JP2001115962A - Thermally-actuated switch - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermally-actuated switch used in a closed-type motor- driven compressor, easy to attach thereto, and high in reliability. SOLUTION: This thermally-actuated switch 21 is made up of a switch body 2 and an electrically insulating holder 23 for housing it. The switch body 2 is held apart from an inner wall of the holder 23 by protrusive ridge parts 23D 23E, and the holder 23 is provided with a plurality of opening parts 23A, thereby exposing the switch body 2 sufficiently to a flowing coolant gas. Fixed parts 23B extending from both ends of the holder 23 are fixed to a coil end 6A of a motor by binding them with strings 6B. The switch body 2 is insulated electrically and thermally from the coil end 5A by the holder 23, and cooled by the coolant gas under normal conditions. If coils of the motor are overheated the temperature of the coolant gas rises to lose its cooling effect, and the heat produced within the switch actuates the switch rapidly.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermally responsive switch mounted on a hermetic electric compressor.

[0002]

2. Description of the Related Art There are several methods of attaching a thermally responsive switch to a hermetic electric compressor. In particular, in order to quickly detect a sudden rise in the temperature of a motor winding which occurs when rotation of the motor is restricted. It is effective to mount the heat responsive switch on the coil end of the motor.

[0003] A conventional mounting structure of the thermally responsive switch will be described with reference to FIG. The hermetic electric compressor 101 shown in FIG.
A hermetically sealed housing is composed of the lid 2 and the lid 103 that covers the opening. The motor 10 is housed in the sealed housing.
4 and a compressor (not shown) are arranged.
A heat-responsive switch 106 entirely covered with an electrically insulating heat-shrinkable tube 105 is fixed on the coil end 104A by a strap 107. The heat-shrinkable tube 105 has a heat-responsive switch 106 before its inner diameter shrinks.
It has a slightly larger cylindrical shape,
And contracted so as to have a predetermined positional relationship, thereby being fixed to the thermally responsive switch. Further, each of the lead wires 106A from the thermally responsive switch 106 is connected in series with the motor coil. Further, the other end 104B of the motor coil is connected to a terminal pin 108A of a connection terminal 108 attached to the sealed housing.

According to this mounting structure, the heat responsive switch is integrated on the coil end of the electric motor, so that the entire handling becomes easy. In addition, it is possible to quickly react to an increase in the winding temperature of the electric motor.

[0005]

According to such a mounting structure, the heat-shrinkable tube 105 is connected to the heat-responsive switch 1 in advance.
06 makes it easier to handle the thermo-responsive switch itself, but since the heat-shrinkable tube hardens considerably after shrinking, it is necessary to apply a strong force to securely fix it with the strap. The workability was reduced.

On the other hand, the thermally responsive switch is placed in an electrically insulating holder and separated from the coil end, for example, in Japanese Utility Model Laid-Open No. 60-95183 and Japanese Utility Model Laid-Open No. 63-18338.
No. 4,609,619 attached to the inside of a closed housing of a hermetic electric compressor disclosed in Japanese Patent No.
There is one such as that shown in No. 35, which is attached to a stator core of an electric motor. However, in these cases, it is necessary to perform processing for attaching the holder to the sealed housing or the stator core, or to fix the attachment member. Further, in the case where the wiring is attached to the inside of the sealed housing, particularly to a portion serving as a lid of the housing as in the above-described conventional example, there is a problem that routing of the wiring inside the sealed housing becomes complicated.

[0007] The thermoresponsive switch is usually connected in series with the motor winding to open the contact due to an increase in ambient temperature, and to generate a contact due to internal heat even when an overcurrent exceeding a specified level flows through the motor. It is structured to open.

[0008] Since the coil end always generates heat even under normal operating current, in a conventional structure directly fixed to the coil end, the thermally responsive switch is always heated by the heat generated from the coil end. It has become. In particular, in recent years, the motor windings have tended to be thinner in order to reduce the size and cost of the motor, and as a result, the rate of temperature rise of the coil with respect to current has increased.

