FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
(See section 10, rule 13)
“TORQUE DETECTION DEVICE, ELECTRIC POWER STEERING
DEVICE, AND VEHICLE”
NSK LTD., of 6-3, Ohsaki 1-chome, Shinagawa-ku, Tokyo
1418560 Japan
The following specification particularly describes the invention and the manner in which
it is to be performed.
2
DESCRIPTION
TORQUE DETECTION DEVICE, ELECTRIC POWER STEERING DEVICE, AND
VEHICLE
Technical Field
[0001]
The present invention relates to a torque detection
apparatus configured to detect torque generated at a rotation
shaft, an electric power steering apparatus, and a vehicle,
each including the torque detection apparatus.
Background Art
[0002]
As an electric power steering apparatus, in one
technology, for example, there is a technology disclosed in
Patent Literature 1. In such a technology, a torque sensor,
in which two coil units respectively including coil bobbins
around which coils are wound are opposed to each other, is
arranged at the inside of a holder formed of an
electromagnetic yoke and a yoke cover.
Citation List
Patent Literature
[0003]
PLT 1: WO 2004/018987
Summary
3
Technical Problem
[0004]
In the technology as disclosed in PLT 1, however, each
coil unit includes a single coil bobbin and a single
electromagnetic yoke and a single yoke cover, respectively.
After the coil bobbin is fit at the inside of the
electromagnetic yoke, the process of press-fitting the yoke
cover into the inner diameter of the electromagnetic yoke has
to be conducted for each coil unit.
Therefore, it is an object of the present invention to
provide a torque detection apparatus capable of achieving a
reduction in the number of component members and an
improvement in the assembling performance, an electric power
steering apparatus, and a vehicle, each including the torque
detection apparatus.
Solution to Problem
[0005]
In order to address the above drawbacks, in one
embodiment of the present invention, there is provided a
torque detection apparatus, including: a pair of detection
coils configured to change impedances in opposite directions
to each other depending on torque generated at a rotation
shaft; two coil bobbins having reel shapes around which the
pair of detection coils are wound, respectively; two
electromagnetic yokes having cylindrical portions in which
the two coil bobbins are fit and held, respectively; and a
yoke cover configured to be press-fit into inner diameters
4
of the cylindrical portions of the two electromagnetic yokes
at a position interposed by the two electromagnetic yokes
facing each other in an axial direction, wherein the torque
is detected based on output voltages of the pair of detection
coils.
[0006]
As described above, two coil bobbins around which the
detection coils are wounded, respectively, are positioned to
face each other. The yoke cover is interposed between them.
The yokes are press-fit with the two coil bobbins from both
sides in the axial direction to integrate the detection coils
corresponding to two parts. In other words, only one yoke
cover is provided for two yokes, and the number of times of
press-fitting the yoke cover is once. Accordingly, as
compared to a case where one coil bobbin, one yoke, and one
yoke cover are provided, one yoke cover is press-fit into one
yoke, and then two yokes into which two yoke covers are
respectively press-fit are integrated together, the number
of parts corresponding to one yoke cover can be reduced, and
the number of times of press-fitting the yoke cover into the
yoke can be reduced, too.
[0007]
In addition, the above-described torque detection
apparatus may further include a press-fit regulation portion
configured to regulate a press-fit depth of the yoke cover
with respect to the two electromagnetic yokes. Accordingly,
it is possible to prevent one yoke cover from being press-fit
5
into one of the yokes completely, and it is possible to
press-fit one yoke cover into two yokes.
Further, in the above-described torque detection
apparatus, the press-fit regulation portion may be formed at
an end portion in the axial direction of each of the
cylindrical portions of the two electromagnetic yokes, and
is configured with a depression portion being depressed in
the axial direction and a projection portion being formed at
the yoke cover to project outwardly in a radial direction with
respect to an inner diameter of each of the two
electromagnetic yokes, and the press-fit depth of the yoke
cover with respect to each of the two electromagnetic yokes
may be regulated by abutting an end face on an outer side in
the axial direction of the projection portion against a bottom
portion of the depression portion. Accordingly, it is
possible to regulate the press-fit depth of the yoke cover
into the yokes, with a relatively simple configuration.
[0008]
In addition, in the above-described torque detection
apparatus, the yoke cover may include an R portion at an end
portion in the axial direction on an outer circumferential
face. Thus, it is possible to improve the press-fit
performance of the yoke cover into the yokes.
Further, the above-described torque detection apparatus
may further include a regulation portion configured to
regulate a phase difference in a circumferential direction
between the two coil bobbins, on a mating face side of each
of the two coil bobbins.
6
Thus, it is possible to prevent the coil bobbins making
a pair from rotating in the circumferential direction, and
to regulate a phase displacement. Therefore, when the coil
bobbin is provided with a coil side terminal for connection
with the sensor circuit board, it is possible to maintain the
position of the coil side terminal always at a given position.
Accordingly, it is possible to connect the coil with the
circuit board appropriately.
[0009]
In addition, in the above-described torque detection
apparatus, the regulation portion may be a step portion in
which a depression and a protrusion are arranged in parallel
to each other in the circumferential direction on the mating
face side of each of the two coil bobbins. In this manner,
it is possible to regulate a phase difference in the
circumferential direction of both of the coil bobbins with
a relatively simple configuration.
