Note: Descriptions are shown in the official language in which they were submitted.
CA 02369338 2005-04-O1
ELECTRICALLY OPERATED PARFCING BRAKE APPARATUS
BACKGROUND OF THE INVENTION
1. Field of the Invention
[0001]
The present invention relates to a parking brake
apparatus for applying a brake force to wheels of a parked
vehicle. More particularly, the present invention is related
to an electrically operated parking brake apparatus for
applying the brake force to the wheels through the driving force
of an electric motor without relying upon the force applied by
the hand or foot of a driver.
2. Description of the Related Art
[0002]
JP-A-2000-309255 discloses an electrically operated
parking brake apparatus with a screw mechanism having in turn
a screw-threaded shaft adapted to be rotationally driven by an
electric motor, and a nut member adapted to mesh with the
screw-threaded shaft. When the screw-threaded shaft is rotated,
the nut member is moved along the screw-threaded shaft, whereby
a brake operating force is transmitted to wheel brakes via
cables connected to the nut member.
[0003]
When two wheel brakes are put in operation by driving two
cables with a single electrically operated parking brake
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apparatus, it is known to use an equalizer rotatably supported
at a central portion thereof by a support shaft and having
cables connected to ends thereof. In the electrically operated
parking brake apparatus disclosed in JP-A-2000-309255, the
equalizer is provided at a position which is situated away from
the screw mechanism, and the movement of the nut member of the
screw mechanism is transmitted to the equalizer via two slide
rods and a cable so that the brake operating force is uniformly
divided at the equalizer for transmission to the two wheel
brakes via two cables. Then, the two slide rods situated facing
each other across the screw-threaded shaft are connected to the
nut member such that the reaction force of the brake operating
force is not applied to the nut member and the screw-threaded
shaft as an unbalanced load.
[0004]
In the related art electrically operated parking
apparatus described above, however, since the nut member and
the equalizer are connected to each other via the two slide rods
and the cable, the construction of the parking apparatus is
complicated because the number of components is increased and
also the size of the apparatus is enlarged.
SUMMARY OF THE INVENTION
[0005
The present invention was made in view of the
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aforementioned problems in the related art, and an object of
the invention is to provide an electrically operated parking
brake apparatus which includes a smaller number of components
and hence is simple in construction and small in size, and which
can prevent an unbalanced load from being applied from the
equalizer to the screw mechanism.
[0006]
With a view to attaining this object, according to the
invention, an electrically operated parking brake apparatus,
includes:
a pair of transmission members for transmitting a brake
operating force to wheel brakes;
an electric motor;
a screw mechanism including a screw-threaded shaft
adapted to be rotationally driven by the electric motor, and
a nut member meshing with the screw-threaded shaft, the nut
member being movable along the screw-threaded shaft by the
rotation of the screw-threaded shaft;
an equalizer having connecting portions connecting the
pair of transmission members; and
a pair of support shafts disposed at positions facing
each other across the screw-threaded shaft for swingably
supporting the equalizer on said nut member,
wherein an axis of the pair of support shafts
substantially passes through a center of the screw-threaded
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shaft, and a line connecting the connecting portions of the
equalizer substantially passes through the center of the
screw-threaded shaft.
[0007]
According to the above construction, since the axis of
the pair of support shafts provided at the positions facing each
other across the screw-threaded shaft for swingably supporting
the equalizer on the nut member passes through the center of
the screw-threaded shaft, the generation of an unbalanced load
is prevented which attempts to bend the screw-threaded shaft
in a direction normal to a plane containing the axis of the pair
of support shafts. In addition, since the line connecting the
portions where the pair of transmission members are connected
to the equalizer passes through the center of the
screw-threaded shaft, the generation of an unbalanced load is
prevented which attempts to bend the screw-threaded shaft in
a direction normal to a plane containing the line connecting
the portions where the pair of transmission members are
connected to the equalizer. Thus, the increase in the number
of components and enlargement of the size of the parking brake
apparatus can be avoided, and the smooth operation of the screw
mechanism can be ensured by preventing the generation of an
unbalanced load which is applied to the screw-threaded shaft.
