JP2005098206A - Return delaying type protector and electric compressor protection system using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a protector which can delay a return time in accordance with a condition of an electric compressor. <P>SOLUTION: This protector 100 comprises: a switch including a first terminal 130, a second terminal 140, and a bimetallic disc 170 for opening/closing a current passage between the first and second terminals; an upper base 110 including an inner space in which at least one surface thereof being opened and storing the switch inside the inner space; and a lower base 200 including PTC, and first and second terminals 230 and 240 of positive characteristic thermistors electrically connected to electrode surfaces 220 and 222 of the PTC, respectively. The lower base 200 is constituted such that when the lower base is mounted to the upper base 110 so as to close the inner space of the upper base 110, the PTC is connected to the switch in parallel. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a protector using a thermally responsive element such as a bimetal disk, and more particularly to a protector that protects an internal motor attached to the outside of a hermetic electric compressor (compressor).

  2. Description of the Related Art A protector is used that shuts down an electric compressor circuit in response to an overcurrent flowing to a motor or an ambient temperature when an abnormal state such as an overload operation or a motor restraint operation occurs in a hermetic electric compressor. As shown in FIG. 11A, the protector 1 includes a base 10 molded with an insulating resin, a pair of terminals 20 and 22 attached to the base 10, a bimetal disk 30, and a heater 40. The The pair of terminals 20 and 22 have fixed contacts 24 and 26 at predetermined positions in the base 10, respectively. The bimetal disc 30 is formed with movable contacts 34 and 36 that are in contact with or isolated from the fixed contacts 24 and 26, and the central portion thereof is fixed to the base 10 by an adjuster screw 32, and in response to an energized current. It generates heat and performs a snap action. In the protector 1, the heater 40 is not necessarily essential, but here, one end of the heater 40 is electrically connected to the fixed contact 26 and the other end is the external terminal 42 so that the heater 40 is connected in series with the bimetal disk 30. (See FIG. 11B).

  The electric compressor is provided with an airtight terminal or a fusing pin (C: common terminal, M: main winding terminal, S: auxiliary winding terminal) which is an interface for supplying electric power to the motor windings. . As shown in FIG. 11B, the protector 1 has a terminal 20 connected to a common terminal C of the motor and a terminal 42 connected to an AC power source. When the motor is overloaded or restrained, an overcurrent flows through the bimetal disk 30, thereby heating the bimetal disk 30 and performing a snap action operation, and the movable contacts 34 and 36 are separated from the fixed contacts 22 and 24. The circuit is interrupted, which protects the motor windings from burning. Furthermore, the bimetal disk 30 can respond to not only the overcurrent but also the heat generated from the motor of the electric compressor, etc., and can interrupt the circuit.

  Further, as shown in FIG. 12, the protector 50 shown in Patent Document 1 is provided with a thermostat-structured bimetal switch 60 and a fail-safe current fuse 70 on the lower base 12 with respect to the protector 1 described above. The heater 40 is connected in series. The temperature of the electric compressor may rise when refrigerant gas leaks, etc. In such a case, it is difficult to detect an abnormality due to overcurrent, so the operating temperature of the bimetal switch 60 should be adjusted appropriately. Then, the temperature abnormality is detected. The current fuse 70 interrupts the circuit in response to an abnormal current that flows when the bimetal switch 30 becomes inoperable due to contact welding or the like, or when a short circuit between the windings occurs.

JP-A-10-308150

  However, the conventional protectors have the following problems. In the case of a protector externally attached to the outer portion of the electric compressor, since the distance from the motor winding, which is a heat source, to the protector is large, it takes time to transfer the heat. For this reason, in the operation test performed on the electric compressor, when a voltage or current exceeding the rating is applied when the motor is restrained (hereinafter referred to as operation test 1), the operation time and the recovery time of the protector are both Shorter. That is, only the response speed to the overcurrent is increased. Further, when a voltage / current less than the rating is applied when the motor is restrained (hereinafter referred to as operation test 2), the operation time of the protector is long and the recovery time is short. Before the temperature of the outer shell (shell) where the protector is attached rises, the winding temperature inside the electric compressor rises rapidly, and before the protector follows, the winding itself reaches the insulation breakdown heat resistance temperature or higher. If this happens, a short circuit will occur between the windings, and due to further heat generation and melting of the airtight terminal glass part due to further large current, the inside of the electric compressor will be in a high pressure state, the airtight terminal will blow off, and the refrigerant will blow out. There is a problem.

