Title of Invention	A TEMPERATURE SENSOR FOR A CASTING MACHINE
Abstract	The temperature sensor comprises a protective metal fitting 22 having a draft angle or taper along its top end. The protective metal fitting 22 is made of the same material as a die. The temperature sensor also comprises a thermocouple inserted in the protective metal fitting 22 to be connected to the top end thereof. The top end of the protective metal fitting 22 is mounted to the die so as to protrude into a casting space in the die.

Title of Invention

A TEMPERATURE SENSOR FOR A CASTING MACHINE

Abstract

The temperature sensor comprises a protective metal fitting 22 having a draft angle or taper along its top end. The protective metal fitting 22 is made of the same material as a die. The temperature sensor also comprises a thermocouple inserted in the protective metal fitting 22 to be connected to the top end thereof. The top end of the protective metal fitting 22 is mounted to the die so as to protrude into a casting space in the die.

Full Text	Specification CASTING MACHINE AND TEMPERATURE SENSOR FOR THE SAME Field of the Invention [0001] The present invention relates to a casting machine and a temperature sensor for the same used for directly detecting a molten metal temperature. Background Art [0002] Conventionally, a cylinder head for a motorcycle engine is made by a low pressure casting method, for example. JP-B-3201930 discloses this type of low pressure casting machine . The casting machine disclosed in this patent document has: a die including a lower and an upper die; and a crucible disposed below the die; and is designed to pressurize molten metal reserved in the crucible to force it up through a stalk to be supplied to a sprue of bhe lower die. [0003] For the purpose of improvement in productivity, the operation processes of the casting machine from the start of molten metal supply to die opening are automated. To be more specific, after an operator turns a start switch on, the casting machine calculates the time period for which molten metal is supplied (hereinafter referred to as pressurization time) based on the die and molten metal temperatures, to pressurize the molten metal during this pressurization time and then supply it into the die. A temperature sensor embedded in the die detects the die temperature, while another temperature sensor provided in the crucible detects the molten metal temperature. The preset pressurization time is so long that the molten metal fills the die after the pressurization start and a solidifying region of the molten metal expands from the upper to lower parts of the die to reach inside of the sprue. [0004] In other words, completing pressurization of the molten metal after the lapse of the pressurization time allows the unsolidified metal to flow from the sprue through the stalk to 1 drop back into the crucible. Only the solidified molten metal remains inside the sprue. Under this condition, the solidified casting in the die has no flowability but is still soft enough to be easily deformed if it is taken out of the die. This substantially decreases the die shape and dimension accuracies . Thus, this casting machine is designed to open the die after a standby period during which the casting becomes hard enough not to deform after pressurization of the molten metal is completed. A time period from the point in time at which pressurization of the molten metal is completed until the point in time at which the die is opened (hereinafter referred to as solidification time) is obtained by calculation based on the die temperature at the time when pressurization of the molten metal is completed. Disclosure of the invention Problem to be Solved by the Invention [0005] It has not been possible for a conventional type of casting machine configured as above to detect the temperature of the casting during the casting process, and therefore not possible to complete pressurization of the molten metal or open a die in the timeliest manner in accordance with an actual solidification rate of the molten metal. Thus, the conventional type of casting machine presets the pressurization and solidification times long enough to ensure that the pressurization and solidification of the molten metal are completely done . This leads to a longer cycle time and therefore to a decrease in productivity. [0006] These problems could be solved by using a temperature sensor to directly detect the temperature of the casting. In addition, such a temperature sensor should be manufactured so as to overcome other problems, including possible breakages of part of the temperature sensor, which is in contact with the casting, due to heat or a pressing force of the molten metal, and wear and tear caused by the casting at the time of opening 2 the die or separating the casting from the die. [0007] The present invention is made in view of the foregoing problems. A first object of the invention is to provide a temperature sensor for the casting machine, which can be prevented from breakages due to heat or a pressing force of the molten metal while being easily removed from the casting. A second object of the invention is to reduce a cycle time of the casting machine by using the temperature sensor. Means for Solving the Problem [0008] The present invention provides a temperature sensor for a casting machine, which is made of the same material as a die, including: a protective metal fitting having a draft angle or taper along its top end; and a thermocouple inserted in the protective metal fitting to be connected to the top end thereof, in which the top end of the protective metal fitting is mounted to the die so as to protrude into a casting space in the die. Effect of the Invention [0009] The protective metal fitting of the temperature sensor for a casting machine defined in Claims 1 and 2 has a refractoriness and strength as high as those of the die, and is removed together with the die from the casting. The present invention therefore provides a temperature sensor for a casting machine, which can be prevented from breakages due to heat or pressure of the molten metal, and be easily removed from the casting without wear and tear caused by the casting at the time of opening the die or separating the casting from the die. [0010] In the inventions of Claims 3 and 4, the temperature sensor is used to directly detect the temperature of the molten metal that solidifies later than at the cavity. This allows the molten metal supply to stop or the die to open when the temperature of the casting reaches an optimum temperature for stopping the molten metal supply or opening the die. 3 [0011] As a result, in the casting machine according to the present invention, it is possible to reduce the supply time for the molten metal and the solidification time, from the stop of the molten metal supply to die-opening, to a period required for casting without any defective product as soon as possible. This therefore further improves the productivity with the reduced casting cycle time. In addition, the present invention allows detection of the temperature of the interior molten metal while allowing the protective metal fitting of the temperature sensor to be easily removed from the casting after the casting process . This makes it possible to prevent the protective metal fitting from being broken when the die is opened or the casting is separated from the die while detecting the temperature of the molten metal with high accuracy. Brief Description of Drawings [0012] FIG. 1A is a vertical sectional view of dies to which a temperature sensor of the present invention is mounted. FIG. IB is a cross-sectional view of the dies to which the temperature sensor of the present invention is mounted. FIG. 2 is an enlarged sectional view, showing the temperature sensor mounted to a lower die. FIG. 3 is an enlarged sectional view of the temperature sensor. FIG. 4 is a flowchart for the purpose of explaining the operation of a casting machine. FIG. 5 is a graph, illustrating how a molten metal temperature changes in a runner. FIG. 6A is a cross-sectional view of dies used for a gravity casting machine. FIG. 6B is a vertical sectional view of the dies used for the gravity casting machine. FIG. 7A is a cross-sectional view of the dies used for the gravity casting machine. FIG. 7B is a vertical sectional view of the dies used for 4 the gravity casting machine. FIG. 8 is a flowchart for the purpose of explaining the casting operation. FIG. 9 is a graph, illustrating how a molten metal temperature changes. Best Mode for Carrying Out the Invention [0013] (First Embodiment) Now, an embodiment of this invention is described with reference to the drawings. In FIG. 1A, FIG. IB through FIG. 5, reference numeral 1 denotes a die to which a temperature sensor 2 of the first embodiment is attached. The die 1 is mounted to a low-pressure casting machine (not shown) and includes an upper die 4 mounted to a platen of the casting machine by an upper support member 3 and a lower die 6 supported on a base of the casting machine through a lower support member 5. The casting machine is designed to drive the platen to move the upper die 4 up from/down to the lower die 6 respectively for die-opening/clamping. The metal used for casting by the die 1 is aluminum alloy. [0014] The upper die 4 is formed with a cavity 7 having a downward opening. The lower die 6 is formed with a cavity 8 having an upward opening . In the first embodiment, the cavities 7, 8 refer to a recess for forming the product part of the casting. The upper die 4 and the lower die 6 are provided with a heater (not shown) for preheating them to a temperature ready for casting and a water-cooling device (not shown) for maintaining the die temperature during the casting process. [0015] As shown in FIGs. 1A, IB and 2, at the inner bottom of the lower die 6 is formed a runner 9 that extends from one side of the cavity 8 to the other. A sprue 10 is also formed at the inner bottom of the lower die 6 that extends downward from the bottom of the runner 21. The temperature sensor 2 of the present invention is so attached to face inside of the runner 9. 5 As shown in FIG. IB, the sprue 10 is formed at the bottom of the lower die 6 so as to have an elliptic shape when viewed from above, by drilling to create a draft angle such that an opening diameter of the sprue 10 becomes larger toward the top as shown in FIG. 2. [0016] A filter 11 for preventing foreign materials from entering inside the die is attached to the opening at the upper end of the sprue 10. The bottom end of the sprue 10 is connected to the top end of a sprue cup 12 provided in the lower support member 5. The sprue cup 12 runs through the lower support member 5 in the vertical direction. The molten metal 13 is supplied from the top end of a stalk (not shown) which comes into contact with the bottom surface of the lower support member 5. [0017] To be more specific, the bottom end of the stalk is dipped in the molten metal within a crucible (not shown) contained in a furnace (not shown). Pressurizing a surface of the molten metal 13 in the crucible during the casting process allows the molten metal 13 to flow from the stalk through the sprue 10 cup into the sprue 10. The molten metal 13 flows from the sprue 10 through the filter 11 into the runner 9 and then into the cavities 7, 8. The molten metal 13, filling the die 1 in this manner, starts solidifying within the cavities 7, 8 {a product part 14 (See FIG. 2)}. [0018] A solidifying region of the molten metal 13 expands from the cavities 7, 8 into the runner 9, and then into the sprue 10 with the lapse of time. The casting machine of the first embodiment uses the temperature sensor 2, which will be described later, to directly detect the temperature of the molten metal 13 in part of the casting, namely, a runner part, after the start of pressurization of the molten metal 13 The solidification of the molten metal 13 can be detected based on the temperature of the molten metal 13, and the casting machine thus completes pressurization of the molten metal 13 when the 6 solidification of the molten metal 13 expands adjacent to a boarder between the sprue 10 and the runner 9. The pressurization of the molten metal 13 is completed in this manner, which causes the unsolidified metal in the sprue cup 12 or the stalk to drop into the crucible. The casting machine then opens the die when the temperature of the molten metal 13 (a casting) decreases to a certain level. [0019] The temperature sensor 2, as shown in FIG. 3, includes a protective metal fitting 22, which includes: a protective portion 2a extending in the vertical direction; a support portion 2b formed, at the base end of the protective portion 2a, into one body together with the protective portion 2a; and a through hole 21 axially passing through the protective metal fitting 22. The temperature sensor 2 also includes a thermocouple 23 inserted in the through hole 21, and is fitted into a mounting hole 24 drilled in the lower die 12. As shown in FIG. 3, the mounting hole 24 consists of a small diameter portion 24a, having an opening in the runner 9, into which the protective portion 2a is fitted, and a large diameter portion 24b, having an opening directed outward of the die, into which the support portion 2b is fitted. The mounting hole 24 is drilled such that it extends through the lower die 6 in the die-opening direction (the vertical direction in FIG. 3) adjacent to the side of the sprue 10 in the lower