[ooos]
Note that Bowden cables, a ball screw mechanism,
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and an upper support shaft and a lower support shaft
described in an embodiment of the invention correspond to the
transmission members, the screw mechanism and the support
shafts of the invention, respectively.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009]
Fig. 1 is a plan view showing a vehicle provided with an
electrically operated parking brake apparatus according to the
invention;
Fig. 2 is a block diagram of a control apparatus for the
electrically operated parking brake apparatus;
Fig. 3 is a plan view, partially cut away, of the
electrically operated parking brake apparatus;
l.5 Fig. 4 is a sectional view taken along the line IV-IV in
Fig. 3;
Fig. 5 is a sectional view taken along the line V-V in
Fig. 4;
Fig. 6 is a sectional view taken along the line VI-VI in
Fig. 9;
Fig. 7 is a sectional view taken along the line VII-VII
in Fig. 6;
Fig. 8 is an operation explaining diagram which
corresponds to Fig. 4;
Fig. 9 is an operation explaining diagram which
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corresponds to Fig. 7; and
Fig. 10 is a flow chart for explaining the operation of
the electrically operated parking brake apparatus.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[oolo)
A mode for carrying out the invention will be described
below based on an embodiment of the invention illustrated in
Figs. 1 to 10.
to [0011)
As shown in Fig. 1, drum type wheel brakes 11, 11 are
provided on left and right rear wheels Wr, Wr of a vehicle, and
an electrically operated brake apparatus 12 disposed beside a
driver' s seat is connected to the wheel brakes 11, 11 via left
and right Bowden cables 13, 13. Each wheel brake 11 includes
a brake drum 14, a pair of brake shoes 15, 16, a connecting rod
17 and a lever 19. The brake shoes 15, 16 are adapted to be
brought into contact with an inner circumferential surface of
the brake drum 14. The connecting rod 17 is adapted to connect
the pair of brake shoes 15, 16. The lever 19 is rotatably
supported at one end thereof on the brake shoe 15 via a pin 18,
and the Bowden cable 13 is connected to the other end thereof .
[0012)
Consequently, when the Bowden cable 13 is pulled with an
electric motor 30 provided on the electrically operated parking
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brake apparatus 12, the lever 19 rotates about the pin 18 in
a clockwise direction of Fig. 1 so as to apply a compression
load on the connecting rod 17. Then, the brake shoe 16 is pushed
to the left as viewed in Fig. 1 by virtue of the load so as to
be pressed against the brake drum 14, whereas the brake shoe
is pushed to the right as viewed in the same figure via the
connecting rod 17 and the pin 18 to be pressed against the drum
14, whereby a brake force is generated on the wheel brakes 11.
Conversely, when the Bowden cable 13 is loosened by the electric
10 motor 30, the brake shoes 15, 16 are allowed to move away from
the brake drum 14, whereby the brake force on the wheel brakes
11 is released.
[0013]
In addition, since the electrically operated parking
15 brake apparatus 12 is disposed besides the driver's seat, the
driver can manually operate the apparatus for applying or
releasing the brake force with ease, and in case the electric
motor 30 or a control system therefor fails, the driver can
manually apply or release the brake force to or from the wheel
brakes 11 with ease. Furthermore, drastic bending of the Bowden
cables 13, 13 extending from the electrically operated parking
brake apparatus 12 to the wheel brakes 11, 11 can be prevented
to thereby reduce the transmission loss of the brake operating
force.