  The restraint protection of the electric compressor is based on the winding temperature and the outer temperature of the electric compressor under the conditions of the rated voltage of the operation test 1 and the low voltage of the operation test 2 (voltage 15 to 20% lower than the rated voltage). Must be kept within the limit temperature set by In particular, in the operation test 2, the protector is required to have an operation time of several seconds and a long recovery time of several tens of seconds to several minutes from the viewpoint of protecting the winding from burning. On the other hand, in the operation test 1, since the rotor restraint current becomes larger than that in the operation test 2, the operation time of the protector is shortened, and the winding temperature is lower than that in the operation test 2, so the outer temperature of the electric compressor is also lowered. The return time tends to be shorter. Therefore, in the conventional protector as shown in FIG. 11 and FIG. 12, for example, in a 15-day continuous test defined in the UL safety standard, the bimetal disk may exceed the guaranteed number of operations. It is necessary to select the protector again.

  The recovery time of the protector shown in FIGS. 11 and 12 is greatly affected by the recovery temperature of the bimetal disk and the ambient temperature, and the protector selected during the 15-day continuous rotor restraint test defined by safety standards and the like. If the matching with the electric compressor is poor, the operation life of the bimetal disk may be exceeded, and the continuous test operation for 15 days may not be executed.

  In general, in the 15-day continuous rotor restraint test, in order to reduce the number of times the protector operates, it is effective to lower the recovery temperature of the bimetal disk to increase the recovery time, but the operating temperature of the bimetal disk If the difference between the return temperature and the return temperature becomes too large, the number of mechanical operation lifetimes of the bimetal disk is reduced, and as a result, the rotor restraint test for 15 days cannot be endured.

  In the case of the protector shown in FIG. 11, it is necessary to select a bimetal disk and a heater according to each electric compressor that uses the rotor restraint protection characteristic and the overload protection characteristic, and there are almost the same number of combinations as the electric compressor. Due to the presence of protectors, it is difficult to have an adequate inventory of parts and finished products, and sometimes the delivery times requested by customers are not satisfied.

  In addition, since the protector shown in FIG. 11 must satisfy the rotor restraint and the overload protection with a single bimetal disk, the operating temperature of the bimetal disk must be set to about 140 to 160 degrees C. The operating temperature of about 120 degrees necessary for the gas leak operation cannot be obtained.

  On the other hand, the protector shown in FIG. 12 can solve such a problem, but the structure becomes complicated, the number of parts increases, the assembly process and management items increase, and these are the causes of the cost increase. It has become.

  In the protector shown in FIG. 12, the bimetal disk for refrigerant gas leakage operation protection may operate before the bimetal disk 1 when measuring the overload protection characteristic. Is very difficult, and it may take time and money to recreate the sample.

  Finally, since the conventional external protector has a distance from the heat source as described above, especially in the case of a scroll type compressor, the distance is further increased, so that it is suitable for abnormal operation of the electric compressor. In some cases, it may be difficult to protect and therefore a relatively expensive internal protector must be used.

An object of the present invention is to solve the above-mentioned conventional problems and to provide a protector that can delay the return time of a bimetal disk in accordance with the state of the electric compressor.
Another object of the present invention is to provide a protector that can withstand the required operational tests and has an improved operational lifetime.
Another object of the present invention is to provide a protector capable of appropriately detecting and protecting an abnormal state of an electric compressor.
Another object of the present invention is to provide a low-cost protector with a small number of parts.