Further, the above-describe torque detection apparatus
may further include: a terminal attachment portion formed at
an end portion of a side face of each of the two coil bobbins
and having terminals to which a tip portion and a termination
portion of one of the pair of detection coils are attached,
respectively; and a movement regulation portion configured
to regulate a movement in the axial direction of the terminal
attachment portion with respect to the two coil bobbins facing
each other.
7
As described above, the position accuracy of the coil
side terminal can be ensured by regulating the movement in
the axial direction of the terminal attachment portion.
Thus, even when the coil side terminal is inserted and
soldered into the through hole of the printed board, it is
possible to insert the coil side terminal into the through
hole with ease and improve the assembling performance.
[0010]
Further, in the above-described torque detection
apparatus, the movement regulation portion may be configured
with a first projection portion formed by a part of a flange
portion of a first one of the two coil bobbins projecting
outwardly in the radial direction, and a movement of the
terminal attachment portion formed at a second one of the two
coil bobbins in the axial direction and toward the first one
side of the two coil bobbins may be regulated by abutting the
first projection portion formed at the first one of the two
coil bobbins against at least a part of the movement
regulation portion formed at the second one of the two coil
bobbins from mating face sides of the two coil bobbins.
As described above, as the movement regulation portion
is formed by a part of the flange portion of the coil bobbin,
it is possible to regulate the movement in the axial direction
of the terminal attachment portion with a relatively simple
configuration.
[0011]
Further, in the above-described torque detection
apparatus, the movement regulation portion may be configured
8
with a second projection portion formed by a part of the
terminal attachment portion projecting outwardly in the
circumferential direction, and a movement of the terminal
attachment portion formed at the second one of the two coil
bobbins in the axial direction and toward an opposite side
to the first one of the two coil bobbins may be regulated by
abutting the second projection portion formed at the terminal
attachment portion formed at the first one of the two coil
bobbins against at least a part of the terminal attachment
portion formed at the second one of the two coil bobbins from
an opposite side to the mating faces of the two coil bobbins.
As described above, as the movement regulation portion
is formed by a part of the terminal attachment portion, it
is possible to regulate the movement in the axial direction
of the terminal attachment portion with a relatively simple
configuration.
[0012]
In addition, the above-described torque detection
apparatus may further include: a circuit board having a torque
detection function configured to detect the output voltages
of the pair of detection coils and to detect the torque based
on the output voltages; a board side connector mounted on the
circuit board; and a coil side connector formed at each of
the two coil bobbins, having the terminal attachment portion
and the terminals, and being electrically connectable to the
board side connector.
As described above, the coil side connector and the board
side connector are connected, and then the detection coil and
9
the circuit board are electrically connected. In addition,
the use of connector connection eliminates the necessity of
soldering to connect the detection coil and the circuit board,
unlike the prior art technology. For this reason, the
assembling process can be simplified and the quality can be
improved, too.
[0013]
Further, in the above-described torque detection
apparatus, the board side connector may be a connector having
a same number of movable pieces to a number of the detection
coils. As described above, since the board side connector
is configured with a movable connector, even if the relative
positional displacement caused by an assembling error occurs
at the coil side terminal, the coil side terminal can be
connected to the board side connector with certainty.
In addition, in the above-described torque detection
apparatus, the board side connector may have two movable
pieces corresponding to the pair of detection coils. In this
manner, since a pair of detection coils (i.e., two detection
coils) are provided, assembling is made easy and the
configuration of the board side connector is simplified.
Furthermore, in the above-described torque detection
apparatus, the coil side connector may include: the terminals
configured to stand up at the terminal attachment portion,
in an insertion direction of the coil side connector into the
board side connector; and a plate-shaped guide portion formed
at at least one side face of the terminal attachment portion
and protruding in the insertion direction.
10
Accordingly, the insertion performance at the time of
inserting the coil side connector into the board side
connector can be improved. In addition, since the guide
portion can be arranged at a position surrounding the coil
side terminal, the coil side terminal can be protected.
[0014]
In addition, in another embodiment of the present
invention, there is provided an electric power steering
apparatus, including: an electric motor configured to apply
to a steering system a steering assist force to reduce a
steering burden of a driver; the torque detection apparatus
according to any one of claim 1 to claim 13 configured to detect
steering torque input into a steering mechanism; and a motor
controller configured to drive and control the electric motor
to apply the steering assist force based on at least the
steering torque detected by the torque detection apparatus.
As described above, it is possible for the torque
detection apparatus with high assembling performance to
detect the steering torque appropriately. Therefore, the
electric power steering apparatus with high reliability can
be achieved.
In addition, in yet another embodiment of the present
invention, there is provided a vehicle including the
above-described electric power steering apparatus. Thus, it
is possible to conduct the steering assist control with high
reliability.
Advantageous Effects
11
[0015]
According to the torque detection apparatus in one
embodiment of the present invention, as the yoke cover to be
press-fit into two yokes holding a pair of coil bobbins,
respectively, is used as a common member, the number of parts
can be reduced. In addition, as the number of times of
press-fitting the yoke cover can be reduced, the assembling
performance can be improved.
Then, in an electric power steering apparatus, and a
vehicle, each including the above torque detection apparatus,
the steering assist control with high reliability can be
achieved.
