JP2007278184A - Protection device for electric compressor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a protection device for small electric compressor capable of surely executing a final protection action at the time of abnormal high temperature. <P>SOLUTION: In the protection device 1 for the electric compressor, a heat generating structure body 7 is arranged in electrically series with a motor in a sealed vessel, and a heat generating part 7A of the heat generating structure body 7 is put between an electrically insulating retention body 8 and a heat radiating contact 10. Heat of the heat generating part 7a is conducted by the heat radiating contact 10 to the sealed vessel via a thermal action plate 9 and is radiated to coolant flowing around the same during normal operation of the motor. If temperature of coolant abnormally rises, heat from the heat generating part 7A is not easily radiated since the sealed vessel itself is heated, temperature of the thermal action plate 9 rises and a bend orientation is reversed to separate the heat radiation contact from the heat generating structure body. Consequently, heat from the heat generating part loses where to go and temperature rises further, and finally, temperature reaches fusing temperature to shut off an electric circuit. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  TECHNICAL FIELD The present invention relates to a protection device used for a hermetic electric compressor or the like, and a fuse mechanism for reliably interrupting an electric circuit when an excessive current flows due to a short circuit of a winding or when an abnormally high temperature occurs due to a decrease in refrigerant gas. The present invention relates to a protective device for an electric compressor having

  2. Description of the Related Art Conventionally, a protective device for preventing electric motors from being burned is used in a hermetic electric compressor for refrigerants used in air conditioners and the like. As this protective device, there is a device that monitors the current and temperature flowing through the electric compressor. The mounting position is also arranged inside the sealed container of the electric compressor and exposed to the refrigerant, or arranged outside to pick up the temperature of the container surface.

  Among them, the one that is disposed inside the container and exposed to the high-temperature and high-pressure refrigerant has an advantage that the refrigerant temperature can be detected more rapidly, and is used in many electric compressors. Therefore, an example of a protective device disposed in the hermetic container of the compressor will be described with reference to FIG. In this protective device 101, a metal housing 102 and a lid plate 103 constitute an airtight container. In this hermetic container, a movable contact 105 fixed to the tip of a thermally responsive member 104 such as a bimetal, and a conductive terminal 107A inserted through a through hole provided in the lid plate 103 and insulated and fixed by a glass 106 are arranged. A contact mechanism in which the fixed contact 108 is arranged is configured.

  The heat-responsive plate 104 drawn into a shallow dish is normally bent toward the lid plate 103 to bring the movable contact 105 into contact with the fixed contact 108, and at a predetermined temperature by self-heating due to energization or heat from the outside. When the above is reached, the bending direction is reversed, the movable contact is pulled away from the fixed contact, and the connection is released.

  Further, another conductive terminal 107B is inserted and fixed in the cover plate, and the tip of the sealed container side and the cover plate 103 are connected by a heater 109 made of a resistance material.

  The protection device 101 is used in a single-phase electric compressor that is a device to be protected, and conductive terminals 107A and 107B are connected in series on a power supply path to the motor. At this time, an electric path connecting the conductive terminal 107A-the fixed contact 108-the movable contact 105-the thermally responsive plate 104-the housing 102-the lid plate 103-the heater 109-the conductive terminal 107B is formed.

  The heat responsive plate 104 self-heats due to the energized current and is heated by the heat from the heater 109. Since the heat is taken away by the refrigerant flowing around the container through the housing 102, the temperature of the heat responsive plate becomes the operating temperature during normal operation. Energization is continued because it balances before reaching.

  For example, when an overcurrent flows to the motor for some reason or when the compressor container becomes abnormally hot, the balance between heat generation and heat dissipation in the protective device is lost, and the protective device becomes hot and the thermal response plate When the temperature reaches a predetermined temperature and reverses, the contacts are separated and the electric circuit is interrupted.

  In a hermetic type electric compressor, the electric motor and the compressor inside thereof generate heat due to energization of the windings and friction of the sliding part, respectively, but these are usually cooled by the refrigerant flowing around the motor and in the compressor. The heat is released to the outside by a heat exchanger in the refrigeration cycle. Therefore, during normal operation, each component such as the refrigerant gas and the electric motor is kept below a predetermined temperature.

  Since the protection device 101 is operated by a balance between heat generation and heat dissipation inside the protection device, the normal internal temperature is higher than the ambient temperature. In addition, the use of the ambient temperature makes it easy to detect the change by installing it at a relatively high temperature, for example, on the motor winding.

