JP6634061B2 - Mold heating device for core manufacturing - Google Patents

Description

  The present invention relates to a heating device for heating a mold for manufacturing a core by a gas burner, and to a mold heating device for controlling the mold heating temperature.

As shown in FIG. 3, a cavity 18 having an uneven wall surface 18 a corresponding to the shape of a core to be manufactured is formed inside the mold 1, and a mold sand S for manufacturing a core is formed in the cavity 18. Will be filled. The mold sand S is generally a casting sand covered with a phenol resin (resin coated sand (RCS)). When the mold sand S is heated in the cavity 18 of the mold 1, the phenol resin is thermally melted. The foundry sands are more strongly adhered to each other and hardened along the uneven surface 18a of the cavity 18, so that a core having a desired shape is manufactured. The phenol resin requires a temperature of 150 ° C. for curing, and thermal decomposition is accelerated from 350 ° C. Therefore, the mold temperature is set to 250 to 350 ° C. in order to harden the mold sand S into the cavity 18 of the mold 1 and to prevent the strength from being degraded by thermal decomposition.
For example, when manufacturing the core in the mold 1, the mold 1 is heated by the gas burner 2 if the mold temperature is optimally 270 ° C. in consideration of the shape and thickness of the core or the atmospheric temperature. In order to match the supply pressure of the gas to be supplied, the blowing time is set at a gas supply pressure of, for example, 1 to 3 KPa at a blowing time of every 2 to 5 seconds, and the firing time for hardening and forming the core is set.

  The combustion gas supplied to the gas burner 2 is generally a mixed gas of gas and air, and the supply of the gas-air mixed gas is performed by, for example, setting the mold temperature at which the mold 1 is heated as described above. When the temperature is set to 270 ° C., for example, in the conventional apparatus described in Patent Document 1 below, the burner control in which the mold is heated by the gas burner is performed by setting the temperature of the mold to 270 ° C. In the following cases, the supply amount of the gas-air mixed gas is increased so that the mold becomes close to 270 ° C. until the mold is close to 270 ° C. If the mold temperature exceeds the set temperature of 270 ° C., the heat is reduced. Switching to reduce the supply amount of the gas-air mixed gas has been performed. The two-stage switching of the gas-air mixed gas between high heat and low heat has been performed by on / off control of a solenoid valve. For example, switching to increase the supply amount of the gas-air mixed gas so as to increase the heat is performed by controlling the solenoid valve to be turned on, and conversely, switching to decrease the supply amount of the gas-air mixture gas to reduce the heat is performed by, for example, switching the electromagnetic valve. Off control was performed.

In the conventional on / off control of the supply amount of the gas-air mixed gas, since a high or low heat is set based on the set temperature as described above, the mold temperature is increased from the set value of 270 ° C. during the casting operation. In accordance with the rise or fall, just by switching the gas-air mixture gas supply in two stages to achieve high or low heat by controlling the supply of gas-air mixed gas as described above, rapid temperature control for the mold can be achieved. It could not be performed, and a variation of plus or minus 10 ° C. or more with respect to the set temperature occurred, and this caused the occurrence of uneven printing in the manufactured core.
Furthermore, the fire often went out when switching from high to low or from low to high.

JP-A-10-58088

  In view of the fact that the on-off control of the supply amount of the gas-air mixed gas cannot respond to the ever-changing mold temperature in the conventional mold heating apparatus described above, the present invention immediately follows the ever-changing mold temperature. It is an object of the present invention to propose a mold heating apparatus capable of constantly supplying a supply amount of a gas-air mixed gas corresponding to a mold temperature.

