JP2005249695A - Torque sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a torque sensor capable of restraining, to the minimum, reduction of a magnetic flux caused by formation of a cut-out provided in a yoke of a coil unit. <P>SOLUTION: In this torque sensor provided with a rotary shaft connected by a torsion bar, a cylindrical coil unit provided to surround the rotary shaft, and an impedance variable means for varying an impedance of the coil unit in response to variation of a torque acting on the rotary shaft, and for detecting the torque generated in the rotary shaft, based on the impedance variation by the impedance variable means, the coil unit is constituted of a bobbin constituted of a wound part wound with a coil, and a terminal part for extracting the coil to an outside, and the yoke stored inside the bobbin and formed with the cut-out for the terminal extraction for the bobbin, and a protrusion projected toward an axis-directional end face side of the terminal in the circumferential-directional central part of the cut-out, and coil escape grooves formed in circumferential-directional both sides of the protrusion are formed in the cut-out in the yoke. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a torque sensor that detects a relative rotational displacement (torque) of an input shaft and an output shaft in an electric power steering apparatus.

Conventionally, as a torque sensor, for example, a technique described in Patent Document 1 has been disclosed. In this publication, a rectangular cutout for a terminal lead-out direction is provided in a yoke that houses a bobbin around which a coil (wiring) of a coil unit of a torque sensor is wound. The coil (wiring thereof) is drawn out from between the notch and the terminal.
JP 2002-156297 A (see FIG. 2).

  Most of the magnetic field formed around the notch flows so as to bypass the notch, but part of the magnetic field is formed so as to jump over the notch. Therefore, in order to reduce the drop of the magnetic field from the non-notch forming portion and form a strong magnetic field, it is desirable that the axial length of the notch is short. However, since a predetermined gap is provided between the notch and the terminal in order to prevent the coil (wiring) from being sandwiched between the notch and the terminal, the axial length of the notch is the axis of the terminal. In addition to the thickness in the direction, there is a problem that the predetermined gap is increased.

  The present invention has been made paying attention to the above problem, and an object thereof is to provide a torque sensor capable of minimizing a decrease in magnetic flux due to formation of a notch provided in a yoke of a coil unit.

  To achieve the above object, according to the present invention, a rotating shaft connected by a torsion bar, a cylindrical coil unit provided so as to surround the rotating shaft, and a coil according to a change in torque acting on the rotating shaft. In the torque sensor for detecting the torque generated on the rotating shaft based on the impedance change by the impedance variable means, the coil unit includes a winding portion around which the coil is wound. And a yoke that is housed inside the bobbin and is provided with a notch for pulling out the terminal portion of the bobbin. At the center in the circumferential direction of the terminal and projecting toward the end face side in the axial direction of the terminal A coil relief groove which is has the be formed.

  That is, since the axial length of the notch in the protruding portion is shorter than the axial length of the notch in the coil escape groove, the magnetic field in the protruding portion can be increased. For this reason, it is possible to reduce the drop of the magnetic field with respect to the non-notch forming portion, and it is possible to minimize the decrease in magnetic flux due to the formation of the notch provided in the yoke of the coil unit.

  Hereinafter, the best mode for realizing the torque sensor of the present invention will be described based on Example 1 shown in the drawings.

  FIG. 1 is a configuration diagram of a torque sensor applied to the power steering apparatus according to the first embodiment. The torque sensor according to the first embodiment is connected to a steering wheel (not shown) operated by the driver, and includes an input shaft 1 (corresponding to a rotating shaft in claims) formed from a magnetic material such as iron, It is provided between an output shaft 2 (corresponding to a rotating shaft in claims) connected to a rack and pinion mechanism. The input shaft 1 and the output shaft 2 are connected via fixed portions 3 a and 3 b of the torsion bar 3. The torque sensor includes a torsion bar 3, two cylindrical members 4 and 5, and coil units 9A and 9B including coils 9a and 9b.

  On the input shaft 1 side end surface of the output shaft 2, a groove 2 a extending further in the radial direction from the insertion portion of the torsion bar 3 is formed. The groove 2 a is formed on the output shaft 2 side end surface of the input shaft 1. The projected portion 1a is slidably inserted. However, the width (circumferential dimension) of the groove 2a is slightly wider than the width of the convex portion 1a, and prevents relative rotation beyond a predetermined range between the input shaft 1 and the output shaft 2.