die 6. [0020] The support portion 2b fitted in the large diameter portion 24b limits a position of the protective metal fitting 21, which is mounted to the lower die 6, to a position where it cannot be inserted further inward of the die 1 from the position shown in the drawing. The protective metal fitting 22 and the lower die 6 are made of the same material. In the first embodiment, alloy tool^ steel (SKD) for hot dies is employed. The length of the protective portion 2a of the protective metal fitting 22, which is fitted in the mounting hole 24 together with the support portion 2b, is so designed that a 7 temperature detecting section 25 or the top end of the protective metal fitting 22 protrudes into the runner 9. In other words, the protective metal fitting 22 is mounted to the lower die 12, with the temperature detection section 25 protruding into a casting space (runner 9) in the die. The temperature detecting section 25 of the protective metal fitting 22 is formed, having an outside diameter gradually smaller toward the top end. The casting space also includes regions other than the runner 9, such as the cavities 7, 8 and the sprue 10 in the die 1, to be filled with the molten metal. [0021] In other words, the temperature detecting section 25 of the protective metal fitting 22 is formed with a draft angle or taper. The temperature detection section 25 defines the top end of the temperature sensor in the present invention. In the first embodiment, the temperature detecting section 25 has a dome-shaped tip portion 25a that is convex upward, to which each top end of two types of conductor 23a, 23b of the thermocouple 23 is welded. To be more specific, each top end of the conductors 23a, 23b passing the through hole 24 faces the opening of the tip portion 25a, in order to be welded together to block the opening using a welding electrode made of common material, alloy tool steel (SKD) for hot dies. The welded opening is then ground into a dome-shape. [0022] The well-known, typical alumel-chromel thermocouple 23 is used. It includes the bwo types of conductor 23a, 23b which conduct each other by welding to the temperature detecting section 25 of the protective metal fitting 22. Providing the thermocouple 23 in this manner allows the temperature sensor 2 to detect the temperature of the molten metal 13 which comes into contact with the tip portion 25a (where the thermocouple 23 is welded) of the protective metal fitting 22 (protective portion 2a). [0023] The two conductors 23a, 23b running through the protective 8 metal fitting 22 to the support portion 2b are lead outside of the lower die 6. They are connected to a controller 31 (See FIG. 1A and IB) of the casting machine through the interior of a stainless duct 26 welded to the support portion 2b. In the temperature sensor 2 of the first embodiment, refractory insulating powder 27 is filled around the conductors 23a, 23b in the through hole 21. As the refractory insulating powder 27, there may be magnesia (MgO) used for a glow plug of diesel engines, for example. [0024] The controller 31 is designed to control the operation of the casting machine having the aforementioned die 1, and includes a molten metal temperature controller, a die temperature controller, a pressurization pressure controller, and a casting condition setter. The molten metal temperature controller controls the temperature of the heater of the furnace so as to heat the molten metal 13 in the crucible at a predetermined temperature. The casting condition setter, which will be described later, determines the temperature of the molten metal 13 for each die used. [0025] The die temperature controller controls the temperatures of the heater and the cooling device in the die 1 so as to heat the die 1 at a predetermined temperature. The casting condition setter determines the temperature of each die 1 used. The pressurization pressure controller switches on/off a pressurization device (not shown) for pressurizing the molten metal 13 in the crucible, while controlling the amount of gas to be supplied from the pressurization device so as to make the feed rate of the molten metal 13 from the crucible into the die 1 equal to a predetermined rate. The casting condition setter determines the predetermined feed rate for each die used. [0026] By the casting condition setter, data related to the casting conditions, such as the die and molten metal 9 temperatures, the pressurization and solidification times, and the feed rate of the molten metal 13, in accordance with each die used for the casting process, are sent to the molten metal temperature controller, the die temperature controller and the pressurization pressure controller. The casting condition setter also outputs start/stop signals for the pressurization pressure controller to start/stop pressurizing the molten metal 13 at the respective predetermined timings. The casting condition setter also outputs die-opening/clamping signals for the drive unit 13 to move the upper die 4 up/down respectively at the predetermined timings. [0027] Of these start/stop signals and die-clamping/opening signals, the stop and die-opening signals are sent when the temperature detected with the temperature sensor 2 reaches predetermined temperatures Tl, T2, respectively (See FIG. 5) . The temperature Tl is optimum for completing pressurization of the molten metal 13, and so predetermined that there is no flowability of the molten metal 13 in the product part, the runner part, and the upper part of the sprue due to the solidification therein while the flowability of the molten metal 13 remains on the stalk 9 side from the upper part of the sprue. [0028] In other words, the temperature Tl is predetermined to be the maximum value at which the molten metal 13 only on the stalk 13 side below the upper part of the sprue flows down toward the crucible side even if the pressurization device stops pressurization. As shown in FIG. 3, in the first embodiment, the temperature Tl is so predetermined that the upper portion of the filter 11 can remain in the casting. The temperature T2, lower than the temperature Tl, is optimum for opening the die, and predetermined to be the maximum value at which the molten metal 13 solidifies enough not to have changed casting shape and dimension at die opening. [0029] The casting condition setter of the first embodiment is 10 designed to produce non-defective products even if it is impossible for the temperature sensor 2 to detect the temperatures Tl, T2 due to some malfunction. In other words, the casting condition setter is designed to determine the timings to complete the pressurization of the molten metal 13 and to open the die based on the times (pressurization and solidification times), instead of the temperature detected by the temperature sensor 2, for failure of the temperature sensor 2. To be more detailed, the casting condition setter is designed to complete the pressurization of the molten metal 13 when the predetermined pressurization time has elapsed since the start of the pressurization of the molten metal 13 in the case that the temperature sensor 2 is a defective product or has some malfunction. The casting condition setter is also designed to open the die when the predetermined solidification time has elapsed since the completion of the pressurization of the molten metal 13. [0030] The pressurization time refers to a time period from the point in time when a supply of the molten metal 13 starts to the point in time when a solidifying region of the molten metal 13 expands to the sprue 10 . This pressurization time is obtained by calculation, in accordance with the type of die 1 used, based on the temperature of the die 1 at the start of supplying the molten metal 13, and the temperature of the molten metal 13 in the crucible. The solidification time refers to a period required for the casting inside of the die 1 to solidify enough ,not to easily deform after the completion of the pressurization of the molten metal 13. This solidification time is obtained by calculation, depending on the type of die 1, based on the temperature of the die 1 at the completion of the pressurization of the molten metal 13. These pressurization and solidification times may be stored in a memory (not shown) as a map in advance and read from the memory as needed. [0031] The aforementioned operation of the casting machine is 11 next described in conjunction with the further detailed configuration of the controller 31 with reference to FIGs. 4 and 5. Here, only one operation cycle (one shot) of the casting work, which is repeatedly performed, is described. It is therefore assumed that the casting conditions for each die 1 have already been inputted in the casting condition setter, and the temperatures of the die 1 and molten metal 13 have already reached the targeted casting temperature. Inputs of the casting conditions are achieved by inputting a predetermined number given to an execution program for each die 1. [0032] The casting work of the casting machine with the die 1 clamped is started by, for example, turning the start switch (not shown) ON. When the start switch is turned ON, the casting condition setter first determines whether or not the current temperatures of the die 1 and the molten metal 13 fall within a range for producing non-defective products, as shown in the step Si of FIG. 4. The range for producing non-defective products refers to a temperature range within which the casting can be a non-defective product, which is predetermined for each die. If NO or the aforementioned temperatures fall out of the range for producing non-defective products, the process goes to the step S2 and performs an alarm process in which the casting condition setter gives an operator notice of the abnormal temperatures . This results in stopping the casting operations . [0033] If YES, the casting condition setter calculates the pressurization time of the molten metal 13 (the step S3) which is essential for executing the casting program to be used in the case the temperature sensor 2 fails to function. The casting condition setter then sends the start signal to the pressurization pressure controller together with the data for the feed rate of the molten metal 13 in the step S4. The start signal sent to the pressurization pressure controller in this manner causes the pressurization device to supply inert gas into the furnace. 12 [0034] As a result, the pressurized molten metal 13 is supplied from the stalk through the sprue cup 12, the sprue 10 and the filter 11 into the die 1. Part of the molten metal 13 filling the cavities 7, 8 first solidifies in the product part 14 within the cavities 7, 8. A solidifying region of the molten metal 13 expands from the runner 9 down to the sprue 10 with the lapse of time. In addition, when the pressurization device starts the pressurization as described above, a timer (not shown) also starts simultaneously. [0035] After that, the casting condition setter uses the temperature sensor 2 in the lower die 6 to detect the temperature of the molten metal 13 in the runner 9 in the step S5. As shown in FIG. 5, the temperature detected with the temperature sensor 2 sharply increases after the start of casting (after the start of supplying the molten metal 13) , then remains unchanged (with the molten metal 13 flowing in the runner 9) for a certain period of time, and then gradually decreases. In the step S6, the casting condition setter compares the maximum temperature detected with the temperature sensor 2 with a predetermined temperature range. If the maximum temperature falls within the predetermined temperature range, the casting condition setter determines that the temperature sensor 2 works properly. In contrast, if the maximum temperature falls out of the predetermined temperature range, it determines that the temperature sensor 2 does not work properly (is in an abnormal condition). [0036] In the case it is determined that the temperature sensor 2 is in an abnormal condition in the step S6, when the elapsed time indicated by the timer reaches the pressurization time obtained in the step S3, the casting condition setter sends the stop signal to the pressurization pressure controller. Then the pressurization pressure controller receives the stop signal, which causes the pressurization device to stop the inert gas 13 supply, thereby completing the pressurization of the molten metal 13 (the step S7). Approximately at the same time when the supply of the molten metal 13 is stopped, the casting condition setter calculates the solidification time based on the current temperature of the die 1 (the step S8). [0037] After the stop of supplying the molten metal 13 in the step S7, the unsolidified metal 13 in the die flows from the sprue 10 through the sprue cup 12 and the stalk to drop back into the crucible. The molten metal 13 remaining in the die 1 (with no flowability) further solidifies with increased hardness as the result of no heat supply (the step S9) . When the pressurization of the molten metal 13 is completed, the timer (not shown) starts. Then, the casting condition setter sends the die-opening signal to the drive unit 13 after the time indicated by the timer reaches the solidification time. Then the drive unit 13 receives the die-opening signal, which causes the upper die 4 to move up to open the die (the step 10 to the step 11). [0038] If YES in the step S6 or it is determined that the temperature sensor 2 works properly, the casting condition setter