own weight, and the pressurized surface within the hydraulic cylinder 51 returns to the hydraulic oil tank 33 via the path D→B−+C.

On the other hand, the pressurized oil that reaches the pressure transducer 71 shown in FIG.
The hydraulic piston 52 is obtained by multiplying the pressure of the pressurized surface by the pressure of the pressurized oil.
It is now possible to know the applied force. That is, this pressure transducer 71 can extract the pressing force of the hydraulic piston 52 as a digital electric signal, and constitutes the pressure detection means 2 in the general configuration shown in FIG. Strictly speaking, from the pressing force obtained above,
Lower frame 13, lower mold! 9. The net machining pressure is what is obtained by subtracting the weight of the workpiece 20. Normally, the sum of these weights is sufficiently small compared to the machining pressure, so there is no problem in ignoring it, but if necessary, pressure conversion can be done. The conversion can be performed by adding a correction circuit to the converter 71.

As shown in FIG. 4, the numerical control system that controls each drive section is a pressure storage section 81. Pressure comparison section 91, back gauge position storage section 101. Hydraulic piston position memory section! 11
, keyboard 121, process progress switching circuit 131, set pressurizing force erasing circuit 141, pressurizing force coefficient setting circuit 151. It is composed of an overload signal amplifier 161, a reset circuit 191, and the like.

In this numerical control section, a pressure storage section 81, a pressure comparison section 91. The back gauge position storage unit 101 and the hydraulic piston position storage unit 111 each have ζ 1 to n storage areas (n indicates the maximum number of required steps, hereinafter), and the pressure storage unit 81 has each storage area. is divided into two areas: a region 1a=na where the maximum value of the operating pressure is stored, and an area 1b=nb where the operating pressure for each process is temporarily stored. These areas 1a-na correspond to the storage means 3 in the above-mentioned general configuration. Further, the pressure comparison section 91 has a region 1c=nc
The numerical values of each area 1a-na, 1b-nb corresponding to each input terminal of the pressure storage unit 81 are compared, and the coefficient β ( For example, when each value in area 1b=nb becomes larger than the value obtained by multiplying 1.20) by each value in area 1a=na, an overload signal (corresponding to the stop signal S) is immediately sent to the overload signal amplifier 161. It looks like it will be sent to. That is, the multiplication function of the pressurizing force coefficient setting circuit 151 and the pressure comparison section 91 corresponds to the allowable pressure setting means 4, and the comparison function and signal output function of the pressure comparison section 91 correspond to the comparison means 5.
It is equivalent to . Note that the coefficient β is normally kept constant at an arbitrary value, and can be changed using the keyboard 121 only when necessary.

In addition, the back gauge position storage section 101 is a region! Q=n(
1. Hydraulic piston position memory section 11'l is a region! d～nd
It has each area of back gauge position storage lot.
The back gauge positioning motor 21 is controlled by the back gauge positioning motor drive circuit 26 based on the stored values of each process 1Q-nQ, and the back gauge position detector 25 is directly connected to the back gauge positioning motor 21.
The position is fed back by the back gauge 2.
4 can be stopped at a predetermined position. Also,
The hydraulic piston positioning motor 61 is similarly stopped at a predetermined position by a hydraulic piston position storage section ttL hydraulic piston positioning motor drive circuit 66 and a hydraulic piston position detector 65.

Further, the process progress switching circuit 131 receives an output signal from a logical product (AND) circuit 133 of a signal from a foot pedal switch 132 linked to the operation of the foot pedal 36 and a positioning completion signal output from the hydraulic piston positioning drive circuit 66. When this is done, it is assumed that one step has been completed, and the connection of the input/output circuits of each storage area of each storage section 81, 101, Ill, and pressure comparison section 91 is proceeded by one step at the same time. Further, each storage section 81,lot is stored at an arbitrary process position according to a command from the keyboard 121.

t t l, and the input/output circuit of the pressure comparator 91 can also be connected thereto.

Also, from the keyboard 121, the back gauge position storage unit lO! , input a predetermined numerical value to the same process number (for example, 3C, 3d) in the hydraulic piston position storage section 111, and process the first process. At this time, the machining pressure is converted into a digital electric signal by the pressure converter 7I and displayed on the digital display 72 for visual confirmation. b for memory
The maximum value of the operating pressure in that process is stored in area (3b). In this way, the process of the processed product is sequentially advanced, and when the final process is completed, the process progress switching circuit 13
1, the first process position (3Q, 3 d, 3
a.

3 b, 3 c) each storage section 81.1011 lit
, the input/output circuit of the pressure comparison section 91 is connected. At this time, the pressure comparison section 91 performs pressure storage section 8 in each process area.
The numerical values in each area a and area b of 1 are compared, but in this case a=b is always true, so an overload signal will not be output as described above, but in the unlikely event that an overload condition occurs, Even if this happens, the press brake body 11 and the molds 18 and 19 will not be protected as will be described later, so sufficient caution is required during the work. Note that processing does not necessarily have to start from 1 in each area, but is configured so that it can start from any position less than n specified on the keyboard 121.