Brief Description of Drawings
[0016]
FIG. 1 is a cross-sectional view illustrative of
substantial parts of an electric power steering apparatus
including a toque detection apparatus in one embodiment of
the present invention;
FIG. 2 is a view illustrative of a configuration of a
torque detector;
FIG. 3 is a perspective view illustrative of component
members of the torque detector;
FIG. 4 is a view illustrative of a connection method of
the torque detector and a circuit board;
FIG. 5 is a view illustrative of a board side connector;
FIG. 6 is a side view illustrative of component members
of the torque detector;
12
FIG. 7 is a view illustrative of a state where the torque
detector is assembled;
FIG. 8 is a view illustrative of a connection state of
the torque detector and the circuit board;
FIG. 9 is a view illustrative of a coil bobbin in a second
embodiment;
FIG. 10 is a view illustrative of a state where the coil
bobbin in the second embodiment is assembled;
FIG. 11 is a view illustrative of a coil bobbin in a third
embodiment;
FIG. 12 is a view illustrative of a state where the coil
bobbin in the third embodiment is assembled; and
FIG. 13 is a view illustrative of another example of the
connection state of the torque detector and the circuit board.
Description of Embodiments
[0017]
Hereinafter, embodiments of the present invention will
be described with reference to the attached drawings.
In one embodiment of the present invention, a torque
detection apparatus is applied to an electric power steering
apparatus of a vehicle.
FIG. 1 is a cross-sectional view illustrative of
substantial parts of the electric power steering apparatus
in one embodiment of the present invention.
In FIG. 1, reference numeral 5 is a housing, and the
housing 5 has a structure of being divided into two regions,
which are an input shaft side housing portion 5a and an output
13
shaft side housing portion 5b. In the inside of the input
shaft side housing portion 5a, an input shaft 1 is rotatably
supported by a bearing 6a. In addition, in the inside of the
output shaft side housing portion 5b, an output shaft 2 is
rotatably supported by bearings 6b and 6c.
Then, the input shaft 1 and the output shaft 2 are coupled
through a torsion bar 3 arranged at the inside of the input
shaft 1.
[0018]
The input shaft 1, the torsion bar 3, and the output shaft
2 are coaxially arranged, the input shaft 1 and the torsion
bar 3 are pin-connected, and the torsion bar 3 and the output
shaft 2 are spline-coupled. In FIG. 1, the steering wheel,
not illustrated, is integrally attached at a projection end
of the input shaft 1. In addition, a pinion shaft 2a is
integrally formed at the output shaft 2 on the opposite side
of the input shaft 1, and the pinion shaft 2a meshes with a
rack 4 to have a configuration of a rack and pinion type
steering mechanism.
Further, a worm wheel 7 is firmly secured at the output
shaft 2 to be coaxial and integrally rotate with the output
shaft 2, and meshes with a worm 8 to be driven by an electric
motor, not illustrated, at the inside of the output shaft side
housing portion 5b. In the worm wheel 7, a teeth portion 7b
made of a synthetic resin is integrally secured to a metal
hub 7a. The rotation force of the electric motor is
transmitted to the output shaft 2 through the worm 8 and the
worm wheel 7, and applies steering assist torque to the output
14
shaft 2 in an arbitrary direction by appropriately changing
the rotation direction of the electric motor.
[0019]
Next, a description will be given of a torque detector
10 configuring a torque sensor (torque detection apparatus)
TS configured to detect the torque between the input shaft
1 and the output shaft 2.
The torque detector 10 includes a sensor shaft portion
11 formed at the input shaft 1, a pair of detection coils 13a
and 13b arranged at the inside of the input shaft side housing
portion 5a, and a cylindrical member 12 arranged between the
sensor shaft portion 11 and the pair of detection coils 13a
and 13b.
The sensor shaft portion 11 is configured with a magnetic
material, and as illustrated in FIG. 2, plural (nine, in an
example of FIG. 2) projection lines 11a extending in an axial
direction are formed in a circumferential direction at
regular intervals on a surface of the sensor shaft portions
11. In addition, groove portions 11b are formed between the
projection lines 11a, respectively.
On the outside of sensor shaft portions 11, the
cylindrical member 12 configured with a conductive and
non-magnetic material, for example, aluminum to be close to
the sensor shaft portion 11 is arranged coaxially with the
sensor shaft portion 11. As illustrated in FIG. 1, an
extension portion 12e of the cylindrical member 12 is secured
to the outside of an end portion 2e of the output shaft 2.
[0020]
15
The cylindrical member 12 is provided with a first window
sequence configured with plural (nine, in an example of FIG.
2) rectangular windows 12a arranged at regular intervals in
the circumferential direction at positions facing the
projection lines 11a on the surface of sensor shaft portions
11, and a second window sequence configured with plural (nine,
in an example of FIG. 2) rectangular windows 12b having an
identical shape to the rectangular windows 12a and having
different phases in the circumferential direction at
positions deviated from the first window sequence in the axial
direction, respectively.
The outer circumference of the cylindrical member 12 is
surrounded by yokes 15a and 15b configured to hold coil
bobbins 18 around which detection coils 13a an 13b having
identical specifications are wound, respectively. The
detection coils 13a and 13b are arranged coaxially with the
cylindrical member 12, such that the detection coil 13a
surrounds the first window sequence configured with the
windows 12a, and the detection coil 13b surrounds the second
window sequence configured with the windows 12b.