[0014]
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As shown in Fig. 2, an electrically operated parking
brake apparatus ECU 21 for controlling the operation of the
electrically operated parking brake apparatus 12 includes an
interface circuit 22, a main CPU 23, a fail safe CPU 24, an
electric motor driving circuit 25, an electromagnetic brake
driving circuit 26, and a lamp driving circuit 27. The
electrically operated parking brake apparatus ECU 21 is fed
from a power source 28. In addition, connected to the interface
circuit 22 are a mode selector switch 29a for selecting an
automatic or manual mode, an activating/deactivating switch
29b for activating or deactivating the operation of the
electrically operated parking brake apparatus 12 through a
switch operation when the manual mode is selected, a current
sensor 29c for detecting current flowing to the electric motor
30, a stroke sensor 29d for detecting the position of a nut
member 31 which will be described later, an inclination sensor
29e for detecting the longitudinal inclination of a road
surface on which the subj ect vehicle is parked, a longitudinal
acceleration sensor 29f for detecting the longitudinal
acceleration of the subject vehicle, a wheel speed sensor 29g
for detecting the wheel speed when the subject vehicle moves
forward or backward, a master cylinder pressure sensor 29h for
detecting the master cylinder pressure of a hydraulic brake
system, and a brake switch 29i for detecting the operation of
a brake pedal.
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(0015]
In addition, various signals such as a throttle position
signal, a shift position signal, an idle stop signal, and a
brake control signal are inputted to the interface circuit 22
of the electrically operated parking brake apparatus ECU 21
from an external ECU 32 for a fuel injection apparatus, an
automatic transmission, an anti-lock brake system and a vehicle
stability assist apparatus. The electric motor driving circuit
25 is connected to the electric motor 30, the electromagnetic
brake driving circuit 26 to an electromagnetic brake 33, which
will be described later, and the lamp driving circuit 27 to
lamps 34 such as a brake warning lamp, an in-operation lamp,
a mode indicator lamp, and stop lamps.
(0016]
Next, the construction of the electrically operated
parking brake apparatus 12 will be described with reference to
Figs. 3 to 7.
[0017]
A housing 91 constituting a main body portion of the
electrically operated parking brake apparatus 12 defines a
bottom wall 41a disposed horizontally, a front erecting wall
41b erecting from a front end of the bottom wall 41a and a rear
erecting wall 41c erecting from the bottom wall 41a at a
position in the vicinity of a rear end thereof . An upper cover
42 is fixed at front and rear ends thereof onto upper sides of
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the front erecting wall 41b and the rear erecting wall 41c with
a plurality of bolts 43, respectively. The electric motor 30
having an output shaft 30a provided so as to extend rearward
is fixed to a front face of the front erecting wall 41b of the
housing 41 with a plurality of bolts 44.
[0018]
A screw-threaded shaft 47 is supported on the front
erecting wall 41b and the rear erecting wall 41c via ball
bearings 45, 46, respectively, and the output shaft 30a of the
electric motor 30 is connected to a front end of the
screw-threaded shaft 47. The nut member 31 is brought into mesh
engagement with an outer circumference of the screw-threaded
shaft 47 via a number of balls 48, and a ball screw mechanism
49 is constituted by the screw-threaded shaft 47, the balls 48,
and the nut member 31. A collar 50 is press-fitted on an outer
circumference of the nut member 31, and vertically extending
upper and lower support shafts 51, 52 are fixed to upper and
lower surfaces of the collar 50, respectively. A guide roller
53 rotatably supported at an upper end of the upper support
shaft 51 is movably fitted in a guide groove 92a formed on a
lower surface of the upper cover 42 in a longitudinal direction.
[0019)
An equalizer 54 having an oval cross section which is
disposed to surround the outer circumference of the nut member
31 is supported by the upper support shaft 51 and the lower
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support shaft 52 in such a manner as to swing transversely. The
Bowden cables 13, 13 are each constituted by an outer tube 13a,
13a and an inner cable 13b, 13b accommodated in the outer tube
13a, 13a in such a manner as to move relative to the outer tube
13a, 13a. Front ends of the outer tubes 13a, 13a are fixed to
a back side of the rear erecting wall 41c, and front ends of
the inner cables 13b, 13b extend through the rear erecting wall
41c to be fixed to left and right end portions of the equalizer
54.
