JP2002005760A - Magnetic core for noncontact type displacement sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic core for a noncontact type displacement sensor using an inexpensive prescribed green compact having a relatively high specific resistance value as the skeleton of a coil housing material forming the magnetic core and effectively improving the mechanical characteristic causing a problem when using the green compact. SOLUTION: This magnetic core is provided with a detecting coil 2 detecting the relative displacement quantity of a first detecting ring 8, against a second detecting ring 8, displaced according to the displacement quantity of a torsion bar 7 when torque is applied to an input shaft 5 in no contact as an inductance change a coil housing member 3 having a space storing the detecting coil 2 and forming a closed space together with the stored detecting coil, and a lead wire 4 connected to the detecting coil 2. The coil housing member 3 is formed with the green compact 10 of insulation-covered soft magnetic powder and an insulating layer 11 covering the outer face, and an organic resin 12 is filled in the closed space of the coil housing member 3 storing the detecting coil 2 to reliably fix the detecting coil 2 in the coil housing member 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic core for a non-contact type displacement sensor, and more specifically, as a skeleton of a coil housing member constituting a magnetic core, which has a relatively high specific resistance value and is inexpensive. In addition to using a soft magnetic powder compact with insulation coating, a so-called compact core, and effectively improving the mechanical characteristics that have become a problem when using the compact, especially for electric power steering devices for automobiles The present invention relates to a magnetic core for a non-contact torque sensor suitable for use.

[0002]

2. Description of the Related Art A power steering device is a device for assisting a steering force of an automobile. In the past, a hydraulic type was mainly used. Power steering systems have been widely developed.

The electric power steering apparatus has better controllability, simplification of mechanical parts, better fuel efficiency, and power supply to the electric motor only when necessary, as compared to the hydraulic power steering apparatus. It has various advantages such as:

[0004] The electric power steering system includes:
The direction and the amount of force when the steering wheel (steering wheel) is operated are detected by a torque sensor, and the current of an electric motor that assists the steering force is controlled by a control unit.

FIG. 7 shows an essential part of a typical non-contact type torque sensor constituting an electric power steering apparatus.

The torque sensor 101 includes an input shaft 102 connected to a steering wheel (not shown), an output shaft 103 connected to the steered wheels, a torsion bar 104 connecting these shafts 102 and 103, First and second detection rings 105 and 106 disposed on the outer peripheral side of the torsion bar 104 on the input shaft 102 side and the output shaft 103 side, respectively;
02 has a detection coil 107 that detects the relative displacement of the first detection ring 105, which is displaced in accordance with the displacement of the torsion bar 104 when a torque is applied to the second detection ring 106, as a change in inductance in a non-contact manner. It is mainly constituted by the magnetic core 108.

The magnetic core 108 has a detection coil 107 wound around a coil bobbin and a space for accommodating the detection coil 107.
And the detection coil 107 is connected to a detection ring 105, 1
A donut-shaped coil housing member 109 which is held at a position spaced apart from the outer peripheral surface of the coil 06 at a constant interval, a lead wire 110 having one end connected to the detection coil 107 and the other end led out of the coil housing member 109; It is mainly constituted by

As shown in FIG. 8, a conventional magnetic core 108 includes a coil housing member 109, a coil housing case 111 for housing the detection coil 107, and a lid press-fitted into an opening of the case 111.
The material of the coil storage case 111 and the lid 112 is a soft magnetic sintered material obtained by compression molding into a green compact with an electromagnetic stainless steel-based or iron-based soft magnetic powder and then further sintering. The detection coil 107 is generally fixed to the inner surface of the coil housing member 109 with an adhesive 113.

However, since the soft magnetic sintered material has a low specific resistance value and a low detection sensitivity as compared with those of ferrite or sendust alloy, if the frequency of the drive power supply is set high to improve the detection sensitivity, eddy current As a result of increased loss and reduced inductance,
The detection sensitivity deteriorates, and it is difficult to perform highly accurate detection.

[0010] On the other hand, ferrite and sendust alloy have excellent magnetic properties and can be detected with high accuracy, but are expensive, so that application to the coil housing member 109 is not preferable in terms of cost. . In addition, ferrite also has a disadvantage that inductance has a large temperature change.