[0021]
The yokes 15a and 15b are secured at the inside of the
input shaft side housing portion 5a, as illustrated in FIG.
1, and output lines of the detection coils 13a and 13b are
connected through a connector (coil side connector) 16 to a
connector (board side connector) 19 of a circuit board 17
arranged at the inside of the input shaft side housing portion
5a. In addition, as another method, although not illustrated,
16
a coil tip portion may be bound to a coil side terminal that
is press-fit into the coil bobbin 18 and secured by soldering,
and then may be inserted into a board through hole and
connected by soldering. Here, including the board side
connector 19, electronic parts that operate as an electric
circuit of the circuit board 17 are mounted on the circuit
board by surface mounting with reflow soldering or lead
soldering.
[0022]
FIG. 3 is a perspective view illustrative of component
members of the torque detector 10.
The coil bobbin 18 is a reel-shaped member made of a
non-conductor such as plastic, and is secured to the input
shaft side housing portion 5a to be coaxial with the input
shaft 2 and the output shaft 3. The coil bobbin 18 includes
a pair of flange portions 18a and 18b, and the coil 13a or
the coil 13b is wound around a groove portion 18c between the
flange portions 18a and 18b.
In the torque detector 10 in one embodiment the present
invention, the two coil bobbins 18, around which the coils
13a and 13b are respectively wound and which have an identical
shape, are used to be opposed to each other.
At a side face end portion of the flange portion 18b,
a terminal attachment portion 18e, to be described later,
configuring the coil side connector 16 to be connectable to
the board side connector 19 is formed, and a regulation
portion 18d is formed at a position of line symmetry, with
a symmetry axis being set as a perpendicular line which
17
virtually goes through the center of the coil bobbin 18 in
the state where the terminal attachment portion 18e is located
at an upper end portion of the coil bobbin 18.
[0023]
The regulation portion 18d includes a base portion that
is a part of the flange portion 18b protruding outwardly in
the radial direction, and a projection portion formed to
protrude outwardly in the axial direction of the coil bobbin
18 at one of the regions of the base portion formed by equally
dividing the base portion in the circumferential direction.
In other words, in a state where the two coil bobbins 18 are
coaxially arranged with the flange portions 18b facing each
other, the regulation portions 18d of both of the coil bobbins
18 abut each other in the circumferential direction, so that
relative positions in the rotational angle direction can be
determined.
It is to be noted that any number of the regulation
portions 18d may be selectable as necessary, as far as two
or more regulation portions 18d are provided for each of the
coil bobbins 18.
The terminal attachment portion 18e is a member having
a substantially rectangular parallelepiped shape that
further protrudes outwardly in the radial direction from an
upper end portion of a side face of the flange portion 18b,
and two terminals (coil side terminals) 18f to be connected
to the board side connector 19 are press-fit into the top face
of the terminal attachment portion 18e. These two coil side
terminals 18f are arranged in parallel to each other, and are
18
secured to protrude outwardly in the radial direction from
the top face of the terminal attachment portion 18e.
[0024]
Further, at one side portion of the terminal attachment
portion 18e, a plate-shaped guide portion 18g that protrudes
outwardly in the radial direction is further formed from the
top face of the terminal attachment portion 18e.
As described above, the coil side connector 16 is
configured with the terminal attachment portions 18e, the
coil side terminals 18f, and the guide portions 18g of the
two coil bobbins 18.
The yokes 15a and 15b are members having an identical
shape, and each of the yokes 15a and 15b is configured with
a cylindrical member 15d which externally fits the coil bobbin
18, and a ring-shaped bottom portion 15e formed at an end
portion that faces outwardly in the axial direction when the
cylindrical member 15d is secured to the coil bobbin 18. The
inner diameter of the bottom portion 15e is same with the inner
diameter of the cylindrical member (groove portion 18c) of
the coil bobbin 18.
Further, in the yokes 15a and 15b, at an end portion of
the opposite side of the bottom portion 15e of the cylindrical
member 15d, three depression portions 15c are formed to be
spaced apart from each other at a given angle in the
circumferential direction. These three depression portions
15c are formed at positions of line symmetry with a symmetry
axis being set as a perpendicular line which virtually goes
through the center of the coil bobbin 18 in the state where
19
the terminal attachment portion 18e is located at an upper
end portion of the coil bobbin 18.
[0025]
Furthermore, a yoke cover 14 is a substantially
ring-shaped member, and three projection portions 14a are
formed on the outer circumferential surface to be spaced apart
from each other at a given angle in the circumferential
direction. This yoke cover 14 is press-fit into the inner
diameters of the cylindrical members 15d of the yokes 15a and
15b with the projection portions 14a being fit in the
depressed portions 15c of the yokes 15a and 15b.
In other words, the press-fit depth when the yoke cover
14 is press-fit into the yokes 15a and 15b is regulated by
the projection portions 14a of the yoke cover 14 and the
depression portions 15c of the yokes 15a and 15b. To be
specific, the axial depth of the depression portions 15c
arranged at the yokes 15a and 15b is configured to be almost
half the thickness of the yoke cover 14 including the
manufacturing tolerance.
