JPS5956965A - High-frequency casting device - Google Patents

Abstract

PURPOSE:To automate melting and casting strokes and to produce a casting having good quality with good efficiency in a device for casting a small-sized casting under a nonoxidative atmosphere by controlling the same in accordance with the storage of the current and time value for heating and heat insulating in casting conditions. CONSTITUTION:Heating current IH is impressed by a circuit 5 on an induction coil 7 to melt the metal M in a crucible 6. The current IH is controlled to a target value IHf as the output of a resistor 10 for detecting said current and the signal set in a circuit 11 are compared in a circuit 12 and a circuit 15 is operated by a circuit 13. The time tf when the metal M attains the m.p. thereof is measured visually and said time is stored as a set value tf, for the melting time with respect to casting conditions such as the kind, melting amt., atmosphere, etc. of the metal in the circuit 16M of a computer 16. The holding time tc after the thorough melting of the metal until casting is set in a circuit 17 and when said time is set, a photocoupler 14 is conducted, and the current IHC enough to maintain the metal M at around the m.p. during this time is detected by the manual operation of the circuit 11. The melting state of the metal M is visually observed and is stored as the set value IHC for heat insulation in a circuit 16M. The control is accomplished by the output of the computer 16 after the end of the actual measurement.

Description

DETAILED DESCRIPTION OF THE INVENTION This invention involves casting metal melted by high-frequency induction heating in a vacuum atmosphere or an inert gas atmosphere into a mold placed in the same atmosphere. This invention relates to a high-frequency casting device for manufacturing small-sized dental or industrial castings.

A gold alloy that has excellent properties as a conventional dental prosthetic material,
High-frequency casting equipment used for casting high-melting point alloys such as silver alloys, nickel-chromium alloys, or nickel-chromium-cobalt alloys is used to plant and bury a wax pattern in a high-temperature investment material, such as a phosphate-based investment material.・Using a mold made from the lost wax method, heat it to a specified temperature (
(depending on the type of alloy), set it in an airtight container of a casting machine, evacuate the inside to a temperature of 10 to 10 Torr in a short time, and pour the molten alloy. For example, an inert gas such as argon at a pressure of 5 kg/c PoG is applied to the pouring metal, and the pressure is applied due to the pressure difference between the gas pressure acting on the riser and the gas pressure inside the mold until the poured metal solidifies. With a continuous pressure casting method that lasts,
There are many devices. However, in order to pour the molten alloy mentioned above, the entire alloy must be completely melted, and in conventional equipment there is no reliable means to confirm the complete melting. This has the drawback of increasing the heating time (say), or flowing the heating current more than necessary, which often causes the temperature to boil.The temperature at which the paddle is kept melting is detected by a radiation thermometer, and the temperature There are devices to control the temperature inside the crucible, but the method of detecting the temperature inside the crucible through the sight glass is that the temperature inside the crucible can be detected immediately by gas or smoke,
The drawback is that it is difficult to measure temperature accurately.

This invention was made in view of the above-mentioned current situation, and each
t Type of metal to be Mated, amount of melting, air quality, etc.:
The actual measurement standard values of the heating current value and heating time value in 1- are stored and controlled by this, and the actual measurement standard heating current value and time value until the molten metal is cast are also stored. The present invention relates to a high-frequency casting apparatus characterized in that these are installed in the control system to control melting retention, and the optimum time corresponding to the melting conditions is determined by the (1q formation).・The aim is to provide a convenient device that can efficiently produce high-quality cast products by setting the electric current to the 1 system and automating the melting and casting processes.

The present invention will be explained in detail below with reference to the drawings.

FIG. 1 shows an embodiment of the high-frequency casting apparatus (1) according to the present invention.
) is a configuration block diagram of. For example, 60H2 power from the AC low frequency power supply (2) is passed through the transformer (3) and rectifier (
4) was converted to direct current via the via 1-2, and this was converted into a high frequency current (H) of several 1.0 kHz by a high frequency oscillation circuit (5) using a vacuum tube or transistor, which was provided around the crucible (6). The voltage is applied to the guide wire ring (7). For example, take out the anode current of the vacuum tube or the base current of the transistor (1 current) which is proportional to this heating current (H), convert it into DC through a high frequency transformer (8) and a rectifier (9), and halve it. A fixed resistor (10) is used to output the heating current (IH) as a feedback voltage signal (CJM). This is the means for detecting the heating high frequency current.

