JP2005327623A - Protective device for three phase motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the following problem:this protective device for a three phase motor has a contact mechanism by a stationary contact 6 and a movable contact 7 in a metallic enclosure, the movable contact 7 is disposed on a movable plate 8, the movable plate 8 is made rockable with a projecting piece part 8A supported by being inserted in the support hole of a support 10 as a fulcrum, the movable plate 8 is molded like a shallow plate and is driven by a thermally actuating board 12 reversing its bending direction by temperature to make break contacts, however, since the thermally actuating board 12 is operated by snapping action, there is possibility that arcing between the contacts continues by rebounding and bouncing caused by an impact at the time when making breaking the contacts. <P>SOLUTION: The projecting piece part 8A forming the fulcrum of the movable plate 8 is held by an elastic body 14 to always and elastically press it against the inner surface of the supporting hole, and thereby, kinetic energy in the action of the movable plate is elastically decreased. Therefore, generation and continuation of rebounding and bouncing are suppressed, and durability of the protective device can be extended by suppressing contact consumption caused by arcing. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a protection device for an electric motor with improved durability used for a hermetic electric compressor or the like.

  In an apparatus such as an air conditioner or a refrigerator / refrigerator, an electric compressor is used to compress and circulate refrigerant gas for heat exchange.

  Mainly these electric compressors are semi-hermetic electric compressors that can be disassembled and maintained by fully-sealed electric compressors and bolts that are completely sealed by welding etc. Hereinafter, these are collectively referred to as a hermetic electric compressor). An electric motor and a compressor are arranged in the storage containers of these hermetic electric compressors, and a passage through which the refrigerant flows is provided in the storage container. After the refrigerant is compressed to a high temperature and high pressure state by a compressor, the refrigerant exchanges heat through a heat exchanger and an expansion valve outside the storage container and is returned to the storage container again in a low temperature and low pressure state. In addition, the refrigerant flows around the motor, thereby taking heat from the motor and cooling it.

  In such a hermetic electric compressor, for example, when the motor is overloaded or rotation is restricted and overcurrent flows, the amount of heat generated by the motor winding increases, or the refrigerant leaks and the motor is sufficiently If it becomes impossible to cool down, the electric motor will be overheated, and eventually the electric motor may be burned out without proper protection.

  For this reason, various protection devices have been proposed in order to protect these electric motors. One of them is a protective device arranged in a refrigerant in a sealed storage container. Since this protective device can directly receive the heat of the refrigerant and the electric motor, it can obtain a quick response to the temperature change of the electric motor and the refrigerant. Various proposals have been made for the form of this protective device. Among them, as a protective device used for a three-phase hermetic electric compressor, for example, Japanese Patent Application Laid-Open No. 57-34623 and Japanese Patent Application Laid-Open No. 1-105435 “Three-phase thermal device”. "Protector" etc. are shown.

  In addition, the present applicant proposes a protection device used for this type of three-phase hermetic electric compressor, and in Japanese Patent Application Laid-Open No. 2004-44408, an electric compressor equipped with this three-phase motor protection device. The structure of was proposed. These protective devices are used for so-called Y-connected three-phase motors. In this case, the protective device 21 is connected to the middle point of the Y-connected coil of the three-phase motor 20 as shown in FIG. The Thus, energization of the motor can be cut off by opening the electric circuit in conjunction with the two sets of contacts.

  An example of the protective device 21 is shown in FIG. 8 which is a longitudinal sectional view of FIG. This protection device 21 is a protection device for use in a three-phase motor having a large current capacity, and has a sealed container composed of a metal housing 22 and a metal plate 23 as shown in the sectional view of FIG. Two conductive terminal pins 24 are airtightly fixed to the metal plate 23 through an electrically insulating filler such as glass 23A. Two connection terminals 25A or 25B are fixed to the outside of the sealed container of the conductive terminal pins 24 and the metal plate 23 to correspond to a large current, respectively, and serve as terminals of a contact mechanism inside the sealed container.

