JPH0316727B2 - - Google Patents

Description

Detailed Description of the Invention [Technical Field of the Invention] The present invention relates to a three-phase electric motor such as a hermetic electric compressor for a refrigerator, in which the heat generated by the three-phase electric motor is easily sensed as close as possible. This relates to a three-phase thermal protector that is installed in an airtight container housing a compressor and that simultaneously opens and closes the midpoint of the stator windings when the temperature exceeds a predetermined temperature due to heat generated by the current flowing through the motor. .

[Background technology]

Conventionally, three-phase thermal protectors were
There is a "three-contact dish-shaped bimetal relay" shown in No.-5747 and an "overcurrent relay" shown in Utility Model Publication No. 41-20189, but both of these are used in the hermetic container of a hermetic compressor. It was incomplete as a sealed thermal protector that could be attached to motor windings, and its shape was inappropriate for maintaining the ability to withstand high pressure in a sealed container filled with Freon gas, etc. . A further improvement in this respect is the ``thermostat switch'' disclosed in Japanese Patent Publication No. 34532/1983. However, this thermostat switch has a structure in which two welded parts are completely sealed to form an airtight container, which requires a large number of steps, and among its components, the member that supports the movable contact has a low strength. In other words, when using a thermostat switch for a small-capacity motor, even if a metal plate with high specific resistance is used, the strength is still insufficient, and the current path must be narrowed, making it difficult to use as a protection switch for a small-current motor. The disadvantage was that it was difficult to adapt as

[Summary of the invention]

The three-phase thermal protector of the present invention eliminates the above-mentioned drawbacks, and has a wide range of applicability from small-capacity motors, that is, low-current motors to large-capacity motors, and can be directly applied to motors of hermetic electric compressors. Because it is a completely sealed type, it can be used in high pressure and high temperature environments such as Freon gas, so it is convenient to calibrate the temperature as a thermal switch with one sealed part.
By arranging a set of contacts, the container is not deformed under the high pressure and high temperature environment in which this three-phase thermal protector is normally used. It is designed to perform calibration.

Therefore, in this three-phase thermal protector, the movable body that supports the movable contacts is made of ceramic and has sufficient rigidity by itself, and a bimetal or the like is drawn into a shallow dish shape through electric motor current. Since the device is equipped with a heating element that heats the reversing plate that performs a sudden jump reversal motion, the heating element itself only needs to be designed to generate a heat amount that matches the current of the motor. It is configured so that it is unrelated to the operation and does not cause any trouble.

[Embodiments of the invention]

FIG. 1 shows all the components in a perspective view. FIG. 2 is a vertical sectional view showing the completed state of the thermal protector at room temperature.