On the other hand, various measures have been taken for the thermally responsive switch in order to cope with a rapid rise in the temperature of the motor or a rise in the temperature of the refrigerant when the motor is abnormal. For example, a switch having good thermal conductivity, such as helium, is used as a heat generating member in the switch or a gas to be sealed in the switch to improve the response of the switch to heat from the coil. Further, since the coil temperature during normal operation is high for the above-described reason, the operation set temperature of the thermally responsive element such as a bimetal is set high. However, the upper limit of the operation set temperature is defined by the electric insulating material used. Therefore, FIG.
As shown in Fig. 0, the thermoresponsive switch is always kept at a relatively high temperature by the heat from the coil end, and the operating temperature cannot be raised above the specified value, so the difference between the temperature during normal operation and the operating temperature. Harmful operation that excessively reacts in spite of a condition that should be allowed in actual operation, such as the contacts of the thermal switch being opened due to a temporary increase in current due to short-time high-load operation, etc. May occur.

[0010]

SUMMARY OF THE INVENTION Accordingly, a thermoresponsive switch according to the present invention comprises a switch body and an electrically insulating holder for housing and holding the switch body. In addition to ensuring electrical insulation with respect to the mounting portion, the portion of the holder that does not affect the electrical insulation is directly in contact with the refrigerant so that heat exchange between the switch body and the refrigerant is good, and the switch body is A gap is provided between the housing and the holder, which allows the refrigerant to flow therethrough.Furthermore, a fixed portion is provided extending from both ends of the holder, and the fixed portion is attached to the electric compressor when mounted on the electric compressor. , The entirety of the thermoresponsive switch is fixed.

Another feature is that at least a fixed portion of the holder of the thermally responsive switch is shaped along an arc of the coil end for mounting on the coil end of the electric motor of the electric compressor. The cylindrical portion has a surface close to the coil end and a surface close to the metal hermetic housing of the electric compressor, which serves as a shielding surface for ensuring electrical insulation. The portion that does not affect the insulation is that a sufficient opening is provided so that the heat exchange between the switch body and the refrigerant is good.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. FIG. 1 shows an example in which the thermoresponsive switch of the present invention is mounted in a hermetic electric compressor. FIGS. 2 and 3 are perspective views and a top view of the vicinity of a mounting portion of the thermoresponsive switch.
FIG. 4 is a side view of the thermoresponsive switch. FIG.
Other than that, the lead wires connected to the thermoresponsive switch are omitted for easy understanding.

The thermally responsive switch 1 comprises a switch body 2 and a holder 3, and is installed in a housing of a hermetic electric compressor. The hermetic electric compressor 4 forms a hermetic housing with a substantially cylindrical housing 5A and a lid 5B, and has an electric motor 6 and a compressor (not shown) provided below the electric motor 6. Refrigerant gas is filled in the closed housing, and the refrigerant gas is compressed by a compressor driven by the electric motor 6 and moves to the upper part of the housing through a gap between a stator and a rotor of the electric motor 6 to cover the housing. It is sent from a discharge pipe 5C provided in the body 5B to a heat exchanger (not shown) and returned to the compressor in the closed housing again.

The switch body 2 is provided with a contact mechanism using a heat responsive body such as a bimetal in a metal hermetic container, and opens and closes contacts by external heat or internal heat generated by an electric current. . This switch body 2
Is connected in series with the coil of the electric motor 6, and in the case of the present embodiment, the coil of the electric motor is a three-phase star connection, and the switch body 2 is connected to one end of each phase coil which is the midpoint of the three-phase star connection. The other end of each phase of the motor coil is connected to a hermetic terminal 8 provided on a lid 5B via a lead wire 7, and further connected to an external power supply.

The thermally responsive switch 1 has a switch body 2 fixed to an electrically insulating holder 3 to maintain insulation from the coil end 6. The holder 3 of this embodiment has a holding portion 3A.
And 3B, respectively, and hold the switch body 2 in the holder 3 while holding it from all sides. In this embodiment, the end surface 2A, which is slightly wider in the shape of a flange of the switch body 2, is held so as to be gripped by the holding portion 3A, and the movement of the entire switch container is suppressed by the holding portion 3B. At this time, a gap 3D is formed between the switch body 2 and the holder 3 so that the refrigerant can pass therethrough for a reason described later.

The thermally responsive switch 1 is fixed on a coil end 6A of the electric motor 6 with a tie string 6B. This tying string 6
Although the entire thermally responsive switch 1 may be tied up by B, the switch body 2 part protrudes largely with respect to the coil width in the embodiment, for example, so that it is difficult to automate the fixing operation with the tying string as it is. Therefore, in the present invention, an extended fixing portion 3C is provided at both ends of the holder 3, and this portion is tied to the coil end 6A, so that the entire thermally responsive switch 1 is fixed. Actually, as shown in FIG. 1, a part of the lead wire 9 for connecting the heat responsive switch 1 and the coil of the electric motor 6 is fixed together by the binding string 6B, but the lead wire 9 has sufficient flexibility and has a fixed portion. Since it is in close contact with the 3C, there is no hindrance to this fixing work.