Further, as a coil housing member having a relatively high specific resistance value and being inexpensive, there is known a coil housing member formed of a soft magnetic powder compact having insulation coating.

[0012] It is known that the coil accommodating member made of such a green compact has a high detection sensitivity because of a small eddy current loss when a high-frequency current is applied. It is difficult to manufacture with a conventional press-fitting structure because it is weak and may be easily broken especially when subjected to an impact, and its application is also limited. It was said to be difficult.

In addition, the conventional magnetic core (FIG. 8) merely fixes the detection coil 107, more specifically, the coil bobbin 114 around which the detection coil is wound, to the inner surface of the coil housing member 109 with an adhesive. Coil storage member 1 of coil bobbin 114
It is also assumed that the fixation on the inner surface of 09 will be insufficient,
In this case, a strong impact force is applied to the coil housing member 109 by the coil bobbin 114, and it is assumed that the coil housing member 109 may be damaged.

Further, the closed space S formed in the coil housing member 109 housing the detection coil 107 is not filled with anything and only the space exists.
May be disturbed, which may have a significant effect on magnetic properties.

Therefore, when the coil housing member is made of the above-mentioned green compact, measures are taken to securely fix the detection coil 107 to the coil housing member 109 and to maintain the winding state of the detection coil. It was necessary.

A general displacement sensor is disposed in contact with a housing made of aluminum alloy or the like in order to avoid the influence of external electromagnetic waves, but a coil housing member whose outer surface is not insulated is provided in the housing. When inscribed, there is a problem that an eddy current is generated in the housing and the sensitivity of the detection coil is reduced.In addition, when the housing is made of an aluminum alloy, a difference in the coefficient of thermal expansion with the coil housing member causes a problem. In particular, when the housing is significantly thermally shrunk at a low temperature, a phenomenon that the coil accommodating member is apt to be apt to occur is apt to occur, and this phenomenon sometimes distorts the magnetic core and causes a shift in inductance characteristics.

[0017]

SUMMARY OF THE INVENTION An object of the present invention is to provide, as a skeleton of a coil accommodating member constituting a magnetic core, a compact made of insulated soft magnetic powder having a relatively high specific resistance value and a low cost. It is an object of the present invention to provide a magnetic core for a non-contact type torque sensor, which effectively improves mechanical properties which have been a problem when using a compact, and is particularly suitable for use in an electric power steering device for automobiles. .

[0018]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides first and second shafts on an input shaft side and an output shaft side of an outer peripheral side of a torsion bar in which an input shaft and an output shaft are coaxially connected. The second detection ring is arranged oppositely, and the relative displacement between the first detection ring and the second detection ring, which is displaced in accordance with the displacement of the torsion bar when a torque is applied to the input shaft, is determined as a change in inductance. And has a space for accommodating the detection coil and the detection coil,
A donut-shaped coil housing member that forms a closed space together with the stored detection coil and holds the detection coil at a position spaced apart from the outer peripheral surface of the detection ring at a fixed interval, one end of which is connected to the detection coil; In the magnetic core for a non-contact type displacement sensor having a lead wire led out of the coil housing member, the coil housing member is a green compact obtained by compression-molding an insulating-coated soft magnetic powder into a predetermined shape. And an insulating layer covering the outer surface of the green compact, and the organic resin is filled in the closed space of the coil housing member housing the detection coil, and the detection coil is securely inserted in the coil housing member. A magnetic core for a non-contact type displacement sensor characterized by being fixed.

The coil housing member has at least one through hole for filling the closed space with the organic resin, and / or has openings at both ends, and stores the detection coil from the upper end opening. It is preferable to have a coil housing case capable of mounting the detection coil on the lower end opening and a lid forming the closed space by being attached to the upper end opening of the coil housing case housing the detection coil.

Further, it is more preferable that the lid is tightly attached to the opening of the coil storage case by press fitting.

In addition, it is more preferable that both the constituent material of the insulating layer and the organic resin filling the closed space are thermoplastic resins or thermosetting resins.