Japanese Patent Laid-Open No. 2-227928 JP2005-268058 JP-A-10-134697

  Recently, for the purpose of improving safety, it is required to prevent damage to an airtight terminal due to overheating in an electric compressor. Explaining this, if the refrigerant gas in the electric compressor decreases for some reason, the cooling efficiency of the motor or compressor cooled by the refrigerant decreases, and the amount of heat released to the outside by the refrigeration cycle also decreases. The temperature inside the aircraft rises.

  When the temperature exceeds a predetermined temperature, the glass of the hermetic terminal begins to deteriorate and the internal pressure also rises, so that the glass of the hermetic terminal is eventually destroyed and gas is ejected from the hole and the conductive pin is blown away at the same time. There is a risk of electrical accidents.

  When the temperature rises due to such refrigerant gas leakage, the protection device 101 may not be sufficiently protected. This is because the protective device 101 uses heat generated by the operating current of the motor as described above. In other words, the conventional protective device is operated by increasing the current value of the motor due to the overload condition of the compressor, etc., and even when the ambient temperature rises, the cause is the amount of heat generated by the motor due to the overcurrent etc. Therefore, the protective device was attached to the part near the heat generation part such as the motor winding, which tends to be relatively hot. Or, it was determined that the increase in ambient temperature was auxiliary, and the operating characteristics were determined mainly by increasing current.

  However, when the rise in internal temperature is caused by refrigerant gas leakage, the load applied to the electric motor is reduced due to the pressure drop due to the decrease in the refrigerant, so that the current value may be lower than the normal operating current. Therefore, it should be operated in response to an increase in the ambient temperature, but it is difficult to operate with a change in the ambient temperature in a structure in which an operating current is passed through the thermally responsive plate to generate heat. For example, the operating temperature of the heat responsive plate 104 of the protective device 101 can be lowered, but in this case, since the difference from the heat generated by the normal operating current is small, it operates even with a very short overcurrent that should normally be allowed. Operation setting is very difficult.

  Further, the protection device 101 has a structure in which the thermal reaction plate returns to the initial state and resumes energization by lowering the temperature even after the operation of the thermal reaction plate 104 so as to cope with an overcurrent caused by a temporary cause. However, it is extremely dangerous for the refrigerant temperature to rise to such a temperature as to deteriorate the sealed terminal, and it is necessary to avoid resuming energization.

  For example, a thermal fuse that blows at a predetermined temperature may be used as the final protection. However, it is difficult to always flow an operating current of an electric motor of several tens of amperes with a conventional thermal fuse. there were. Therefore, a combination of a thermal fuse and a current fuse has been proposed. However, the thermal fuse is connected to a control circuit different from that to which the current fuse is connected, and a circuit therefor is required.

  Also, in the protective device 101, for example, a melted part with a reduced cross section is provided in a part of the heater 109, and the melted part can be melted to cut off the electric circuit, so that the electric circuit can be cut off permanently. The part is a current fuse that is blown by a large current due to a short circuit or the like, and cannot be blown only by a change in ambient temperature.

  Therefore, apart from the conventional protection device, there is a demand for a small protection device that can reliably perform the final protection operation at an abnormally high temperature.

  Therefore, the protective device for an electric compressor of the present invention has a metal hermetic container, and the hermetic container is provided with at least two electric terminals, and at least one of the electric terminals is provided in a hole formed in the hermetic container. A conductive terminal that is inserted and hermetically insulated and fixed, and a heat generating structure that electrically connects the electrical terminals is arranged inside the hermetic container, and the heat-responsive plate has one end thereof capable of exchanging heat with the hermetic container. The heat generating plate is provided with a heat-dissipating contact at the other end of the heat-responsive plate, and the heat-generating structure is provided with a heat-generating portion having a particularly high resistance value. The heat is transferred to the hermetic container through the heat radiating part and the thermal reaction plate, and further released to the outside through the hermetic container, so that the heat generating part is kept below the melting temperature. Invert the heat dissipation contact Heating unit is characterized by blocking the path and melted by self-heating by reducing the heat dissipation path of heat generating portions away from the heat unit.

  Another feature is that an airtight container is constituted by a lid plate in which a conductive terminal is hermetically insulated and fixed to a metal plate and a housing in which an opening is closely fixed to the lid plate, and the metal of the lid plate is placed in the hermetic container. A heat generating structure that electrically connects the plate and the conductive terminal is arranged, and one end of the heat responsive plate is fixed to the housing so that heat can be exchanged with the housing, and another heat insulating contact is arranged on the other end. An electrically insulating holding body is disposed between the cover plate and the heat generating structure, and the heat generating structure is provided with a heat generating part having a small cross-sectional area and a particularly high resistance value. The heat of the heat generating part is efficiently transferred to the airtight container by inserting the heat dissipation contact and the holding body, and the heat generating part is kept below the melting temperature by being released to the outside through the airtight container. When the plate reaches a predetermined temperature, the direction of curvature is reversed and the heat dissipation contacts generate heat. Reducing the heat dissipation path of heat generating portions away from one to the heat generating portion by self-heating is to block the path and melted at.

