JP2000275059A - Magnetic sensor and magnetic encoder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify gap adjustment, and to obtain a magnetic encoder with high detection accuracy by setting the thickness of the resin part of a flexible printed circuit FPC while the thickness is equal to the gap interval between a magnetic sensor and a magnetic record medium. SOLUTION: For example, in the outer-periphery direction of the surface of a magnetic medium 1, a magnetic pole is polarized so that N and S oppose N and S, respectively, like NSSNNS, and a polarizing pitch λ should be set to approximately 38 μm. The magnetic medium 1 is fixed to a shaft 9 and is rotated with the rotation of the shaft 9. A magnetic sensor 2 is arranged opposite to the magnetic medium 1 so that the thickness of a resin part 15 of an FPC is set to a gap (g). At this time, the resin part 15 of the FPC also adheres to a magnetic sensor element, and the gap (g) is formed by the thickness of the resin part 15 of the FPC. In this manner, an FPC 11 with the resin part 15 of the FPC for covering the surface of a magnetic sensor element 3 is used, thus easily limiting the small gap (g) to approximately 25 μm without changing the thermocompression bonding process of the FPC and the magnetic sensor element.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a configuration of a magnetic sensor used for detecting a position or a speed by combining a magnetic drum or a magnetic scale, and in particular, by bringing a magnetic drum or a magnetic scale into contact with a magnetic sensor. The present invention relates to a magnetic sensor and a magnetic encoder used.

[0002]

2. Description of the Related Art As shown in FIG. 7, a magnetic encoder includes a magnetic medium 1 in the form of a drum or scale, a magnetic sensor element 3, and a flexible printed circuit 4.
An appropriate interval (hereinafter, referred to as a gap g) is required. Generally, the gap g refers to the distance between the magnetoresistive element 5 and the magnetic medium, but in the present invention, as shown in FIG. 7, the nonmagnetic film 6 provided for protecting the magnetoresistive element 5 is provided. Means the distance between the surface and the magnetic medium.

From the relationship between the magnitude of the output from the magnetic sensor and the distortion of the waveform, there is a relationship of g = 0.5 to 0.8λ between the magnetization pitch λ of the magnetic medium and the optimum gap g. FIG.
FIG. 7 shows the relationship between the output voltage of the magnetic sensor when the magnetization pitch λ of the magnetic medium is 40 μm and the distance between the magnetic sensor and the magnetic medium is changed. The gap g is about 1 / of the magnetized pitch λ.
If it is less than 2, the output waveform of the sensor will saturate and cause distortion, so even if the gap g is narrowed, the output of the magnetic sensor will not increase. When the gap g is increased to a value substantially equal to the magnetization pitch λ, the magnetic field reaching the magnetoresistive element of the magnetic sensor is weakened, and the force for sensing the magnetic field is weakened, so that the output voltage of the magnetic sensor is reduced. Therefore, in order to obtain a stable sensor output, the gap g is set to g = 0.
It is necessary to keep the range of 5 to 0.8λ to reduce the variation of the output signal of the sensor.

[0004] The magnetic encoder is assembled by adjusting the gap g while measuring the output of the magnetic sensor so that the distortion of the output voltage waveform is small and the output is large.

As another method, a jig having a thickness corresponding to the gap g is prepared, a jig is inserted between the magnetic medium and the magnetic sensor, and the magnetic medium is brought into close contact with the jig and the magnetic sensor. A method of removing a jig after fixing a magnetic sensor by using a method is often used.

There is a method shown in FIG. 8A or 8A). FIG. 8A shows a configuration in which a tetrafluoroethylene-based resin or polyamide-based resin sheet 7 is attached to the outer periphery of the magnetic medium 1. FIG. 8B) shows a method in which a sheet 7 is attached to the magnetic sensor element 3 and the magnetic medium 1 and the magnetic sensor 2 are contacted and slid via the sheet.

A drum type magnetic encoder in which the magnetic sensor 2 and the magnetic medium 1 are combined will be described with reference to FIG.
The magnetic sensor has a structure in which a magnetic sensor element 3 and a flexible printed circuit 4 (hereinafter, referred to as FPC) have a joint 8 formed by thermocompression bonding of the terminal solder of the magnetic sensor element and the terminal solder of the FPC. As shown in FIG. 7, the bonding portion 8 has a shape in which the solder is protruded from the terminal portion so as to protrude due to thermocompression bonding.

