JPH0334169B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention utilizes the rapid jumping motion by drawing a thermally responsive plate such as a bimetal that changes its shape depending on temperature differences into a plate shape so that it can perform sudden jumping motions at different temperatures. In particular, the other end of a connecting member fixed near the fixed end of the thermally responsive plate that makes a sudden jump motion is fixed to a thermally responsive plate support, and the connecting member and By arranging the distance setting member between the thermally responsive plate support and the thermally and electrically insulated state, it is easy to accurately set the temperature at which the movable contact separates from the fixed contact to a desired value as described below. This paper proposes a thermally responsive switch that has the effect of improving protection performance by shortening the operating time when a current several times the limit operating current value is passed.

Embodiments of the present invention will be described below with reference to the drawings. In Figure 1, 1 has an opening 1a at the left end.
2 is a container made by drawing an iron plate or the like, and 2 is a lid plate made by punching out an iron plate into a disc shape. Opening 1 of container 1
A is bonded and fixed to the vicinity of the outer periphery of the lid plate 2 by a method such as ring welding, and a single sealed container is constituted by both of them. A hole 2a is bored in the cover plate 2 at a position offset from the center, and a conductor 4 is hermetically fixed to the hole 2a while being electrically insulated by a filler material 3 such as glass. The left side of the conductor 4 in the figure, that is, the part that protrudes outside the sealed container, is connected to the equipment or power source protected by this thermally responsive switch, and in this embodiment, the connecting fitting 9b for this purpose is made by welding or the like. It is fixed by a method.
On the right side of the conductor 4 in the figure, that is, on the inside of the sealed container, there is a fixed contact support 5 having a disk-shaped fixed contact 5a clad with, for example, a silver alloy and having a partially spherical upper surface fixed to its tip. It is fixed.
The fixed contact support 5 is made by bending an appropriate metal plate into an L-shape selected so that its specific resistance, weldability, etc. meet the purpose. A thermally responsive plate support 8 made of an L-shaped metal plate is fixed to a portion of the lid plate 2 facing the inside of the sealed container by a method such as welding.
The right end of a connecting member 7 made of a suitable metal plate bent into a crank shape is fixed to the right side of the thermally responsive plate support 8, and the left end of the connecting member 7 is a bimetal or trimetal member with a movable contact 6a fixed near the tip. A thermally responsive plate 6 consisting of is fixedly attached. At this time, the connecting member 7 has a shape that is easier to deform near the center than both ends thereof, and has a structure that has the effect of avoiding deformation of the fixed part and the thermally responsive plate support during calibration of the operating temperature, which will be described later. ing. The center part of the thermally responsive plate 6 is drawn into a shallow dish shape, and at a predetermined temperature, for example, 120°C, it suddenly flips over to the state shown by the dotted line, and the movable contact 6a is opened from the fixed contact 5a by a snap action. Also, for example, at 80° C., the contact jumps back and the contacts are closed to the state shown by the solid line in the figure. A spacing member 8a, such as a screw, screwed into the vicinity of the tip of the thermally responsive plate support 8, connects a portion of the connecting member 7 near the base to which the thermally responsive plate 6 is attached at its lower end, and is made of, for example, an insulator. By pressing through the insulating member 8b, the central, slightly narrow portion 7a of the connecting member 7 is deformed, and the contact pressure that acts between the movable contact 6a and the fixed contact 5a at room temperature, for example, is adjusted to an appropriate value. The above-mentioned snap operation is ensured and the operating temperature is calibrated, and after the calibration, it is fixed at that position. Spacing member 8 like a screw
If a is made of an electrical insulator, the insulating member 8b is unnecessary. A connecting fitting 9a for connecting to an external circuit on the same potential side as the closed container is fixed to the outside of the lid plate 2 by welding or the like. If a thermally responsive switch with such a configuration is connected in series with a motor to be protected via the connecting fittings 9a and 9b, connected to a power source, and installed in a heat exchange relationship with the motor windings, the motor The influence of the temperature of the windings and the motor current flow through the thermally responsive plate support 8 - the connecting member 7 - the thermally responsive plate 6 - the movable contact 6a - the fixed contact 5a - the fixed contact support 5 - the conductor 4. Under the influence of heat generated by the resistance, the temperature of the thermally responsive plate 6 rises, and in the event of an abnormality, the thermally responsive plate 6 suddenly jumps and reverses, entering the state shown by the dotted line, cutting off the current supply to the motor and reducing the motor winding temperature. Abnormal rise can be protected. In FIG. 1, the thermally responsive plate support 8 is fixed to the cover plate 2, and the fixed contact support 5 is fixed to the conductor 4, but in contrast to this, the thermally responsive plate support 8 is fixed to the cover plate 2.
is fixed to the conductor 4, and the fixed contact support 5 is fixed to the cover plate 2.
Of course, the same effect can be obtained even if it is fixed to the surface.

