JPS6215131B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a temperature sensor that converts temperature changes into electrical signals. The need to convert temperature changes into electrical signals and perform temperature control frequently arises in applications such as air conditioning, protection of semiconductor integrated circuit boards from temperature rises, and fire alarms. As temperature sensors for such applications, reed switches using bimetals, thermistors, and thermal ferrites are known. However, bimetals have the drawback of increasing their size, so they tend to be replaced by thermistors or thermal ferrite reed switches. In this reed switch, a reed piece made of magnetic material is enclosed in a container.
Ferrite whose composition has been adjusted so that the Curie point drops to a low temperature close to room temperature, for example, is placed adjacent to the outside of the container, and an external magnetic field is generated from the ferrite and applied to the lead piece when the temperature changes to pass the Curie point. temperature control or temperature alarm is performed by causing the reed to disappear from the reed piece and then opening and closing the reed switch at a predetermined temperature. However, there is a limit to the miniaturization of this reed switch, and it cannot be miniaturized to the extent that it can be mounted on a semiconductor substrate, for example. Additionally, thermistors have the disadvantage of relatively large variations in characteristics. The present invention improves on conventional temperature sensors and provides a temperature sensor based on an entirely new temperature sensing principle. The temperature sensor according to the present invention includes: a permanent magnet; first and second magnetic flux path sections made of a soft magnetic material and installed opposite to two magnetic poles of the permanent magnet;
A rare earth cobalt alloy polycrystal whose easy magnetization direction changes depending on temperature is disposed opposite to one magnetic pole of the permanent magnet via a first magnetic flux path made of the soft magnetic material, and The direction of the magnetic field lines and the C axis of the crystal are perpendicular or parallel,
a third magnetic flux passage portion whose bottom surface is parallel or perpendicular;
The permanent magnet is made of the rare earth cobalt alloy polycrystal whose direction of easy magnetization changes depending on the temperature, and the C-axis is parallel or perpendicular to the direction of the magnetic field lines, and the bottom surface is perpendicular or parallel to the direction of the magnetic field lines. and a fourth magnetic flux passage section having tropism, and the first magnetic flux passage section made of the soft magnetic material is arranged between the one magnetic pole and the third magnetic flux passage section or the fourth magnetic flux passage section. The second magnetic flux passage section made of the soft magnetic material forms a magnetic coupling between the other magnetic pole of the permanent magnet and the fourth magnetic flux passage section, and the magnetic flux generation section made of the permanent magnet A temperature-magnetic field converter comprising a magnetic flux passage section made of a material whose easy magnetization direction changes depending on the temperature, and a magnetic flux passage section made of a soft magnetic material, the magnetic flux passage section comprising a magnetic flux passage section made of a material whose easy magnetization direction changes depending on the temperature, and a magnetic flux passage section made of a soft magnetic material. A temperature/magnetic field converter is provided by combining the above parts so that the magnetic flux passes through the converter on one of the high temperature sides, and leaks out of the converter on the other side, and further includes a magnetoelectric converter. It is characterized by having a container. One feature of the temperature sensor of the present invention is that a ferromagnetic material whose direction of easy magnetization changes depending on temperature is used for the magnetic flux path portion. It is well known that among ferromagnetic materials, there are crystals that have large magnetic anisotropy and whose direction of easy magnetization changes with temperature. Typical materials include rare earth cobalt alloys (PrCo ₅ , NdCo ₅ , TbCo ₅ , DyCo ₅ , HoCo ₅ ,
Lu ₂ Co ₁₇ , Tm ₂ (Fe ₁ −xCox) ₁₇ , etc.). The general formula for rare earth cobalt alloys is RnCom. R is one or more rare earth elements. Some of the cobalt may be replaced with iron, copper, vanadium, or other metals. The magnetic anisotropy of a rare earth cobalt alloy single crystal will be explained below with reference to the drawings. In the drawings, in Figure 1, black circles represent R atoms and white circles represent Co atoms.
1 is a drawing showing the crystal structure and easy magnetization direction of RCo ₅ type rare earth cobalt alloy. FIG. 2 is a graph showing the temperature dependence of the easy magnetization direction of the RCo ₅ type rare earth cobalt alloy, and FIG. 3 is a graph similar to FIG. 2 for the R ₂ Co ₁₇ type rare earth cobalt alloy. In FIG. 1, an RCo ₅ type rare earth cobalt crystal having a CaCu ₅ type hexagonal crystal structure is illustrated. In rare earth cobalt alloys used as permanent magnets, the magnetic anisotropy is generally along the C-axis (A-axis) of the crystal.
) is the easy axis of magnetization, and has an extremely large magnetic anisotropy constant, and the direction of the difficult axis of magnetization is several
Magnetization does not saturate unless a magnetic field of 100KOe is applied.
However, depending on the type of R and the type and amount of elements substituted for Co, the axis of easy magnetization changes depending on the temperature.
It may move to a conical plane (abbreviation of C-Cone) or to a conical plane (abbreviation of C-Cone). The R ₂ Co ₁₇ type rare earth cobalt alloy has a hexagonal or rhombohedral crystal depending on the composition and temperature, but magnetic anisotropy is determined by the temperature at which the axis of easy magnetization is either the C axis, basal plane, or conical plane of the crystal. Show dependencies. Figures 2 and 3 show RCo ₅ type and
The change in the easy axis of magnetization of R ₂ Co ₁₇ type rare earth cobalt alloy due to absolute temperature is the above symbol A (C axis direction),
It is shown using C (conical surface) and P (base surface) (Bulletin of the Japan Institute of Metals Vol. 16 (1977) No. 2 79
page). Note that the dotted line in the same figure means undecided or speculation. In the case of RCo ₅ type rare earth cobalt alloy, the magnetic anisotropy shows temperature dependence when the rare earth element is Pr, Nd, Tb, Dy, or Ho. R ₂ Co ₁₇
In rare earth cobalt alloys, when the rare earth element is Lu, the magnetic anisotropy exhibits temperature dependence. The magnetic anisotropy change temperature can be adjusted depending on the type of rare earth element. In the R ₂ Co ₁₇ type rare earth cobalt alloy shown in FIG. 3, the magnetic anisotropy change temperature can be adjusted by adding additive elements such as copper, iron, vanadium, etc. to the R ₂ Co ₁₇ type alloy. The following table shows the change in the easy axis of magnetization at room temperature when cobalt in R ₂ Co ₁₇ type rare earth cobalt alloy is replaced with iron.