[0022]

Next, an example of an embodiment of the present invention will be described in detail with reference to the drawings. Fig. 1 (a) ~
(c) is a typical view of a magnetic core for a non-contact type displacement sensor according to the present invention, wherein (a) is a plan view, (b) is a cross-sectional view, and (c) is a bottom view. FIG. Also, FIG.
1 shows an example in which the magnetic core shown in FIGS. 1A to 1C is incorporated in an electric power steering apparatus for a vehicle.

The magnetic core 1 shown in FIG. 1 includes a detection coil 2 wound around a coil bobbin 17, a coil housing member 3 for housing the coil, and a lead wire 4 extending from the detection coil 2 to the outside of the coil housing member 3. It is mainly composed of

As shown in FIG. 2, the detection coil 2 is provided on the input shaft 5 side and the output shaft 6 side of the outer periphery of the torsion bar 7 connecting the input shaft 5 and the output shaft 6 coaxially. The relative displacement of the first detection ring 8 with respect to the second detection ring 9 which is displaced in accordance with the displacement of the torsion bar 7 when the torque is applied to the input shaft 5 by disposing the second detection rings 8 and 9 facing each other. In a non-contact manner as a change in inductance.

The coil accommodating member 3 has a space for accommodating the detection coil 2, forms a closed space S together with the accommodated detection coil 2, and disposes the detection coil 2 at regular intervals from the outer peripheral surfaces of the detection rings 8 and 9. It is for holding at a separated position.

The lead wire 4 is for passing a high-frequency current from an external power supply (not shown) to the detection coil 2. One end of the lead wire 4 is connected to the detection coil 2, and the other end is connected to the outside of the coil housing member 3. And connect it to an external power supply.

FIGS. 6 (a) to 6 (c) are exploded perspective views for explaining the structure of a typical magnetic core of the present invention, and FIG.
FIG. 6B shows the detection coil 2 wound around the coil bobbin, and FIG. 7C shows the coil storage case 15.

The main features of the structure of the present invention are that, as a skeleton of the coil housing member 3 constituting the magnetic core 1, a predetermined compact 10 having a relatively high specific resistance value and a low cost is used, and a detection coil is provided. And filling the closed space of the coil accommodating member 3 with the organic resin. More specifically, the coil accommodating member 3 is formed by compression molding an insulating-coated soft magnetic powder into a predetermined shape. And a coil housing member 3 comprising the green compact 10 obtained by the above method and an insulating layer 11 covering the outer surface of the green compact 10 and housing the detection coil 2.
Is filled with the organic resin 12 in the closed space of the coil housing member 3.
To reliably fix the detection coil 2 therein.

By employing the above configuration, even when a high-frequency current is applied to the detection coil 2, the eddy current loss is small and the detection sensitivity is increased.
Since the strength of the entire magnetic core is also greatly improved, even if a shock is applied to the magnetic core, the core is less likely to be damaged,
Moreover, it can be manufactured at low cost, and as a result, the magnetic core of the present invention has sufficient performance as a magnetic core for a non-contact type displacement sensor. It is possible to do.

The green compact 10 is obtained by compression-molding a soft magnetic powder coated with insulation into a predetermined shape.
As the insulating-coated soft magnetic powder, for example, it is preferable to use a mixed powder in which 1% by mass or less of an organic binder is mixed with a phosphate treatment or an inorganic coating treatment iron powder. It is preferable to carry out under the condition that the density of the molded body is 7.2 g / cm ³ or more. Further, in order to improve the characteristics of the magnetic core, it is more preferable to further heat to a temperature of 500 ° C. or less after the compression molding.

The insulating layer 11 protects the green compact 10 from the outer surface side, prevents the generation of eddy current when placed in contact with the housing, and protects the compact at low temperatures when the housing is made of an aluminum alloy. It has the effect of alleviating biting into the magnetic core of the housing. In addition, since the conduction with the housing is interrupted, a stable response can be obtained without being affected by a potential change from the vehicle body.

The constituent material of the insulating layer 11 is preferably a thermosetting resin such as polyphenylene sulfide containing glass fiber, a thermoplastic resin such as polyester or polyamide, or a phenol resin containing glass fiber.