  Inside the sealed container, a fixed contact 26 is connected and fixed to the inner end of each conductive terminal pin 24, and a movable contact 27 is fixed on a movable plate 28, which is a heating resistor, opposite to the fixed contact. Yes. The movable plate 28 is disposed between the main portion 29A of the metal support 29 and the metal plate 23 substantially in parallel with the metal plate. The support 29 is provided with a leg 29B around the main part 29A, and the leg 29B is fixed to the metal plate 23 by welding. The movable plate 28 is adapted to move with a projecting piece 28A provided at the end opposite to the side to which the movable contact 27 is fixed as a fulcrum, and the projecting piece 28A is a leg 29B of the support 29. Is supported through a support hole 29C provided in one of the two.

  The two movable contacts 27 on the movable plate 28 are arranged so as to form an isosceles triangle having the protruding piece portion 28A of the movable plate as a vertex. The movable plate 28 is electrically connected to the metal plate 23 and the connection terminal 25B by being connected to the support 29 by a conductive wire 30 which is a conductor having sufficient flexibility. The movable plate 28 is not only a support for the movable contact 27 but also a heating resistor through which an operating current flows, and the connection position of the conductive wire 30 and the fixed position of each movable contact 27 form an equilateral triangle, respectively. The resistance value between them is aligned. The movable plate 28 has a resistance value and a heat generation position adjusted by providing a slit or the like in order to make heat transfer to a heat responsive plate, which will be described later, and operating characteristics as a protective device appropriate.

  One end of a thermally responsive plate 31 such as a bimetal is fixed to the support 29, and the movable end of the thermally responsive plate 31 is interlocked with the movable plate 28 by a connector 32, thereby interlocking with the movement of the thermally responsive plate. The contact is opened and closed. The thermally responsive plate 31 is obtained by squeezing and deforming a bimetal or the like into a shallow dish shape, and reverses or returns the bending direction with a sudden jump operation at a predetermined temperature. One end of the thermally responsive plate 31 is fixed to the support 29 by welding or the like. The movable end of the thermally responsive plate 31 is mechanically connected to the movable plate 28 by a connector 32 fixed to the distal end of the movable plate. It is only held to receive. Therefore, when the protective device 21 is energized, the current from the support 29 to the movable plate 28 mainly flows through the conductive wire 30 having a low resistance, and hardly flows through the thermally responsive plate 31 having a high contact resistance. Therefore, the thermally responsive plate 21 is heated not by self-heating due to current but mainly by the heat generated by the movable plate 28. In this way, when an overcurrent flows through the electric compressor or when the protective device is in an overheated state, the thermoresponsive plate 31 is operated, whereby the movable contact is separated from the fixed contact, and the electric circuit on the motor can be interrupted. An insulating plate 33 made of ceramic or the like is disposed between the metal plate 23 and the fixed contact 26 in order to protect the surface of the glass 23A from arc heat and scattered matter when the contact is opened and closed.

  This protective device is provided with a contact mechanism that drives a movable contact by deformation of a thermally responsive plate in a metal hermetic container. When the heat responsive plate is deformed due to heat generation or an increase in the ambient temperature, the contact can be opened to cut off the power supply.

JP-A-57-34623 JP-A-1-105435 JP-A-2004-44408

  The protection device 21 for the three-phase motor is relatively large and large as a whole so that it can withstand energization of a large current as compared with the protection devices of Patent Documents 1 and 2. Therefore, particularly when opening and closing the contacts, when the same opening / closing speed as that of the conventional one is given, impact during operation may be a problem.

  For example, when the opening / closing speed of the movable contact 27 is slow, the duration of arc discharge generated between the movable contact 27 and the fixed contact 26 is extended, and the contact is deteriorated. Therefore, the opening / closing time needs to be as short as possible. However, on the other hand, as a result of increasing the current capacity as a protective device, the movable contact becomes larger, and the movable plate on which the movable contact is arranged also increases the cross-sectional area in order to increase the strength and to pass a large current. The mass increases. Therefore, when the operation speed of the movable contact is increased, a large force is required when the contact is opened and returned.

  Here, when a part having a large mass is moved at a high speed, a large force is required to stop the movement. For this reason, when the contact is released, the movable plate collides with the support to cause a rebound that tries to contact the contact again. So-called bouncing is repeated. Whenever the contact is repeatedly opened and closed by rebounding or bouncing, arc discharge occurs between the contacts, and the contact deteriorates due to the high heat. Conventionally, the mass of the movable contact is relatively small, and such a repulsive force is suppressed by the force of a thermally responsive plate or the like that drives the movable contact, so that the occurrence and duration of rebound and bouncing have been minimized. However, if the mass of the moving part such as the movable contact or the movable plate increases as in this example, the repulsive force due to the collision cannot be suppressed only by the force of the thermally responsive plate, and as a result, these movements are difficult to converge.