[0026]
In addition, R portions (corner R) 14b are respectively
provided at end portions in the axial direction on the outer
circumferential surfaces of the yoke cover 14. The R portion
14b should be arranged on at least a part of the outer
circumferential surface.
It is to be noted that, here, the three projection
portions 14a and the three depression portions 15c are
respectively provided. However, the arranged number and the
20
arranged angle of the projection portions 14a and the
depression portions 15c can be set appropriately.
The board side connector 19 is mounted on the circuit
board 17, as illustrated in FIG. 4. The board side connector
19 has a female terminal, and the coil side connector 16 is
connected to the board side connector 19 in a board thickness
direction, so that an electrical connection between the
torque detector 10 and the circuit board 17 is made available.
In addition, as another method, a coil tip portion may be bound
to a coil side terminal that is press-fit into the coil bobbin
18 and secured by soldering, and then may be inserted into
a board through hole and connected by soldering.
[0027]
FIG. 5 is a view illustrative of a configuration of the
board side connector 19.
The board side connector 19 includes terminals 19a,
terminal movable portions 19b, in each of which a part of the
terminal 19a is made to have a letter U shape, and two housings
19c. The board side connector 19 is a movable connector, and
the terminals 19a and the housings 19c are configured to be
movable individually by an elastic deformation structure of
the terminal movable portion 19b.
When the torque detector 10 is assembled, firstly, the
coils 13a and 13b are wound around the coil bobbins 18,
respectively. When the coil 13a is wound around the coil
bobbin 18, a tip portion of the coil 13a is bound and secured
to one of the coil side terminals 18f by soldering or TIG
welding. After the coil 13a is wound around the groove
21
portion 18c, its termination portion is bound and secured to
the other one of the coil side terminals 18f by soldering or
TIG welding. This assembling method also applies to the coil
13b.
[0028]
Next, the two coil bobbins 18 around which the coils 13a
and 13b are wound are fit into the yokes 15a and 15b,
respectively. Then, these two coil bobbins 18 are arranged
to make the flange portions 18b face each other interposing
the yoke cover 14, as illustrated in FIG. 6, the yokes 15a
and 15b are press-fit with the yoke cover 14 from both sides
in the axial direction.
Accordingly, the coils 13a and 13b of two parts are
integrated, as illustrated in FIG. 7. Such integrated coils
are attached to the inner side of the input shaft side housing
portion 5a.
Then, the depression portions 15d of the yokes 15a and
15b and the projection portions 14a of the yoke cover 14 abut
each other in the axial direction, respectively, so that the
relative position of the yoke cover 14 in a press-fit
direction with respect to the yokes 15a and 15b are regulated.
In addition, as the axial depth of the depression portions
15c provided at the yokes 15a and 15b is almost half the
thickness of the yoke cover 14, the press-fit amount can be
made equal in the yoke 15a and the yoke 15b.
[0029]
Furthermore, the regulation portion 18d in one of the
coil bobbins 18 and the regulation portion 18d in the other
22
one of the coil bobbins 18 engage with each other, so that
the rotation in the circumferential direction of the two coil
bobbins 18 is prevented by step parts of the regulation
portions 18 of the two coil bobbins 18 with each other and
the phase deviation is regulated.
Then, the coil side connector 16 is formed by the two
coil bobbins 18 facing each other to be integrated together,
and such a coil side connector 16 is connected to the board
side connector 19 of the circuit board 17, as illustrated in
FIG. 8.
A torque operation circuit, not illustrated,
configuring the torque sensor TS is mounted on the circuit
board 17, the torque operation circuit is configured to detect
output voltages of the two coils 13a and 13b and to detect
the steering torque applied to the steering wheel and then
transmitted to the input shaft 1 based on a difference between
the output voltages. Thus, the torque sensor TS is configured
to detect the relative displacement (rotational
displacement) between the input shaft 1 and the output shaft
2 to correspond to a change in the impedance of the coil pair.
[0030]
The steering torque that has been detected by the torque
sensor TS is input into a controller, not illustrated. The
controller receives inputs of a vehicle speed in addition to
the steering torque, and conducts the steering assist control
to apply the steering assist force according to these inputs
to a steering system. To be specific, a steering assist
torque instruction value to generate the steering assist
23
force in an electric motor is calculated in a known procedure,
the driving electric current to be supplied to the electric
motor is feedback-controlled by the calculated steering
assist torque instruction value and the motor current
detection value. In this manner, the steering assist control
is conducted.
It is to be noted that in the above description, the input
shaft 2, the output shaft 3, and the torsion bar 4 correspond
to a rotation shaft, the coils 13a and 13b correspond to
detection coils, the yokes 15a and 15b correspond to
electromagnetic yokes. In addition, the projection portion
14a and the depression portion 15c correspond to press-fit
regulation portions.
[0031]
Thus, in one embodiment of the present invention, the
two coil bobbins 18 around which the detection coils are wound
are arranged to face each other, and interposes the yoke cover
14 between the two coil bobbins 18. By press-fitting the
yokes 15a and 15b with both of the coil bobbins 18 from both
sides in the axial direction, two detection coils
corresponding to two parts are integrated. In other words,
only one yoke cover 14 is provided for two yokes 15a and 15b,
and the number of times of press-fitting is once.