uses the temperature sensor 2 to detect the temperature of the molten metal 13 in the runner 9 in the step S12. The temperature detected with the temperature sensor 2 varies as shown in FIG. 5. After reaching the maximum temperature, it gradually decreases as the molten metal 13 further solidifies. The casting condition setter sends the stop signal to the pressurization pressure controller when the temperature detected with the temperature sensor 2 decreases to the predetermined temperature Tl (the step S13) . Then the pressurization pressure controller receives the stop signal, which causes the pressurization device to stop the inert gas supply, thereby completing the pressurization of the molten metal 13 (the step S14). [0039] When the pressurization of the molten metal 13 is completed, 14 the unsolidified metal 13 drops back into the crucible while the molten metal 13 having no flowability remains in the die 1. This remaining molten metal 13 further solidifies since its temperature further decreases as the result of no heat supply. The casting condition setter uses the temperature sensor 2 to constantly detect the temperature of the molten metal 13 in the runner part as shown in the steps S15, S16. When the temperature of the molten metal 13 detected with the temperature sensor 2 decreases to the predetermined temperature T2, the casting condition setter determines the completion of the solidification and sends the die-opening signal to the drive unit 13. [0040] The drive unit 13 receives the die-opening signal in this manner, which causes the upper die 4 to move up to open the die (the step Sll). One cycle of the casting work ends. At the die-opening, in either case that the casting moves up with the upper die 4, or the casting remains in the lower die 6, the temperature detecting section 25 of the temperature sensor 2 can be easily removed from the casting when it is separated from the lower die 6. This is because the temperature detecting section 25 of the temperature sensor 2 is formed with a draft angle or taper. As described above, the protective metal fitting 22 including the temperature detecting section 25 and the thermocouple welding part are made of the same material as the die, providing excellent wear resistance. This therefore prevents them from being worn out by castings. [0041] Thus, the low-pressure casting machine configured as above performs casting, using the temperature sensor 2 attached to the die 1, which allows the molten metal 13, flowing into the runner 9 from the sprue 10 in the lower die 6, to come into contact with the protective metal fitting 22 of the temperature sensor 2 . Such a contact between the molten metal 13 and the protective metal fitting 22 permits direct detection of the temperature of the molten metal 13 in part of the casting, namely, the runner 15 part, by the temperature sensor 2. Thus, the casting machine including the temperature sensor 2 can directly detect the temperature of the casting during the casting process, and therefore can complete the pressurization of the molten metal 13 or open the die in the timeliest manner in accordance with an actual solidification rate of the molten metal 13, thereby reducing the cycle time. [0042] Since the protective metal fitting 22 and the lower die 6 are made of the same material, the temperature sensor 2 has a refractoriness and strength as high as those of the die 1. This prevents the temperature sensor 2 from being broken due to heat or pressure of the molten metal 13. As well as using the same material for the protective metal fitting 22 and the die 1, the temperature detecting section 25 is formed with a draft angle or taper. The protective metal fitting 22 can therefore be easily removed together with the die 1 from the casting without wear and tear caused by the casting at the time of opening the die or separating the casting from the die, even though the molten metal 13 solidifies in contact with the protective metal fitting 22, forming the casting. [0043] The temperature sensor 2 of the first embodiment is attached to the lower die 6 and the temperature detecting section 25 of the protective metal fitting 22 faces inside the runner 9, in order to detect the temperature of the tip portion 25a of the temperature detecting section 25. The temperature Sensor 2 can thus detect the temperature of the molten metal 13 located in the runner 9, in other words, a temperature of the molten metal 13 nearest the product part 14. Thus, this ensures that no trace of the temperature sensor 2 remains on the product part, and the temperature of the casting is detected with high accuracy. In addition, in this embodiment, the temperature sensor 2 is provided at a position where the temperature detection section 25 faces the inside of the runner 9. It should be understood, however, that the position where 16 the temperature sensor according to the present invention is attached is not limited to the runner 9 but may be changed, for example, to the cavity 7, 8 or the sprue 10. [0044] (Second Embodiment) An embodiment of the present invention applied to a gravity casting machine is described in details with reference to FIGs. 6A, 6B through 9. FIGs. 6A and 6B, and 7A and 7B illustrate dies used for the gravity casting machine, in which FIGs. 6A and 7A are cross-sectional plan views and FIGs. 6B and 7B are vertical sectional views. FIG. 8 is a flowchart for the purpose of explaining the casting operation. FIG. 9 is a graph, illustrating how the molten metal temperature changes. A gravity casting die 41, as shown in FIGs. 6A and 6B, and 7A and 7B includes a first die 42 and a second die 43 formed so as to open in the horizontal direction, as well as cavities 44, 45 and risers 46, 47 above the cavities. The first die 42 and the second die 43 are mounted to a die drive unit (not shown) by which the dies are clamped and opened. [0045] In the die 41 shown in FIGs. 6A and 6B, the molten metal 13 is supplied from the risers 46, 47 into the cavities 44, 45. The die 41 shown in FIGs. 7A and 7B has a sprue 48 formed with an upward opening on the side of the risers 46, 47. A structure is employed in which the molten metal 13 is supplied from the sprue 48 through a runner 49 to the bottom of the cavities 44, 45. These dies 41 each have a temperature sensor 2 provided in the risers 46, 47. [0046] The temperature sensor 2 is an equivalent to what is used for the first embodiment, and mounted to the first die 42 with a temperature detecting section 25 protruding from the inner wall face of the riser 46 into the die in the die-opening direction. In other words, also in this case, the temperature sensor 2 is located at a position where the molten metal 13 17 solidifies later than at the cavities 44, 45. As is the case with the die 41 of FIGs. 7A and 7B, in which the sprue 48 and the runner 49 are used to supply the molten metal 13 to the bottom of the cavities 44, 45, the sprue 48 may be provided with the temperature sensor 2, as shown by a phantom line in FIG. 7B. [0047] The gravity casting machine with the die 41 configured as described above is controlled by a controller (not shown) in a manner shown in FIG. 8. To be more specific, the controller determines whether or not the current temperatures of the die 41 and the molten metal 13 fall within a range for producing non-defective products in the step PI in the flowchart of FIG. 8. The range for producing non-defective products refers to a temperature range within which the casting can be a non-defective product, which is predetermined for each die. If NO or the aforementioned temperatures fall out of the range for producing non-defective products, the process goes to the step P2 and performs an alarm process in which the controller gives an operator notice of the abnormal temperatures. This results in stopping the casting operations. [0048] If YES, the gravity casting machine uses a molten metal supply device (not shown) or the like to supply the molten metal 13 (pouring) to fill the die 41 (the step P3). At the pouring, the controller calculates the solidification time of the molten metal 13 which is essential for executing the casting program to be used in the case the temperature sensor 2 fails to function. At the same time, the timer starts. [0049] As mentioned above, after the supply of the molten metal 13 into the die 41, the controller uses the temperature sensor 2 to detect the temperature of the molten metal 13 in the risers 46, 47 or the sprue 48, as shown in the step P4 . The temperature detected with the temperature sensor 2 sharply increases after the casting process start (pouring start), then remains unchanged for a certain time period, and then gradually 18 decreases, as shown in FIG. 9. After that, the controller determines that the temperature sensor 2 works properly if the maximum temperature detected with the temperature sensor 2 falls within a predetermined temperature range in the step P5. In contrast, the controller determines that the temperature sensor 2 does not work properly (is in the abnormal condition) if the maximum temperature falls out of the predetermined temperature range. [0050] If it is determined that the temperature sensor 2 is in the abnormal condition in the step P5, the controller is in standby until the elapsed time indicated by the timer reaches the solidification time obtained in the step P3 (the step P6) and then sends a die-opening signal to the die drive unit. The die drive unit then receives the die-opening signal in this manner, which causes the die to open (the step P7). If YES in the step P5 or the temperature sensor 2 works properly, the controller uses the temperature sensor 2 to detect the temperature of the molten metal 13 in the step P8. [0051] The temperature detected with the temperature sensor 2 varies as shown in FIG. 9. After reaching the maximum temperature, it decreases as the molten metal 13 further solidifies. When the temperature detected with the temperature sensor 2 decreases to the predetermined temperature T3 (the step P9) , the controller uses the die drive unit to open the die (the step P7) . The temperature T3 is predetermined to be the maximum value at which the molten metal 13 solidifies enough not to have changed casting shape and dimension at die opening. In this way, the die is opened, which results in completion of one cycle of the casting work. The temperature detecting section 25 of the temperature sensor 2 can be easily removed from the casting when it is separated from the first die after the casting process, since the temperature detecting section 25 is formed with a draft angle or taper. [0052] 19 Thus, the gravity casting machine with the die 41 of the second embodiment uses the temperature sensor 2 to directly detect the temperature of the molten metal 13, and determines the timing to open the die based on this detected temperature. This ensures that the die 41 is opened in the timeliest manner in accordance with the conditions of the casting, even if there are variations in temperature of the die 41 at the start of the casting process. Therefore, there is no need to unnecessarily extend or shorten the solidification time for the molten metal 13, or the solidification time can be minimized to a period required for the casting to be a non-defective product. This further improves the productivity. Industrial Applicability [0053] The present invention can be applied to casing parts such as cylinder heads of vehicle engines, marine engines or other general-purpose engines. 20 Claims [1] A temperature sensor for a casting machine, which is made of the same material as a die, comprising: a protective metal fitting having a draft angle or taper along its top end; and a thermocouple inserted in the protective metal fitting to be connected to the top end thereof, wherein the top end of the protective metal fitting is mounted to the die so as to protrude into a casting space in the die. [2] The temperature sensor for a casting machine according to Claim 1, wherein the top end of the protective metal fitting protrudes from the inner wall face of the die into the casting space in a die-opening direction. [3] A casting machine comprising: the temperature sensor according to Claim 1; and a controller for controlling timing to stop supplying molten metal based on a temperature detected with the temperature sensor; wherein the temperature sensor is located at a position where the molten metal solidifies later than at a cavity of the die, and the top end of the protective metal fitting protrudes into the die from the inner wall face thereof in the die-opening direction. [4] A casting machine comprising: the temperature sensor according to Claim 1; and a controller for controlling timing to open the die based on a temperature detected with the temperature sensor; wherein the temperature sensor is located at a position where molten metal solidifies later than at a cavity of the die, and the top end of the protective metal fitting protrudes into the die from the inner wall face thereof in the l! 21 die-opening direction. The temperature sensor comprises a protective metal fitting 22 having a draft angle or taper along its top end. The protective metal fitting 22 is made of the same material as a die. The temperature sensor also comprises a thermocouple inserted in the protective metal fitting 22 to be connected to the top end thereof. The top end of the protective metal fitting 22 is mounted to the die so as to protrude into a casting space in the die.

