JPH02115719A - Rotation detector - Google Patents

Abstract

PURPOSE:To stabilize pulses by arranging the face where a resistor pattern is formed of a magnetoresistance element in parallel with the magnetization repeating direction of a magnet. CONSTITUTION:A resistor pattern 6 consisting of current passages 8 and 9 is formed on one face 7 of a magnetoresistance element 4, and these passages 8 and 9 are so arranged that their longitudinal directions are intersected orthogonally with each other, and they are connected in series. This element 4 is mounted on a circuit board 13 having an electronic circuit on its front face 13a, and the face 7 is perpendicular to the surface 13a. A rear face 13b of the board 13 is arranged closely to a magnetic recording medium 3 approximately in parallel with its outer periphery magnetized face, and the face 7 is arranged in the magnetization repeating direction of the medium 3. Thus, when a rotating body 1 is rotated, the medium 3 is rotated integrally and a rotating magnetic field whose direction is changed on the face 7 is generated. The resistance value of the element 4 is changed approximately symmetrically with respect to the center value of this change of the magnetic field in accordance with this change, and the center value and the distance between the medium 3 and the element 4 are fixed for the ambient temperature, and output pulses of the electronic circuit are stabilized to have 50% duty ratio.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a rotation detection device for detecting the number of rotations and rotation speed of a rotating body.

[Prior art]

In the conventional rotation detector, as shown in FIG.
The surface of the magnetoresistive element on which the resistor pattern was formed was arranged parallel to the magnetized surface of the magnet or magnetic recording medium 3. In the figure, 1 is a rotating body, 2 is a disk that rotates together with the rotating body 1, and 3 is a multi-pole magnetized magnet or magnetic recording medium on the outer periphery of the disk 2.

Magnetoresistive elements generate magnetic fields when a magnetic field sufficient to saturate the ferromagnetic material is applied in the longitudinal direction of the ferromagnetic material, that is, in a direction intersecting the current direction at a certain angle, on a plane on which a resistor pattern is formed. The resistance of a ferromagnetic material has the property of changing depending on the angle (for example, Japanese Patent Application Laid-Open No. 50-2898
(See Publication No. 9).

[Problems to be solved by the present invention]

In the conventional rotation detector as shown in FIG. 7) The direction of the magnetic field never changes by 90 degrees. Therefore, it is not possible to make a large change in the electrical resistance of the magnetoresistive element, and the changing waveform is not a sine wave but a distorted one, and the output pulse width obtained through the waveform shaping circuit varies depending on the distance between the magnetic recording medium and the magnetoresistive element, or the ambient temperature. There was a problem in that it was difficult to obtain a stable output pulse with a duty ratio of 50%. This is inconvenient for signal processing in subsequent electronic circuits.

Furthermore, since the leads of the magnetoresistive element 4 are connected to an electronic circuit (not shown), a certain length of lead is required, and there is also the problem that the lead is easily affected by electrical noise.

Another problem is that the magnetoresistive element is easily damaged by accidentally contacting the magnetic recording medium 3 or a magnet.

An object of the present invention is to propose a circuit detection device that can solve these problems.

[Means to solve the problem]

In order to achieve the above object, the rotation detecting device of the present invention includes a multi-pole magnetized magnet or magnetic recording medium on the outer periphery of a disk or cylinder that rotates together with a rotating body, and a magnet or magnetic recording medium. It consists of a magnetoresistive element placed close to the medium and an electronic circuit that amplifies the resistance change of the magnetoresistive element and outputs a pulse signal, and the surface of the magnetoresistive element on which the resistor pattern is formed is a magnet or magnetic recording It is arranged parallel to the direction of repeated magnetization of the medium.

In the magnetoresistive element, the main resistor pattern is composed of first and second current paths each made of a ferromagnetic material having a magnetoresistive effect, and these current paths are arranged so that their longitudinal directions are perpendicular to each other and are electrically conductive. It is effective to use a device in which the terminals are connected in series, and current supply terminals are provided at both ends of this series connection, and output terminals for taking out the output voltage are provided at the connection points of the first and second current paths. be.

[Effect]

In the rotation detecting device configured as described above, when the rotating body rotates, the multi-pole magnetized magnet or magnetic recording medium rotates together on the outer periphery of the disk or cylinder. Therefore, a rotating magnetic field whose direction changes in the plane in which the resistor pattern is formed is generated in the magnetoresistive element. The resistance value of the magnetoresistive element changes in response to changes in this magnetic field. The resistance change changes symmetrically with respect to the median value of the change, and the median value remains approximately constant depending on the distance between the magnetic recording medium and the magnetoresistive element and the ambient temperature, and the output pulse of the electronic circuit has a duty ratio of 50. % stable.

