JP5274155B2 - Overcurrent protection device - Google Patents

Abstract

An over current protection device that surely prevents a burnout by opening a power supply circuit to an electric compressor upon an over current, includes a heater which generates heat by a current flowing through the electric compressor, a first over current relay unit which is serially connected to the heater, is thermoelectrically coupled thereto, and includes a first bimetal contact piece which opens a first contact at a temperature equal to or more than a first temperature, and recovers the first contact at a temperature lower than the first temperature and higher than 0 DEG C, and a second over current relay unit which is serially connected to the heater, is thermoelectrically coupled thereto, and includes a second bimetal contact piece which opens a second contact at a temperatureequal to or higher than a second temperature higher than the first temperature, and recovers the second contact only at a temperature lower than 0 DEG C, where both the first over current relay unit and the second over current relay unit open the power supply circuit to the electric compressor.

Description

  The present invention relates to an overcurrent protection device that protects an electric compressor used in a cooling device such as a refrigerator or a small air conditioner from burning due to an overcurrent that occurs in an overload state or a locked state.

  Conventionally, in order to protect an electric compressor used for a cooling device such as a refrigerator and a small air conditioner from an overcurrent state, the electric compressor is closely attached to a main body case of the electric compressor, senses temperature, and is used as an electric motor of the electric compressor. An overcurrent protection device that opens and closes a switch contact piece connected in series between the electric motor of the electric compressor and the power source is provided using a bimetal that operates by the heat of the heater that generates heat in response to the flowing overcurrent. ing. In this case, when the operating temperature of the bimetal is reached due to the abnormal temperature of the main body case of the electric compressor or the heating of the heater in an overcurrent state, the bimetal is reversed in reverse, thereby opening the switch piece, While energizing is interrupted, energization to the heater is also interrupted. And when it cools to the return temperature of a bimetal by natural cooling, a bimetal will reverse reverse (return reverse), a switch contact piece will close, and electricity supply to the motor of an electric compressor and electricity supply to a heater will be restarted.

  In this way, the bimetal inversion operation prevents the electric compressor from being burned out, but when the electric compressor is overloaded or locked, the bimetal inversion and reverse inversion are repeated, Along with this, the switch piece opens and closes, but if this is done for a long time, the bimetal's forward / reverse life will end, and the bimetal will not be able to open the switch piece. Is welded, the electric motor of the electric compressor remains in an overcurrent state, and the electric motor is burned out.

  In order to solve such a problem, the connection contact piece having a contact for opening and closing the energization circuit to the electric motor of the electric compressor is opened by reversing the first bimetal contact piece in a normal overcurrent state, Shut off the energizing circuit. Then, when the life of the first bimetal piece is exhausted and the reversing operation is not performed, an overcurrent continues to flow to the electric motor of the electric compressor. However, due to the high temperature at that time, the second bimetal piece is It reverses and the said connection piece is opened, and the electricity supply circuit to the electric motor of an electric compressor is opened. The return temperature of the second bimetal contact piece is set to a temperature that does not return in a normal environment, such as −50 ° C., and once the operation is performed, energization to the electric motor of the electric compressor is continued. There is a technology having a so-called fail-safe function for preventing the electric motor from burning. (For example, patent document 1).

  In addition, the thermo bimetal is reversed by the abnormal temperature of the main body case of the electric compressor, the thermo switch part opens the energization circuit to the electric motor of the electric compressor, and the heater generates heat due to the overcurrent to the electric motor of the electric compressor. Case where the bimetal is reversed, the main bimetal movable contact opens from the fixed contact, the protector part that opens the energization circuit to the motor of the electric compressor is formed, and the thermo switch part, protector part and heater are made of one insulator And an adjustment screw for attaching the center portion of the main bimetal and the main bimetal are joined by a hot-melt metal (solder). (For example, Patent Document 2)

In this patent document 2, the main bimetal normally reverses and opens an energization circuit to the motor of the electric compressor. However, when the movable contact of the main bimetal is welded to the fixed contact, the heater continues to generate heat. When the temperature inside the case rises and the molten metal (solder) melts, the coupling between the adjustment screw and the main bimetal is broken, and the main bimetal is forced down by the coil spring attached to the adjustment screw, and it can be moved from the fixed contact. It has a so-called fail-safe function in which the contacts are forcibly peeled off.
Japanese Patent Application Laid-Open No. 07-201262 JP 09-180612 A

  Both of the technology of Patent Document 1 and the technology of Patent Document 2 are heaters that are generated when a contact that opens a current-carrying circuit to an electric motor of an electric compressor to prevent the electric motor from burning due to an overcurrent is welded for some reason. This is common in that the welded contacts are forcibly peeled off by the heat generated so that the non-energized state of the electric motor is continued and burnout is prevented.