Next, this ('vH) signal and the high frequency current setting circuit (1
1) is compared with the setting signal (vs) by a comparison circuit o2). The above setting signal (vs) is, for example, the current program chart during fixed value control shown in Figure 2. The coil (
7) A certain value of the heating current (IH) applied to the
0A roll 1, 1.1! It is an l value signal. Now, for example, when trying to make cobalt-chromium thread in a predetermined length ν), if the above (work, -1) is predetermined at 30A and the setting circuit (11) outputs the αday) signal corresponding to 3OA. With this as the target value, the above detection signal (VH) is (VH=
A comparator circuit (12) generates a fu control signal 1E flow OC) that becomes
4), installed in the circuit of the AC power supply (2), operates the thyrisk type phase control circuit G15), and adjusts the firing phase angle of the AC waveform to control the transformer primary voltage (E
p), and the heating voltage (1N) is constant-value controlled to the above-mentioned target value. This 74-back control system is controlled by disturbances such as voltage fluctuations of the AC power supply (2) and high frequency oscillation circuit (5).
This is a feedback control system that is not affected by noise etc. and provides a positive control value r with respect to the target value set by the current setting circuit (11).

Return to Figure 2 and figure ■ Temperature of the metal in the crucible (T1)
It is a time cheat of melting point temperature (TM
f) Indicates that KM has been carried out. Visually confirm that the metal has reached the melting point (TMf) and melted from the time (to) when the set current (JHf) is applied, and the (t 1
- Measure the required melting time (tf) of (to) and use this as a fixed melting time setting value (1;) for the type of metal and casting conditions such as melting amount and air.
This (tf) is input to the memory circuit (16N) of the microcomputer (16) and stored.Then, the above-mentioned molten metal (3) is stored in the above-mentioned (Tmf) as shown in FIG.
) is slightly over E7 and fits in (Tmf)! The holding time (t2) is maintained until the entire amount of metal is completely melted and poured into the mold (t2).
c) is determined in advance to be, for example, 18eC, and this is
Time setting and 0N-OFF time setting device (17) in figure A1
). With this time setting, the photocoupler (14
1000 current flows through the light emitting diode (14L) of ), making the phototransistor (14T) conductive. This (t
During the set time of c), the temperature of the metal (c) is as shown in Figure 2 ■
It detects a current (Tsc) sufficient to maintain (also called hold-off) near the melting point. This detection is carried out by manually operating the current setting circuit (11), so the current should be reduced to about 30 degrees (I)If). Visually confirm that the temperature is maintained, and then set the specific heat retention current setting value (I) under the above conditions.
)l'c), and input and store it in the memory circuit (16 seconds).After completing the above measurements, for metals under the same casting conditions, σ, f)・( Engineering 4
The two-stage l:1m current value of c) is output from the microcomputer (16) and set in the heating Lj7 flow setting circuit (11), and the target time of the same < (t6・(t c)) is set in the time setting circuit. Just set it in advance to (17), and then it will automatically keep the constant current (I) up to the point (tl).
Hf) and melted by heating, and at the time (tl), the time setting circuit (1
7) After receiving the signal from the microcomputer (16)
automatically switches the current setting value of the current setting circuit (11) to (nc), and by this target value of (Ha), (t
c) When the time has elapsed (t2), the photocoupler (l is signal 1#, the flow (IC) is turned OFF L, and the molten metal is simultaneously cast into the mold. The above is a case where the current control means is constant value control) However, current control is not limited to the above fixed value control, but also
Various methods may be used, as illustrated in FIGS. Figure 3 ■ shows that a point (ta) (t) is set between the melting time set value (t f), and at that point, the target current value is gradually decreased to (■ Hf') (cm sf). By changing the current in this way, the temperature increase gradient before reaching the melting temperature of the metal (T M , the temperature exceeding the melting point between (tl) and (c2) (the four forces are reduced compared to the above constant value control, and the casting becomes stable. Figure 4 ■ is ('l:0) -
The constant current control of the melting time at (tl) is the same as in Fig. 2, but the melting holding current set value after the time (tl) is intermittent at a predetermined period, for example, the OFF time is (tA). , the ON time is (tf5), and (t8/lA
) is set as ≠, the effective current is approximately 1/3 of (IHf)
This is similar to (1-IC) in FIG. 2.