  The protector according to the present invention includes a first terminal, a second terminal, a switch including a bimetal disk for opening and closing a current path between the first and second terminals, and an internal space where at least one surface is open. A second member including a first member for accommodating the switch in the internal space, a positive temperature coefficient thermistor, and first and second positive temperature coefficient thermistor terminals electrically connected to each electrode surface of the positive temperature coefficient thermistor. The second member is attached to the first member so as to close the internal space of the first member, and the first and second positive characteristic thermistor terminals are the first and second terminals, respectively. It is electrically connected to the terminal.

  Preferably, the first and second terminals include first and second fixed contacts, respectively, and the bimetal disk has first and second movable contacts that are in contact with or not in contact with the first and second fixed contacts. In addition, when the bimetal disk that generates heat in response to the current applied between the first and second terminals is reversed, the first and second movable contacts are separated from the first and second fixed contacts.

  Preferably, when the first and second movable contacts of the bimetal disk are separated from the first and second fixed contacts, a current is supplied to the positive temperature coefficient thermistor via the first and second positive temperature coefficient thermistor element terminals. The positive temperature coefficient thermistor is heated. Due to the heat generated by the positive temperature coefficient thermistor, the ambient temperature in the internal space rises, and the recovery time of the bimetal disk is delayed.

  Preferably, the first member has one circular surface and a side surface connected to the one surface, the inner surface is formed by the one surface and the side surface, and a surface facing the one surface is open. And a base member formed by molding an insulating resin, and a plurality of openings communicating with the internal space are formed on the one surface, and the second member has a circular shape so as to correspond to the open surface of the first member When the second member is attached to the open surface of the first member, the internal space is substantially sealed, and the first and second terminals and the first member The second positive characteristic thermistor terminal protrudes from the corresponding opening.

  Preferably, the positive temperature coefficient thermistor (PTC) has a first electrode surface and a second electrode surface opposite to the first electrode surface, and the first and second electrode surfaces are mounted on the second member. The first and second positive temperature coefficient thermistor terminals are arranged in parallel with the surface, and the first and second contact portions that are in electrical contact with the first and second electrode surfaces, and the first And first and second terminal portions extending from the second contact portion, and the first and second terminal portions are electrically connected to the first and second terminals, respectively, and project from the opening. . The positive temperature coefficient thermistor is preferably arranged so as to face the bimetal disk, so that the heat of the positive temperature coefficient thermistor is preferably coupled to the bimetal disk in the internal space.

  Further, the switch may include a heater connected in series with the first or second terminal. The heater generates heat due to the applied current, transmits this heat to the bimetal disk, and promotes the inversion of the bimetal disk.

  Furthermore, the electric compressor protection system of the present invention includes a protector having the above-described features, and a plurality of airtight terminals that include a motor and a compressor in the housing and function as an external interface with the motor. The protector is electrically connected to a predetermined hermetic terminal to protect the motor.

  Preferably, when the bimetal disk reverses and the current path between the contacts is interrupted, the positive temperature coefficient thermistor generates heat and delays the return time of the bimetal disk.

  According to the present invention, when the bimetal disk is reversed and the current path is interrupted, the recovery time of the bimetal disk can be delayed by the heat generated by the positive temperature coefficient thermistor. Therefore, an appropriate test can be performed within the operation compensation of the bimetal disk. Furthermore, by delaying the return time, a rapid increase in the temperature of the motor winding of the electric compressor can be suppressed, and the winding can be prevented from being burned out. In addition, there is no need to change the mechanical properties of the bimetal disk itself in order to delay the recovery time of the bimetal disk, so the life of the bimetal disk is not shortened, and the recovery time is delayed due to the small number of parts. Therefore, it is possible to manufacture the protector at a low cost.

  The protector according to the present invention is preferably used by being externally attached to a fusite pin of an electric compressor. Embodiments will be described below with reference to the drawings.

  1 is an exploded perspective view of an upper base of a protector according to a first embodiment of the present invention, FIG. 2A is a plan view of the protector, and FIG. 2B is a cross-sectional view taken along line X1-X1. The protector 100 includes an upper base 110 formed by molding an insulating resin, and a lower base 200 (see FIG. 3) assembled to the upper base 110. The upper base 110 has a circular surface 111 and an outer peripheral surface 112 that forms a side surface of the surface 111, and a cylindrical space is formed inside by these surfaces. The side facing the surface 111 is an open surface 113.