The thickness of the insulating layer 11 is preferably 0.3 mm or more. If the thickness is less than 0.3 mm, the green compact cannot be sufficiently protected.

The insulating layer 11 is preferably formed by insert molding.

As the organic resin 12 to be filled in the closed space of the coil housing member 3, a material different from the constituent material of the insulating layer 11 may be used, but it is preferable to use the same material.
In this case, the formation of the insulating layer 11 and the filling of the organic resin 12 into the closed space are preferably performed by an insert molding method that can perform these operations simultaneously.

At least one coil housing member 3 (one in FIG. 1) is used to fill the closed space with an organic resin.
It is preferable to have a through hole 13 in particular, especially when it is necessary to quickly fill the closed space with an organic resin, FIG.
As shown in FIG. 6 (c), a total of four through-holes 13 may be provided at four equal positions (0 °, 90 °, 180 °, and 270 ° positions) on the outer peripheral surface of the coil housing member. More preferred.

As shown in FIG. 6 (c), the coil housing member 3 has openings 14a and 14b at both ends, can store the detection coil 2 from the upper end opening 14a, and mounts the detection coil 2 on the lower end opening 14b. Preferably, the coil housing case 15 includes a cover 16 that forms the closed space S by being attached to the upper end opening 14a of the coil housing case 15 that houses the detection coil 2. In this case, the through hole 13 May be provided on at least one of the coil storage case 15 and the lid 16.

It is important that the lid 16 is tightly attached to the opening of the coil housing case 15 by press-fitting in order to enhance the sensitivity of the coil, and is preferable from the viewpoint of securing the strength of the entire magnetic core.

As another embodiment, as shown in FIG. 3, two compacts 10a, 10b containing the detection coil 2 are provided.
Are set so that the lids 16a and 16b are overlapped with each other, and the entire outer surfaces thereof are simultaneously covered with the insulating layer 11 by insert molding, and the organic resin 12 is placed in the closed spaces in these compacts 10a and 10b, respectively. May be filled at the same time, whereby the productivity can be improved.

As shown in FIG. 4, two compacts 10
The openings of a and 10b can be closed by sharing one lid 16, thereby reducing the product cost of the magnetic core and further improving the productivity.

The above is merely an example of the embodiment of the present invention, and various changes can be made within the scope of the claims. For example, when it is necessary to position the coil housing member 3 in the housing, as shown in FIG. 5, three or more projections 18 are provided on the outer peripheral surface of the coil housing member 3 so as to correspond to these projections 18. Thus, it can be configured to fit into a concave portion (not shown) provided on the inner peripheral surface of the housing.

[0042]

According to the present invention, the eddy current loss when a high-frequency current is applied is small and high inductance characteristics are obtained by using a soft magnetic powder compact having insulation coating as the skeleton of the coil housing member. In addition, the detection sensitivity can be effectively improved. Further, by filling the closed space of the coil housing member housing the detection coil with the organic resin, the detection coil can be securely fixed and the strength as the magnetic core can be remarkably increased.

Further, by covering the outer surface of the green compact with an insulating layer, eddy current loss which is likely to occur when the magnetic core is inscribed in the housing can be suppressed. In addition, when the housing is made of an aluminum alloy, In addition, because the insulating layer reduces the tendency of the housing to stick to the magnetic core, which tends to occur at low temperatures, the magnetic core is less likely to be distorted, and stable inductance characteristics can be obtained.

[Brief description of the drawings]

1 shows a magnetic core for a non-contact type displacement sensor according to the present invention, wherein (a) is a plan view, (b) is a sectional view, and (c).
Is a bottom view.

FIG. 2 is a partial cross-sectional view when the magnetic core shown in FIG. 1 is attached to an electric power steering device for a vehicle.

FIG. 3 is a cross-sectional view showing another embodiment of the present invention.

FIG. 4 is a cross-sectional view showing another embodiment of the present invention.

FIG. 5 is a plan view showing another coil housing member 3 constituting the magnetic core of the present invention.