  The cylindrical member 4 is tightly fixed to the input shaft 1 so as to surround the large diameter portion 1A. The cylindrical member 4 is made of a conductive and nonmagnetic material (aluminum material in this embodiment), and a plurality of first windows 4a are provided in the circumferential direction.

  The cylindrical member 5 is closely fixed to the output shaft 2 so as to cover the cylindrical member 4 at the small diameter portion 5A. The cylindrical member 5 is made of a conductive and nonmagnetic material (aluminum material in this embodiment), and a plurality of second windows 5a and 5b are provided in the circumferential direction.

  The two sets of coil units 9A and 9B are arranged side by side in the axial direction so as to surround the outer periphery of the cylindrical members 4 and 5. The coils 9a, 9b, the first window 4a, and the second windows 5a, 5b are arranged so as to face each other in the radial direction.

  The driver's steering force is transmitted from the input shaft 1, the torsion bar 3, and the output shaft 2 to the rack and pinion mechanism (not shown) and to the steered wheels (not shown). When the driver performs a steering operation, the degree of overlap between the window of the cylindrical member 4 and the window of the cylindrical member 5 changes as the torsion bar 3 fixed between the input and output shafts twists. At this time, impedance changes occur in the coils 9a and 9b (corresponding to the impedance variable means in the claims). When the generated impedance change is transmitted to the board (not shown), the steering torque is calculated in the board. A drive current that generates a steering assist torque that reduces the steering torque based on the calculation result is supplied to an electric motor (not shown), and a steering assist torque having an arbitrary direction and magnitude is applied.

2 is a cross-sectional view of the coil unit 9A (9B) of the torque sensor according to the first embodiment, taken along line AA. FIG. 3 is a front view of the coil unit 9A (9B) of the torque sensor as viewed from the axial second yoke member 14 side. FIG. 4 is a side view of the coil unit 9A (9B) of the torque sensor as viewed from the radial terminal side.
The coil unit 9A (9B) includes a resin bobbin 11 in which a wire 12 such as a copper wire is wound to form a coil 9a (9b), and a yoke as a bobbin housing that covers the side surface and outer periphery of the bobbin 11 9C (9D). The yoke 9C (9D) includes a first yoke member 10 and a second yoke member 14. Here, the first yoke member 10 is a member composed of a cylindrical portion 15, a bottom portion 16, a bent portion 17, and an opening portion 16 a, and the second yoke member 14 is the other in the axial direction of the cylindrical portion 15 of the first yoke member 10. It is a disk-shaped member that closes the side. Details of the first yoke member 10 will be described with reference to FIGS. Details of the bobbin 11 will be described with reference to FIGS. Further, the notch 21 in FIG. 4 will be described with reference to FIG.

5 is a cross-sectional view of the first yoke member 10 in the AA direction according to the first embodiment, and FIG. 6 is a front view of the first yoke member 10 according to the first embodiment as viewed from the axial cutout 21 side.
The first yoke member 10 includes a cylindrical portion 15, a bottom portion 16 that closes one axial direction of the cylindrical portion 15, an opening portion 16 a provided in the bottom portion 16, and a bent portion that connects the cylindrical portion 15 and the bottom portion 16. 17. Further, a cutout 21 is provided in a part of the cylindrical portion 15, and the terminal portion 11 a of the bobbin 11 is drawn out from the cutout 21.

[Notch shape]
Next, the notch 21 provided in the first yoke member 10 of the yoke 9C (9D) will be described. FIG. 7 is a diagram illustrating the notch 21 of the first yoke member 10 according to the first embodiment. The notch 21 is divided into first tapered regions 18 a and 18 b and abutment region 19. The abutting region 19 is provided with a protruding portion 19a, and the coil escape groove 21a is formed in a tapered shape so that the axial length of the notch 21 gradually increases from the protruding portion 19a toward both ends in the circumferential direction. Is provided.

  FIG. 8 is a cross-sectional view in the AA direction of the bobbin 11 in the first embodiment. FIG. 9 is a view of the bobbin 11 in the first embodiment when viewed from the installation surface side of the second yoke member 14 in the axial direction.

  The bobbin 11 includes a winding part 11a around which the wiring 12 is wound to form a coil 9a (9b), and a bobbin terminal part 11b that leads the wiring 12 to the outside (corresponding to a terminal part described in claims), The wiring winding portion 11c is configured to wind the drawn wiring 12. The bobbin terminal portion 11b is connected to the terminal 13.