According to the second aspect of the present invention, since the directions of changes in the resistance values of the first and second current paths due to the magnetic field are opposite to each other, a large output voltage can be obtained at the output terminal of the connection point. Therefore, it is ideal for performing switching operations to obtain pulse signals in electronic circuits, and output pulses with a more stable duty ratio can be obtained.

In the third aspect of the present invention, since the back surface of the circuit board is placed close to the magnetic recording medium, there is no risk that the magnetoresistive element itself will come into contact with the rotating part. Furthermore, since surface mounting technology is used for electrical connection between the magnetoresistive element and the electronic circuit of the circuit board, and there is no need to use lead wires, there is no risk of electrical noise being mixed in.

According to the fourth aspect of the present invention, the magnetic field applied to the resistor pattern can be made strong, so that the detection sensitivity can be increased.

〔Example〕

In Figs. 1 (A) to (D), 1 is a rotating body, 2 is a disk that rotates together with the rotating body l, 3 is a magnetic recording medium with multipolar magnetization on its outer periphery, and 4 is a magnetoresistive element. , first and second
The resistor pattern 6 consisting of the current path 8.9 is connected to the − plane 7.
is formed.

As is clear from the figure (D), the two types of flow passages 8.9 are arranged so that their longitudinal directions are orthogonal to each other, and are electrically connected in series, with current supply terminals to,
ii, and the connection point is output terminal 1 for taking out the output voltage.
2 are provided respectively.

This magnetoresistive element 4 is surface mounted on a circuit board 13 having an electronic circuit on its surface 13a, and the surface 7 having the resistor pattern 6 is perpendicular to the surface 13a of the circuit board 13. The back surface 13b of the circuit board 13 is placed close to the magnetic recording medium 3 and parallel to the outer circumferential magnetized surface of the magnetic recording medium 3. Further, one surface 7 of the magnetoresistive element 4 is arranged parallel to the magnetization repetition direction of the magnetic recording medium 3, that is, the circumferential direction.

When the disk 2 rotates, the direction of the magnetic field applied to the resistor pattern 6 of the magnetoresistive element 4 changes. (B) and (C)
), the direction of this magnetic field is 90 degrees different.

FIG. 2 shows an electronic circuit 5 that amplifies the resistance change of the magnetoresistive element 4 and converts it into a pulse signal. Since the circuit itself is well known, a detailed explanation will be omitted, but the output pulse is as shown in the figure. It is a rectangular wave with a duty ratio of 50%. Note that FIG. 9 shows the output waveform of the amplifier 5a in the same figure. In the electronic circuit 5, noise countermeasure components (not shown) are provided on the circuit board 13.

Note that the electronic circuit 5 provided on the surface 13a of the circuit board 13 is omitted and not shown in FIGS. 1(A), 1(B), and 1(C).

FIG. 3 shows an example of a magnetoresistive element equipped with a lead frame to support surface mounting technology. As shown in FIG.
It is soldered to 0.11.12. The symbol 17° indicates the soldered part. Figure (B) shows the state before the lead frame is attached. In this example, the bent portion of the lead frame 14, 15, 16]4a.

15a and 16a on the surface 13 of the circuit board 13 in FIG.
Place it on board a and solder it for surface mounting. The electronic circuit board 13 can be a printed wiring board or a thick film printed board. In the example shown in Figure 3, the insulating substrate of the magnetoresistive element is sandwiched between the lead frames, the electrodes (terminals) are soldered,
Since the bent portion of the lead frame extends perpendicularly from the surface of the insulating board, when surface mounting on the circuit board 13,
This bent portion acts to allow the magnetoresistive element to stand on its own.

Therefore, it can be easily reflow soldered together with other electronic components during mounting.

Further, in this example, the resistor pattern 6 is arranged closest to the surface of the circuit board 13.

Figures 4 (A) and (B) show the lead frame 14°1
5 and 1.6 are different from those shown in FIG. Furthermore, although the positional relationship of the resistor pattern 6 with respect to the lead frame is different, they have the same effect.

In the examples shown in FIGS. 3 and 4, the element 4 may be plastic molded so that only the bent portion of the lead frame is exposed.

The example shown in FIG. 5 is an example in which the terminal 10 of the magnetoresistive element 4 is extended to the end surface 17a of the insulating substrate 17, and other terminals '11.
By doing the same with 12, the reliability of the connection when mounted on the circuit board 13 is increased. In this way, the insulating substrate 17 of the magnetoresistive element 4 is directly attached to the circuit board 1.
3, a slightly thicker insulating board 17 is used so that the insulating board 17 can easily stand on its own on the circuit board 13. FIG. 6 shows a state in which the magnetoresistive element 4 of FIG. 5 is mounted on the surface of a circuit board 13, with 18 representing solder and 19 representing a solder land.

Note that in order to make the element 4 easy to stand on its own, the front or back side of the element 4 may be supported by plastic, a ceramic chip, an L-shaped metal piece, or the like.

