U.S. patent application number 11/707158 was filed with the patent office on 2007-08-23 for rotation angle detecting device.
This patent application is currently assigned to DENSO CORPORATION. Invention is credited to Shigetoshi Fukaya, Shinji Hatanaka, Kenji Takeda.
Application Number | 20070194786 11/707158 |
Document ID | / |
Family ID | 37946418 |
Filed Date | 2007-08-23 |
United States Patent
Application |
20070194786 |
Kind Code |
A1 |
Hatanaka; Shinji ; et
al. |
August 23, 2007 |
Rotation angle detecting device
Abstract
A rotation angle detecting device is rotated by a rotating
object via a gear mechanism to detect a rotation angle of the
rotating object. The rotation angle detecting device includes a
housing, a magnet rotor unit having a permanent magnet and a
central hole, a magnetic sensor unit including a pair of magnetic
sensor elements each of which detects magnetic flux density of a
magnetic field generated by the permanent magnet in a direction
different from the other, and a signal processor that calculates a
rotation angle of the rotating object from the magnetic flux
density. The magnetic rotor unit includes a mechanism for changing
the magnetic flux density as the number of turns of the magnet
rotor unit changes.
Inventors: |
Hatanaka; Shinji;
(Okazaki-city, JP) ; Takeda; Kenji; (Okazaki-city,
JP) ; Fukaya; Shigetoshi; (Toyota-city, JP) |
Correspondence
Address: |
NIXON & VANDERHYE, PC
901 NORTH GLEBE ROAD, 11TH FLOOR
ARLINGTON
VA
22203
US
|
Assignee: |
DENSO CORPORATION
Kariya-city
JP
NIPPON SOKEN, INC.
Nishio-city
JP
|
Family ID: |
37946418 |
Appl. No.: |
11/707158 |
Filed: |
February 16, 2007 |
Current U.S.
Class: |
324/207.25 |
Current CPC
Class: |
G01D 5/145 20130101 |
Class at
Publication: |
324/207.25 |
International
Class: |
G01B 7/30 20060101
G01B007/30 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 23, 2006 |
JP |
2006-47042 |
May 15, 2006 |
JP |
2006-135351 |
Claims
1. A rotation angle detecting device rotated by rotating object via
a gear mechanism to detect a rotation angle .phi. of the rotating
object comprising: a housing; a magnet rotor unit having a
permanent magnet and a central hole, said rotor unit is rotatably
supported by the housing; a magnetic sensor unit including a pair
of magnetic sensor elements each of which detects magnetic flux
density Bx, By of a magnetic field generated by the permanent
magnet in a direction different from the other, said magnetic
sensor unit being supported by the housing to be disposed in the
central hole to provide a pair of output signals corresponding to
magnetic flux densities; and a signal processor for calculating a
rotation angle .phi. of the rotating object from the magnetic flux
density, wherein the magnetic rotor unit comprises means for
changing the magnetic flux density as the number of turns of the
magnet rotor unit changes.
2. A rotation angle detecting device as in claim 1, wherein the
signal processor calculates the rotation angle of the rotating
object from the magnetic flux density and data of a vector length
of the magnetic flux density relative to the number of turns of the
magnet rotor unit.
3. A rotation angle detecting device as in claim 2, wherein the
signal processor calculates the rotation angle of the rotating
object in the following steps: calculating a rotation angle of the
magnetic rotor unit from arctan of a ratio of the magnetic flux
densities that is By/Bx; calculating the rotation angle of the
rotating object from the rotation angle and the data of the vector
length.
4. A rotation angle detecting device as in claim 1, wherein the
permanent magnet has a conical inside surface that surrounds the
magnetic sensor unit.
5. A rotation angle detecting device as in claim 1, wherein the
means for changing the magnetic flux density changes position of
the permanent magnet relative to the magnetic sensor unit as the
magnet rotor unit rotates.
