JPS6115122B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for automatically controlling the weight of powder charged into a cavity in the process of compression molding powder to obtain a green compact of a predetermined shape.

In order to manufacture powder metallurgy products, the powder is compressed and molded to produce a green compact before sintering, but the molding of powder using the widely known automatic molding press is the same as pressing. Powder is filled into a cavity formed by a die and a lower punch using a shoe box or the like that operates in conjunction with each other, and the filled powder is compressed by an upper punch attached to a ram to the desired pressure. Powder (molded body)
This is what you get. In this case, in order to mold a large amount of green compacts of the same shape with uniform green density and dimensions, especially the dimensions in the compression direction, it is necessary to keep the weight of the powder filled into the cavity and the pressing pressure constant at all times. be.

However, although the pressure for compressing the powder can be kept relatively stable, the weight of the powder packed into the cavity may vary depending on the bulk of the powder, segregation in particle size or composition, or switching of the powder mixing lot. It is easy to change during molding work due to etc. Therefore, even if the powder filling volume (powder bulk) in the cavity is held constant, the pressurizing pressure is kept constant, so if the powder bulk is large, the powder filling weight becomes lighter. The dimension in the compression direction, that is, the height of the green compact is reduced, and conversely, when the volume of the powder is small, the packed weight of the powder becomes heavy and the height of the green compact becomes high. If the amount of variation in the bulk of the powder is large as described above, the height dimension of the compact will exceed the desired dimension (standard value), which is undesirable as a large number of defective products will be produced.

For this reason, in the past, an operator would occasionally check the weight of the green compact produced, and manually rotate the filling amount adjusting section of the press as necessary, for example, by changing the relative height between the die and the lower punch. volume of the cavity,
In particular, a method has been used to adjust the depth, thereby adjusting the powder filling weight (ie, green powder weight) to fall within a predetermined tolerance range. In such a method, if the interval between checking the green compact weight is made as short as possible, or if all the green compacts are checked, the variation in the weight of the green compacts (i.e., the height in the compression direction) will be reduced. Although there is no chance of defective products being mixed in, the workability of manufacturing green compacts is significantly inferior, and at least one worker is required per press for checking, which reduces the human element. Manufacturing efficiency, including production efficiency, will be significantly reduced.

The present invention has been made in view of the above circumstances, and the present invention electrically detects fluctuations in the filling weight of powder as the amount of deviation of the upper punch from the reference position immediately after the upper punch pressurizes and compresses the powder. It is an object of the present invention to provide a method for automatically controlling the powder filling weight by changing the cavity volume based on a signal.

Embodiments of the present invention will be described below with reference to the drawings.

First, an apparatus for carrying out the method of the present invention will be described. In the figure, reference numeral 1 denotes a table of the press device, which is fixed to a predetermined location on a frame F, and a lower punch 2 is erected approximately at the center thereof. A lower plunger 3 is provided below the table 1 along the vertical direction, and a screw is carved in approximately the lower half of the lower plunger 3, and an edge extension nut 4 and a filling adjuster nut are inserted therein. 5 are screwed together at a predetermined distance from each other, and a lever 6 is disposed between each nut 4 and 5 and is moved up and down intermittently by a drive mechanism and an air cylinder (not shown). On the other hand, the lower plunger bracket 3B is fitted with a worm wheel 8 that is screwed into the filling adjustment nut 7. A worm 9 that meshes with the worm wheel 8 is rotated by a Guinard motor 10 to adjust the filling adjustment nut 5. The upper limit position, that is, the upper limit position of the lower plunger 3 can be changed. A support stand 11 is fixed horizontally to the upper end of the lower plunger 3, and pillars 12, 12 are erected at both ends of the upper surface of the support stand, passing through the table 1. is bolster 1
3 is fixed. A die 14 having a hollow portion having the same cross-sectional shape as the lower punch 2 is disposed approximately at the center of the bolster 13, that is, at a location that coincides with the center axis of the lower punch 2. 2 is inserted, and a cavity 15 is formed by the upper end surface of the lower punch 2 and the inner wall surface of the hollow part of the die 14. A hollow frame-shaped feeder 16 is provided on the upper surface of the bolster 13 and is reciprocated between its peripheral portion and the upper end opening of the cavity 15 by the drive mechanism of the press device. Powder is supplied to the periphery of the upper surface of the bolster 13, and is moved to the upper opening of the cavity 15, where the supplied powder falls into the cavity 15 and is filled therein.

