JPS6362053B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a solenoid with self-recoverable overheat prevention means.

Solenoids that utilize the force exerted by an excitation coil on a movable core are convenient to handle and have long been used, and their ratings are such that the excitation power does not cause the sum of the coil temperature rise and the ambient temperature to exceed a specified temperature (for example, 105°C). It's decided.

Some solenoids have a built-in temperature fuse to prevent the coil from burning out or catching fire if the temperature rises above a safe limit. However, the temperature fuse has the disadvantage that it must be replaced or repaired every time it is activated, making maintenance work extremely troublesome.

The present invention aims to eliminate this drawback and provide a reliable and safe solenoid by incorporating a self-recoverable temperature switch.

The present invention was developed based on the fact that a reed switch does not respond even if a magnetic flux is applied to its contact portion from a direction perpendicular to the axis of the reed. A fixed iron core provided at the open end of the bobbin, a movable iron core inserted into the fixed iron core from the other open end of the bobbin so as to be removable, and a movable iron core provided so as to surround the excitation coil and close the opening on the fixed iron core side of the bobbin. In the solenoid equipped with a fixed iron core and a part of the yoke, the fixed iron core and a part of the yoke are made of a temperature-sensitive magnetic material having the required Kyrie point, and a permanent magnet is assembled in a position facing the fixed iron core of the yoke. A self-recoverable device characterized in that a reed switch is arranged such that its axial direction is perpendicular to the axis of the bobbin, and its contact portion is located on the axis of the bobbin, and the excitation coil and the reed switch are electrically connected. This relates to a solenoid with an overheat prevention function.

Hereinafter, the present invention will be described in detail using examples with reference to the drawings.

FIGS. 1 and 2 are views showing an embodiment of the present invention at temperatures below and above the cutoff temperature, respectively.

In the figure, an excitation coil 1 constituting a solenoid coil is wound around a cylindrical bobbin 2, and is connected to a bottomed cylindrical yoke 3 made of a temperature-sensitive magnetic material having a Curie point Tc corresponding to the cutoff temperature, and an annular lid. body yoke 4
, which closes one opening of the central hole. A cylindrical body 5 made of a non-magnetic material is inserted into the center hole of the bobbin 2, and a fixed iron core 6 made of the same temperature-sensitive magnetic material as the yoke 3 is inserted into the cylindrical body 5.
is provided in contact with the bottom surface 3' of the yoke 3, and the movable iron core 7 is inserted into the cylindrical body 5. The movable iron core 7 is connected to the recovery spring 9 via a connecting member 8 that is connected to a connecting groove 71 provided at the outer end of the cylindrical body 5 . The recovery spring 9 connects the movable core 7 to the fixed core 6.
is biased in the direction away from the Also yoke 3
At a position facing the fixed iron core 6 on the bottom surface 3' of the reed switch 11, magnets 12 and 13 with equal magnetic force are installed near both ends of the glass tube of the reed switch 11 with their magnetic poles perpendicular to the axis of the reed switch 11 and in opposite directions. The reed switch magnet assembly 10 is fitted so that the contact part of the reed switch 11 is on the axis of the bobbin 2 and one magnetic pole surface of each of the magnets 12 and 13 is in contact with the yoke 3. Deploy. A lead end of the reed switch 11 is connected in series with the excitation coil 1.

Next, the operation of the solenoid constructed as described above will be described. Now, when the temperature of the yoke 3 and the fixed iron core 6 is less than the Curie point Tc, the magnetic flux flowing from the magnets 12 and 13 through the bottom 3' of the yoke 3 becomes dominant at the contact part of the reed switch 11, and the contact part is in a closed state. When a power source is connected to the excitation coil 1, it is energized via the reed switch 11, and the magnetic flux generated by the excitation coil 1 attracts the movable core 7 to the fixed core 6, overcoming the biasing force of the spring 9 and causing the magnetic flux as shown in FIG. It sticks to the fixed iron core 7 as shown in the figure.