In order to achieve the above object, in the invention according to claim 1, the gas burner 2 for heating the core manufacturing die 1 is provided with a core manufacturing die. A mold heating device for core production, which is provided facing the back side of the mold 1 and heats the mold 1 by the gas burner 2;
The temperature measurement information of the mold 1 obtained from the heating temperature of the mold 1 is transmitted to the temperature control device 3 which sets the heating temperature in advance, and the temperature control device 3 controls the inverter 4 by PID. If the heating temperature of the core manufacturing mold 1 transmitted to the temperature control device 3 is lower than a preset heating temperature, the output of the blower 6 provided in the air supply circuit 5 is increased by the inverter 4. The air having an increased air flow rate is introduced into the venturi mixer 7 by the blower 6 having the increased output, and the air having the increased air flow rate is introduced into the venturi mixer 7. Suction power increases,
On the other hand, the fuel gas flowing through the fuel gas supply circuit 8 is sucked and introduced into the air supply circuit 5 having an increased suction force of the venturi mixer 7, whereby the flow rate of the gas-air mixed gas is increased in the air supply circuit 5. A gas-air mixed gas circuit 5A is formed,
At this time, a zero governor 9 is interposed in the fuel gas supply circuit 8, and a loading circuit 10 for branching the gas-air mixed gas circuit 5A and introducing the pressure in the circuit to the zero governor 9 as a loading pressure is provided. The gas pressure of the gas-air mixed gas circuit 5A is provided as a loading pressure to the zero governor 9 through the loading circuit 10 so that the gas flow rate of the fuel gas in the fuel gas supply circuit 8 is reduced by the gas-air mixed gas circuit. 5A is introduced into the air supply circuit 5 in proportion to the increase of the gas air flow rate,
Thus, while maintaining the gas-air mixing ratio constant, the gas-air mixed gas having an increased supply pressure is supplied to the mold heating gas burner 2 to reduce the low heating temperature of the core manufacturing mold 1. Heat over high heat to approach the preset heating temperature,
On the other hand, if the heating temperature of the mold for core production transmitted to the temperature control device 3 becomes higher than a preset heating temperature, the output of the blower 6 provided in the air supply circuit 5 is reduced by the inverter 4. The air having a reduced air flow rate is introduced into the venturi mixer 7 by the blower 6 having a reduced output, and the air having a reduced air flow rate is introduced into the venturi mixer 7, whereby the Venturi mixer 7 The suction power decreases
On the other hand, the fuel gas flowing through the fuel gas supply circuit 8 is sucked into the air supply circuit 5 having a reduced suction force of the venturi mixer 7, whereby the gas supply gas 5 having a reduced flow rate of the gas-air mixed gas is supplied to the air supply circuit 5. A mixed gas circuit 5A is formed,
At this time, the gas pressure of the gas-air mixed gas circuit 5A from the gas-air mixed gas circuit 5A in which the flow rate of the gas-air mixed gas is reduced is loaded to the zero governor 9 as a loading pressure through the loading circuit 10 so that the fuel gas supply circuit 8 Is introduced into the air supply circuit 5 in proportion to the decrease in the gas air flow rate of the gas-air mixed gas circuit 5A,
Thus, while maintaining the gas-air mixing ratio constant, the gas-air mixed gas having a reduced supply pressure is supplied to the mold heating gas burner 2 to raise the high heating temperature of the core manufacturing mold 1 in advance. The heating is performed over a low heat so as to approach the set heating temperature. In this way, the heating temperature of the core manufacturing die 1 is always maintained at a predetermined heating temperature ,
At this time, the zero governor 9 interposed in the fuel gas supply circuit 8 forms a primary gas path 27 and a secondary gas path 28 with a counter valve 26 provided in the zero governor 9 interposed therebetween. The governor chamber 29 is divided into an upper chamber 31 and a lower chamber 32 by a main diaphragm 30. The upper chamber 31 has an inlet 33 connected to the loading circuit 10 that receives the loading pressure of the air supply circuit 5 that increases and decreases the air flow rate. A counter spring 34 is provided to withstand the gas pressure of the primary gas passage 27 of the fuel gas supply circuit 8 via the main diaphragm 30. The lower chamber 32 is connected to the upper main diaphragm 30 and the lower The counter valve 2 is formed so as to be surrounded by the balance diaphragm 35 and penetrates through the lower chamber 32. The valve stem 36 is mounted, the valve stem 36 moves up and down following the main diaphragm 30, and the balance diaphragm 35 follows the vertical movement of the valve stem 36. It consists of a heating device.