  However, since the technique of Patent Document 2 is a mechanism in which the molten metal (solder) is melted and the movable contact is forcibly removed from the fixed contact, the operation time point for forcibly removing the movable contact from the fixed contact is It is affected by the melting temperature of hot-melt metal (solder). That is, the melting time differs depending on the bonding state and material of the hot-melt metal (solder), and it is difficult to determine the desired time when the movable contact is peeled off from the fixed contact.

  In the technique of Patent Document 2, since the molten metal (solder) is melted and the movable contact is forcibly removed from the fixed contact, once the operation is performed, it cannot be returned and reused. In order to restart the electric compressor, the overcurrent protection device must be replaced. Further, since the movable contact is forcibly removed from the fixed contact mechanically, there is a concern that the weld contact is not removed when the welding is strong.

  Since the technique of Patent Document 1 is not a technique in which hot-melt metal (solder) is melted as in Patent Document 2, the second bimetal contact piece that has once reversed is cooled to a return temperature of, for example, −50 ° C. or lower. Then, since it will return and it will be in a reusable state, the problem which becomes unusable like patent document 2 will be solved.

  However, since the technique of Patent Document 1 operates two bimetals with a single heater, there is a limit to making an overcurrent protection device of a different type depending on the heater selection. That is, the rating of the electric motor varies depending on the type of electric compressor, and the temperature rise varies depending on the type of electric compressor. Therefore, an overcurrent protection device that operates according to each electric compressor is required. For example, when the first bimetal contact piece is reversed when the temperature rises to 130 ° C. so as to cut off the energization to the motor, a type that opens the energization circuit to the motor when an overcurrent of 10 amperes flows for 10 seconds, , A type with a different combination of current value and operating time, such as a type that opens the energization circuit to the motor when an overcurrent of 12 amperes flows for 8 seconds, is stable and suitable for the electric compressor Need to work.

  However, since two bimetals are operated by one heater, it is difficult to make types with different overcurrent levels, even if different bimetal types can be used to make types with different inversion operating temperatures. . That is, since there is only one heater, for example, two bimetals that reverse at 130 ° C. are used, and the first bimetal contact piece reverses when 10 amps of overcurrent flows for 10 seconds, It is difficult to make a second bimetal contact that operates at different current values, such as a type that reverses when a 20 amp overcurrent flows for 10 seconds. For this reason, it is difficult to make a type with a different current value of the overcurrent flowing to the electric motor of the electric compressor, and there is a problem that the degree of freedom of design is limited and it is difficult to make a type suitable for the electric compressor. In addition, since the movable contact is forcibly peeled off from the fixed contact, there is a concern about the state where the contact is not peeled off when the welding is strong.

  In view of these points, the present invention increases the degree of freedom in design so as to cope with various inversion operating temperatures and various overcurrents by changing the type of bimetal and the wire diameter of the heater. Provide an overcurrent protection device that makes it easy to make a product that suits the machine. Also provided is an overcurrent protection device that is reusable.

