JP3316980B2 - Crack occurrence detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for detecting cracks generated in a shaft such as a tie bar in a device having a clamping mechanism such as a die casting machine or a press machine.

[0002]

2. Description of the Related Art In a die casting machine, stress is concentrated on a nut fixing portion or a step portion of a tie bar at the time of mold clamping, and a crack may occur. Conventionally, an ultrasonic flaw detector has been used for detecting such a crack, which uses the principle that transmitted ultrasonic waves are reflected at a crack portion, and detects the occurrence of a crack based on the intensity of a reflected wave.

[0003]

However, in the crack detection by the ultrasonic flaw detector, the probe for transmitting and receiving the ultrasonic wave cannot always be kept in contact with the tie bar. In order to transmit ultrasonic waves efficiently, it is necessary to apply and form an oil film on the surface of the tie bar, and the measurement is troublesome. Therefore, cracks cannot always be detected. Therefore, it was difficult to find a relatively small crack before it became unusable and quickly replace the tie bar. In addition, there has been difficulties in detection certainty, such as erroneous detection due to a defective echo and individual differences in measurement data.

An object of the present invention is to provide a crack occurrence detecting device of a tightening mechanism capable of reliably and constantly detecting a crack in a shaft on which a tightening reaction force such as a tie bar acts.

[0005]

To explain the structure of the present invention, a signal corresponding to the amount of distortion is output to the shaft surfaces of the general portions of the shafts 41 and 42 on which the tightening reaction force acts, where the frequency of occurrence of cracks is small. In addition to mounting the strain gauge 5, means 6 for inputting an output signal of the strain gauge 5 and determining the occurrence of a crack when the output signal becomes smaller than a predetermined value is provided.

[0006]

[Function] In a shaft on which a tightening reaction force acts, cracks occur frequently at a specific portion. When no crack is generated, the distortion amount shows almost the same value in any part of the shaft. However, when a crack is generated in a specific portion, the distortion amount increases in this portion, and the distortion amount in the remaining general portion decreases. Thus, since the output signal of the strain gauge provided in the general portion becomes smaller than the predetermined value, the occurrence of cracks is reliably known without causing individual differences among the measurers.

[0007] Since the strain gauge can always be mounted on the shaft surface, it is possible to constantly monitor the occurrence of cracks. Thus, relatively small cracks before the shaft became unusable are detected without undue delay,
The shaft can be replaced according to the operating state of the tightening mechanism without lowering the productivity.

[0008]

FIG. 1 shows an entire die casting machine provided with a crack occurrence detecting device according to the present invention. In the figure, base 1
A fixed platen 21 and a movable platen 22 are provided facing each other, and the fixed platen 21 to which the injection cylinder 31 is connected is fixed to the base 1, while the movable platen 22 can be moved in a horizontal direction within a certain range. It is. The dies 31 and 32 are held on the platens 21 and 22, respectively. When the movable platen 22 approaches the fixed platen 21, the dies 31 and 32 are brought into close contact with each other to perform mold clamping.

The fixed platen 2 with the movable platen 22 interposed therebetween
On the side opposite to 1, a link housing 23 equipped with a mold clamping cylinder 32 is provided, and the link housing 23 can move in a horizontal direction within a certain range on the base 1. The platens 21 and 22 and the link housing 23
Tie bars 41, 42, which are shafts at four places, up, down, left, and right
Penetrate (only the upper and lower two are shown). One end of each of the tie bars 41 and 42 is connected to the fixed platen 21 by a tie bar nut 43, and the other end is connected to the link housing 23 by worm wheel nuts 44A and 44B, which will be described in detail later.

The guide bar 3 extends from the mold clamping cylinder 32 to the movable platen 22 through the link housing 23.
The guide bar 33 is connected to the movable platen 22 via a toggle mechanism described later at an intermediate position. A product pushing cylinder 34 is provided at the tip of the guide bar 33.

Movable platen 22 and link housing 23
Strain gauges 5 are attached to part of the surface of each of the tie bars 41 and 42 between them, and output signals of these strain gauges 5 are input to the control device 6. A control panel 11 is provided in contact with the base 1, and equipment is stopped from the control device 6 to the control panel 11.
Each signal of the mold clamping force adjustment is output.