  According to the protection device for an electric compressor of the present invention, even when a relatively large operating current always flows like an electric motor of an electric compressor, it can be connected in series to a power source, and the current increases when overheating occurs. It is possible to obtain a protection device that can reliably perform a protection operation even in the absence of the problem.

  Cooling by efficiently transferring the heat of the heat generating part provided on the electric circuit to the outside of the sealed container, mechanically lowering the heat conduction efficiency when the ambient temperature rises, so that the energization current does not change when the surroundings are overheated However, the temperature of the heating part rises and melts.

  Next, an embodiment will be described with reference to FIGS. This electric compressor protective device (hereinafter referred to as a protective device) 1 includes a metal housing 2 and a cover plate 3 to form an airtight container. The housing 2 has a long dome shape, and the cover plate 3 is a metal conductive terminal that is an electric terminal in each of the two through holes 3B1 and 3B2 formed in the oval metal plate 3A that matches the shape of the opening of the housing. 4A and 4B are inserted and hermetically insulated and fixed by glass 5 which is an electrically insulating filler. A ceramic insulator 6 for obtaining a creepage distance between the conductive terminal 4 and the metal plate 3 </ b> A is integrally disposed with the glass 5 on the inner surface of each glass 5 without gap.

  A heat generating structure 7 that connects the conductive terminals 4 </ b> A and 4 </ b> B, which are electrical terminals, is disposed in the vicinity of the tip inside the hermetic container. The heat generating structure 7 is provided with a heat generating portion 7A having a particularly high resistance value by narrowing the width of the heat generating structure 7 than the others. When the heat generating portion 7A does not radiate heat from a heat radiating contact described later, It is set so that it can be melted by heat generated by normal operating current. The heat generating portion 7A is inserted between a contact portion 8A provided on the holding body 8 disposed between the metal plate 3A and a heat radiation contact 10 disposed on the tip of the thermally responsive plate 9. Both the holding body 8 and the heat radiation contact 10 are made of an electrically insulating material such as ceramics, and heat from the heat generating structure 7 is transmitted to the housing 2 or the metal plate 3A constituting the airtight container, but no current flows.

  The thermally responsive plate 9 is made of bimetal, trimetal, or the like, and is usually curved so that the heat dissipation contact 10 is pressed against the heat generating structure 7. Further, the thermal response plate 9 changes its curvature when its temperature rises, and is configured to pull the heat dissipation contact 10 away from the heat generating structure 7 when it reaches a predetermined temperature. In the present embodiment, the heat responsive plate 9 is formed by drawing a bimetal into a shallow dish shape so as to perform a sudden reversal operation at a predetermined temperature, and the heat responsive plate support 11 fixed to the adjusting portion 2A of the housing 2 is provided. Via the housing 2. The reverse operation temperature is set to a temperature that is reached when the ambient temperature is in an abnormal overheat state without operating during normal operation of the electric compressor to be controlled. Further, by slightly pressing and deforming the adjustment portion 2A of the housing from the outside, the contact pressure of the radiating contact 10 is adjusted, and the reversal temperature of the thermally responsive plate 9 is finely adjusted.

  This protection device 1 is connected in series with the winding of the electric motor, and an electric motor operating current flows between the conductive terminals 4A-4B which are electric terminals. During normal operation of the motor, the heat of the heat generating portion 7A of the heat generating structure 7 generated by the operating current is taken from the heat radiating contact 10 to the housing 2 through the heat responsive plate 9 and to the metal plate 3A through the holding body 8. Furthermore, the metal plate 3A and the housing 2 which are sealed containers are always cooled by the refrigerant flowing around, and the heat transmitted from the heat generating part 7A is taken away by the refrigerant, so that the heat generating part 7A is always kept below the melting temperature and energization is not performed. Will continue.

  If the refrigerant temperature rises for some reason and reaches a dangerous temperature at the airtight terminal, for example, 150 ° C., the housing 2 and the metal plate 3A constituting the hermetic container are also heated, so that the heat radiation from the thermal reaction plate 9 becomes insufficient. The thermally responsive plate is heated to a predetermined operating temperature, and its bending direction is reversed as shown in FIG. 3 so that the heat radiating contact 10 is pulled away from the heat generating structure 7.