An overcurrent protection device according to a first aspect of the invention is an overcurrent protection device connected in series with the motor to a current supply circuit to an electric motor of an electric compressor, wherein the overcurrent protection device is inverted at a temperature equal to or higher than a first temperature. A first bimetal contact piece which is separated from the fixed contact and cuts off a current supply circuit to the electric motor and comes into contact with and returns to the fixed contact at a return temperature lower than the first temperature and higher than 0 ° C .; A first overcurrent relay in which a first electric heater arranged in a thermal coupling relationship with the bimetal contact piece is housed in a first heat-resistant insulating case having a bottomed cylindrical shape; and a first overcurrent relay that is higher than the first temperature. A second bimetal contact piece that reverses above the temperature of 2 and leaves the fixed contact , interrupts the current supply circuit to the motor, and abuts and returns to the fixed contact only at a temperature lower than 0 ° C .; Arranged in thermal coupling relationship with bimetallic piece A second electrical heater consists of a second over-current relay housed in a second heat insulating case of the bottomed cylindrical shape, and the first bimetal contact piece and the series circuit of the first electric heater, the A series circuit of a second bimetal contact piece and the second electric heater is connected in series to form a series circuit with the electric motor, and the first overcurrent relay and the second overcurrent relay are connected to the electric compressor. The first bimetal contact piece and the second bimetal contact piece are housed in a cover containing an external terminal connected to a terminal protruding from the upper surface of the main body case, and the cover is attached to the upper surface of the main body case. Is located in a state where the temperature of the main body case is sensed, and the first bimetal contact piece senses the temperature of the main body case and is caused by heat generation of the first electric heater due to an overcurrent flowing through the electric motor. The second bimetal contact piece senses the temperature of the body case and the first bimetal contact piece is welded to a fixed contact. The second electric heater is in a relationship of reversing above the second temperature due to heat generation .

According to a second aspect of the present invention, there is provided the overcurrent protection device according to the first aspect, wherein the first overcurrent relay and the second overcurrent relay are structurally similar in structure, and the cover includes the first overcurrent protection device on one side. 1 overcurrent relay and the second overcurrent relay are provided side by side, the external terminal is housed on the other side, and when the cover is attached to the main body case, the external terminal is connected to the terminal protruding from the upper surface of the main body case. The first bimetal contact piece and the second bimetal contact piece are located in a state of sensing the temperature of the main body case .

In the first invention, the overcurrent protection device is constituted by a series connection of a separate first overcurrent relay and a second overcurrent relay, so that the same overcurrent supplied to the electric compressor flows through each heater. The first overcurrent relay detects an overload state of the electric compressor, a start-up failure or an overcurrent of the electric compressor in a locked state, and protects the electric compressor from both temperature and overcurrent. The second overcurrent relay detects the temperature rise and overcurrent of the electric compressor during contact welding of the first overcurrent relay, and can protect the electric compressor from both temperature and overcurrent. It becomes easy to determine the operation time points of the overcurrent relay and the second overcurrent relay, the degree of freedom of design is increased, a stable overcurrent protection operation can be obtained, and it is easy to make a device suitable for the electric compressor.
The first overcurrent relay and the second overcurrent relay are housed in a cover that is attached to the upper surface of the main body case of the electric compressor. By attaching this cover, the first bimetal contact piece and the second bimetal contact piece are accommodated. Since the piece senses the temperature of the main body case, both the first bimetal contact piece and the second bimetal contact piece sense the temperature of the main body case and generate heat from the electric heater due to overcurrent flowing through the motor. The current supply circuit to the electric motor can be opened by reversing operation at the set temperature.
In addition, the second overcurrent relay can maintain its state once it is operated if the return temperature is set to a low temperature that cannot be reached under normal use, such as -50 ° C. It is possible to stably maintain the energization cut-off state. Furthermore, once it has been operated, it can be reused if it is cooled below the return temperature, which is economical.

In the second invention, since the first overcurrent relay and the second overcurrent relay are structurally similar in structure, various reversal operating temperatures can be obtained by changing the type of the bimetal contact piece and the wire diameter of the electric heater. It is possible to make a first overcurrent relay and a second overcurrent relay that can cope with various overcurrents, and it is easy to determine the reversal operation time of the first overcurrent relay and the second overcurrent relay, The degree of freedom is increased, and a stable overcurrent protection operation can be obtained, which makes it easy to make a device suitable for the electric compressor.
Further, the connection of the external terminal to the terminal protruding from the upper surface of the main body case and the attachment of the first bimetal contact piece and the second bimetal contact piece to the state of sensing the temperature of the main body case are achieved by attaching the cover. Will be.