[0020]
As shown in Fig. 5, an axis L1 of the upper support shaft
51 and the lower support shaft 52 extends in a perpendicular
direction and passes through the center of the screw-threaded
shaft 47, whereas a line L2 connecting portions where the pair
of Bowden cables 13, 13 are connected to the equalizer 54
extends horizontally and passes through the center of the
screw-threaded shaft 47. In case the axis L1 is offset
transversely from the center of the screw-threaded shaft 47,
the screw-threaded shaft 47 is subjected to an unbalanced load
which bends the screw-threaded shaft 47 in a direction normal
to a plane containing the axis L1 ( i . a . , a transverse direction)
due to a load from the Bowden cable 13, 13. In addition, in
case the line L2 is offset vertically from the center of the
screw-threaded shaft 47, the screw-threaded shaft 47 is
subj ected to an unbalanced load which bends the screw-threaded
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shaft 47 in a direction normal to a plane containing the line
L2 ( i . a . , a vertical direction) due to the Load from the Bowden
cables 13, 13.
[0021]
According to the invention, however, since the axis L1
and the line L2 both pass through the center of the
screw-threaded shaft 47, the application of the unbalanced load
which attempts to bend the screw-threaded shaft 47 is prevented
so that the ball screw mechanism 49 can be operated in a smooth
fashion. Moreover, since the guide roller 53 is supported by
making use of the upper support shaft 51, the number of
components of the parking brake apparatus is decreased.
[0022]
The electromagnetic brake 33 includes a core 62, a coil
63, a rotor 65, a plate 66 and an armature 67. The core 62 is
fixed to a back side of the front erecting wall 41b with four
bolts 61. The coil 63 is accommodated in the interior of the
core 62. The rotor 65 is fixed to the front of the screw-threaded
shaft 47 with a key 64 so as to be situated on a back side of
the core 62. The plate 66 is longitudinally movably supported
with four bolts 61 and disposed between a back side of the rotor
65 and head portions 61a of the bolts 61. The armature 67 is
longitudinally movably supported with four bolts 61, and
disposed between the back side of the core 62 and a front side
of the rotor 65. A first coil spring 68 and a second coil spring
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69 are supported around an outer circumference of each of the
two vertically disposed bolts 61, 61. The first coil springs
68, disposed between recessed portions 62a in the core 62 and
the armature 67, bias the armature 67 in a direction in which
the armature 67 is brought into contact with the front side of
the rotor 65, and the second coil springs 69, disposed between
the armature 67 and the plate 66, bias the armature 67 and the
plate 66 in directions in which the armature 67 and the plate
66 move away from the front and back sides of the rotor 65. In
addition, only the first coil spring 68 is supported on an outer
circumference of each of the two horizontally disposed bolts
61, 61, and the second coil spring 69 is not supported thereon
in order to avoid the interference with an elongated hole 71a
in an arm portion 71 of a release member 70 which will be
described later.
[0023]
The biasing force of the first coil springs 68 is set to
be stronger than that of the second coil springs 69 and
consequently, when the coil 63 is de-magnetized, the rotor 65
is held between the armature 67 and the plate 66 to thereby
restrict the rotation of the screw-threaded shaft 47. In
contrast, when the coil 63 is magnetized, the armature 67 is
drawn by the core 62 against the biasing force of the first coil
springs 68, and the armature 67 and the plate 66 are caused to
move away from the rotor 65 by the biasing force of the second
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coil springs 69 so that the rotation of the screw-threaded shaft
47 is allowed.