This intermittent rate is determined by the ON-OFF time setting circuit (1) shown in Figure 1.
7). Figure ■ shows that the temperature in the molten state becomes almost stable with small intervals depending on the control method. Figure 5 ■ shows the melting time (tl) (ta
) (tb), and when (ta) is reached, the current setting value (t(f) is set to (tHA) at (tX), and (
t6) At times, the current is a rectangular wave of (I Hf), and (t
From point b), change the current on the lower side to the waveform of (to s), and from the melting point (tl), change the current on the lower side to
'). The program control that reduces the heating current step by step until melting is similar to the method shown in Figure 3 above, but the temperature of the metal (T) is
As shown in Figure 2, the temperature exceeding the melting point (TMf) is extremely low, and this method has excellent casting performance.

Returning to FIG. 1, the following security function is added to the time setting circuit (17). That is, if a failure occurs somewhere in the current control system and the metal does not melt even after a predetermined period of time, the photocoupler (14) is urgently shut off.

The above is the configuration and operation of the high-frequency casting apparatus according to the embodiment of the present invention, but the high-frequency current feedback control (41) is not limited to the one shown in the drawings, and the control system explained in FIGS. The control method is not limited to the above, and control methods that include proportional, integral, and differential operations can also be applied, and many other methods can be considered. Additionally, a temperature detection system is added to the above time and current control system, and
It is also possible to use an apparatus that collects the data shown in Figure 2 and observes the control performance of the control system.

As described above, this invention solves the problems of the conventional high-frequency HtJi manufacturing equipment, especially the melting time keeping function [2. By maintaining melting using a feedback control system that sets the optimum actually measured holding current value to maintain a state suitable for hot water, good casting conditions are always met without being affected by heavy power supply pressure or other disturbances, resulting in good quality. This provides a convenient device that can efficiently produce high-quality cast products.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing the configuration of the control system of the high-frequency casting apparatus according to the embodiment of the present invention, and Fig. 2 b is a current constant 1 near <
Temperature time chart of molten metal according to the control Quimchi l. Figure 4 (■) shows the time button for controlling the melting heat retention current intermittently, Figure (G) is the melting temperature time chart according to Figure ■, and Figure 5 (78) shows the melting current and the melting heat retention current as a program graph; Ill
Figure 1 is a temperature chart of molten metal according to Figure 2. (5)...High-rise e-source circuit (6)...RutsutY. (7)... High frequency 1: conductor 1; 1 (ring (10)
... Heating current detection resistor (11) ... Heating current setting circuit (12) ... Comparison circuit between detected value and set value (13)
... Operation circuit (14) of AC phase control circuit (15)
・・・ Time system side j operation end (16) 11・Microcombiner (16M)・・
Memory circuit (1”) of the above (16)... Time setting and current ON-OFF setting circuit σ1 ()... Heating high frequency current (work)... Heating current setting value (actual measurement standard value) (work H
CXII (d)...Heat insulation Ichihara setting value (actually measured standard value) (
tl)... Melting 1 good point (t f)... Heating time setting value (actual measurement standard f1σ)
(t2)... Casting time (tc)... Melting retention time setting value (actual measurement standard value) (
T-Re...Melting temperature Figure 1 Procedural amendment (voluntary)] Neutral indication]) Self-phase 57 I I' Patent Nii I 1 No. 1691'
i'6 bow 2, title of the invention High frequency casting device, (, r mountain ``ni・1・person who does it) related to patent applicant 41 agent agent 5 [Spontaneous] 3rd line, 1st character ``Correct pressure-1 to Flow'', 17th line 1-fee pack'' ヲ ``Feedback-]
to be revised. 8-2 The 4th character of the 8th page of the specification 1--” is 1
+” and also the 1st (1st line 1(t2)J
Correct it to r(t+)J. that's all

Claims (1)

[Claims] The metal placed in the crucible in a vacuum atmosphere or an atmosphere of inert gas is melted by induction heating using a high-frequency current, and this is then cast into a mold in the atmosphere. In the apparatus, the type of metal to be melted
Heating current value under casting conditions such as melting amount and air,
The actually measured standard value of the heating time value is stored and the control is performed using this value, and the actually measured standard heating current value and its time value until the molten metal is cast are also stored, and these are used for the control. A high-frequency casting device characterized in that it is set to a wholesale system to control melting and retention.