The overcurrent protection device of the present invention is an overcurrent protection device connected in series with the motor to a current supply circuit to an electric motor of an electric compressor, wherein the overcurrent protection device is inverted at a temperature equal to or higher than a first temperature. A first bimetal contact piece which is separated from the fixed contact and cuts off a current supply circuit to the electric motor and comes into contact with and returns to the fixed contact at a return temperature lower than the first temperature and higher than 0 ° C .; A first overcurrent relay in which a first electric heater disposed in a thermal coupling relationship with the bimetal contact piece is housed in a first heat-resistant insulating case having a bottomed cylindrical shape; and a second higher than the first temperature. A second bimetal contact piece that reverses above the fixed temperature, leaves the fixed contact , interrupts the current supply circuit to the motor, and contacts and returns to the fixed contact only at a temperature lower than 0 ° C. , and the second bimetal Placed in thermal coupling with the piece And an electric heater consists of a second over-current relay housed in a second heat insulating case of the bottomed cylindrical shape, and the first bimetal contact piece and the series circuit of the first electric heater, said first A series circuit of two bimetal contacts and the second electric heater is connected in series to form a series circuit with the electric motor, and the first overcurrent relay and the second overcurrent relay are the main body of the electric compressor. The first bimetal contact piece and the second bimetal contact piece are accommodated in a cover containing external terminals connected to terminals protruding from the upper surface of the case, and the cover is attached to the upper surface of the main body case. Located in a state of sensing the temperature of the main body case, the first bimetal contact piece senses the temperature of the main body case and generates heat of the first electric heater due to an overcurrent flowing through the electric motor. The second bimetal contact piece senses the temperature of the main body case and the first bimetal contact piece is welded to the fixed contact. The relationship of reversing above the second temperature due to heat generated by the second electric heater is described below, and examples of the present invention will be described below.

  FIG. 1 is a circuit diagram in which a first overcurrent relay and a second overcurrent relay constituting an overcurrent protection device according to the present invention are connected in series, and FIG. 2 is a first overcurrent relay and a second overcurrent according to the present invention. 3 is a side view showing the external appearance of the relay, FIG. 3 is a diagram showing the external appearance of the first overcurrent relay and the second overcurrent relay shown in FIG. 2, and FIG. 4 is the first overcurrent relay shown in FIG. FIG. 5 is a diagram showing a state in which the overcurrent protection device according to the present invention is attached to the upper surface of the sealed case of the electric compressor, and FIG. 6 is an overcurrent diagram in FIG. It is a concrete perspective view of the part which attaches a protection device to the upper surface of the airtight case of an electric compressor.

  The overcurrent protection device 1 of the present invention is attached in close contact with the main body case 51 of the electric compressor 50 in order to protect the electric compressor 50 used in a cooling device such as a refrigerator or a small air conditioner from its overcurrent state. It operates to sense the temperature and cut off the energization of the motor 52 in accordance with the overcurrent flowing through the motor 52 of the electric compressor 50. In the electric compressor 50, a motor 52 and a refrigerant compressor unit 53 are housed in a main body case 51 constituting a sealed case, and the refrigerant compressor unit 53 is driven by the electric motor 52 to compress refrigerant. It is.

  The overcurrent protection device 1 is configured to be connected in series with the motor 52 to a current supply circuit to the motor 52 of the electric compressor 50, and the overcurrent protection device 1 is electrically driven at a temperature equal to or higher than a first temperature (T1 ° C.). The first bimetal contact piece 2A that cuts off the current supply circuit to the motor 52 of the compressor 50 and returns at a return temperature lower than the first temperature (T1 ° C.) and higher than 0 ° C. is made of the first synthetic resin. The first overcurrent relay 2 housed in the heat resistant insulation case 2K and the first overcurrent relay 2 connected in series and electrically compressed at a second temperature (T2 ° C) higher than the first temperature (T1 ° C). The second bimetal contact piece 3A which cuts off the current supply circuit to the electric motor 52 of the machine 50 and returns only at a temperature lower than 0 ° C. (T3 ° C.) is housed in the second heat-resistant insulating case 3K made of synthetic resin. 2 overcurrent relay 3.

  This will be specifically described below. As shown in FIGS. 1 to 4, the first overcurrent relay 2 is mainly composed of a heat-resistant insulating case 2K made of a synthetic resin having a bottomed cylindrical shape with one surface (the lower surface in FIG. 2) having an opening 2K1. The first bimetal contact piece 2A is supported on a support shaft 2C fixed to the center portion of the bottom wall 2K2 of the case 2K with a nut 2D away from the inner surface of the case 2K. The bimetal contact piece 2A includes movable side contacts 2E at the left and right projecting portions of a circular bimetal plate. Two external terminals A and B are attached to the bottom wall 2K2 of the case 2K (upper side wall in FIG. 2), and the external terminals A and B are exposed inside the case 2K.