In the invention according to claim 2 , the gas-air mixed gas circuit 5A connected to the gas burner 2 bends and deforms following the displacement of the core manufacturing die 1 during operation, and the gas-air mixed gas flows when the gas-air mixed gas flows. 2. The mold heating apparatus for core production according to claim 1 , wherein the mixed gas is formed by a hard rubber tube 37 which is less susceptible to internal resistance.

  According to the first aspect of the invention, the adjustment of the supply amount of the gas-air mixed gas from the gas-air mixed gas circuit 5A to the gas burner 2 is performed by automatic adjustment in proportion to the heating temperature of the core manufacturing die 1. I made it. That is, a temperature control device 3 that constantly receives information on the heating temperature of the core manufacturing die 1 with time, and an inverter 4 that is PID-controlled by the temperature control device 3 in response to an increase or decrease in a preset heating temperature of the die 1. A blower 6 in which the amount of air supplied to the venturi mixer 7 is controlled by the PID control of the inverter 4, the air from the air supply circuit 5 and the fuel gas from the fuel gas supply circuit 8 are mixed at a fixed ratio. A venturi mixer 7 for controlling the supply amount of the gas-air mixed gas to the gas burner 2 is provided. The function of these mechanisms is used to check the ever-changing value of the mold temperature during operation. The temperature can be automatically adjusted over time to the best mold temperature set in advance, which makes it possible to fire a stable core without unevenness. It is.

  Then, according to the present invention, at this time, the gas pressure of the gas-air mixed gas circuit 5A from the gas-air mixed gas circuit 5A whose flow rate of the gas-air mixed gas is increased or decreased is loaded on the zero governor 9 as a loading pressure through the loading circuit 10. Thereby, the gas flow rate of the fuel gas in the fuel gas supply circuit 8 is introduced into the air supply circuit 5 in proportion to the increase / decrease of the gas air flow rate in the gas / air mixing gas circuit 5A, so that the mixing ratio of the gas / air is kept constant. In this state, the gas-air mixed gas whose supply pressure has been increased or decreased is supplied to the gas burner 2 for heating the mold so that the heating temperature of the mold 1 for manufacturing the core approaches a preset heating temperature. The heating temperature of the core manufacturing die 1 is constantly raised to a predetermined heating temperature. Lifting and has been led to the core of good quality is fired form.

At this time, the zero governor 9 interposed in the fuel gas supply circuit 8 has a primary gas passage 27 and a secondary gas passage 27 sandwiching a counter valve 26 provided in the zero governor 9 as shown in FIG. The governor chamber 29 of the zero governor 9 is divided into an upper chamber 31 and a lower chamber 32 by a main diaphragm 30, and the upper chamber 31 is loaded with a loading pressure of the increasing or decreasing air flow rate of the air supply circuit 5. An inlet 33 connected to the circuit 10 is provided, and a counter spring 34 is provided through the main diaphragm 30 to withstand the gas pressure in the primary gas passage 27 of the fuel gas supply circuit 8. The lower chamber 32 is formed by being surrounded by the main diaphragm 30 and a lower-side balance diaphragm 35. The valve stem 36 of the counter valve 26 is attached through the valve diaphragm 36. The valve stem 36 moves up and down following the main diaphragm 30, and the balance diaphragm 35 follows the vertical movement of the valve stem 36. The counter valve 26 is attached to the counter spring 34, the main diaphragm 30 supported by the counter spring 34, and the balance diaphragm 35 even if the primary gas pressure of the primary gas path 27 changes across the zero governor 9. Therefore, these members absorb changes in the primary gas pressure, the opening degree of the counter valve 26 does not fluctuate greatly, and the secondary gas pressure is not affected by changes in the primary gas pressure. On the other hand, the upper chamber 31 of the governor chamber 29 of the zero governor 9 is provided with the inlet 33 connected to the loading circuit 10 which receives the loading pressure of the air supply circuit 5 which increases and decreases the air flow rate. The gas pressure of the gas-air mixed gas circuit 5A from the gas-air mixed gas circuit 5A whose flow rate has increased or decreased is loaded on the zero governor 9 as a loading pressure through the loading circuit 10 so that the opening degree of the counter valve 26 of the zero governor 9 is reduced. The gas flow rate of the fuel gas in the fuel gas supply circuit 8 is introduced into the air supply circuit 5 in proportion to the increase and decrease in the gas air flow rate of the gas-air mixed gas circuit 5A. Heat the heating temperature to a high or low heat so that it approaches the preset heating temperature. In this way, it is possible to maintain at all times a predetermined heating temperature and the heating temperature of the core manufacturing mold 1.