An upper plunger 17 whose center axis coincides with the lower plunger 3 is disposed above the bolster 13, and a screw is carved in the upper outer periphery of the upper plunger 17, and a screw is carved in the lower part of the upper plunger 17. A hollow portion opening at the lower end surface is formed. An upper adjustment nut 18 and an upper pressure nut 19 are screwed onto the threaded portion of the upper plunger 17 with a predetermined distance between them, and between these nuts 18 and 19 the press device is driven. A lever 20 is provided which is moved up and down intermittently by a mechanism. Further, a holder 21 that is prevented from coming off by a flange is installed inside the hollow part, and this holder 21 is pressed downward by a compression spring 22 disposed at its rear end so that its tip end is inserted into the hollow part. An upper punch 23 and a horizontally extending dock plate 24 are attached thereto, protruding from the open end of the section. This upper punch 23 has the same cross-sectional shape as the lower punch 2, and its center axis coincides with the center axis of the lower punch 2, so that the upper plunger 17 is controlled by the lowering movement of the lever 20. The upper punch 23 is configured to press and compress the powder filled in the cavity 15 by moving downward while being guided by the bracket 25.

Furthermore, a limit switch 26 is attached to the outer wall surface of the tip of the upper plunger 17, which is operated by the dock plate 24 to detect the time of measurement. A detector 2 is operated to detect the position of the upper punch 23 during pressure compression, that is, the height of the green compact in the cavity 15.
7 is installed. These limit switch 26 and detector 27 are connected to the motor 1.
Control device 2 that controls the rotation direction and rotation amount of 0
8 is connected. Reference numeral 29 in the figure is a cam that rotates in conjunction with the drive mechanism of the press device, and a limit switch 30 connected to the control device 28 is attached to this cam 29. The motor 10 is configured to be driven by an output signal from the control device 28 as the motor 10 is operated.

FIG. 2 shows the motor 10 depending on the height of the powder compact.
This figure shows the principle of a circuit that controls the motor to rotate forward, reverse, or stop. That is, the detector 27 has two contacts, a first contact 27a and a second contact 27b, and the stylus 2
When 7c is located on the upper side, that is, when the height of the powder compact in the cavity 15 is higher than the reference height, the first contact 27a side is closed, and when it is located on the lower side, that is, the height of the powder compact When the height of the powder compact is lower than the reference height, the second contact 27b is closed, and when the height of the powder compact matches the reference height, both contacts 27a and 27b are opened. . In addition, each contact 27a, 27b
are movable as appropriate, and by changing their mutual spacing, the allowable height of the powder compact can be changed. The first contact 27a is connected to a first coil 31 provided in the control device 28, and the second contact 27b is connected to a second coil 32, and each of these coils 3
1 and 32, the b contact 26b of the limit switch 26 is inserted in series. Therefore, when the first coil 31 is energized with the b contact 26b of the limit switch 26 closed, the movable piece 31b, which is normally biased to contact one contact 31a, contacts the other contact 31c. When the second coil 32 is switched and the second coil 32 is excited, the movable piece 32b, which is normally biased to contact one contact 32a, moves to the other contact 32c.
Furthermore, the movable pieces 31b and 32b are electrically connected. Therefore, the height of the powder compact is high and the detector 2
When the first contact 27a side of the detector 27 is closed, the contacts 31c and 32a are connected, and when the height of the compact is low and the second contact 27b side of the detector 27 is closed, the contacts 31a and 32a are connected. 32c is connected, and furthermore, when the powder compact substantially matches the reference height and each contact 27a, 27b of the detector 27 is open,
The contacts 31a and 32a are configured to be connected. On the other hand, the limit switch 30
The a contact 30a and the contacts 31a and 32c are connected in series, and these and the first relay CR1
and b contact CR2b of second relay CR2, which will be described later.
are connected in series. In addition, the first relay
The a contact CR1a of CR1 is the contact 31a, 32c
The first relay CR1 is connected in parallel with the first relay CR1 so as to maintain itself. In addition, the contacts 31a,
32a is connected in parallel with the contacts 31a and 32c, that is, in series with the a contact 30a of the limit switch 30, and is connected to these and the second relay CR.
2 and the b contact CR1b of the first relay CR1 are connected in series. In addition, the second relay CR
The second a-contact CR2a is connected in parallel with the contacts 31a and 32a so as to be self-supporting. Furthermore, 33a in FIG. 2 is an a contact point of a limit switch (not shown) operated by another cam (not shown) that operates in conjunction with the drive mechanism of the press device, and this a contact point 33a and What is Reverse Relay MR and Forward Relay MF? Fuse 34
The reversing relay MR is connected in series with the normal relay MF, the other b contact CR1b' of the first relay CR1, and the other b contact CR2b' of the second relay CR2. Connected in series, forward relay MF is connected to reverse relay MR.
B contact MRb and other A contact CR of the first relay CR1
1a' are connected in series.