  A terminal C is provided inside the bottom wall (upper side wall in FIG. 2) 2K2, and the inner end of the case 2K of the terminal A and the terminal C have fixed contacts 2G respectively corresponding to the movable side contacts 2E of the bimetal contact piece 2A. One end of the first electric heater 2B is connected to the inner end of the case 2K of the terminal B, and the other end of the electric heater 2B is connected to the terminal C. In a normal state that is not an overcurrent state, the bimetal contact piece 2A is in a state in which the left and right movable contacts 2E are in contact with the left and right fixed contacts 2G, as shown by the solid line in FIG. The first electric heater 2B having a predetermined electric resistance is disposed corresponding to the circular portion of the bimetal contact piece 2A so as to extend over the terminals B and C and to be in a thermal coupling relationship with the bimetal contact piece 2A. Yes.

  The second overcurrent relay 3 is structurally similar to the first overcurrent relay 2 in structure. Therefore, in FIGS. 1 to 4, the same parts as those of the first overcurrent relay 2 are indicated by reference numerals in parentheses. That is, as shown in FIGS. 1 to 4, the second overcurrent relay 3 is mainly composed of a heat-resistant insulating case 3K made of synthetic resin having a bottomed cylindrical shape with one surface (the lower surface in FIG. 2) being an opening 3K1. The first bimetal contact piece 3A is supported on a support shaft 3C fixed to the center of the bottom wall (upper side wall) 3K2 of the case 3K with a nut 3D while being separated from the inner surface of the case 3K. Yes. The bimetal contact piece 3A includes movable side contacts 3E on the left and right projecting portions of a circular bimetal plate. Two external terminal terminals A and B are attached to the bottom wall (upper side wall in FIG. 2) 3K2 of the case 3K, and the terminals A and B are exposed inside the case 3K.

  A terminal C is provided on the inner side of the bottom wall (upper side wall in FIG. 2) 3K2, and the inner end of the case 3K of the terminal A and the terminal C have fixed contacts 3G respectively corresponding to the movable side contacts 3E of the bimetal contact piece 3A. The one end of the second electric heater 3B is connected to the inner end of the case 3K of the terminal B, and the other end of the electric heater 3B is connected to the terminal C. In a normal state that is not an overcurrent state, the bimetal contact piece 3A is in a state in which the left and right movable contacts 3E are in contact with the left and right fixed contacts 3G, as shown by the solid line in FIG. The second electric heater 3B having a predetermined electric resistance is arranged corresponding to the circular portion of the bimetal contact piece 3A so as to extend over the terminals B and C and to be in a thermal coupling relationship with the bimetal contact piece 3A. Yes.

  As shown in FIGS. 5 and 6, the overcurrent protection device 1 has a configuration in which the first overcurrent relay 2 and the second overcurrent relay 3 configured as described above are combined and housed in a predetermined cover KS. The cover KS is attached to the upper surface of the main body case 51 of the electric compressor 50, and the external terminal 57 for power supply housed in the cover KS is connected to the terminals 54A, 54B, 54C protruding from the upper surface of the main body case 51. In addition to being connected, the bimetal contact pieces 2 </ b> A and 3 </ b> A are positioned to sense the temperature of the main body case 51.

  In the cover KS, the first overcurrent relay 2 and the second overcurrent relay 3 are provided on one side, and the external terminal 57 is accommodated on the other side. The structure in which the cover KS is attached to the upper surface of the main body case 51 is such that the engagement holes 60A and 60B are formed in the left and right engaging pieces of the metal support base 59 attached to the upper surface of the main body case 51, 58A and 58B are attached to the corresponding locking holes 60A and 60B by being locked by the elasticity of the cover KS, respectively. As a result, the cases 2K and 3K are brought into a state in which the respective openings 2K1 and 3K1 are in contact with the support base 59.

  In the first overcurrent relay 2 and the second overcurrent relay 3 configured as described above, the series circuit of the first overcurrent relay 2 and the second overcurrent relay 3 is connected in series with the electric motor 52 of the electric compressor 50. . In a state where the movable contact 2E of the first overcurrent relay 2 is in contact with the fixed contact 2G, the bimetal contact piece 2A and the electric heater 2B form a first series circuit. In addition, with the movable contact 3E of the second overcurrent relay 3 in contact with the fixed contact 3G, the bimetal contact piece 3A and the electric heater 3B form a second series circuit. The first and second series circuits are connected in series and connected to the motor 52 in series.

