JPH0791568B2 - Sizing press for powder molding - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a sizing press for sizing a powder molded product that is pressure molded by a powder molding press and sintered.

(Prior Art) Since a molded product obtained by sintering after powder molding has a variation in size, pressure is applied again by a sizing press for sizing to improve dimensional accuracy. That is, various materials are mixed in the raw material powder, and for example, in iron-based powder, iron powder (variation in particle size),
Carbon, zinc stearate, etc. with different specific gravities are used, and these mixed materials are filled into the die attached to the powder molding press by the feeder and measured in the scraping state with the feeder. Variations occur, and moreover, there is a burning error due to sintering. In this case, there is little variation in the radial direction that is limited by the inner diameter of the die, but there is a large variation in the height direction that is compressed by the upper and lower movable punches, etc. Variation of about ± 0.2 mm occurs. Therefore, in order to improve the dimensional accuracy, the sizing is performed by pressing again with the sizing press.

The sizing press for this purpose is generally composed of an upper punch attached to the upper punch plate and pressed by the upper hydraulic cylinder, a lower punch attached to the lower punch plate and supported by the lower hydraulic cylinder, and a baking punch. The die is attached to a die plate for accommodating the bonded powder molded product and cooperating with the upper punch and the lower punch to size the powder molded product.

In the conventional sizing press, a stopper is provided between the upper punch plate and the lower punch plate, and when the dimension of the powder molded product in the height direction reaches a specified dimension, the stopper receives the load applied to the powder molded product. Was doing.

(Problems to be Solved by the Invention) However, when a large load is applied only to the stopper, the stopper and the mold are distorted, and the effect is not so high as to obtain a desired accuracy. Then, this invention aims at provision of the novel sizing press which can solve these problems.

(Means for Solving Problems) In the sizing press, the present invention is provided between the upper punch plate and the lower punch plate of the press body, and the height of the powder molded product is measured by measuring the distance. Sizing pressure that detects that the detection signal has been reached, and a solenoid switching valve that has a hydraulic circuit that controls the upper hydraulic cylinder are installed in parallel. A sizing press for powder molding, characterized in that the sizing press for powder molding is provided with a relief valve that supplies a pressure to the hydraulic circuit and that acts on the hydraulic circuit to stop the pressure increase upon receiving the detection signal.

(Example) Below, the Example of this invention is described based on drawing. As shown in FIGS. 1 and 2, the sizing press is composed of a press body and a control circuit. First, the press body comprises an upper hydraulic cylinder 1 and an upper punch plate 3 connected to the tip of a piston rod 2 of the cylinder 1.
And a cylindrical upper punch 4 fixed to the upper punch plate 3 and movable up and down by expansion and contraction of the upper hydraulic cylinder 1 on the upper side.

On the lower side of the press body, a die plate 7 fixed to a base 5 and fitted with a die 6 is connected to the die plate 7 via a guide rod 8 and inserted into the die 6. Fixed plate 10 with core rod 9 attached
A lower hydraulic cylinder 11, a yoke plate 13 connected to the tip of a piston rod 12 of the cylinder 11, a lower punch plate 15 connected to the yoke plate 13 via a connecting rod 14, and a lower punch plate 15 A cylindrical lower punch 16 that is fixedly attached to the lower hydraulic cylinder 11 and is vertically movable by expansion and contraction of the lower hydraulic cylinder 11.

Furthermore, one end is attached to the upper punch plate 3 and is vertically installed so as to pass through the die plate 7, and the other end contacts the lower punch plate 15 at the time of pressure forming to generate a detection signal. 17 are provided.

As the length measuring sensor 17, for example, Magnescale (trade name of Sony Magnescale Co., Ltd.) or the like is used, and its configuration is as shown in FIG. That is, the probe 17
A spindle 17b having a is projected from the main body 17c, the spindle 17b is slidably supported in the main body by a bearing 17d, and is supported by a spring 17e, and is connected to the base end of the spindle 17b. Scale 17f is the main body 17
It is configured to pass through the inside of the detection head 17g built into c.

The length measuring sensor 17 is shortened within the range of the measurement stroke 1 when the probe 17a is pressed, and generates a detection signal when the scale 17f is inserted through the detection head 17g to perform the length measurement. It can be taken out via 17h.
A dedicated comparator / display unit (not shown) is prepared for the length measurement sensor 17, and the unit digitally displays the deviation from the measured value with respect to a preset upper limit value or lower limit value, and It is possible to determine whether the deviation is outside the upper limit value or outside the upper and lower limit values, and perform lamp display and signal output.

A dock (operation lever) 20 is attached to the upper punch plate 3 and the die plate 7 via mounting rods 18 and 19, respectively.
And the switch 21 are attached, and the contact point of the switch 21 conducts when the upper punch 4 reaches the upper limit, detects this, and takes out the powder molded product 22 knocked out on the die plate 7. Therefore, a control signal for activating a robot or other feeding device (not shown) is generated.

Next, the hydraulic control circuit controls the solenoid valve 23 for controlling the upper hydraulic cylinder 1 and the lower hydraulic cylinder 11
An electromagnetic switching valve 24 for controlling the hydraulic pressure and an electric relief valve 25 controlled by a detection signal from the length measuring sensor 17 are provided in parallel with a hydraulic source 26. The electromagnetic switching valve 23 and the electromagnetic switching valve 24 are each composed of a 4-port 2-position switching valve operated by a solenoid. At one position, the upper punch 3 and the lower punch 16 are moved upward as shown in FIG. , To supply the hydraulic pressure to the upper and lower hydraulic cylinders 1 and 11 to knock out the molded product 22, and at the other position to apply a pressure for sizing to the powder molded product 22 as shown in FIG. Is to be switched.