First, the movable body 11 is made of alumina porcelain, for example, and has a rectangular small hole 11a in the center and three round holes 11b on the outside. , 11c and 11d
is worn. Recessed portions for receiving movable contact plates 12, 13 and 14 are formed around the three round holes. The movable contact plates 12, 13, and 14 have movable contacts 15, 16 made of silver alloy, etc.
and 17 are each electrically conductively fixed to a predetermined position on the lower surface by a method such as welding. In addition, the movable contact plates 12, 13 and 14 have 12a and 12a, respectively.
Round holes 13a and 14a are bored, and these holes and the round holes 11b and 11c of the movable body 11
and rivets 18a, 18b and 18c on 11d
are inserted and attached to each other. Here, rivets 18a, 18b and 18c are installed to fix the movable contact plates 12, 13 and 14 to the movable body 11.
The movable contact plates 12, 13, and 14 may be fixed to the movable body 11 using an adhesive without being limited thereto. The three movable contact plates 12, 13 and 14 include 12b and 13, respectively.
Projections b and 14b are formed by pressing, etc., and rivets 18a and 18
The straight line connecting the centers of the three projections as determined by b and 18c is set at a position such that it forms an equilateral triangle. A movable assembly is a heating element 19 made of Nichrome wire or a plate, fixed to the positions of these three projections by a method such as welding, in the vicinity of three vertices.
This is the part indicated by symbol M in the figure. Next, a reversing plate 21 made of a plate-shaped material that deforms depending on temperature, such as bimetal, is placed on the movable body, and the middle stage 22b of the stud 22 made by punching a metal plate is inserted into the round hole 21a of the reversing plate 21. The thinnest part is the lower part 22c.
is the rectangular small hole 11 of the movable body 11 of the movable assembly M.
This lower stage 22c is longer than the thickness of the movable body 11 and its lower end slightly protrudes from the lower surface of the movable body 11. The lower row 2 of the protruding stud 22
Twist the lower part of 2c to secure it so that it cannot be removed. The twisted state of this stud 22 is the screw 22 in Figure 2.
It is shown in the lower part of 22ct. Next, the outer periphery of the reversing plate 21 is attached to the three protrusions 23a and 2 of the support plate 23.
3b and 23c support the plate to the extent that it can be reversed, but the protrusion 23a is initially displaced slightly outward from the state shown in the drawing, and is bent into the shape shown so as to embrace the reversal plate. The upper part 22a of the stud 22 is loosely fitted into the elongated hole 23d in the center of the support so that it can move up and down, but the movable assembly cannot rotate. Although the order is reversed here for convenience of explanation, the support plate 23 is fixed to the first fixed contact plate 31 in advance by, for example, welding. That is, by aligning the long hole 23d of the support plate 23 with the long hole 31a of the first fixed contact plate 31 (it is preferable to make the long hole 31a a little larger), the X mark shown in FIG. The points are fixed by spot welding or the like.

The first fixed contact plate 31 has a slightly narrower width at the center, and has welding projections 31b and 31c on the left end for fixing to the vicinity of the opening of the metal container 41, and the right end is formed into a U-shape below. A fixed contact 51 made of silver alloy or the like is fixed near the end. The second fixed contact plate 32 and the third fixed contact plate 33 are fixed contacts 52 and 53 made of silver alloy, etc., respectively.
The lead-in wires 62 and 63 made of iron-nickel alloy or the like are further fixed by a method such as welding. The lead-in wires 62 and 63 are made of iron, for example, on the cover plate 7.
1 through insulating materials 82 and 83 such as glass. The lid plate 71 is fixed to the open end of the container 41 by a method such as welding to form one airtight container. The terminal plate 91 is fixed to the cover plate 71 by a method such as welding, and if three lead wires (not shown) are connected to the lead-in wires 62 and 63 and the terminal plate 91, they can be electrically insulated from each other. A portion having the same potential as the first, second, and third fixed contacts arranged in this manner can be guided to an electric circuit outside the sealed container.

This thermal protector is
By connecting the three lead wires mentioned above to the midpoint of the three-phase electric motor, the first fixed contact 51, movable contact 15, and second fixed contact are connected at room temperature as shown in FIG. 52 and movable contact 1
6 and the third fixed contact 53, which is not shown in the drawing.
Since the movable contacts 17 and 17 are in the closed state, the windings W ₁ , W ₂ and W ₃ of the three-phase motor generate heat at their midpoints by the heating elements 19 electrically bridging the movable contacts. They will be connected by the body 19.

As is clear from FIG. 2, each movable contact is pressed against the fixed contact with a predetermined pressure at a predetermined temperature by the elasticity of a reversing plate 21 formed of bimetal or the like into a plate shape. As a result, the temperature at which the reversing plate 21 performs reversing operation can be adjusted within a range equal to or higher than the return temperature. The method of applying the pressing force is to bend the center part of the first fixed contact plate 31 by slightly deforming the upper center of the container 41 in the direction of concave, and bending the center part of the first fixed contact plate 31 to bend the protrusions 23a, 23b and 23c of the support plate 23. The outer periphery of the reversing plate 21 is pushed down via the . The force that dents the container is the highest pressure and temperature in a closed container where this protector is normally used, such as 50Kg/ ^cm2・150℃, but the container will not deform, but if the force per unit area exceeds this, for example A load of about 50 kg is applied intensively to a narrow part of ^about 0.3 cm2, causing it to deform.