FIG. 6 is a perspective view and FIG. 7 is a side view of a rotary magnetic encoder in which a magnetic medium 1 and a magnetic sensor 2 are combined. The magnetic pole is NSS in the outer circumferential direction of the magnetic medium surface.
Like NNS, the magnets are magnetized so that N and N and S and S face each other, and the interval between N and S or S and N is represented by a magnetizing pitch λ. The magnetic medium 1 is fixed to the shaft 9 and rotates with the rotation of the shaft 9. The gap g between the magnetic sensor 2 and the magnetic medium 1
Are arranged so as to face each other with an interval of. FPC
4 is often arranged on the magnetic medium 1 side of the magnetic sensor element 3. From the relationship between the thickness of the FPC and the gap g, the FPC 4 is generally arranged at a position where the FPC 4 is outside the end of the magnetic medium.

The method of adjusting the gap while measuring the output of the magnetic sensor and assembling so that the output voltage waveform distortion is small and the output is large can provide the optimum gap size. The characteristic variation can be absorbed and the characteristic variation as the magnetic encoder can be reduced. However, in the method of adjusting the gap for each magnetic encoder, since the adjustment is performed to the optimum gap while actually checking the sensor output, the number of assembly steps is increased, which hinders the cost reduction.

A jig having a thickness corresponding to the gap was prepared, a jig was inserted between the magnetic medium and the magnetic sensor, and the magnetic sensor was fixed in a state where the magnetic medium, the jig and the magnetic sensor were in close contact with each other. Then, it is easy to adopt a method of removing the jig if the gap g is a large value.
When it is necessary to adjust the distance to a minimum range of about 40 μm, there is a risk of damaging the surface of the magnetic sensor and the recording medium when the jig is removed, so that it is difficult to adopt the jig. Also,
It was also difficult to make a jig having a thickness of 30 to 40 μm.

FIG. 8 shows a method for overcoming these drawbacks, which is to use a sheet of polytetrafluoroethylene resin or polyamide resin.
Is attached to the magnetic medium 1 or the magnetic sensor element 3, and the magnetic medium 1 and the magnetic sensor 2 are contacted and slid via the sheet 7. FIG. 8A shows a structure in which the sheet is attached to the magnetic medium side, and FIG. 8B) shows a structure in which the sheet 7 is attached to the magnetic sensor side. Although the number of steps for attaching the polytetrafluoroethylene-based resin or polyamide-based resin sheet 7 is increased, it is not necessary to attach the sheet at the time of assembling the magnetic encoder as compared with the above-described method, and the sheet can be attached in a separate process. It is easy to do. However, there are many problems to be solved such as processing when the adhesive resin of the sheet 7 protrudes from the sheet.

[0012]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a magnetic encoder having good detection accuracy without complicating the manufacturing process of the magnetic sensor, simplifying the process of adjusting the gap of the magnetic encoder. And

[0013]

The magnetic sensor of the present invention comprises:
A magnetic recording medium having a magnetic recording medium having a predetermined magnetic pattern alternately magnetized in a reverse direction at a constant pitch λ; The resin part of the FPC covers at least a part of the sensor part.

The resin portion of the FPC refers to a region having no metal wiring for a conductor, a region formed of a resin film or a resin film and an adhesive, and a surface of a nonmagnetic film provided for the purpose of protecting the magnetoresistive element. By covering a part or the whole of the area with the resin part of the FPC, the interval between the magnetic sensor and the magnetic recording medium can be secured.

The gap g can be easily obtained simply by making the thickness of the resin part of the FPC equal to the distance between the magnetic sensor and the magnetic recording medium and pressing the magnetic sensor through the magnetic medium and the FPC resin part. Not only the gap adjustment becomes easy, but also the generation of scratches on the surface of the magnetic medium and the magnetic sensor can be prevented.

The thickness of the resin portion of the FPC is determined by a magnetization pitch λ.
By setting the value to 0.2 to 1λ, the distortion of the output waveform from the magnetic sensor can be minimized and a sufficient output voltage can be obtained.