In addition, the relief valve 25 is a digital valve like this embodiment,
Otherwise, a proportional solenoid valve or an electro-hydraulic servo valve is used. The relief valve 25 is set to a desired set pressure by a variable adjustment by an electric motor, and until the set pressure is reached, the hydraulic cylinders 1, 1 are set through the electromagnetic switching valves 23, 24.
The pump discharge oil is supplied to the hydraulic pressure source 1 from 1 to continuously increase the pressure, and the pressure increase is stopped by the detection signal of the length measuring sensor 17.

Further, the length measuring sensor 17 is such that the height dimension of the sintered powder molded product 22 that is sized by measuring the distance between the upper punch plate 3 and the lower punch plate 15 has reached a prescribed height. Is detected, and the relief valve 25 is controlled by generating a detection signal so that the pressing force beyond that is not applied to the upper punch 4 and the lower punch 16. That is, the sintered powder molded product 22 has a long height dimension and a short height dimension, and the pressing force required when sizing these to a fixed prescribed height dimension is different. Until the sizing is completed (until the length measuring sensor 17 generates a detection signal), the hydraulic circuit is equipped with the relief valve so that the minimum required pressure can be supplied to each powder molded product.
It is controlled by 25 and is controlled by the relief valve 25 so as not to become overpressure more (when the detection signal is generated) when the specified height dimension is reached.

In this regard, in the present embodiment, the set pressure of the relief valve 25 is about the pressurizing force required to size the product having the smallest height dimension among the sintered powder molded products 22 to the specified height dimension. Initially set to, if the height dimension of the item to be sizing is large, until the detection signal is generated, sequentially increasing the set pressure while varying the initial set value of the relief valve 25 to the motor, As shown in FIG. 2, when the detection signal is generated by sizing to the specified height,
This detection signal stops the motor to stop the rise of the set pressure of the relief valve 25 and restores the initial set pressure.

Note that the relief valve 25 can be set as follows in addition to the above embodiment. For example, the initial setting value is set to a pressing force necessary for sizing the largest height dimension among the sintered powder molded products 22, and the detection signal from the length measurement sensor 17 is sized to the specified dimension. When the above occurs, the set pressure of the relief valve 25 may be reduced at once by the detection signal (for example, up to about the pressing force required for sizing the powder molded product of the minimum size).

Next, when the desired sizing is completed as described above, simultaneously or thereafter, as shown in FIG. 1, the electromagnetic switching valve 23 is switched to raise the upper punch 4 until the dock 20 and the switch 21 come into contact with each other. Also, the sized powder molded product 22 is knocked out by switching and raising the electromagnetic switching valve 24. The knocked-out powder molded product 22 is moved to a predetermined discharge path by the robot or other feeding device which is operated by a control signal generated by the contact between the dock 20 and the switch 21, and is newly sized instead. The sintered powder molded product is set in a predetermined position.

In addition, the setting of the length measuring sensor 17 is provided at two points, that is, the time (second set value) and the time (second set value) before reaching the specified dimension, and the pressure is rapidly increased to the first set value, If the rise of the pressure is delayed between the first set value and the second set value, better sizing can be performed. Also,
As the length measuring sensor, a rack may be provided on one of the upper punch plate and the lower punch plate, and a pinion for operating a rotary encoder may be provided on the other.

(Effect of the invention) As is apparent from the above-described embodiments, in the sizing press according to the present invention, it is detected by the length measuring sensor that the powder molded product is sized so as to have the specified dimension height. Since the relief valve is controlled so that no more pressure is applied to each part of the press machine body, it is possible to manufacture powder molded products with high dimensional accuracy and to prevent damage to the press machine body. It is effective.

[Brief description of drawings]

FIGS. 1 and 2 show a sizing press according to an embodiment of the present invention. FIG. 1 is an operation state explanatory diagram when a powder molded article is knocked out, and FIG. 2 is an operation state explanatory when a powder molded article is pressurized. FIG. 3 and FIG. 3 are vertical sectional views of a length measuring sensor used in the sizing press. [Explanation of symbols] 1 ... Upper hydraulic cylinder 2, 12 ... Piston rod 3 ... Upper punch plate, 4 ... Upper punch 5 ... Base, 6 ... Die 7 ... Die plate, 8 ... Guide rod 9 ... Core rod, 10 ... Fixed Plate 11 ... Lower hydraulic cylinder, 13 ... Yoke plate 14 ... Connecting rod, 15 ... Lower punch plate 16 ... Lower punch, 17 ... Length measuring sensor 18, 19 ... Mounting rod, 20 ... Dock 21 ... Switch, 22 ... Powder molded product 23, 24 ... Solenoid switching valve, 25 ... Relief valve 26 ... Hydraulic source

Claims (1)

[Claims] 1. An upper punch attached to an upper punch plate and moved by an upper hydraulic cylinder, a lower punch attached to a lower punch plate and moved by a lower hydraulic cylinder, and a sintered powder molded product. A press body having at least a die attached to a die plate for accommodating and accommodating the upper punch and the lower punch to size the sintered powder molded article; A length-measuring sensor provided between the punch plate and the lower punch plate, which detects that the height of the powder molded product has reached a specified dimension by measuring the distance, and generates a detection signal, and the upper hydraulic cylinder. Is provided in parallel with the solenoid directional control valve having a hydraulic circuit for controlling the above, and the sizing pressure that sequentially increases until the detection symbol is generated is supplied to the hydraulic circuit. For powder molding sizing press, characterized in that a set pressure-varying relief valve that acts on the hydraulic circuit so as to stop the pressure rise by receiving a detection signal.