6. A rotation angle detecting device as in claim 1, the means for
changing the magnetic flux density comprises a pair of screw member
disposed between a portion of the magnetic rotor unit and the
magnetic sensor to change the magnetic flux density as the rotor
unit rotates relative to the housing.
7. A rotation angle detecting device as in claim 1, the permanent
magnet is polarized in a direction perpendicular to the rotation
axis of the permanent magnet.
8. A rotation angle detecting device as in claim 1, further
comprising a gear mechanism disposed between the rotating object
and the magnet rotor unit to transmit rotation of the rotating
object to the magnet rotor unit.
9. A rotation angle detecting device as in claim 1, wherein the
pair of the magnetic sensor elements is disposed in a chip to be
perpendicular to each other.
10. A rotation angle detecting device as in claim 1, wherein the
magnetic sensor unit is integrated into the signal processor.
11. A rotation angle detecting device as in claim 1, wherein the
magnet rotor unit further comprises a magnetic yoke disposed around
the permanent magnet.
12. A rotation angle detecting device as in claim 11, wherein the
signal processor calculates the rotation angle of the rotating
object from the magnetic flux density Bx, By and data of a vector
length of the magnetic flux density relative to the number of turns
of the magnet rotor unit.
13. A rotation angle detecting device as in claim 12, wherein the
signal processor calculates the rotation angle of the rotating
object in the following steps: calculating a rotation angle of the
magnetic rotor unit from arctan By/Bx; calculating the rotation
angle of the rotating object from the rotation angle and the data
of the vector length.
14. A rotation angle detecting device as in claim 11, wherein the
means for changing the magnetic flux density changes position of
the permanent magnet relative to the magnetic sensor unit as the
magnet rotor unit rotates.
15. A rotation angle detecting device as in claim 14, the means for
changing the magnetic flux density comprises a pair of screw member
disposed between the permanent magnet and the magnetic sensor.
16. A rotation angle detecting device as in claim 11, the permanent
magnet is polarized in a direction perpendicular to the rotation
axis of the permanent magnet.
17. A rotation angle detecting device as in claim 11, wherein the
permanent magnet has a conical hole that surrounds the magnetic
sensor unit.
18. A rotation angle detecting device as in claim 11, further
comprising a gear mechanism disposed between the rotating object
and the magnet rotor unit.
19. A rotation angle detecting device as in claim 11, wherein the
pair of the magnetic sensor elements is disposed in a chip to be
perpendicular to each other.
20. A rotation angle detecting device as in claim 11, wherein the
magnetic sensor unit is integrated into the signal processor.
21. A rotation angle detecting device as in claim 17, wherein: the
yoke comprises a cup-shaped member that has a disk portion (3a) at
the bottom thereof; and the disk portion has a depression formed on
the side of the disk portion 3a facing the permanent magnet.
22. A rotation angle detecting device as in claim 21, wherein the
depression is a cylindrical space that has an outside diameter
larger than the smallest diameter of the conical hole of the
permanent magnet and smaller than the outside diameter of the
permanent magnet.
23. A rotation angle detecting device as in claim 21, further
comprising a gear mechanism disposed between the rotating object
and the magnet rotor unit to transmit rotation of the rotating
object to the magnet rotor unit, wherein the yoke has teeth of the
gear mechanism on the outer surface thereof.
24. A rotation angle detecting device as in claim 23, wherein the
means for changing the magnetic flux density comprises a pair of
screw member disposed between a portion of the magnetic rotor unit
and the magnetic sensor unit to move the magnet rotor unit relative
to the magnetic sensor unit as the rotor unit rotates relative to
the housing.
25. A rotation angle detecting device as in claim 23, further
comprising a holding member fixed to the housing to hold the outer
periphery of the teeth.
26. A rotation angle detecting device as in claim 25, wherein the
means for changing the magnetic flux density comprises a pair of
screw member disposed between the magnetic yoke and the holding
member to move the magnetic yoke relative to the magnetic sensor
unit as the rotor unit rotates relative to the housing.
