JPH0768942B2 - Protective device for hermetic electric compressor - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention relates to a hermetic electric compressor in which a heat carrier gas such as freon is circulated, in which a lubricating oil of the electric motor and the compressor is in a hermetically sealed container in a normal operating state. Before the normal circulation of the lubricating oil is obstructed and the motor or compressor fails due to the absence of a specified amount of the oil that should normally be present, the power supply to the electric motor is shut off and the lubricant is normally present. The present invention relates to a protective device that limits power supply to an electric motor until a fixed amount is secured.

[Background technology]

Conventionally, as such a protection device, there is a switch that accommodates a thermo-responsive body that is deformed by heat such as bimetal in a sealed casing, and that drives a pair of contacts by the thermo-responsive body.
This switch is fixed to the coil end part of the stator winding of the electric motor of the hermetically-sealed electric compressor so that the current flowing through the motor exceeds a specified value or the temperature of the coil end part near this switch exceeds a specified value. There is known a protector that shuts off the operation by shutting off the current flowing to the electric motor when the switch is activated.However, the present invention is concerned with the abnormal movement of the lubricating oil which is considered to be the cause before causing the abnormal temperature rise. Is detected, the operation of the electric motor is interrupted, and the electric compressor is protected by not continuing the operation until a predetermined amount of lubricating oil is returned to the normal location. It relates to the device.

[Outline of Invention]

The present invention has a control mechanism in which a heat generating element and a heat responsive element are mounted on a heat transfer member that is a conductor of good heat, and a predetermined amount of lubricating oil is retained during normal operation in a closed container of a hermetic electric compressor. The heat response element of the control mechanism, which is placed in the area where the heat is generated and is immersed in the lubricating oil during normal operation, transfers most of the heat generated by the heat generating element to the lubricating oil and diffuses it to the specified operating value. Is maintained in a low temperature range less than the above, and during abnormal operation, when the lubricating oil is moved to a place other than the part where the heat transfer member of the control mechanism is attached, a heat generating element of the control mechanism is generated. A large amount of heat is accumulated on the heat transfer member, thereby increasing the temperature of the heat responsive element to a predetermined operating value or higher, thereby stopping and protecting the operation of the hermetic electric compressor.

Example of Invention

In FIG. 1, a hermetically-sealed electric compressor 10 comprises a robust iron container 11 and a lid 12 in which a motor 14 and a compressor 13 are housed in a hermetically sealed container in which a sealing portion 11A is hermetically welded. is there. The compressor 13 is press-fitted and fixed in the closed container 11, and the stator 14A of the electric motor 14 is fixed to a stationary portion of the compressor by a fixing member 13A. The motor rotor 14B is connected by its shaft 14C to drive the moving parts of the compressor. Axis of rotation
14C extends downward, and at the normal lubricating oil level, the tip is immersed and a hole 14D is formed in the center, and the suction of lubricating oil due to gas pressure difference in the closed container etc.
And is supplied to the sliding portion and the bearing portion of the compressor 13. The control mechanism 15 is fixed to the stator winding 14E of the electric motor. A suction pipe 16 is connected to the suction side of the compressor 13, and its discharge port 13B is located at the upper part of the compressor, and when driven by an electric motor, heat transfer gas such as freon is discharged from the discharge port 13B.
From the closed container 11 and the compressor 13 to the passage 13C
To the discharge pipe 17 from around the electric motor 14,
The gas discharged from the discharge pipe circulates through a device such as a well-known condenser or evaporator (not shown) to finish the thermal work and return from the suction pipe 16 to the compressor 13 again. The motor stator winding is connected to an airtight terminal having a plurality of conductors that are electrically insulated from the wall of the hermetically sealed container 11 in order to be connected to an external power source (not shown). There is. The lubricating oil has a normal amount level near the lower end surface of the motor winding 14E as indicated by symbol 18, and the control mechanism 15 is mounted so that most of it is located below the free surface level of the lubricating oil 18.