[Table] Another feature of the present invention is that an anisotropic material made of a rare earth cobalt alloy polycrystal whose easy magnetization direction changes depending on temperature is used as the third and fourth magnetic flux passage parts, and the base surface The purpose is to switch the direction of magnetic flux within the temperature/magnetic field converter by utilizing the fact that the direction of easy magnetization changes from C to C-axis direction or vice versa. Specifically, two or more metal pieces made of a rare earth cobalt alloy are used, and when either the C-axis or the base surface, preferably the C-axis, is in the easy magnetization direction, the magnetic flux of the permanent magnet is At a temperature where either the C-axis or the basal plane is in the direction of easy magnetization, the magnetic flux escapes to the outside of the temperature/magnetic field converter along one of the axes or planes of the metal piece. Arrange the metal pieces so they don't escape. Another feature of the present invention is that a soft magnetic material (of course, the direction of easy magnetization does not change with temperature) is used as the first and second magnetic flux passage sections. The first and second magnetic flux paths made of this soft magnetic material form a closed loop of magnetic flux together with some of the rare earth cobalt alloy pieces, and have the function of completely confining the magnetic flux within the temperature/magnetic field converter. In other words, if the closed loop is composed only of rare earth cobalt alloys and permanent magnets, the magnetic flux will leak slightly to the outside of the temperature/magnetic field converter, resulting in a decrease in the sensitivity of temperature change detection. Next, other features of the present invention will be explained based on the drawings. In FIG. 4, first and second magnetic flux passage portions 3 and 3' made of a soft magnetic material such as permalloy are provided oppositely to two magnetic poles N and S of a permanent magnet 4, respectively. A fourth magnetic flux passage section 1 is installed opposite to one magnetic pole N of the permanent magnet 4 via a first magnetic flux passage section 3 made of a soft magnetic material. The fourth magnetic flux path section 1 is made of a rare earth cobalt alloy crystal whose easy magnetization direction changes depending on the temperature,
It has anisotropy such that the direction of the magnetic field lines from the crystal is parallel to the C axis (arrow) of the crystal, and the bottom surface is perpendicular. By the way, in rare earth cobalt alloys used as permanent magnets, the C-axis direction is the easy magnetization direction at room temperature or below. By pressing an alloy in which the C axis is the axis of easy magnetization below room temperature in a magnetic field at room temperature, an anisotropic magnetic flux path in which the easy magnetization directions of substantially all crystals of the polycrystalline material are aligned can be obtained. In order to detect temperature changes at higher temperatures than around room temperature, when compacting fine powder of a rare earth cobalt alloy ferromagnetic material whose magnetic anisotropy changes at the detection temperature in a magnetic field, the pressure must exceed the temperature at which the direction of easy magnetization changes. It is necessary to warm the powder in the powder. By doing so, it is possible to obtain a compacted powder material in which the directions of easy magnetization are aligned. If this is sintered by a conventional method, an anisotropic sintered rare earth cobalt alloy whose basal plane is aligned with the C-axis direction is produced. The third magnetic flux passage section 2 is made of the rare earth cobalt alloy crystal, which is placed opposite to the side surface of the permanent magnet 4 and whose direction of easy magnetization changes depending on the temperature. In FIG. 5A, at a temperature where the base surfaces (perpendicular to the C axis) of the rare earth cobalt alloy of the third and fourth magnetic flux passage sections 1 and 2 are in the direction of easy magnetization, the N and S poles of the permanent magnet 4 are The magnetic flux between the first and second magnetic flux passage parts 3, 3', the third and fourth magnetic flux passage parts 2,
1, forming a closed loop that does not leak to the outside of the temperature/magnetic field converter 10. On the other hand, when the C-axis is in the direction of easy magnetization, the magnetic flux flows to the outside from the third magnetic flux passage section 2, as shown in FIG. 5B. If a known Hall element is placed at a position where this leakage magnetic flux can be detected, temperature can be detected by turning the current ON and OFF. This third magnetic flux passage section 2
has anisotropy such that the C axis is perpendicular to the direction of the magnetic field lines from the permanent magnet 4, and the bottom surface P is parallel to the direction. First magnetic flux passage section 3 made of soft magnetic material
forms a magnetic coupling between the magnetic pole N and the third magnetic flux passage section 2 or the fourth magnetic flux passage section 1, and the second magnetic flux passage section 3' made of a soft magnetic material is connected to the permanent magnet 4.
A magnetic coupling is established between the other magnetic pole S and the third magnetic flux passage section 2. FIG. 6 shows an example in which the arrangement of the third magnetic flux passage section 2' and the first magnetic flux passage section 3 is changed. FIG. 7 shows a specific example in which a Hall element 20 is arranged between two temperature/magnetic field converters 10 to constitute a temperature sensor. Note that it is not always necessary to use two converters 10. When the temperature sensor according to the present invention is formed into a shape suitable for mounting on a semiconductor circuit board, the Hall element 20 having the pin 21 is connected to the converter 10 as shown in FIG.
There will be a structure sandwiched between them. The overall dimensions of this temperature sensor are, for example, 10 mm in length, 5 mm in width, and 5 mm in thickness, making the temperature sensor extremely compact. This miniaturization has been made possible largely due to the fact that a rare earth cobalt alloy with high saturation magnetization is arranged as the magnetic flux path portion of the temperature sensor. Furthermore, the detection temperature of the sensor can be selected over a very wide range by adjusting the composition of the rare earth cobalt alloy. Furthermore, since the rare earth cobalt alloy has extremely high magnetic anisotropy, temperature detection sensitivity is significantly increased. From the above description, it will be clear that the temperature sensor of the present invention significantly outperforms conventional temperature sensors.