As a result of the above, the first machining of the workpiece 20 is completed, and the normal operating pressure is stored in the area a of the pressure storage section 81. Therefore, in each step of the second and subsequent machining processes, the signal output from the pressure transducer 71 is automatically input into the area b of the pressure storage section 81, since there are already stored values in the area a of each process. The system is configured to erase the already stored numerical values and rewrite them with the newly input operating pressure force. Therefore, the pressure comparator 91
The numerical values in the a and b areas of each process in the pressure storage unit 81 are compared sequentially, and the value in the b area is larger than the value obtained by multiplying the constant coefficient β by the numerical value in the a area as described above. When this occurs, 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 and cut off the power to the solenoid coil 42 of the solenoid valve 41 to lose its excitation. Therefore, the solenoid valve 41 was brought into the state shown in FIG. 5 by the spring 44, and the pressurized oil pressurized by the hydraulic pump 32 returned to the hydraulic oil tank 33 via the path A-H, and then entered the hydraulic cylinder 51. Pressurized oil also returns to the hydraulic oil tank 33 via the path D41→J, so even if the foot pedal 36 is kept depressed, the overload will not be removed from the mold I8! 9 can be prevented from occurring. One overload signal reaches the hydraulic drive motor controller 171 and the overload alarm controller 181;
Immediately cut off the power to the hydraulic drive motor 32 and stop it, and at the same time, the overload alarm controller 181 turns on the alarm indicator 1.
B2 or a buzzer (not shown) can be activated to notify the operator of an abnormality. That is,
These solenoid valve controller 43 and hydraulic drive motor controller 1
Reference numeral 71 corresponds to the stopping means 6 in the above-mentioned general configuration.

In order to ensure the above-mentioned effect, it is important to employ a solenoid valve 41 with a sufficiently large diameter that has a quick switching time, and a hydraulic piping that is sufficiently thick and has the shortest distance. Furthermore, after the machine has stopped due to the above-mentioned overload, after confirming that there is no abnormality in each part, it is possible to activate the reset circuit 191 using the keyboard 121 to stop outputting the overload signal and return to normal work. . Furthermore, when it is desired to erase or update the numerical values in area a of the pressure memory section 81, the set pressurizing force erase circuit 141 is activated by a command from the keyboard 121 to erase the memories in areas a and b of the pressure memory section 81, as described above. It can be updated in the same way as when processing the initial processed product.

Note that 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. In addition, this device is also capable of directly converting the pressing force into an electrical signal using a strain gauge or the like appropriately installed between the pressurizing mechanism section and the mold mounting section, and inputting the signal manually to the pressure transducer 71.
By using the hydraulic pressure of the overload prevention device, which has a set of hydraulic cylinders and pistons instead of the shear plate as described above, as input to the pressure transducer 71, a mechanical pressurizing mechanism such as a crank press can be used. It can also be used as an overload protection device.

"Effects of the Invention" According to the overload prevention device of the present invention, the operating pressure of the press processing machine is detected by the pressure detection means during the initial processing for each process, and the maximum operating pressure for each process is detected by the pressure detection means. The value is stored in the storage means, and from the next machining onwards, the allowable pressure value for each process is set by multiplying the maximum value of the initial operating pressure for each process stored in the storage means by a certain margin rate. and compares the operating pressure detected by the pressure detection means after the setting with a comparison means for each step,
When an operating pressure greater than the allowable pressure value is applied, a stop signal is supplied from the comparison means to the stop means to immediately stop the press. Therefore, numerical control allows continuous machining with different operating pressures. Also, by changing the allowable pressure value set each time, overload can be prevented for each process.
This has the effect of improving work safety, protecting the mold and press machine body, and preventing the production of defective products.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the general configuration of an embodiment of an overload prevention device according to the present invention, and FIGS. 2 to 5 show each part when the embodiment according to the present invention is applied to a press brake. 2 is a schematic front view of the press brake, and FIG. 3 is a vertical sectional view taken along line I [I=III in FIG.
FIG. 4 is a block diagram showing the control section, FIG. 5 is a diagram showing other states of the solenoid valve, and FIG. 6 is a diagram for explaining problems in the conventional example. l... Press processing machine, 2 (71)... Pressure detector (pressure transducer), 3
(81)... Memory means (pressure memory section), 4 (9
1,151)... Allowable pressure value setting means (pressure comparison section, pressure coefficient setting circuit), 5 (91)... Comparison means (pressure comparison section), 6 (
43,171)...Stopping means ('1! Magnetic valve controller, hydraulic drive motor controller). Figure 1

Claims (1)

[Scope of Claims] Pressure detection means for detecting the operating pressure of a press processing machine, and storing the maximum value of the operating pressure detected by the pressure detection means for each process during initial press processing for each process. storage means for setting the permissible pressure value for each process by multiplying the maximum value of the operating pressure for each process stored by the storage means by a predetermined margin rate; After the allowable pressure value is set by the value setting means, the allowable pressure value and the operating pressure detected by the pressure detecting means are compared for each process, and when the latter pressure value is equal to or higher than the former pressure value. What is claimed is: 1. An overload prevention device for a press machine, comprising: a comparison means that sometimes outputs a stop signal; and a stop means that stops a press operation based on the stop signal of the comparison means.