[0024]
A release member 72 is disposed between the plate 66 and
the armature 67, and includes a transversely extending base
portion 70 and arm portions 71, 71 extending upwardly from ends
of the base portion 70 so as to be formed in a U-shape. The
two horizontally disposed bolts 61, 61 pass through elongated
holes 71a, 71a formed in the left and right arm portions 71,
71 in such a manner as to extend in vertical directions, whereby
the release member 72 is allowed to be freely guided in vertical
directions . Two upper and lower inclined surfaces 71b, 71c are
formed on a side of each arm portion 71 of the release member
72 which faces the armature 67, and two upper and lower inclined
surfaces 67a, 67b are formed on the armature 67 in such a manner
as to be brought into contact with the inclined surfaces 71b,
71c. When the release member 72 is situated at a lowered
position as illustrated in Figs . 6 and 7, the inclined surfaces
71b, 71c; 71b, 71c of the release member 72 are kept away from
the inclined surfaces 67a, 67b; 67a, 67b of the armature 67.
[0025)
A rotational shaft 75 is supported on a plane bearing 73
provided at a rear end of the bottom wall 41a of the housing
41 and a plane bearing 74 provided at a rear end of the rear
erecting wall 41c of the housing 41 in such a manner as to move
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vertically and rotate freely. A coil spring 78 is disposed
between a spring seat 77 supported at a lower portion of the
rotational shaft 75 via a ball bearing 76 and the bottom wall
41a of the housing 41. The rotational shaft 75 which is biased
upwardly by virtue of the biasing force of the coil spring 78
is stopped at a position where a driving bevel gear 79 fixed
to an upper portion of the rotational shaft 75 is brought into
contact with a lower surface of the plane bearing 74. A
hexagonal hole 75a is formed axially into an upper end of the
rotational shaft 75 so that a hexagonal wrench 80 (refer to Fig.
8) is inserted thereinto.
[0026)
A lever 82 is supported at an intermediate portion
thereof on a bracket 41d provided at a central portion of the
bottom wall 41a of the housing 41 in such a manner as to swing
vertically via the pin 81 extending transversely. A
transversely extending pin 83 is fixed to a bracket 77a provided
on an upper surface of the spring seat 77, and this pin 83 fits
in a longitudinally extending elongated hole 82a formed in the
lever 82 at a rear end thereof. A front end of the lever 82
fits in the vertically extending elongated hole 70a formed in
the base portion 70 of the release member 72.
[0027)
A follower bevel gear 84 is fixed to a rear end of the
screw-threaded shaft 47 which extends rearward through the rear
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erecting wall 41c. When the rotational shaft 75 is situated
at a raised position by virtue of the biasing force of the coil
spring 78, the driving bevel gear 79 on the rotational shaft
75 does not mesh with the follower bevel gear 84 on the
screw-threaded shaft 47, but when the rotational shaft 75 is
lowered against the biasing force of the coil spring 78, the
driving bevel gear 79 and the follower bevel gear 84 can be
brought into mesh engagement with each other.
[0028]
1.0 Next, Fig. 10 is a flowchart depicting the operation of
the electrically operated parking brake apparatus constructed
as described above according to an embodiment of the invention.
[0029]
First, in step S1, outputs from the respective sensors
15 29c to 29h are compared with their upper and lower limit values
so as to check the conditions of the sensors 29c to 29h by
confirming whether or not the outputs fall within their upper
and lower limit values, respectively. Further, the conditions
of the electric motor 30 are checked by determining whether or
20 not the electric motor 30 operates properly by allowing a
current to flow slightly to the electric motor 30. In the
following step S2, in case it is determined that the respective
sensors 29c to 29h and the electric motor 30 operate normally,
and in step S3 in case it is determined that the automatic mode
25 is selected with the mode selector switch 29a, the flow proceeds
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to step S9. In step S4, the main CPU 23 of the electrically
operated parking brake apparatus ECU 21 determines whether or
not the electrically operated parking brake apparatus needs to
be activated based on the inclination of the road surface
detected by the inclination sensor 29e, the longitudinal
acceleration detected by the longitudinal acceleration sensor
29f, the wheel speeds detected by the wheel speed sensors 29g,
the master cylinder pressure of the hydraulic brake apparatus
detected by the master cylinder pressure sensor 29h, the
operating conditions of the brake pedal detected by the brake
switch 29i and the throttle position signal, shift position
signal, idle stop signal and brake control signals inputted
from the external ECU. Then, based on the result of the
determination in step S4, in step S5 the main CPU 23 drives the
electromagnetic brake 33 and the electric motor 30 to activate
the electrically operated parking brake apparatus 12 or in step
S6, the main CPU 23 drives the electromagnetic brake 33 and the
electric motor 30 to deactivate the electrically operated
parking brake apparatus 12.
