JPH0275185A - Three-terminal overheat preventing unit and heater control circuit using same - Google Patents

Abstract

PURPOSE:To surely obtain the protective function with a simple structure, improve productivity, and reduce the cost by providing a short-circuiting movable armature bridging two fixed terminals on a bar-shaped center terminal, separating it via thermal deformation at the time of an abnormality, and simultaneously turning off heaters of three phases. CONSTITUTION:An overheat preventing unit 20 is provided at the connection section of heaters 3 connected to a three-phase AC power source 2 and star- connected for use. Two fixed terminals 25 connected to heaters of two phases, a short-circuiting movable armature 28 ordinarily bridging them and a bar- shaped center terminal 26 connected to a heater of the remaining phase are stored in the outer case 24 of the preventing unit 20. When heater excitation is abnormal, the armature 28 is deformed by the heat and separated from the terminals 25 and simultaneously opens all heaters of three phases. Three heaters are opened by one preventing unit 20, which has high reliability as a protective device, winding is easy, work processes are reduced, and the cost can be reduced.

Description

[Detailed Description of the Invention] (a) Industrial Application Field The present invention is applicable to a number of applications such as refrigerating showcases, defrosting heaters for freezers, heating heaters for cooking heating equipment such as griddles and fryers, etc. In large commercial equipment that uses 3-phase AC power supplies, if an abnormal situation occurs where these heaters are left energized, immediately turn off the power to the heaters. The present invention relates to the structure of an overheat protector that prevents abnormal temperature rise inside a product, and a heater control circuit using the same.

(B) Prior Art Today, various types of commercial equipment, such as refrigerated showcases, freezers, and heating equipment for cooking such as griddles and fryers, are becoming more multifunctional and larger. Against this background, there are an increasing number of products that use three-phase AC 200mm power supplies, which can efficiently use high output and have low electricity bills, and this trend is expected to increase in the future. .

By the way, many heaters, especially sheath type heaters, are used in these refrigerated showcases and freezers, such as defrosting heaters, and griddles and fryers, such as heating heaters. These heaters are connected to a 3-phase AC power supply and perform their respective functions, but since heaters are heat-generating components, if the control circuit fails, the heaters may be turned off without electricity, causing the temperature inside the product to rise. In preparation for the unlikely event that the temperature rises abnormally, an overheating preventer is usually provided that immediately detects abnormal heat generation in the heater and shuts off the heater circuit. This protects the product. The specific way to set up this overheating preventer is as shown in the basic circuit diagram in Figure 8, in the case of a heater that is connected to a three-phase power supply and is star-connected. An overheat protector], 1 can be provided on the two phases of the refrigerator, and it can be applied to the refrigerator control circuit as shown in the electric circuit diagram of Figure 9, or another embodiment method can be applied to the refrigerator's electric circuit diagram of Figure 10. As shown in the circuit diagram, an overheat protector 1 is provided in the excitation circuit of an auxiliary relay 10 that turns on and off the heater. In Figure 8, 2 is a three-phase AC 200V power supply, 3.3.3 is star-connected, and 3.
These are heaters for each phase connected to a phase alternating current power source 2, and 4 indicates a star connection portion thereof. Further, in FIGS. 9 and 10, 5 is a compressor motor, 6 is a condensing fan motor, 7 is a cooling fan motor, and 8 is a defrost timer. This defrost timer 8
After the compressor motor 5 has been operated for cooling for a certain period of time, the timer is activated and the timer contact 9 is switched from contact A to contact I to form an excitation circuit from the defrost 1 to the heater magnet switch 10. do. This defrost heater magnet switch 10 corresponds to the above-mentioned auxiliary relay, and by forming the excitation circuit of this defrost heater magnet switch 10, each phase of the defrost l-heaters 11, 11, 11 which are star-connected is connected. The inserted common operating contact 12 is closed, the heater is energized, and the defrost operation continues until the defrost return thermometer (not shown) detects a temperature rise around the cooler near the end of defrosting. I do. Meanwhile, in parallel with this, by switching the timer contact piece 9, the compressor magnet switch 1
3 is cut off, its operating contact 14, which had been closed until now, is opened, and the compressor motor 5 is turned off during the defrosting period.
Stop. Further, another operating contact piece 15 of the defrost magnet switch 10 is opened, and the cooling fan motor 7 is also stopped. 16 and 17 are overload relays, 18 are thermostats, and 1 is an overheat protector for the defrost heater. Here, the overheating preventer 1 is inserted in series with two phases of the defrost heater circuit in FIG. 9, and is inserted in series with the defrost magnet switch 10 in FIG. Therefore, if there is a failure in the defrost timer 8, etc., there is no closing button on the side where the timer contact piece 9 makes contact.
Defrost 1-Heater 11. ], 1.11 When an abnormal situation of long-term energization occurs, this overheating preventer 1 is equipped with a bimetallic movable contact piece that senses the abnormal heat generation of the heater and operates to open the heater. The structure is As a result, the defrost heater 11°11.11 is shut off, and the temperature inside the product is prevented from rising.