Thus, as compared to a case where one coil bobbin, one
yoke, and one yoke cover are provided, one yoke cover is
press-fit into one yoke, and then two yokes respectively
press-fit with two yoke covers are integrated together, the
number of parts corresponding to one yoke cover can be reduced,
24
and its manufacturing cost corresponding to the reduction can
be reduced. Further, as the number of times of press-fitting
the yoke cover into the yoke can be reduced, too, and thus
the assembling performance can be improved.
[0032]
Further, the press-fit regulation portion (projection
portion 14a and depression portion 15c) configured to
regulate the press-fit depth of the yoke cover 14 into the
yokes 15a and 15b is provided, so that both sides in the axial
direction of the yoke cover 14 can be press-fit into the yokes,
respectively.
Moreover, since the R portion is arranged at an end
portion in the axial direction on the outer circumferential
face of the yoke cover 14, the press-fit performance of the
yoke cover 14 into the yokes 15a and 15b can be improved.
In addition, the coil bobbin 18 is provided with two or
more regulation portions 18d and the two coil bobbins 18 are
positioned in the rotational direction by the regulation
portions 18d, so that the positioning accuracy of the coil
side terminal 18f can be improved. Furthermore, since the
guide portion 18g is arranged in the vicinity of the coil side
terminal 18f, the insertion performance into the board side
connector 19 can be improved. Thus, the connection with the
board side connector 19 can be made easily.
[0033]
Moreover, since the torque detector 10 is configured with
two coil bobbins 18 having an identical shape, the number of
the molds used for molding can be reduced. In addition, since
25
the parts (coil bobbins 18) can be commonly used, the
manufacturing cost can be reduced.
Furthermore, an inductance-type torque sensor, in a
prior art technology, is accommodated in a gearbox of the
electric power steering apparatus and the coil side terminal
is inserted and soldered into the through hole of the sensor
substrate used for signal processing, so that the coil and
the sensor substrate are electrically connected. However,
these years, as lead-free solder that does not include lead
is used, as a background of environmental load reduction,
there is a problem in that the stable quality degrades in the
electrical connection by soldering as described above.
[0034]
On the other hand, in one embodiment of the present
invention, a connector is used for electrically connecting
the coil and the sensor substrate. Thus, as compared with
the electrical connection by soldering, enhancement in the
quality stability can be achieved. In addition, since the
coil and the sensor substrate can be connected easily, the
assembling performance can be improved.
Further, since the board side connector 19 is configured
with a movable connector having a contact movable portion,
the two coils 13a and 13b can be connected more easily and
adequately.
Two or more coils (two coils in one embodiment of the
present invention) are basically used for configuring the
torque sensor TS, and there is a high possibility that a
relative positional displacement caused by an assembly error
26
occurs at the coil side terminal 18f of each coil. Thus, when
such a relative positional displacement of the coil side
terminal 18f occurs, the coil side terminal 18f cannot be
connected to the board side connector 19 and the electrical
connection may not be available adequately.
[0035]
On the other hand, in one embodiment of the present
invention, the board side connector 19 is configured such that
the terminal 19a and the housing 19c are individually movable.
Thus, each of the coil side terminals 18f can be inserted
easily. Thus, while absorbing the relative positional
displacement of the coil side terminal 18f, the coil side
terminal 18f can be fit into the board side connector 19, and
the electrical connection between the coil and the sensor
substrate is made available with certainty.
Thus, at the time of assembling the sensor, the board
(circuit board 17) on which a connector (board side connector
19) is mounted has only to be inserted into the coil (torque
detector 10). Therefore, simplification of the assembling
process and improvement of the production efficiency can be
expected. In addition, it is possible to configure a torque
detection apparatus (torque sensor TS) that can ensure the
electrical connection between the board (circuit board 17)
and the coil (torque detector 10) with certainty.
Thus, in the electric power steering apparatus on which
the torque detection apparatus is mounted, it is possible to
detect the steering torque adequately and to conduct the
steering assist control to give a steering assist force to
27
the steering system to reduce the steering burden of the
driver.
[0036]
Next, a second embodiment of the present invention will
be described below.
In the second embodiment, a movement regulation portion
configured to regulate the movement in the axial direction
of the terminal attachment portion 18e is arranged at the coil
bobbin 18.
FIG. 9 is a view illustrative of the coil bobbin 18 in
the second embodiment. Here, only the vicinities of the
terminal attachment portion 18e are illustrated.
As illustrated in FIG. 9, adjacently to the terminal
attachment portion 18e, a bobbin rib (first projection
portion) 18h, which is a part of the flange portion 18b
projecting outwardly in the radial direction, is formed. In
addition, in the terminal holder 18e, a bobbin collar (second
projection portion) 18i projecting in the circumferential
direction is formed.
As illustrated in FIG. 10, when the torque detector 10
is assembled, the bobbin ribs 18h abut the terminal attachment
portions 18e formed at the facing coil bobbins 18 from mating
face sides of the coil bobbins 18, respectively. Accordingly,
the bobbin ribs 18h are configured to regulate the movements
of the terminal attachment portions 18e formed at the facing
coil bobbins 18, in the axial direction and toward the coil
bobbins 18 side in which the bobbin ribs 18h themselves are
formed, respectively.
28
[0037]
As the two coil bobbins 18 are identical parts, and have
shapes to be line symmetry with respect to the yoke cover 14,
the bobbin ribs 18h are configured to regulate the movements
of the mating terminal attachment portions 18e, respectively.