  Further, in the structure of the protection device 21, when the thermally responsive plate returns, a collision between the movable plate and the support may occur together with a collision between the contacts, and vibration due to the collision may promote bouncing of the contacts. Next, rebound and bouncing including this phenomenon will be described with reference to FIG. As shown in FIG. 9A, the contact mechanism of the protective device closes the contacts by pressing the tip of the movable plate 28 with a thermally responsive plate 31 curved in the contact direction as shown in FIG. At this time, when the tip of the movable plate 28 is pushed, the protruding piece 28A, which is the opposite end with the contact portion of the movable contact 27 and the fixed contact 26 as a fulcrum, is provided above the support hole 29C provided in the support 29. It is pressed against the inner surface. When the heat responsive plate 31 is heated to the first predetermined temperature due to heat generation due to energization of overcurrent or a rise in refrigerant temperature, the heat responsive plate reverses its curving direction with a sudden jumping operation. When the thermally responsive plate 31 lifts the tip of the movable plate 28 via the connector 32 as shown in FIG. 9B, the movable contact 27 is separated from the fixed contact 26 and the electric circuit is interrupted. At this stage of separating the movable contact, only the tip of the movable plate 28 is pulled up, and the contact surface of the contact serving as a fulcrum is separated, so that the force pressing the protruding piece 28A is not applied. Further, when the tip of the movable plate is pulled up, the contact portion 28B provided on the surface opposite to the contact point of the moved movable plate 28 comes into contact with the support 29, and the projecting piece portion 28A is shown in FIG. ) To move downward and collide with the lower inner surface of the support hole 29C. At the same time, the entire movable plate 28 that has collided with the support 29 also undergoes rebound to return to the fixed contact side due to the reaction. Therefore, as shown in FIG. 9C, after the projecting piece 28A comes into contact with the support hole 29C, the movable plate moves further downward due to rebound, instantaneously closes the contacts, and again generates an arc between the contacts. There is a case.

  When the ambient temperature is lowered and the temperature of the thermally responsive plate 31 is lowered to the second predetermined temperature, the thermally responsive plate returns to its bending direction with a sudden jump operation. At this time, only the tip of the movable plate 28 is pushed down by the thermally responsive plate 31, and first contacts the contact as shown in FIG. 9D. Immediately after this contact, the pressure between the contacts is not sufficiently increased, so that bouncing due to reaction during contact is likely to occur. Further, the projecting piece 28A of the movable plate is bounced up with the contact point between the contacts as a fulcrum, and the projecting piece 28A collides with the upper inner surface of the support hole 29C when returning to the state of FIG. 9A. The slight vibrations caused by the shock at this time may cause a slight opening / closing between the contacts before the contact state is stabilized, thereby generating an arc between the contacts.

  As described above, when the number of contact opening / closing increases due to rebounding or bouncing, there is a problem in that contact deterioration due to arc increases, and as a result, durability performance as a protective device decreases. Therefore, there is a demand for a protective device that can suppress the opening and closing of the contact due to rebound and bouncing during the operation and return of the contact mechanism.

  Therefore, the protection device for a three-phase motor according to the present invention has a sealed container composed of a metal housing having an opening and a metal plate that closes the opening, and the metal plate has two through holes. Two conductive terminal pins are inserted and fixed through an insulating filler, two fixed contacts connected and fixed to the end of the conductive terminal pin protruding into the sealed container, a main portion, and A leg provided in the main part, and a support hole provided in the leg, and the leg disposed on the metal plate by fixing the leg to the metal plate; and the metal plate; Between the main part of the support body, it is arranged substantially in parallel with the metal plate, and has a projecting piece part inserted into a support hole of the support body at one end thereof, and swings around the projecting piece part as a fulcrum. The heating resistor approaching and separating from the metal plate, and the heating resistor Two movable contacts fixed to a portion facing the fixed contact, and the other end of the heating resistor to the other end of the projecting piece to transmit the reversal and return operations of the thermally responsive plate to the heating resistor And a conductor that electrically connects the support and the heating resistor, and the heat-responsive plate includes the heating resistor between the heating resistor and the main surface of the support. Is disposed substantially in parallel with the body, one of the ends is fixed to the support, the other is connected to the heating resistor via the connector, and the support hole of the support has a heating resistor An elastic body is disposed in a gap with the protruding piece portion of the body, and the protruding piece portion is elastically pressed against the inner surface of the support hole.