In the invention according to claim 2 , the gas-air mixed gas circuit 5A connected to the gas burner 2 bends and deforms following the displacement of the core manufacturing die 1 during operation, and the gas-air mixed gas flows when the gas-air mixed gas flows. The mixed gas is formed by a hard rubber tube 37 which is less susceptible to in-tube resistance and is flexible.
When the gas-air mixture gas is supplied from the gas-air mixture gas circuit 5A to the gas burner 2, if the supply pressure of the gas-air mixture gas is small, the gas-air mixture gas may be insufficiently supplied due to the resistance in the tube of the gas-air mixture gas circuit 5A. . Therefore, the forming member of the gas-air mixed gas circuit 5A bends and flexes following the displacement during the operation of the mold 1 for manufacturing the core, and the mixed gas does not receive resistance in the tube when the gas-air mixed gas flows, and is flexible. (See FIG. 1), and the supply pressure of the gas-air mixed gas circuit 5A is applied to the zero governor 9 via the loading circuit 10, and the opening degree of the on-off valve (counter valve 26) is adjusted. By increasing the flow rate, the gas flow rate of the fuel gas supply circuit 8 is sufficiently supplied to the air supply circuit 5, and as a result, the supply pressure of the gas / air mixture gas circuit 5A is increased to smoothly feed the gas / air mixture gas to the gas burner 2. To be able to supply.

1 is a supply control circuit of a gas-air mixed gas of one embodiment according to the present invention. It is sectional drawing of the schematic structure of a component which shows the principal part of the supply control circuit of the said gas air mixed gas. FIG. 3 is a cross-sectional view of a generally used mold heating device.

As shown in FIG. 3, the inside of the mold support frame 12 faces the back side of the core manufacturing mold 1 attached to the mold block 11 via the mold support frame 12 and the mold mounting plate 13. Many gas burners 2 are installed. The gas burner 2 is attached to a front plate 15 of a hollow mounting plate 14, and a gas supply pipe 17 for supplying a gas-air mixed gas to a hollow portion 16 of the hollow mounting plate 14 is provided.
The gas supply pipe 17 is formed by a flexible hard rubber tube 37. The gas burner 2 connected to the gas supply pipe 17 is displaced integrally with the core manufacturing die 1 during the core firing operation. That is, the mold 1 for manufacturing a core is composed of a fixed mold and a movable mold. In both cases, when the core fired by the mold is taken out, when the mold is filled with mold sand, or when the mold is used. The mold is rotated and displaced when the mold sand is discharged, and in the case of a movable mold, the mold is largely moved in the horizontal direction, and follows the core manufacturing mold 1 which is largely displaced during this work. The gas supply pipe 17 must be connected so that the gas-air mixed gas flowing inside the pipe is connected to the internal resistance of the gas supply pipe 17 if the pipe is connected by an elbow pipe bent at a right angle by an elbow pipe or the like. As a result, when the gas pressure of the gas-air mixed gas is low, a situation in which the gas does not flow sufficiently occurs. Therefore, the forming member of the gas-air mixed gas circuit 5A bends and flexes following the displacement during the operation of the mold 1 for manufacturing the core, and the mixed gas does not receive resistance in the tube when the gas-air mixed gas flows, and is flexible. The gas-air mixed gas can be smoothly circulated by the formation of the hard rubber tube 37 having the shape.

  The gas-mixed gas blown from the gas burner 2 and burned heats the mold 1 for manufacturing the core facing the gas, and heats the mold sand S filled in the cavity 18 of the mold 1 to fire the core. Will be formed.

  FIG. 1 shows a control circuit of one embodiment for controlling the supply of a gas-air mixed gas to a gas burner 2.