F covering at least a part of the surface of the nonmagnetic film provided for the purpose of protecting the element for sensing magnetism of the present invention.
The resin part of the PC is not fixed by the adhesive, and the gap g can be obtained by deforming to the magnetic sensor side by the pressing force of the magnetic medium and the magnetic sensor, and the gap g is reduced by the thickness of the adhesive. In addition to this, it is possible to omit the steps of applying and fixing the adhesive.

Since the resin portion of the FPC of the present invention protrudes from the end of the magnetic sensor by at least w / 10 of the magnetic sensor width w, the relative movement between the magnetic medium and the magnetic sensor can be improved.
Deformation of the resin portion of the FPC by the slip stick can be prevented, and relative movement between the magnetic medium and the magnetic sensor can be performed smoothly.

The sliding resistance between the magnetic medium and the FPC resin portion can be further reduced in frictional resistance by applying a lubricating oil such as silicone oil.

In the magnetic sensor according to the present invention, the portion of the FPC resin portion protruding from the end of the magnetic sensor is curved with the curved surface toward the magnetic sensor, so that the magnetic medium at the end of the FPC resin portion is free from the magnetic medium. Entanglement of the magnetic sensor on the facing portion is prevented.

The curved surface of the FPC resin portion can be formed at the same time in the process of joining the FPC terminal portion and the solder surface added to the magnetic sensor terminal portion and applying heat and pressure by using a heated jig. Alternatively, a curved surface may be formed on a single FPC in a separate step.

According to the magnetic sensor of the present invention, the overflow of the solder generated when the electrode of the magnetic sensor and the electrode of the FPC are joined by solder is escaped to the notch of the FPC provided near the solder joint. The overflowed solder is F
It is possible to prevent the PC from coming out on the side facing the magnetic medium and to prevent a short circuit between adjacent electrodes. If the solder jumps out even to a part of the FPC on the side facing the magnetic medium, not only does the gap g change, but also the surface of the magnetic medium is damaged. The shape of the notch provided in the FPC is preferably provided in parallel with the moving direction of the magnetic medium, and may be provided in each of a large number of electrode terminals, or one notch may be provided for a plurality of electrodes. Is also a good thing. The shape of the notch includes a structure such as a concave hole, a penetrating hole, and a notch.

In the magnetic encoder of the present invention, the thickness of the resin portion of the FPC provided on the magnetic sensor side is defined as a gap g between the magnetic sensor and the magnetic medium, and the resin portion of the FPC is deformed and brought into close contact with the magnetic recording medium. Thus, the gap can be stably and easily realized.

The magnetic encoder of the present invention can smoothly slide the magnetic medium and the magnetic sensor by setting the force f for pressing the magnetic sensor against the magnetic medium to 10 g or less. 8 g or less is more preferable. With a pressing force of 10 g or more, the abrasion of the resin layer of the FPC increases, and the generation of dust increases. On the other hand, if the weight exceeds 15 g, the sliding of the FPC resin portion and the magnetic medium is not smooth, and the FPC resin portion is pulled in the sliding direction (slip stick).
This is because the C resin portion is damaged.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to embodiments. FIG. 1 shows a magnetic sensor according to an embodiment of the present invention, in which a) is a perspective view, b) is a front view, and c) is a side view. FIG. 2 is a perspective view illustrating a magnetic encoder using the magnetic sensor of the present invention, and FIG. 3 is a side view. FIG.
Is a magnetic sensor according to another embodiment of the present invention, wherein a) is a type in which the resin portion of the FPC is thick, and b) is a type in which the FPC is drawn out at both ends of the magnetic sensor element. Hereinafter, the same reference numerals are used for the same parts as those in the conventional example for easy understanding.

(Embodiment 1) A magnetic sensor according to an embodiment will be described with reference to FIG. The magnetic sensor element 3 has a magnetoresistive element 5 and a lead wire 10 formed on a glass substrate by using a photolithography technique, a sputtering film forming technique, and the like. A nonmagnetic protective film 6 is added on the upper surface of the magnetoresistive element 5. The lead wire 10 is connected to the magnetoresistive element 5 and the FP
The C joint 8 is electrically connected.