Next, the method of the present invention will be explained based on FIGS. 3 and 4.

Figure 3 A, B, and C show the step-by-step process of pressurizing and compressing powder and extruding the formed green compact, and Figure 4 is a cam diagram corresponding to the process. , 35 in FIG. 4 indicates the position of the upper end surface of the lower punch 3, 3b indicates the vertical movement of the upper plunger 17 and the upper punch 23, 37 indicates the vertical movement of the die 14, and 38 indicates the position of the upper end surface of the feeder 16. In addition, the diagonal line 39 indicates the position where the height of the green compact is measured, and 26b, 30
a, 33a are the b contact 26b and a contact 30
The opening and closing positions of a and 33a are shown, and the shaded portion indicates the closed state (ON state). Therefore, in the state shown in FIG. 3A, the lower plunger 3 is at the upper limit position, that is, the die 14 is at the upper limit position, the cavity 15 is at a predetermined depth, and the feeder 16 is placed here. This is a state in which the powder is dropped and filled, and the upper plunger 17, that is, the upper punch 23, begins to descend, and this is a state in the range of 0° to about 70° in FIG. In this state, B contact 2
6b, A contacts 30a, 33a are open, so the forward rotation relay MF and reverse rotation relay in Fig. 2
MR is not excited and the motor 10 does not rotate. Thereafter, when the upper punch 23 descends together with the upper plunger 17 and the tip end surface of the upper punch 23 comes into contact with the powder in the cavity 15 (curve 37 and curve 36 in FIG. 4 intersect), the powder is processed. Pressure compression is started. In this case, since the force of the compression spring 22 is initially stronger than the resistance force of the powder, the upper plunger 17 and the upper punch 23
Although the relative position with respect to
Finally, the compressive force of the upper plunger 17 is applied directly to the powder via the upper punch 23, and the maximum downward pressure is reached at the 180° point in Fig. 4 (No. 3).
Figure b). At this point, the powder is compacted and becomes a compact, but at the maximum pressure, there is a slight distortion in the mechanical system, which is not suitable for measuring the height of the compact, so each contact 26b, 30a is still ,33
a is open and no measurements are taken. Note that after the upper punch 23 starts compressing the powder,
After a slight delay, the die 14 starts to move down together with the lower plunger 3 using the lever 6.