27. A rotation angle detecting device as in claim 26, wherein: the
magnet rotor unit further comprises a rotor shaft; and the housing
comprises an insert member that supports the rotor shaft as a
bearing so that the magnet rotor shaft can rotate and also
vertically slide therein.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] The present application is based on and claims priority from
Japanese Patent Applications 2006-47042, filed Feb. 23, 2006 and
2006-135351, filed May 15, 2006, the contents of which are
incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a rotation angle detecting
device that detects the rotation angle of a rotary shaft of a
rotating object, such as a steering wheel of a vehicle, by
detecting change of magnetic flux density.
[0004] 2. Description of the Related Art
[0005] JP-A-2005-3625 or U.S. Pat. No. 6,861,837 B1, which is a
counterpart of the former, discloses a prior art rotation angle
detecting device that detects a rotation angle of a rotating object
larger than 360 degrees in angle. As shown in FIG. 14 of this
application, the prior art rotation angle detecting device includes
a pair of permanent magnets 80, 90 each of which is separately
linked with a rotary shaft 40 of a rotating object via gear
mechanism and a pair of magnetic sensors 100, 110, each of which
detects magnetic flux density of a magnetic field generated by the
permanent magnets 80, 90. The gear mechanism is comprised of three
gears: a drive gear 70 that is fixed to the rotary shaft of the
rotating object and two driven gears 50, 60 to which the permanent
magnets 80, 90 are respectively,fixed. The number of teeth of the
driven gear 50 is different from the other driven gear 60 to change
the phase between the output signals of the magnetic sensors 100,
110 as the driven gears 50, 60 rotate so that the rotation angle
larger than 360 degrees in angle can be calculated from the phase
difference. In other words, the gear mechanism includes at least
three gears (70, 80, 90), which increase the size and parts of the
rotation angle detecting device.
SUMMARY OF THE INVENTION
[0006] Therefore, an object of the invention is to provide a more
compact rotation angle detecting device.
[0007] According to a feature of the invention, a rotation angle
detecting device rotated by rotating object via a gear mechanism to
detect a rotation angle of the rotating object includes a magnet
rotor unit having a permanent magnet and a central hole, a magnetic
sensor unit that is disposed in the inside hall and includes a pair
of magnetic sensor elements each of which detects magnetic flux
density Bx, By of a magnetic field generated by the permanent
magnet in a direction different from the other, and a signal
processor for calculating a rotation angle of the rotating object
from the magnetic flux density. Further, the magnetic rotor unit
includes a mechanism for changing the magnetic flux density as the
number of turns of the magnet rotor unit changes.
[0008] In the above rotation angle detecting device, there are the
following features:
[0009] (1) the signal processor calculates the rotation angle of
the rotating object from the magnetic flux density and data of a
vector length of the magnetic flux density relative to the number
of turns of the magnet rotor unit;
[0010] (2) the signal processor calculates the rotation angle of
the rotating object in the following steps: calculating a rotation
angle of the magnetic rotor unit from arctan By/Bx; calculating the
rotation angle of the rotating object from the rotation angle of
the magnet rotor unit and the data of the vector length;
[0011] (3) the permanent magnet has a conical inside surface that
surrounds the magnetic sensor unit;
[0012] (4) the mechanism for changing the magnetic flux density
changes position of the permanent magnet relative to the magnetic
sensor unit as the magnet rotor unit rotates;
[0013] (5) the mechanism for changing the magnetic flux density
includes a pair of screw member disposed between a portion of the
magnetic rotor unit and the magnetic sensor to change the magnetic
flux density as the rotor unit rotates relative to the housing;
[0014] (6) the permanent magnet is polarized in a direction
perpendicular to the rotation axis of the permanent magnet;
[0015] (7) a gear mechanism is disposed between the rotating object
and the magnet rotor unit to transmit rotation of the rotating
object to the magnet rotor unit;
[0016] (8) the pair of the magnetic sensor elements is disposed in
a chip to be perpendicular to each other;
[0017] (9) the magnetic sensor unit is integrated into the signal
processor; and
[0018] (10) the magnet rotor unit further includes a magnetic yoke
disposed around the permanent magnet.