  One specific circuit connection is described below. The electric motor 52 shown in FIG. 1 shows the case of an AC electric motor, and the power source 55 is also an AC power source. If the electric motor 52 is controlled by an inverter whose rotation speed is variable by frequency conversion, the power source 55 is an inverter-controlled power source.

  One terminal of the motor 52 is connected to the power supply 55, and the first overcurrent relay 2 is connected to the terminal A of the other terminal 54 </ b> A of the motor 52. The bimetal contact piece 2A in which the movable contact 2E is in contact with the fixed contact 2G and the electric heater 2B form a first series circuit. The terminal B of the first overcurrent relay 2 is connected to the terminal A of the second overcurrent relay 3. In the second overcurrent relay 3, the bimetallic contact 3 </ b> A in which the movable contact 3 </ b> E is in contact with the fixed contact 3 </ b> G and the electric heater 3 </ b> B form a second series circuit, and the terminal B is connected to the terminal 54 </ b> B connected to the power supply 55. Connected. As a result, the first and second series circuits are connected in series to form a series circuit with the motor 52.

  In this configuration, during normal operation of the electric compressor 50, the current flowing through the electric motor 52 is less than the set value, so that the amount of heat generated from the electric heater 2B increases as the bimetal contact piece 2A is reversed as indicated by the dotted line in FIG. Further, the amount of heat generated from the electric heater 3B is not so large that the bimetal contact piece 3A is reversed as shown by the dotted line in FIG. 1, and the temperature of the main body case 51 is also shown by the dotted line in FIG. Therefore, the motor 52 is in a state of supplying power from the power source 55 while maintaining the state in which the movable contact 2E is in contact with the fixed contact 2G and the movable contact 3E is in contact with the fixed contact 3G. The electric compressor 50 continues the normal operation state.

  However, when the electric compressor 50 is overloaded, or when the electric compressor 50 is in a starting failure or locked state, the amount of heat received by the bimetal contact pieces 2A and 3A increases due to the temperature rise of the electric compressor 50. Further, when an overcurrent exceeding the set value flows, the amount of heat generated by the electric heaters 2B and 3B increases, and the amount of heat received by the bimetal contact pieces 2A and 3A increases. As a result, the bimetal contact piece 2A is first heated to a first temperature (T1 ° C.... 120 ° C.) or higher, which is the operating temperature, so that the bimetal contact piece 2A is inverted as shown by the dotted line in FIG. The movable contact 2E is separated from the fixed contact 2G and interrupts the current supply circuit to the motor 52. Since the reversal operation temperature of the bimetal contact piece 3A is set to be considerably higher than the first temperature (T1 ° C.), the reversal operation is not performed, and the movable contact 3E remains in contact with the fixed contact 3G. It is.

  Thus, by stopping the operation of the electric compressor 50, the electric heater 2B is not energized, and by natural cooling, the return temperature (for example, lower than the first temperature (T1 ° C .... 120 ° C.) and higher than 0 ° C. (for example, 100 ° C.), the bimetal contact piece 2A reversely reverses (returns) as shown by the solid line in FIG. 1, the movable contact 2E comes into contact with the fixed contact 2G again, and the electric motor 52 is activated again to start the electric compressor 50. Returns to the operating state. At this time, if the overload state of the electric compressor 50, or the start-up failure or the locked state is eliminated, the electric current flowing through the electric motor 52 is less than the set value, so that the electric compressor 50 is normal as described above. Continue operating. However, when the electric compressor 50 is restored, if the overload state or the start-up failure or the locked state is not eliminated, the bimetal contact piece 2A is heated again to the first temperature (T1 ° C.) that is the operating temperature. As a result, the bimetal contact piece 2A is reversed as indicated by the dotted line in FIG. 1, and the movable contact 2E is separated from the fixed contact 2G, thereby interrupting the current supply circuit to the motor 52. In this way, the electric compressor 50 is protected from an overload state, or burnout caused by a starting failure or a locked state.