According to the thermal responsive switch 1, there is no need to provide a special structure for mounting the thermal responsive switch in the motor or the sealed housing, and the fixing operation itself with the conventional tying string can be made easier. it can. Further, the holder 3 is thicker than the conventional insulating tube so that heat conduction from the motor coil end 6A to the switch main body 2 is difficult, and the switch main body 2 has a gap 3D not only in the part not facing the holder but also in the part facing it. Is provided, most of the switch body 2 is exposed to the flow of the refrigerant gas and heat is taken away. Therefore, the temperature of the switch body during normal operation is lower than that of the conventional switch body, which is acceptable for the electric motor. The harmful operation which excessively reacts due to the increase of the current in a short time should not occur. In addition, when an overcurrent flows through the coil due to the restriction of the rotation of the motor and the coil end to which the thermally responsive switch is attached generates heat, the heat generated by the coil end heats the refrigerant gas and deprives the switch of heat. At the same time, the amount of heat generated inside the switch body increases due to the overcurrent, so that the thermally responsive member such as a bimetal reaches the operating temperature. In this way, the thermal responsive switch quickly opens the contact mechanism to stop energizing the motor, thereby preventing burnout of the motor windings and accidents caused by the burnout.

Further, during normal operation, the electric motor is practically cooled by exchanging heat with the refrigerant gas flowing through the closed housing. However, if this refrigerant gas leaks out for some reason, the electric motor will be insufficiently cooled and the electric motor will be insufficiently cooled. May reach the burnout temperature. Even in such a case, according to the present invention, when the heat exchange by the refrigerant gas becomes insufficient, the contact mechanism is opened by the heat generated inside the switch body, thereby preventing the electric motor from burning.

Next, another embodiment of the present invention will be described. FIG. 5 is a cross-sectional view of a main part of the hermetic electric compressor 24 to which the thermally responsive switch 21 is attached. FIGS. 6 and 7 are a perspective view and a top view of the vicinity of the attached portion of the thermally responsive switch. FIG. 8 is a view of the thermally responsive switch as viewed from the direction in which the switch body is inserted into the holder. FIG.
It is an A sectional arrow view. The same parts as those in the above-described embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted. Further, for the same reason as in the above-described example, the description of the lead wires connected to the thermally responsive switch is omitted except in FIG.

The heat responsive switch 21 is fixed on the coil end 6A of the electric motor 6 by a strap 6B. The thermally responsive switch 21 has a structure in which the same switch body 2 as described above is housed in an electrically insulating holder 23. Although the holder 23 covers the switch body 2 as a whole, a plurality of openings 23A are perforated so that the container of the switch body is sufficiently exposed to the flow of the refrigerant gas, and sufficient air permeability is secured. Have been. At both ends of the holder 23, there are provided fixing portions 23B extending in the shape of the arc of the coil end 6A. By fixing the fixing portion 23B to the coil end 6A with the tying string 6B, a heat responsive switch is provided. The whole 21 is fixed on the coil end 6A.

Both ends of the holder 23 are open, and the switch body 2 is inserted through one of the insertion openings 23C. A ridge for holding the switch body is provided on the inner surface of the holder 23. In the embodiment, two ridges 23D are provided on the upper side in the figure and one ridge 23E is provided on the lower side in accordance with the curved shape of the switch body 2, and the opening 23C of each ridge is provided. A concave step is provided on the side, which serves as a detent for the switch body and accommodates the end face 2A which is slightly wider in the switch body of the embodiment. The amount of insertion of the switch body 2 into the holder 23 is defined by the end face 2A of the switch body abutting on the step.

The thermally responsive switch 21 is suitable for a case where higher insulation performance is required as compared with the above-described thermally responsive switch 1. In other words, in the thermally responsive switch 23, the opening 23 is not provided on the surface 23F facing the coil end 6A and the surface 23G facing the sealed housing of the electric compressor, and between the metal container of the switch body 2 and each metal portion. The electrical insulation performance is improved by extending the electrical distance as a shielding surface. The other surface of the holder 3 has an opening 23A.
At the same time, the both ends of the holder are penetrated, and the switch body 2 is held in the holder by the holding projections 23D and 23D.
Gap 23H so that it floats from the inner wall of the holder with 3E
Is provided, a flow of the refrigerant gas is also generated in both ends of the holder, and heat exchange between the container of the switch body 2 and the refrigerant gas can be performed more efficiently.