FIGS. 6 (a) to 6 (c) are exploded perspective views of members mainly constituting another magnetic core of the present invention, and FIG. 6 (d) is a sectional view of a magnetic core manufactured using these members.

FIG. 7 is a perspective view showing a main part of a conventional non-contact type torque sensor.

FIG. 8 is a sectional view showing a conventional magnetic core.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 magnetic core for non-contact displacement sensor 2 detection coil 3 coil housing member 4 lead wire 5 input shaft 6 output shaft 7 torsion bar 8 first detection ring 9 second detection ring 10 compact 11 insulating layer 12 organic resin 13 through hole 14 Opening 15 Coil storage case 16 Lid 17 Coil bobbin 18 Convex part

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masayuki Yamamoto 2- 30-11 Minami-Ikebukuro, Toshima-ku, Tokyo Inside Tokyo Sintered Metal Co., Ltd. (72) Inventor Masayuki Sugiyama 2--30, Minami-Ikebukuro, Toshima-ku, Tokyo No. 11 Tokyo Sintered Metal Co., Ltd. (72) Inventor Hidesatoshi Tsuchiya 2-30-11 Minami Ikebukuro, Toshima-ku, Tokyo Tokyo 72 Co., Ltd. 3-5-8, Minamisenba Koyo Seiko Co., Ltd. (72) Inventor: Shunsuke Nakaura 3-5-8, Minamisenba, Chuo-ku, Osaka-shi, Osaka Prefecture Kochi Seiko Co., Ltd. (72) Inventor: Norio Nakatani, Osaka, Osaka 3-5-8 Minamisenba, Ward Koyo Seiko Co., Ltd. (72) Inventor Takahiro Sanada 3-5-8 Minamisenba, Chuo-ku, Osaka-shi, Osaka Inside Koyo Seiko Co., Ltd. (72) Nagano Inventor Shin Osaka, Chuo-ku, Osaka-shi Minamisenba 3-chome No. 5 No. 8 Koyo Seiko Co., Ltd. in the F-term (reference) 2F051 AA01 AB05 BA03 2F063 AA02 AA34 BA30 BC04 CA40 DA01 DB01 DB07 DD03 GA04 GA29 GA33 GA50 GA61 ZA01 3D033 CA28

Claims (5)

[Claims] An input shaft and an output shaft are coaxially connected to each other, and a first and a second detection ring are arranged on an input shaft side and an output shaft side of an outer peripheral side of the torsion bar, and torque is applied to the input shaft. A detection coil that detects the relative displacement of the first detection ring relative to the second detection ring, which is displaced in accordance with the displacement of the torsion bar when actuated, as a change in inductance, and a space for accommodating the detection coil. A donut-shaped coil housing member that forms a closed space together with the stored detection coil and holds the detection coil at a position separated from the outer peripheral surface of the detection ring at a constant interval, and one end is connected to the detection coil, A magnetic core for a non-contact type displacement sensor having a lead wire whose other end is led out of a coil housing member, wherein the coil housing member is formed of a soft magnetic powder coated with an insulating material in a predetermined shape. A green compact obtained by compression molding,
An organic resin is filled in the closed space of the coil housing member, which is constituted by an insulating layer that covers the outer surface of the green compact and houses the detection coil, and the detection coil is securely fixed in the coil housing member. A magnetic core for a non-contact displacement sensor. 2. The magnetic core for a non-contact displacement sensor according to claim 1, wherein the coil housing member has at least one through hole for filling the closed space with an organic resin. 3. A coil storage case having an opening at both ends, a detection coil can be stored from an upper end opening, and a detection coil can be mounted on a lower end opening, and a coil storage case storing the detection coil. 3. The magnetic core for a non-contact displacement sensor according to claim 1, further comprising: a lid that forms the closed space by being attached to an upper end opening of the magnetic sensor. 4. The magnetic core for a non-contact displacement sensor according to claim 3, wherein the lid is tightly attached to an upper end opening of the coil storage case by press-fitting. 5. The non-contact material according to claim 1, wherein the constituent material of the insulating layer and the organic resin filling the closed space are each a thermoplastic resin or a thermosetting resin. Magnetic core for displacement sensors.