  By elastically pressing the part that becomes the fulcrum of operation of the heating resistor that is a movable plate against the inner surface of the support hole by an elastic body, the kinetic energy in the operation of the movable plate is elastically received and attenuated early. Can suppress the occurrence and persistence of rebound and bouncing. In addition, this configuration can suppress the collision of the movable plate in the support hole, and can suppress the vibration of the movable plate in particular when the contact is restored, thereby stabilizing the contact state. Therefore, the contact opening / closing phenomenon due to the collision at the time of contact opening / closing is converged at an early stage, and the wear of the contact due to the arc is suppressed, so that the durability performance as a protection device can be improved.

  In the contact mechanism of the protection device, the projecting piece portion serving as a fulcrum of the movable plate to which the movable contact is fixed is positioned by being elastically held by a leaf spring-like elastic plate, and sliding is accompanied when the movable plate is operated. By doing so, the kinetic energy of the movable plate is elastically absorbed and attenuated, and unnecessary movement of the movable plate in the support hole is suppressed. In addition, small vibrations caused by collisions when the contacts are opened and closed are attenuated by an elastic plate having a much lower natural frequency, and kinetic energy is also attenuated by sliding resistance.

  Next, specific examples of the protection device for a three-phase motor according to the present invention will be described with reference to the drawings. 1 is an external view of the present invention, FIG. 2 is a longitudinal sectional view, FIG. 3 is a partially enlarged view thereof, FIG. 4 is a sectional view taken along the line AA of FIG. 2, and FIG. An exploded perspective view shown in FIG. 6 and a structural diagram for explaining the operation of the contact mechanism are shown in FIG.

  This protection device 1 for a three-phase motor (hereinafter simply referred to as “protection device”) has a sealed container composed of a metal housing 2 and a metal plate 3 as in the above-described conventional example. The two conductive terminal pins 4 are hermetically insulated and fixed with an insulating filler such as glass 3A. Two connecting terminals 5A or 5B are fixed to the conductive terminal pin 4 and the metal plate 3, respectively, and serve as terminals of a contact mechanism inside the sealed container.

  The inside of the sealed container has a structure as shown in the sectional views of FIGS. 2 to 4 and the exploded perspective view of FIG. The fixed contact 6 is connected and fixed to the inner container end of each conductive terminal pin 4 via a fixed contact support 6A. The fixed contact support 6A is a metal conductor, and an insulation holder 9 made of an electrically insulating member such as ceramics is disposed between the fixed contact support 6A and the metal plate 3. . The fixed contact support 6A is supported on the back by an insulating holding body 9, so that electrical insulation between the fixed contact 6 and the metal plate 3 is maintained, and deflection due to the pressing force of the movable contact described later is prevented. It is possible to accurately define the position and the pressure between the contacts. The insulating holder 9 covers the surface of the glass 3A and can protect the surface of the glass from the heat of the arc and the scattered matter when the contacts are opened and closed.

  The movable contact 7 facing the fixed contact 6 is fixed on the movable plate 8. The movable plate 8 is a heating resistor in the electric circuit, and is disposed between the main portion 10A of the metal support 10 and the metal plate 3 in substantially parallel to the metal plate. The support body 10 is provided with a plurality of leg portions 10B around the main portion 10A, and is fixed by welding the leg portions 10B to the metal plate 3. The movable plate 8 is adapted to move with a projecting piece 8A provided on the side opposite to the side to which the movable contact 7 is fixed as a fulcrum. The projecting piece 8A is formed on the leg 10B of the support 10. One is supported through the support hole 10C provided as a through hole. Further, a stator 8B wider than the width of the support hole 10C is welded and fixed to the end of the projecting piece 8A to prevent the end from falling off. Further, on the back side of the end portion to which the movable contact 7 is fixed, there is provided an abutting portion 8C for abutting against the support 10 so as to provide a gap so as not to mechanically sandwich a thermal response plate described later when the contact mechanism is operated. ing.