(c) Problems to be solved by the invention However, as mentioned above, when the overheat protector is provided for two phases, the installation method becomes complicated, there are many connection points, and there are many wiring lead wires, which requires a lot of man-hours. increases and productivity is poor. Furthermore, since there are two phases, it is possible that only one of the two phases operates due to variations in the operating temperature characteristics of each phase, resulting in poor reliability. On the other hand, even if the overheat protector is installed in the excitation circuit of the auxiliary relay, even if the overheat protector operates normally, if the auxiliary relay (defrost 1 - heater magnet switch 10) is malfunctioning, the heater will not turn off and it will not function as a safety device. without fulfilling the
Lacking reliability.

The present invention was made in view of the above-mentioned problems.
In the protection circuit for heaters that are connected to a phase AC power supply and used in star connection, one overheat protector can directly cut off three phase heaters at the same time, ensuring that the protection function is achieved, and the structure is The object of the present invention is to provide a three-terminal overheat protector that is simple, highly productive, and inexpensive, and a heater control circuit that can exhibit a highly reliable safety protection function using this overheat protector.

(d) Means for Solving the Problems The three-terminal overheat protector of the present invention has two fixed terminals connected to a two-phase heater, and a short-circuit movable contact piece at the end that constantly bridges these fixed terminals. and has a rod-shaped central terminal connected to the remaining I-phase heater in a sealed structure inside the outer case, and the short-circuiting movable contact piece is thermally deformed by the heat when the heater is abnormally energized. It separates the fixed terminals and simultaneously opens all three-phase heaters that were star-connected. In addition, this three-terminal overheat protector and three sheathed heaters, each of which was made into a semi-finished product, were installed, and the three terminals protruding from the fixed terminal and center terminal of the overheat protector were installed. The lead wires are connected to the respective electrode terminals of each of the sheathed heaters, and the connection parts are sealed and molded to star-connect the sheathed heaters. In the event of an abnormality in heater power supply, the overheating preventer shuts off the heater circuit. A heater control circuit is formed to shut off the heater.

(e) By installing an overheating preventer in the star connection part of the heater that opens all three circuits at the same time, the temperature of the surface of the reheater and its surroundings will rise abnormally if the heater control circuit breaks down and the heater is continuously energized. However, the overheating preventer of the present invention detects abnormal heat generation and simultaneously cuts off power to all three-phase heaters, thereby preventing accidents such as product fires, resulting short-circuits, electric shocks, and thermal deformation of the product. . In addition, a single overheating preventer can reliably cut off power to the heater, increasing its reliability as a protection device. To connect the heaters, simply connect one end of each heater to the three lead wires coming out of the overheat protector, and then mold the heaters to make a star connection, reducing the number of connection points and making work easier. It also reduces man-hours and makes installation easier.

(f) Example Embodiments of the present invention will be described below with reference to the drawings.

Figure 1 is a basic circuit diagram of a heater control circuit using the overheat preventer according to the present invention, Figure 2 is an overall electrical circuit diagram using this overheat preventer in a defrosting heater circuit of a refrigerator, and Figure 3 4 is a sectional view of a specific structure of this overheat protector, FIG. 4 is a plan view thereof, and FIG. 5 is an electric circuit diagram thereof. In each figure, the same components as in FIGS. 9 and 10, which are electrical circuit diagrams of a refrigerator using a conventional desuperheater, are designated by the same numbers.