  On the surface 111 of the upper base 110, a plurality of slot-shaped openings 114, 115, 116, and 117 communicating with the internal space are formed. The openings 114, 115, 116, 117 are arranged at intervals of 90 degrees, and a through hole 118 for an adjuster screw is formed at the center thereof. The upper base 110 accommodates a bimetal switch 120 for opening and closing a circuit in response to an overcurrent and an ambient temperature that are passed during overload operation or restraint operation. The bimetal switch 120 includes a pair of first and second terminals 130 and 140 including fixed contacts 132 and 142, a heater 150, a third terminal 160 connected to the heater 150, and a bimetal disk, as in the past. 170 and an adjuster screw 180 for finely adjusting the operating temperature of the bimetal disc 170.

  The first and second terminals 130 and 140 are made of a conductive metal and have fixed contacts 132 and 142 that provide a substantially flat surface, and terminals that are bent from the fixed contacts 132 and 142 and extend substantially perpendicularly therefrom. Parts 134 and 144. The first terminal 130 further includes a terminal portion 136 that is integral with and has the same shape as the terminal portion 134, and the terminal portion 136 is bent at an angle of approximately 90 degrees with respect to the terminal portion 134. When the first and second terminals 130 and 140 are mounted in the upper base 110, the terminal portions 134 and 144 protrude outward from the opposing openings 114 and 116, and the terminal portion 136 protrudes from the opening 115 and is fixed. The contacts 132 and 142 are positioned at predetermined positions on the upper base 110.

  The heater 150 is made of a nickel chromium alloy or the like, and is bent so as to fit in a groove formed in the center of the upper base 110. One end 152 of the heater 150 is connected to the second terminal 140 by welding, and the other end 154 is connected to the connection 162 of the third terminal 160 by welding. The third terminal 160 includes a terminal portion 164 that is bent substantially vertically from the connection portion 162, and the terminal portion 164 protrudes from the opening 117.

  The bimetal disc 170 has a substantially disk shape, and protrusions are formed at opposite ends thereof. Movable contacts 172 and 174 are welded to each protrusion by welding or the like. Further, a through-hole 176 and a plurality of slits extending radially from the through-hole 176 are formed in the center of the bimetal disc 170. When the bimetal disc 170 is mounted in the upper base 110, the through hole 176 is aligned with the central through hole 118 of the upper base 110, and the adjuster screw 180 is mounted through the through holes 118 and 176. At this time, the movable contacts 172 and 174 are brought into contact with the fixed contacts 132 and 142 with a constant contact pressure, and the operating temperature of the bimetal disk 170 is finely adjusted by adjusting the adjuster screw 180. In this embodiment, the inversion temperature of the bimetal disk 170 is about 155 degrees, and the return temperature is adjusted to about 69 degrees.

  The main feature of the protector of the present invention is that the lower base 200 includes a positive temperature coefficient thermistor (hereinafter referred to as PTC) for delaying the return time of the bimetal switch 120. 3A is a front view of the lower base, and FIG. 3B is a cross-sectional view of the lower base taken along line X2-X2.

  The lower base 200 includes an insulating resin molded in a disc shape so as to be fitted to the open surface 113 of the upper base 110. A circular PTC and fourth and fifth terminals 230 and 240 electrically connected to the PTC are attached to the mounting surface 210 of the lower base 200. The PTC has opposing electrode surfaces 220 and 222, and as is well known, when a voltage is applied to the electrode surfaces 220 and 222 at a low temperature, ie, lower than the Curie temperature, it acts as a low resistance element, and by self-energization When the temperature rises and exceeds the Curie temperature, it functions as a high resistance element. The PTC of this example has a Curie temperature set to about 70 degrees, and is about 5K ohms at a lower temperature, and about 10K ohms at a higher temperature.