Therefore, the temperature of the switch body during normal operation becomes lower than that of the conventional switch body by being cooled by the refrigerant gas. The harmful operation that the response switch reacts excessively does not occur.

[0024]

As described above, according to the structure of the thermally responsive switch of the present invention, it is possible to fix it on the coil end by using the tying string, as in the case of the thermally responsive switch using the conventional insulating tube. Therefore, there is no need to install special hooks or other structures inside the motor or hermetic housing for mounting the heat-responsive switch, and the fixing work that is extended along the coil end is provided by the tying strap. In itself, it can be made easier as compared to the conventional one.

In addition to the structure in which the switch is mounted on the coil end, the heat of the coil is less likely to be directly transmitted to the switch main body than the conventional one by the holder, and most of the switch main body container has the refrigerant in the sealed housing. Since the switch body is exposed to the gas flow, the temperature of the switch body during normal operation is efficiently cooled by the refrigerant gas and becomes lower than that of the conventional switch body. In this way, the difference between the temperature of the thermally responsive switch during normal operation and the operating temperature can be increased, and no harmful operation will occur if the current is increased for a short time which should be allowed for the motor.

[Brief description of the drawings]

FIG. 1 is a partial cross-sectional view of a hermetic electric compressor to which an embodiment of a thermoresponsive switch according to the present invention is attached.

FIG. 2 is a view showing a state in which the thermally responsive switch of FIG. 1 is mounted on a coil end;

FIG. 3 is a diagram showing a state in which the thermally responsive switch of FIG. 1 is mounted on a coil end;

FIG. 4 is a side view of the thermally responsive switch of FIG. 1;

FIG. 5 is a partial sectional view of a hermetic electric compressor to which another embodiment according to the thermally responsive switch of the present invention is attached.

FIG. 6 is a diagram showing a mounting state of the thermally responsive switch of FIG. 5 on a coil end;

FIG. 7 is a view showing a state in which the thermally responsive switch of FIG. 5 is mounted on a coil end;

FIG. 8 is an end view of the thermally responsive switch of FIG. 1;

FIG. 9 is a side view of the thermal switch of FIG. 1;

FIG. 10 is a partial cross-sectional view of a conventional hermetic electric compressor equipped with a thermally responsive switch.

[Explanation of symbols]

 1, 21: thermal response switch 2: switch body 3: holder 3A, 3B: holding part 3C: fixed part 3D: gap 4, 24: hermetic electric compressor 5A: housing 5B: lid 6: electric motor 6A: coil end 7: Lead wire 8: Airtight terminal 23: Holder 23A: Opening 23B: Fixed part

Claims (2)

[Claims] 1. A thermoresponsive switch mounted in a housing of a hermetic electric compressor in which a refrigerant circulates in a hermetically sealed housing, wherein the thermoresponsive switch comprises a switch body and an electrically insulating holder for housing and holding the switch body. The switch body houses a switch contact mechanism in a bottomed cylindrical metal container, and a metal lid plate is welded to an opening of the container to form an airtight container. In addition to securing the electrical insulation for the mounting portion of the hermetic electric compressor, the portion that does not affect the electrical insulation of the holder is directly cooled by the refrigerant so that heat exchange between the switch body and the refrigerant is good. There is a gap between the switch body and the holder that is sufficient for refrigerant to flow, and a fixed portion is provided extending from both ends of the holder. A thermally responsive switch characterized in that the fixing portion is fixed to the mounting portion of the electric compressor when the fixing portion is fixed to the mounting portion of the electric compressor, whereby the entirety including the switch body is fixed. At least a fixed portion of the holder is shaped along an arc of the coil end for mounting on a coil end of the electric motor of the electric compressor, and the holder has a cylindrical portion for receiving the switch body; The cylindrical portion has a surface close to the coil end and a surface close to the metal hermetic housing of the electric compressor, which serves as a shielding surface for securing electrical insulation, and a portion not affecting the electrical insulation. 2. The thermally responsive switch according to claim 1, wherein a sufficient opening is provided so that heat exchange between the switch body and the refrigerant is good.