  Here, the wiring 12 drawn out to the outside in the bobbin terminal portion 11b is covered with enamel and wound around the wiring winding portion 11c. Further, the bobbin terminal portion 11b is made of resin, and is configured to prevent a short circuit even if the enamel of the wiring 12 is peeled off.

[Effect of notch when bobbin is attached to the yoke]
10 is an enlarged view showing the vicinity of the notch 21 of the coil unit 9A (9B) (the region represented by B in FIG. 4) in the first embodiment.
The protrusion 19a of the notch 21 contacts the bobbin terminal abutting surface 11e, and the wiring 12 of the coil 9a (9b) is drawn out from the coil escape groove 21a provided in the first taper regions 18a and 18b.

  In the protrusion 19a, the axial length of the notch 21 is shorter than the axial length of the notch 21 in the coil escape groove 21a.

  The protruding portion 19a is in contact with the bobbin terminal portion abutting surface 11e, and is configured to suppress the vertical movement of the terminal 13 in the axial direction. Moreover, since the coil escape groove 21a is formed in a tapered shape in which the axial length of the cutout 21 gradually increases toward both ends in the circumferential direction, the change in the axial length of the cutout 21 becomes gentle.

The effects obtained by dividing the notch 21 into two regions of the first tapered regions 18a and 18b and the abutting region 19 will be listed below.
1) In the first taper regions 18a and 18b, a coil escape groove 21a is provided, and contact of the wiring of the coil 9a (9b) between the notch 21 and the terminal 13 can be avoided. That is, there is no possibility of damaging the wiring 12 (corresponding to claim 1).
2) Since the axial length of the cutout 21 is shorter than the axial length of the cutout 21 in the coil escape groove 21a in the protruding portion 19a, the magnetic field in the cutout 21 can be strengthened in the protruding portion 19a. Thereby, the drop of the magnetic field with the non-notch forming part can be reduced (corresponding to claim 1).
3) The protruding portion 19a is in contact with the bobbin terminal portion abutting surface 11e, and the vertical movement of the terminal 13 in the axial direction can be suppressed. Therefore, it is possible to prevent the terminal 13 from being tilted in the axial direction, and to prevent the wiring 12 from being disconnected.
4) Since the coil escape groove 21a is formed in a tapered shape in which the axial length of the cutout 21 gradually increases toward both ends in the circumferential direction, the change in the axial length of the cutout 21 becomes gentle. Thereby, the big change of the impedance in the notch 21 vicinity can be suppressed.

  Next, Example 2 will be described with reference to FIG. Since the basic configuration of the torque sensor is the same as that of the first embodiment, only different points will be described.

FIG. 11 is an enlarged view showing the vicinity of the notch 22 of the coil unit 9A (9B) (region represented by B in FIG. 4) in the second embodiment.
The notch 22 is divided into the abutting region 19, the second tapered regions 20a and 20b, and the third tapered regions 23a and 23b, and expands toward the bobbin insertion port 11d ′. At this time, the circumferential width of the bobbin insertion port 11d ′ is formed longer than that of the first embodiment as compared with the notch 21 of the first embodiment, and the circumferential width of the coil escape groove 22a portion is the coil of the first embodiment. It is formed shorter than the escape groove 21a.

  Next, the operation of the second embodiment will be described. The notch 22 is divided into the abutment region 19, the second taper regions 20a and 20b, and the third taper regions 23a and 23b, whereby the circumferential width of the bobbin insertion port 11d ′ is increased, so that the insertability of the bobbin 11 is increased. And the ease of assembly can be ensured.

  Further, the circumferential width of the notch 22 affects the formation of the magnetic field, and particularly affects the vicinity of the coil 9a (9b). At this time, since the circumferential width of the coil escape groove 22a is formed short, a decrease in magnetic flux due to the formation of the notch 22 can be minimized. That is, it is possible to simultaneously achieve two effects of improving the insertability of the bobbin 11 and suppressing the decrease in magnetic flux due to the notch 22.

  Further, technical ideas other than the claims that can be grasped from the respective embodiments will be described below together with the effects thereof.

(A) In the torque sensor according to claim 1,
The protrusion is in contact with an axial end surface of the terminal.