[0019] According to another feature of the invention, the signal
processor calculates the rotation angle of the rotating object from
the magnetic flux density Bx, By and data of a vector length of the
magnetic flux density relative to the number of turns of the magnet
rotor unit.
[0020] The yoke may include a cup-shaped member that has a disk
portion at the bottom thereof, and the disk portion has a
depression formed on the side of the disk portion 3a facing the
permanent magnet. The depression may be a cylindrical space that
has an outside diameter larger than the smallest diameter of the
conical hole of the permanent magnet and smaller than the outside
diameter of the permanent magnet. A holding member may be fixed to
the housing to hold the outer periphery of the teeth that are
formed on the magnetic yoke. A pair of screw member may be disposed
between the magnetic yoke and the holding member to move the
magnetic yoke relative to the magnetic sensor unit as the rotor
unit rotates relative to the housing.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] Other objects, features and characteristics of the present
invention as well as the functions of related parts of the present
invention will become clear from a study of the following detailed
description, the appended claims and the drawings. In the
drawings:
[0022] FIGS. 1A and 1B are, respectively, a schematic
cross-sectional longitudinal view and a schematic plan view of a
steering angle detecting device according to the first embodiment
of the invention;
[0023] FIG. 2 is a graph showing a relation between the rotation
angle .phi. of a steering wheel shaft and magnetic flux densities
Bx, By along X, Y axes;
[0024] FIG. 3 is a graph showing a relation between the rotation
angle of the steering wheel shaft and arctangent of By/Bx;
[0025] FIG. 4 is a graph showing relation between the rotation
angle .theta. of a permanent magnet and vector length of magnetic
flux density;
[0026] FIG. 5 is a cross-sectional view of a rotation angle
detecting device according to the second embodiment of the
invention;
[0027] FIG. 6 is a cross-sectional view of a rotation angle
detecting device according to the third embodiment of the
invention;
[0028] FIG. 7 is a cross-sectional view of a rotation angle
detecting device according to the fourth embodiment of the
invention;
[0029] FIG. 8 is a cross-sectional view of a rotation angle
detecting device according to the fifth embodiment of the
invention;
[0030] FIG. 9 is a graph showing a relation between the depth of a
bottom gap of the seventh embodiment and magnetic flux density to
be detected by the magnetic sensor thereof;
[0031] FIG. 10 is a cross-sectional view of a variation of the
rotation angle detecting device according to the fifth
embodiment;
[0032] FIGS. 11A and 11B are, respectively, a plan view and a
cross-sectional view of a rotation angle detecting device according
to the sixth embodiment of the invention;
[0033] FIG. 12 is a cross-sectional view of a rotation angle
detecting device according to the seventh embodiment of the
invention;
[0034] FIG. 13 is a cross-sectional view of a variation of the
rotation angle detecting device according to the seventh
embodiment; and
[0035] FIG. 14 is a schematic diagram of a prior art rotation angle
detecting device.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0036] Several preferred embodiments of the invention will be
described with reference to the appended drawings.
[0037] A vehicle steering angle detecting device according to the
first embodiment of the invention will be described with reference
to FIGS. 1A, 1B-4.
[0038] The vehicle steering angle detecting device is a device that
detects the rotation angle of the rotary shaft 9 of a vehicle
steering wheel (not shown). The vehicle steering angle detecting
device includes a housing 1, a magnet rotor shaft 2, a cylindrical
magnetic yoke 3 made of a soft iron, a cylindrical permanent magnet
4, a male screw 5, a female screw 6, a magnetic sensor unit 7, a
signal processor 8, a spur gear 10, a gear teeth 11, etc.