In a thermally responsive switch with the structure described above, the critical operating current value (hereinafter referred to as UTC) and its characteristics are necessary to protect the motor etc.
When a current several times the value of UTC is passed through the switch, there is an operating time (hereinafter referred to as ST) until the thermally responsive plate reaches a predetermined jump reversal temperature and opens the contact. As is well known, UTC must match the rated load operating current of the motor. If the UTC is below this rated current, the motor will not operate sufficiently and the operating rate will be reduced due to the overly protective thermal switch. Conversely, UTC
If the current is higher than 150% of the rated current, there is a risk that the windings will overheat and the insulation will deteriorate when the motor is operated under overload. Therefore, the UTC is selected, for example, in a range of about 105% to 125% of the rated load operating current. Next, when the motor's torque is overcome by the load's torque and the rotor does not turn, a so-called rotor locked state occurs, and a current several times the rated current flows through the motor windings. In this case, the current must be supplied immediately. must be shut off to prevent overheating of the windings. In such cases, the ST characteristics of the thermally responsive switch become a problem.

In order to adjust the UTC of the thermally responsive switch to a preferable range for the rated current of the motor to be protected, it is necessary to select a low resistance value for each component of the thermally responsive switch, but the mechanical strength of each component must also be considered. and design the resistivity and dimensions of the materials to be used. The design is relatively easy if only the UTC is matched to the motor's rated current, but recently motor windings have been designed with no thermal margin against overcurrent (when the rotor is locked). Therefore, the ST of the thermally responsive switch is required to be short. That is,
It is desirable to shorten ST without changing UTC. In order to meet this demand, various questions have been raised regarding the ratio of the resistance value of each component of the thermally responsive switch to the total resistance value (resistance between the connecting fittings 9a and 9b shown in Figure 1). Upon investigation, we found that the part that should have a high ratio to the total resistance value is the thermally responsive plate 6, and the second part is the unique part of the connecting member 7 in order to prevent the self-generated heat of the thermally responsive plate 6 from escaping through conduction. It was found that it was necessary to select a relatively high resistance. Since the size of the connecting member 7 is smaller than the size of the thermally responsive plate 6 and the thermally responsive plate support 8, the low resistance value of this part is not large when directly compared, but the length of the current path is This means that a high resistance value must be selected. If the resistance value per length is set high, the heat generated in this part will be transferred from the thermally responsive plate 6 connected to both ends of this part to the thermally responsive plate support 8.
It acts extremely effectively to block the transfer of heat to. Therefore, in thermally responsive switches designed for the same UTC, the ST differs considerably depending on whether the connecting member 7 has a large resistance value per length or a small resistance value per length.