The FPC 11 is disposed so as to cover the magnetic sensor element 3. At substantially the center of the FPC, the FPC 11 and the magnetic sensor 3 are thermocompression-bonded at the joint 8 by soldering and mechanically and electrically connected. The FPC 11 has a magnetic sensor element 3
External terminals 13 are provided via conductors 12 in the opposite direction. A reinforcing resin 14 is applied to reinforce the bonding strength between the magnetic sensor 3 and the FPC 11. The reinforcing resin 14 is made of an epoxy resin and has a temperature of 120.degree.
Heat cured in air for minutes.

The FPC is called a thin type. The FPC is a polyimide resin sheet 25 μm, a bonding adhesive layer 35 μm, a copper circuit layer 35 μm, a bonding adhesive layer 35 μm, and a polyimide resin sheet 25 μm. used. . The resin portion 15 of the FPC is disposed so as to cover the magnetic sensor element 3. However, since there is no copper circuit layer 35 μm, the bonding adhesive layers on both sides, and the polyimide resin sheet on one side, the FPC
Has a thickness of 25 μm. The resin portion 15 of the FPC is not bonded to the magnetic sensor element 3 with a resin or the like, and has a copper circuit layer thickness of 35 μm and a solder thickness of the bonding portion 8 of about 10 μm.
The gap is maintained with a gap of about 45 μm in total with the magnetic sensor element 3.

The width of the resin portion 15 of the FPC is at least one-tenth of the width w of the magnetic sensor element 3 and is protruded on one side.
Is attached. This is to prevent the FPC resin portion 15 from being caught between the magnetic medium and the magnetic sensor. The end of the warped portion 17 was set so as not to protrude from the thickness direction of the magnetic sensor element 3.

In the vicinity of the joining portion 8 of the resin portion 15 of the FPC, a notch 18 from which the polyimide resin is cut is provided. The notch 18 not only facilitates the alignment of the joint 8 but also serves as a relief for the solder that has exuded during the thermocompression bonding of the solder. In this embodiment, the shape is such that all the joints 8 can be covered by one notch. The height dimension of the notch 18 (F
The dimension of the PC in the resin part direction) was 0.4 mm.

FIG. 2 is a perspective view of a magnetic encoder in which the magnetic sensor of the present invention is combined with a magnetic medium. The magnetic poles are magnetized in the outer circumferential direction of the magnetic medium so that N and N and S and S face each other like NSSNNS, and the magnetization pitch λ is 38.
μm. The magnetic medium 1 is fixed to the shaft 9 and rotates with the rotation of the shaft 9. The magnetic sensor 2 and the magnetic medium 1 are arranged so that the thickness of the resin portion 15 of the FPC becomes a gap g and is opposed to each other. At this time, the resin portion 15 of the FPC is also in close contact with the magnetic sensor element.

FIG. 3 shows the close contact portion of the resin portion 15 of the FPC.
This will be described in detail with reference to a sectional view of FIG. Since the magnetic sensor is pressed against the magnetic medium 1 with a pressing force f of 10 g or less, the resin portion 15 of the FPC bends in the vicinity of the notch portion 18 to be in close contact with the magnetic sensor element 3 and the resin portion of the FPC 1
A gap g is formed at a thickness of 5. The exuded portion 19 of the solder generated at the joining portion 8 is trapped in the space of the notch portion 18 and does not protrude to the magnetic medium side of the FPC 11.

By using the FPC 11 having the resin portion 15 of the FPC so as to cover the surface of the magnetic sensor element 3, the thermocompression bonding process between the FPC and the magnetic sensor element can be performed without any change. The gap g as small as 25 μm can be easily regulated.

(Embodiment 2) FIG. 4a) shows an example in which the gap g is increased. The resin portion 15 of the FPC is obtained by combining two layers of a polyimide resin sheet 25 μm and an adhesive layer 35 μm, and has a total of 120 μm. It goes without saying that the gap g can be easily changed by using a polyimide resin sheet and an FPC in which the thickness of the adhesive layer is changed.

(Embodiment 3) As shown in FIG. 4b), as a measure for reducing the size of the magnetic sensor element 3, a magnetic sensor element 3 having terminals at two positions on both ends, and a terminal corresponding to the terminal and a solder escape Flexible cable 1 with cutout
2 and the two terminals to which solder has been applied are thermocompression bonded. By wiring so as to have terminals at both ends of the magnetic sensor element 3, the width of the terminal portion can be suppressed from increasing, and the element size can be reduced. This is particularly effective when the area occupied by the terminals in the magnetic sensor element 3 is large.