[0030]
In contrast, in case the manual mode is selected with the
mode selector switch 29a in step S3, in step S7 the conditions
of the activating/deactivating switch 29b are determined.
Based on the results of the determination in step S7, in step
S8 the electromagnetic brake 33 and the electric motor 30 are
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driven to activate the electrically operated parking brake
apparatus 12, or in step S9 the electromagnetic brake 33 and
the electric motor 30 are driven to deactivate the electrically
operated parking brake apparatus 12. In addition, in case it
is determined in step S2 that the respective sensors 29c to 29h
and the electric motor 30 are operated abnormally, in step S10
a fail safe mode is selected so that the electrically operated
parking brake apparatus 12 can be activated or deactivated
manually by the driver without involvement of the electric
motor 30.
[0031]
When the electrically operated parking brake apparatus
12 is not in operation, the nut member 31 of the ball screw
mechanism 49 is situated at a rear position indicated by chain
lines in Fig. 4, whereby the equalizer 54 supported on the nut
member 31 moves rearward and the Bowden cables 13, 13 are
loosened. Then, the coil 63 of the electromagnetic brake 33
is not demagnetized, and the rotor 65 is held between the
armature 67 and the plate 66 by virtue of the biasing force of
the first coil springs 68, whereby the screw-threaded shaft 47
which is integral with the rotor 65 is restrained from being
rotated with a certain external force in an unintended fashion.
In addition, since the rotational shaft 75 is held at an upper
first position (refer to Fig. 9) by virtue of the biasing force
of the coil spring 78, the mesh engagement between the driving
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bevel gear 79 and the follower bevel gear 84 is released, and
the release member 72 is situated at a lowered deactivated
position (refer to Fig. 7).
[0032)
When the electrically operated parking brake apparatus
ECU 21 outputs an instruction to activate the electrically
operated parking brake apparatus 12 from this state (refer to
steps S5, S8 in Fig. 10), the coil 63 of the electromagnetic
brake 33 is first magnetized so that the armature 67 is drawn
by the core 62, whereby the armature 67 and the plate 66 move
away from the rotor 65 and the screw-threaded shaft 47 is
released from the restrained conditions. At the same time as
this occurs, the electric motor 30 is driven, and the
screw-threaded shaft 47 of the ball screw mechanism 49 rotates,
so that the nut member 31 advances from the position indicated
by the chain lines to a position indicated by solid lines in
Fig. 4, whereby a tension is generated on the left and right
Bowden cables 13, 13 connected to the equalizer 54 which
advances together with the nut member 31, the left and right
wheel brakes 11, 11 being thereby activated. Then, in case the
tension on the left and right Bowden cables 13, 13 is not in
balance, the equalizer 54 swings in a direction indicated by
an arrow A-A' about the upper support shaft 51 and the lower
support shaft 52 in Fig. 3 so that the tension on the left and
right Bowden cables 13, 13 becomes uniform so as to generate
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brake forces of the same magnitude on the left and right wheel
brakes 11, 11.