Full Text

Specification
CASTING MACHINE AND TEMPERATURE SENSOR FOR THE SAME Field of the Invention [0001]
The present invention relates to a casting machine and a temperature sensor for the same used for directly detecting a molten metal temperature. Background Art
[0002]
Conventionally, a cylinder head for a motorcycle engine is made by a low pressure casting method, for example. JP-B-3201930 discloses this type of low pressure casting machine . The casting machine disclosed in this patent document has: a die including a lower and an upper die; and a crucible disposed below the die; and is designed to pressurize molten metal reserved in the crucible to force it up through a stalk to be supplied to a sprue of bhe lower die. [0003]
For the purpose of improvement in productivity, the operation processes of the casting machine from the start of molten metal supply to die opening are automated. To be more specific, after an operator turns a start switch on, the casting machine calculates the time period for which molten metal is supplied (hereinafter referred to as pressurization time) based on the die and molten metal temperatures, to pressurize the molten metal during this pressurization time and then supply it into the die. A temperature sensor embedded in the die detects the die temperature, while another temperature sensor provided in the crucible detects the molten metal temperature. The preset pressurization time is so long that the molten metal fills the die after the pressurization start and a solidifying region of the molten metal expands from the upper to lower parts of the die to reach inside of the sprue. [0004]
In other words, completing pressurization of the molten metal after the lapse of the pressurization time allows the unsolidified metal to flow from the sprue through the stalk to
1

