JPH043258Y2 - - Google Patents

Description

[Detailed explanation of the idea] [Technical field of invention] The present invention relates to a speed sensor.

[Technical background of the invention and its problems] A conventional speed sensor is constructed as shown in FIG. That is, a movable element 2 made of a rod-shaped alnico permanent magnet is inserted into a fixed coil 1, and it is connected to a part to be measured (not shown) via a member 3, and the movement of the movable element 2 causes the coil 1 to move. Measure the voltage induced in the This voltage is
Since it is a function of the speed of , the speed can be determined by the above measurement.

Although the speed sensor with this configuration has a simple structure, the output corresponding to the speed is not necessarily at a high level, and the signal output at low speeds is sometimes masked by noise. In addition, a long movable element is required to make a speed sensor for a long stroke, but it is difficult to manufacture long rod-shaped permanent magnets of uniform quality, resulting in high costs. Furthermore, it has the disadvantage of making it easier to directly pick up external fluctuating magnetic fields, resulting in a high noise level.

[Purpose of the invention] The invention was created based on the above circumstances.
The object of the present invention is to obtain a speed sensor that has a high output level with respect to speed, can be provided at low cost even for long strokes, and is not easily affected by external fluctuating magnetic fields.

[Summary of the invention] The speed sensor of the invention includes a cylindrical fixed yoke, a coil mounted concentrically within the fixed yoke, and a coil that penetrates an end wall provided at one end of the fixed yoke and is inserted into the fixed coil. The movable iron core is inserted into the movable iron core, and a permanent magnet is attached to the tip of the movable iron core and magnetized in the radial direction of the movable iron core.

[Embodiment of the invention] In FIG. 2, a fixed yoke 12 is installed in a fixed yoke 11 which is cylindrical with one end closed and has a through hole 11a at the center of the closed end surface, and a fixed yoke 12 is installed inside the coil 12. A round bar-shaped movable iron core 14 is inserted into the tip of which a ring-shaped permanent magnet 13 magnetized in the radial direction is concentrically attached. A member 15 for coupling with a portion to be measured is attached to the base end of the movable core 14.

Even in the speed sensor of the present invention having the above configuration, the speed can be determined by the voltage induced in the fixed coil 12 by the movement of the movable iron core 14, as in the case of the conventional speed sensor.

Therefore, in the present invention, the fixed yoke 11,
Since the magnetic circuit is formed by the movable iron core 14, the amount of magnetic flux crossing the coil 12 increases,
Output becomes higher. Also, when using a long stroke type, there is no need to use a long bar-shaped magnet.
Magnets are easy to manufacture and can be provided at low cost. Moreover, in this case, the performance can be stabilized and the accuracy can be increased. Furthermore, the external fluctuating magnetic field
1 and does not directly pass through the coil 12, the noise level can be lowered.

Note that the present invention is not limited to the above embodiments. For example, if it is difficult to manufacture a ring-shaped magnet that is magnetized in the radial direction, a fan-shaped permanent magnet 15 obtained by dividing a ring in the radial direction may be attached to the tip of the movable core, as shown in FIG. .

Moreover, instead of the movable core having the above-mentioned configuration, a movable core made of an iron chromium-based or alnico-based permanent magnet similar to that shown in FIG. 1 may be used. In this case, dimension A in FIG. 2 may be at least five times the diameter of the movable core.

[Effects of the Invention] As is clear from the above, the speed sensor of the present invention has a large output and a low noise level, and therefore can detect speed with high accuracy even at low speeds.

[Brief explanation of drawings]

Fig. 1 is a sectional view of a conventional speed sensor, Fig. 2 is a sectional view of an embodiment of the present invention, and Fig. 3 is a front view thereof.
FIG. 4 is a front view of the main part of the modified example. 11...Fixed yoke, 12...Coil, 13...
...Permanent magnet, 14...Movable iron core.

Claims (1)

[Scope of utility model registration request] A cylindrical fixed yoke, a coil mounted concentrically within the fixed yoke, a movable core inserted into the fixed coil through an end wall provided at one end of the fixed yoke, and the movable core. A speed sensor comprising: a permanent magnet attached to a tip of a movable iron core and magnetized in a radial direction.