  Therefore, the heat of the heat generating portion 7A of the heat generating structure loses the heat dissipation path and further rises in temperature, leading to fusing as shown in FIGS. Since the electric circuit is reliably interrupted in this way, the energization is stopped before the electric motor is burned out, and an accident such as a missing pin of the glass terminal can be prevented. In addition, since the heat dissipation contact 10 is made of an electrically insulating material such as ceramics, energization is performed between the heat generating portions 7A1 and 7A2 that are blown even if the temperature of the thermally responsive plate 9 decreases and the curving direction is restored after the energization is cut off. It will not be resumed. Further, even when a large current flows due to a so-called rare short of an electric motor, the heat generating structure is melted to cut off the electric circuit and stop energization thereafter.

  If the return temperature of the thermal reaction plate 9 is set sufficiently lower than room temperature, or if a unidirectional shape memory alloy or the like is used as the thermal response plate so that the heat dissipation contact does not return even after the power is cut off Alternatively, the heat dissipation contact may be a metal conductive contact. Further, in this case, the conductive contacts can be short-circuited at both ends of the heat generating portion of the heat generating structure. In this case, since the normal operating current bypasses the heat generating part, the self-heating in the high resistance heat generating part is suppressed, and it can be kept at a temperature sufficiently lower than the melting temperature together with the effect of heat dissipation. When the ambient temperature rises and the thermal response plate is inverted and the conductive contact is separated from the heat generating structure, the heat dissipation path is reduced, and in addition to reducing the heat dissipation path, the bypassed current is also applied to the heat generating part. The electric circuit can be interrupted by increasing the melting temperature.

  By using the protection device 101 together with the protection device 1, the protection device 101 can be restored by the thermal reaction plate before the electric circuit of the protection device 1 is melted against an overcurrent due to temporary restraint or the like. Protection is performed, and a permanent final protection such as a short circuit of the motor or an abnormally high temperature can be surely performed by fusing the electric circuit of the protection device 1.

  Next, a second embodiment of the present invention will be described with reference to FIGS. In the present embodiment, the same parts as those in the above-described embodiment are denoted by the same symbols, and detailed description thereof is omitted. The protective device 21 forms an airtight container with a metal housing 22 and a lid plate 23 as in the above-described embodiment. The cover plate 23 has one through hole 23B formed on one end side of the metal plate 23A, and a metal conductive terminal 24, which is one electrical terminal, is inserted into the through hole 23B. The glass plate 5 is an electrically insulating filler. Airtight and insulated. In the present embodiment, the metal plate 23A and the housing 22 constituting the sealed container are the other electrical terminal with respect to the conductive terminal 24 which is one electrical terminal. An insulator 6 is disposed on the inner surface of the glass 5 in an airtight container so as to be integrated with the glass 5 without a gap.

  One end of a conductive heat generating structure 27 is connected and fixed near the inner end of the airtight container of the conductive terminal 24, and the other end of the heat generating structure 27 is connected to the metal plate 23A by a connecting portion 27B. The heat generating structure 27 is provided with a heat generating portion 27A made of a metal having a melting temperature lower than that of the heat generating structure at a part of the electric circuit. When the heat generating portion 27A does not perform heat dissipation by the heat dissipation contact, It can be melted by self-heating with normal operating current. The heat generating portion 27A has an abutting portion 8A provided on the electrically insulating holding body 8 disposed between the metal plate 23A and an electric insulating member disposed at the tip of the thermally responsive plate 9 in the same manner as in the above example. The heat dissipation contact 10 is inserted.

  The thermally responsive plate 9 is formed into a shallow dish shape so as to reversely operate at a predetermined temperature, and is fixed via a thermally responsive plate support 11 fixed to the housing 22. The operating temperature is set so that it does not operate during normal operation of the electric compressor to be controlled and is reversed by a temperature rise such as when the ambient temperature is abnormally overheated.

  The protection device 21 is connected in series with the winding of the electric motor, and an operating current of the electric motor is supplied. The heat of the heat generating portion 27A of the heat generating structure 7 generated by the operating current flowing during normal operation of the electric motor is transferred from the heat radiation contact 10 to the housing 22 through the heat responsive plate 9, and by the connecting portion 27B and the holding body 8 with the metal plate. By being taken away by the metal plate 27, the heat generating portion 27A is always kept below the melting temperature and energization is continued.