The temperature of the reversing plate 21 is heated by passing a current through the heating element 19 and rises above the ambient temperature. Therefore, it is necessary to select an appropriate resistance value of the heating element 19 according to the current of the motor to be protected, but in the thermal protector of the present invention, the heating element 19 is electrically conductive to the movable contact plates 12, 13, and 14. Since it has a structure in which the cross-sectional area and length are fixed, there is a large degree of freedom in selecting the cross-sectional area and length, and the applicable current value range can be made very wide. Although the heating element 19 of the embodiment connects the three movable contacts using a delta connection, it is easily possible to use a Y connection.

As for the location where this thermal protector is placed, it is preferable to wrap the outside of the thermal protector with an insulating material and fix it to the windings of the motor to be protected, for example. Therefore, the temperature of the thermal protector is close to the temperature of the motor windings. The temperature of the reversal plate inside the thermal protector rises due to the influence of the winding temperature in the normal operating state of the motor and the heat generated by the current flowing through the heating element 19 disposed very close to the reversal plate. At the increased temperature, the reversal plate maintains the state shown in FIG. 2 and supplies current. When the rotor of the electric motor becomes locked for some reason, an excessive current flows compared to the normal operating current, which causes the heating element 19 to reach a very high temperature, and the temperature of the reversing plate 21 also rises, exceeding the reversing operating temperature. Next to it is the reversing board 2.
1 changes its curvature in a snap-like manner and the movable assembly is pulled upward as shown in Figure 3, and as a result, the three movable contacts are separated from the fixed contacts without pairs and cut off the current. . After the current is cut off, when the temperature of the heating element 19 and the surrounding temperature naturally decrease and the temperature of the reversing plate 21 becomes below the return temperature, the reversing plate 21 returns to its original state as shown in FIG. 2 by a snap operation.

〔Effect of the invention〕

As described above, the three-phase thermal protector of the present invention can insulate the three fixed contacts at a minimum of two locations, and the operating temperature can be adjusted by slight deformation of the sealed container, making it complicated. It has the advantage of having excellent performance, such as being compact and having a wide selection of applicable current ranges, without the need for additional mechanisms or extra sealing parts.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing components according to an embodiment of the present invention. FIGS. 2 and 3 are longitudinal sectional views of the embodiment, with FIG. 2 showing the state at room temperature and FIG. 3 showing the state when reverse operation is performed. 4 and 5 are perspective views showing a partially assembled state, and FIG. 6 is a schematic diagram showing electrical connections. 11... Movable body, 12, 13, 14... Movable contact plate, 15, 16, 17... Movable contact, 19...
Heating element, 21... Reversing plate, 22... Stud, 23...
Support plate, 31...first fixed contact plate, 41...container, 51...first fixed contact, 52...second fixed contact, 53...third fixed contact, 71...lid plate .

Claims (1)

[Claims] 1 An airtight container is constituted by a lid plate joined to the open end of a metal container having an open end and a closed end, and the lid plate has electrically insulated second and third A fixed contact is fixed to the metal container, and a fixed contact plate having a first fixed contact fixed thereto is electrically conductively fixed to the metal container.The fixed contact plate further includes a reversing plate having a plurality of protrusions that moves in reverse according to temperature changes. A support plate supporting the peripheral part of the body is electrically conductively fixed, and three movable contact plates each having a movable contact fixed to it are electrically insulated from each other and fixed to the movable body approximately at the center of the support plate. A movable assembly formed by fixing between three movable contact plates by means of a heating element is supported approximately in the center by a rivet, and each of the movable contacts of the movable assembly and the first, second and third The rivets are positioned so that the fixed contacts close together at room temperature, and by compressing and deforming the container from the outside, the rivets are positioned approximately at the center of the first fixed contact plate. A three-phase thermal protector, characterized in that the reversing operation temperature of the reversing plate is adjusted by deforming the contact point and adjusting the contact pressure of the contact by the reversing plate applied between the three pairs of contacts. .