Reference numeral 20 denotes an overheat preventer provided at the connection portion where the three-phase heater 3 and the three-phase defrosting heater 11 are star-connected.

As shown in FIG. 3, this overheating preventer 20 is made up of an outer case consisting of a bottomed cylindrical body 22 made of synthetic resin having an internal circular cavity 21, and a circular cover 23 that seals the opening of this cavity. 24, and at the bottom of the space 21, first attach two fixed terminals 2.
5 and 25 are arranged opposite to each other, and the bottomed cylindrical body 22 is penetrated and protruded, and the exposed outer ends 25' and 25' are connected to any one of the three-phase defrosting heaters 11, 1.1.11. Two-phase defrosting heater 1. ], , 11.

Further, a rod-shaped central terminal 26 is erected at the center of the bottomed cylindrical body 22, and at its end projecting into the circular space 21, there is a contact point 27.27 that comes into contact with the fixed terminal 25.25. A short-circuiting movable contact piece 28 is usually attached to each end of the short-circuiting movable contact piece 28, which bridges both fixed terminals 25 and 25. A screw is cut in the head of the central terminal 26 that protrudes outside the bottomed cylindrical body 22, and a terminal piece 29 for connection with the remaining one-phase defrosting heater 11 is provided.
is fastened with a fixing screw 30.

Therefore, this central terminal 26 also serves as a terminal for connection with the defrosting heater 1], and these two fixed terminals 25°25
The electrical circuit diagram normally formed by the central terminal 26 and the short-circuiting movable contact piece 28 is as shown in FIG.
Defrosting heater connected to 5.26 11. ,11,
11 is in a star connection state. By the way, the short-circuiting movable contact piece 28 is a bimetallic plate that deforms and warps due to heat, and is used in the defrosting heater 1. ] , 1.1 , 1.
If 1 is energized for a long time, the heat from the heater will cause the recess 21 to
When the internal atmospheric temperature rises to about 45 degrees, terminal 2
5, the contact points 27 and 27 are bent and deformed to be separated from each other. The contact piece 28 has an operating temperature characteristic such that it is short-circuited at a temperature of about 30 degrees. In this way, the star connection state of the three-phase defrosting heaters 11, 11.11 is released, and the three phases are opened simultaneously. Therefore, as can be understood from the electrical circuit diagram of FIG. 2 using the present overheating preventer 20, an abnormal temperature rise that would result in the heater not being energized due to an unexpected failure of the defrost timer 8 or the defrost heater magnet switch 10 is possible. When the abnormal temperature is detected, the defrosting heater 11. , 11.

11 is directly turned off to protect the product. FIG. 6 shows a desuperheater 30 whose external shape is different from that shown in FIG. 1 piece 1
Three sheathed heaters 11 that are considered to be semi-finished products
, 11 and 11, and as shown in the same figure, two fixed wires 31, 29, 29 are soldered internally and come out from two fixed terminals (not shown), respectively. 3] and one lead wire 31 coming out from a central terminal (not shown), a total of three lead wires come out from the overheating protector 30, while the sheathed heaters 1.1, 1.1. , ], each of 1 -
Connect the electrode terminal at the end to the lead wire 3 ], , 3 ], ,
3] and mold the connected portion 32, 32, 32 so as to seal it.

In this way, the three-phase sheathed defrosting heater 11, 1
．． 1.

The overheat protector 30 can be easily assembled integrally with the star connection portion of [1]. Therefore, as shown in FIG. 11, a simple three-phase defrosting heater 11, ]-1, ], ]
The structure is significantly different from the conventional one, in which one end is tied together and star-connected.In this conventional one, the overheat protector must be placed on two of the three phases to ensure the safety of the heater. It has no choice but to have a complicated configuration that cannot provide any protective effect.

FIG. 7 shows the sheath type heater with overheating preventer shown in FIG.
4, the end opposite to the overheat protector 30 side is also molded 34, 34, 34, and lead wires are connected to other parts.