[0033]
As has been described above, when the driving force of
the electric motor 30 is transmitted to the Bowden cables 13,
13 via the ball screw mechanism 49 which can transmit the
driving force in a reverse direction, the reaction force of the
brake operation force applied to the Bowden cables 13, 13 (in
other words, the tension of the Bowden cables 13, 13) acts on
the electric motor 30 as a load. Consequently, if the magnitude
of the load that is applied to the electric motor 30 and the
magnitude of the brake operating force are memorized in advance,
the magnitude of the brake operating force can be controlled
to an optional target value based on the magnitude of the load
of the electric motor 30 ( for example, the current value of the
electric motor 30 detected by the current sensor 29c).
[0034]
In addition, since the ball screw mechanism 49 has good
transmission efficiency with less friction force and looseness,
a sufficient response can be secured even if a motor which is
small in size and light in weight is utilized for the electric
motor 30, and additionally the noise can be reduced that would
be generated when in operation. Furthermore, since the ball
screw mechanism 49 is smaller in size than the reduction gear
mechanism, the overall size of the electrically operated
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parking brake apparatus 12 can be reduced.
[0035]
Thus, when the electrically operated parking brake
apparatus 12 is activated, and then a required brake force is
generated on the left and right wheel brakes 11, 11, the
electric motor 30 is stopped and the coil 63 of the
electromagnetic motor 33 is demagnetized, so that the rotor 65
is held between the armature 67 and the plate 66 by virtue of
the biasing force of the first coil springs 68, whereby the
rotation of the screw-threaded shaft 47 is restrained. This
ensures that the unintended rotation of the screw-threaded
shaft 47 is restrained to thereby prevent the brake force on
the wheel brakes 11, 11 from being released even if the tension
of the Bowden cables 13, 13 is transmitted back to the
screw-thread shaft 47 of the ball screw mechanism 49 in a
reverse fashion.
(0036]
In addition, since the electromagnetic brake 33 drives
the armature 67 to control the rotation of the screw-threaded
shaft 47 by virtue of friction force acting between the plate
66 and armature 67 and the rotor 65, the inertia force of the
electric motor 30 can be controlled accurately to thereby
control the stop position in a precise fashion when compared
to a case where a rotating preventing means such as a ratchet
mechanism is used. Moreover, since the restraint and release
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of restraint of the rotor 65 can be implemented moderately via
friction force, the operation noise can be reduced.
[0037]
Now, when the electrically operated parking brake
apparatus ECU 21 outputs an instruction to deactivate the
electrically operated.parking brake apparatus 12 (refer to
steps S6, 59 in Fig. 10), the coil 63 of the electromagnetic
brake 33 is first magnetized to release the restraint of the
screw-threaded shaft 47, and in this state the electrically
operated parking apparatus ECU 21 drives the electric motor 30
in a direction opposite to the direction described previously
so as to rotate the screw-threaded shaft 47 of the ball screw
mechanism 49 in a reverse direction, whereby the nut member 31
is withdrawn from the position indicated by the solid lines in
Fig. 4 to the position indicated by the chain lines so as to
deactivate the left and right wheel brakes 11, 11.
[0038]
Tn case the electric motor 30 or the control system
thereof fails while the electrically operated parking brake
apparatus 12 is generating the brake force on the wheel brakes
11, 11, the driver may manually deactivate the parking brake
apparatus (refer to step S10 in Fig. 10) . Due to this, as shown
in Fig. 8, when the hexagonal wrench 80 is inserted into the
hexagonal hole 75a in the rotational shaft 75 so as to press
down the rotational shaft 75 to a second position against the
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biasing force of the coil spring 78, the driving bevel gear 79
of the rotational shaft 75 is brought into mesh engagement with
the follower bevel gear 84 of the screw-threaded shaft 47.