  The protruding portion 19a is in contact with the bobbin terminal portion abutting surface 11e, and the vertical movement of the terminal 13 in the axial direction can be suppressed. Therefore, it is possible to prevent the terminal 13 from being tilted in the axial direction, and to prevent the wiring 12 from being disconnected.

(B) In the torque sensor according to claim 1 or (A),
The torque sensor, wherein the coil escape groove is formed in a taper shape so that an axial length of the notch gradually increases from the protrusion toward both ends in the circumferential direction.

  Since the change in the axial length of the notch becomes gentle, the impedance change around the notch can be suppressed.

(C) In the torque sensor according to claim 1 or (a) or (b) above,
The yoke includes a first yoke member having a cylindrical portion and a bottom portion that closes one axial direction side of the cylindrical portion;
A disc-shaped second yoke member that closes the other axial side of the cylindrical portion;
The notch is formed at an end portion on the other axial side of the cylindrical portion, and a circumferential width of the notch is formed in a tapered shape whose diameter increases from one side in the axial direction to the other side. Torque sensor.

  When the cutout 22 is formed in the cylindrical portion 15, the cutout 22 is formed so as to expand in a tapered shape from the bottom portion 16 to the second yoke member 14 side. That is, the insertability of the bobbin 11 is improved by increasing the circumferential width of the bobbin insertion port 11d '. Further, the place where the size of the circumferential width of the notch 22 has the greatest influence is in the vicinity of the coil 9a (9b), but since the circumferential width of the coil escape groove 22a is short, the decrease in magnetic flux due to the formation of the notch 22 is minimized. Can be suppressed.

It is a torque sensor block diagram in Example 1. FIG. It is AA sectional drawing of the coil unit of the torque sensor in Example 1. FIG. It is the front view which looked at the coil unit of the torque sensor in Example 1 from the axial second unit member side. FIG. 3 is a side view of the coil unit of the torque sensor according to the first embodiment when viewed from the radial terminal side. FIG. 6 is a cross-sectional view of the first yoke member in Example 1 in the AA direction. It is the front view which looked at the 1st yoke member in Example 1 from the axial direction notch side. 6 is a diagram illustrating a cutout shape of a first yoke member in Embodiment 1. FIG. 2 is a cross-sectional view of the bobbin in Example 1 in the AA direction. FIG. It is the figure which looked at the bobbin in Example 1 from the installation surface side of the 2nd yoke member of an axial direction. FIG. 3 is a diagram illustrating the vicinity of a notch in a coil unit according to the first embodiment. It is a figure showing the notch vicinity of the coil unit in Example 2. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Input shaft 1a Convex part 1A Large diameter part 2 Output shaft 2a Groove 3 Torsion bar 3a Fixed part 3b Fixed part 4 Cylindrical member 4a 1st window 4c, 4d Window 4A Small diameter part 5 Cylindrical member 5a, 5b 2nd window 5c, 5d Window 5A Small diameter part 9A, 9B Coil unit 9C, 9D Yoke 9a, 9b Coil 10 First yoke member 11 Bobbin 11a Winding part 11b Bobbin terminal part 11c Wire winding part 11d Bobbin insertion port 11e Bobbin terminal part abutting surface 12 Wiring 13 Terminal 14 Second yoke member 15 Cylindrical portion 16 Bottom portion 16a Opening portion 17 Bending portion 18a, 18b First taper region 19 Abutting region 19a Protruding portion 20a, 20b Second taper region 21 Notch 21a Coil escape groove 22 Notch 22a Coil escape groove 23a, 23b Third taper region

Claims (1)

A rotating shaft connected by a torsion bar;
A cylindrical coil unit provided so as to surround the rotating shaft;
Impedance variable means for changing the impedance of the coil of the coil unit in accordance with a change in torque acting on the rotating shaft;
With
In the torque sensor for detecting the torque generated in the rotating shaft based on the impedance change by the impedance variable means,
The coil unit includes a bobbin composed of a winding part around which the coil is wound, and a terminal part that pulls the coil to the outside.
And a yoke that is housed in the bobbin and in which a notch for pulling out the terminal portion of the bobbin is formed,
The notch of the yoke is formed with a protrusion that protrudes toward the axial end face side of the terminal at the circumferential center of the notch, and coil escape grooves that are formed on both sides of the protrusion in the circumferential direction. A featured torque sensor.

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