FIGS. 2 and 3 show the worm wheel nut 4.
4A and 4B show a rotary drive mechanism. The upper and lower tie bars 41 and 42 penetrating the link housing 23 are formed with screws at their respective ends, to which worm wheel nuts 44A and 44B are respectively connected. A tooth profile is formed on the outer periphery of each worm wheel nut 44A, 44B, and the worm gear 45A, 45B meshes with the tooth profile. The rotating shaft 46A of the upper worm gear 45A has a bevel gear 47A,
It is connected to a hydraulic motor 49 by 48A. Also,
The rotating shaft 46B of the lower worm gear 45B is a bevel gear 48B.
It is further connected to the bevel gear 48A via a ball joint 71. The rotating shafts of the left and right worm gears (the right side is not shown) are connected to each other by ball joints 72 and 73.

On the fixed platen 21 side, tie bars 41, 4
2 is fixed to this end, by appropriately rotating the hydraulic motor 49, the link housing 23 is retracted (rightward in FIG. 3) at the time of mold clamping, and tightening acting on the tie bars 41, 42 is performed. The reaction force can be reduced.

FIG. 4 shows details of a toggle mechanism provided between the movable platen 22 and the link housing 23. A crosshead 35 is mounted on a guide bar 33 protruding from the mold clamping cylinder 32, and links 36A and 36B are interposed above and below the guide bar 33, respectively.
A and 37B are connected. One end of each of the links 37A and 37B is connected to the link housing 23, and the other ends of the links 38A and 38B having one ends connected to the movable platen 22 are connected to the corners of the links 37A and 37B. I have. Thus, the two link pairs 37 constituting the toggle mechanism
A, 38A and 37B, 38B take a deep V-shape as the guide bar 33 retreats into the mold clamping cylinder 32, and when the guide bar 33 advances, it changes from a shallow V-shape to a substantially horizontal state as shown in the figure. .

The principle of such a toggle mechanism will be described with reference to FIG. 5. When the connecting point of the deep V-shaped links 37 and 38 is pushed with a force P, the entirety of the V-shaped link 37, 38 is made shallow to reduce the angle θ.
When deformed into a letter shape, the outward force F generated at the tip of each link 37, 38 increases rapidly as the angle θ decreases, as shown in FIG. Thus, the output of the mold clamping cylinder 32 is greatly amplified by the toggle mechanism and becomes the mold clamping force of the movable platen 22. At this time, a reaction force proportional to the mold clamping force acts on the tie bars 41 and 42.

FIG. 7 shows details of the strain gauge 5 mounted on the tie bar 41. The strain gauge 5 is formed by a so-called 4-active dummy method. Two gauges 51, 52, 53, 54 are attached to the upper and lower positions on the tie bar surface in directions different from each other by 90 degrees, and the gauges 51, 52 reduce tensile strain. , Gauges 53 and 54 detect the compressive strain due to the Poisson's ratio. Then, by connecting these gauges 51 to 54 to the bridge shown in FIG. 8, a high output corresponding to the amount of strain can be obtained without being affected by temperature fluctuation or bending strain. Each of the gauges 51 to 54 is protected by a silicon-based and epoxy-based coating material having a two-layer structure.

The strain gauge 5 is connected to a control device 6 as shown in FIG. 9, and the control device 6 displays a strain amount on a display 61 based on an output signal of the strain gauge 5 provided on each tie bar. The output signal is compared with a reference value by an internal comparator, and an excessive amount, an appropriate amount, and an excessive amount of distortion are displayed by the LED 62. If it is too small, the tie bar may be cracked as described later. Therefore, the abnormal buzzer 63 is sounded and the automatic operation of the die casting machine is stopped. When the calibration input value is changed by the calibration input value setting unit 64, the display on the display 61 can be switched between the stress value and the load value.