  Further, as shown in FIG. 4, the two movable contacts 7 are arranged so as to form an isosceles triangle having the protruding piece 8A of the movable plate as a vertex. The movable plate 8 is electrically connected to the metal plate 3 and the connection terminal 5B by being connected to the support 10 by a conductive wire 11 which is a conductor having sufficient flexibility such as a stranded wire. The movable plate 8 is a movable body that moves the movable contact 7 and at the same time a heating element through which an operating current flows. The connection position of the conductive wire 11 and the fixed position of each movable contact 7 form an equilateral triangle, respectively. The resistance values between are aligned. In addition, the movable plate 8 is adjusted in resistance value and heat generation position by providing a slit or the like in order to make the heat transfer to a heat responsive plate, which will be described later, and the operation characteristics as a protective device appropriate.

  One end of a thermally responsive plate 12 such as a bimetal is fixed to the support 10 via a thermally responsive plate support 12A, and the movable end of the thermally responsive plate 12 is interlocked with the movable plate 8 by a connector 13. The contacts are opened and closed in conjunction with the movement of the thermal response plate. In addition, a slit 10E in which a screw 10D for adjusting the operation of the thermally responsive plate 12 is disposed is cut in the main portion 10A of the support 10, and the thermally responsive plate is moved by the screw 10D via the thermally responsive plate support 12A. The operating temperature is calibrated by pressing and adjusting the contact pressure. The heat responsive plate 12 is fixed to the support 10 via a heat responsive plate support 12A by a method such as welding. The tip of the heat responsive plate 12 is fixed to the movable plate 8 by a connector 13 fixed to the tip of the movable plate. It is only held to receive mechanically. On the other hand, since the conductive wire 11 is connected and fixed to both the movable plate 8 and the support 10 by welding, the energizing current to the protection device 1 is mainly generated through the conductive wire 11 having a low resistance. To the movable plate 8 and hardly flows to the thermally responsive plate 12 having a high contact resistance with the connector 13. Thus, the thermally responsive plate 12 is heated mainly by the heat generated by the movable plate 8, not by the self-heating caused by the current. In this way, when the overcurrent flows through the electric compressor or when the protective device is overheated due to an increase in ambient temperature, the movable contact is opened from the fixed contact by the movable plate interlocking with the movement of the thermally responsive plate 12 that reversely operates. The electric circuit on the electric motor can be interrupted.

  In this protective device 1, the protruding piece 8A of the movable plate 8 is inserted into the support hole 10C of the support 10 as described above, but the elastic plate has a leaf spring-like elasticity together with the end of the movable plate. A body 14 is arranged. By this elastic body 14, the protruding piece 8A is elastically brought into contact with the upper part of the inner surface of the support hole 10C. The elastic body 14 will be described with reference to FIG. 3 which is an enlarged view. The elastic body 14 has one end fixed to the support body 10, and in this embodiment, one end of a leaf spring which is elastically bent into a U shape. A fixed end 14A, which is further bent along the surface of the support, is fixed by welding. Further, the movable end 14B, which is the other end, is always in elastic contact with the lower surface of the movable plate 8 in the figure, but is not fixed.

  The elastic body 14 applies a pressing force in the upward direction to the movable plate 8, so that the projecting piece 8 </ b> A of the movable plate 8 is always in contact with the upper surface of the inner surface of the support hole 10 </ b> C. Here, since the movable plate 8 is elastically held, there is no substantial influence on the movement with the protruding piece of the movable plate as a fulcrum when the contact is opened or closed.

  Next, the function of this elastic body when the contacts are opened and closed will be described. Normally, the elastic body 14 is positioned reliably by pressing the movable plate 8 against the support 10 in a fixed direction. Further, even when vibration is applied from the device to be protected, the gap between the projecting piece 8A and the support hole 10C is substantially eliminated, so that the occurrence of rattling can be suppressed and the contact state of the contact can be stabilized.

  During the opening / closing operation of the contacts, the movable plate 8 is driven large and quickly by the sudden reversal or return of the thermally responsive plate 12. Therefore, the contacts can be opened and closed in a short time. On the other hand, when the contacts are opened and closed, the movable plate and the support or the movable contact and the fixed contact collide, so that so-called rebound and bouncing occur. In particular, when the mass of the movable plate or the like is large, the kinetic energy is also large, so that the occurrence of these phenomena is difficult to suppress, and the time until the generated bouncing converges becomes long. Therefore, the deterioration of the contact progresses due to the arc generated when the contact is opened and closed, and the durability performance as the protective device is lowered.