In other words, the bobbin ribs 18h are configured to
naturally determine the terminal location accuracy with each
other in the assembling.
In addition, as illustrated in FIG. 10, when the torque
detector 10 is assembled, the bobbin collars 18i abut the
other bobbin collars 18i of the terminal attachment portions
18e formed at the facing coil bobbins 18 from opposite sides
to the mating faces of the coil bobbins 18, respectively.
Thus, the bobbin collars 18i are configured to regulate the
movements in the axial direction of the terminal attachment
portions 18e formed at the facing coil bobbins 18 and toward
sides separated from the coil bobbins 18 at which the bobbin
collars 18i themselves are formed.
[0038]
Thus, the bobbin rib 18h configured with the flange
portion 18b of the coil bobbin 18 and the bobbin collar 18i
formed as a part of the terminal attachment portion 18e
regulate each other at the axial positions of the terminal
attachment portion 18e. Thus, it is possible to ensure the
location accuracy of the coil side terminal 18f at the time
of assembling the torque detector 10.
Hence, in order to make an electrical connection with
a printed board including a torque signal processor, even when
29
the coil side terminal 18f is fit into a connector mounted
on the printed board, for example, the coil side terminal 18f
can be inserted easily and the assembling performance can be
improved.
[0039]
Next, a third embodiment of the present invention will
be described.
In the third embodiment, a movement regulation portion
configured to regulate the movement in the axial direction
of the terminal attachment portion 18e is provided without
including the guide portion 18g, whereas in the second
embodiment, the guide portion 18g is arranged at the terminal
attachment portion 18e.
FIG. 11 is a view illustrative of the coil bobbin 18 in
the third embodiment. As illustrated in FIG. 11, the
configuration is same as that of the coil bobbin 18
illustrated in FIG. 9, except that the guide portion 18g is
not arranged at the terminal attachment portion 18e.
[0040]
In other words, FIG. 12 illustrates the coil bobbin 18
in a state where the torque detector 10 is assembled. Also
in this case, the bobbin rib 18h configured with the flange
portion 18b of the coil bobbin 18 and the bobbin collar 18i
configured as a part of the terminal attachment portion 18e
regulate each other with respect to the axial position of the
terminal attachment portion 18e. Thus, it is possible to
ensure the positional accuracy of the coil side terminal 18f
when the torque detector 10 is assembled.
30
In addition, in this case, since the guide portion 18g
is not provided, when the torque detector is electrically
connected to a printed board including a torque signal
processor, a technique of inserting the coil side terminals
18f into through holes of the printed board and soldering can
be used. In this situation, since the positional accuracy
of the coil side terminal 18f is ensured, the coil side
terminals 18f can be inserted into the through holes of the
printed board easily, and an improvement in the assembling
performance can be achieved.
[0041]
Heretofore, embodiments of the present invention have
been described. However, the present invention is not
limited to them, and various changes and improvements are
applicable.
For example, a pair of coils 13a and 13b are used as coils
of the torque detector 10. However, two or more pairs of coils
may be used.
Also, in the above embodiments, the case where the
circuit board 17 is horizontally attached to the torque
detector 10 has been described. As illustrated in FIG. 13,
however, the circuit board 17 can be attached to the torque
detector 10 vertically. Thus, the choice of the layout
including the shape of the connector is enabled in the product
limitation size.
Industrial Availability
[0042]
31
According to the torque detection apparatus in one
embodiment of the present invention, as the yoke cover to be
press-fit into two yokes holding a pair of coil bobbins,
respectively, is used as a common member, the number of parts
can be reduced and it is useful. In addition, as the number
of times of press-fitting the yoke cover can be reduced, the
assembling performance can be improved and it is useful.
Then, in an electric power steering apparatus, and a
vehicle, each including the above torque detection apparatus,
the steering assist control with high reliability can be
achieved and it is useful.
Reference Signs List
[0043]
1 ... input shaft, 2 ... output shaft, 3 ... torsion bar,
5 ... housing, 5a ... input shaft side housing portion, 5b ...
output shaft side housing portion, 7 ... worm wheel, 8 ...
worm, TS ... torque sensor, 10 ... torque detector, 11 ...
sensor shaft, 12 ... cylindrical member, 13a, 13b ...
detection coil, 14 ... yoke cover, 15a, 15b ... yoke, 16 ...
coil side connector, 17 ... circuit board, 18 ... coil bobbin,
18a, 18b ... flange portion, 18c ... groove portion, 18d ...
regulation portion, 18e ... terminal attachment portion,
18f ... coil side terminal, 18g ... guide portion, 18h ...
bobbin rib, 18i ... bobbin collar, 19 ... board side connector,
19a ... terminal, 19b ... terminal movable portion, 19c ...
housing
32
CLAIMS
1. A torque detection apparatus, comprising:
a pair of detection coils configured to change impedances
in opposite directions to each other depending on torque
generated at a rotation shaft;
two coil bobbins having reel shapes around which the pair
of detection coils are wound, respectively;
two electromagnetic yokes having cylindrical portions
in which the two coil bobbins are fit and held, respectively;
and
a yoke cover configured to be press-fit into inner
diameters of the cylindrical portions of the two
electromagnetic yokes at a position interposed by the two
electromagnetic yokes facing each other in an axial
direction,
wherein the torque is detected based on output voltages
of the pair of detection coils.