[0039] The magnet rotor shaft 2, the magnetic yoke 3, the permanent
magnet 4, the male screw 5 and the teeth 11 form a magnet rotor
unit. The cylindrical magnetic yoke 3 is fixed to the magnet rotor
shaft 2 to increase the magnetic flux density generated by the
permanent magnet 4, which is held by the inner wall of the yoke 3.
The cylindrical permanent magnet 4 has a center hole that is
defined by a conical surface whose inside diameter increases as the
surface goes upward as shown in FIG. 1A.
[0040] As shown in FIG. 1B, the permanent magnet 4 is polarized to
have N and S poles in a direction in parallel with X axis that is
perpendicular to a vertical center line M of the magnet rotor shaft
2. The male screw 5 is formed on the surface of the magnet rotor
shaft 2. The female screw 6 is formed in the housing 1 to receive
the male screw 5 so that the male screw 5 can move up or down by
0.5 mm as the magnet rotor shaft 2 rotates a half turn (180 degrees
in angle) in one direction or the other. A spring member may be
disposed between the housing 1 and the magnet rotor shaft 2 or the
yoke 3 to eliminate an excessive engagement play.
[0041] The magnetic sensor unit 7 is disposed at the central hole
of the permanent magnet 4 on the vertical center line M of the
magnet rotor shaft 2. The magnetic sensor unit 7 is comprised of an
integrated circuit (IC) chip that includes a pair of Hall elements
(i.e. magnetic sensor elements) and related peripheral circuits.
One of the Hall elements outputs a voltage signal Vx that is
proportional to an X axis component Bx of the magnetic flux density
B of the magnetic field generated by the permanent magnet 4, and
the other Hall element outputs a voltage signal Vy that is
proportional to a Y axis component By of the magnetic flux density
B.
[0042] The magnet rotor unit is disposed so that its center axis M
can be in parallel with the rotating axis of the spur gear 10, and
the gear teeth 11 are formed on the outer surface of the yoke 3 so
as to mesh with the spur gear 10, In this case, the ratio of the
number of gear teeth 11 to the spur gear is 1/2.
[0043] When the magnet rotor unit rotates in one direction, it
moves downward. Accordingly, the distance between the conical
surface of the permanent magnet 4 and the magnetic sensor unit 7
increases, and the magnetic flux density B decreases, as shown in
FIG. 4 by a broken line. On the other hand, the magnet rotor unit
moves upward when it rotates in the other direction. In this case,
the magnetic flux density B increases.
[0044] Assuming that the magnitude or vector length of the flux
density B is f(.theta.) when the rotation angle of the permanent
magnet 4 relative to the X axis is .theta., the X axis component Bx
and the Y-axis component By are expressed as follows.
Bx=f(.theta.)cos .theta. (1)
By=f(.theta.)sin .theta. (2)
[0045] The vector length f(.theta.) changes as the size, shape or
material of the permanent magnet 4 or magnetic yoke 3 changes.
[0046] The signal processor 8 calculates the rotation angle .theta.
within 360 degrees from the flux density components Bx, By by the
following expression.
.theta.=arctan(By/Bx) (3)
[0047] Then, the signal processor 8 calculates the vector length of
B at an angle .theta. by the following expression.
f(.theta.)=(Bx.sup.2+By.sup.2).sup.1/2 (4)
[0048] The vector length f(.theta.) that corresponds to plural
rotation angles of the permanent magnet beyond the range 360
degrees, are thus calculated and stored in a map that is included
in the signal processor 8.
[0049] FIG. 2 is a graph showing the relation between the magnetic
flux densities Bx, By and the rotation angle .theta.' of the
permanent magnet 4 or the rotation angle .phi. of the rotary shaft
9, and FIG. 3 is a graph showing the relation between the value of
arctan (By/Bx) and the rotation angle .theta.' of the permanent
magnet 4 or the rotation angle .phi. of the rotary shaft 9.