When the temperature of the yoke 3 and the fixed iron core 6 reaches the Curie point Tc due to the heat generation of the excitation coil 1, they lose their magnetism, so the magnetic flux from the magnets 12 and 13 is in equilibrium at the contact part of the reed switch 11, and the contact is opened. When the coils are separated, the current supply to the excitation coil 1 is cut off.
The magnetic flux from the excitation coil 1 passes perpendicularly through the contact portion of the reed switch 11 and does not include a component flowing parallel to the reed, so it is not involved in the opening and closing of the contact. The reed switch and magnet assembly 10 are a kind of ferromagnetic material detection switch, so if the solenoid has only the movable core 7 without the fixed core 6, even if the yoke 3 exhibits paramagnetism, the movable core is ferromagnetic. 7 is located close to the excitation coil 1, the contact remains closed and the excitation coil 1 cannot be de-energized. In the case of the configuration of the present invention, the movable iron core 7 is isolated by the length of the fixed iron core 6 so that the detection switch does not operate (the contacts are in an open state), so it is possible to cut off the current to the excitation coil 1. can. When the excitation coil 1 is de-energized, the magnetic attractive force acting on the movable core 7 disappears, and the movable core 7 is displaced to the left by the biasing force of the spring 9, as shown in FIG.

When the temperature decreases and the yoke 3 and fixed iron core 6 become below the Curie point Tc and become magnetic again, the reed switch 11 becomes conductive. If the power source remains connected, the exciting coil 1 generates magnetic flux again and the movable iron core 7 attracts the fixed iron core 6. In this way, a solenoid that can prevent the excitation coil 1 from burning out or catching fire is obtained.

FIG. 3 shows another embodiment of a solenoid according to the invention, in which a different assembly 14 is used in place of the reed switch/magnet assembly 10 of FIG. That is, a rod-shaped magnet 16 magnetized in the longitudinal direction is placed in the center of the glass tube of the reed switch 15 and brought into contact with the center of the bottom surface of the yoke 3 so that the direction of magnetization is parallel to the axial direction of the glass tube. be. Further, the lead end of the reed switch 15 is connected in parallel to the exciting coil 1.

The action of the solenoid with this configuration is such that when the yoke 3 and fixed iron core 6 are below the Curie point Tc, the magnet 1
6 is short-circuited by the yoke 3, almost no magnetic flux flows to the reed switch side, and the contacts are in an open state. When the power is connected, current flows to the excitation coil 1 and the movable iron core as shown in Figure 3. 7 is adsorbed to the fixed iron core.

When the temperature of the yoke 3 and the fixed iron core 6 reach their Curie point, most of the magnetic flux from the magnet 16 flows through the contact part of the reed switch 15, the contact is closed, and the current flowing through the excitation coil 1 reaches the reed switch. 15, and the movable core 7 is separated from the fixed core 6 by the biasing force of the spring 9.

When the temperature decreases and the yoke and fixed core 6 exhibit magnetism, the reed switch 15 is opened, the exciting coil 1 generates magnetic flux again, and the movable core 7 is displaced.

As is clear from the above description, the entire yoke 3 does not need to be made of a temperature-sensitive magnetic material, and it is sufficient if at least the fixed core 6 of the bottom portion 3' of the yoke 3 is made of a temperature-sensitive magnetic material.

As explained above, the solenoid according to the present invention is extremely advantageous as a solenoid having a simple structure, high reliability, and a self-recoverable overheat prevention function.

[Brief explanation of drawings]

FIGS. 1 and 2 show an embodiment of the solenoid according to the present invention, and are schematic configuration diagrams showing an adsorption state below the cutoff temperature and a separation state above the cutoff temperature, respectively. FIG. FIG. 3 is a schematic configuration diagram showing an adsorption state. In the figure, 1: excitation coil, 2: cylindrical bobbin, 3: bottomed cylindrical yoke, 3': its bottom, 4:
Lid body made of annular yoke, 6: Temperature-sensitive magnetic fixed core, 7: Movable core, 9: Recovery spring, 10 , 14 :
Reed switch, magnet assembly, 11, 15: reed switch, 12, 13, 16: magnet.

Claims (1)

[Claims] 1: an excitation coil wound around a bobbin; a fixed iron core provided at one open end of the bobbin; a movable iron core inserted into the fixed iron core from the other open end of the bobbin so as to be removable; A solenoid comprising a yoke surrounding an excitation coil and closing an opening on the fixed core side of the bobbin, wherein the yoke and the fixed core are made of a temperature-sensitive magnetic material having a required Curie point; A reed switch equipped with a permanent magnet is attached to a position facing the fixed iron core of the yoke so that the contact portion of the reed switch is located approximately on the axis of the bobbin, and the excitation coil and reed switch are electrically connected. A solenoid with a self-recoverable function characterized by a self-recovery function.