The control mechanism 15 is shown in FIG. 2, and two through-holes are formed in a board 21 made by punching a relatively thick iron plate into a circle. Conductive pins 23 and 24 are hermetically sealed by penetrating the substrate 21 with an insulating filler 22. In the vicinity of the tip on the left side of the conductive pin 23 in the figure, a thermo-responsive body 25 made of a metal that is deformed by a change in temperature such as bimetal is supported, and a movable contact 26 is fixed to the tip of the thermo-responsive body 25. There is. A fixed contact 27 forming a pair with the movable contact is fixed to the left end of the conductive pin 24 in the drawing,
A heater 28 made of a material having a high specific resistance value such as a nichrome wire has one end fixed to the conductive pin 23 by a method such as welding and the other end fixed to the substrate 21. A casing 29 that surrounds these and is formed by deep-drawing an iron plate is welded to the substrate 21 at the entire circumference of the opening at the right end thereof to form a sealed casing. A terminal fitting 30 is welded to the outside of the board 21. Here, the heater 28 is attached to a heat generating element, and the heat responsive body 25 is attached to a hermetically sealed casing corresponding to a heat responsive element and a heat transfer member.

Next, the operation will be described with reference to FIG. Taking a single-phase induction motor as an example of the electric motor, one end of the power source E has a lead wire.
31 is connected to the conductive pin 24 of the control mechanism 15 by the lead wire 32A via the conductor 32 of the airtight terminal T. The other end of the power source E is connected to one end of the main winding M of the electric motor by the lead wire 33 via the conductor 34 of the airtight terminal T, and the lead wire 33 is connected to the conductor 35 of the airtight terminal T through the capacitor C. It is connected to one end of the auxiliary winding A. The other end of the main winding is the control mechanism 15
Connected to the conductive pin 23 of the
It is connected to the terminal fitting 30 of. Since the control mechanism 15 is as shown in FIG. 2, when the power switch S is closed, the current from one end of the power source E is lead wire 31-conductor 32-lead wire 32.
A-Conductive pin 24-Fixed contact 27-Movable contact 26-Thermal responder 25
-Conducting pin 23-Main winding M-Conductor 34-Lead wire 33 to the other end of the power supply E. In addition, the same circuit is used from the lead wire 31 to the conductive pin 23 from here to the heater 28-terminal fitting 30-
It also flows to the other end of the power supply E at the same time through the auxiliary winding A-conductor 35-capacitor C-lead wire 33. Therefore, the electric motor 14 rotates, which causes the compressor 13 to operate. As can be seen from FIG. 1, the lubricating oil 18 is the hole 14D of the rotary shaft as described above.
The lubricating oil sucked up from the oil and supplied to the sliding parts of the bearing and the compressor 13 is normally sucked up and circulates downward through a passage 13C provided between the closed container 11 and the compressor 13. Therefore, the lubricating oil level is maintained at the position shown. However, due to some abnormality such as fluctuation of gas pressure in the closed container, a large amount of lubricating oil was sucked up and accumulated too much in the upper part of the compressor 13, and the level of the lubricating oil in the lower part of the closed container 11 drastically dropped. If it is separated from the end surface of the suction hole 14D of 14C, the supply to the sliding portion of the compressor 13, the bearing, etc. is reduced and eventually a fatal failure occurs. Therefore, the control mechanism 15 is arranged to operate when the level of the lubricating oil 18 is lowered and most of the control mechanism 15 is exposed to the heat transfer gas before a failure occurs.

As described above, the total current of the electric motor is flowing through the heat responder 25 in the control mechanism, but since the resistance value of the heat responder 25 is selected to be low, the temperature of the heat responder does not rise so much. Although the current flowing through the auxiliary winding A of the motor is smaller than the total current and the main winding current, it passes through the heater 28 in the control function. Therefore, if the resistance value of the heater 28 is properly selected, the heat generated by the heater 28 will cause heat to be enclosed. 29
The temperature of the heat responsive body 25 can be raised while heating the. The heat-actuating body 25 is formed in a shallow dish-like shape in the approximate center, and is normally curved downward as shown in FIG. 2, and the movable contact is pressed against the fixed contact to close the electric path between them. Then, the curved direction of the dish-shaped portion is suddenly reversed, and the movable contact 26 operates so as to separate from the fixed contact 27. The main winding current is an excessive value when starting the motor,
Since this is a fraction of the operating current in a very short time, the temperature of the thermal actuator 25 does not reach 150 ° C due to the excessive current at the time of startup. It's easy to do with switches, as is well known. Since the auxiliary winding current of the electric motor is almost constant irrespective of changes in the number of revolutions that occur during normal operation, when the heater 28 is heated by this current, the casing 29 and the thermal actuator 25 are generated.
The temperature of can be made almost constant. Therefore, when the outside of the casing 29 is almost entirely in contact with the lubricating oil, the heater 28
Although the heat generated by is diffused into the lubricating oil and rises only to a certain degree,
When the housing 29 is exposed from the lubricating oil, the diffusion of the ambient gas surrounding the housing 29 from the surface of the housing 29, which rises due to the heat generated by the heater 28, is reduced, and the temperature rises significantly.
According to an experiment using Freon gas and a so-called Sniso as a lubricating oil, the difference in temperature rise between the case where the housing 29 is immersed in Sniso and the case where it is exposed to Freon gas is 50 ° C.
Obtained ~ 60 ° C. In the actual hermetic electric compressor, for example, the temperature difference is such that the temperature of the thermal actuator 25 is kept below 130 ° C in a normal state where the casing 29 is sufficiently immersed in lubricating oil and the contacts are closed. And abnormal operation results in case 29
Was exposed to the atmospheric gas due to the drop in the level of the lubricating oil, it was sufficient to bring the temperature of the thermal actuator 25 to 150 ° C. or higher to open the contact points.