[0050] The number of times of the rotation can be calculated from
the vector length f(.theta.) and the rotation angle .theta. (within
360 degrees) is calculated from the expression (3). Assuming that
the number of times of the rotation is "2" and that the calculated
rotation angle .theta. is "55", the actual rotation angle .theta.'
(larger than 360 degrees) is 360 degrees+55 degrees=415
degrees.
[0051] Thus, the actual rotation angle .theta.' larger than 360
degrees in angle can be calculated.
[0052] In this embodiment, the magnetic flux density Bx, By can be
detected by demodulating the wave form shown in FIG. 3 while the
rotary shaft 9 is rotating. The cylindrical magnetic yoke 3 or the
cylindrical permanent magnet 4 can be replaced with a magnetic yoke
or permanent magnet having an elliptic or a polygonal
cross-section. The rotation angle .theta. of the permanent magnet 4
that is smaller than 360 degrees can be also calculated from the
characteristic curve of the vector length in addition to the
characteristic curve of arctan (By/Bx), as shown in FIG. 4.
[0053] As a variation, the male and female screws 5, 6 of the first
embodiment can be omitted by changing the teeth of the spur gear 10
and the gear teeth 11 to a pair of gears (such as spiral gears)
that moves the permanent magnet 4 vertically at a prescribed degree
when the rotary shaft 9 rotates. Instead of the gear teeth 11 being
directly formed on the outer surface of the magnetic yoke 3, a ring
member on which the gear teeth 11 are formed can be fixed to the
outer surface of the magnetic yoke 3. The magnetic yoke 3 can be
omitted by forming the gear teeth 11 on the outer surface of the
permanent magnet 4 if an outside magnetic noise is negligible.
Further, the spur gear 10 may be a non-backlash gear that is
constituted of a pair of gears connected by a spring member to
prevent a back lash. The conical surface of the center hole of the
permanent magnet 4 can be modified to a stepped inclined surface
whose inside diameter increased stepwise as the surface goes
upward. The distance between the surface of the permanent magnet 4
and the magnetic sensor unit 7 increases stepwise when the magnet
rotor turns over 360 degrees, and the magnetic flux density B
decreases stepwise.
[0054] A rotation angle detecting device according to the second
embodiment of the invention will be described with reference to
FIG. 5. Incidentally, the same reference numeral as the first
embodiment represents the same or substantially the same part,
portion or component as the first or a precedent embodiment,
hereafter.
[0055] The teeth of the gear 10 and the teeth 11 are formed spiral
as the above variation of the first embodiment, and are arranged so
that only the magnetic yoke 3 can be moved upward or downward along
the outer surface of the permanent magnet 4, as shown in FIG. 5. As
the magnetic yoke 3 is moved upward or downward by the gear 10
(shown in FIG. 1), the vector length of the magnetic flux density
changes in substantially the same manner as the first embodiment.
The center hole of the permanent magnet may be cylindrical instead
of conical.
[0056] A rotation angle detecting device according to the third
embodiment of the invention will be described with reference to
FIG. 6.
[0057] Instead of the permanent magnet 4 having the conical
surface, a permanent magnet 4 having a cylindrical surface and a
second magnetic yoke 12 having a conical inner surface are combined
in this embodiment. The second magnetic yoke 12 is fitted to the
cylindrical inner surface of the permanent magnet 4. It is easy to
provide a suitable inner surface of the second yoke 12, so that
more suitable vector length f(.theta.) can be provided by machining
the second yoke 12.
[0058] A rotation, angle detecting device according to the fourth
embodiment of the invention will be described with reference to
FIG. 7.
[0059] This rotation angle detecting device includes a magnetic
disk 13 in addition to the housing 1, the magnet rotor shaft 2, the
cylindrical magnetic yoke 3, the cylindrical permanent magnet 4,
the male screw 5, the female screw 6, the magnetic sensor unit 7,
the signal processor 8, the spur gear 10 and the a gear teeth 11 of
the first embodiment. However, the gear teeth 11 and the female
screw 6 are respectively formed on the peripheral surface and the
center hole of the magnetic disk 13 so that only the magnetic disk
13 can be driven by the screw 5 in the vertical direction and
rotated by the spur gear 10 as the rotary shaft 9 rotates.