drop back into the crucible. Only the solidified molten metal remains inside the sprue. Under this condition, the solidified casting in the die has no flowability but is still soft enough to be easily deformed if it is taken out of the die. This substantially decreases the die shape and dimension accuracies . Thus, this casting machine is designed to open the die after a standby period during which the casting becomes hard enough not to deform after pressurization of the molten metal is completed. A time period from the point in time at which pressurization of the molten metal is completed until the point in time at which the die is opened (hereinafter referred to as solidification time) is obtained by calculation based on the die temperature at the time when pressurization of the molten metal is completed. Disclosure of the invention Problem to be Solved by the Invention
[0005]
It has not been possible for a conventional type of casting machine configured as above to detect the temperature of the casting during the casting process, and therefore not possible to complete pressurization of the molten metal or open a die in the timeliest manner in accordance with an actual solidification rate of the molten metal. Thus, the conventional type of casting machine presets the pressurization and solidification times long enough to ensure that the pressurization and solidification of the molten metal are completely done . This leads to a longer cycle time and therefore to a decrease in productivity.
[0006]
These problems could be solved by using a temperature sensor to directly detect the temperature of the casting. In addition, such a temperature sensor should be manufactured so as to overcome other problems, including possible breakages of part of the temperature sensor, which is in contact with the casting, due to heat or a pressing force of the molten metal, and wear and tear caused by the casting at the time of opening
2

the die or separating the casting from the die.
[0007]
The present invention is made in view of the foregoing problems. A first object of the invention is to provide a temperature sensor for the casting machine, which can be prevented from breakages due to heat or a pressing force of the molten metal while being easily removed from the casting. A second object of the invention is to reduce a cycle time of the casting machine by using the temperature sensor. Means for Solving the Problem
[0008]
The present invention provides a temperature sensor for a casting machine, which is made of the same material as a die, including: a protective metal fitting having a draft angle or taper along its top end; and a thermocouple inserted in the protective metal fitting to be connected to the top end thereof, in which the top end of the protective metal fitting is mounted to the die so as to protrude into a casting space in the die. Effect of the Invention
[0009]
The protective metal fitting of the temperature sensor for a casting machine defined in Claims 1 and 2 has a refractoriness and strength as high as those of the die, and is removed together with the die from the casting. The present invention therefore provides a temperature sensor for a casting machine, which can be prevented from breakages due to heat or pressure of the molten metal, and be easily removed from the casting without wear and tear caused by the casting at the time of opening the die or separating the casting from the die.
[0010]
In the inventions of Claims 3 and 4, the temperature sensor is used to directly detect the temperature of the molten metal that solidifies later than at the cavity. This allows the molten metal supply to stop or the die to open when the temperature of the casting reaches an optimum temperature for stopping the molten metal supply or opening the die.
3

[0011]
As a result, in the casting machine according to the present invention, it is possible to reduce the supply time for the molten metal and the solidification time, from the stop of the molten metal supply to die-opening, to a period required for casting without any defective product as soon as possible. This therefore further improves the productivity with the reduced casting cycle time. In addition, the present invention allows detection of the temperature of the interior molten metal while allowing the protective metal fitting of the temperature sensor to be easily removed from the casting after the casting process . This makes it possible to prevent the protective metal fitting from being broken when the die is opened or the casting is separated from the die while detecting the temperature of the molten metal with high accuracy.
Brief Description of Drawings [0012]
FIG. 1A is a vertical sectional view of dies to which a temperature sensor of the present invention is mounted.
FIG. IB is a cross-sectional view of the dies to which the temperature sensor of the present invention is mounted.
FIG. 2 is an enlarged sectional view, showing the temperature sensor mounted to a lower die.
FIG. 3 is an enlarged sectional view of the temperature sensor.
FIG. 4 is a flowchart for the purpose of explaining the operation of a casting machine.
FIG. 5 is a graph, illustrating how a molten metal temperature changes in a runner.
FIG. 6A is a cross-sectional view of dies used for a gravity casting machine.
FIG. 6B is a vertical sectional view of the dies used for the gravity casting machine.
FIG. 7A is a cross-sectional view of the dies used for the gravity casting machine.
FIG. 7B is a vertical sectional view of the dies used for
4

the gravity casting machine.
FIG. 8 is a flowchart for the purpose of explaining the casting operation.
FIG. 9 is a graph, illustrating how a molten metal temperature changes.
Best Mode for Carrying Out the Invention [0013] (First Embodiment)
Now, an embodiment of this invention is described with reference to the drawings.
In FIG. 1A, FIG. IB through FIG. 5, reference numeral 1 denotes a die to which a temperature sensor 2 of the first embodiment is attached. The die 1 is mounted to a low-pressure casting machine (not shown) and includes an upper die 4 mounted to a platen of the casting machine by an upper support member 3 and a lower die 6 supported on a base of the casting machine through a lower support member 5. The casting machine is designed to drive the platen to move the upper die 4 up from/down to the lower die 6 respectively for die-opening/clamping. The metal used for casting by the die 1 is aluminum alloy. [0014]
The upper die 4 is formed with a cavity 7 having a downward opening. The lower die 6 is formed with a cavity 8 having an upward opening . In the first embodiment, the cavities 7, 8 refer to a recess for forming the product part of the casting.
The upper die 4 and the lower die 6 are provided with a heater (not shown) for preheating them to a temperature ready for casting and a water-cooling device (not shown) for maintaining the die temperature during the casting process. [0015]
As shown in FIGs. 1A, IB and 2, at the inner bottom of the lower die 6 is formed a runner 9 that extends from one side of the cavity 8 to the other. A sprue 10 is also formed at the inner bottom of the lower die 6 that extends downward from the bottom of the runner 21. The temperature sensor 2 of the present invention is so attached to face inside of the runner 9.
5

As shown in FIG. IB, the sprue 10 is formed at the bottom of the lower die 6 so as to have an elliptic shape when viewed from above, by drilling to create a draft angle such that an opening diameter of the sprue 10 becomes larger toward the top as shown in FIG. 2. [0016]
A filter 11 for preventing foreign materials from entering inside the die is attached to the opening at the upper end of the sprue 10. The bottom end of the sprue 10 is connected to the top end of a sprue cup 12 provided in the lower support member 5. The sprue cup 12 runs through the lower support member 5 in the vertical direction. The molten metal 13 is supplied from the top end of a stalk (not shown) which comes into contact with the bottom surface of the lower support member 5. [0017]
To be more specific, the bottom end of the stalk is dipped in the molten metal within a crucible (not shown) contained in a furnace (not shown). Pressurizing a surface of the molten metal 13 in the crucible during the casting process allows the molten metal 13 to flow from the stalk through the sprue 10 cup into the sprue 10. The molten metal 13 flows from the sprue 10 through the filter 11 into the runner 9 and then into the cavities 7, 8. The molten metal 13, filling the die 1 in this manner, starts solidifying within the cavities 7, 8 {a product part 14 (See FIG. 2)}. [0018]
A solidifying region of the molten metal 13 expands from the cavities 7, 8 into the runner 9, and then into the sprue 10 with the lapse of time. The casting machine of the first embodiment uses the temperature sensor 2, which will be described later, to directly detect the temperature of the molten metal 13 in part of the casting, namely, a runner part, after the start of pressurization of the molten metal 13 The solidification of the molten metal 13 can be detected based on the temperature of the molten metal 13, and the casting machine thus completes pressurization of the molten metal 13 when the
6