  The fourth terminal 230 is a metal member processed into an L-shape as shown in FIG. 4, and a contact portion 232 extending in the horizontal direction and extending by being bent substantially vertically from the contact portion 232. Terminal portion 236. The contact portion 230 extends with a substantially uniform width and includes a protruding surface 232a protruding in the middle thereof. As shown in FIG. 3, the projecting surface 232 a is in contact with the approximate center of the electrode surface 220 of the PTC. Wide portions 234 extending in the width direction are formed from both sides of the base portion of the contact portion 232. Preferably, the wide portion 234 is fixed to the mounting surface 210 of the lower base 200 by insert molding.

  As shown in FIG. 5, the fifth terminal 240 is a metal member processed into an L-shape, and includes a contact portion 242 extending in the horizontal direction and a terminal portion 244 extending by being bent in a substantially vertical direction therefrom. And have. The contact portion 242 has a projecting surface 242a that is offset through a step at the tip, and a pair of leg portions 246 that are bent substantially vertically downward on both sides of the base portion of the contact portion 242. Is formed.

  As shown in FIGS. 3A and 3B, the electrode surface 220 comes into contact with the protruding surface 232 a of the contact portion 232 from the state where the fourth terminal 230 is fixed on the mounting surface 210 of the lower base 200. The fifth terminal 240 is attached so that the protruding surface 242a of the contact portion 242 contacts the electrode surface 222 of the PTC. Preferably, the leg portion 246 of the fifth terminal can be fitted and fixed in a recess formed in advance on the mounting surface 210 of the lower base 200. It is also possible to weld the contact portions 232 and 242 to the electrode surfaces 220 and 222. When the fifth terminal 240 is attached to the lower base 200, the contact portions 232 and 242 preferably press the electrode surfaces 2220 and 222 of the PTC with a constant contact pressure.

  The lower base 200 to which the fourth and fifth terminals 230 and 240 and the PTC are attached is mounted so as to close the open surface 113 of the upper base 110. The state at this time is shown in FIG. A flange portion 212 is formed on the outer periphery of the lower base 200, and preferably the flange portion 212 is joined to a flange portion 113 a formed on the open surface 113 of the upper base 110. The terminal portions 236 and 244 of the fourth and fifth terminals 230 and 240 are inserted into the openings 115 and 117 of the upper base 110. In the opening 115, the terminal portion 236 is bonded to the terminal portion 136 of the first terminal 130 by welding or the like, and in the opening 117, the terminal portion 244 is welded to the terminal portion 164 of the third terminal 160 by welding or the like. Thus, as shown in FIG. 7, the heater 150 is connected in series with the bimetal disk 170, and a parallel circuit of these and the PTC is configured. Further, since the open surface 113 of the upper base 110 is sealed by the lower base 200, the internal space of the upper base 110 has a substantially sealed structure, and the PTC is close to the bimetal disc 170 in the sealed structure. Arranged.

  FIG. 8 shows a scroll type electric compressor 300 to which the protector 100 according to the present embodiment is attached. The scroll-type electric compressor 300 includes a motor 320 and a compressor 330 in a housing shell 310, and the shell is filled with refrigerant gas compressed by the compressor. Unlike a normal electric compressor, the positions of the motor 320 and the compressor 330 are opposite. In the upper part 340 of the shell 310, a refrigerant gas discharge pipe 350 is formed, and a plurality of hermetic terminals (fusite pins) sealed with glass are formed adjacent thereto. The protector 100 is fixed by a spring or the like of the dedicated cover 360 so as to be connected in series with an airtight terminal connected to the common terminal of the motor.

  Next, operation | movement of the protector of a present Example is demonstrated. During the normal operation of the electric compressor 300, the bimetal switch 120 is closed, and the current supplied from the AC power supply is supplied to the motor via the bimetal disc 170 and the heater 150. At this time, since the difference in specific resistance between the PTC and the bimetal disk 170 is very large, power is not supplied to the PTC side, and therefore the PTC does not generate heat.