  Therefore, in the present invention, the protrusion of the movable plate is held by an elastic body, thereby preventing the protrusion from colliding in the support hole when the contact is opened and reducing the kinetic energy of the movable plate to rebound or bouncing. To converge early. Also, by pressing the projecting piece against the inner surface of the support hole in advance when returning to the contact point, it is possible to suppress the bounce caused by the collision of the projecting piece and the accompanying small vibrations and to attenuate the kinetic energy of the movable plate with the elastic plate. Rebound and bouncing are converged at an early stage by suppressing the vibration of the plate.

  This operation will be described with reference to FIG. As shown in FIG. 6A, the contact mechanism of the protective device closes the contacts by pressing the tip of the movable plate 8 with a thermally responsive plate 12 curved in the contact direction. At this time, the tip of the movable plate 8 is pushed, so that the protruding piece 8A which is the opposite end with the contact portion of the movable contact 7 and the fixed contact 6 as a fulcrum is provided on the support hole 10C provided in the support 10. It is pressed against the inner surface. The protruding piece 8A is also elastically pressed by the elastic body 14 at the same time.

  When the heat responsive plate 12 is heated to the first predetermined temperature due to heat generation due to overcurrent energization or a rise in refrigerant temperature, the heat responsive plate reverses its curving direction with a jumping action. When the thermally responsive plate 12 lifts the tip of the movable plate 8 through the connector 13 as shown in FIG. 6B, the movable contact 7 is separated from the fixed contact 6 and the electric circuit is interrupted. At this time, only the tip of the movable plate 8 is pulled up, and the contact surface of the contact point serving as a fulcrum is separated, so that the force due to the thermally responsive plate 12 is not applied to the protruding piece 8A. However, since the elastic body 14 elastically presses the movable plate, the projecting piece 8A continues to be pressed against the inner surface of the support hole 10C of the support.

  Here, when the contact is released, the abutting portion 8C of the movable plate 8 collides with the support 10, so that the rebound causes rebound due to the rebound of the movable plate. However, since the movable plate is held by the elastic body, the kinetic energy of the movable plate is rapidly attenuated. Further, when the abutting portion 8C of the movable plate 8 abuts on the support 9, the projecting piece portion 8A is rapidly pushed down with the abutting portion as a fulcrum. However, by receiving this force by the elastic body 14 disposed in the gap between the protruding piece 8A and the support hole 10C, the collision of the protruding piece 10C in the support hole and the accompanying small vibration can be suppressed. As a result, rebound converges early and arcing is minimized.

  When the ambient temperature falls and the temperature of the thermally responsive plate 12 decreases to the second predetermined temperature, the thermally responsive plate returns to its bending direction with a sudden jumping operation. At this time, the movable plate 8 is pushed down by the thermally responsive plate 12 and returns to the state shown in FIG. At this time, bouncing due to the collision between the contacts occurs, but the kinetic energy of the movable plate 8 is absorbed and attenuated by the elastic body 14, so that the bouncing converges early. Further, here, the thermally responsive plate 12 pushes down the tip of the movable plate, and the protruding piece 8A of the movable plate is lifted upward with the contact point between the contacts as a fulcrum. Since it is pressed against the inner surface, no movement such as a collision occurs, and the kinetic energy is attenuated and absorbed by the elastic body.

  As described above, in this embodiment, even when bouncing due to contact collision occurs, vibration due to collision of the projecting piece portion does not occur. Therefore, even when the pressure between the contacts is not sufficiently increased immediately after the contact is restored, contact between the contacts is not caused. Is relatively stable. In addition, since the kinetic energy of the movable plate is also attenuated by the elastic body, the occurrence and duration of bouncing can be minimized. As a result, arcing is also minimized and the durability of the contacts is improved.

  For example, without this elastic body, the movable plate causes rebound and bouncing on the movable contact side, and freely moves on the inside of the support hole on the projecting piece side, so that the movement of the movable plate is difficult to converge. In addition, the projecting piece also collides by moving up and down in the support hole during the operation of the movable plate, so that the vibration caused by this collision is transmitted to the movable contact side, particularly promoting bouncing and making the contact state between the contacts unstable. .