  When the refrigerant temperature rises for some reason and reaches a dangerous temperature at the airtight terminal, for example, 150 ° C., the housing 22 and the metal plate 23A constituting the sealed container are also heated, so that the amount of heat released from the thermally responsive plate 9 becomes insufficient. The thermally responsive plate is heated to a predetermined operating temperature to reverse its curving direction, and the radiating contact 10 is separated from the heat generating structure 27.

  For this reason, the heat of the heat generating portion 27A loses the heat dissipation path and further rises in temperature due to self-heating, leading to fusing. Since the electric circuit is reliably interrupted in this way, the energization is stopped before the electric motor is burned out, and an accident such as a missing pin of the glass terminal can be prevented. In addition, since the heat radiation contact 10 is made of an electrically insulating material such as ceramics, the temperature of the thermally responsive plate 9 decreases after the current is cut off, and the energization is resumed in the melted heat generating portion even if the curving direction is restored. No.

  Also in the present embodiment, when a large current flows due to a short circuit or the like, it goes without saying that the heat generating structure is blown to cut off the electric circuit and stop energization thereafter.

  Similarly to the above-described embodiment, this protection device 21 is also used in combination with the conventional protection device 101 and the like, so that it can be protected against overcurrent due to temporary restraint and the like, as well as against permanent overheating and short circuit conditions. Final protection can be performed.

  According to the present invention, it is possible to completely cut off the electric circuit against overheating in the electric compressor without increasing current due to refrigerant gas leakage or the like, which has been difficult to protect in the past, and it is ensured before the electric motor burns out or the airtight terminal breaks. Final protection can be performed.

The longitudinal cross-sectional view which shows one Example of the protection apparatus for electric compressors of this invention AA sectional view of the protective device for the electric compressor of FIG. The longitudinal cross-sectional view which shows the final protection state of the protection apparatus for electric compressors of FIG. BB sectional view of the protective device for the electric compressor of FIG. The longitudinal cross-sectional view which shows 2nd Example of the protection apparatus for electric compressors of this invention CC sectional view of the protective device for the electric compressor of FIG. A longitudinal sectional view showing an example of a conventional protection device

Explanation of symbols

1, 2: 1: Protection device for electric compressor 2: Housing 3, 23: Cover plate 3A: Metal plates 4A, 4B, 24: Conductive terminal (electric terminal)
5: Glass 7, 27: Heat generating structure 7A, 27A: Heat generating portion 8: Holding body 9: Thermally responsive plate 10: Heat radiation contact 22: Housing (electric terminal)
23A: Metal plate (electrical terminal)

Claims (2)

A metal airtight container,
This hermetic container is provided with at least two electrical terminals,
At least one of the electrical terminals is a conductive terminal that is inserted into a hole formed in the hermetic container and is hermetically insulated and fixed.
Inside the airtight container, a heat generating structure that electrically connects the electrical terminals is arranged,
One end of the heat-responsive plate is fixed to the air-tight container so that heat can be exchanged with the air-tight container, and a heat radiation contact is disposed on the other end of the heat-responsive plate,
The heating structure is provided with a heating part having a particularly high resistance value,
When the heat dissipation contact comes into contact with the heat generating part, the heat of the heat generating part is transmitted to the airtight container through the heat dissipating part and the thermal reaction plate, and further released to the outside through the airtight container, so that the heat generating part is kept below the melting temperature. Sauce,
The thermal reaction plate is characterized in that when a predetermined temperature is reached, the direction of curvature is reversed, the heat dissipation part is separated from the heat generating part and the heat dissipation path of the heat generating part is reduced, so that the heat generating part melts by self-heating and the electric circuit is cut off. Protection device for electric compressors. A lid plate in which a conductive terminal is inserted into a hole drilled in a metal plate and hermetically insulated and fixed;
An airtight container is configured with a housing that tightly fixes the opening along the peripheral edge of the lid plate,
In this airtight container, a heat generating structure that electrically connects the metal plate of the lid plate and the conductive terminal is disposed,
One end of the heat-responsive plate, which has been drawn into a shallow dish shape, is fixed to the housing so that heat can be exchanged with the housing.
An electrically insulating holder is placed between the cover plate and the heat generating structure,
The heating structure is provided with a heating part having a particularly high resistance value,
By inserting this heat generating part with a heat dissipation contact and a holding body, the heat of the heat generating part is efficiently transmitted to the airtight container and released to the outside through the airtight container, so that the heat generating part is kept below the melting temperature. ,
The thermal reaction plate is characterized in that when a predetermined temperature is reached, the direction of curvature is reversed, the heat dissipation part is separated from the heat generating part and the heat dissipation path of the heat generating part is reduced, so that the heat generating part melts by self-heating and the electric circuit is cut off. Protection device for electric compressors.

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