  As an abnormal state of the electric compressor 300, for example, when the rotor is restrained, an overcurrent larger than that during normal operation flows. The bimetal disk 170 rises in temperature when energized, and when it reaches about 155 degrees, it performs a reversing operation, the movable contacts 172 and 174 are isolated from the fixed contacts 132 and 142, and the current path between the contacts becomes non-conductive. Along with this, current supply to the PTC side is started, and the PTC rises to about 100 degrees by self-heating. Since the bimetal disk 170 and the PTC are accommodated in the sealed space of the upper base 110 and the lower base 200, the ambient temperature of the bimetal disk 170 is efficiently raised by self-heating of the PTC. Preferably, the cooling rate of the bimetal disk 170 is delayed by making the heat generation temperature of the PTC higher than the return temperature of the bimetal disk. Thereafter, the temperature of the housing shell 310 rises due to the heat of the motor winding and is thermally conducted to the upper part 340. Also, the temperature in the cover 360 rises due to the heat generated by the PTC, and this temperature is the return temperature of the bimetal disk. The temperature is raised later to a slightly higher temperature. As a result, the ambient temperature of the bimetal disc 170 becomes higher than the return temperature for a certain period of time, and the bimetal disc 170 does not return during that time.

  FIG. 9 shows the protection characteristics when the motor restraint protection test is performed, the restraint current (A), voltage (V), and temperature (° C.) are plotted on the vertical axis, and the test time (seconds) is plotted on the horizontal axis. Yes. FIG. 9A shows the characteristics when the protector according to the present embodiment is used, and FIG. 9B shows the characteristics when the conventional protector is used. When the protector according to this embodiment is used, the recovery time of the bimetal switch is delayed, so the temperature rise of the main winding and the starting winding should be kept below the maximum allowable winding temperature of 160 degrees for a long time of the test. I was able to. The maximum temperature of the main winding at this time was 84.4 degrees. Thereby, it is possible to appropriately prevent the winding of the motor from being burned out, and to improve the life of the motor by reducing the number of trips of the bimetal disk. In contrast, when a conventional protector is used, the bimetal disk recovery time is short, so the bimetal switch trips many times within a very short time (500 seconds in the figure). The temperature of the coil rises rapidly, and the maximum allowable temperature of the winding is quickly reached. Furthermore, since the bimetal switch trips many times within a short time, the guaranteed number of operations of the bimetal disk is quickly exceeded, in other words, the life of the bimetal disk is shortened.

  Next, a second embodiment of the present invention will be described. As shown in FIG. 10, the protector according to the second embodiment includes the first current fuse 400 between the PTC and the first terminal 130, and the second current between the heater 150 and the second terminal 140. Current fuse 410 is formed. The first fuse 400 can be obtained, for example, by forming a portion having a relatively small cross-sectional area between the terminal portion 134 and the terminal portion 136 of the first terminal shown in FIG. The second fuse 410 can be obtained by relatively reducing the sectional area of a part of the terminal portion 164 of the third terminal 160. The first and second current fuses 400 and 410 are the first and second current fuses 400 and 410 when the PTC causes thermal runaway or the like for some reason, or when the contact of the bimetal disk is welded and the electric compressor cannot be protected. The second current fuse 400, 410 blows in response to the overcurrent and opens the circuit. Thereby, it is possible to prevent an accident such as the airtight terminal flying.

  As described above, according to the present embodiment, when the distance between the heat source and the protector is long like the scroll type electric compressor, in order to suppress the temperature of the winding to the limit temperature or less from the experimental results so far, A short operation time and a long recovery time of the bimetal switch are required. In order to achieve this, a so-called internal protector is generally used due to the characteristics of its operating characteristics, but the protector of this embodiment has a low cost configuration and is scrolled while being externally attached to the outer shell of the housing shell. The type electric compressor can be appropriately protected. Furthermore, in the case of the protector of the present embodiment, the return time is sufficiently longer than that of the conventional protector or internal protector, so that an excessive temperature rise of the winding can be suppressed, and further, the stable winding The temperature is lower than using a conventional protector, and rotor restraint protection can be performed safely.

  Since the PTC can be used to delay the recovery time of the protector, it is not necessary to increase the hysteresis of the operating temperature and recovery temperature of the bimetal switch, and it is highly reliable without degrading the mechanical life of the bimetallic disk. A protector having a rotor restraint protection characteristic can be obtained.