  A thermocouple 19 for measuring the heating temperature of the mold 1 is installed in the mold 1 for core production, and the heating temperature of the mold 1 measured by the thermocouple 19 is sent to the temperature controller 3 by the temperature measurement circuit 20. Is transmitted. The optimal heating temperature of the core manufacturing die 1 is set in the temperature control device 3, and the heating temperature transmitted from the core manufacturing die 1 to the temperature control device 3 and the temperature adjustment device 3 are set in advance. The heating signal is compared with the set heating temperature, and the comparison signal is transmitted to the inverter 4 by the comparison signal transmission circuit 21 at 4 to 20 mA / 0 to 60 Hz. The control signal from the inverter 4 is transmitted at 5 to 60 Hz to the blower 6 provided in the air supply circuit 5 by the inverter control circuit 22 and responds to the control signal from the inverter 4 transmitted by the inverter control circuit 22. The blower 6 outputs the number of rotations to control the air flow rate of the air supply circuit 5. 5a is an air supply source connected to the outside air.

  Then, the temperature control device 3 switches the AUTO, OFF, and MAN switching contacts of the operation switch 24 provided in the circuit 23 of the power supply M to the AUTO contact, and inputs the temperature control device 3 to the operating state. When the heating temperature of the die 1 for manufacturing a child is transmitted to the temperature control device 3 through the temperature measurement circuit 20 by the thermocouple 19, the heating temperature transmitted to the temperature control device 3 is preset in the temperature control device 3. For example, if the heating temperature is lower than the optimum heating temperature of 270 ° C., information on the lower heating temperature is transmitted from the temperature controller 3 to the inverter 4, and a control signal for increasing the output of the blower 6 by the inverter 4 is transmitted to the blower 6. Then, the air flow rate of the air supply circuit 5 is increased by the blower 6, and the increased air flow rate causes a venturi mixer connected thereto. -7 is increased, and the fuel gas supplied from the fuel gas supply circuit 8 via the gas supply source 8a such as a gas cylinder and the flow rate regulating valve 25 is supplied to the air by the venturi mixer 7 having the increased suction force. The fuel gas is supplied to the supply circuit 5 in an increased manner, whereby the fuel gas, which is increased in proportion to the increase of the air flow rate by the suction force of the venturi mixer 7 whose suction force is increased, is sucked into the air supply circuit 5. Thus, while maintaining the gas-air mixing ratio constant, the gas-air mixed gas having an increased supply pressure is introduced into the gas burner 2 for heating the mold, so that the heating temperature of the mold 1 for core production is increased. Is heated by the gas burner 2 so as to approach a preset 270 ° C.

  On the other hand, when the heating temperature of the operating core manufacturing die 1 is transmitted to the temperature control device 3 through the temperature measurement circuit 20 by the thermocouple 19, the heating temperature transmitted to the temperature control device 3 becomes the temperature. If the heating temperature is higher than, for example, the optimum heating temperature of 270 ° C. set in advance in the adjusting device 3, information on the high heating temperature is transmitted from the temperature adjusting device 3 to the inverter 4, and the inverter 4 reduces the output of the blower 6. The signal is transmitted to the blower 6, the air flow of the air supply circuit 5 is reduced by the blower 6, and the suction force of the venturi mixer 7 connected thereto is reduced by the reduced air flow, thereby reducing the suction force. The fuel gas supplied from the fuel gas supply circuit 8 by the venturi mixer 7 is supplied to the air supply circuit 5 in a reduced amount. As a result, the fuel gas reduced in proportion to the decrease in the air flow rate is sucked into the air supply circuit 5 by the suction force of the venturi mixer 7 in which the suction force has decreased, and the mixing ratio of the gas air is kept constant. In the held state, the gas-air mixed gas having a reduced supply pressure is supplied to the gas burner 2 for heating the mold, so that the heating temperature of the mold 1 for manufacturing a core does not approach a preset 270 ° C. The mold 1 for core production is heated by the gas burner 2 so that the core 1 can be opened.