By using the structure of the present invention, a magnetic sensor corresponding to a magnetic recording medium having a very small pitch can be obtained.
When the pitch λ of the magnetic recording medium is extremely small, the gap between the magnetic drum and the magnetic sensor is kept to some extent small and constant in order to accurately read a magnetic signal that changes at a period of λ and improve detection accuracy. There is a need. As shown by an example of the output characteristic of the magnetic sensor in FIG. 5, when the magnetic sensor having the configuration of the present invention is used, the magnetic sensor can be used stably even in the range of a very small gap having a large sensor output = 10 to 20 μm. In the conventional magnetic sensor, in addition to reducing the gap itself, it was difficult to suppress an output change due to a gap length error or a displacement during assembly. On the other hand, the magnetic sensor using the configuration of the present invention can handle a gap of 25 μm or less, and can obtain a stable sensor output voltage.

[0037]

According to the configuration of the present invention, when assembling the magnetic encoder, the gap can be adjusted without performing the gap adjustment.
A magnetic sensor can be used in contact. Such a magnetic encoder has good detection accuracy, has a simple assembling process, is suitable for mass production, and is inexpensive.

[Brief description of the drawings]

FIG. 1 is an external view of a magnetic sensor according to an embodiment of the present invention.

FIG. 2 is a perspective view of a magnetic encoder using the magnetic sensor of the present invention.

FIG. 3 is a sectional view of a magnetic encoder using the magnetic sensor of the present invention.

FIG. 4 is a sectional view of a magnetic sensor according to another embodiment of the present invention.

FIG. 5 is a diagram illustrating a relationship between a gap g and a magnetic sensor output voltage.

FIG. 6 is a perspective view of a conventional magnetic encoder.

FIG. 7 is a sectional view of a conventional magnetic encoder.

FIG. 8 is a diagram showing gap adjustment of a conventional magnetic encoder.

[Explanation of symbols]

1 magnetic medium, 2 magnetic sensors, 3 magnetic sensor elements,
4, 11 FPC, 5 magnetoresistive element, 6 non-magnetic film, 7 resin sheet, 8 thermocompression bonding section, 9 axes, 10
Lead wire, 12 conductor, 13 external terminal, 14
Reinforcement resin, 15 FPC resin part, 16 gap, 17
Warp, 18 Notch, 19 Solder bleed

Claims (8)

[Claims] 1. A magnetic device, which is disposed so as to face a magnetic recording medium having a predetermined magnetic pattern alternately magnetized in a reverse direction at a constant pitch λ with an interval, and detects the magnetic pattern as a change in electric resistance. A magnetic sensor having a resistance effect element, wherein a resin portion of a flexible printed circuit covers at least a part of the sensor portion. 2. The magnetic sensor according to claim 1, wherein the thickness of the resin portion of the flexible printed circuit is equal to the gap between the magnetic sensor and the magnetic recording medium. 3. The magnetic sensor according to claim 1, wherein the thickness of the resin portion of the flexible printed circuit is in a range of 0.2 to 1λ with respect to the magnetization pitch λ. 4. The flexible printed circuit according to claim 1, wherein the resin portion and the magnetic sensor are not fixed.
Alternatively, the magnetic sensor according to claim 2. 5. The resin part of the flexible printed circuit,
The magnetic sensor according to claim 1, wherein the magnetic sensor protrudes from an end of the magnetic sensor by at least w / 10 of a width w of the magnetic sensor. 6. The resin part of the flexible printed circuit,
The magnetic sensor according to claim 1, wherein a portion protruding from an end of the magnetic sensor is curved with a curved surface toward the magnetic sensor. 7. The magnetic sensor according to claim 1, wherein an overflow of solder generated at the time of welding between the magnetic sensor and the flexible printed circuit is escaped to a notch provided in the flexible printed circuit. . 8. A structure in which the thickness of the resin portion of the flexible printed circuit is set as a gap between the magnetic sensor and the magnetic medium, and the resin portion of the flexible printed circuit is deformed and brought into close contact with the magnetic recording medium, so that they are slid. A magnetic encoder using the magnetic sensor according to claim 1.