  On the other hand, in the present invention, the movable plate protruding piece is elastically held and positioned by the elastic body, so that the movement of the end of the movable plate is limited and the elastic body absorbs the vibration generated by the collision. The whole movement is easy to converge. Therefore, the convergence time of rebound and bouncing can be shortened. Further, since the movable plate and the elastic body are not fixed, friction is generated between the movable plate and the kinetic energy is consumed when the movable plate is swung. Therefore, the convergence time such as bouncing can be further shortened.

  As described above, according to the present invention, even in a protection device for a large current having a relatively large moving part mass, a transient phenomenon caused by a collision occurring at the time of contact opening / closing can be converged at an early stage. And the durability performance as a protective device can be extended. In this embodiment, the case where the fixed contact is connected and fixed to the conductive terminal pin via the fixed contact support has been described as an example. For example, the fixed contact is directly fixed to the conductive terminal pin as in the conventional example. Needless to say, the same effect can be obtained. Further, although the elastic body is fixed to the support, the fixing position may be on the movable plate side. In addition, by fixing the elastic body to both the movable plate and the support body, it is not slid, but the movement of the projecting piece portion in the left and right directions in the support hole can be regulated to make positioning more reliable. Furthermore, it is good also as a structure which presses and positions a protrusion piece part on an inner surface under a support hole with an elastic body.

  According to the protection device for a three-phase motor of the present invention, it is possible to suppress contact consumption due to an arc when the contact is opened and closed, and to improve durability as a protection device. For this reason, for example, when it is placed in a position where it cannot be easily replaced, such as inside a hermetic container of a hermetic type electric compressor, it is used when the energized current is large and the contact wear rate is relatively high when the contacts are opened and closed. Even if it exists, the function of protection object apparatuses, such as an electric compressor, can be maintained over a long term.

External view of protection device for three-phase motor of the present invention 1 is a longitudinal sectional view of the three-phase motor protection device of FIG. Partial enlarged view of FIG. AA cross-sectional arrow view of FIG. 1 is an exploded perspective view of the three-phase motor protection device of FIG. Structure diagram of protection device for three-phase motor in FIG. Longitudinal sectional view of a conventional protection device for a three-phase motor BB sectional view of FIG. 7 Structural diagram of the protection device for the three-phase motor of FIG. Circuit diagram for explaining attachment of protective device for three-phase motor to electric motor

Explanation of symbols

1: protection device for three-phase motor 2: housing 3: metal plate 4: conductive terminal pin 6: fixed contact 7: movable contact 8: movable plate 8A: protruding piece 8C: contact portion 10: support 10A: main portion 10B: Leg 10C: Support hole 11: Conductive wire 12: Thermally responsive plate 13: Connector 14: Elastic body

Claims (2)

In the protective device for a three-phase motor, which opens and closes the current path by a thermally responsive plate that reverses when the set temperature is reached and returns when the temperature falls below the set temperature,
It has a sealed container composed of a metal housing having an opening and a metal plate that closes the opening,
The metal plate has two through holes, and two conductive terminal pins are inserted and fixed through an insulating filler,
Two fixed contacts connected and fixed to the end of the conductive terminal pin protruding into the sealed container;
A main body and a leg provided in the main part, and a support hole is provided in the leg and the leg is fixed to the metal plate, and the support is disposed in the sealed container; and
Between the metal plate and the main part of the support body, it is disposed substantially in parallel with the metal plate, and has a projecting piece portion inserted into a support hole of the support body at one end thereof, A heating resistor that approaches and separates from the metal plate by swinging as a fulcrum;
Two movable contacts fixed to a portion of the heating resistor facing the fixed contact;
A connector provided at the other end portion of the heat generating resistor with respect to the projecting piece portion for transmitting the reversal and return operation of the thermally responsive plate to the heat generating resistor;
A conductor that electrically connects the support and the heating resistor;
The thermally responsive plate is disposed between the heat generating resistor and the main surface of the support substantially parallel to the heat generating resistor, one of both ends being fixed to the support, and the other being the connection Connected to the heating resistor through a child,
A protection device for a three-phase motor, wherein an elastic body is disposed in a gap between the support hole of the support body and the protruding piece portion of the heating resistor, and the protruding piece portion is pressed against the inner surface of the support hole. The protection device for a three-phase motor according to claim 1, wherein one of the elastic bodies arranged in the support hole is fixed to the support or the heating resistor, and the other is in contact.

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