After passing the maximum pressure point, Atsupapa plunger 1
7 begins to rise, but since no force is applied to the upper punch 23 to actively push it up, the upper punch 23 remains in that position while the compression spring 22 extends to its initial state (as shown in Figure 4). (state shown by the chain line), the green compact is therefore held between the upper punch 23 and the lower punch 2. On the other hand, dice 1
4, after a while after the upper punch 23 begins to rise, it begins to rapidly descend (from the 270° point in Figure 4), and eventually descends until its upper surface and the upper surface of the lower punch 2 coincide. do. Then, when the upper punch 23 and the lower punch 2 are holding the powder compact, and the upper surface of the die 14 is about to match the upper surface of the lower punch 2 (270° point in FIG. 4), the limit switch 30 is turned on. is operated by the cam 29 and its a contact 30
a closes, and at the same time or slightly later (280° point in Figure 4), the upper plunger 17
The limit switch 26 attached to is operated to close its b contact 26b, and the height of the powder compact is measured here. (Figure 3 C). At this point, as shown in FIG. 4, the upper punch 23 is about to separate from the powder compact, so there is almost no distortion in the mechanical system and accurate measurements can be made. On the other hand, when the B contact 26b of the limit switch 26 is closed and the other A contact 33a is closed, the motor 10 is started or stopped depending on the measurement result, and thus the volume of the cavity 15, that is, the filling amount is Make adjustments.

This series of operations for measurement and adjustment of the filling amount is explained using the circuit shown in FIG. When the detector 2 is within the range of , the detector 2 pressed by the dog plate 24
The stylus 27c of No. 7 is located between its first contact 27a and second contact 27b, and each contact 27a, 27b is open, and the first and second coils 31, 32 are not excited. Therefore, the connection state here is such that the contact 31a and the contact 32c are connected, and as a result, the limit switch 30 is operated and its a contact 30a is closed, and the first relay CR1 is not energized. Since the b contact CR1b is closed, the second relay CR2 is energized and self-holds. However, the second relay CR2
is energized and self-holding, the second relay
The other b contact CR2b' of CR2 is open, and the other a contact CR1a' of the first relay CR1 is open, so even if the a contact 33a is closed, the forward relay MF,
None of the reversing relays MR is energized and motor 1
0 remains stopped.

Further, when the amount of powder filled into the cavity 15 is large and the height of the green compact is higher than the reference height, the stylus 27c of the detector 27 comes into contact with the first contact 27a, and the first coil 31 The movable piece 3 is excited
1b switches from contact 31a to contact 31c,
As a result, even if the limit switch 30 is operated and its a contact 30a is closed, the first and second relays
Neither CR1 nor CR2 is excited. When the a contact 33a closes, the forward relay MF is not energized and its b contact MFb closes, and the first
Since the second relays CR1 and CR2 are not energized and the other b contacts CR1b' and CR2b' are closed, the reversing relay MR is energized, and as a result, a current flows through the motor 10 to reverse it. The worm 9 and the worm wheel 8 rotate in the opposite direction, and the filling adjustment nut 7 is lowered somewhat. Then, the lower plunger 3 is lowered and the bolster 13, that is, the die 14, is lowered somewhat through the support stand 11 and the column 12, and as a result, the depth of the cavity 15, that is, the volume, is reduced, and the powder filled therein is reduced. weight is reduced.

Further, if the amount of powder packed into the cavity 15 is small and the height of the green compact is lower than the reference height, the stylus 27c of the detector 27 is pressed against the dog plate 24 and comes into contact with the second contact 27b. second
The coil 32 is excited and its movable piece 32b switches from the contact 32a to the contact 32c, and the movable piece 32b switches from the contact 32a to the contact 32c.
and the contact 32c are in a connected state. As a result, when the limit switch 30 is operated and its a contact 30a is closed, the second relay CR2 is not energized and its b contact CR2b is closed, so that the first relay CR1 is energized and self-holds. Therefore, since the first relay CR1 is energized and the other b contact CR1b' of the first relay CR1 is open, and the other a contact CR1a' is closed, the forward rotation relay MF is energized, and as a result, the motor 10 is A current flows through the worm to rotate it in the forward direction, causing the worm to rotate in the forward direction, thereby causing the worm 9 and the worm wheel 8 to rotate and the filling adjustment nut 7 to rise somewhat. Then, the lower plunger 3 rises and pushes up the bolster 13, that is, the die 14, somewhat through the support stand 11 and the column 12, and as a result, the depth of the cavity 15, that is, the volume increases, and the weight of the powder to be filled increases. increases.