In this way, seeds 1. ], , ], 1. ,
1) An overheat protector is integrated into the star connection,
Since the heater control circuit is formed, the number of component parts and associated wiring connections and wiring processing points are reduced, improving workability and productivity, and one overheating preventer 20 can reliably turn off the heater. This increases the reliability of the protection device.

(G) Effects of the Invention As described above, according to the three-terminal overheat protector of the present invention, the fixed terminal for connecting the two-phase heater and the rod-shaped central terminal for connecting the remaining one-phase heater are housed inside the outer case. Equipped with a sealed structure,
A short-circuiting movable contact piece attached to the end of this central terminal normally bridges both terminals to form a star connection for the heater, and in the event of an abnormality in which the heater is energized for a long time, it thermally deforms and separates from both terminals in a bimetallic manner. Since all heaters are turned off directly, the protective function can be reliably performed. Also, when connecting to a 3-phase heater, use one overheat protector, connect the heater to the three lead wires coming out of it, and simply mold them, and the overheat protector will connect to the heater. A heater control circuit that can directly cut three phases at the same time can be easily created.

And since it does not have a conventional configuration in which two overheat protectors are placed in each two-phase heater circuit, it is easy to install and connect.
This provides effects such as easier wiring processing and improved productivity.

[Brief explanation of the drawing]

Figure 1 is a basic circuit diagram of a heater control circuit using the 3-terminal overheat protector of the present invention, Figure 2 is an overall electrical circuit diagram of a refrigerator in which the overheat protector of the present invention is applied to a defrosting heater circuit, and Figure 3 The figure is a sectional view of the overheat protector, Figure 4 is its plan view, Figure 5 is an electrical circuit diagram of its contact mechanism, and Figure 6 (a) is the relationship between the overheat protector and the sheathed heater connected to it. Plan view, Fig. 6(b) is a plan view of the overheating preventer showing the connection point of the sheathed heater, and Fig. 7 is a cooling unit with the defrosting heater assembled with the overheating preventer attached to the star connection part. Figure 8 is a basic circuit diagram of a conventional refrigerator in which a two-phase heater circuit is provided with an overheat protector, and Figure 9 is a diagram of a refrigerator in which a two-phase heater circuit is provided with an overheat protector. Figure 10 is a conventional overall electrical circuit diagram of a refrigerator in which an overheat protector is installed in the auxiliary relay circuit that controls energization of the heater circuit, and Figure 11 is a diagram of a three-phase sheathed heater that is simply started. FIG. 2 is a wiring plan view of a conventional sheathed heater in which wiring is connected, and a plan view of an overheat protector with exposed wiring parts. 1... Overheat protector, 2... 3-phase AC power supply, 3...
Heater, 11...defrosting heater (sheathed heater)
, 20.30・3-terminal overheat protector, 26・center terminal, 28・short-circuit movable contact piece, 31・lead wire, 32・
・Mold forming part. -1-1 J≧

Claims (2)

[Claims] (1) Two fixed terminals that are connected to two of the three-phase star-connected heaters, and a rod-shaped center that stands between these fixed terminals and is connected to the remaining one-phase heater. The terminal is attached to the end of the central terminal, and the fixed terminal is always bridged to form a star connection for the three-phase heater, and when the heater is abnormally energized, the heat deforms the terminal and separates it from the fixed terminal. A three-terminal overheat protector having a short-circuiting movable contact piece that simultaneously opens phase heaters in a sealed structure within an exterior case. (2) The connection part of the star-connected 3-phase heater is equipped with a fixed terminal for connection with the 2-phase heater and a short-circuiting movable contact piece at the end that constantly bridges these fixed terminals. A three-terminal overheat protector is provided which has a sealed structure with a bar-shaped central terminal connected to the heater, and each semi-finished product is connected to the fixed terminal and three lead wires coming out from the central terminal in advance. Connect each electrode terminal of the sheathed heater prepared in the state, and mold the connection part, and in case of abnormality in heater energization,
The short-circuiting movable contact piece, which connects the three-phase heaters in a star connection, undergoes temperature deformation upon receiving the heat of the heater, and operates to cut off contact with the fixed terminal and simultaneously open all three-phase heaters. Heater control circuit using a 3-terminal overheat protector.