solidification of the molten metal 13 expands adjacent to a boarder between the sprue 10 and the runner 9. The pressurization of the molten metal 13 is completed in this manner, which causes the unsolidified metal in the sprue cup 12 or the stalk to drop into the crucible. The casting machine then opens the die when the temperature of the molten metal 13 (a casting) decreases to a certain level. [0019]
The temperature sensor 2, as shown in FIG. 3, includes a protective metal fitting 22, which includes: a protective portion 2a extending in the vertical direction; a support portion 2b formed, at the base end of the protective portion 2a, into one body together with the protective portion 2a; and a through hole 21 axially passing through the protective metal fitting 22. The temperature sensor 2 also includes a thermocouple 23 inserted in the through hole 21, and is fitted into a mounting hole 24 drilled in the lower die 12. As shown in FIG. 3, the mounting hole 24 consists of a small diameter portion 24a, having an opening in the runner 9, into which the protective portion 2a is fitted, and a large diameter portion 24b, having an opening directed outward of the die, into which the support portion 2b is fitted. The mounting hole 24 is drilled such that it extends through the lower die 6 in the die-opening direction (the vertical direction in FIG. 3) adjacent to the side of the sprue 10 in the lower die 6. [0020]
The support portion 2b fitted in the large diameter portion 24b limits a position of the protective metal fitting 21, which is mounted to the lower die 6, to a position where it cannot be inserted further inward of the die 1 from the position shown in the drawing. The protective metal fitting 22 and the lower die 6 are made of the same material. In the first embodiment, alloy tool^ steel (SKD) for hot dies is employed.
The length of the protective portion 2a of the protective metal fitting 22, which is fitted in the mounting hole 24 together with the support portion 2b, is so designed that a
7

temperature detecting section 25 or the top end of the protective metal fitting 22 protrudes into the runner 9.
In other words, the protective metal fitting 22 is mounted to the lower die 12, with the temperature detection section 25 protruding into a casting space (runner 9) in the die. The temperature detecting section 25 of the protective metal fitting
22 is formed, having an outside diameter gradually smaller
toward the top end. The casting space also includes regions
other than the runner 9, such as the cavities 7, 8 and the sprue
10 in the die 1, to be filled with the molten metal.
[0021]
In other words, the temperature detecting section 25 of the protective metal fitting 22 is formed with a draft angle or taper. The temperature detection section 25 defines the top end of the temperature sensor in the present invention. In the first embodiment, the temperature detecting section 25 has a dome-shaped tip portion 25a that is convex upward, to which each top end of two types of conductor 23a, 23b of the thermocouple
23 is welded. To be more specific, each top end of the conductors
23a, 23b passing the through hole 24 faces the opening of the
tip portion 25a, in order to be welded together to block the
opening using a welding electrode made of common material, alloy
tool steel (SKD) for hot dies. The welded opening is then ground
into a dome-shape. [0022]
The well-known, typical alumel-chromel thermocouple 23 is used. It includes the bwo types of conductor 23a, 23b which conduct each other by welding to the temperature detecting section 25 of the protective metal fitting 22. Providing the thermocouple 23 in this manner allows the temperature sensor 2 to detect the temperature of the molten metal 13 which comes into contact with the tip portion 25a (where the thermocouple 23 is welded) of the protective metal fitting 22 (protective portion 2a).
[0023]
The two conductors 23a, 23b running through the protective
8

metal fitting 22 to the support portion 2b are lead outside of the lower die 6. They are connected to a controller 31 (See FIG. 1A and IB) of the casting machine through the interior of a stainless duct 26 welded to the support portion 2b. In the temperature sensor 2 of the first embodiment, refractory insulating powder 27 is filled around the conductors 23a, 23b in the through hole 21. As the refractory insulating powder 27, there may be magnesia (MgO) used for a glow plug of diesel engines, for example. [0024]
The controller 31 is designed to control the operation of the casting machine having the aforementioned die 1, and includes a molten metal temperature controller, a die temperature controller, a pressurization pressure controller, and a casting condition setter.
The molten metal temperature controller controls the temperature of the heater of the furnace so as to heat the molten metal 13 in the crucible at a predetermined temperature. The casting condition setter, which will be described later, determines the temperature of the molten metal 13 for each die used.
[0025]
The die temperature controller controls the temperatures of the heater and the cooling device in the die 1 so as to heat the die 1 at a predetermined temperature. The casting condition setter determines the temperature of each die 1 used.
The pressurization pressure controller switches on/off a pressurization device (not shown) for pressurizing the molten metal 13 in the crucible, while controlling the amount of gas to be supplied from the pressurization device so as to make the feed rate of the molten metal 13 from the crucible into the die 1 equal to a predetermined rate. The casting condition setter determines the predetermined feed rate for each die used. [0026]
By the casting condition setter, data related to the casting conditions, such as the die and molten metal
9

temperatures, the pressurization and solidification times, and the feed rate of the molten metal 13, in accordance with each die used for the casting process, are sent to the molten metal temperature controller, the die temperature controller and the pressurization pressure controller. The casting condition setter also outputs start/stop signals for the pressurization pressure controller to start/stop pressurizing the molten metal 13 at the respective predetermined timings. The casting condition setter also outputs die-opening/clamping signals for the drive unit 13 to move the upper die 4 up/down respectively at the predetermined timings.
[0027]
Of these start/stop signals and die-clamping/opening signals, the stop and die-opening signals are sent when the temperature detected with the temperature sensor 2 reaches predetermined temperatures Tl, T2, respectively (See FIG. 5) . The temperature Tl is optimum for completing pressurization of the molten metal 13, and so predetermined that there is no flowability of the molten metal 13 in the product part, the runner part, and the upper part of the sprue due to the solidification therein while the flowability of the molten metal 13 remains on the stalk 9 side from the upper part of the sprue.
[0028]
In other words, the temperature Tl is predetermined to be the maximum value at which the molten metal 13 only on the stalk 13 side below the upper part of the sprue flows down toward the crucible side even if the pressurization device stops pressurization. As shown in FIG. 3, in the first embodiment, the temperature Tl is so predetermined that the upper portion of the filter 11 can remain in the casting. The temperature T2, lower than the temperature Tl, is optimum for opening the die, and predetermined to be the maximum value at which the molten metal 13 solidifies enough not to have changed casting shape and dimension at die opening.
[0029] The casting condition setter of the first embodiment is
10

designed to produce non-defective products even if it is impossible for the temperature sensor 2 to detect the temperatures Tl, T2 due to some malfunction. In other words, the casting condition setter is designed to determine the timings to complete the pressurization of the molten metal 13 and to open the die based on the times (pressurization and solidification times), instead of the temperature detected by the temperature sensor 2, for failure of the temperature sensor 2. To be more detailed, the casting condition setter is designed to complete the pressurization of the molten metal 13 when the predetermined pressurization time has elapsed since the start of the pressurization of the molten metal 13 in the case that the temperature sensor 2 is a defective product or has some malfunction. The casting condition setter is also designed to open the die when the predetermined solidification time has elapsed since the completion of the pressurization of the molten metal 13.
[0030]
The pressurization time refers to a time period from the point in time when a supply of the molten metal 13 starts to the point in time when a solidifying region of the molten metal 13 expands to the sprue 10 . This pressurization time is obtained by calculation, in accordance with the type of die 1 used, based on the temperature of the die 1 at the start of supplying the molten metal 13, and the temperature of the molten metal 13 in the crucible. The solidification time refers to a period required for the casting inside of the die 1 to solidify enough ,not to easily deform after the completion of the pressurization of the molten metal 13. This solidification time is obtained by calculation, depending on the type of die 1, based on the temperature of the die 1 at the completion of the pressurization of the molten metal 13. These pressurization and solidification times may be stored in a memory (not shown) as a map in advance and read from the memory as needed. [0031]
The aforementioned operation of the casting machine is
11

next described in conjunction with the further detailed configuration of the controller 31 with reference to FIGs. 4 and 5. Here, only one operation cycle (one shot) of the casting work, which is repeatedly performed, is described. It is therefore assumed that the casting conditions for each die 1 have already been inputted in the casting condition setter, and the temperatures of the die 1 and molten metal 13 have already reached the targeted casting temperature. Inputs of the casting conditions are achieved by inputting a predetermined number given to an execution program for each die 1. [0032]
The casting work of the casting machine with the die 1 clamped is started by, for example, turning the start switch (not shown) ON. When the start switch is turned ON, the casting condition setter first determines whether or not the current temperatures of the die 1 and the molten metal 13 fall within a range for producing non-defective products, as shown in the step Si of FIG. 4. The range for producing non-defective products refers to a temperature range within which the casting can be a non-defective product, which is predetermined for each die. If NO or the aforementioned temperatures fall out of the range for producing non-defective products, the process goes to the step S2 and performs an alarm process in which the casting condition setter gives an operator notice of the abnormal temperatures . This results in stopping the casting operations . [0033]
If YES, the casting condition setter calculates the pressurization time of the molten metal 13 (the step S3) which is essential for executing the casting program to be used in the case the temperature sensor 2 fails to function. The casting condition setter then sends the start signal to the pressurization pressure controller together with the data for the feed rate of the molten metal 13 in the step S4. The start signal sent to the pressurization pressure controller in this manner causes the pressurization device to supply inert gas into the furnace.
12