FIG. 10 shows the positional relationship between the fixed platen 21, the movable platen 22, the link housing 23, the strain gauge 5 and the like, and the amount of distortion of each part of the tie bar during mold clamping. In a normal state in which no cracks are generated, uniform tensile strain is generated in the tie bars 41 and 42. This is due to a general portion where a strain gauge is attached to a specific portion P such as a screw portion or a step portion where stress is easily concentrated. C doesn't change. However, in the case of an abnormality where a crack has occurred in the specific portion P, the amount of distortion at the specific portion P increases, and the forces received by the tie bars 41 and 42 are absorbed here.
As a result, in the general portion C to which the strain gauge 5 is attached, the amount of strain is greatly reduced. Then, by determining the decrease in the amount of distortion by the comparator in the control device 6, the occurrence of a crack is known, and the abnormal buzzer 63 is notified.

By the way, the mold clamping force gradually increases due to the expansion accompanying the rise of the mold temperature during use. Therefore, FIG.
The die height is adjusted by the procedure shown in (1), and the mold clamping force (that is, the reaction force load acting on the tie bar) is reduced to an appropriate value. That is, when the mold clamping is performed and the mold clamping limit LS is turned on, the load over due to the excessive clamping force is caused by the strain gauge 5.
, The mold is opened until the mold opening limit LS is turned ON, and the die height is adjusted. This is performed by rotating the hydraulic motor 49 described above in an appropriate direction (rotating for only 0.02 seconds by the die height adjustment drive timer) to move the link housing 23 backward (in a direction in which the distance between the fixed platen and the fixed platen is increased). Then, mold clamping is performed again, and the appropriateness of the mold clamping force is confirmed. If the clamping force is still large, the above procedure is repeated.

If the amount of distortion on the display 61 is disproportionately large or small with a certain tie bar, the mold is opened, the equipment is stopped, and the power is turned off. The worm gears 44A, 4A of the tie bars 41, 42
Joint 7 for connecting between rotating shafts 46A and 46B of 4B
1, 72 and 73 are separated, and the rotation shaft corresponding to the tie bar in question is rotated by a spanner or the like. As a result, the worm wheel nuts 44A and 44B rotate to change the substantial lengths of the tie bars 41 and 42. After this adjustment, the rotation shafts 46A and 46B are connected again, and the mold is clamped to confirm that the distortion amounts on the display 61 corresponding to the tie bars 41 and 42 are substantially the same.

Thus, according to the present embodiment, by monitoring the output of the strain gauge attached to the tie bar, not only crack detection but also an increase in mold clamping force due to a rise in mold temperature can be prevented. At the same time, the unbalance of the loads between the tie bars can be eliminated. As a result, the generation of burrs is suppressed, and the life of the tie bar is extended.

[0022]

As described above, according to the crack occurrence detection device of the present invention, the occurrence of a crack is constantly monitored, and a relatively small crack before the device becomes inoperable can be reliably detected.

[Brief description of the drawings]

FIG. 1 is an overall side view of a die casting machine provided with a crack detection device.

FIG. 2 is a cross-sectional view of a rotation drive mechanism of a worm wheel nut provided at an end of a tie bar.

FIG. 3 is a sectional view taken along line III-III in FIG. 2;

FIG. 4 is an overall schematic side view of the die casting machine.

FIG. 5 is an explanatory view of a toggle mechanism.

FIG. 6 is a graph showing characteristics of a toggle mechanism.

FIG. 7 is a perspective view of a strain gauge attached to a tie bar.

FIG. 8 is a connection diagram of a strain gauge.

FIG. 9 is a front view of a display panel of the crack detection device.

FIG. 10 is an explanatory diagram of distortion generated in a tie bar of the die casting machine.

FIG. 11 is a diagram showing a procedure of die height adjustment.

[Explanation of symbols]

 41, 42 Tie bar (shaft) 5 Strain gauge 6 Control device (crack occurrence determination means)

Claims (1)

(57) [Claims] 1. A strain gauge for outputting a signal corresponding to a strain amount is mounted on a shaft surface of a general portion of a shaft on which a tightening reaction force acts, where a crack is less likely to occur.
A crack occurrence detection device for a tightening mechanism, comprising: means for receiving an output signal of the strain gauge and determining the occurrence of a crack when the output signal becomes smaller than a predetermined value.