The amount of change in the depth (volume) of the cavity 15 is determined by the amount of rotation of the motor 10, but this can be done by appropriately setting the shape of a cam (not shown) that closes the a contact 33a in FIG. Contact 3
3a should be closed for a predetermined period of time (in the range of 285° to 355° in FIG. 4).

The green compact formed and measured in this manner is transferred to the advancing feeder while the upper surface of the die 14 and the upper surface of the lower punch 2 are in agreement (between 275° and 285° in FIG. 4). 16 to move to a predetermined position. Thereafter, the die 14 is raised to form a cavity 15, and the powder is dropped and filled into the cavity 15 by the feeder 16, and the above-described operation is repeated.

As is clear from the above explanation, the weight of the powder filled into the cavity 15 varies slightly due to variations in its volume, but according to the above configuration and method, the weight of the powder filled into the cavity 15 is suppressed in the compression direction of the green compact. The height of the cavity is detected each time it is compressed, and if there is a change at the same time, the height of the cavity 1 is detected in accordance with the amount of change.
Since the depth in the compression direction of No. 5, that is, the volume, can be changed, green compacts of the same shape can be automatically and continuously obtained, and no defective products will be mixed in. In particular, the first contact 27a and the second contact 27 of the detector 27
If the distance from b is set to be sufficiently narrower than the allowable range of the height of the green compact, the accuracy will be further improved.

In the above embodiment, the die 14 was moved up and down to change the depth (that is, the volume) of the cavity 15, and the die 14 was lowered to relatively extrude the green compact, but in a fixed die press, Alternatively, the lower punch 2 may be attached to a lower plunger and the lower punch may be moved up and down to change the depth (ie, volume) of the cavity 15 and to extrude the compact from the cavity 15. Further, the mounting position of the limit switch 26 attached to the upper plunger 17 is not limited to this, but the limit switch 26 may be attached to the holder 21 or the upper punch 23 and operated by the dog attached to the upper plunger 17. It is also possible to construct a circuit as shown in FIG. 4 by using the b contact among the contacts. Further, the circuit shown in FIG. 4 is based on the principle, and it is possible to configure other circuits to operate each member in the same manner as in the above embodiment. Furthermore, if the height (weight) of the powder compact exceeds the permissible range for some reason, it is possible to detect this and issue an alarm or mark the powder compact. Contamination with non-defective products can be completely prevented.

As explained above, according to the present invention, the weight of the powder is detected as the height of the green compact each time the powder is pressurized and compacted to form a green compact, and at the same time, if there is a variation from the reference value, Since the filling weight of the powder is automatically adjusted by changing the depth of the cavity, it is possible to continuously and automatically obtain powder compacts of the same shape with height and weight within the allowable range. Therefore, there is no need for the operator to inspect the powder compact from time to time and change the depth or volume of the cavity, as in the past, and work efficiency is significantly improved. Furthermore, since the method according to the present invention is a so-called 100% inspection, there is no problem such as the accumulation of slight fluctuations in the packed weight of powder for some reason, resulting in defective products.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing a press device according to the present invention, FIG. 2 is a circuit diagram thereof, FIG. 3 is an explanatory diagram showing its operation, and FIG. 4 is a cam diagram thereof. 2...Lower punch, 7...Filling adjustment nut, 10
...Geared motor, 14...Dice, 15...
Cavity, 23...Upper punch, 24...Dog plate, 26...Limit switch, 27...
...Detector, 28...Control device, 30...Limit switch, 33a...A contact.

Claims (1)

[Claims] 1. A powder compression molding method in which a lower punch is fitted into a die of a predetermined shape, a cavity formed by the die and the lower punch is filled with powder, and this powder is compression molded using an upper punch at a substantially constant pressure. After the upper punch has compressed the powder, while the powder compact is being held between the lower punch and the upper punch, the position of the upper punch is electrically detected, and the position of the upper punch is detected from a predetermined reference position of the said position. The depth of the cavity is adjusted by electrically measuring the amount of deviation of the die and driving a motor using an electric signal corresponding to the measurement result to displace at least one of the die or the lower punch. Automatic control method for powder filling weight.