  However, when the number of times of opening / closing the movable contact 2E with respect to the fixed contact 2G by reversing and returning the bimetal contact piece 2A is performed over a long period of time, or when the electric compressor 50 is operated over a long period of time, the fixed contact The opening / closing frequency of the movable contact 2E with respect to 2G increases, the life of the bimetal contact piece 2A reaches the normal reversal / reverse reversal, the movable contact 2E cannot be opened with respect to the fixed contact 2G, and the movable contact 2E When welding to the fixed contact 2G, the electric motor 52 of the electric compressor 50 remains in an overcurrent state, and if this continues, the electric motor 52 is burned out.

  Thus, when the movable contact 2E is welded to the fixed contact 2G, energization to the electric heater 3B continues, so the amount of heat generated by the electric heater 3B increases and the amount of heat received by the bimetal contact piece 3A increases. As a result, when the bimetal contact piece 3A is heated to the second temperature (T2 ° C.) or higher, which is the operating temperature, the bimetal contact piece 3A is inverted as shown by the dotted line in FIG. 1, and the movable contact 3E is fixed. It leaves | separates from the contact 3G, interrupts | blocks the electric current supply circuit to the electric motor 52, and prevents that the electric motor 52 burns out.

  The second temperature (T2 ° C.), which is the operating temperature at which the bimetallic contact piece 3A is inverted and the movable contact 3E is separated from the fixed contact 3G, is reversed and the movable contact 2E is separated from the fixed contact 2G. Since the temperature is set to be considerably higher than the first temperature (T1 ° C.... 120 ° C., for example, 120 ° C.), for example, 150 ° C., the bimetal contact piece 3A is reversed before the bimetal contact piece 2A is reversed. It will not work.

  The return temperature at which the movable contact 3E comes into contact with the fixed contact 3G again when the bimetal contact piece 3A reversely reverses (returns) as shown by the solid line in FIG. 1 is set to a temperature sufficiently lower than 0 ° C. (T3 ° C.). This temperature is a sub-zero temperature (T3 ° C.) that is sufficiently lower than the low temperature that occurs in the temperature situation where the electric compressor 50 is used in a normal environment. Since T3 ° C. is several tens of degrees below zero, for example, about −50 ° C., once the bimetal contact piece 3A is reversed as shown by the dotted line in FIG. 1, the bimetal contact piece 3A is artificially brought up to this return temperature. Since it will not return unless it is cooled, once the bimetal contact piece 3A is reversed as shown by the dotted line in FIG. 1, it will not return permanently, so the burnout protection of the electric compressor 50 continues. Will be. The method of cooling the bimetal contact piece 3A to the return temperature can be used again if it is cooled by liquid nitrogen or a low-temperature refrigeration apparatus.

  As described above, in the type in which the reverse operation is performed by the heat generated by the electric heater, the electric resistance of the bimetal contact pieces 2A and 3A is considerably smaller than the electric resistance of the electric heaters 2B and 3B. The self-heating of the bimetal contact pieces 2A and 3A is small, and the reversal operation when an overcurrent flows is substantially due to the heating of the electric heaters 2B and 3B.

  By configuring the series circuit of the first overcurrent relay 2 and the second overcurrent relay 3 as described above, by changing the types of the bimetal contact pieces 2A and 3A and the wire diameters of the electric heaters 2B and 3B, The first overcurrent relay 2 and the second overcurrent relay 3 that can cope with the reverse operation temperature and various overcurrents can be made, and the first overcurrent relay 2 and the second overcurrent relay 3 are reversed. It becomes easy to determine the time point, the degree of freedom of design increases, a stable overcurrent protection operation can be obtained, and a product suitable for the electric compressor can be easily made.

  FIG. 1 shows circuit connections of the power source 55, the motor 52, the first overcurrent relay 2, the second overcurrent relay 3, and the power source 55, but the first overcurrent relay 2 and the second overcurrent relay 3 The positions may be switched to connect the power source 55, the electric motor 52, the second overcurrent relay 3, the first overcurrent relay 2, and the power source 55.

  Further, in the above, the bimetal contact piece 2A of the first overcurrent relay 2 and the bimetal contact piece 3A of the second overcurrent relay 3 together with the temperature sensing of the main body case 51 of the electric compressor 1, the corresponding electric heaters 2B, 3B. However, the electric heaters 2B and 3B may be omitted, and the reverse operation may be performed only by sensing the temperature of the main body case 51.