  Due to the heat generated by the PTC, it is possible to extend the recovery time of the protector by 3 to 5 times compared to the conventional protector, and this makes it possible to perform a 15-day continuous rotor restraint protection test as defined by safety standards such as UL. In the conventional external protector, the number of operation of the protector is about 10,000 times, but this can be suppressed to about 2000 to 5000 times, and as a result, the reliability of the electric compressor and the protector is improved. . Further, by arbitrarily setting the amount of heat generated by the PTC, it is possible to further reduce the number of operations and improve the operating life of the protector.

  Furthermore, the protector of this embodiment has the same recovery temperature of the bimetal disk as the conventional one and can significantly extend the recovery time, so that the rotor restraint protection can be achieved without being restricted by strict operating time characteristics. For those with similar load protection characteristics, one type of protector can protect several types of electric compressors with different rotor restraint currents. In addition, the time and cost for selecting a protector by the manufacturer of the electric compressor or the air conditioner can be greatly reduced, thereby reducing time and cost. Furthermore, for protector manufacturers, the number of parts can be reduced, the risk of having excess inventory can be avoided, and delivery in just-in-time can be realized easily. .

  For rotor restraint protection of electric compressors, bimetal discs can be selected and adjusted with some margin, so the operating temperature of bimetal discs must be set around 140-160 degrees like conventional protectors. In fact, it is theoretically possible to reduce the temperature to around 120 degrees, which is the operating temperature for the purpose of protecting the refrigerant gas leakage operation based on the overload protection characteristics. In the conventional protector, a thermostat type bimetal disk is added. However, the protector of this embodiment can reduce the cost with a simpler configuration by removing the thermostat type bimetal disk.

  When the bimetal disk does not operate, the difference between the specific resistances of the bimetal disk and the PTC is so large that almost no current flows to the PTC side. Therefore, the current sensitivity required for the protector itself (rotor constraint protection), current As for the temperature sensitivity (overload protection), there is no difference from the conventional protector, so the current protector can be smoothly replaced with the protector of the present embodiment.

  Rotor restraint protection at room temperature or below, for example, 0 degrees, is a severe test condition for the protector, and the conventional external protector has such a low ambient temperature, so that the return time is short, and the outer shell of the electric compressor and Before the protector atmosphere became saturated, the winding reached the limit temperature or more, and there was a case where sufficient protection could not be performed. However, in the protector of this example, the protector body was heated by the heat generated by the PTC. Therefore, the temperature in the cover in which the protector is installed rises quickly to the vicinity of the return temperature of the protector without being influenced by the environmental temperature so much, and the winding can be protected without any problem.

  If the rotor restraint protection at a low voltage, for example, 30% lower than the rating can be satisfied, the same protection at the rated voltage can be performed. Therefore, the low voltage rotor restraint protection condition can be satisfied. By selecting the protector, mistakes in selecting the protector can be almost eliminated, and the development period can be shortened and, consequently, the cost can be reduced.

  Although the preferred embodiment of the present invention has been described in detail above, the present invention is not limited to the specific embodiment, and various modifications are possible within the scope of the gist of the present invention described in the claims. Can be changed. For example, in the first and second embodiments, the heater 150 is mounted in the upper base 110, but the heater 150 is not necessarily required. When the heater is not used, the third terminal 160 is electrically connected so as to have the same polarity as the second terminal 140. For example, the third terminal 160 and the second terminal 140 may be integrally formed.

  The protector according to the present invention can be used as an external type of an electric compressor shell. In particular, the present invention can be applied to a large output compressor in which an internal protector is used.