[Brief explanation of the drawing]

Figure 1 is a drawing showing the structure and easy magnetization direction of a single crystal of RCo ₅ type rare earth cobalt alloy. However, black circles represent R atoms, white circles represent Co atoms, and
The figure is a graph showing the temperature dependence of the easy magnetization direction of the RCo ₅ type rare earth cobalt alloy, Figure 3 is a graph similar to Figure 2 for the R ₂ Co ₁₇ type rare earth cobalt alloy, and Figure 4 is the graph of the temperature sensor of the present invention. 5A and 5B are conceptual diagrams illustrating changes in magnetic flux in FIG. 4, and FIGS. 7 is a sectional view of a temperature sensor according to one specific example, and FIG. 8 is a perspective view of a temperature sensor according to one specific example. DESCRIPTION OF SYMBOLS 1...Fourth magnetic flux passage part, 2... Third magnetic flux passage part, 3... First magnetic flux passage part, 3'... Second magnetic flux passage part, 4... Permanent magnet.

Claims (1)

[Claims] 1. A permanent magnet; first and second magnetic flux path sections made of a soft magnetic material and placed opposite to each other on two magnetic poles of the permanent magnet; made of the soft magnetic material at one magnetic pole of the permanent magnet; Made of rare earth cobalt alloy polycrystals whose easy magnetization direction changes depending on temperature, which are disposed opposite to each other via a first magnetic flux path section,
The direction of the magnetic field lines from the one magnetic pole and the C of the crystal
a third magnetic flux passage section whose axes are perpendicular or parallel and whose bottom surfaces are parallel or perpendicular; consisting of the rare earth cobalt alloy polycrystal whose easy magnetization direction changes depending on the temperature, which is disposed opposite to the side surface of the permanent magnet; The fourth material has anisotropy in which the C-axis is parallel or perpendicular to the direction, and the base is perpendicular or parallel to the direction of
and a first magnetic flux path section made of the soft magnetic material that forms a magnetic coupling between the one magnetic pole and the third magnetic flux path section or the fourth magnetic flux path section. , the second magnetic flux passage section made of the soft magnetic material forms a magnetic coupling between the other magnetic pole of the permanent magnet and the fourth magnetic flux passage section, and the magnetic flux generation section made of the permanent magnet is easily magnetized depending on the temperature. A temperature-magnetic field converter comprising a magnetic flux passage section made of a material whose direction changes and a magnetic flux passage section made of a soft magnetic material, which are either on a lower temperature side or a higher temperature side than the temperature at which the magnetic anisotropy changes. A temperature/magnetic field converter is provided by combining each of the above parts so that the magnetic flux passes through the converter and leaks out of the converter on the other hand, and a magnetoelectric converter is further provided. A temperature sensor that converts temperature changes into electrical signals.