FIG. 7 shows an example in which the magnetoresistive element 4 is surface-mounted on the circuit board 13 via another chip component.As shown in FIG. The magnetoresistive element 4 is surface-mounted perpendicularly to the circuit board 13 by soldering the magnetoresistive element 4 and then reflow soldering onto the circuit board 13 as shown in FIG. Reference numeral 20 indicates a reflow soldered part. Further, reference numeral 21 indicates a solder for soldering the terminal 10 of the magnetoresistive element 4 to the electrode 18 of the ceramic chip 19.

In the various embodiments described above, surface mount technology was used, so
Circuit board 13 on which magnetoresistive element 4 and other electronic components are mounted
We were able to reduce the overall dimensions, including the thickness, to 31 layers.

〔Effect of the invention〕

Since the present invention is configured as described above, it produces the effects described below.

By arranging the surface of the magnetoresistive element on which the resistor pattern is formed parallel to the direction of repeated magnetization of the magnet or magnetic recording medium, the magnetic field that acts on the resistor pattern is effectively applied, thereby reducing the duty ratio of the output pulse signal. A stable pulse of 50% can be obtained.

Furthermore, the magnetoresistive element is surface mounted perpendicularly to the circuit board,
If the circuit board is placed parallel to the outer magnetized surface of a magnet or magnetic recording medium, and its back surface is placed close to the outer magnetized surface, the magnetoresistive element itself becomes a rotating part during assembly or during use after assembly. This is convenient because it prevents you from getting hurt by touching it.

Furthermore, by surface mounting the magnetoresistive element on the circuit board, the overall thickness of the circuit portion can be reduced, and the overall dimensions including the rotating recording medium can be reduced, resulting in better cohesion. Further, since the magnetoresistive element and the electronic circuit are close to each other, noise resistance is improved.

Furthermore, if the resistor pattern of the magnetoresistive element is arranged close to the circuit board and off-centered, the magnetic field will act more strongly on the resistor pattern, so a more stable output can be expected.

[Brief explanation of drawings]

1 to 8 show embodiments of this invention, and FIG. 1(A)
1 is a perspective view of one embodiment; FIGS. 2B and 2C are plan views showing different rotational positions of the magnetic recording medium; FIG. 1D is a plan view showing details of the magnetoresistive element; Figure 2 is an electric circuit diagram, Figure 3 (A) is a perspective view of an example in which a lead frame is attached to a magnetoresistive element, Figure 3 (B) is a diagram before the lead frame is attached, Figure 4 (A) is a perspective view showing another example in which a lead frame is attached to a magnetoresistive element;
B) is a view before the lead frame is attached, Figure 5 is a side view showing another example of the magnetoresistive element, Figure 6 is a side view of the magnetoresistive element shown in Figure 5 mounted on a rotating board, and Figure 7. 8 is a perspective view of the ceramic chip of FIG. 7, FIG. 9 is a diagram showing waveforms of the electronic circuit of FIG. 2, and FIG. 10 is a diagram of the conventional technology. FIG. DESCRIPTION OF SYMBOLS 1... Rotating body, 2... Enwa, 3... Magnetic recording medium, 4... Magnetoresistive element, 5... Electronic circuit, 6...
Resistor pattern, 7... Surface, 8... First current circuit, 9... Second current circuit, 10.11... Current supply terminal, 12... Output terminal, 13...・Circuit board, 13
a...front side, 13b...back side

Claims (4)

[Claims] 1. A magnet or magnetic recording medium (3) magnetized with multiple poles on the outer periphery of a disk or cylinder that rotates together with the rotating body (1), and a magnetoresistive element (4) disposed close to the magnet or magnetic recording medium. ) and an electronic circuit (5) that amplifies the resistance change of the magnetoresistive element (4) and outputs a pulse signal,
A rotation detection device in which a surface (7) of a magnetoresistive element (4) on which a resistor pattern (6) is formed is arranged parallel to the direction of repeated magnetization of a magnet or a magnetic recording medium (3). 2. 2. The rotation detecting device according to claim 1, wherein the magnetoresistive element (4) has main resistor patterns (6) each made of a ferromagnetic material having a magnetoresistive effect. 3. A surface (7) on which the magnetoresistive element (4) is formed with its resistor pattern (6) is placed on the surface (13a) of the circuit board (13) on which the electronic circuit (5) is formed.
) is mounted vertically, and the circuit board (13)
is approximately parallel to the outer circumferential magnetized surface of the magnet or magnetic recording medium (3), and is located on the back surface (13b) of the circuit board (13).
) is arranged close to the outer circumferential magnetized surface. 4. The rotation detection device according to claim 3, wherein the resistor pattern (6) of the magnetoresistive element (4) is arranged close to the circuit board (13).