It is a disassembled perspective view of the upper base of the protector which concerns on 1st Example of this invention. 2A is a plan view of the upper base, and FIG. 2B is a cross-sectional view taken along line X1-X1. FIG. 3A is a plan view of the lower base of the protector according to the first embodiment, and FIG. 3B is a cross-sectional view taken along line X2-X2. 4A is a top view of the fourth terminal, FIG. 4B is a front view of the fourth terminal, and FIG. 4C is a side view of the fourth terminal. FIG. 5A is a top view of the fifth terminal, FIG. 5B is a front view of the fifth terminal, and FIG. 5C is a side view of the fifth terminal. It is sectional drawing when a lower base is assembled | attached to the upper base. It is a figure which shows the circuit structure of the protector which concerns on a 1st Example. It is a figure which shows schematic structure of a scroll type electric compressor. FIG. 9A shows the rotor restraint protection characteristic by the protector of the first embodiment, and FIG. 9B shows the rotor restraint protection characteristic by the conventional protector. It is a figure which shows the circuit structure of the protector which concerns on a 2nd Example. It is a figure which shows the structural example of the conventional protector. It is a figure which shows the structural example of the other conventional protector.

Explanation of symbols

100: protector 110: upper base 120: bimetal switch 130: first terminal 140: second terminal 150: heater 160: third terminal 170: bimetal disk 180: adjuster screw 200: lower base 210: mounting surface 220 222: electrode surface 230: fourth terminal 240: fifth terminal 300: electric compressor

Claims (10)

A switch including a first terminal, a second terminal, a bimetal disk for opening and closing a current path between the first and second terminals;
A first member that includes an internal space that is open on at least one surface, and that accommodates the switch in the internal space;
A positive characteristic thermistor, and a second member including first and second positive characteristic thermistor terminals electrically connected to the respective electrode surfaces of the positive characteristic thermistor,
The second member is attached to the first member so as to close the internal space of the first member, and the first and second positive temperature coefficient thermistor terminals are electrically connected to the first and second terminals, respectively. Connected, protector. The first and second terminals include first and second fixed contacts, respectively, and the bimetal disk includes first and second movable contacts that are in contact with or not in contact with the first and second fixed contacts, and The first and second movable contacts are spaced apart from the first and second fixed contacts when the bimetallic disc that generates heat in response to a current applied between the first and second terminals is reversed. The protector described in 1. When the first and second movable contacts are separated from the first and second fixed contacts, current is supplied to the positive thermistor via the first and second positive thermistor terminals, and the positive thermistor generates heat. The protector according to claim 1 or 2. The protector according to claim 1, 2, or 3, wherein the atmospheric temperature in the internal space is raised by heat generation of the positive temperature coefficient thermistor, and the recovery time of the bimetal disk is delayed. The first member has a circular surface and a side surface connected to the one surface, an internal space is formed by the one surface and the side surface, and a surface facing the one surface is open. Including a base member molded with resin, the one surface is formed with a plurality of openings communicating with the internal space, and the second member is molded in a circular shape so as to correspond to the open surface of the first member When the second member is attached to the open surface of the first member, the internal space is substantially sealed, and the first and second terminals and the first and second terminals are included. The protector according to claim 1, 2, 3, or 4, wherein two positive temperature coefficient thermistor terminals protrude from corresponding openings. The positive temperature coefficient thermistor has a first electrode surface and a second electrode surface facing the first electrode surface, and the first and second electrode surfaces are parallel to the mounting surface of the second member. The first and second positive temperature coefficient thermistor terminals are electrically connected to the first and second electrode surfaces, and the first and second contact points. And a first terminal portion extending from the first portion, the first terminal portion being electrically connected to the first terminal and the second terminal, respectively, and protruding from the opening. Item 7. The protector according to Item 5. The positive temperature coefficient thermistor is disposed so as to face the bimetal disk substantially parallel to the second member when the second member is attached to the first member. The protector described in 1. The protector according to claim 1, 2, 3, 4, 5 or 6, wherein the switch further comprises a heater connected in series with the first or second terminal. The protector according to any one of claims 1 to 8,
An electric compressor including a motor and a compressor in the housing and having a plurality of hermetic terminals functioning as an external interface with the motor provided in a part of the housing;
The protector is an electric compressor protection system in which the protector is electrically connected to a predetermined terminal among a plurality of hermetic terminals. 10. The electric compressor protection system according to claim 9, wherein when the bimetal disk is reversed and the current path is interrupted, the return time of the bimetal disk is delayed by the heat of the positive temperature coefficient thermistor.

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