[0060] As the magnetic disk 13 is moved upward or downward, the
vector length f(.theta.) or the vector length of the magnetic flux
density changes in substantially the same manner as the first
embodiment. The center hole of the permanent magnet may be also
cylindrical instead of conical.
[0061] A rotation angle detecting device according to the fifth
embodiment of the invention will be described with reference to
FIGS. 8-10.
[0062] The magnet rotor shaft 2, the magnetic yoke 3, the permanent
magnet 4, the male screw 5 and the teeth 11 form a unitary magnet
rotor unit 21. The magnetic yoke 3 is a cup-shaped member that has
a disk portion 3a at the bottom thereof. The permanent magnet 4 is
fitted to the inside surface of the magnetic yoke 3. A cylindrical
depression 3b is formed on the side of the disk portion 3a facing
the permanent magnet 4. The cylindrical depression 3b has an
outside diameter that is larger than the smallest diameter of the
conical hole of the permanent magnet 4 and smaller than the outside
diameter of the permanent magnet 4. The outside diameter of the
depression 3b is preferably as large as the arithmetical means of
the outside diameter of the permanent magnet 4 and the smallest
diameter of the conical hole of the permanent magnet 4, and the
depth is designed to provide a suitable magnetic flux density.
[0063] As shown in FIG. 9, the ratio (%) of the magnetic flux
density B measured at the portion to the corresponding portion of
the first embodiment changes as the diameter of the depression 3b
and the depth thereof change. The depth is usually between 1 mm and
10 mm and, preferably, larger than 2 mm. The shape of the
depression 3b may be other than cylindrical, such as rectangular,
conical or elliptical shape. As shown in FIG. 10, the depression 3b
may be filled with a non-magnetic member 3c.
[0064] A rotation angle detecting device according to the sixth
embodiment of the invention will be described with reference to
FIGS. 11A and 11B.
[0065] The housing 1 has a semi-cylindrical sleeve 22 that holds
the outer periphery of the teeth 11 and an insert member 23 that
has the female screw 6. The sleeve 22 has an arc-shaped opening of
about a quarter length of the whole circumference of the sleeve 22,
from which the teeth 11 of the magnetic yoke 3 projects to mesh
with the gear 10. The female screw 6 of the insert member 23
slidably receives the male screw 5 formed on the outer periphery of
the magnet rotor shaft 2. The sleeve 22 may be formed separately
from the case 1 or may be integrated with the case 1. The
semi-cylindrical sleeve is effective to eliminate an excessive
engagement play between the gear 10 and the teeth 11. The magnetic
sensor unit 7 is supported via a pole member 71 by a circuit board
72.
[0066] A rotation angle detecting device according to the seventh
embodiment of the invention will be described with reference to
FIGS. 12 and 13.
[0067] A male screw 3c is formed at the teeth 11 on the outer
periphery of the magnetic yoke 3 instead of the male screw 5 formed
on the magnet rotor shaft 2, and a female screw 22a is formed on
the inner periphery of the semi-cylindrical sleeve 22 instead of
the female screw 6 formed in the insert member 23. The insert
member 23 supports the magnet rotor shaft 2 as a bearing so that
the magnet rotor shaft 2 can rotate and also vertically slide
therein. As a variation, the magnet rotor shaft 2 and the insert
member 23 can be omitted as shown in FIG. 13.
[0068] In the foregoing description of the present invention, the
invention has been disclosed with reference to specific embodiments
thereof. It will, however, be evident that various modifications
and changes may be made to the specific embodiments of the present
invention without departing from the scope of the invention as set
forth in the appended claims. Accordingly, the description of the
present invention is to be regarded in an illustrative, rather than
a restrictive, sense.
* * * * *