[0034]
As a result, the pressurized molten metal 13 is supplied from the stalk through the sprue cup 12, the sprue 10 and the filter 11 into the die 1. Part of the molten metal 13 filling the cavities 7, 8 first solidifies in the product part 14 within the cavities 7, 8. A solidifying region of the molten metal 13 expands from the runner 9 down to the sprue 10 with the lapse of time. In addition, when the pressurization device starts the pressurization as described above, a timer (not shown) also starts simultaneously.
[0035]
After that, the casting condition setter uses the temperature sensor 2 in the lower die 6 to detect the temperature of the molten metal 13 in the runner 9 in the step S5. As shown in FIG. 5, the temperature detected with the temperature sensor 2 sharply increases after the start of casting (after the start of supplying the molten metal 13) , then remains unchanged (with the molten metal 13 flowing in the runner 9) for a certain period of time, and then gradually decreases. In the step S6, the casting condition setter compares the maximum temperature detected with the temperature sensor 2 with a predetermined temperature range. If the maximum temperature falls within the predetermined temperature range, the casting condition setter determines that the temperature sensor 2 works properly. In contrast, if the maximum temperature falls out of the predetermined temperature range, it determines that the temperature sensor 2 does not work properly (is in an abnormal condition).
[0036]
In the case it is determined that the temperature sensor 2 is in an abnormal condition in the step S6, when the elapsed time indicated by the timer reaches the pressurization time obtained in the step S3, the casting condition setter sends the stop signal to the pressurization pressure controller. Then the pressurization pressure controller receives the stop signal, which causes the pressurization device to stop the inert gas
13

supply, thereby completing the pressurization of the molten metal 13 (the step S7). Approximately at the same time when the supply of the molten metal 13 is stopped, the casting condition setter calculates the solidification time based on the current temperature of the die 1 (the step S8).
[0037]
After the stop of supplying the molten metal 13 in the step S7, the unsolidified metal 13 in the die flows from the sprue 10 through the sprue cup 12 and the stalk to drop back into the crucible. The molten metal 13 remaining in the die 1 (with no flowability) further solidifies with increased hardness as the result of no heat supply (the step S9) . When the pressurization of the molten metal 13 is completed, the timer (not shown) starts. Then, the casting condition setter sends the die-opening signal to the drive unit 13 after the time indicated by the timer reaches the solidification time. Then the drive unit 13 receives the die-opening signal, which causes the upper die 4 to move up to open the die (the step 10 to the step 11).
[0038]
If YES in the step S6 or it is determined that the temperature sensor 2 works properly, the casting condition setter uses the temperature sensor 2 to detect the temperature of the molten metal 13 in the runner 9 in the step S12. The temperature detected with the temperature sensor 2 varies as shown in FIG. 5. After reaching the maximum temperature, it gradually decreases as the molten metal 13 further solidifies. The casting condition setter sends the stop signal to the pressurization pressure controller when the temperature detected with the temperature sensor 2 decreases to the predetermined temperature Tl (the step S13) . Then the pressurization pressure controller receives the stop signal, which causes the pressurization device to stop the inert gas supply, thereby completing the pressurization of the molten metal 13 (the step S14).
[0039] When the pressurization of the molten metal 13 is completed,
14

the unsolidified metal 13 drops back into the crucible while the molten metal 13 having no flowability remains in the die 1. This remaining molten metal 13 further solidifies since its temperature further decreases as the result of no heat supply. The casting condition setter uses the temperature sensor 2 to constantly detect the temperature of the molten metal 13 in the runner part as shown in the steps S15, S16. When the temperature of the molten metal 13 detected with the temperature sensor 2 decreases to the predetermined temperature T2, the casting condition setter determines the completion of the solidification and sends the die-opening signal to the drive unit 13.
[0040]
The drive unit 13 receives the die-opening signal in this manner, which causes the upper die 4 to move up to open the die (the step Sll). One cycle of the casting work ends. At the die-opening, in either case that the casting moves up with the upper die 4, or the casting remains in the lower die 6, the temperature detecting section 25 of the temperature sensor 2 can be easily removed from the casting when it is separated from the lower die 6. This is because the temperature detecting section 25 of the temperature sensor 2 is formed with a draft angle or taper. As described above, the protective metal fitting 22 including the temperature detecting section 25 and the thermocouple welding part are made of the same material as the die, providing excellent wear resistance. This therefore prevents them from being worn out by castings.
[0041]
Thus, the low-pressure casting machine configured as above performs casting, using the temperature sensor 2 attached to the die 1, which allows the molten metal 13, flowing into the runner 9 from the sprue 10 in the lower die 6, to come into contact with the protective metal fitting 22 of the temperature sensor 2 . Such a contact between the molten metal 13 and the protective metal fitting 22 permits direct detection of the temperature of the molten metal 13 in part of the casting, namely, the runner
15

part, by the temperature sensor 2.
Thus, the casting machine including the temperature sensor 2 can directly detect the temperature of the casting during the casting process, and therefore can complete the pressurization of the molten metal 13 or open the die in the timeliest manner in accordance with an actual solidification rate of the molten metal 13, thereby reducing the cycle time. [0042]
Since the protective metal fitting 22 and the lower die 6 are made of the same material, the temperature sensor 2 has a refractoriness and strength as high as those of the die 1. This prevents the temperature sensor 2 from being broken due to heat or pressure of the molten metal 13. As well as using the same material for the protective metal fitting 22 and the die 1, the temperature detecting section 25 is formed with a draft angle or taper. The protective metal fitting 22 can therefore be easily removed together with the die 1 from the casting without wear and tear caused by the casting at the time of opening the die or separating the casting from the die, even though the molten metal 13 solidifies in contact with the protective metal fitting 22, forming the casting. [0043]
The temperature sensor 2 of the first embodiment is attached to the lower die 6 and the temperature detecting section 25 of the protective metal fitting 22 faces inside the runner 9, in order to detect the temperature of the tip portion 25a of the temperature detecting section 25. The temperature Sensor 2 can thus detect the temperature of the molten metal 13 located in the runner 9, in other words, a temperature of the molten metal 13 nearest the product part 14. Thus, this ensures that no trace of the temperature sensor 2 remains on the product part, and the temperature of the casting is detected with high accuracy. In addition, in this embodiment, the temperature sensor 2 is provided at a position where the temperature detection section 25 faces the inside of the runner 9. It should be understood, however, that the position where
16

the temperature sensor according to the present invention is attached is not limited to the runner 9 but may be changed, for example, to the cavity 7, 8 or the sprue 10. [0044] (Second Embodiment)
An embodiment of the present invention applied to a gravity casting machine is described in details with reference to FIGs. 6A, 6B through 9.
FIGs. 6A and 6B, and 7A and 7B illustrate dies used for the gravity casting machine, in which FIGs. 6A and 7A are cross-sectional plan views and FIGs. 6B and 7B are vertical sectional views. FIG. 8 is a flowchart for the purpose of explaining the casting operation. FIG. 9 is a graph, illustrating how the molten metal temperature changes.
A gravity casting die 41, as shown in FIGs. 6A and 6B, and 7A and 7B includes a first die 42 and a second die 43 formed so as to open in the horizontal direction, as well as cavities
44, 45 and risers 46, 47 above the cavities. The first die 42
and the second die 43 are mounted to a die drive unit (not shown)
by which the dies are clamped and opened.
[0045]
In the die 41 shown in FIGs. 6A and 6B, the molten metal 13 is supplied from the risers 46, 47 into the cavities 44, 45. The die 41 shown in FIGs. 7A and 7B has a sprue 48 formed with an upward opening on the side of the risers 46, 47. A structure is employed in which the molten metal 13 is supplied from the sprue 48 through a runner 49 to the bottom of the cavities 44,
45. These dies 41 each have a temperature sensor 2 provided
in the risers 46, 47.
[0046]
The temperature sensor 2 is an equivalent to what is used for the first embodiment, and mounted to the first die 42 with a temperature detecting section 25 protruding from the inner wall face of the riser 46 into the die in the die-opening direction. In other words, also in this case, the temperature sensor 2 is located at a position where the molten metal 13
17