  At this time, the zero governor 9 interposed in the fuel gas supply circuit 8 has a primary gas passage 27 and a secondary gas passage 27 sandwiching a counter valve 26 provided in the zero governor 9 as shown in FIG. The governor chamber 29 of the zero governor 9 is divided into an upper chamber 31 and a lower chamber 32 by a main diaphragm 30, and the upper chamber 31 is loaded with a loading pressure of the increasing or decreasing air flow rate of the air supply circuit 5. An inlet 33 connected to the circuit 10 is provided, and a counter spring 34 is provided through the main diaphragm 30 to withstand the gas pressure in the primary gas passage 27 of the fuel gas supply circuit 8. The lower chamber 32 is formed by being surrounded by the main diaphragm 30 and a lower-side balance diaphragm 35. The valve stem 36 of the counter valve 26 is attached through the valve diaphragm 36. The valve stem 36 moves up and down following the main diaphragm 30, and the balance diaphragm 35 follows the vertical movement of the valve stem 36. The counter valve 26 is attached to the counter spring 34, the main diaphragm 30 supported by the counter spring 34, and the balance diaphragm 35 even if the primary gas pressure of the primary gas path 27 changes across the zero governor 9. Therefore, the change in the primary gas pressure is absorbed by these members, the opening degree of the counter valve 26 does not largely change, and the change in the secondary gas pressure is not affected by the change in the primary gas pressure. On the other hand, the upper chamber 31 of the governor chamber 29 of the zero governor 9 is provided with the inlet 33 connected to the loading circuit 10 which receives the loading pressure of the air supply circuit 5 which increases and decreases the air flow rate. When the gas pressure of the gas-air mixed gas circuit 5A from the gas-air mixed gas circuit 5A whose flow rate has increased or decreased is loaded on the zero governor 9 as a loading pressure through the loading circuit 10, the opening degree of the counter valve 26 of the zero governor 9 is reduced. The gas flow rate of the fuel gas in the fuel gas supply circuit 8 is introduced into the air supply circuit 5 in proportion to the increase and decrease in the gas air flow rate of the gas-air mixed gas circuit 5A. Heat the heating temperature to a high or low heat every time to approach the preset heating temperature. It was so.

The automatic operation work of the worker will be described based on the control circuit shown in FIG. 1. First, the temperature control device 3 sets the mold temperature (target value) within a range of 250 to 350 ° C., for example, 270 ° C. Next, the switching contact of the operation switch 23 is switched to the AUTO contact. When the mold temperature after the replacement of the mold 1 is lower than the set temperature set by the temperature control device 3, for example, 270 ° C., the maximum output signal is output from the temperature control device 3, whereby the inverter 4 also outputs a signal. A maximum output, for example, an output signal having a frequency of 60 Hz is supplied to the blower 6. As a result, the blower 6 has the maximum air volume, and the mold temperature rises.
In this way, the worker fills the mold 1 with the mold sand S at the start of the work, and when heating the mold 1, sets the heating temperature to high heat in accordance with the set temperature. Adjustment is performed and the set temperature is maintained, it changes in the range of plus or minus 2 ° C to 5 ° C, and there is no sudden change from high to low or low to high, so the fire does not extinguish and the appropriate burner Expect to burn chips.

  By the above operation, when the mold temperature approaches the target temperature of 270 ° C., the air flow from the blower 6 is reduced by the PID control of the temperature control device 3 and the inverter 4 (inverter 4 deceleration), and the mold temperature becomes the set temperature. Or by automatically controlling the wind power of the blower 6 by the above PID control even if the mold temperature exceeds the set temperature, so that the mold temperature is controlled so as to always maintain the set temperature. .

  As described above, according to the present invention, while the heating temperature that changes every time during the operation of the mold 1 is confirmed by the PID control by the temperature control device 3 and the inverter 4, the mold temperature is set in advance to the best mold. The temperature of the mold can be automatically adjusted with time, whereby a stable core can be fired without unevenness.