[0039]
Further, since the rear end of the lever 82 supported by
the pin 81 at the central portion thereof is pushed down with
the front end thereof being pushed up, the release member 72
connected to the front end thereof is raised between the plate
66 and the armature 67. As a result, as shown in Fig. 9, since
the inclined surfaces 71b, 71b; 71c, 71c provided on the release
member 72 ride on the inclined surfaces 67a, 67a; 67b, 67b
provided on the armature 67, the plate 66 and the armature 67
move away from the rotor 65 against the biasing force of the
first coil spring 68, whereby the electromagnetic brake 33 can
be released manually without magnetizing the coil 63.
[0040)
Consequently, the screw-threaded shaft 97 can be rotated
via the driving bevel gear 79 and the follower bevel gear 84
which are in mesh engagement by rotating the rotational shaft
75 with the hexagonal wrench 80 from this sate, whereby the nut
member 31 can be moved from a position indicated by solid lines
in Fig. 8 to a position indicated by chain lines. Thus, the
Bowden cables 13, 13 can be loosened to deactivate the wheel
brakes 11, 11.
[0041)
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Of course, in case the activation of the electrically
' operated parking brake apparatus 12 by the electric motor 30
becomes impossible due to a failure, as has been described above,
the electrically operated parking brake apparatus 12 can be
activated through the manual operation with the hexagonal
wrench 80. In this case, the hexagonal wrench 80 is rotated
in a direction opposite to the direction described previously
so that the nut member 31 is moved from the position indicated
by the chain lines in Fig. 8 to the position indicated by the
solid lines.
[0042]
Thus, when the electric motor 30 or the control system
thereof fails, the electric operated parking brake apparatus
12 can manually be activated or deactivated through a simple
operation in which the hexagonal wrench 80 is inserted into the
hexagonal hole 75a of the rotational shaft 75 so as to rotate
the rotational shaft 75 while pushing down the same, whereby
the conveniences can be improved remarkably.
[0043j
While the embodiment of the invention has been described
in detail heretofore, the invention may be modified in design
in various ways without departing from the sprit and scope
thereof.
[0044]
For example, while the electrically operated parking
24
CA 02369338 2005-04-O1
brake apparatus 12 and the wheel brakes 11, 11 are connected
to each other with the Bowden cables 13, 13 in the embodiment,
in addition to the Bowden cables 13, 13, rods, links or arms
may be used solely or in combination to form the transmission
member. Alternatively, rods, links or arms may be used in
combination with the Bowden cables 13, 13 to form the
transmission member.
[0045]
In addition, while the ball screw mechanism 49 is used
as the screw mechanism in the embodiment, any screw mechanism
other than the ball screw mechanism may be used.
[0046]
Furthermore, while in the embodiment the axis L1 of the
upper support shaft 51 and the lower support shaft 52 for
supporting the equalizer 54 on the nut member 31 in the swinging
fashion is disposed in the perpendicular direction and the line
L2 connecting the portions where the pair of Bowden cables 13,
13 are connected to the equalizer 54 is disposed in the
horizontal direction, the positional relationship of the axes
L1 and L2 may be changed such that the positions are
interchanged.
[0047]
As has been described above, according to the invention,
since the axis of the pair of support shafts provided at the
positions facing each other across the screw-threaded shaft for
CA 02369338 2005-04-O1
supporting the equalizer on the nut member in the swinging
fashion passes through the center of the screw-threaded shaft,
the generation of an unbalanced load is prevented which
attempts to bend the screw-threaded shaft in a direction normal
to a plane containing the axis of the pair of support shafts .
In addition, since the line connecting the portions where the
pair of transmission members are connected to the equalizer
passes through the center of the screw-threaded shaft, the
generation of an unbalanced load is prevented which attempts
to bend the screw-threaded shaft in a direction normal to a
plane containing the line connecting the portions where the
pair of transmission members are connected to the equalizer.
Thus, the increase in the number of components and enlargement
of the size of the parking brake apparatus 12 can be avoided,
and smooth operation of the screw mechanism can be assured by
preventing the generation of an unbalanced load which is
applied to the screw-threaded shaft.
26