  In the above description, the bimetal contact piece 2A of the first overcurrent relay 2 and the bimetal contact piece 3A of the second overcurrent relay 3 sense the temperature of the main body case 51 of the electric compressor 1. The contact pieces 2A and 3A may be reversed only by the amount of heat generated by the corresponding electric heaters 2B and 3B.

  In the present invention, the configuration of the electric compressor 1, the configurations of the first overcurrent relay 2 and the second overcurrent relay 3 and the like are not limited to the above-described embodiment, and various modifications can be made without departing from the technical scope of the present invention. Are contemplated and encompass various embodiments.

It is the circuit diagram by which the 1st overcurrent relay and the 2nd overcurrent relay which comprise the overcurrent protection apparatus which concern on this invention were connected in series. It is a side view which shows the external appearance of the 1st overcurrent relay and 2nd overcurrent relay which concern on this invention. It is a figure which shows the external appearance by the side of the terminal part of the 1st overcurrent relay and 2nd overcurrent relay which are shown in FIG. It is the internal block diagram seen from the opening surface of the 1st overcurrent relay and 2nd overcurrent relay which are shown in FIG. It is a figure which shows the state which attached the overcurrent protection apparatus which concerns on this invention to the upper surface of the airtight case of an electric compressor. It is a specific perspective view of the part which attaches the overcurrent protection apparatus in FIG. 5 to the upper surface of the airtight case of an electric compressor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Overcurrent protection device 2 ... 1st overcurrent relay 2A ... Bimetal contact piece 2B ... Electric heater 2C ... Support shaft 2E ... Movable contact 2G ... Fixed Contact 2K ・ ・ ・ Heat-resistant insulation case 3 ・ ・ ・ Second overcurrent relay 3A ・ ・ ・ Bimetal contact piece 3B ・ ・ ・ Electric heater 3C ・ ・ ・ Support shaft 3E ・ ・ ・ Moving side contact 3G ・ ・ ・ Fixed contact 3K: heat-resistant insulation case 50 ... electric compressor 51 ... main body case 52 ... electric motor 53 ... compression section 55 ... power supply

Claims (2)

In the overcurrent protection device connected in series with the motor to the current supply circuit to the motor of the electric compressor, the overcurrent protection device is:
The first temperature is reversed above the first temperature, separated from the fixed contact , interrupts the current supply circuit to the motor, and comes into contact with and returns to the fixed contact at a return temperature lower than the first temperature and higher than 0 ° C. A first overcurrent relay in which a bimetal contact piece and a first electric heater arranged in a thermal coupling relationship with the first bimetal contact piece are housed in a first heat-resistant insulating case having a bottomed cylindrical shape ;
The second temperature is reversed above the second temperature higher than the first temperature, is separated from the fixed contact , cuts off the current supply circuit to the motor, and comes into contact with and returns to the fixed contact only at a temperature lower than 0 ° C. consists of a bimetal contact piece, and a second electrical heater disposed in said second bimetal contact piece and the thermal coupling relation, a second overcurrent relay housed in a second heat insulating case of a bottomed cylindrical shape ,
A series circuit of the first bimetal contact piece and the first electric heater, and a series circuit of the second bimetal contact piece and the second electric heater are connected in series to form a series circuit with the electric motor. ,
The first overcurrent relay and the second overcurrent relay are housed in a cover that houses an external terminal connected to a terminal protruding on the upper surface of the main body case of the electric compressor,
The first bimetal contact piece and the second bimetal contact piece are positioned in a state of sensing the temperature of the main body case by attaching the cover to the upper surface of the main body case,
The first bimetal contact piece senses the temperature of the main body case and has a relationship of reversing above the first temperature due to heat generation of the first electric heater due to overcurrent flowing through the electric motor. The bimetal contact piece 2 senses the temperature of the main body case, and the second bimetallic contact piece is heated above the second temperature due to heat generation of the second electric heater due to overcurrent when the first bimetal contact piece is welded to the fixed contact. An overcurrent protection device characterized by being in an inverted relationship . The first overcurrent relay and the second overcurrent relay are structurally similar in structure, and the first overcurrent relay and the second overcurrent relay are provided on one side in the cover, The external terminal is housed on the other side, and by attaching the cover to the main body case, the external terminal is connected to a terminal protruding from the upper surface of the main body case, and the first bimetal contact piece and the first 2. The overcurrent protection device according to claim 1, wherein the bimetal contact piece of 2 is located in a state of sensing the temperature of the main body case .

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