S-type sand 1 Core manufacturing mold 2 Gas burner 3 Temperature controller 4 Inverter 5 Air supply circuit 6 Blower 7 Venturi mixer 8 Fuel gas supply circuit 9 Zero governor 10 Loading circuit

Claims (2)

A gas burner for heating the core manufacturing die is provided facing the back side of the core manufacturing die, and the core manufacturing die heating device for heating the die by the gas burner. ,
The temperature measurement information of the mold obtained from the heating temperature of the mold is transmitted to a temperature control device that sets a heating temperature in advance, and the temperature control device includes a mechanism for performing PID control of an inverter. When the heating temperature of the core manufacturing mold transmitted to the control device becomes lower than the preset heating temperature, the output of the blower provided in the air supply circuit is increased by the inverter, and the air flow rate is increased by the blower having the increased output. The increased air is introduced into the venturi mixer, and the air with the increased air flow is introduced into the venturi mixer, whereby the suction force of the venturi mixer increases,
On the other hand, the fuel gas flowing through the fuel gas supply circuit is sucked and introduced into the air supply circuit having an increased suction force of the venturi mixer, whereby the gas / air mixture gas circuit having the increased flow rate of the gas / air mixture gas is supplied to the air supply circuit. Formed,
At this time, a zero governor is interposed in the fuel gas supply circuit, and a loading circuit for branching the gas-air mixed gas circuit and introducing the pressure in the circuit as the loading pressure to the zero governor is provided. When the gas pressure of the gas-air mixture gas circuit is loaded on the zero governor as a loading pressure through the circuit, the gas flow rate of the fuel gas in the fuel gas supply circuit is proportional to the increase in the gas-air flow rate of the gas-air mixture gas circuit. And introduced into the air supply circuit,
Thus, while maintaining the gas-air mixing ratio constant, the gas-air mixed gas having the increased supply pressure is supplied to the mold heating gas burner, and a low heating temperature of the core manufacturing mold is set in advance. High heat to approach the heating temperature
On the other hand, if the heating temperature of the core manufacturing mold transmitted to the temperature control device becomes higher than the heating temperature preset in the temperature control device, the output of the blower provided in the air supply circuit is changed by the inverter. By reducing the output, the blower with reduced output introduces air with reduced air flow into the venturi mixer, and the air with reduced air flow is introduced into the venturi mixer, thereby suctioning the venturi mixer. On the other hand, the fuel gas flowing through the fuel gas supply circuit is sucked into the air supply circuit with reduced suction force of the venturi mixer, whereby the gas air having a reduced flow rate of the gas-air mixed gas is supplied to the air supply circuit. A mixed gas circuit is formed,
At this time, the gas pressure of the gas-air mixed gas circuit from the gas-air mixed gas circuit having a reduced flow rate of the gas-air mixed gas is loaded to the zero governor by the loading pressure through the loading circuit, so that the fuel gas of the fuel gas supply circuit is The gas flow rate is introduced into the air supply circuit in proportion to the decrease in the gas air flow rate of the gas-air mixed gas circuit,
Thus, while maintaining the gas-air mixing ratio constant, the gas-air mixed gas having a reduced supply pressure is supplied to the mold heating gas burner, and a high heating temperature of the core manufacturing mold is set in advance. Heating over low heat to approach the heating temperature
In this way, the heating temperature of the core manufacturing mold is always maintained at a predetermined heating temperature ,
At this time, the zero governor interposed in the fuel gas supply circuit has a primary side gas path and a secondary side gas path with a counter valve provided in the zero governor interposed therebetween, and the governor chamber of the zero governor is located above the main diaphragm by a main diaphragm. The upper chamber is provided with an inlet that is connected to a loading circuit that receives a loading pressure of an increasing or decreasing air flow rate of the air supply circuit, and the upper chamber is provided with a fuel gas supply circuit through the main diaphragm. A counter spring against the gas pressure of the primary gas passage is provided, and the lower chamber is formed by being surrounded by an upper main diaphragm and a lower balance diaphragm, and penetrates through the lower chamber to form a valve stem of a counter valve. The valve stem moves up and down following the main diaphragm. Balance diaphragm core manufacturing mold heating apparatus comprising so as to follow the vertical movement of the valve stem. The gas-air mixed gas circuit connected to the gas burner bends and flexes in accordance with the displacement of the core manufacturing mold during operation, and the gas-mixed gas does not receive resistance in the tube when flowing the gas-air mixed gas. The mold heating apparatus for manufacturing a core according to claim 1, wherein the heating apparatus is formed by a hard rubber tube having a core.

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