Although various embodiments have been described above, other embodiments of the present invention have various modifications, for example, functions of both the heat generating element and the heat responsive element of the control mechanism are made of a material such as bimetal whose specific resistance value is selected. There are various possibilities such as using self-heating of the heat-responsive body itself, and various combinations can be easily made by those skilled in the art as necessary.

〔The invention's effect〕

According to the present invention, it is possible to prevent the conventional hermetic electric compressor from being damaged due to lack of lubricating oil by the function of the inexpensive control mechanism, and the excessive current flows in the motor winding longer than the normal starting time. Even in the case of the above, there is an excellent effect that the electric power supply to the electric motor is stopped and the durability of the electric compressor can be improved.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing a protective device for a hermetic electric compressor according to the present invention. FIG. 2 is a partially cutaway perspective view showing an embodiment of the control mechanism of the apparatus shown in FIG. FIG. 3 is an electric circuit diagram for explaining the device of the present invention. 11 ・ 12 …… Closed container, 13 …… Compressor, 14 …… Electric motor, 15 …… Control mechanism, 18 …… Lubricating oil, 25 …… Thermal response element, 26 …… Moving contact, 27 …… Fixed contact, 28: heating element, 29: housing, M: main winding, A: auxiliary winding.

 ─────────────────────────────────────────────────── ─── Continuation of the front page Examiner Yuji Sugazawa (56) References JP-A-52-22948 (JP, A) Actual exploitation Sho-57-127532 (JP, U) Actual exploitation Sho-56-122795 (JP, U) Actual Public Sho 47-42624 (JP, Y1) Actual Public Sho 43-11736 (JP, Y1)

Claims (1)

[Claims] 1. An electric motor and a compressor are housed in a closed container,
The compressor is driven by the rotation of the electric motor to circulate the heat transfer gas, and a heat transfer member is arranged in the closed container at a portion where a predetermined amount of lubricating oil is secured during normal operation of the compressor. A control mechanism that is brought into contact with the lubricating oil is installed, and the control mechanism is one in which a heat generating element and a heat responsive element are mounted in a hermetically sealed casing configured by the heat transfer member with good heat conduction. The element uses a heat deformable member, and a movable contact is provided in the vicinity of the movable end of the heat deformable member, and a fixed contact is fixed to the movable contact so as to be able to open and close, and the heat generating element and the heat responsive element are windings of the electric motor. Connected in series with the heat generating element, the heat generated by the heat generating element is configured to be transferred to the heat transfer member and the heat responsive element, and normally the control mechanism diffuses the heat into the lubricating oil to reach a value below a predetermined temperature. Held in In an abnormal state in which the compressor moves the lubricating oil to a portion outside the predetermined range, the lubricating oil in the portion in contact with the heat transfer member of the control mechanism decreases and the temperature of the heat response element of the control mechanism rises. The movable contact and the fixed contact are separated by the operation of the motor, and even when a predetermined amount of lubricating oil that contacts the heat transfer member of the control mechanism is secured, when an excessive current is applied to the motor winding for a predetermined time or longer. Protection of a hermetic electric compressor characterized in that the movable contact and the fixed contact are separated when the temperature of the heat responsive element of the control mechanism rises and operates, and the power supply to the electric motor is directly cut off. apparatus.