solidifies later than at the cavities 44, 45. As is the case with the die 41 of FIGs. 7A and 7B, in which the sprue 48 and the runner 49 are used to supply the molten metal 13 to the bottom of the cavities 44, 45, the sprue 48 may be provided with the temperature sensor 2, as shown by a phantom line in FIG. 7B.
[0047]
The gravity casting machine with the die 41 configured as described above is controlled by a controller (not shown) in a manner shown in FIG. 8. To be more specific, the controller determines whether or not the current temperatures of the die 41 and the molten metal 13 fall within a range for producing non-defective products in the step PI in the flowchart of FIG. 8. The range for producing non-defective products refers to a temperature range within which the casting can be a non-defective product, which is predetermined for each die. If NO or the aforementioned temperatures fall out of the range for producing non-defective products, the process goes to the step P2 and performs an alarm process in which the controller gives an operator notice of the abnormal temperatures. This results in stopping the casting operations.
[0048]
If YES, the gravity casting machine uses a molten metal supply device (not shown) or the like to supply the molten metal 13 (pouring) to fill the die 41 (the step P3). At the pouring, the controller calculates the solidification time of the molten metal 13 which is essential for executing the casting program to be used in the case the temperature sensor 2 fails to function. At the same time, the timer starts.
[0049]
As mentioned above, after the supply of the molten metal 13 into the die 41, the controller uses the temperature sensor 2 to detect the temperature of the molten metal 13 in the risers 46, 47 or the sprue 48, as shown in the step P4 . The temperature detected with the temperature sensor 2 sharply increases after the casting process start (pouring start), then remains unchanged for a certain time period, and then gradually
18

decreases, as shown in FIG. 9. After that, the controller determines that the temperature sensor 2 works properly if the maximum temperature detected with the temperature sensor 2 falls within a predetermined temperature range in the step P5. In contrast, the controller determines that the temperature sensor 2 does not work properly (is in the abnormal condition) if the maximum temperature falls out of the predetermined temperature range.
[0050]
If it is determined that the temperature sensor 2 is in the abnormal condition in the step P5, the controller is in standby until the elapsed time indicated by the timer reaches the solidification time obtained in the step P3 (the step P6) and then sends a die-opening signal to the die drive unit. The die drive unit then receives the die-opening signal in this manner, which causes the die to open (the step P7).
If YES in the step P5 or the temperature sensor 2 works properly, the controller uses the temperature sensor 2 to detect the temperature of the molten metal 13 in the step P8. [0051]
The temperature detected with the temperature sensor 2 varies as shown in FIG. 9. After reaching the maximum temperature, it decreases as the molten metal 13 further solidifies. When the temperature detected with the temperature sensor 2 decreases to the predetermined temperature T3 (the step P9) , the controller uses the die drive unit to open the die (the step P7) . The temperature T3 is predetermined to be the maximum value at which the molten metal 13 solidifies enough not to have changed casting shape and dimension at die opening. In this way, the die is opened, which results in completion of one cycle of the casting work. The temperature detecting section 25 of the temperature sensor 2 can be easily removed from the casting when it is separated from the first die after the casting process, since the temperature detecting section 25 is formed with a draft angle or taper.
[0052]
19

Thus, the gravity casting machine with the die 41 of the second embodiment uses the temperature sensor 2 to directly detect the temperature of the molten metal 13, and determines the timing to open the die based on this detected temperature. This ensures that the die 41 is opened in the timeliest manner in accordance with the conditions of the casting, even if there are variations in temperature of the die 41 at the start of the casting process.
Therefore, there is no need to unnecessarily extend or shorten the solidification time for the molten metal 13, or the solidification time can be minimized to a period required for the casting to be a non-defective product. This further improves the productivity. Industrial Applicability [0053]
The present invention can be applied to casing parts such as cylinder heads of vehicle engines, marine engines or other general-purpose engines.
20

Claims
[1] A temperature sensor for a casting machine, which is made of the same material as a die, comprising: a protective metal fitting having a draft angle or taper along its top end; and a thermocouple inserted in the protective metal fitting to be connected to the top end thereof, wherein the top end of the protective metal fitting is mounted to the die so as to protrude into a casting space in the die.
[2] The temperature sensor for a casting machine according to Claim 1, wherein the top end of the protective metal fitting protrudes from the inner wall face of the die into the casting space in a die-opening direction.
[3] A casting machine comprising: the temperature sensor according to Claim 1; and a controller for controlling timing to stop supplying molten metal based on a temperature detected with the temperature sensor; wherein the temperature sensor is located at a position where the molten metal solidifies later than at a cavity of the die, and the top end of the protective metal fitting protrudes into the die from the inner wall face thereof in the die-opening direction.
[4] A casting machine comprising: the temperature sensor according to Claim 1; and a controller for controlling timing to open the die based on a temperature detected with the temperature sensor; wherein the temperature sensor is located at a position where molten metal solidifies later than at a cavity of the die, and the top end of the protective metal fitting protrudes into the die from the inner wall face thereof in the
l!
21
die-opening direction.

The temperature sensor comprises a protective metal fitting 22 having a draft angle or taper along its top end. The protective metal fitting 22 is made of the same material as a die. The temperature sensor also comprises a thermocouple inserted in the protective metal fitting 22 to be connected to the top end thereof. The top end of the protective metal fitting 22 is mounted to the die so as to protrude into a casting space in the die.

Documents:

01949-kolnp-2006-abstract.pdf

01949-kolnp-2006-assignment.pdf

01949-kolnp-2006-claims.pdf

01949-kolnp-2006-correspondence others-1.1.pdf

01949-kolnp-2006-correspondence others.pdf

01949-kolnp-2006-correspondence-1.2.pdf

01949-kolnp-2006-description (complete).pdf

01949-kolnp-2006-drawings.pdf

01949-kolnp-2006-form-1.pdf

01949-kolnp-2006-form-18.pdf

01949-kolnp-2006-form-2.pdf

01949-kolnp-2006-form-3.pdf

01949-kolnp-2006-form-5.pdf

01949-kolnp-2006-international publication.pdf

01949-kolnp-2006-priority document.pdf

1949-KOLNP-2006-(19-04-2012)-PETITION UNDER RULE 137.pdf

1949-KOLNP-2006-(23-12-2011)-ABSTRACT.pdf

1949-KOLNP-2006-(23-12-2011)-AMANDED CLAIMS.pdf

1949-KOLNP-2006-(23-12-2011)-DESCRIPTION (COMPLETE).pdf

1949-KOLNP-2006-(23-12-2011)-DRAWINGS.pdf

1949-KOLNP-2006-(23-12-2011)-EXAMINATION REPORT REPLY RECIEVED.pdf

1949-KOLNP-2006-(23-12-2011)-FORM-1.pdf

1949-KOLNP-2006-(23-12-2011)-FORM-2.pdf

1949-KOLNP-2006-(23-12-2011)-FORM-3.pdf

1949-KOLNP-2006-(23-12-2011)-FORM-5.pdf

1949-KOLNP-2006-(23-12-2011)-OTHER PCT FORM.pdf

1949-KOLNP-2006-(23-12-2011)-OTHERS.pdf

1949-KOLNP-2006-CORRESPONDENCE 1.1.pdf

1949-KOLNP-2006-TRANSLATED COPY OF PRIORITY DOCUMENT.pdf

abstract-01949-kolnp-2006.jpg

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Patent Number

254383

Indian Patent Application Number

1949/KOLNP/2006

PG Journal Number

44/2012

Publication Date

02-Nov-2012

Grant Date

30-Oct-2012

Date of Filing

12-Jul-2006

Name of Patentee

YAMAHA HATSUDOKI KABUSHIKI KAISHA

Applicant Address

2500 SHINGAI, IWATA-SHI SHIZUOKA 4388501

Inventors:

#	Inventor's Name	Inventor's Address
1	TAKASHI ODA	c/o.YAMAHA HATSUDOKI KABUSHIKI KAISHA 2500 SHINGAI, IWATA-SHI, SHIZUOKA 4388501
2	HIROSHI YOSHII	C/o. YAMAHA HATSUDOKI KABUSHIKI KAISHA 2500 SHINGAI, IWATA-SHI SHIZUOKA 4388501

PCT International Classification Number

G01K1/08; B22D2/00

PCT International Application Number

PCT/JP 05/000685

PCT International Filing date

2005-01-20

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	2004-012880	2004-01-21	Japan