2. The torque detection apparatus according to claim 1,
further comprising a press-fit regulation portion configured
to regulate a press-fit depth of the yoke cover with respect
to the two electromagnetic yokes.
3. The torque detection apparatus according to claim 2,
wherein the press-fit regulation portion is formed at
an end portion in the axial direction of each of the
cylindrical portions of the two electromagnetic yokes, and
33
is configured with a depression portion being depressed in
the axial direction and a projection portion being formed at
the yoke cover to project outwardly in a radial direction with
respect to an inner diameter of each of the two
electromagnetic yokes, and
wherein the press-fit depth of the yoke cover with
respect to each of the two electromagnetic yokes is regulated
by abutting an end face on an outer side in the axial direction
of the projection portion against a bottom portion of the
depression portion.
4. The torque detection apparatus according to any one
of claim 1 to claim 3, wherein the yoke cover comprises an
R portion at an end portion in the axial direction on an outer
circumferential face.
5. The torque detection apparatus according to any one
of claim 1 to claim 4, further comprising a regulation portion
configured to regulate a phase difference in a
circumferential direction between the two coil bobbins, on
a mating face side of each of the two coil bobbins.
6. The torque detection apparatus according to claim 5,
wherein the regulation portion is a step portion in which a
depression and a protrusion are arranged in parallel to each
other in the circumferential direction on the mating face side
of each of the two coil bobbins.
34
7. The torque detection apparatus according to any one
of claim 1 to claim 6, further comprising:
a terminal attachment portion formed at an end portion
of a side face of each of the two coil bobbins and having
terminals to which a tip portion and a termination portion
of one of the pair of detection coils are attached,
respectively; and
a movement regulation portion configured to regulate a
movement in the axial direction of the terminal attachment
portion with respect to the two coil bobbins facing each
other.
8. The torque detection apparatus according to claim 7,
wherein the movement regulation portion is configured
with a first projection portion formed by a part of a flange
portion of a first one of the two coil bobbins projecting
outwardly in the radial direction, and
wherein a movement of the terminal attachment portion
formed at a second one of the two coil bobbins in the axial
direction and toward the first one side of the two coil bobbins
is regulated by abutting the first projection portion formed
at the first one of the two coil bobbins against at least a
part of the movement regulation portion formed at the second
one of the two coil bobbins from mating face sides of the two
coil bobbins.
9. The torque detection apparatus according to claim 7
or claim 8,
35
wherein the movement regulation portion is configured
with a second projection portion formed by a part of the
terminal attachment portion projecting outwardly in the
circumferential direction, and
wherein a movement of the terminal attachment portion
formed at the second one of the two coil bobbins in the axial
direction and toward an opposite side to the first one of the
two coil bobbins is regulated by abutting the second
projection portion formed at the terminal attachment portion
formed at the first one of the two coil bobbins against at
least a part of the terminal attachment portion formed at the
second one of the two coil bobbins from an opposite side to
the mating faces of the two coil bobbins.
10. The torque detection apparatus according to any one
of claim 7 to claim 9, further comprising:
a circuit board having a torque detection function
configured to detect the output voltages of the pair of
detection coils and to detect the torque based on the output
voltages;
a board side connector mounted on the circuit board; and
a coil side connector formed at each of the two coil
bobbins, having the terminal attachment portion and the
terminals, and being electrically connectable to the board
side connector.
11. The torque detection apparatus according to claim
10, wherein the board side connector is a connector having
36
a same number of movable pieces to a number of the detection
coils.
12. The torque detection apparatus according to claim
11, wherein the board side connector has two movable pieces
corresponding to the pair of detection coils.
13. The torque detection apparatus according to any one
of claim 10 to claim 12, wherein the coil side connector
includes:
the terminals configured to stand up at the terminal
attachment portion, in an insertion direction of the coil side
connector into the board side connector; and
a plate-shaped guide portion formed at at least one side
face of the terminal attachment portion and protruding in the
insertion direction.
14. An electric power steering apparatus, comprising:
an electric motor configured to apply to a steering
system a steering assist force to reduce a steering burden
of a driver;
the torque detection apparatus according to any one of
claim 1 to claim 13 configured to detect steering torque input
into a steering mechanism; and
a motor controller configured to drive and control the
electric motor to apply the steering assist force based on
at least the steering torque detected by the torque detection
apparatus.
37
15. A vehicle comprising the electric power steering
apparatus according to claim 14.
38
ABSTRACT
TORQUE DETECTION DEVICE, ELECTRIC POWER STEERING DEVICE, AND
VEHICLE
Provided are a torque detection device capable of achieving
improved assemblability and quality, an electric power
steering device provided with said torque detection device,
and a vehicle. A torque sensor (TS) is provided with a pair
of coils (13a, 13b), two coil bobbins (18) around which the
pair of coils (13a, 13b) are respectively wound, two yokes
(15a, 15b) that respectively hold the two coil bobbins (18),
and a yoke cover (14) that is press-fitted into the inner
diameter of the yokes (15a, 15b). The yoke cover (14) is
disposed so as to be sandwiched between the two yokes (15a,
15b), which are made to face each other in the axial direction,
and is press-fitted into the inner diameter of the two yokes
(15a, 15b).