The above-mentioned matters will be explained using specific numerical values as follows. The method of measuring UTC is to place a thermally responsive switch in an electrically insulating fluid whose ambient temperature is constant at 60°C, and after allowing the temperature to sufficiently adjust to the surrounding temperature, start applying current between the connecting fittings 9a and 9b to predict the UTC. Increase the current at a rate of 1 ampere over 10 minutes from a lower current of several amperes, and read the current value when the contacts open. The method for measuring ST is to allow the switch to fully adjust to the ambient temperature in a thermostatic chamber with a constant ambient temperature of 25°C, then pass a constant current of 60 amperes between the connecting fittings 9a and 9b, and then the contacts open and the current is interrupted. Measure the time it takes. The thermally responsive switch used in the experiment was as shown in Figure 1, and for comparison, the spacing setting member 8 was used.
A is a brass screw and its lower end is an insulating member 8b.
The test was carried out on a part of the connecting member 7 that was in direct contact with the part fixed to the thermally responsive plate without intervening. 1st
In the illustrated embodiment, a small piece of alumina porcelain is used as the insulating member 8b, and the total resistance is 2.5 mΩ, of which the thermally responsive plate 6 is 1.2 mΩ and the connecting member 7 is 0.3 mΩ.
Ω, thermally responsive plate support 8 is 0.3 mΩ, between both contacts is 0.2 mΩ including contact resistance, fixed contact support 5
was 0.3 mΩ, and the conductor was 0.2 mΩ. For comparison, in the case where the insulating member 8b is omitted, the total resistance is 2.5 mΩ, of which the thermally responsive plate 6 is 1.2 mΩ, and the connecting member 7 is bypassed with a brass screw.
0.01 mΩ The material of the thermally responsive plate support 8 was replaced with a material with a high specific resistance value, and the resistance was 0.59 mΩ, the resistance between both contacts was 0.2 mΩ including contact resistance, and the fixed contact support 5 was 0.3 mΩ.
The conductor was 0.2 mΩ. The example model has a UTC of 34.5 amperes and an ST of 12 seconds, while the comparative model has a UTC of 34.5 amperes and an ST of 12 seconds.
UTC was 34.3 amperes and ST was 16 seconds. ST is
Being 30% longer means that a very dangerous temperature rise will occur in protection when the rotor is locked, and the protection performance can be said to be extremely poor.

As described above, in the present invention, the thermally responsive plate 6 that quickly flips and returns is supported on the thermally responsive plate support 8 via the connecting member 7 having a high resistance value per length, and the thermally responsive plate support 8 The distance setting member 8a is thermally and electrically insulated between the vicinity of the tip of the connecting member 7 and the connecting member 7.
By setting the temperature according to I can do things. In addition to the screw-like shape shown in FIG. 1, the spacing setting member may have a shape as shown in FIG. 2. That is, FIG. 2 shows an enlarged view of a portion surrounding the tip of the thermally responsive plate support 8 shown in FIG. A metal arm 11 is shown inserted between the connecting member 7 and for fixing this wedge 10. The left end of the arm 11 is fixed to a part of the thermally responsive plate support 8 by a method such as welding, and the right end is fixed to the wedge 10 at an appropriate position as it pushes the wedge 10.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view of a sealed thermally responsive switch according to an embodiment of the present invention. FIG. 2 is a partially enlarged view corresponding to FIG. 1 according to another embodiment. DESCRIPTION OF SYMBOLS 1... Container, 1a... Opening, 2a... Hole, 2... Lid plate, 4... Conductor, 3... Filler, 5a... Fixed contact,
5... Fixed contact support, 6a... Movable contact, 6... Thermal response plate, 8... Thermal response plate support, 7... Connection member, 8
a, 10... Spacing setting member.

Claims (1)

[Claims] 1 A container having an opening at one end, a lid plate that is bonded and fixed to the opening to form a closed container, a conductor that is fixed to a hole in the lid plate with an electrically insulating filler, and A thermally responsive plate support and a fixed contact support are each fixed to a portion of the inside of the container of the conductor and the lid plate, and near the tip of the thermally responsive plate support there is a device that performs a quick jump reversal and a quick jump return at different temperatures. In a closed type thermally responsive switch, a thermally responsive plate is fixed via a connecting member, and a fixed contact that contacts or separates from a movable contact provided at a movable end of the thermally responsive plate is fixed to the fixed contact support. , the connecting member has a shape that is easier to deform near its center than both ends, and a spacing member is inserted in a thermally and electrically insulated state between near its tip and near the tip of the thermally responsive plate support. The temperature at which the movable contact separates from the fixed contact can be adjusted by increasing or decreasing the contact pressure between the fixed contact and the movable contact by adjusting the distance between the connecting member and the vicinity of the tip of the thermally responsive plate support. A sealed thermally responsive switch that is calibrated.